Global epidemiology and clinical outcomes of carbapenem-resistant Pseudomonas aeruginosa and associated carbapenemases (POP): a prospective cohort study

Genomic insights into the rapid rise of Pseudomonas aeruginosa ST463: A high-risk lineage's adaptive strategy in China

High-risk lineages of Pseudomonas aeruginosa pose a serious threat to public health, causing severe infections with high mortality rates and limited treatment options. The emergence and rapid spread of the high-risk lineage ST463 in China have further exacerbated this issue. However, the basis of its success in China remains unidentified. In this study, we analyzed a comprehensive dataset of ST463 strains from 2000 to 2023 using whole genome sequencing to unravel the epidemiological characteristics, evolutionary trajectory, and antibiotic resistance profiles. Our findings suggest that ST463 likely originated from a single introduction from North America in 2007, followed by widespread domestic dissemination. Since its introduction, the lineage has undergone significant genomic changes, including the acquisition of three unique regions that enhanced its metabolism and adaptability. Frequent recombination events, along with the burden of bacteriophages, antibiotic resistance genes, and the spread of c1-type (blaKPC-2) plasmid-carrying strains, have played crucial roles in its expansion in China. Mutation analysis reveals adaptive responses to antibiotics and selective pressures on key virulence factors, indicating that ST463 is evolving toward a more pathogenic lifestyle.

Aspirin enhances the antibacterial activity of colistin against multidrug-resistant Pseudomonas aeruginosa

Multidrug-resistant (MDR) Pseudomonas aeruginosa (PSA), recently reclassified by the World Health Organization (WHO) as a high-priority antimicrobial-resistant pathogen, continues to impose a substantial global health burden due to escalating resistance and stagnant therapeutic innovation. Colistin retains critical clinical utility against MDR P. aeruginosa infections; however, its dose-limiting nephrotoxicity and neurotoxicity necessitate strategies to optimise therapeutic indices. This study investigated the molecular mechanism underlying the synergistic activity of aspirin in potentiating colistin efficacy against MDR P. aeruginosa. In vitro analyses revealed marked synergistic bactericidal activity (FIC index ≤0.5), with metabolomic profiling demonstrating suppression of key metabolic pathways integral to bacterial membrane biogenesis, including glycerophospholipid metabolism and fatty acid biosynthesis. Ultrastructural imaging confirmed irreversible disruption of membrane integrity via combined treatment. In a rat model of P. aeruginosa-induced pneumonia, colistin-aspirin co-administration demonstrated superior efficacy to monotherapy, significantly reducing pulmonary bacterial load (3 to 4-log CFU/g reduction vs colistin alone; p < 0.01), attenuating histopathological injury, and suppressing pro-inflammatory cytokine levels (IL-6, IL-8, TNF-α) by 30-47%. Critically, this synergy enabled a reduction of colistin dosing to one-sixteenth while maintaining bactericidal potency. These findings provide mechanistic insights into aspirin-mediated colistin sensitisation and evidence supporting combinatorial regimens to circumvent colistin toxicity barriers. This work establishes a rational foundation for clinical translation of repurposed aspirin-colistin therapy against MDR P. aeruginosa infections.

Mortality and exacerbations in bronchiectasis patients with carbapenem-resistant Pseudomonas aeruginosa isolation: a long-term retrospective cohort study

BACKGROUND

Few studies have investigated the impact of carbapenem-resistant Pseudomonas aeruginosa (CRPA) on long-term outcomes in bronchiectasis. This study aimed to analyze acute exacerbations and mortality in bronchiectasis patients with CRPA isolation.

METHODS

This retrospective study included bronchiectasis patients with PA-positive cultures from January 1, 2014, to July 31, 2023, at West China Hospital of Sichuan University. PA was isolated from sputum or bronchoalveolar lavage fluid (BALF) and classified into CRPA and non-CRPA groups based on antimicrobial susceptibility testing. Multivariate logistic regression was used to assess risk factors for acute exacerbations, while multivariate Cox regression identified independent risk factors for all-cause and cause-specific mortality.

RESULTS

Among 564 patients with PA-positive isolates, 143 (25.36%) harbored CRPA strains. CRPA isolation was associated with an increased risk of acute exacerbations (adjusted odds ratio [aOR] 2.072, p = 0.001), while antibiotic treatment reduced the risk of exacerbations (aOR 0.439, p = 0.011). CRPA isolation was an independent risk factor for all-cause (adjusted hazard ratio [aHR] 1.488, p = 0.031) and cause-specific mortality (aHR 1.882, p = 0.010). The 1-, 3-, 5-, and 7-year cause-specific survival rates in the CRPA group were 88.6%, 79.8%, 73.2%, and 68.0%, respectively, versus 95.4%, 91.0%, 85.6%, and 81.8% in the non-CRPA group (p = 0.001).

CONCLUSION

CRPA isolation was significantly associated with an increasing risk of acute exacerbations, overall and cause-specific mortality. These findings underscored the urgent need to strengthen antibiotic stewardship to reduce the emergence of CRPA and to implement early detection and targeted management strategies to improve outcomes for patients with CRPA.

Management of Severe Infections: Multidrug-Resistant and Carbapenem-Resistant Gram-Negative Bacteria

This article provides an overview of the mechanisms behind carbapenem resistance and the antibiotic management for severe infections caused by key carbapenem-resistant gram-negative bacteria, specifically Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa. For Enterobacterales, it highlights the relative advantages of meropenem-vaborbactam and imipenem-relebactam in treating Klebsiella pneumoniae carbapenemase (KPC)-producing strains with resistance to ceftazidime-avibactam, the preference for ceftazidime-avibactam in addressing oxacillin-hydrolyzing carpapenemase (OXA)-48-like -producing organisms, and the combination of ceftazidime-avibactam with aztreonam for metallo-β-lactamase (MBL)-producing Enterobacterales. Regarding A baumannii, sulbactam-durlobactam is identified as the preferred treatment, while ceftolozane-tazobactam, ceftazidime-avibactam, and imipenem-relebactam are viable options for P aeruginosa. Additionally, cefiderocol is presented as an alternative for MBL-producing carbapenem-resistant gram-negative bacteria.

Effectiveness of ceftazidime-avibactam versus ceftolozane-tazobactam for multidrug-resistant Pseudomonas aeruginosa infections in the USA (CACTUS): a multicentre, retrospective, observational study

BACKGROUND

Ceftolozane-tazobactam and ceftazidime-avibactam are preferred treatment options for multidrug-resistant Pseudomonas aeruginosa infections; however, real-world comparative effectiveness studies are scarce. Pharmacokinetic and pharmacodynamic differences between the agents might affect clinical response rates. We aimed to compare the effectiveness of ceftolozane-tazobactam and ceftazidime-avibactam for treatment of invasive multidrug-resistant P aeruginosa infections.

METHODS

This multicentre, retrospective, observational study was conducted at 28 hospitals in the USA between Jan 1, 2016, and Dec 31, 2023. Eligible patients were adults (age ≥18 years old) with microbiologically confirmed multidrug-resistant P aeruginosa pneumonia or bacteraemia treated with ceftolozane-tazobactam or ceftazidime-avibactam for more than 48 h. Patients were matched (1:1) by study site, severity of illness, time to treatment initiation (≤72 h or >72 h), and infection type. The primary outcome was clinical success at day 30, which was defined as survival, resolution of signs and symptoms of infection with the intended treatment course, and the absence of recurrent infection due to P aeruginosa. Secondary outcomes included all-cause mortality and development of resistance to study drug.

FINDINGS

420 eligible patients were included (210 in each treatment group), of whom 350 (83%) had pneumonia and 70 (17%) had bacteraemia. Baseline demographics, comorbidities, and severity of illness indicators were similar between groups. On treatment initiation, 336 (80%) patients were in the intensive care unit, 296 (70%) were receiving mechanical ventilation, and 168 (40%) required vasopressor support. Clinical success was observed in 128 (61%) of 210 patients treated with ceftolozane-tazobactam and 109 (52%) of 210 patients treated with ceftazidime-avibactam. By conditional logistic regression analysis, the adjusted odds ratio (aOR) of success after treatment with ceftolozane-tazobactam compared with ceftazidime-avibactam was 2·07 (95% CI 1·16-3·70). For patients with pneumonia, clinical success was observed in 110 (63%) of 175 patients in the ceftolozane-tazobactam group and 89 (51%) of 175 patients in the ceftazidime-avibactam group (aOR 2·34 [95% CI 1·22-4·47]). Among patients with bacteraemia, rates of clinical success were 51% (18 of 35 patients) for patients treated with ceftolozane-tazobactam and 57% (20 of 35 patients) for those treated with ceftazidime-avibactam (0·76 [0·23-2·57]). There were no significant differences between groups in 30-day or 90-day mortality. Among patients whose baseline isolates were tested for susceptibility, resistance developed in 22% (38 of 173) of patients treated with ceftolozane-tazobactam and 23% (40 of 177) of patients treated with ceftazidime-avibactam.

INTERPRETATION

Treatment with ceftolozane-tazobactam resulted in higher rates of clinical success compared with ceftazidime-avibactam for invasive infections due to multidrug-resistant P aeruginosa. Differences were driven by improved response rates for patients with pneumonia who were treated with ceftolozane-tazobactam. There were no significant differences between study groups with respect to all-cause mortality; treatment-emergent resistance was common with both agents.

FUNDING

Merck Sharp & Dohme.

Evaluation of imipenem-relebactam susceptibility testing in carbapenem resistant Pseudomonas aeruginosa: comparison of sensititre microplates, disc diffusion, and MTS gradient strips with broth microdilution

Four commercial tests EUMDROXF® Sensititre microplates, MTS gradient strips, and disc diffusion were evaluated for imipenem-relebactam susceptibility in 148 ceftazidime and imipenem-resistant Pseudomonas aeruginosa strains, using broth microdilution (BMD) as the reference. EUMDROXF® Sensititre microplates showed the highest accuracy (CA = 93.2%, EA = 93.9%, and bias difference + 21.8%). While the MTS gradient strips showed acceptable performance (CA = 84.5%; EA = 89.9%, and difference of bias = 21.0%), the disc method misclassified 25.8% (16/62) of the resistant strains. Given these results, considering an Area of Technical Uncertainty (ATU) for disc diffusion (20-24 mm) in imipenem-relebactam testing is recommended for P. aeruginosa strains.

Combined impact of biosynthesized selenium nanoparticles and imipenem against carbapenem-resistant Pseudomonas aeruginosa and their associated virulence factors

BACKGROUND

Carbapenem-resistant P. aeruginosa (CRPA) is a significant nosocomial pathogen characterized by extensive antibiotic resistance, representing a serious public health concern. It is regarded as a high-priority target for antibacterial research. This study aimed to isolate and identify CRPA isolates and the biosynthesis of selenium nanoparticles (Se-NPs) as a novel therapeutic approach for combating CRPA strains and their capacity to form biofilms, alone or in combination with imipenem.

METHODS

CRPA isolates were isolated from different clinical samples, identified, and subjected to antibiotic profiling using Vitek-2 method. The detection of biofilm was performed using Congo red agar (CRA), Microdilution broth assay (MBA), and qRT-PCR detection of Bap and ompA genes. Biosynthesis of Se-NPs with a cell-free filter (CFF) of Streptomyces sp. was done and characterized with various techniques, including UV-Vis, XRD, TEM, FTIR, and Zeta potential measurement. The antibacterial efficacy and minimum inhibitory concentrations (MICs) were determined using disc diffusion and microdilution techniques. The checkerboard assay was used to formulate various combinations of imipenem and Se-NPs, alongside time-kill assays to assess their antimicrobial efficacy. Furthermore, the cytotoxic effects and hemolytic activity of Se-NPs, imipenem and their combination were assessed.

RESULTS

The identification process and antibiotic susceptibility testing confirmed that the bacterial isolates were found to be CRPA. Phenotypic analysis revealed that the CRPA produced biofilm, and qRT-PCR demonstrated that all CRPA strains under study have the Bap and ompA genes. The CFF of Streptomyces sp. was able to biosynthesize Se-NPs which presented UV-Visible spectrometric profile with sharp peak at 290 nm. Se-NPs appeared to be a spherical shape, with particle sizes ranging from 20 to 100 nm under TEM and have zeta potential value of -40 mV. The MICs of Se-NPs and imipenem ranged from 6 to 14 and 12 to 14 µg/ml, respectively. The fractional inhibitory concentration index (FICI) values ranged from 0.37 to 0.50 against tested CRPA strain with a significant reduction in the concentrations of Se-NPs and imipenem. QRT-PCR showed that Se-NPs alone or combination of Se-NPs and imipenem led to a reduction of Bap and ompA gene expression compared to control (p ≤ 0.0001). The study showed a significant difference in cell viability was observed across normal or cancer cell lines at high concentrations. However, the combination of Se-NPs and imipenem demonstrated enhanced selectivity toward cancer cells, with HepG-2 cells showing significantly lower viability compared to normal HFP-4 cells across all tested concentrations. Se-NPs alone showed moderate hemolysis percentages of 1.9% at 12 h and 2.3% at 24 h while the hemolytic activity Se-NPs and imipenem combination was reduced to 1.4% and 1.7% at 12 and 24 h, representing approximately 26% and 26% reductions in haemolysis compared to Se-NPs alone at the respective time points.

CONCLUSION

This study confirms that the biosynthesized Se-NPs exhibit potent synergistic effects with imipenem against CRPA, significantly reducing biofilm formation and the expression of virulence genes Bap and ompA.

Diagnostic algorithm for the detection of carbapenemases and extended-spectrum β-lactamases in carbapenem-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa can acquire carbapenem resistance through various mechanisms, including genomic mutations leading to the overexpression of efflux pumps, intrinsic AmpC-β-lactamase, and/or reduced permeability, and/or through the acquisition of plasmid-mediated carbapenemases and/or extended-spectrum-β-lactamases (ESBLs). Unfortunately, carbapenemase/ESBL-producing-carbapenem-resistant-P. aeruginosa (CP/ESBL-CRPA) cannot be differentiated from non-CP/ESBL-CRPA based solely on susceptibility testing results of conventional β-lactam (BL)-antibiotics. Knowing that these two groups display different activity profiles toward novel BL/β-lactamase-inhibitor (BLI) combinations, we developed and verified a cost-effective and easy-to-use diagnostic algorithm for screening and differentiation of carbapenemase and ESBL production in CRPA. We determined disc diffusion inhibition zones and gradient strip minimal inhibitory concentration values of 136 whole-genome-sequenced CRPA (70 metallo-β-lactamase-[MBL-], 1 GES-5-, 1 KPC-2-, 12 ESBL-, and 53 AmpC-hyper-producing isolates). We used the following BL-BLI combinations: ceftolozane-tazobactam (C-T), ceftazidime-avibactam, imipenem-relebactam (I-R), meropenem-vaborbactam, cefepime-enmetazobactam (C-E), and aztreonam-avibactam. We also included a lateral flow immunoassay (Carba-5, NG-Biotech) for confirmation of MBL production and double disc synergy testing (DDST) to improve ESBL detection. C-T was the most effective screening antibiotic for distinguishing MBL and ESBL producers from AmpC-hyperproducing CRPA, achieving a sensitivity of 100% for both MBL and ESBL producers. I-R reliably confirmed MBL production in C-T positive screened CRPAs, with a sensitivity of 92.8% and specificity of 100%. Incorporating Carba-5 into the phenotypic algorithm improved sensitivity for confirming MBL production to 100%. For the remaining C-T positive but I-R negative isolates, C-E showed 75% sensitivity and 78.6% specificity in detecting ESBL production. The DDST further confirmed ESBL production in six out of nine ESBL producers (66.6%). In conclusion, we established a simple and cost-effective diagnostic algorithm, enabling screening and confirmation of carbapenemase and ESBL production in CRPA.IMPORTANCECarbapenem-resistant Pseudomonas aeruginosa (CRPA) is a major global health threat, and rapid identification of its resistance mechanisms is crucial for effective treatment and infection control. Differentiating between carbapenemase-producing (CP), extended-spectrum β-lactamase-producing (ESBL), and AmpC-hyperproducing CRPA is challenging, as conventional susceptibility testing cannot reliably distinguish these resistance mechanisms. Our study presents a simple, cost-effective, and easy-to-implement phenotypic diagnostic algorithm that enables accurate screening and confirmation of CP and ESBL production in CRPA. This method is particularly valuable for laboratories lacking access to molecular diagnostics, as it provides a practical alternative for routine testing. By facilitating the early detection of resistant P. aeruginosa strains, this approach has the potential to improve patient outcomes, optimize antimicrobial therapy, and enhance global surveillance efforts against multidrug-resistant pathogens.

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.

Genomic epidemiology and characterization of difficult-to-treat resistant Pseudomonas aeruginosa isolates co-harboring blaOXA-50 and crpP causing bronchiectasis

Difficult-to-treat resistant Pseudomonas aeruginosa (DTR-PA) is an MDR subset resistant to all first-line antipseudomonal agents. It is particularly concerning in respiratory infections like bronchiectasis, leading to poor outcomes, limited treatment options, and higher healthcare costs. This study aimed to investigate the antimicrobial resistance profiles and sequence types (STs) of Pseudomonas aeruginosa isolates, providing insight into their resistance patterns and the factors contributing to resistance. In 2021, 38 multidrug-resistant P. aeruginosa isolates were collected from bronchiectasis patients from a single medical center in Ningbo, China. The isolates were obtained from various clinical samples, including sputum, secretion, urine, and blood. Minimum inhibitory concentration testing revealed that 97.4% of the isolates were sensitive to amikacin and tobramycin, with none showing resistance to polymyxin B. Resistance rates to imipenem and meropenem were 84.2% and 57.9%, respectively, with 44.7% of isolates classified as DTR-PA. Multilocus sequence typing identified ST277 (18.4%), ST1076 (13.2%), and ST3012 (13.2%) as the predominant DTR-PA sequence types. The presence of blaPAO, aph(3')-IIb, and catB7, in all isolates and blaOXA-50 (16 isolates) and crpP genes (24 isolates) in coexisitance in 11 of 16 isolates, suggested a strong association with the DTR phenotype. Phylogenetic analysis grouped DTR-PA isolates into distinct evolutionary lineages (II and III), underscoring their genetic relatedness and potential for clonal spread. Our findings suggest that co-harboring blaOXA-50 and crpP contributes to the development of DTR-PA, highlighting the need for continuous monitoring of these resistance determinants. While the study provides important insights into antimicrobial resistance in DTR-PA, further research is needed to explore resistance development across different infection sites and clinical settings.

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.

Clinical outcomes and pharmacokinetics/pharmacodynamics of intravenous polymyxin B treatment for various site carbapenem-resistant gram-negative bacterial infections: a prospective observational multicenter study

Polymyxin B, a last resort for carbapenem-resistant gram-negative bacteria (CRGNB) infections, has infection site-specific pharmacokinetic/pharmacodynamic (PK/PD) properties. However, there is little clinical evidence to support optimal exposures of polymyxin B for different site infections. We performed a prospective, observational, multicenter study to evaluate the clinical outcomes and PK/PD of intravenous polymyxin B treatment for various site CRGNB infections. The main clinical outcomes were 14-day all-cause mortality and nephrotoxicity, and the secondary outcomes were 28-day mortality and clinical response. The area under curves (AUCs) of polymyxin B were determined, and their associations with clinical outcomes were analyzed by stratification based on the infection site. A total of 312 patients were ultimately enrolled from 10 research centers. The overall 14-day mortality was 29.5%, and those of patients with lower respiratory tract infection (LRTI), intra-abdominal infection (IAI), and bloodstream infection (BSI) were 32.3%, 19.7%, and 30.3%, respectively. The 28-day mortality rate was 38.1%, while LRTI patients had the highest mortality (41.4%) and IAI patients lowest (34.8%). The clinical response rate was 46.2%, which was similar among the subgroups. The overall AKI rate was 60.9%. An AUC greater than 50 mg∙h/L was related to lower mortality in IAI patients but not in LRTI patients, which led to a lower but not significant difference in the overall analysis. The AUC of polymyxin B was an independent risk factor for 14-day mortality in IAI patients, and the cutoff value was 76 mg∙h/L. The results would be helpful for personalized dosing and monitoring of polymyxin B.CLINICAL TRIALSThis study is registered with the Chinese Clinical Trial Registry as ChiCTR2200056667.

Real-World Applications of Imipenem-Cilastatin-Relebactam: Insights From a Multicenter Observational Cohort Study

Background

Multidrug-resistant (MDR) gram-negative infections are a substantial threat to patients and public health. Imipenem-cilastatin-relebactam (IMI/REL) is a β-lactam/β-lactamase inhibitor with expanded activity against MDR Pseudomonas aeruginosa and carbapenem-resistant Enterobacterales. This study aims to describe the patient characteristics, prescribing patterns, and clinical outcomes associated with IMI/REL.

Methods

This was a retrospective, multicenter, observational study of patients ≥18 years old who received IMI/REL for ≥48 hours for a suspected or confirmed gram-negative infection. The primary outcome was clinical success, defined as improvement or resolution of infection-related signs or symptoms while receiving IMI/REL and the absence of 30-day microbiologic failure. Multivariable logistic regression analysis was performed to identify independent predictors of clinical success.

Results

The study included 151 patients from 24 US medical centers. IMI/REL was predominantly prescribed for lower respiratory tract infections, accounting for 52.3% of cases. Most patients were infected with a carbapenem-nonsusceptible pathogen (85.4%); P aeruginosa was frequently targeted (72.2%). Clinical success was achieved in 70.2% of patients. Heart failure, receipt of antibiotics within the past 90 days, intensive care unit admission at time of index culture collection, and isolation of difficult-to-treat resistant P aeruginosa were independently associated with a reduced odds of clinical success. Adverse events were reported in 6.0% of patients, leading to discontinuation of IMI/REL in 3 instances.

Conclusions

This study provides a comprehensive analysis of the real-world effectiveness and safety of IMI/REL. Comparative studies and investigations of specific subgroups will further enhance our understanding of IMI/REL in treating MDR infections.

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.

Molecular epidemiology and patient outcome of carbapenem-resistant Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii in Japan: a multicenter study from MultiDrug-Resistant organisms clinical research network

Background and objectives

Carbapenem-resistant Gram-negative bacilli (CRGNB), especially Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii, are critical pathogens associated with excess morbidity and mortality. To elucidate their molecular epidemiology and clinical outcomes in Japan, patients with CRGNB were enrolled in the MDR organisms clinical research network (MDRnet) consisting of eight tertiary care facilities.

Methods

Between 2019 and 2022, 246 unique patients with carbapenem-resistant Enterobacterales (CRE), carbapenem-resistant P. aeruginosa (CRPA) and carbapenem-resistant A. baumannii (CRAB) isolates were prospectively enrolled.

Results

A total of 246 isolates were collected from 246 patients, including 78 (31.7%) CRE, 167 (67.9%) CRPA and 1 (0.4%) CRAB. For CRE, 74.4% of the isolates carried carbapenemase genes with predominance of bla IMP (64.1%). Only 2.4% of CRPA had carbapenemase genes, which was lower than CRE. Among the infected patients, 20.0% and 12.5% died of CRE and CRPA within 30 days, respectively. In patients with CRE, the mortality rate within 30 days for those without carbapenemase-producing Enterobacterales (CPE) was higher compared with those with CPE (22.2% compared with 18.8%).

Conclusions

Our study highlights the unique molecular epidemiology and clinical outcomes of CRGNB in Japan.

Carbapenem-Resistant Pseudomonas aeruginosa's Resistome: Pan-Genomic Plasticity, the Impact of Transposable Elements and Jumping Genes

Pseudomonas aeruginosa, a Gram-negative, motile bacterium, may cause significant infections in both community and hospital settings, leading to substantial morbidity and mortality. This opportunistic pathogen can thrive in various environments, making it a public health concern worldwide. P. aeruginosa's genomic pool is highly dynamic and diverse, with a pan-genome size ranging from 5.5 to 7.76 Mbp. This versatility arises from its ability to acquire genes through horizontal gene transfer (HGT) via different genetic elements (GEs), such as mobile genetic elements (MGEs). These MGEs, collectively known as the mobilome, facilitate the spread of genes encoding resistance to antimicrobials (ARGs), resistance to heavy metals (HMRGs), virulence (VGs), and metabolic functions (MGs). Of particular concern are the acquired carbapenemase genes (ACGs) and other β-lactamase genes, such as classes A, B [metallo-β-lactamases (MBLs)], and D carbapenemases, which can lead to increased antimicrobial resistance. This review emphasizes the importance of the mobilome in understanding antimicrobial resistance in P. aeruginosa.

Rapid prediction of carbapenemases in Pseudomonas aeruginosa by imipenem/relebactam and MALDI-TOF MS

Pseudomonas aeruginosa is a major nosocomial pathogen commonly involved in multidrug-resistant (MDR) infections that are very difficult to treat. Imipenem/relebactam is a new carbapenem/β-lactamase inhibitor combination with robust activity against P. aeruginosa. However, resistance is increasingly reported, and rapid detection is, therefore, crucial so that appropriate treatments can be prescribed. We have developed a rapid MALDI TOF-MS-based method that can accurately predict the presence of carbapenemases in P. aeruginosa using imipenem/relebactam. The method was developed using a retrospective and a prospective collection of 419 P. aeruginosa isolates (including recombinant isolates and WGS-characterized clinical strains) encompassing the most important β-lactam resistance mechanisms. The MALDI TOF-MS method is based on the detection of the hydrolysis of imipenem in the presence or absence of relebactam, measuring modifications in the mass spectra of imipenem after incubation with bacteria. The method was evaluated against a retrospective collection and then validated against 250 prospectively collected clinical isolates, showing a 98% (246/250) agreement between the phenotype and the MALDI-TOF MS hydrolysis result and a 100% accordance with the β-lactam resistance genotype. Some errors in detecting GES-producing isolates and in detecting different mutational resistance mechanisms associated with imipenem/relebactam resistance (MICs ranging from 4 to 8 mg/L) were observed. All results were obtained within 1 hour, positioning the MALDI-TOF-based test as a rapid and easy-to-perform method for detection of carbapenemases (except GES enzymes) in P. aeruginosa. Besides, implementation of the method in routine laboratory screening would facilitate the correct use of imipenem/relebactam to treat P. aeruginosa infections.IMPORTANCEWhile several rapid diagnostic methods have been developed for the detection of ESBLs and carbapenemases to improve treatment decision-making in Enterobacterales, there is a lack of approaches to rapidly identify resistance mechanisms and predict β-lactam susceptibility in Pseudomonas aeruginosa. Taking advantage of the mechanism of action and the high efficacy of the newly developed β-lactam/β-lactamase inhibitor combination imipenem/relebactam against P. aeruginosa, we developed a WGS-guided, MALDI-TOF-based algorithm that accurately predicts the presence of carbapenemase enzymes in this bacterium and aids in forecasting the imipenem/relebactam susceptibility profile. The implementation of this method in routine laboratory testing would provide significant support in the rapid decision-making for the use of imipenem/relebactam in severe P. aeruginosa infections.

Emerging resistance mechanisms to newer β-lactams in Pseudomonas aeruginosa

BACKGROUND

Although the introduction of novel β-lactams and/or combinations with β-lactamase inhibitors over the last decade is helping to mitigate the threat of extensively drug-resistant/difficult-to-treat-resistant (XDR/DTR) Pseudomonas aeruginosa infections, the problem is far from being solved, due to the capacity of this pathogen for developing resistance.

OBJECTIVES

This study aims to provide a comprehensive analysis of the emerging/evolving resistance mechanisms to the antipseudomonal β-lactams introduced over the last decade.

SOURCES

Sources include literature review of published studies before December 31 2024 analysing P. aeruginosa resistance mechanisms for ceftolozane/tazobactam, ceftazidime/avibactam, cefiderocol, imipenem/relebactam, meropenem/vaborbactam, and/ aztreonam/avibactam.

CONTENT

Among the emerging resistance mechanisms are noteworthy the mutations in the catalytic centres (mostly the Ω-loop) of AmpC, the horizontally acquired OXA-2/OXA-10 enzymes or of the class A carbapenemases (GES/KPC). These mutations typically confer ceftolozane/tazobactam and ceftazidime/avibacm resistance. They also frequently increase cefiderocol Minimal Inhibitory Concentrations (MICs), and some of them, such as the L320P AmpC mutation, affect cefiderocol specifically. However, most of these mutations confer collateral susceptibility to carbapenems. Efflux pumps are also relevant, given their capacity to extrude both, the β-lactam and their partner β-lactamase inhibitor. Moreover, beyond the classical mutational overexpression of efflux pumps, emerging resistance is driven by the selection of structural mutations leading to modified (enhanced) substrate recognition. Other emerging mechanisms include β-lactam target mutations (particularly Penicillin-binding protein 3 (PBP3)), large genomic deletions, the activation of two-component regulators (such as ParRS or CpxRS) or the mutations in iron transport systems (such as Piu or Pir) involved in cefiderocol resistance.

IMPLICATIONS

A deep understanding of emerging resistance mechanisms, including their conferred cross-resistances and collateral susceptibilities, should be useful for the optimization of treatments of severe XDR/DTR P. aeruginosa infections.

Companions in antimicrobial resistance: examining transmission of common antimicrobial-resistant organisms between people and their dogs, cats, and horses

SUMMARYNumerous questions persist regarding the role of companion animals as potential reservoirs of antimicrobial-resistant organisms that can infect humans. While relative antimicrobial usage in companion animals is lower than that in humans, certain antimicrobial-resistant pathogens have comparable colonization rates in companion animals and their human counterparts, which inevitably raises questions regarding potential antimicrobial resistance (AMR) transmission. Furthermore, the close contact between pets and their owners, as well as pets, veterinary professionals, and the veterinary clinic environment, provides ample opportunity for zoonotic transmission of antimicrobial-resistant pathogens. Here we summarize what is known about the transmission of AMR and select antimicrobial-resistant organisms between companion animals (primarily dogs, cats, and horses) and humans. We also describe the global distribution of selected antimicrobial-resistant organisms in companion animals. The impact of interspecies AMR transmission within households and veterinary care settings is critically reviewed and discussed in the context of methicillin-resistant staphylococci, extended-spectrum β-lactamase and carbapenemase-producing bacteria. Key research areas are emphasized within established global action plans on AMR, offering valuable insights for shaping future research and surveillance initiatives.

Spatial transcriptomics identifies novel Pseudomonas aeruginosa virulence factors

To examine host-pathogen interactions, we leveraged a dual spatial transcriptomics approach that simultaneously captures the expression of Pseudomonas aeruginosa genes alongside the entire host transcriptome using a murine model of ocular infection. This method revealed differential pathogen- and host-specific gene expression patterns in infected corneas, which generated a unified transcriptional map of infection. By integrating these data, we developed a predictive ridge regression model trained on images from infected tissues. The model achieved an R2 score of 0.923 in predicting bacterial burden distributions and identifying novel biomarkers associated with disease severity. Among iron acquisition pathogen-specific gene transcripts that showed significant enrichment at the host-pathogen interface, we discovered the novel virulence mediator PA2590, which was required for bacterial virulence. This study therefore highlights the power of combining bacterial and host spatial transcriptomics to uncover complex host-pathogen interactions and identify potentially druggable targets.

β-Lactamase diversity in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a clinically important Gram-negative pathogen responsible for a wide variety of serious nosocomial and community-acquired infections. Antibiotic resistance is a major concern, as this organism has a wide variety of resistance mechanisms, including chromosomal class C (blaPDC) and D (blaOXA-50 family) β-lactamases, efflux pumps, porin channels, and the ability to readily acquire additional β-lactamases. Surveillance studies can reveal the diversity and distribution of β-lactamase alleles but are difficult and expensive to conduct. Herein, we apply a novel approach, using publicly available data derived from whole genome sequences, to explore the diversity and distribution of β-lactamase alleles across 30,452 P. aeruginosa isolates. The most common alleles were blaPDC-3, blaPDC-5, blaPDC-8, blaOXA-488, blaOXA-50, and blaOXA-486. Interestingly, only 43.6% of assigned blaPDC alleles were encountered, and the 10 most common blaPDC and intrinsic blaOXA alleles represent approximately 75% of their respective total alleles, while many other assigned alleles were extremely uncommon. As anticipated, differences were observed over time and geography. Surprisingly, more distinct unassigned alleles were encountered than distinct assigned alleles. Understanding the diversity and distribution of β-lactamase alleles helps to prioritize variants for further research, select targets for drug development, and may aid in selecting therapies for a given infection.

Evaluation of two gradient diffusion tests to determine susceptibility to aztreonam and ceftazidime-avibactam in combination

The combination of aztreonam and ceftazidime-avibactam (ATM-CZA) is a last resort regimen against recalcitrant infections caused by metallo-β-lactamase (MBL)-producing organisms. Susceptibility testing is warranted due to emerging resistance to the combination, but there are no widely implemented methods for use in clinical laboratories. Here, we used a cohort of 100 Enterobacterales, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia strains, including 68 MBL producers, to evaluate the performance of two ETEST strip-based synergy testing methods: the side-by-side (SS) method with an ATM ETEST placed next to a CZA ETEST (10 mm apart) and the strip cross (SX) method with a CZA ETEST placed perpendicularly on top of the ATM ETEST (at the 8 µg/mL mark). By reference broth microdilution (BMD), 89.1% (41/46) of the Enterobacterales, 15% (3/20) of the P. aeruginosa, and 97.1% (33/34) of the S. maltophilia isolates tested susceptible to the ATM-CZA combination. The SS method yielded 72% categorical agreement with BMD and 28 major errors (ME, 36.4%). Initial testing with the SX method yielded three ME , of which one was resolved upon repeat testing, yielding a final categorical agreement of 98% with BMD with two ME (2.6%). The SX method also yielded 100% reproducibility across three brands of Mueller Hinton agar (BD, Hardy, Remel). Our study demonstrates that the SX method is accurate, precise, and feasible for clinical laboratories to perform ATM-CZA susceptibility testing to guide use of the combination for treatment of multidrug-resistant gram-negative pathogens.

Synergistic effects of colistin-rifampin-based triple antimicrobial combination therapy against Carbapenem-resistant Pseudomonas aeruginosa: a time-kill assay

BACKGROUND

Our research aimed to investigate the potential of in vitro triple antimicrobial synergism against carbapenem-resistant Pseudomonas aeruginosa (CRPA) as a strategy to overcome antimicrobial resistance.

METHODS

We used 12 CRPA blood isolates stocked in the Asian Bacterial Bank between 2016 and 2018. All isolates were tested by multi-locus sequencing and carbapenemase multiplex PCR. To assess the antimicrobial interactions, we performed time-kill assays using double or triple combination regimens. These regimens included CST and/or rifampin combined with IPM, MEM, or CZA. The assay was conducted at 1× and 0.5× MICs.

RESULTS

Among the 12 CRPA isolates, nine produced metallo-beta-lactamases (6 IMP-6, 2 VIM-2 and 1 NDM-1). In the time-kill assay, the median viable bacterial count for CST-rifampin was the lowest among double combinations after 24 h incubation (2.25 log cfu/mL at 1× MIC and 3.71 log cfu/mL at 0.5× MIC). In contrast, all triple combinations achieved 0 log cfu/mL at both 1× MIC and 0.5× MIC. Compared with CST-rifampin (synergism: 25% at 1× MIC, 42% at 0.5× MIC; bactericidal: 50% at 1× MIC, 42% at 0.5× MIC), all triple combinations showed greater synergism and bactericidal activity at both 1× MIC (50%-75% for synergism, 75%-83% for bactericidal activity) and 0.5× MIC (58%-75% for both).

CONCLUSIONS

Our findings suggest that CST-rifampin-based triple antimicrobial combinations exhibit greater synergy and bactericidal activity in eradicating CRPA compared with double antimicrobial combinations.

World Health Organization priority antimicrobial resistance in Enterobacterales, Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecium healthcare-associated bloodstream infections in Brazil (ASCENSION): a prospective, multicentre, observational study

Background

Carbapenem-resistant Enterobacterales (CRE), Acinetobacter baumannii (CRAB), Pseudomonas aeruginosa (CRPA), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE) are listed by World Health Organization (WHO) as priority antimicrobial-resistant bacteria. Data on WHO Priority Antimicrobial resistance Phenotype (WPAP) bacteria from low- and middle-income countries are scarce. In this study, we investigated the occurrence of WPAP in healthcare-associated bloodstream infections (BSI) in Brazil, an upper-middle-income country in South America.

Methods

ASCENSION was a prospective, multicentre, observational study conducted in 14 hospitals from four of five Brazilian regions. Enterobacterales, A. baumannii, P. aeruginosa, S. aureus and E. faecium BSIs in hospitalised patients were analysed. The primary outcome was the frequency of WPAP among all bacteria of interest. Secondary outcomes were incidence-density of bacteria isolates in hospitalised patients, WPAP proportions within bacterial species, and 28-day mortality. PCR for carbapenemase genes was performed in carbapenem-resistant Gram-negative bacteria.

Findings

Between August 15, 2022, and August 14, 2023, 1350 isolates (1220 BSI episodes) were included. WPAP accounted for 38.8% (n = 524; 95% Confidence Interval 32.0-46.1) of all isolates, with CRE (19.3%) as the most frequent, followed by CRAB (9.6%), MRSA (4.9%), VRE (2.7%), and CRPA (2.4%). Incidence-density of all and WPAP isolates were 1.91 and 0.77/1000 patients-day, respectively. Carbapenem-resistant Klebsiella pneumoniae (CRKP) was the most common CRE, corresponding to 14.2% of all BSIs. A. baumannii isolates presented the highest proportion of WPAP (87.8%). Mortality rates were higher in patients with BSIs by WPAP than non-WPAP isolates. KPC (64.4%) was the predominant carbapenemase in CRE, followed by NDM (28.4%) and KPC + NDM co-production (7.1%). OXA-23 was the most frequent in CRAB.

Interpretation

A high frequency of WPAP bacteria, particularly CRKP and CRAB, were found in healthcare-associated BSIs in Brazil, posing them as a major public health problem in this country.

Funding

National Council for Scientific and Technological Development, Brazil.

An unignorable human health risk posed by antibiotic resistome and microbiome in urban rivers: Insights from Beijing, China

Urban rivers are the main water bodies humans frequently come into contact with, so the risks posed are closely monitored. Antibiotic resistance genes (ARGs) residues in reclaimed water pose serious risks to human health. There are urgent needs to improve the understanding of distribution of and risks posed by ARGs in urban rivers. In this study, shotgun metagenomic approach was used to characterize ARGs, mobile genetic elements (MGEs), and virulence factors (VFs) in water and sediment from Xinfeng River in Beijing and to identify microbes, potential antibiotic resistant bacteria, and human pathogens (HPs). MGE, microbial community, VF, and ARG co-occurrences were used to assess the environmental risks posed by ARGs. The results indicated that quinolone was the most abundant ARG type and that tufA and fusA were the two dominant ARG subtypes. Wetland effluent increased ARG abundance in the river, and the effect was detected even 50 m downstream. ARG abundances and distribution in the river had difference in different seasons. The dominant bacteria in the river were Proteobacteria, Bacteroidetes, and Actinobacteria, and 59 HPs were detected. In total, 69 MGEs and 19 VFs were found. Co-occurrence networks indicated that potential antibiotic resistant bacteria, MGEs, VFs, and ARGs in the river significantly correlated, indicating the potential risks posed by ARGs. The results improve our understanding of ARG distribution and environmental risks in urban river water. More attention should be paid to controlling environmental risks posed by ARGs in urban river and reclaimed water.

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.

Difficult-to-Treat Pseudomonas aeruginosa Infections in Critically Ill Patients: A Comprehensive Review and Treatment Proposal

The management of infections caused by difficult-to-treat Pseudomonas aeruginosa in critically ill patients poses a significant challenge. Optimal antibiotic therapy is crucial for patient prognosis, yet the numerous resistance mechanisms of P. aeruginosa, which may even combine, complicate the selection of an appropriate antibiotic. In this review, we examine the epidemiology, resistance mechanisms, risk factors, and available and future therapeutic options, as well as strategies for treatment optimization. Finally, we propose a treatment algorithm to facilitate decision making based on the resistance patterns specific to each Intensive Care Unit.

Time to positivity as a predictor of catheter-related bacteremia and mortality in adults with Pseudomonas aeruginosa bloodstream infection

BACKGROUND

Time to positivity (TTP) and differential TTP (DTP) emerge as diagnostic and prognostic tools for bloodstream infections (BSI) though specific cut-off values need to be determined for each pathogen. Pseudomonas aeruginosa BSI (PAE-BSI) is of critical concern, particularly in immunocompromised patients, due to high mortality rates. Catheter-related infections are a common cause, necessitating rapid and accurate diagnostic tools for effective management (source-control).

METHODS

Unicentric retrospective observational study analyzing the diagnostic utility and best cut-off values of time to positivity (TTP) and differential time to positivity (DTP) to identify catheter-related PAE-BSI and the association of TTP with 30-day mortality.

RESULTS

1177 PAE-BSI cases TTP were included in the study. TTP was available in all episodes whereas DTP was available in 355 episodes. Breakthrough bacteremia disregarding the TTP, more than one positive blood culture or > 7 days with a catheter in place and both a TTP < 13h and a DTP > 2h were independently associated to catheter-related PAE-BSI. Secondly, lower TTP were significantly associated with higher 30-day mortality rates in both catheter-related and non-catheter-related PAE-BSI. For catheter-related infections, TTP < 14h exacerbated mortality among patients among patients in whom the catheter was not removed within 48h (OR 2.9[1.04-8]); whereas for other sources TTP < 16h increased mortality (OR 1.6[1.1-2.4]) particularly when the empiric antibiotic therapy was not active (OR 3.8[1.5-10]).

CONCLUSION

These findings advocate for the routine use of TTP over DTP as a diagnostic tool to guide timely interventions such as catheter removal, thereby potentially improving patient outcomes in PAE-BSI. Moreover, lower TTP have also prognostic implications in both catheter-related and non-catheter-related infections.

Pseudomonas aeruginosa: One Health approach to deciphering hidden relationships in Northern Portugal

AIMS

Antimicrobial resistance in Pseudomonas aeruginosa represents a major global challenge in public and veterinary health, particularly from a One Health perspective. This study aimed to investigate antimicrobial resistance, the presence of virulence genes, and the genetic diversity of P. aeruginosa isolates from diverse sources.

METHODS AND RESULTS

The study utilized antimicrobial susceptibility testing, genomic analysis for resistance and virulence genes, and multilocus sequence typing to characterize a total of 737 P. aeruginosa isolates that were collected from humans, domestic animals, and aquatic environments in Northern Portugal. Antimicrobial resistance profiles were analyzed, and genomic approaches were employed to detect resistance and virulence genes. The study found a high prevalence of multidrug-resistant isolates, including high-risk clones such as ST244 and ST446, particularly in hospital sources and wastewater treatment plants. Key genes associated with resistance and virulence, including efflux pumps (e.g. MexA and MexB) and secretion systems (T3SS and T6SS), were identified.

CONCLUSIONS

This work highlights the intricate dynamics of multidrug-resistant P. aeruginosa across interconnected ecosystems in Northern Portugal. It underscores the importance of genomic studies in revealing the mechanisms of resistance and virulence, contributing to the broader understanding of resistance dynamics and informing future mitigation strategies.

Carbapenem resistance in the Dominican Republic: clinical characteristics, genotypic profiles, and risk factors

Objective

To characterize the clinical and microbiological features of carbapenem-resistant Enterobacterales (CRE) compared to carbapenem-susceptible Enterobacterales (CSE) in the Dominican Republic (DR), and to assess risk factors associated with CRE.

Design

Retrospective case-control study.

Setting

Hospital General Plaza de la Salud, a tertiary teaching hospital in Santo Domingo, DR, from January 2015 to June 2024.

Patients

Patients with CRE infections were identified from microbiology records. For each year, a matched group of CSE cases was selected at a 2.5:1 ratio. A total of 101 CRE cases and 280 CSE cases were included.

Methods

Data were collected on demographics, comorbidities, infection sources, hospital stay duration, antibiotic use, and microbiology results. Statistical analysis included univariate and multivariate logistic regression to identify independent risk factors for CRE.

Results

CRE cases showed higher prevalence of Enterobacter (36.5%) and Klebsiella (38.5%), while Escherichia predominated in CSE (65.5%). CRE patients had longer hospital stays (mean 18.7 vs 4.6 days, P < 0.001), higher ICU admission rates (34.7% vs 3.6%, P < 0.001), and increased invasive procedure use (eg central venous catheters, 36.6% vs 5.4%, P < 0.001). Key risk factors included antibiotic use (OR 3.09, P < 0.001) and ICU stay (OR 3.60, P= 0.012). The peak CRE resistance rate was 3.47% in 2022, a 64% increase from pre-pandemic levels.

Conclusions

CRE infections in the DR increased during the COVID-19 pandemic, associated with prolonged hospitalizations and critical care. Enhanced antimicrobial stewardship is essential to curb resistance.

Multidrug-resistant Gram-negative bacterial infections

Multidrug-resistant Gram-negative bacterial infections cause significant morbidity and mortality globally. These pathogens easily acquire antimicrobial resistance (AMR), further highlighting their clinical significance. Third-generation cephalosporin-resistant and carbapenem-resistant Enterobacterales (eg, Escherichia coli and Klebsiella spp), multidrug-resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii are the most problematic and have been identified as priority pathogens. In response, several new diagnostic technologies aimed at rapidly detecting AMR have been developed, including biochemical, molecular, genomic, and proteomic techniques. The last decade has also seen the licensing of multiple antibiotics that have changed the treatment landscape for these challenging infections.

Global phylogeography and genetic characterization of carbapenem and ceftazidime-avibactam resistant KPC-33-producing Pseudomonas aeruginosa

Ceftazidime-avibactam (CZA) is currently one of the last resorts used to treat infections caused by carbapenem-resistant Enterobacteriaceae and Pseudomonas aeruginosa. However, KPC variants have become the main mechanism mediating CZA resistance in KPC-producing gram-negative bacteria after increasing the application of CZA. Our previous study revealed that CZA-resistant KPC-33 had emerged in carbapenem-resistant P. aeruginosa (CRPA) and had resulted in death due to hypervirulence and extensive drug resistance; however, the evolutionary path of KPC-33-producing CRPA has not been investigated. Here, we observed the emergence of blaKPC-33 in CRPA under drug pressure, leading to resistance to CZA. We further elucidated the pathway of resistance development due to blaKPC mutations in P. aeruginosa. Three KPC-producing P. aeruginosa (KPC-PA) strains (including one blaKPC-33-positive strain and two blaKPC-2-positive strains) were successively isolated from a hospitalized patient. The blaKPC-33-positive CZA-resistant strain SRPA0656 (CZA MIC >128 μg/mL, imipenem MIC = 32 μg/mL) was isolated after the blaKPC-2-positive P. aeruginosa SRP2863 (CZA MIC = 1 μg/mL, imipenem MIC >128 μg/mL) was treated with CZA. The subsequent use of carbapenems to treat the infection led to the re-emergence of the KPC-2-producing strain SRPA3703. Additionally, we collected four other KPC-33-producing P. aeruginosa strains. Antimicrobial susceptibility testing revealed that all the KPC-33-bearing P. aeruginosa strains in this study were multidrug-resistant but susceptible to colistin and amikacin. Whole-genome sequencing indicated that blaKPC-33 was located on two Tn4401-like transposons contained in the plasmids and that most of these plasmids could be transferred into P. aeruginosa PAO1Rif isolates. Growth rate determination demonstrated that the relative growth rate of P. aeruginosa harboring blaKPC-33 was faster than that of P. aeruginosa harboring blaKPC-2 in the logarithmic phase. Global phylogenetic analysis revealed that most KPC-PA strains were isolated from China and the USA. MLST revealed that the most common ST in KPC-PA was ST463, which was detected only in China, and that all the strains carried blaKPC-2 or its derivatives. These results indicated that the use of CZA for the treatment of KPC-2-producing P. aeruginosa may have contributed to the evolution of KPC-33. The widespread dissemination of KPC-PA (especially the ST463) and Tn4401 transposons may increase the spread of CRPA isolates carrying blaKPC-33. Close attention to the development of resistance to CZA during clinical treatment of CRPA infection and monitoring CZA-resistant strains is necessary to prevent further spread.

Antibiotic resistance genotype, phenotype, and clinical outcomes in patients with Gram-negative infections at Rabin Medical Center in Israel

Antibiotic resistance is a major cause of morbidity and mortality. However, a better understanding of the relationship between bacterial genetic markers, phenotypic resistance, and clinical outcomes is needed. We performed whole-genome sequencing on five medically important pathogens (Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) to investigate how resistance genes impact patient outcomes. A total of 168 isolates from 162 patients with Gram-negative infections admitted to Beilinson Hospital at Rabin Medical Center in Israel were included for final analysis. Genomes were analyzed for resistance determinants and correlated with microbiologic and clinical data. Thirty-day mortality from time of culture was 26.5% (43/162). Twenty-nine patients had carbapenem-resistant isolates (29/168, 17.2%), while 63 patients had multidrug-resistant isolates (63/168, 37.5%). Albumin levels were inversely associated with mortality and length of stay, while arrival from a healthcare facility and cancer chemotherapy predicted having a multidrug-resistant isolate. Sequencing revealed possible patient-to-patient transmission events. blaCTX-M-15 was associated with multidrug-resistance in E. coli (OR = 3.888, P = 0.023) on multivariate analysis. Increased blaOXA-72 copy number was associated with carbapenem-resistance in A. baumannii (P = 0.003) and meropenem minimum inhibitory concentration (P = 0.005), yet carbapenem-resistant isolates retained sensitivity to cefiderocol and sulbactam-durlobactam. RJX84154 was associated with multidrug-resistance across all pathogens (P = 0.0018) and in E. coli (P = 0.0024). Low albumin levels were associated with mortality and length of stay in this sample population. blaCTX-M-15 was correlated with multidrug-resistance in E. coli, and blaOXA-72 depth predicted meropenem minimum inhibitory concentration in A. baumannii. RJX84154 may play a role in multidrug-resistance.

IMPORTANCE

While there have been several studies that attempt to find clinical predictors of outcomes in patients hospitalized with bacterial infections, less has been done to combine clinical data with genomic mechanisms of antibiotic resistance. This study focused on a hospitalized patient population in Israel with infections due to medically important bacterial pathogens as a way to build a framework that would unite clinical data with both bacterial antibiotic susceptibility and genomic data. Merging both clinical and genomic data allowed us to find both bacterial and clinical factors that impact certain clinical outcomes. As genome sequencing of bacteria becomes both rapid and commonplace, near real-time monitoring of resistance determinants could help to optimize clinical care and potentially improve outcomes in these patients.

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.

Characterisation of a new virulent phage isolated from Hainan Island with potential against multidrug-resistant Pseudomonas aeruginosa infections

Multidrug-resistant (MDR) Pseudomonas aeruginosa is a serious life-threatening pathogen. The rise in P. aeruginosa resistance rates has renewed interest in phages as an alternative therapeutic approach for treating bacterial infections. In this study, we investigated the characteristics of the first Pseudomonas phage, vB_PaP_HN01, isolated from Hainan, the only tropical island in China. The lytic rate of this phage against P. aeruginosa reached 64.3 % (27/42). Under the optimal multiplicity of infection (MOI) of 0.1, more than 90 % of phage particles absorb onto the host cell within 10 min, with an eclipse period of around 15 min, and a high titer phage production (1011 PFU/ml) within 90 min was demonstrated. vB_PaP_HN01 maintains a robust titer after 1 h exposure to pH values and temperatures (up to 50 °C). Genome annotation revealed that vB_PaP_HN01 did not contain drug-resistance or lysogeny-associated genes. It can effectively inhibit the formation of biofilms of MDR P. aeruginosa and eliminated aggressive biofilms (removal rate about 70 %). In the in vivo infection models, it was demonstrated that the survival rate and lifespan of Galleria mellonella larvae were increased alongside the injection of vB_PaP_HN01. These data revealed the potential of vB_PaP_HN01 against P. aeruginosa in clinic.

Antimicrobial Peptides: A Promising Alternative to Conventional Antimicrobials for Combating Polymicrobial Biofilms

Polymicrobial biofilms adhere to surfaces and enhance pathogen resistance to conventional treatments, significantly contributing to chronic infections in the respiratory tract, oral cavity, chronic wounds, and on medical devices. This review examines antimicrobial peptides (AMPs) as a promising alternative to traditional antibiotics for treating biofilm-associated infections. AMPs, which can be produced as part of the innate immune response or synthesized therapeutically, have broad-spectrum antimicrobial activity, often disrupting microbial cell membranes and causing cell death. Many specifically target negatively charged bacterial membranes, unlike host cell membranes. Research shows AMPs effectively inhibit and disrupt polymicrobial biofilms and can enhance conventional antibiotics' efficacy. Preclinical and clinical research is advancing, with animal studies and clinical trials showing promise against multidrug-resistant bacteria and fungi. Numerous patents indicate increasing interest in AMPs. However, challenges such as peptide stability, potential cytotoxicity, and high production costs must be addressed. Ongoing research focuses on optimizing AMP structures, enhancing stability, and developing cost-effective production methods. In summary, AMPs offer a novel approach to combating biofilm-associated infections, with their unique mechanisms and synergistic potential with existing antibiotics positioning them as promising candidates for future treatments.

Antimicrobial resistance: a concise update

Antimicrobial resistance (AMR) is a serious threat to global public health, with approximately 5 million deaths associated with bacterial AMR in 2019. Tackling AMR requires a multifaceted and cohesive approach that ranges from increased understanding of mechanisms and drivers at the individual and population levels, AMR surveillance, antimicrobial stewardship, improved infection prevention and control measures, and strengthened global policies and funding to development of novel antimicrobial therapeutic strategies. In this rapidly advancing field, this Review provides a concise update on AMR, encompassing epidemiology, evolution, underlying mechanisms (primarily those related to last-line or newer generation of antibiotics), infection prevention and control measures, access to antibiotics, antimicrobial stewardship, AMR surveillance, and emerging non-antibiotic therapeutic approaches. The Review also discusses the potential roles of artificial intelligence in addressing AMR, including antimicrobial susceptibility testing, AMR surveillance, antimicrobial stewardship, diagnosis, and antimicrobial drug discovery and development. This Review highlights the urgent need for addressing the global effects of AMR and for rapid advancement of relevant technology in this dynamic field.

Molecular Epidemiology of Carbapenemase-Producing Pseudomonas aeruginosa: An Iranian Referral Hospital-Based Study

In recent years, there has been a significant increase in infections caused by carbapenemase-producing strains, with carbapenem-resistant Pseudomonas aeruginosa (CRPA) emerging as a priority pathogen according to the World Health Organization. This study aimed to evaluate the molecular epidemiology of CRPA isolated from patients referred to Children's Medical Center in Tehran, Iran. P. aeruginosa isolates collected from different children's wards were screened for common carbapenem-resistant genes by polymerase chain reaction (PCR). Genetic relatedness between isolates was assessed by pulsed-field gel electrophoresis (PFGE). The study included 133 participants, with 50% being male, and revealed a median age of 2 years (interquartile range: 6 months to 6 years). Carbapenem resistance was detected in 15% of cases (n = 20), with CRPA isolates predominantly found in the emergency ward (60%). The median age of patients with CRPA was significantly higher than those with carbapenem-susceptible P. aeruginosa (6 years vs. 1 year). PCR analysis revealed metallo-β-lactamase production in 45% of CRPA isolates (n = 9), with blaNDM being the most prevalent gene. PFGE analysis of the CRPA isolates identified three clusters (Cluster I, II, and III). Cluster I, comprising 65% of all isolates (n = 13), was predominantly found in the emergency ward. Notably, blaNDM-producing strains were prevalent in the emergency ward. Our study highlights the significant prevalence of CRPA in the emergency ward of our hospital and underscores the importance of targeted surveillance and infection control measures to curb its spread within health care settings.

Antimicrobial resistance and carbapenemase dissemination in Pseudomonas aeruginosa isolates from Libyan hospitals: a call for surveillance and intervention

Pseudomonas aeruginosa is a multidrug-resistant bacterium capable of forming biofilms. This study aimed to assess resistance of clinical isolates from Libyan hospitals to antipseudomonal antibiotics, the prevalence of selected extended-spectrum β-lactamases and carbapenemase genes among these isolates, and the microorganisms' capacity for alginate and biofilm production. Forty-five isolates were collected from four hospitals in Benghazi and Derna, Libya. Antimicrobial susceptibility was determined using agar disc diffusion. The presence of resistance genes (blaCTXM, blaTEM, blaSHV-1, blaGES-1, blaKPC, and blaNDM) was screened using PCR. Biofilm formation was quantified via the crystal violet assay, while alginate production was measured spectrophotometrically. Resistance to antipseudomonal antibiotics ranged from 48.9% to 75.6%. The most prevalent resistance gene was blaNDM (26.7%), followed by blaGES-1 (17.8%). Moreover, all isolates demonstrated varying degrees of biofilm-forming ability and alginate production. No statistically significant correlation was found between biofilm formation and alginate production. The dissemination of resistant genes in P. aeruginosa, particularly carbapenemases, is of great concern. This issue is compounded by the bacteria's biofilm-forming capability. Urgent intervention and continuous surveillance are imperative to prevent further deterioration and the catastrophic spread of resistance among these formidable bacteria.

Mitigating Health Risks Through Environmental Tracking of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a prevalent nosocomial pathogen and a significant reservoir of antimicrobial resistance genes in residential and built environments. It is also widespread in various indoor and outdoor settings, including sewage, surface waters, soil, recreational waters (both treated and untreated), and industrial effluents. Surveillance efforts for P. aeruginosa are primarily focused on hospitals rather than built environments. However, evidence links multidrug-resistant P. aeruginosa of human origin with activity in built environments and hospital settings. Consequently, tracking this pathogen across all environments is crucial for understanding the mechanisms of reverse transmission from built environments to humans. This review explores public health hygiene by examining the prevalence of P. aeruginosa in various environments, its sequence types, the factors contributing to multidrug resistance, and the identification methods through global surveillance. Whole-genome sequencing with sequence typing and real-time quantitative PCR are widely used to identify and study antimicrobial-resistant strains worldwide. Additionally, advanced techniques such as functional metagenomics, next-generation sequencing, MALDI-TOF, and biosensors are being extensively employed to detect antimicrobial-resistant strains and mitigate the ongoing evolution of bacterial resistance to antibiotics. Our review strongly underscores the importance of environmental monitoring of P. aeruginosa in preventing human infections. Furthermore, strategic planning in built environments is essential for effective epidemiological surveillance of P. aeruginosa and the development of comprehensive risk assessment models.

Effectiveness of traditional non-carbapenem β-lactams vs. novel β-lactams for the treatment of carbapenem-resistant Pseudomonas aeruginosa: a retrospective cohort study

BACKGROUND

The World Health Organization (WHO) has identified carbapenem-resistant Pseudomonas aeruginosa (CRPA) as one of the three critical priority pathogens. There is scarce literature evaluating the treatment outcomes in patients with CRPA infections treated with traditional non-carbapenem β-lactam (NCBL) agents. Thus, this study aims to assess the effectiveness of traditional NCBL compared to novel β-lactam agents (NVL) for treating non-carbapenem β-lactam -susceptible CRPA.

METHODS

A single-center retrospective cohort study was conducted between January 2016 and December 2022. The study included adult patients 18 years and older with infection due to CRPA who were treated based on microbiology sensitivity with traditional NCBL or NVL for more than 48 h. The primary outcome was 30-day mortality.

RESULTS

124 patients were included: 98 (79%) in the NCBL group and 26 (20.9%) in the NVL group. 78 (62.9%) patients were male. The median (interquartile range (IQR)) age of included patients was 64 (45, 77) years. A total of 84 (67.7%) patients were critically ill, with an overall median (IQR) APACHE II score of 18 (13.5, 23). The rates of 30-day mortality in NCBL and NVL groups were 41 (41.8%) and 12 (46.2%), respectively; P = 0.692.

CONCLUSION

In patients with CRPA infections susceptible to traditional NCBL, there was no statisticallly significant difference in 30-day mortality among patients who were treated with traditional NCBL compared with NVL. Further studies with larger sample sizes are needed to confirm these findings.

Decadal Evolution of KPC-related plasmids in Pseudomonas aeruginosa high-risk clone ST463 in Zhejiang, China

Klebsiella pneumoniae carbapenemase-producing Pseudomonas aeruginosa (KPC-PA) isolates have quickly expanded in China, especially the high-risk clone ST463. We aimed to explore the evolution of KPC-related plasmids driving ST463 clone success. Whole-genome sequencing of 1258 clinical P. aeruginosa strains (2011-2020) identified 106 ST463-PA isolates, with a KPC prevalence of 90.6%. Early on (2011-2012), ST463-PA obtained the KPC-encoding type II (pT2-KPC) or type I plasmid (pT1-KPC) to overcome carbapenem stress. Between 2012 and 2017, pT1-KPC plasmid dominated due to its lower fitness costs and IS26-driven blaKPC amplification ability. By 2017-2020, large fragment deletions in pT1-KPC formed pT1del-KPC plasmid. It conferred even lower fitness costs, enhanced blaKPC-2 gene stability, and greater copy-number flexibility, while maintaining horizontal transmission ability. Consequently, pT1del-KPC plasmid finally succeeded, making ST463 the dominant ST in China. Our findings highlight evolutionary pressures driving ST463 dominance and emphasize the need for targeted strategies to control its spread and antibiotic resistance development.

blaGES-producing ST654 comprises a quarter of all carbapenem-resistant Pseudomonas aeruginosa in blood isolates from 15 hospitals

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) are of major clinical concern. We analyzed 85 P. aeruginosa blood isolates non-susceptible to carbapenems collected during 2021-2023 from 15 medical centers in Israel. We aimed to determine the prevalence of high-risk clones, examine clonality, test antibiotic susceptibility, and assess the presence of acquired resistance genes, including carbapenemases. Whole-genome sequencing was performed using Illumina sequencing technology. Susceptibly was determined using the broth microdilution method. In the entire sample, 43.5% were high-risk clones. A main clade (27.1% of isolates) found in multiple hospitals comprised 19 isolates belonging to the high-risk ST654 clone and four closely related isolates. The isolates in this main clade harbored a broad set of resistance genes, including GES-type genes, and 91% had a mutated outer membrane protein (OprD). Isolates in the main clade were uniformly tobramycin (TOB) resistant and 83% were ceftolozane/tazobactam resistant. In the entire sample, we found high resistance to most antipseudomonal agents, including new beta-lactam/beta-lactamase inhibitor combinations. No uniform susceptibility to an antipseudomonal agent was found. Carbapenemases were carried by 9.4% of isolates (5.9% blaGES-5 and 3.5% blaNDM-1) and oprD was mutated in 67% of isolates. Thus, the epidemiology of CRPA is explained by a combination of clonal expansion of a dominant high-risk clade and sporadic occurrence of mutated strains. Our findings highlight the importance of susceptibility testing using a wide panel of antibiotics when CRPA is detected. Prevention measures tracking and controlling emerging high-risk clades and clones are crucial to limit the spread of CRPA.

Human airway epithelium controls Pseudomonas aeruginosa infection via inducible nitric oxide synthase

Introduction

Airway epithelial cells play a central role in the innate immune response to invading bacteria, yet adequate human infection models are lacking.

Methods

We utilized mucociliary-differentiated human airway organoids with direct access to the apical side of epithelial cells to model the initial phase of Pseudomonas aeruginosa respiratory tract infection.

Results

Immunofluorescence of infected organoids revealed that Pseudomonas aeruginosa invades the epithelial barrier and subsequently proliferates within the epithelial space. RNA sequencing analysis demonstrated that Pseudomonas infection stimulated innate antimicrobial immune responses, but specifically enhanced the expression of genes of the nitric oxide metabolic pathway. We demonstrated that activation of inducible nitric oxide synthase (iNOS) in airway organoids exposed bacteria to nitrosative stress, effectively inhibiting intra-epithelial pathogen proliferation. Pharmacological inhibition of iNOS resulted in expansion of bacterial proliferation whereas a NO producing drug reduced bacterial numbers. iNOS expression was mainly localized to ciliated epithelial cells of infected airway organoids, which was confirmed in primary human lung tissue during Pseudomonas pneumonia.

Discussion

Our findings highlight the critical role of epithelial-derived iNOS in host defence against Pseudomonas aeruginosa infection. Furthermore, we describe a human tissue model that accurately mimics the airway epithelium, providing a valuable framework for systemically studying host-pathogen interactions in respiratory infections.

Revealing quorum-sensing networks in Pseudomonas aeruginosa infections through internal and external signals to prevent new resistance trends

In the context of growing antibiotic resistance in bacteria, the quorum-sensing (QS) system of Pseudomonas aeruginosa (P. aeruginosa) has become a target for new therapeutic strategies. QS is a crucial communication process and an essential pathogenic mechanism. This comprehensive review explores the critical role of QS in the pathogenesis of P. aeruginosa infections, including lung, burn, bloodstream, gastrointestinal, corneal, and urinary tract infections. In addition, this review delves into the complexity of the bacterial QS communication network and highlights the intricate mechanisms underlying these pathological processes. Notably, in addition to the four main QS systems, bacterial QS can interact with various external and internal signaling networks, such as host environments and nutrients in the external microbiome, as well as internal virulence regulation systems within bacteria. These elements can significantly influence the behavior and virulence of microbial communities. Therefore, this review reveals that inhibitors targeting singular QS pathways may inadvertently promote virulence in other pathways, leading to new trends in drug resistance. In response to evolving resistance challenges, this study proposes more cautious treatment strategies, including multitarget interventions and combination therapies, aimed at combating the escalating issue of resistance.

Not all carbapenem-resistant Pseudomonas aeruginosa strains are alike: tailoring antibiotic therapy based on resistance mechanisms

PURPOSE OF REVIEW

To correlate the resistance mechanisms and the susceptibility to new antibiotics in Pseudomonas aeruginosa .

RECENT FINDINGS

Definition of antibiotic resistance in Pseudomonas aeruginosa is still debated. Carbapenem-resistant Pseudomonas aeruginosa (CRPA) and difficult-to-treat resistant Pseudomonas aeruginosa (DTR-PA) are used but which of them better correlate with the risk of mortality remains debated. Mechanisms underlying resistance in Pseudomonas aeruginosa are complex and may be combined, resulting in unpredictable phenotype and cross-resistance. Thus, not all CRPA are alike and tailoring antibiotic therapy on resistance mechanisms is challenging.

SUMMARY

Current guidelines recommend the use of new antipseudomonal agents for CRPA or DTR-PA infections but they don't provide specific information on how tailoring antibiotic therapy on underlying resistance mechanisms. This review may be useful to understand which mechanisms are involved in CRPA and may have practical implications helping clinicians to select an appropriate antibiotic regimen. Several antibiotics are now available for Pseudomonas aeruginosa but their rational use is important to avoid development of future resistance. The knowledge of local epidemiology and most common resistance mechanisms may guide empirical therapy, but targeted antibiotic therapy should be re-evaluated as soon as susceptibility testing profile is available and selected according to Pseudomonas aeruginosa phenotype.

Unveiling the Dynamics of Antimicrobial Resistance: A Year-Long Surveillance (2023) at the Largest Infectious Disease Profile Hospital in Western Romania

Background/Objectives: Antimicrobial resistance (AMR) is a critical global health threat, leading to increased morbidity, mortality, and healthcare costs. This study aimed to identify the most common bacterial pathogens and their resistance profiles from 2179 positive clinical cultures from inpatients at "Victor Babes" Hospital of Infectious Disease and Pneumoftiziology Timisoara in 2023. Methods: Samples were collected from sputum, bronchial aspiration, hemoculture, urine, wound secretions, catheter samples, and other clinical specimens. Results: Key pathogens identified included Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, with notable resistance patterns, observed K. pneumoniae exhibited high resistance rates, notably 41.41% in Quarter 1, while E. coli showed 35.93% resistance in the same period. S. aureus, particularly MRSA, remained a persistent challenge, with 169 cases recorded over the year. A. baumannii and P. aeruginosa displayed alarming levels of multi-drug resistance, especially in Quarter 3 (88.24% and 22.02%, respectively). Although there was a general decline in resistance rates by Quarter 4, critical pathogens such as S. aureus and K. pneumoniae continued to exhibit significant resistance (81.25% and 21.74%, respectively). Conclusions: The study's findings align with the broader antimicrobial resistance trends observed in Romania, where high resistance rates in K. pneumoniae, E. coli, S. aureus (MRSA), Acinetobacter, and Pseudomonas species have been widely reported, reflecting the country's ongoing struggle with multi-drug-resistant infections. Despite some reductions in resistance rates across quarters, the persistent presence of these resistant strains underscores the critical need for strengthened antimicrobial stewardship, infection control measures, and continuous surveillance to combat the growing threat of AMR in Romania and similar healthcare settings.