Carbapenemase-producing Pseudomonas aeruginosa -an emerging challenge

Gene expressions of clinical Pseudomonas aeruginosa harboring RND efflux pumps on chromosome and involving a novel integron on a plasmid

The clinical strain of Pseudomonas aeruginosa XM8 harbored multiple RND-type antibiotic efflux pump genes and a novel integron In4881 on its plasmid pXM8-2, rendering it resistant to nearly all conventional antibiotics except colistin. The resistance was primarily attributed to the inactivation of the oprD gene and overexpression of several efflux pump genes, including mexAB-oprM, mexCD-oprJ, oprN-mexFE, and mexXY. In this study, the XM8 strain was comprehensively characterized using various methods. Antimicrobial susceptibility testing was performed using the BioMerieux VITEK2 system and manual double dilution methods. Gene expression levels of efflux pump-related genes were analyzed via quantitative real-time PCR. The bacterial chromosome and plasmid were sequenced using both Illumina and Nanopore platforms, and bioinformatics tools were employed to analyze mobile genetic elements associated with antibiotic resistance. The pXM8-2 plasmid containsed multiple mobile genetic elements, including integrons (In4881, In334, In413) and transposons (Tn3, TnAs1, TnAs3). Notably, In4881 was reported for the first time in this study. The presence of these elements highlights the potential for horizontal gene transfer and further spread of antibiotic resistance. Given the strong resistance profile of the XM8 strain, effective measures should be implemented to prevent the dissemination and prevalence of such multidrug-resistant bacteria.

The evolution of carbapenem-resistant Pseudomonas aeruginosa in the COVID-19 era: A global perspective and regional insights

OBJECTIVE

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a major contributor to healthcare-associated infections globally. The aim of this study was the impact of the COVID-19 pandemic on the genomic characteristics of P. aeruginosa, particularly clinical CRPA isolates.

METHODS

Clinical data of each patient were collected from the clinical and medical record system. Whole-genome sequencing and bioinformatics analyses were performed to characterize the antibiotic resistance genes (ARGs) and evolutionary dynamics of these isolates. Furthermore, big data analysis was employed to elucidate the genomic characteristics of P. aeruginosa genomes across different periods on a global scale. Statistical analyses were applied to ensure the reliability of the findings.

RESULTS

A total of 628 non-duplicate CRPA isolates were collected, with 256 isolates from before the COVID-19 pandemic and 372 during the pandemic. Only 26.59% of isolates carried carbapenemases, predominantly GES-14, and carbapenemase diversity decreased during the pandemic. However, the diversity of CRPA sequence types (STs) increased, with ST235 and ST244 emerging as the most prevalent clones. The Antibiotic resistance genes (ARGs) number carried by CRPA isolates significantly decreased during the pandemic (P < 0.05), with notable differences in 24 ARGs and 14 virulence factors (VFs) between prepandemic and pandemic periods (χ2 test, P < 0.05). O11 was the predominant serotype across all periods. Global analysis revealed a significant reduction in ARGs in strains from China and Australia (P < 0.01) during the pandemic. Analysis of the global epidemic clones ST244 and ST235 indicated that ARGs in ST244 P. aeruginosa increased significantly during the pandemic.

CONCLUSIONS

Our study highlights the critical need for ongoing surveillance of the evolutionary effects of the COVID-19 pandemic on clinical CRPA isolates, offering an essential theoretical basis for the development of effective and rational control strategies in clinical settings.

Loss of OprD function is sufficient for carbapenem-resistance-only but insufficient for multidrug resistance in Pseudomonas aeruginosa

BACKGROUND

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) constitutes a serious source of global healthcare-associated infections, and the exploration of its resistance mechanism represents an important approach to address this issue. Because current research on antibiotic resistance predominantly focuses on multidrug-resistant P. aeruginosa which is widely isolated clinically and the resistance mechanism is complicated. CRPA generally has a higher tolerance to other antibiotics than carbapenem-sensitive P. aeruginosa, yet the specific mechanism of resistance remains poorly understood.

RESULTS

This study delves into the specific antibiotic resistance mechanisms of carbapenem-resistance-only P. aeruginosa (CROPA), a rare kind of pathogen that shows resistance exclusively to carbapenem antibiotics. We collected 11 clinical isolates of CROPA, performed genome sequencing. Our analysis revealed numerous amino acid mutations and premature termination of OprD expression in the CROPA strains. The insertion of IS256 element into OprD in P. aeruginosa was a novel finding. Validation via qPCR and SDS-PAGE affirmed diminished OprD expression levels. Interestingly, common carbapenemases were not detected in our study, and there was no observed upregulation of relevant efflux pumps. The expression of wild-type OprD in CROPA strains restored the sensitivity to carbapenem antibiotics.

CONCLUSIONS

Compared with previous studies on MDR-CRPA, the emergence of CROPA may be directly linked to changes in OprD, while other resistance mechanisms could contribute to broader antibiotic resistance profiles. By focusing on the antibiotic resistance mechanisms of CROPA, this study illuminates the relationship between specific antibiotic resistance mechanisms and antibiotic resistance, providing a theoretical foundation for guiding clinical treatment and developing novel anti-infective agents.

Intestinal bacteria aerosols from hospital and municipal wastewater treatment: Seasonal variations, dispersal characteristics and toxic effects

Wastewater contains a rich abundance of intestinal pathogens, which can be released into the air during the wastewater treatment process, posing hazards to occupational workers and surrounding residents. Hospital wastewater contains a higher concentration of pathogens compared to urban wastewater, potentially causing greater harm to human health. In this study, a one-year collection of bioaerosols was conducted at a hospital sewage station (HSS) and a municipal sewage plant (MSP) to investigate the characteristics of intestinal bacteria in bioaerosols from different wastewater sources. The concentration of intestinal bacteria in the biological tank air at HSS ranged from 16 to 42 CFU/m3, while at MSP, the concentration range was from 19 to 30 CFU/m3. The airborne bacterial concentration was highest during the summer season. The average proportions of fine particles (<2.5 μm) in the air of HSS and MSP were 45.48% and 41.59%, respectively. The predominant intestinal bacteria detected in HSS bioaerosols were uncultured_bacterium_f_Enterobacteriaceae, Pantoea, and Serratia. The primary intestinal bacteria in MSP bioaerosols were Brevundimonas, Pseudomonas, and Enterobacteriaceae. Bioaerosols can rapidly diffuse into the surrounding environment. After 1 h of diffusion, the average diffusion areas of bioaerosols from HSS and MSP were 131.79 km2 and 159.01 km2, respectively. Exposure to bioaerosols generated from hospital wastewater can cause damage to the respiratory system of mice. The biological components in the bioaerosols can lead to significant increases in the expression levels of IL-6 and TNF-α in the serum of mice, as well as marked pathological changes in the lungs. This study reveals the potential health hazards of inhaling bioaerosols generated from wastewater and provides a scientific basis for formulating management measures for bioaerosols.

Increased rates of blaNDM in Pseudomonas aeruginosa in a tertiary care hospital in southern Brazil

Carbapenem-Resistant Pseudomonas Aeruginosa (CRPA) is considered as one of the high priority pathogens by the World Health Organization. As CRPA carbapenemase producers have increased worldwide, the aim of this study was to evaluate the carbapenemase prevalence in CRPA at a tertiary care hospital in Brazil". All 395 CRPA identified in the period of September 2021 to May 2024 were evaluated by multiplex real-time polymerase chain reaction (qPCR-HRM) for the following carbapenemase genes: blaKPC, blaNDM, blaOXA-48-like, blaIMP, blaVIM,blaSPM and blaGES. In the first period analyzed (September to December 2021), almost 70 % of the isolates were negative for the 7 tested genes, and the blaNDM was found in 27.3 % of the CRPA. In the following semesters there was an increase of blaNDM as follows: January to June of 2022 = 29.8 %; July to December of 2022 = 43.8 %; January to June of 2023 = 42.4 %; July to December 2023 = 58.9 % and January to May of 2024 = 59.5 % of blaNDM. The prevalence of the other carbapenemases remained low. These results indicated an important increase of the blaNDM gene, overcoming the CRPA non-carbapenemase producers in our institution.

In vivo divergent evolution of cross-resistance to new β-lactam/β-lactamase inhibitor combinations in Pseudomonas aeruginosa following ceftazidime/avibactam treatment

PURPOSE

To describe and characterize the evolutionary process of cross-resistance to ceftazidime/avibactam, ceftolozane/tazobactam and imipenem/relebactam of a carbapenem-resistant Pseudomonas aeruginosa (CRPA) lineage isolated from a patient receiving two courses of ceftazidime/avibactam treatment.

METHODS

The minimum inhibitory concentrations (MICs) of strains were determined by broth microdilution methods. The mutant genes were identified by the whole genome sequencing results. Cloning, knockout and complementation experiments were used to evaluate the impact of the resistance relative genes on the MICs. Reverse transcription-quantitative PCR was used to evaluate the relative expression of ampC and mexA. The fitness cost was measured by growth curve tests.

RESULTS

A total of 24 CRPA strains were isolated encompassing the whole ceftazidime/avibactam treatment. The CRPA strains developed high-level resistance to ceftazidime/avibactam and cross-resistance to ceftolozane/tazobactam or imipenem/relebactam, clustering into clade A and clade B, respectively. In both clades, the overexpression of AmpC was crucial to ceftazidime/avibactam resistance, which was driven by AmpD deficiency in clade A and dacB mutation in clade B, respectively. In clade A, mraY mutation and a new allele of AmpC (blaPDC-575) elevated resistance to ceftazidime/avibactam, with blaPDC-575 also conferring resistance to ceftolozane/tazobactam. In clade B, mexB mutation was associated with the resistance to both ceftazidime/avibactam and imipenem/relebactam. Moreover, the fitness costs of P. aeruginosa strains typically increased with the higher MICs of ceftazidime/avibactam.

CONCLUSION

Divergent resistance evolution resulted in a complex phenotype in the CRPA lineage, posing significant challenge to clinical treatment. The resistance surveillance needs to be prioritized, and new therapeutic strategies are urgently required.

Analysis of intrahospital and global dissemination and resistome dynamics of NDM-1-producing ST773 Pseudomonas aeruginosa high-risk clone

Objectives

To analyse the intrahospital and global dissemination and resistome dynamics of the concerning NDM-1 MBL-producing ST773 P. aeruginosa high-risk clone.

Methods

A total of 17 NDM-1-producing P. aeruginosa isolates recovered in 2022-24 from 10 patients at Hospital Clinic of Barcelona (HCB), Spain, were studied through susceptibility testing and WGS. Expression of resistance genes was analysed through quantitative (real-time) RT-PCR. Forty ST773 genomes from isolates recovered worldwide were also incorporated in the phylogenetic and resistome analysis.

Results

All HCB NDM-1-producing isolates were assigned to ST773 except one (ST357 additionally producing VEB-9 and linked epidemiologically to India). The index ST773 case was a 41-year-old woman admitted to the oncology ward in February 2022 after breast cancer surgery in Ukraine. These isolates were closely related and the bla NDM-1 gene was located in the same 117 kb integrative conjugative element. All ST773-NDM-1 producers from HCB and the 40 worldwide isolates shared the same acquired resistance determinants [aadA11-like, rmtB4, qnrVC1 and tet(G)], as well as some of the antibiotic resistance mutations (mexZ, mexT, gyrA and parC). Other specific mutations such as an oprD deletion were shared only with isolates from Ukrainian patients transferred to Madrid or the Netherlands. Lastly, HCB isolates evolved further resistome mutations during intrahospital dissemination, including regulators of AmpC (mpl) and MexAB-OprM (nalD), linked to the acquisition of aztreonam/avibactam resistance, and thus remaining only susceptible to cefiderocol and colistin.

Conclusions

This work evidences the transborder spread and intrahospital dissemination and evolution of the emerging ST773-NDM-1 P. aeruginosa high-risk clone.

Designing a multi-epitope vaccine against Pseudomonas aeruginosa via integrating reverse vaccinology with immunoinformatics approaches

Pseudomonas aeruginosa is a typically opportunistic pathogen responsible for a wide range of nosocomial infections. In this study, we designed two multi-epitope vaccines targeting P. aeruginosa proteins, incorporating cytotoxic T lymphocyte (CTL), helper T lymphocyte (HTL), and linear B lymphocyte (LBL) epitopes identified using reverse vaccinology and immunoinformatics approaches. The vaccines exhibited favorable physicochemical properties, including stability, solubility, and optimal molecular weight, suggesting their potential as viable candidates for vaccine development. Molecular docking studies revealed strong binding affinity to Toll-like receptors 1 (TLR1) and 2 (TLR2). Furthermore, molecular dynamics simulations confirmed the stability of the vaccine-TLR complexes over time. Immune simulation analyses indicated that the vaccines could induce robust humoral and cellular immune responses, providing a promising new approach for combating P. aeruginosa infections, particularly in the face of increasing antibiotic resistance.

Unveiling the impact: COVID-19's influence on bacterial resistance in the Kingdom of Bahrain

BACKGROUND

Antibiotic resistance is a growing global health threat, and understanding local trends in bacterial isolates and their susceptibility patterns is crucial for effective infection control and antimicrobial stewardship. The coronavirus disease 2019 (COVID-19) pandemic has introduced additional complexities, potentially influencing these patterns.

AIM

To analyze trends in bacterial isolates and their antibiotic susceptibility patterns at Salmaniya Medical Complex from 2018 to 2023, with a specific focus on the impact of the COVID-19 pandemic on these trends.

METHODS

A retrospective analysis of microbiological data was conducted, covering the period from 2018 to 2023. The study included key bacterial pathogens such as Escherichia coli (E. coli), Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus, among others. The antibiotic susceptibility profiles of these isolates were assessed using standard laboratory methods. To contextualize the findings, the findings were compared with similar studies from other regions, including China, India, Romania, Saudi Arabia, the United Arab Emirates, Malaysia, and United States.

RESULTS

The study revealed fluctuating trends in the prevalence of bacterial isolates, with notable changes during the COVID-19 pandemic. For example, a significant increase in the prevalence of Staphylococcus aureus was observed during the pandemic years, while the prevalence of E. coli showed a more variable pattern. Antibiotic resistance rates varied among the different pathogens, with a concerning rise in resistance to commonly used antibiotics, particularly among Klebsiella pneumoniae and E. coli. Additionally, the study identified an alarming increase in the prevalence of multidrug-resistant (MDR) strains, especially within Klebsiella pneumoniae and E. coli isolates. The impact of the COVID-19 pandemic on these trends was evident, with shifts in the frequency, resistance patterns, and the emergence of MDR bacteria among several key pathogens.

CONCLUSION

This study highlights the dynamic nature of bacterial isolates and their antibiotic susceptibility patterns at Salmaniya Medical Complex, particularly in the context of the COVID-19 pandemic. The findings underscore the need for continuous monitoring and effective anti-microbial stewardship programs to combat the evolving threat of antibiotic resistance. Further research and policy initiatives are required to address the identified challenges and improve patient outcomes in the face of these ongoing challenges.

Pseudomonas aeruginosa enhances anti-PD-1 efficacy in colorectal cancer by activating cytotoxic CD8+ T cells

Background

Immune checkpoint therapy for colorectal cancer (CRC) has been found to be unsatisfactory for clinical treatment. Fecal microbiota transplantation (FMT) has been shown to remodel the intestinal flora, which may improve the therapeutic effect of αPD-1. Further exploration of key genera that can sensitize cells to αPD-1 for CRC treatment and preliminary exploration of immunological mechanisms may provide effective guidance for the clinical treatment of CRC.

Methods

In this study, 16S rRNA gene sequencing was analyzed in the fecal flora of both responders and no-responders to αPD-1 treatment, and the therapeutic effect was experimentally verified.

Results

Pseudomonas aeruginosa was found to be highly abundant in the fecal flora of treated mice, and Pseudomonas aeruginosa mannose-sensitive hemagglutinin (PA-MSHA) in combination with αPD-1 was effective in the treatment of CRC through the induction of CD8+ T-cell immunological effects.

Conclusion

The clinical drug PA-MSHA can be used in combination with αPD-1 for the treatment of CRC as a potential clinical therapeutic option.

Antimicrobial activity of new anti-Pseudomonas beta-lactam-beta-lactamase inhibitors against Pseudomonas aeruginosa respiratory isolates recovered during the study for Monitoring Antimicrobial Resistance Trends (SMART) program in France (2016-2022)

OBJECTIVES

To assess the susceptibility of ceftolozane/tazobactam (C/T) and comparators to Pseudomonas aeruginosa isolates recovered from respiratory-tract-infections (RTI) between 2016-2022 in the French SMART study.

METHODS

Antibiotic susceptibility testing and minimum inhibitory concentrations (MICs) of 717 P.aeruginosa isolates collected in five French hospitals were determined and interpreted according to the EUCAST-2022 guidelines. P. aeruginosa isolates resistant (R) to imipenem and/or C/T were screened by PCR for extended-spectrum-β-lactamases (ESBLs), AmpC and carbapenemase genes. The identified genes were sequenced and the variants determined.

RESULTS

All in all, 96.5 % of P. aeruginosa isolates were susceptible to C/T, comparable to the susceptibilities of meropenem-vaborbactam (MVB = 96.5 %), imipenem/relebactam (IMI/REL = 96.9 %) and ceftazidime-avibactam (C/A = 97.0 %). MIC50 and MIC90 for C/T were 0.5 and 2 mg/L respectively against the 717 isolates. Among the 242 isolates (33.7 %) resistant to at least one anti-Pseudomonas β-lactam, close to 90 % were susceptible to C/T, C/A, MVB and IMI/REL. Among the 80 isolates resistant to piperacillin-tazobactam, cefepime and ceftazidime, 76.3 % were susceptible to C/T and only IMI/REL and amikacin reached susceptibility exceeding 80 %. Among the 32 isolates resistant to imipenem and meropenem, susceptibility exceeding 60 % was observed only for IMI/REL, C/T, and C/A. For these strains, the MIC50 of C/T was 2 mg/L, while that of C/A was at the resistance threshold (8 mg/L). IMI/REL had the strongest activity (72 %) against the 25 isolates resistant to C/T. Lastly, 53 imipenem and/or C/T-R isolates harbored a class C β-lactam (blaPDC) variant, and one of them also carried the blaPER-1 gene and another, the blaVIM-2 gene.

CONCLUSION

C/T is a reliable treatment option in RTI caused by P. aeruginosa.

Genetic Diversity in Antimicrobial Resistance Determinants Among Pathogenic Pseudomonas aeruginosa in India

The drastic rise in antibiotic resistance has become a global challenge, including India, due to high morbidity. The delayed identification and lack of treatment are the major causes of death. However, there is a shortage of precise information on the specific resistance pattern and sequence types of Pseudomonas aeruginosa from India that can help in diagnostics and therapy. A total of 16 clinical isolates were collected from the western region of India, along with 181 P. aeruginosa genomes of India from public database were retrieved and thoroughly analysed for antibiotics resistance determinants for associated sequence types and O-serotypes using different bioinformatics tools. Of all collected isolates (n = 16), 9 were extensively drug-resistant (XDR), 6 were multidrug-resistant (MDR), and only 1 isolate was susceptible to selected antibiotics. ST357 (n = 23; 11.6%) was the most frequent, followed by ST308, and ST1203. In serotyping, O11 (n = 85; 43%) was most prevalent. A novel ST4937 was reported and submitted to PubMLST. blaNDM-1 carbapenemase was found in (n = 45; 22.8%) isolates, whereas class D blaOXA-488 was present in (n = 38; 19.2%) isolates, further, several variants were found for class C blaPDC genes, where blaPDC-3 and blaPDC-19a were found to be predominant. We discovered that the amounts of carbapenemases and extended spectrum beta-lactamases (ESBL) genes were lower in India. This can be a relief sometimes, but a rise in high-risk clones could lead to longer hospital stays and more deaths. Therefore, ongoing surveillance of these strains is essential for effective infection management and containment of their spread.

Virulence factors, molecular characteristics, and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa isolated from pediatric patients in Shanghai, China

BACKGROUND

The investigation into virulence factors, clinical and molecular characteristics, and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa (CRPA) in pediatric populations is currently inadequate.

PURPOSE

This study aimed to investigate the virulence factors, clinical and molecular characteristics, and resistance mechanisms of 135 CRPA isolates in Shanghai, China.

METHODS

Analysis of virulence-associated genes and multilocus sequence typing (MLST) provided epidemiological and molecular insights into the isolates. Resistance mechanisms were identified via PCR, sequencing, and qRT-PCR.

RESULTS

The predominant resistance mechanism to carbapenems was the decreased production of outer membrane porin OprD (75.6%), accompanied by mutational inactivation of the oprD (87.4%). However, elevated production of AmpC (7.4%) and mexB overexpression (5.2%) were uncommon. Thirty-five sequence types (STs) were identified, with clonal complex 244 (CC244;59.3%) representing the majority of infections. Sixteen virulence factor genes were detected, with a significant portion of isolates (40.7%) concurrently possessing Toxin A (toxA), Elastase B (lasB), Exoenzyme S (exoS), staphylolysin (lasA), and Pilin (pilA). Almost all CC244 isolates carried toxA (100%), exoS (100%), pilA (100%), lasB (98.6%), and lasA (82.5%) while all ST2100, ST274, ST1129, ST446, and ST2069 isolates contained exoY. CC244 + isolates exhibited significantly increased antibiotic resistance, and the isolates from diseased or discharged patients showed comparatively higher resistance than others, except against gentamicin. Most patients (71.9%) received combination therapy, with 65.2% achieving clinical cure or improvement.

CONCLUSION

This study predominantly identified OprD-mediated carbapenem resistance in pediatric patients. The CRPA isolates were characterized by a variety of STs and a widespread distribution of virulence-associated genes. CC244 demonstrated significantly higher resistance, with potential outbreaks occurring in 2018 and 2019. These findings could aid in managing nosocomial CRPA infections and enhancing clinical practices.

Investigating the validity of mCIM and sCIM phenotypic methods in screening Pseudomonas aeruginosa isolates producing IMP, VIM, and NDM metallo-beta-lactamases isolated from burn wounds

Metallo-beta-lactamase-producing Pseudomonas aeruginosa (P. aeruginosa) is a major pathogen in burn wounds, often exhibiting high levels of antibiotic resistance, which complicates treatment strategies. This study deals with the validity of the modified Carbapenem Inactivation Method (mCIM) and the simplified Carbapenem Inactivation Method (sCIM) phenotypic tests for screening metallo-beta-lactamase (MBL) production by P. aeruginosa isolates from a referral burn center in Iran. Forty isolates were obtained between January and June 2021 and identified using conventional biochemical methods. Antimicrobial susceptibility testing was conducted following Clinical and Laboratory Standards Institute (CLSI) 2021 guidelines. mCIM based on CLSI 2023 guidelines was used to detect carbapenemase production. sCIM was also used based on previously developed protocols. PCR was performed to detect blaIMP, blaVIM, and blaNDM genes. The results were analyzed using SPSS and MedCalc. We observed a 90% resistance rate to imipenem and high resistance to other antibiotics, with multidrug-resistant (MDR) strains constituting 95% of the isolates. The mCIM test demonstrated high sensitivity (87.50%) and high negative predictive value (89.47%) and moderate specificity (70.83%) and moderate positive predictive value (66.67%) for detecting MBLs. In contrast, the sCIM test was unreliable, indicating a need for more standardized testing protocols. This study underscores the importance of accurate and timely detection of carbapenemase production to guide effective treatment.

In Vitro and In Vivo Evaluation of the De Novo Designed Antimicrobial Peptide P6.2 Against a KPC-Producing P. aeruginosa Clinical Isolate

The antimicrobial peptide P6.2 was previously de novo designed as an alpha helix cationic amphipathic molecule. In previous work, we have shown that this peptide displayed significant antimicrobial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria. However, while P6.2 lacked biofilm-inhibiting properties against the P. aeruginosa strain PA01, it displayed anti-inflammatory effects in a murine acute lung infection model challenged with this pathogen. In this work, the peptide P6.2 antimicrobial activity and its possible synergy with meropenem were evaluated both in vitro and in vivo using a Galleria mellonella infection model against a carbapenem-resistant KPC-producing clinical isolate of P. aeruginosa. Firstly, the cytotoxic effect of the peptide on A549 and RAW264.7 cell lines was assayed, showing no cytotoxicity at 64 µg/mL and below. Then, the MIC (minimal inhibitory concentration) and bactericidal effect against the carbapenemase-producing strain P. aeruginosa M13513 strain were determined. P6.2 showed a MIC between 32 and 64 µg/mL, and a rapid bactericidal activity against this strain (less than 45 min). The peptide stability at different temperatures and in bovine serum at 37 °C was also analyzed, showing good stability and almost no degradation after 15 min of incubation at 100 °C or 24 h at 37 °C in serum, respectively. The antibiofilm activity was also evaluated, and although the peptide did not show biofilm inhibitory activity, it did demonstrate biofilm disruptive activity, together with bactericidal activity inside the pre-formed biofilm. The possible synergistic effect with the carbapenem meropenem was then analyzed in vitro by killing kinetics, revealing a synergistic interaction between P6.2 and the antibiotic against this strain. Finally, P6.2 was evaluated in vivo in the Galleria mellonella larvae infection model. Interestingly, in G. mellonella, P6.2 alone did not completely clear the infection caused by P. aeruginosa M13513. However, when combined with meropenem, P6.2 demonstrated a synergistic effect, leading to increased survival rates in infected larvae. The results presented here highlight the potential that this peptide displays when used in combination with carbapenems against a clinically relevant KPC-producing P. aeruginosa.

High prevalence of carbapenem-resistant Pseudomonas aeruginosa and identification of a novel VIM-type metallo-β-lactamase, VIM-92, in clinical isolates from northern China

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) has become a serious global health concern due to the limited treatment options. The primary resistance mechanism in CRPA involves the production of metallo-β-lactamases (MBLs), making MBL-producing P. aeruginosa a significant component of CRPA cases. To understand the prevalence of CRPA in hospitals in northern China, we conducted a preliminary screening and identification of CRPA in 143 clinical isolates of P. aeruginosa collected from various departments of a tertiary hospital between 2021 and 2023, analyzing CRPA resistance trends in certain regions of northern China during this period. We identified 71 CRPA isolates that exhibited high carbapenem resistance and phylogenetic tree analysis revealed that ST244 CRPA isolates had widely spread across various departments of the same hospital over three consecutive years. We also identified two VIM-producing isolates, PJK40 and PJK43, both of which carried the same novel VIM-type metallo-β-lactamase, VIM-92, encoded by a newly identified gene, bla VIM-92, closely related to bla VIM-24. bla VIM-92 was embedded in class 1 integrons within the Tn1403 transposon. The bla VIM-92-carrying plasmid, pPJK40, was found to resemble the pJB37 megaplasmid. The expression of VIM-92 and VIM-24 in DH5α and PAO1 revealed similar effects of the MICs of β-lactams, except for aztreonam. The high prevalence of CRPA in clinical settings, and the identification of VIM-92, highlights the urgent need for ongoing surveillance of CRPA and emerging MBL variants in P. aeruginosa.

Outbreak investigations of contact patients and the hospital environment after detection of carbapenemase-producing Pseudomonas aeruginosa on general hospital wards

BACKGROUND

Carbapenemase-producing Pseudomonas aeruginosa (CPPA) is known to cause outbreaks in healthcare settings. Outbreak investigations, including screening of contact patients and the environment, are key in infection prevention and control (IPC) management to contain them.

AIM

The aim of this study was to determine the yield of outbreak investigations performed after unexpected detections of CPPA in clinical or screening cultures of patients hospitalized on a general ward.

METHODS

In this retrospective cohort study, we included all adult patients newly detected with CPPA ('index patients') while hospitalized on a general ward from June 2011 to December 2021. We evaluated the outbreak investigations performed, i.e., screening of epidemiologically linked patients ('contact patients') and the environment. Isolates were analysed by whole-genome sequencing (WGS).

FINDINGS

Outbreak investigations of 34 of 38 (89.5%) index patients were evaluated, with screening of contact patients performed in 34 (100%) and the environment in 18 (52.9%). CPPA was detected in eight (44.4%) of the environmental screenings, and WGS confirmed relatedness to the index in four (22.2%). A total of 1707 of 1982 (86.1%) identified contact patients were screened, of which eight carried CPPA (0.5%). WGS confirmed transmission from index patient to contact patient in five of these (0.3%).

CONCLUSION

Environmental screening should be part of outbreak investigations for CPPA, as it identifies sources which enables timely installation of targeted IPC measures. Identification of index-to-contact patient transmission was rare in our setting, thus implying reconsideration of the definition of contact patients at high risk is needed.

In vitro activity of aztreonam in combination with relebactam against gram-negative pathogens producing various serine and metallo-β-lactamases

OBJECTIVES

Infections caused by carbapenemase-producing Gram-negative pathogens have become a significant global public health challenge due to limited treatment options. Pathogens producing metallo-β-lactamase are particularly problematic since they are not inhibited by conventional β-lactamase inhibitors. Herein, we assess the in vitro activity of aztreonam in combination with relebactam against a collection carbapenemase producing organisms, including strains producing both serine‑β-lactamase and IMP-type metallo-β-lactamase that are commonly encountered in Japan.

METHODS

A total of 119 carbapenemase-producing clinical isolates were used in this study. Minimum inhibitory concentrations (MICs) of aztreonam and imipenem alone and aztreonam/relebactam, aztreonam/avibactam and imipenem/relebactam combinations were determined by the broth microdilution method.

RESULTS

Aztreonam MICs were reduced in combination with relebactam for strains producing ESBL or AmpC in addition to IMP-type, NDM-type, GES-type or OXA-48 carbapenemases and for Stenotrophomonas spp. Additionally, aztreonam/relebactam combination MICs were significantly lower than MICs of aztreonam alone among IMP producers, NDM producers and Stenotrophomonas spp. Significant differences between aztreonam/relebactam and aztreonam MICs were also observed for strains of E. coli, K. pneumoniae and Enterobacter spp., many of which produced both metallo-β-lactamase and serine‑β-lactamase. The aztreonam/relebactam combination showed comparable to higher MICs compared with the aztreonam/avibactam combination.

CONCLUSION

The addition of relebactam has a potential to restore the activity of aztreonam against strains that produce metallo-β-lactamase and serine‑β-lactamase. The combination may have a role in the treatment of infections due to these strains in countries without access to ceftazidime-avibactam.

Epidemiology and Genetic Traits of Carbapenemase-Producing Enterobacterales: A Global Threat to Human Health

Carbapenemase-producing Enterobacterales (CPE) represent an important threat to global health, resulting in an urgent issue in clinical settings. CPE often exhibit a multidrug-resistant (MDR) phenotype, thus reducing the antimicrobial armamentarium, with few antibiotics retaining residual antimicrobial activity against these pathogens. Carbapenemases are divided into three classes (A, B, and D) according to the Ambler classification system. Among these, KPC (class A), NDM, VIM, IMP (class B), and OXA-48-like (class D) represent the most important carbapenemases in terms of diffusion and clinical impact. CPE diffusion has been observed worldwide, with current endemicity in multiple territories around the world. In this context, the clonal spread and plasmid-mediated transmission of carbapenemases have contributed to the global spread of CPE worldwide and to the diffusion of carbapenemases among different Enterobacterales species. In recent years, novel molecules showing excellent in vitro and in vivo activity have been developed against CPE. However, the recent emergence of novel traits of resistance to these molecules has already been reported in several cases, mitigating the initial promising results. This review aims to provide an updated description of the major classes of carbapenemases, their global distribution, and future perspectives to limit the diffusion of CPEs.

High-risk Pseudomonas aeruginosa clones harboring β-lactamases: 2024 update

Carbapenem-resistant Pseudomonas aeruginosa is defined by the World Health Organization as a "high priority" in developing new antimicrobials. Indeed, the emergence and spread of multidrug-resistant (MDR) or extensively drug-resistant (XDR) bacteria increase the morbidity and mortality risk of infected patients. Genomic variants of P. aeruginosa that display phenotypes of MDR/XDR have been defined as high-risk global clones. In this mini-review, we describe some international high-risk clones that carry β-lactamase genes that can produce chronic colonization and increase infected patients' morbidity and mortality rates.

High level non-carbapenemase carbapenem resistance by overlaying mutations of mexR, oprD, and ftsI in Pseudomonas aeruginosa

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a global threat, but the mechanism of non-carbapenemase carbapenem resistance is still unclear. In the current study, we investigated the contributions of point mutations in mexR, oprD, and ftsI to carbapenem resistance in P. aeruginosa during in vivo evolution studies with consecutive clinical isolates. Real-time qPCR and Electrophoretic Mobility Shift Assay demonstrated that MexR (Gln55Pro) mutation increased MexAB efflux pump genes expression by altering MexR's binding capacity, leading to a four- to eight-fold increase in meropenem MIC in the Pae d1 Green ∆mexR and PAO1∆mexR mutants. The OprD (Trp415*) truncation affected porin structure, and the constructed mutant Pae d1 Green oprD Trp415* increased meropenem MIC by 16-fold (from 0.25 to 4 µg/mL). The contribution of ftsI mutation to meropenem resistance was confirmed by clinical linkage analysis and was estimated to cause a two-fold increase in meropenem MIC by comparing the resistant clinical isolate with the Pae d1 Green oprD Trp415*∆mexR double mutant. The study found that the oprD Trp415* allele alone accounts for the imipenem MIC in clinical isolates, while the ∆mexR and ftsI Arg504Cys alleles do not contribute to imipenem resistance. In conclusion, we identified and explored the contributions of mexR, oprD, and ftsI mutations to high level non-carbapenemase carbapenem resistance in P. aeruginosa. These findings highlight the interplay of different mutations in causing non-carbapenemase carbapenem-resistance in P. aeruginosa.

IMPORTANCE

The emergence of carbapenem-resistant Pseudomonas aeruginosa (CRPA) poses a significant global health threat, complicating treatment options for infections caused by this pathogen. Understanding the mechanisms behind non-carbapenemase carbapenem resistance is critical for developing effective therapeutic strategies. This study provides crucial insights into how specific point mutations in key genes-mexR, oprD, and ftsI-contribute to carbapenem resistance, particularly the MexR (Gln55Pro) mutation's effect on efflux pump expression and the OprD (Trp415*) truncation's impact on porin structure. The findings elucidate the complex interplay of these mutations, highlighting their roles in conferring high-level resistance, and underscore the imperative for continued research to inform therapeutic strategies against CRPA infections.

The Contribution of Carbapenem-Resistant Pseudomonas Aeruginosa Isolation to Clinical Outcomes in Hospitalized Patients with Exacerbations of Bronchiectasis: A Retrospective Cohort Study

BACKGROUND

The antibiotic resistance of Pseudomonas aeruginosa (PA) is increasingly severe in bronchiectasis patients. However, there is currently a lack of research on the clinical outcomes of carbapenem-resistant PA (CRPA) isolation in hospitalized exacerbations of bronchiectasis (HEB) patients. We investigated the incidence, risk factors, and clinical outcomes of PA and CRPA isolation in HEB patients.

METHODS

This was an observational, retrospective cohort study of PA and CRPA isolated from sputum or bronchoalveolar lavage fluid cultures of HEB patients from January 1, 2018 to December 31, 2022. The primary outcomes were respiratory failure, mechanical ventilation, and length of hospital stay. The incidence, risk factors, and clinical outcomes of PA and CRPA isolation were analyzed using multivariate logistic and Poisson regression.

RESULTS

Among 1,286 patients, the prevalence of PA, CRPA, and multi-drug resistant PA isolation was 20.61% (n = 265), 3.81% (n = 49), and 5.83% (n = 75), respectively. CRPA isolation was associated with an increased risk for respiratory failure (adjusted odds ratio (aOR) 2.56; 95% confidence interval (CI) [1.29, 5.11]; p = 0.007), mechanical ventilation (aOR 3.65; 95% CI [1.50, 8.92]; p = 0.004), and length of hospital stay (Coefficient (Coef) 0.27; 95% CI [0.18,0.35]; p < 0.001) compared to non-CRPA. Antibiotic treatment decreased the risk of respiratory failure (aOR 0.37; 95% CI [0.17, 0.80]; p = 0.011), mechanical ventilation (aOR 0.36; 95% CI [0.13, 0.99]; p = 0.047), and length of hospital stay (Coef - 0.23; 95% CI [- 0.33, - 0.14]; p < 0.001).

CONCLUSIONS

CRPA isolation was identified in more severe bronchiectasis patients and significantly increased the risk of respiratory failure, mechanical ventilation and length of hospital stay, while antibiotic treatment reduced this risk.

Genomic analysis of blaNDM-1-carrying-Pseudomonas aeruginosa ST2407 in the chromosome from Brazil

Pseudomonas aeruginosa, an opportunistic pathogen often found in Healthcare-associated infections (HAI), has shown increased resistance to carbapenems (imipenem, meropenem, doripenem), the primary treatment options. We've seen a rise in carbapenemase-producing P. aeruginosa in Brazil, including NDM-producers. This study characterises an isolate carrying blaNDM-1 from a patient's skin fragment in a Brazilian hospital. The whole genomic sequence (WGS) of P. aeruginosa CCBH26428 was extracted and sequenced using Illumina and minION platforms. The assembly used MinION results mapped with Illumina reads, and annotation was performed by the RAST server. Resistance genes and clonality were identified using the CABGen platform. Additional information was carried out by manual annotation using Geneious software and BLAST tool. The genomic analysis revealed a genome of 6.995.008 bp and G+C 65.9 %. P. aeruginosa CCBH26428 belongs to ST2407. The blaNDM gene, associated with ISAba125, was found in a 63.862 pb genomic region flanked by IS26 insertion sequences. This region also contained the repA of the plasmid incompatibility group IncC2 and other resistance genes, suggesting it is a possible "translocation unit". Additionally, 17 resistance genes, mutations in OprD and GyrA, and several virulence genes were detected, potentially exacerbating the infection. This study is report a WGS analysis of P. aeruginosa carrying blaNDM-1 in Brazil, highlighting the role of IS26 in the acquisition and spread of resistance genes between plasmids and chromosomes.

In vitro activity of ceftazidime-avibactam/aztreonam combination against MBL-producing Pseudomonas aeruginosa strains

PURPOSE

The emergence of multidrug-resistant P. aeruginosa isolates poses a challenge to healthcare systems worldwide. Rising numbers in deaths, duration of hospitalization as well as failing treatments prove the hazards posed by these pathogens. This and the lack of promising therapeutic options highlight the urgency of antibiotic drug development. As interim solution or alternative to the development of new antibiotic drugs, investigation of novel combinations of existing antibiotic drugs can be an economic and swift approach. Therefore, this study addresses the evaluation of in vitro activity of the antibiotic combination of ceftazidime-avibactam/aztreonam against MBL-producing P. aeruginosa strains.

METHODS

We tested 153 isolates from six university hospitals via microdilution against their susceptibility to meropenem, aztreonam, ceftazime-avibactam and the minimal inhibitory concentration of the combination of ceftazidime-avibactam/aztreonam. 64 isolates produced carbapenemases of which 61 were VIM-, 2 NDM- and 1 OXA-producer.

RESULTS

We were able to show that the synergetic effects of this regimen with an avibactam concentration of 4 mg/l and an aztreonam concentration of 16 mg/l could successfully lower the number of MBL-producing isolates that showed a high minimal inhibitory concentration compared to a carbapenemase-negative control group in vitro.

CONCLUSION

The antibiotic combination consisting of ceftazidime-avibactam/aztreonam represents a possible approach to the treatment of patients infected with multidrug-resistant P. aeruginosa isolates.

Trends and implications of antimicrobial resistance in Pseudomonas aeruginosa: Insights from a 19-year study in Zhejiang Province

This study aimed to elucidate the resistance trends of P. aeruginosa isolates from 2005 to 2023 in Zhejiang Province, emphasizing the impact of Coronavirus disease 2019 (COVID-19) on antimicrobial resistance patterns and clinical management. We retrospectively analyzed 7326 P. aeruginosa isolates collected from diverse clinical sources in a tertiary hospital in Zhejiang Province from 2005 to 2023. Identification and antibiotic susceptibility testing of each isolate were performed using the VITEK-32 automated system and the disk diffusion method, following Clinical and Laboratory Standards Institute guidelines. We assessed resistance patterns for key antibiotic classes relevant to P. aeruginosa treatment, including carbapenems, β-lactams, aminoglycosides, and quinolones. Statistical analyses, including trend evaluations and resistance determinant assessments, were conducted in R software (version 4.2.2), with visualizations generated through ggplot2 to illustrate resistance trends over time. This study focused on key anti-pseudomonal agents including carbapenems (imipenem and meropenem), β-lactams (piperacillin), and quinolones (ciprofloxacin and levofloxacin). We observed a progressive increase in resistance to imipenem from 6.8% in 2005 to 48.2% in 2023 and meropenem from 25.4% to 44.2% over the same period. Conversely, resistance rates to aminoglycosides declined, with gentamicin resistance dropping from 22.0% in 2005 to 5.0% in 2019. Cephalosporins exhibited variable trends, with cefepime resistance peaking at 40.4% in 2013 before declining to 12.1% in 2023. The findings indicated a progressive increase in resistance rates for these antibiotics, with notable peaks coinciding with changes in clinical practices and the COVID-19 pandemic. The analysis demonstrated that shifts in prescription habits, particularly during the COVID-19 pandemic, influenced resistance patterns, underscoring the need for context-specific antimicrobial stewardship strategies. This study identifies significant, evolving resistance patterns in P. aeruginosa over a 19-year period, with marked increases in resistance to critical antibiotics, including carbapenems (imipenem, meropenem), quinolones (levofloxacin, ciprofloxacin), and certain β-lactams (piperacillin). These findings underscore an urgent need for dynamic, tailored infection control measures, emphasizing the importance of robust antibiotic stewardship programs, localized treatment guidelines, and proactive monitoring of resistance trends. Implementing these strategies is essential to effectively counter the challenges posed by multi-drug resistant P. aeruginosa, improve patient outcomes, and sustain the efficacy of vital antibiotic therapies.

In vitro activity assessment of cefiderocol against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter spp., including β-lactam nonsusceptible molecularly characterized isolates, collected from 2020 to 2021 in the United States and European hospitals

This study reports the activity of cefiderocol against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter spp. isolates collected from the United States and Europe, including Israel and Turkey, from 2020 to 2021. Among Enterobacterales, 2.8% were carbapenem nonsusceptible (CNSE); cefiderocol inhibited 96.6%/85.1% [Clinical Laboratory Standards Institute (CLSI)/European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints] of these isolates. Imipenem-relebactam, meropenem-vaborbactam, and ceftazidime-avibactam displayed susceptibilities lower than cefiderocol against CNSE isolates (67.4-84.6% susceptible, CLSI). Cefiderocol was the only agent active against CNSE isolates carrying metallo-β-lactamase (MBL) carbapenemase or multiple carbapenemase genes (84.6%-92.3% susceptible, CLSI). Approximately 18% of carbapenem-susceptible Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis carried extended-spectrum-β-lactamases and/or plasmid-borne AmpC-encoding genes; cefiderocol inhibited 99.8%-100.0% (CLSI) of these genotypic groups. Multi-drug resistance (MDR) phenotypes were observed in 16.9% and 52.5% of P. aeruginosa and A. baumannii-calcoaceticus isolates, respectively. Carbapenemase genes were rare (4.9%) among cephalosporin and/or carbapenem nonsusceptible P. aeruginosa, compared to 87.6% carriage in A. baumannii-calcoaceticus, respectively. Against the MDR and carbapenemase-carrying P. aeruginosa and A. baumannii-calcoaceticus subsets, cefiderocol was active against 98.6%/98.7% and 97.1%/97.4% (CLSI), respectively. Only 69 isolates (0.3%) across all species groups were identified as cefiderocol nonsusceptible per CLSI criteria (>4 mg/L). Cefiderocol was the most active agent in vitro against Enterobacterales, P. aeruginosa, and Acinetobacter spp., with uniform activity against all phenotypic- and genotypic-resistant subsets. Coupled with the low incidence of nonsusceptibility observed across species groups, these results demonstrate cefiderocol as an important option for treating infections caused by pathogens with diverse mechanisms of resistance in US and European hospitals.IMPORTANCEThe worldwide spread of multi-drug-resistant Pseudomonas aeruginosa and carbapenem-resistant Enterobacterales and Acinetobacter spp. poses a serious challenge in healthcare settings as infections caused by these organisms are commonly refractory to many frontline therapeutic agents. Multiple global health organizations highlighted these pathogens as critical priorities for new antibiotic development, thus necessitating continued surveillance of the activities of currently available antimicrobial agents and circulating mechanisms of resistance. To meet this need, this study phenotypically and genotypically characterized priority Gram-negative pathogens collected from patients in US and European hospitals to examine the activity of cefiderocol and other currently available treatment options, including carbapenems and β-lactam-β-lactamase inhibitor combinations. The results presented here provide a detailed perspective to healthcare practitioners of cefiderocol's broad applicability, manifested in high activity and low nonsusceptibility rates, across phenotypic and genotypic organism groups relative to other agents and further support its use against the most intransigent infections.

In-vitro activities of essential antimicrobial agents including aztreonam/avibactam, eravacycline, colistin and other comparators against carbapenem-resistant bacteria with different carbapenemase genes: A multi-centre study in China, 2021

OBJECTIVE

Carbapenem-resistant bacteria (CRB), including carbapenem-resistant Acinetobacter baumannii (CRAB), carbapenem-resistant Pseudomonas aeruginosa (CRPA) and carbapenem-resistant Enterobacterales (CRE), pose a considerable threat to public health in China. Eravacycline, aztreonam/avibactam and colistin are important antimicrobial agents for the treatment of serious infections caused by CRB. This study aimed to evaluate the prevalence of CRB strains, and the susceptibility of commonly used clinical antimicrobial agents against strains with different carbapenemase genes.

METHODS

In total, 7194 gram-negative bacteria strains were collected from different regions of China, and 924 carbapenem-resistant strains were identified. All strains were from confirmed infections. Antimicrobial susceptibility testing, covering 21 antimicrobial agents including aztreonam/avibactam, eravacycline, colistin and other comparators, was performed using the broth microdilution method. Carbapenemase genes (blaKPC, blaNDM, blaOXA, blaIMP and blaVIM) were screened using polymerase chain reaction amplification and sequence analysis. All statistical analyses were performed using Statistical Package for the Social Sciences Version 23.0.

RESULTS

The isolation rates of CRE, CRAB and CRPA were 6.31% (332/5265), 62.95% (440/699) and 15.20% (152/1000), respectively. The predominant carbapenemase in carbapenem-resistant Escherichia coli (CRECO) was NDM, while in carbapenem-resistant Klebsiella pneumoniae (CRKP), it was KPC. All CRAB produced OXA-23, and 85.52% of CRPA did not produce any of the following carbapenemases: NDM, KPC, VIM, IMP and OXA. Aztreonam/avibactam, colistin and eravacycline exhibited high antimicrobial activity against different species producing various carbapenemases. Compared with ceftazidime/avibactam, aztreonam/avibactam demonstrated superior antimicrobial activity, particularly pronounced in CRECO and strains producing metallo-beta-lactamases. In comparisons between tigecycline and eravacycline, the latter maintained higher antimicrobial activity across different species. Antimicrobial agents exhibited varying levels of activity against strains with different resistance mechanisms.

CONCLUSIONS

Using aztreonam/avibactam, eravacycline and colistin to treat infections caused by CRB offers significant advantages. These findings will guide clinical practice and optimize antimicrobial administration.

The Synergy of Machine Learning and Epidemiology in Addressing Carbapenem Resistance: A Comprehensive Review

BACKGROUND/OBJECTIVES

Carbapenem resistance poses a significant threat to public health by undermining the efficacy of one of the last lines of antibiotic defense. Addressing this challenge requires innovative approaches that can enhance our understanding and ability to combat resistant pathogens. This review aims to explore the integration of machine learning (ML) and epidemiological approaches to understand, predict, and combat carbapenem-resistant pathogens. It examines how leveraging large datasets and advanced computational techniques can identify patterns, predict outbreaks, and inform targeted intervention strategies.

METHODS

The review synthesizes current knowledge on the mechanisms of carbapenem resistance, highlights the strengths and limitations of traditional epidemiological methods, and evaluates the transformative potential of ML. Real-world applications and case studies are used to demonstrate the practical benefits of combining ML and epidemiology. Technical and ethical challenges, such as data quality, model interpretability, and biases, are also addressed, with recommendations provided for overcoming these obstacles.

RESULTS

By integrating ML with epidemiological analysis, significant improvements can be made in predictive accuracy, identifying novel patterns in disease transmission, and designing effective public health interventions. Case studies illustrate the benefits of interdisciplinary collaboration in tackling carbapenem resistance, though challenges such as model interpretability and data biases must be managed.

CONCLUSIONS

The combination of ML and epidemiology holds great promise for enhancing our capacity to predict and prevent carbapenem-resistant infections. Future research should focus on overcoming technical and ethical challenges to fully realize the potential of these approaches. Interdisciplinary collaboration is key to developing sustainable strategies to combat antimicrobial resistance (AMR), ultimately improving patient outcomes and safeguarding public health.

Characterization of the Chromosomally Located Metallo-β-Lactamase Genes blaIMP-45 and blaVIM-2 in a Carbapenem-Resistant Pseudomonas aeruginosa Clinical Isolate

Objective: Characterization of the multidrug resistance (MDR) region in P. aeruginosa strain PA59 revealed the presence of antibiotic resistance genes, including blaIMP-45 and blaVIM-2, within a complex genetic landscape of mobile genetic elements. Methods: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) strains were isolated from Shanghai Changhai Hospital. Polymerase chain reaction (PCR) was used to detect the β-lactamase genes in the isolated strains. Strains carrying two or more genes were subjected to whole-genome sequencing (WGS) and in-depth bioinformatics analysis. Results: A total of 94 CRPA strains were isolated, among which PA59 was determined to carry blaIMP-45 and blaVIM-2 genes. Compared with single-gene positive or other blaIMP and blaVIM dual-gene positive strains reported, PA59 exhibited a broader range of drug resistance. We discovered a multidrug resistant (MDR)-related region composed of various mobile elements in the PA59 chromosome. This region carried many resistance genes, including the target genes blaIMP-45 and blaVIM-2. By further comparing the mobile elements GI13 and Ph08, we speculated that this integron structure carrying blaIMP-45 and blaVIM-2 was initially integrated into the genomic island or prophage, forming a more complex genetic structure, and then further integrated into the PA59 chromosome through plasmids. Phylogenetic tree analysis showed limited sequence similarity between PA59 and other CRPA strains. Conclusions: This study identified PA59 as the first reported P. aeruginosa strain carrying both blaIMP-45 and blaVIM-2 on the chromosome. The assembly and annotation of the PA59 genome provide valuable insights into the genomic diversity and gene content of this clinically important pathogen, aiding the development of effective strategies against antibiotic resistance.

Risk factors for Pseudomonas aeruginosa VIM colonization or infection in the ICU: Case-control study

BACKGROUND

Carbapenem-resistant strains of Pseudomonas aeruginosa (CRPA) have become a major health care concern in many countries, against which anti-infective strategies are limited and which require adequate infection control interventions. Knowing the different modes of transmission of CRPA in intensive care units (ICUs) would be helpful to adapt the means of prevention.

METHODS

The aim of this retrospective case-control study was conducted between January 1, 2017 and February 28, 2022 to identify the risk factors for the acquisition of CRPA in ICUs.

RESULTS

During the study period, 147 patients were included (49 cases and 98 controls). Among the 49 patients, 31 (63%) acquired CRPA in clusters and 18 (37%) sporadically. A univariate analysis showed that 4 variables were associated with CRPA acquisition, including (1) prior antibiotic prescriptions, (2) admission to rooms 203 and 207, (3) severity of illness at admission, and (4) use of mechanical ventilation. Multivariate analysis identified 3 factors of CRPA acquisition, including admission to room 203 (odds ratio [OR] = 29.5 [3.52-247.09]), previous antibiotic therapy (OR = 3.44 [1.02-11.76]), and severity of condition at admission (OR = 1.02 [1-1.04]).

CONCLUSIONS

Our study suggests the role of a contaminated environment in the acquisition of CRPA in the ICU, along with antibiotic use.

Clinical and genomic characterization of carbapenem-resistant Enterobacterales bloodstream infections in patients with hematologic malignancies

Background

Carbapenem-resistant Enterobacterales (CRE) bloodstream infections (BSIs) pose a significant risk to patients with hematologic malignancies, yet the distinct features and outcomes of these infections are not thoroughly understood.

Methods

This retrospective study examined the characteristics and clinical outcomes of patients with Enterobacterales BSIs at the Hematology Department of Fujian Medical University Union Hospital from 2018 to 2022. Whole-genome sequencing was conducted on 45 consecutive CRE BSI isolates during this period.

Results

A total of 301 patients with Enterobacterales BSIs were included, with 65 (21.6%) cases of CRE and 236 (78.4%) cases of carbapenem-susceptible Enterobacterales (CSE). CRE infections accounted for 16.9% to 26.9% of all Enterobacterales BSIs, and carbapenem-resistant Klebsiella pneumoniae (CRKP) was the predominant strain. The most frequent sequence type (ST) and carbapenemase among CRKP were ST11 (68.6%) and blaKPC-2 (80.0%), respectively. Perianal infections, multiple infection foci, and a history of multiple hospitalizations, ICU stays, and prior CRE infections were identified as risk factors for CRE BSIs. Patients in the CRE group experienced significantly higher proportions of infection-related septic shock (43.1% vs. 19.9%, P < 0.0003) and 30-day all-cause mortality (56.9% vs. 24.6%, P < 0.0001) compared to those in the CSE group. Patient's age and disease subtypes, strain subtypes, and antimicrobial treatment regimens significantly influenced survival in patients with CRE BSIs.

Conclusions

CRE BSIs are a frequent complication in patients with hematological malignancies undergoing treatment and are associated with poor survival rates. A comprehensive understanding of risk factors and ongoing surveillance of prevalent strains are essential for the effective management of these infections.

Molecular epidemiology and carbapenem resistance mechanisms of Pseudomonas aeruginosa isolated from a hospital in Fujian, China

The worldwide spread of Pseudomonas aeruginosa, especially carbapenem-resistant P. aeruginosa (CRPA), poses a serious threat to global public health. In this research, we collected and studied the clinical prevalence, molecular epidemiology, and resistance mechanisms of CRPA in Fujian, China. Among 167 non-duplicated P. aeruginosa isolates collected during 2019-2021, strains from respiratory specimens and wound secretions of older males in the intensive care unit dominated. Ninety-eight isolates (58.7 %) were resistant to at least one tested antibiotic, among which 70 strains were carbapenem-resistant. Moleclar typing of the CRPA isolates revealed they were highly divergent, belonging to 46 different sequence types. It is noteworthy that two previously reported high risk clones, ST1971 specific to China and the globally prevalent ST357, were found. Several carbapenem resistance-related characteristics were also explored in 70 CRPA isolates. Firstly, carbapenemase was phenotypically positive in 22.9 % of CRPA, genetically predominant by metallo-β-lactamase (MBL) and co-carrige of different carbapenemase genes. Then, mutations of the carbapenem-specific porins oprD and opdP were commonly observed, with frequencies of 97.1% and 100.0%, respectively. Furthermore, the biofilm formation and relative transcription levels of 8 multidrug efflux pump genes were also found to be increased in 48.6 % and 72.9 % of CRPA isolates compared to the reference strain PAO1. These findings will help fill the data gaps in molecular characteristics of CRPA on the southeastern coast of China and emphasize the urgent need for data-based specific stewardship for antipseudomonal practices to prevent the dissemination of CRPA.

Simultaneous clonal spread of NDM-1-producing Pseudomonas aeruginosa ST773 from Ukrainian patients in the Netherlands and Spain

Objectives

We describe the clonal spread of New Delhi metallo-β-lactamase (NDM) 1-producing Pseudomonas aeruginosa isolates belonging to the ST773 clone in Spain and the Netherlands, associated with the transfer of Ukrainian patients during the war.

Methods

Between March and December 2022, nine NDM-1-producing P. aeruginosa ST773 isolates were recovered from nine Ukrainian patients evacuated to two Spanish (n = 3) and five Dutch (n = 6) hospitals. Antimicrobial susceptibility testing was studied (Sensititre, Microscan, EUCAST-2023). Whole genome sequencing (Illumina, Oxford-Nanopore) was used to analyze the genetic relatedness, the resistome, and the prophage content.

Results

All NDM-1-producing P. aeruginosa ST773 isolates exhibited resistance to all tested antimicrobials except colistin, aztreonam, and cefiderocol. Genomic analysis revealed that all isolates had an identical resistome and a chromosomally encoded integrative conjugative element carrying the bla NDM-1 gene. The core genome multilocus sequence typing and core genome single nucleotide polymorphisms analysis showed highly related isolates, irrespective of country of isolation, distant from other NDM-1-ST773 P. aeruginosa not collected in Ukraine. Both analysis revealed two closely related clusters, spanning the Spanish and Dutch isolates. In addition, a high content of prophages was identified in all strains, most of them in more than one isolate simultaneously, regardless of their origin country. Moreover, an identical phage tail-like bacteriocin cluster was identified in all NDM-1-ST773 P. aeruginosa.

Conclusions

We report a clonal dissemination of NDM-producing P. aeruginosa ST773 to the Netherlands and Spain associated with patients from Ukraine. Our work highlights the importance of genomic surveillance and to understand the dynamics of resistance in multidrug-resistant bacteria after the transfer of patients from conflict zones. International collaboration is crucial to address global antimicrobial resistance.

Genomic and Phylogenomic Characterization of Carbapenem-resistant Pseudomonas aeruginosa 'High-risk' Clone O4/ExoS+/ST654 Circulating in Chilean Hospitals

INTRODUCTION

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a serious threat to public health. Globally, carbapenemases-producing CRPA isolates mainly belong to 'high-risk' clones; however, the molecular epidemiology of CRPA isolates circulating in Chile are scarce, where this pathogen is the main aetiological agent of ventilator-associated pneumonia.

OBJECTIVES

To characterize the phylogenomics and molecular features of ST654 CRPA isolates collected in Chile between 2016 and 2022.

METHODS

Eighty-nine CRPA isolates collected in different Chilean hospitals from clinical specimens between 2005 and 2022 were analysed. Antibiotic susceptibility tests and carbapenemases production were carried out on the CRPA ST654 isolates. Also, they were subjected to whole-genome sequencing, from which in silico analyses were performed.

RESULTS

Thirty-four strains (38.2%) belonged to the ST654 high-risk clone, being the most predominant lineage of the collection. Most of these isolates belonged to a subclade including KPC producers that also clustered with strains from Argentina and the United States, whereas few VIM and NDM co-producers clustered in two different smaller subclades. The isolates exhibited a broad resistome encompassing genes mediating resistance to several other clinically relevant drugs. Additionally, all the 34 ST654 isolates were ExoS+ as a virulence factor and associated to the O4-serotype.

CONCLUSIONS

Our report represents the most comprehensive phylogenomic study of a CRPA high-risk clone ST654 to date. Our analyses suggest that this lineage is undergoing a divergent evolutionary path in Chile, because most of the isolates were KPC producers and were O4 serotype, differing from previous descriptions, which underline the relevance of performing molecular surveillance on this pathogen.

Emergence of NDM-1-Producing Pseudomonas aeruginosa Nosocomial Isolates in Attica Region of Greece

Here, we report on the emergence and spread of multidrug-resistant NDM-1-producing P. aeruginosa isolates from patients hospitalized in the Attica region, Greece, in 2022 to provide data on their resistome, their virulome, the genetic environment of blaNDM-1, and their molecular epidemiology. A total of 17 carbapenem-resistant P. aeruginosa isolates identified as NDM-producers by immunochromatography at the hospital level were sent to the Central Public Health Laboratory, in the frame of the laboratory surveillance of carbapenem-resistant pathogens, for further characterization. The initial screening for genetic AMR determinants was carried out by PCR and the MDR Direct Flow Chip assay. Typing was performed by MLST and DLST, the latter in a subset of isolates. Further analysis was performed by whole-genome sequencing (WGS) of six isolates from both hospitals to analyze their entire genomes and elucidate their genetic relatedness. All isolates were allocated to international high-risk clones, sixteen to ST773 and one to ST308. Five ST773 and the sole ST308 isolate were found to harbor the blaNDM-1 gene, along with various other ARGs integrated into their chromosomes, as well as with a wide variety of virulence genes. The blaNDM-1 gene was located in the integrative and conjugative elements ICE6600-like and ICETn43716385 in ST773 and ST308 isolates, respectively. Single-nucleotide polymorphism analysis of the five ST773 isolates indicated their clonal spread in both hospitals. These results suggested that two different molecular events contributed to the emergence of NDM-1-producing P. aeruginosa isolates in Athenian hospitals, highlighting the need for ongoing surveillance.

Hospital wastewater as source of human pathogenic bacteria: A phenotypic and genomic analysis of international high-risk clone VIM-2-producing Pseudomonas aeruginosa ST235/O11

Pseudomonas aeruginosa belong to the special pathogen group capable of causing serious infections, with high mortality rates. The aim of this study was to describe the antibiotic resistance and genomic characteristics of Pseudomonas aeruginosa belonging to international high-risk clone ST235 (GPAE0131 isolate), obtained from hospital wastewater. P. aeruginosa GPAE0131 was isolated from ward tertiary hospital in Brazil and the antibiotic resistance profile was determined by the disc-diffusion method. Genomic characteristics related to antibiotic resistance and virulence factors were evaluated by genomic DNA sequencing on the Illumina MiSeq platform and bioinformatic analysis. GPAE0131 isolate showed resistance to piperacillin-tazobactam, cefepime, ceftazidime, imipenem, meropenem, ciprofloxacin, levofloxacin and tobramycin. Resistome comprehend of resistance genes to β-lactams (blaVIM-2, blaOXA-4, blaOXA-488, blaPDC-35), aminoglycosides (aph(3')-IIb, aac(6')-IIc, aac(6')-Ib9, aadA1), fosfomycin (fosA), chloramphenicol (catB7) and sulfonamides (sul1). Genome comparisons evidence insertion of blaVIM-2 and blaOXA-4 genes. GPAE0131 isolate was predicted to be pathogenic to humans and several virulence factors were found, including encoding gene for ExoU and exotoxin A. All of these features into a pathogenic international high-risk clone (ST235), classified as critical priority, stands out as public health concern due to the widespread dispersal of human pathogens through wastewater. It is suggested that mitigating measures be implemented, such as the treatment of hospital sewage and the addition of tertiary treatment, to prevent the escape of pathogens at this level into the environment.

Two cinnamoyl hydroxamates as potential quorum sensing inhibitors against Pseudomonas aeruginosa

Introduction

Pseudomonas aeruginosa is a ubiquitous pathogen that causes various infectious diseases through the regulation of quorum sensing (QS). The strategy of interfering with the QS systems of P. aeruginosa, coupled with a reduction in the dosage of conventional antibiotics, presents a potential solution to treating infection and mitigating antibiotic resistance. In this study, seven cinnamoyl hydroxamates were synthesized to evaluate their inhibitory effects on QS of P. aeruginosa. Among these cinnamic acid derivatives, we found cinnamoyl hydroxamic acid (CHA) and 3-methoxy-cinnamoyl hydroxamic acid (MCHA) were the two most effective candidates. Furtherly, the effect of CHA and MCHA on the production of virulence factors and biofilm of P. aeruginosa were evaluated. Ultimately, our study may offer promising potential for treating P. aeruginosa infections and reducing its virulence.

Methods

The disc diffusion test were conducted to evaluate inhibitory effects on QS of seven cinnamoyl hydroxamates. The influence of CHA and MCHA on the production of virulence and flagellar motility of P. aeruginosa was furtherly explored. Scanning electron microscopy (SEM) experiment were conducted to evaluate the suppression of CHA and MCHA on the formed biofilm of P. aeruginosa. RT-qPCR was used to detect rhlI, lasA, lasB, rhlA, rhlB, and oprL genes in P. aeruginosa. In silico docking study was performed to explore the molecular mechanism of CHA and MCHA. The synergistic effects of CHA with gentamicin were detected on biofilm cell dispersal.

Result

After treatment of CHA or MCHA, the production of multiple virulence factors, including pyocyanin, proteases, rhamnolipid, and siderophore, and swimming and swarming motilities in P. aeruginosa were inhibited significantly. And our results showed CHA and MCHA could eliminate the formed biofilm of P. aeruginosa. RT-qPCR revealed that CHA and MCHA inhibited the expression of QS related genes in P. aeruginosa. Molecular docking indicated that CHA and MCHA primarily inhibited the RhlI/R system in P. aeruginosa by competing with the cognate signaling molecule C4-HSL.Additionally, CHA exhibited potent synergistic effects with gentamicin on biofilm cell dispersal.

Discussion

P. aeruginosa is one of the most clinically and epidemiologically important bacteria and a primary cause of catheter-related urinary tract infections and ventilator-associated pneumonia. This study aims to explore whether cinnamoyl hydroxamates have inhibitory effects on QS. And our results indicate that CHA and MCHA, as two novel QSIs, offer promising potential for treating P. aeruginosa infections and reducing its virulence.

Polymerized cyclodextrin microparticles for sustained antibiotic delivery in lung infections

Pulmonary infections complicate chronic lung diseases requiring attention to both the pathophysiology and complexity associated with infection management. Patients with cystic fibrosis (CF) struggle with continuous bouts of pulmonary infections, contributing to lung destruction and eventual mortality. Additionally, CF patients struggle with airways that are highly viscous, with accumulated mucus creating optimal environments for bacteria colonization. The unique physiology and altered airway environment provide an ideal niche for bacteria to change their phenotype often becoming resistant to current treatments. Colonization with multiple pathogens at the same time further complicate treatment algorithms, requiring drug combinations that can challenge CF patient tolerance to treatment. The goal of this research initiative was to explore the utilization of a microparticle antibiotic delivery system, which could provide localized and sustained antibiotic dosing. The outcome of this work demonstrates the feasibility of providing efficient localized delivery of antibiotics to manage infection using both preclinical in vitro and in vivo CF infection models. The studies outlined in this manuscript demonstrate the proof-of-concept and unique capacity of polymerized cyclodextrin microparticles to provide site-directed management of pulmonary infections.

Comparison of Different Methods for Assaying the In Vitro Activity of Cefiderocol against Carbapenem-Resistant Pseudomonas aeruginosa Strains: Influence of Bacterial Inoculum

Carbapenem-resistant Pseudomonas aeruginosa infections represent a critical public health concern, highlighting the need for the development of effective antibiotics. Cefiderocol demonstrated potent in vitro activity against Pseudomonas aeruginosa, particularly in strains that are resistant to other drugs. However, concerns regarding the emergence of drug-resistant strains persist. This study, conducted with 109 carbapenem-resistant Pseudomonas aeruginosa strains from the Spanish Hospital (Dr. Balmis, Alicante). The study evaluated susceptibility to cefiderocol in comparison to alternative antibiotics and including their susceptibility to bacterial inoculum, while assessing various testing methods. Our findings revealed high susceptibility to cefiderocol against carbapenem-resistant strains, with only 2 of 109 strains exhibiting resistance. Comparative analysis demonstrated superiority of cefiderocol towards alternative antibiotics. Both the E-test and disk-diffusion methods showed 100% concordance with the microdilution method in classifying strains as susceptible or resistant. However, 4.6% (5/109) of disc zone diameters fell within the technical uncertainty zone, so the E-test technique was found to be more useful in routine clinical practice. Additionally, escalating bacterial inoculum correlated with decreases in vitro activity, so this parameter should be adjusted very carefully in in vivo studies. This study underscores cefiderocol's potential as a therapeutic option for carbapenem-resistant Pseudomonas aeruginosa infections. However, the emergence of drug-resistant strains emphasizes the critical need for a wise use of antibiotics and a continuous monitoring of resistance to antibiotics. Based on our in vitro data, further investigation concerning the impact of bacterial inoculum on drug efficacy is warranted in order to detect resistance mechanisms and optimize treatment strategies, thereby mitigating the risk of resistance.

Patient outcomes by baseline pathogen resistance phenotype and genotype in CERTAIN-1, a Phase 3 study of cefepime-taniborbactam versus meropenem in adults with complicated urinary tract infection

CERTAIN-1 was a Phase 3, double-blind, randomized, parallel group study of the efficacy and safety of cefepime-taniborbactam versus meropenem in the treatment of adults with complicated urinary tract infection (cUTI), including acute pyelonephritis. We determined susceptibility of Enterobacterales and Pseudomonas aeruginosa baseline pathogens to cefepime-taniborbactam and comparators and characterized β-lactam resistance mechanisms. Microbiologic response and clinical response were assessed in patient subsets defined by baseline pathogens that were of cefepime-, multidrug-, or carbapenem-resistant phenotype or that carried β-lactamase genes. Among Enterobacterales baseline pathogens, 26.8%, 4.1%, and 3.0% carried genes for extended-spectrum β-lactamases (ESBLs), AmpC, and carbapenemases, respectively. Within each treatment group, while composite success rates at Test of Cure in resistant subsets by pathogen species were similar to those by pathogen overall, composite success rates in meropenem patients were numerically lower for cefepime-resistant Escherichia coli (9/19; 47.4%) and ESBL E. coli (13/25; 52.0%) compared with E. coli overall (62/100; 62.0%). Cefepime-taniborbactam achieved composite success in 7/8 (87.5%) patients with carbapenem-resistant Enterobacterales and 8/9 (88.9%) patients with Enterobacterales with a carbapenemase gene (5 OXA-48-group; 2 KPC-3; 2 NDM-1). Cefepime-taniborbactam also achieved composite success in 8/16 (50.0%) patients and clinical success in 13/16 (81.3%) patients with P. aeruginosa; corresponding rates were 4/7 (57.1%) and 6/7 (85.7%) for meropenem. Cefepime-taniborbactam demonstrated efficacy in adult cUTI patients with cefepime-, multidrug-, and carbapenem-resistant pathogens including pathogens with ESBL, AmpC, and carbapenemase genes.

CLINICAL TRIALS

This study is registered with ClinicalTrials.gov as NCT03840148.

Variation in the response to antibiotics and life-history across the major Pseudomonas aeruginosa clone type (mPact) panel

Pseudomonas aeruginosa is a ubiquitous, opportunistic human pathogen. Since it often expresses multidrug resistance, new treatment options are urgently required. Such new treatments are usually assessed with one of the canonical laboratory strains, PAO1 or PA14. However, these two strains are unlikely representative of the strains infecting patients, because they have adapted to laboratory conditions and do not capture the enormous genomic diversity of the species. Here, we characterized the major P. aeruginosa clone type (mPact) panel. This panel consists of 20 strains, which reflect the species' genomic diversity, cover all major clone types, and have both patient and environmental origins. We found significant strain variation in distinct responses toward antibiotics and general growth characteristics. Only few of the measured traits are related, suggesting independent trait optimization across strains. High resistance levels were only identified for clinical mPact isolates and could be linked to known antimicrobial resistance (AMR) genes. One strain, H01, produced highly unstable AMR combined with reduced growth under drug-free conditions, indicating an evolutionary cost to resistance. The expression of microcolonies was common among strains, especially for strain H15, which also showed reduced growth, possibly indicating another type of evolutionary trade-off. By linking isolation source, growth, and virulence to life history traits, we further identified specific adaptive strategies for individual mPact strains toward either host processes or degradation pathways. Overall, the mPact panel provides a reasonably sized set of distinct strains, enabling in-depth analysis of new treatment designs or evolutionary dynamics in consideration of the species' genomic diversity.

IMPORTANCE

New treatment strategies are urgently needed for high-risk pathogens such as the opportunistic and often multidrug-resistant pathogen Pseudomonas aeruginosa. Here, we characterize the major P. aeruginosa clone type (mPact) panel. It consists of 20 strains with different origins that cover the major clone types of the species as well as its genomic diversity. This mPact panel shows significant variation in (i) resistance against distinct antibiotics, including several last resort antibiotics; (ii) related traits associated with the response to antibiotics; and (iii) general growth characteristics. We further developed a novel approach that integrates information on resistance, growth, virulence, and life-history characteristics, allowing us to demonstrate the presence of distinct adaptive strategies of the strains that focus either on host interaction or resource processing. In conclusion, the mPact panel provides a manageable number of representative strains for this important pathogen for further in-depth analyses of treatment options and evolutionary dynamics.

Screening of the PA14NR Transposon Mutant Library Identifies Genes Involved in Resistance to Bacteriophage Infection in Pseudomomas aeruginosa

Multidrug-resistant P. aeruginosa infections pose a serious public health threat due to the rise in antimicrobial resistance. Phage therapy has emerged as a promising alternative. However, P. aeruginosa has evolved various mechanisms to thwart phage attacks, making it crucial to decipher these resistance mechanisms to develop effective therapeutic strategies. In this study, we conducted a forward-genetic screen of the P. aeruginosa PA14 non-redundant transposon library (PA14NR) to identify dominant-negative mutants displaying phage-resistant phenotypes. Our screening process revealed 78 mutants capable of thriving in the presence of phages, with 23 of them carrying insertions in genes associated with membrane composition. Six mutants exhibited total resistance to phage infection. Transposon insertions were found in genes known to be linked to phage-resistance such as galU and a glycosyl transferase gene, as well as novel genes such as mexB, lasB, and two hypothetical proteins. Functional experiments demonstrated that these genes played pivotal roles in phage adsorption and biofilm formation, indicating that altering the bacterial membrane composition commonly leads to phage resistance in P. aeruginosa. Importantly, these mutants displayed phenotypic trade-offs, as their resistance to phages inversely affected antibiotic resistance and hindered biofilm formation, shedding light on the complex interplay between phage susceptibility and bacterial fitness. This study highlights the potential of transposon mutant libraries and forward-genetic screens in identifying key genes involved in phage-host interactions and resistance mechanisms. These findings support the development of innovative strategies for combating antibiotic-resistant pathogens.

Direct prediction of antimicrobial resistance in Pseudomonas aeruginosa by metagenomic next-generation sequencing

Objective

Pseudomonas aeruginosa has strong drug resistance and can tolerate a variety of antibiotics, which is a major problem in the management of antibiotic-resistant infections. Direct prediction of multi-drug resistance (MDR) resistance phenotypes of P. aeruginosa isolates and clinical samples by genotype is helpful for timely antibiotic treatment.

Methods

In the study, whole genome sequencing (WGS) data of 494 P. aeruginosa isolates were used to screen key anti-microbial resistance (AMR)-associated genes related to imipenem (IPM), meropenem (MEM), piperacillin/tazobactam (TZP), and levofloxacin (LVFX) resistance in P. aeruginosa by comparing genes with copy number differences between resistance and sensitive strains. Subsequently, for the direct prediction of the resistance of P. aeruginosa to four antibiotics by the AMR-associated features screened, we collected 74 P. aeruginosa positive sputum samples to sequence by metagenomics next-generation sequencing (mNGS), of which 1 sample with low quality was eliminated. Then, we constructed the resistance prediction model.

Results

We identified 93, 88, 80, 140 AMR-associated features for IPM, MEM, TZP, and LVFX resistance in P. aeruginosa. The relative abundance of AMR-associated genes was obtained by matching mNGS and WGS data. The top 20 features with importance degree for IPM, MEM, TZP, and LVFX resistance were used to model, respectively. Then, we used the random forest algorithm to construct resistance prediction models of P. aeruginosa, in which the areas under the curves of the IPM, MEM, TZP, and LVFX resistance prediction models were all greater than 0.8, suggesting these resistance prediction models had good performance.

Conclusion

In summary, mNGS can predict the resistance of P. aeruginosa by directly detecting AMR-associated genes, which provides a reference for rapid clinical detection of drug resistance of pathogenic bacteria.

In Silico Molecular Analysis of Carbapenemase-Negative Carbapenem-Resistant Pseudomonas aeruginosa Strains in Greece

To date, three carbapenem resistance mechanisms have been identified: carbapenemase released from the pathogen, changes in the expression of the outer membrane OprD porin, and overexpression of the efflux pump MexAB-OprM. Twelve carbapenemase-negative carbapenem-resistant Pseudomonas aeruginosa strains, isolated from patients hospitalized at the University Hospital of Larissa, Central Greece, during 2023, which belonged to various sequence types (STs), were selected and were studied focusing on the characterization of their β-lactamases, on changes to OprD and its regulator MexT proteins, and on alterations to the MexAB-OprM regulator proteins encoded by the mexR, nalC, and nalD genes. Whole genome sequencing analysis revealed the presence of β-lactamase encoding genes, with blaPAO present in all isolates. Additionally, seven different genes of the oxacillinase family (blaOXA-35, blaOXA-50, blaOXA-395, blaOXA-396, blaOXA-486, blaOXA-488, blaOXA-494) were identified, with each strain harboring one to three of these. Regarding the OprD, five strains had truncated structures, at Loop 2, Loop 3, Loop 4, and Loop 9, while the remaining strains carried previously reported amino acid changes. Further, an additional strain had a truncated MexR; whereas, two other strains had totally modified NalC sequences. The active form of MexT, responsible for the downregulation of OprD production, as the intact sequence of the NalD protein, was found in all the strains studied. It is concluded that the truncated OprD, MexR, and NalC proteins, detected in eight strains, probably led to inactive proteins, contributing to carbapenem resistance. However, four strains carried known modifications in OprD, MexR, and NalC, as previously reported in both susceptible and resistant strains, a finding that indicates the complexity of carbapenem resistance in P. aeruginosa.

Antibiotic susceptibility profile of Pseudomonas species isolated from clinical specimens to access, watch and reserve drugs across various hospital settings at a tertiary care hospital of central India

Background and Objectives

Over the last decade, hospital-acquired infections, particularly in the critical care setting, have become more common, with Gram-negative bacterial infections having the highest prevalence. This study aims to determine the prevalence and antibiotic susceptibility pattern of Pseudomonas species to WHO's, aware class of antibiotics, which are commonly prescribed across various ICU's, medical and surgical wards of our tertiary care teaching hospital.

Materials and Methods

This prospective study conducted from January 2021 to June 2022 at a tertiary care centre of central India identified Pseudomonas species from clinical samples using standard procedures and antimicrobial susceptibility testing performed as per Clinical Laboratory Standards Institute (CLSI) guidelines (M100; 32th Edition).

Results

A total of 1490 non duplicate Pseudomonas species isolates were grown from 21,019 culture positive clinical samples, of which 1247 were Pseudomonas aeruginosa. Out of these 1247 Pseudomonas aeruginosa 384 were MDR (30.7%). Pseudomonas aeruginosa were most commonly isolated from the pus samples (85%). ICU isolates were significantly more resistant to antibiotics than those from other units. P. aeruginosa strains from ICUs showed the highest rates of resistance to ceftazidime (93.9%). Reserve drug colistin showed good susceptibility (98.2%). All the 18 colistin resistant strains were found to be negative for plasmid mediated mcr-1,2,3 genes.

Conclusion

The study shall help to generate and disseminate the data so that proper antibiotic policy can be made for judicious use of Access, Watch and Reserve antibiotics and antibiotic de-escalation plan can be put forth.

Pseudomonasaeruginosa antimicrobial susceptibility profiles, resistance mechanisms and international clonal lineages: update from ESGARS-ESCMID/ISARPAE Group

SCOPE

Pseudomonas aeruginosa, a ubiquitous opportunistic pathogen considered one of the paradigms of antimicrobial resistance, is among the main causes of hospital-acquired and chronic infections associated with significant morbidity and mortality. This growing threat results from the extraordinary capacity of P. aeruginosa to develop antimicrobial resistance through chromosomal mutations, the increasing prevalence of transferable resistance determinants (such as the carbapenemases and the extended-spectrum β-lactamases), and the global expansion of epidemic lineages. The general objective of this initiative is to provide a comprehensive update of P. aeruginosa resistance mechanisms, especially for the extensively drug-resistant (XDR)/difficult-to-treat resistance (DTR) international high-risk epidemic lineages, and how the recently approved β-lactams and β-lactam/β-lactamase inhibitor combinations may affect resistance mechanisms and the definition of susceptibility profiles.

METHODS

To address this challenge, the European Study Group for Antimicrobial Resistance Surveillance (ESGARS) from the European Society of Clinical Microbiology and Infectious Diseases launched the 'Improving Surveillance of Antibiotic-Resistant Pseudomonas aeruginosa in Europe (ISARPAE)' initiative in 2022, supported by the Joint programming initiative on antimicrobial resistance network call and included a panel of over 40 researchers from 18 European Countries. Thus, a ESGARS-ISARPAE position paper was designed and the final version agreed after four rounds of revision and discussion by all panel members.

QUESTIONS ADDRESSED IN THE POSITION PAPER

To provide an update on (a) the emerging resistance mechanisms to classical and novel anti-pseudomonal agents, with a particular focus on β-lactams, (b) the susceptibility profiles associated with the most relevant β-lactam resistance mechanisms, (c) the impact of the novel agents and resistance mechanisms on the definitions of resistance profiles, and (d) the globally expanding XDR/DTR high-risk lineages and their association with transferable resistance mechanisms.

IMPLICATION

The evidence presented herein can be used for coordinated epidemiological surveillance and decision making at the European and global level.

Role of β-Lactamase Inhibitors as Potentiators in Antimicrobial Chemotherapy Targeting Gram-Negative Bacteria

Since the discovery of penicillin, β-lactam antibiotics have commonly been used to treat bacterial infections. Unfortunately, at the same time, pathogens can develop resistance to β-lactam antibiotics such as penicillins, cephalosporins, monobactams, and carbapenems by producing β-lactamases. Therefore, a combination of β-lactam antibiotics with β-lactamase inhibitors has been a promising approach to controlling β-lactam-resistant bacteria. The discovery of novel β-lactamase inhibitors (BLIs) is essential for effectively treating antibiotic-resistant bacterial infections. Therefore, this review discusses the development of innovative inhibitors meant to enhance the activity of β-lactam antibiotics. Specifically, this review describes the classification and characteristics of different classes of β-lactamases and the synergistic mechanisms of β-lactams and BLIs. In addition, we introduce potential sources of compounds for use as novel BLIs. This provides insights into overcoming current challenges in β-lactamase-producing bacteria and designing effective treatment options in combination with BLIs.

Assessing the in vivo impact of novel β-lactamase inhibitors on the efficacy of their partner β-lactams against serine carbapenemase-producing Pseudomonas aeruginosa using human-simulated exposures

OBJECTIVES

To evaluate the efficacy of human-simulated regimens (HSRs) of ceftazidime, ceftazidime/avibactam, imipenem, imipenem/relebactam, meropenem and meropenem/vaborbactam in a murine thigh infection model against serine carbapenemase-producing Pseudomonas aeruginosa.

METHODS

Nine P. aeruginosa clinical isolates harbouring GES-5 (n = 1), GES-20 (n = 1), GES-5/20 (n = 1), GES-19, GES-20 (n = 3) and KPC (n = 3) were evaluated. Six mice were administered HSRs of ceftazidime 2 g q8h (2 h infusion), ceftazidime/avibactam 2.5 g q8h (2 h infusion), meropenem 2 g q8h (3 h infusion), imipenem 0.5 g q6h (0.5 h infusion), imipenem/relebactam 1.25 g q6h (0.5 h infusion) and meropenem/vaborbactam 4 g q8h (3 h infusion). Change in bacterial burden relative to baseline and the percent of isolates meeting the 1 log10 kill endpoint were assessed.

RESULTS

The addition of avibactam to ceftazidime increased the percentage of isolates meeting 1 log10 kill from 33% to 100% of GES- or KPC-harbouring isolates. Imipenem/relebactam HSR produced ≥1 log10 of kill against 83% and 100% of GES- and KPC-harbouring isolates, respectively, while imipenem alone failed to reach 1 log10 kill for any isolates. Vaborbactam resulted in variable restoration of meropenem activity as 1 log10 kill was achieved in only 33% and 66% of GES- and KPC-harbouring isolates, respectively, compared with no isolates for meropenem alone.

CONCLUSIONS

Ceftazidime/avibactam and imipenem/relebactam were active against 100% and 89% of KPC- or GES-harbouring isolates tested in vivo. The activity of meropenem/vaborbactam was variable, suggesting this may be an inferior treatment option in this setting. Further studies to evaluate clinical outcomes in GES- and KPC-producing P. aeruginosa are warranted given their increasing prevalence worldwide.

Molecular analysis of metallo-beta-lactamase-producing Pseudomonas aeruginosa in Switzerland 2022-2023

OBJECTIVES

The occurrence of metallo-beta-lactamase-producing Pseudomonas aeruginosa (MBL-PA) isolates is increasing globally, including in Switzerland. The aim of this study was to characterise, phenotypically and genotypically, the MBL-PA isolates submitted to the Swiss National Reference Center for Emerging Antibiotic Resistance (NARA) reference laboratory over a 12-month period from July 2022 to July 2023.

METHODS

Thirty-nine non-duplicate MBL-PA Isolates were submitted to NARA over the study period from across Switzerland. Susceptibility was determined by broth microdilution according to EUCAST methodology. Whole-genome sequencing was performed on 34 isolates. Sequence types (STs) and resistance genes were ascertained using the Centre for Genomic Epidemiology platform. MBL genes, blaNDM-1, blaIMP-1, and blaVIM-2, were cloned into vector pUCP24 and transformed into P. aeruginosa PA14.

RESULTS

The most prevalent MBL types identified in this study were VIM (21/39; 53.8%) followed by NDM (11/39; 28.2%), IMP (6/39; 15.4%), and a single isolate produced both VIM and NDM enzymes. WGS identified 13 different STs types among the 39 isolates. They all exhibited resistance to cephalosporins, carbapenems, and the beta-lactam-beta-lactamase inhibitor combinations, ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam, and meropenem-vaborbactam, and 8 isolates were cefiderocol (FDC) resistant. Recombinant P. aeruginosa strains producing blaNDM-1, blaIMP-1, and blaVIM-2 exhibited FDC MICs of 16, 8, and 1 mg/L, respectively.

CONCLUSIONS

This study showed that the MBL-PA in Switzerland could be attributed to the wide dissemination of high-risk clones that accounted for most isolates in this study. Although FDC resistance was only found in 8 isolates, MBL carriage was shown to be a major contributor to this phenotype.