Epidemiology and risk factors of extensively drug-resistant Pseudomonas aeruginosa infections

The Role of blaOXA-101 and blaOXA-573 in Extensively Drug-Resistant/ Pan Drug-Resistant (XDR/PDR) Pseudomonas aeruginosa Resistance to Ceftazidime-Avibactam

Objective

To explore the association of the resistance of extensively drug-resistant/ pan-drug-resistant Pseudomonas aeruginosa (XDR/PDR-PA) to ceftazidime-avibactam (CZA) with various class D β-lactamase genes.

Methods

Twofold dilution was used to determine the minimum inhibitory concentration (MIC) of CZA against XDR/PDR-PA. Whole genome sequencing and bioinformatics analysis were used to determine the drug-resistant genes of each isolate. Pearson correlation coefficient and statistical analysis were used to assess the association of the resistance of XDR/PDR-PA to CZA and various class D β-lactamase genes.

Results

ST244 was the predominant type (34/68, 50%) among the 68 XDR/PDR-PA strains. Subsequently, ST357 was the second most prevalent type (5/68, 7.4%) strain. blaOXA-101 and blaOXA-573 genes were associated with resistance to CZA (p-value was 0.029 and 0.021, respectively) in the 68 XDR/PDR-PA isolates tested.

Conclusion

Our work found that blaOXA-101 and blaOXA-847 play a role in XDR/PDR-PA resistance to CZA.

Antimicrobial Resistance and Mortality in Carbapenem-Resistant Pseudomonas aeruginosa Infections in Southern Thailand

Background/Objectives: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is an important pathogen associated with high mortality and treatment failure rates. We aimed to assess the susceptibility of CRPA to antipseudomonal agents, identify its resistance mechanisms, and evaluate clinical outcomes in a sample of CRPA isolates. Methods: This was an in vitro study of a clinical isolate of CRPA from hospitalized patients with CRPA infection and a retrospective observational study of these patients, who were diagnosed between 14 February 2021 and 10 August 2023 at Songklanagarind Hospital in Songkhla, Thailand. In vitro experiments were conducted to determine the minimum inhibitory concentrations (MICs) of the antipseudomonal agents using the broth microdilution method. Resistance mechanisms were assessed using the modified carbapenem inactivation method, combined disk tests, and quantitative real-time reverse transcription polymerase chain reaction. Results: A total of 140 CRPA isolates were analyzed. Both traditional and novel β-lactams had high MICs. The most common resistance mechanism was the upregulation of the MexAB-OprM efflux pump (81.3%), followed by the downregulation of the OprD porin (48.9%) and metallo-β-lactamase (MBL) production (45.0%), and the overexpression of blaAmpC (41.0%). The 30-day all-cause mortality rate was 30.5%. The risk factors associated with 30-day mortality included a Charlson Comorbidity Index of ≥5 (OR: 3.43; 95% CI: 1.07-10.99; p = 0.03), sepsis (OR: 10.62; 95% CI: 1.26-89.44; p = 0.03), and septic shock (OR: 4.39; 95% CI: 1.67-11.55; p < 0.01). In contrast, receiving active documented therapy was significantly associated with reduced mortality (OR: 0.17; 95% CI: 0.04-0.74; p = 0.01). Conclusions: This study revealed higher MIC values of all β-lactams for CRPA, while colistin and amikacin remained effective. The resistance mechanisms included MexAB-OprM overexpression, OprD downregulation, MBL production, and blaAmpC overexpression, with a higher prevalence of MBL than in other regions of Thailand. High 30-day mortality was associated with comorbidities, sepsis, and septic shock, but active therapy reduced mortality.

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.

Multidrug resistance of Pseudomonas aeruginosa: do virulence properties impact on resistance patterns?

Introduction

Patients with nosocomial infections are at risk of multidrug-resistant (MDR) Pseudomonas aeruginosa since these bacteria slow down the entire treatment process, increasing the morbidity and mortality of patients staying in hospital. The purpose of the research was to assess the simultaneous presence of multidrug resistance and virulence factors among nosocomial strains of P. aeruginosa to evaluate significant association among them.

Methods

One hundred and eight clinical isolates of P. aeruginosa were found in a variety of samples taken from patients having nosocomial infection, including wound swabs, pus, sputum, tracheal aspirate, and urine. An antibiogram was performed to investigate the pathogen's antibiotic sensitivity pattern against 14 widely used antibiotics in Bangladesh. Virulence factors were evaluated, and the presence of ten β-lactamase and six virulence genes was analyzed by performing PCR. By using a binary logistic regression test with a 95% confidence interval, the relationship between MDR phenotypes and the virulence attributes was assessed.

Results

The susceptibility rate among the isolates was 70-75% for aminoglycosides (amikacin, gentamicin, netilmicin), 15-20% for cephalosporins (ceftazidime, ceftriaxone), 30-35% for quinolones (ciprofloxacin, levofloxacin), 10-15% for tetracyclines (tigecycline, doxycycline), 15-20% for carbapenem (meropenem), 10-15% for sulfonamide (co-trimoxazole), 5-10% for amoxiclav, and 30-35% for piperacillin/tazobactam. A total of 74.1% of the strains carried metallo-β-lactamase (MBL) genes. Among the isolates, 89% showed hemolytic activity, 80-90% produced different pigments such as fluorescein and pyoverdine, 46% were strong biofilm producers, and all the isolates presented different types of motilities (swimming, swarming, and twitching). The virulence genes (lasB, exoS, toxA, aprA, algD, and plcH) were detected within a range of 60-80% of the isolates.

Discussion

Only the toxA gene and twitching motility showed a significant correlation (p-value = 0.001 and 0.028, respectively) with multidrug resistance in the clinical P. aeruginosa isolates which indicates that it can be used as a drug target to combat these organisms. The high prevalence of MDR strains and their association with virulence factors revealed the potential of the pathogen to cause an infection. The current study advocates for immediate epidemiological surveillance of MDR P. aeruginosa strains in Bangladesh to impede the rapid dissemination of this opportunistic pathogen.

Risk Factors and Outcomes of Multidrug-resistant Pseudomonas aeruginosa in Kelantan, Malaysia: A Multicenter Case-control Study

Background

Increasing trend and spread of multidrug-resistant Pseudomonas aeruginosa (MDR-PA) in clinical settings is a great challenge in managing patients with infections caused by this pathogen.

Objective

To determine the risk factors and outcomes of MDR-PA acquisition in the northeastern state of Malaysia. In addition, this study also reported on the susceptibility pattern and common resistant genes among MDR-PA.

Materials and Methods

MDR-PA isolates obtained between March 2021 and February 2022 from all four major hospitals in the state of Kelantan, Malaysia, were submitted for susceptibility and resistant genes identification. The clinical data of the patients with MDR-PA were retrospectively reviewed. The risk factors and outcomes of MDR-PA acquired patients were analyzed by comparing with patients who acquired susceptible-PA while admitted to the same hospital during the study time.

Results

A total of 100 MDR-PA and 100 susceptible-PA cases were included. Ceftolozane-tazobactam was susceptible in 41.3% of MDR-PA compared to only 4%-8% with other β-lactams. About half (46%) of the MDR-PA isolates harbored the bla -NDM-1 gene, but none had the bla -OXA-48 gene. Factors independently associated with MDR-PA acquisitions were age (OR: 1.02; P = 0.028), genitourinary disorder (OR: 6.89; P = 0.001), and central venous catheter (OR: 3.18; P = 0.001). In addition, MDR-PA acquisitions were found to be associated with antimicrobial treatment failure (41.1% vs. 25.0%; P = 0.001) and mortality (40.0% versus 6.0%; P <0.001).

Conclusion

Most of the MDR-PA strains in Kelantan tertiary hospitals harbored the bla -NDM-1 gene, which is easily transmissible and can lead to an outbreak. Nonetheless, a significant number of the MDR-PA isolates were still susceptible to ceftolozane-tazobactam.

Occurrence of Plasmid-Mediated Quinolone Resistance and Carbapenemase-Encoding Genes in Pseudomonas aeruginosa Isolates from Nosocomial Patients in Aguascalientes, Mexico

Pseudomonas aeruginosa is a leading cause of healthcare-associated infections, which are related to substantial morbidity and mortality. The incidence of Plasmid-Mediated Quinolone Resistance (PMQR) determinants has been previously reported in this bacterium. However, there is limited information regarding the presence of PMQR and carbapenemase-encoding genes simultaneously. This study aims to analyze the prevalence of these determinants on P. aeruginosa strain isolated from clinical patients in the State of Aguascalientes, Mexico. Fifty-two P. aeruginosa isolates from nosocomial patients were collected from Centenario Hospital Miguel Hidalgo. This is a retrospective observational study conducted at a single center. Antibiotic susceptibility was tested using the Vitek-2 system. Only carbapenem-resistant isolates were included in this study. Carbapenemase-encoding genes and PMQR determinants were screened by polymerase chain reaction (PCR). Resistance rates of 100% were found on tigecycline and ceftriaxone. Of the 52 isolates, 34.6% were positive for the qnr genes, 46.2% for the oqxA gene, and 25% for the aac-(6')-lb gene. The most frequent carbapenemase genes found in the samples were blaOXA-51 (42.3%), blaOXA-1 (15.4%), and blaVIM (15.4%). blaOXA-51 co-carrying oqxA was detected in 21.1% of the isolates, blaOXA-51 co-carrying aac-(6')-lb in 11.5%, blaVIM co-carrying aac-(6')-lb in 3.8%, and blaKPC co-carrying oqxA in 5.8%. Systematic surveillance to detect carbapenemase-encoding genes and PMQR determinants, and rational prescription using the last-line drugs could help in preventing the dissemination of multidrug-resistant determinants.

Risk factors and clinical impact of multidrug resistance in healthcare-associated bacteraemic urinary tract infections: a post-hoc analysis of a multicentre prospective cohort in Spain

BACKGROUND

The global burden associated with antimicrobial resistance is of increasing concern.

AIM

To evaluate risk factors associated with multidrug-resistant (MDR) infection and its clinical impact in a cohort of patients with healthcare-associated bacteraemic urinary tract infections (BUTIs).

METHODS

This was a prospective, multicentre, post-hoc analysis of patients with healthcare-associated-BUTI (ITUBRAS-2). The primary outcome was MDR profile. Secondary outcomes were clinical response (at 48-72 h and at hospital discharge) and length of hospital stay from onset of BUTI. Logistic regression was used to evaluate variables associated with MDR profile and clinical response. Length of hospital stay was evaluated using multivariate median regression.

FINDINGS

In all, 443 episodes were included, of which 271 (61.17%) were classified as expressing an MDR profile. In univariate analysis, MDR profile was associated with E. coli episodes (odds ratio (OR): 3.13; 95% confidence interval (CI): 2.11-4.69, P < 0.001) and the extensively drug-resistant (XDR) pattern with P. aeruginosa aetiology (7.84; 2.37-25.95; P = 0.001). MDR was independently associated with prior use of fluoroquinolones (adjusted OR: 2.43; 95% CI: 1.25-4.69), cephalosporins (2.14; 1.35-3.41), and imipenem or meropenem (2.08; 1.03-4.20) but not with prior ertapenem. In terms of outcomes, MDR profile was not associated with lower frequency of clinical cure, but was associated with longer hospital stay.

CONCLUSION

MDR profile was independently associated with prior use of fluoroquinolones, cephalosporins, imipenem, and meropenem, but not with prior ertapenem. MDR-BUTI episodes were not associated with worse clinical cure, although they were independently associated with longer duration of hospital stay.

Characterization and genetic analysis of extensively drug-resistant hospital acquired Pseudomonas aeruginosa isolates

BACKGROUND

The incidence of hospital-acquired infections in extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) has been increasing worldwide and is frequently associated with an increase in mortality and morbidity rates. The aim of this study was to characterize clinical XDR-PA isolates recovered during six months at three different hospitals in Egypt.

RESULTS

Seventy hospital-acquired clinical isolates of P. aeruginosa were classified into multidrug-resistant (MDR), extensively drug-resistant (XDR) and pandrug-resistant (PDR), according to their antimicrobial resistance profile. In addition, the possession of genes associated with mobile genetic elements and genes encoding antimicrobial resistance determinants among isolates were detected using polymerase chain reaction. As a result, a significant percentage of the isolates (75.7%) were XDR, while 18.5% were MDR, however only 5.7% of the isolates were non-MDR. The phenotypic detection of carbapenemases, extended-spectrum β-lactamases (ESBLs) and metallo β-lactamase (MBL) enzymes showed that 73.6% of XDR-PA isolates were carbapenemases producers, whereas 75.5% and 88.7% of XDR-PA isolates produced ESBLs and MBL respectively. In addition, PCR screening showed that oxa gene was the most frequently detected gene of carbapenemases (91.4%), while aac(6')-lb gene was mostly detected (84.3%) among the screened aminoglycosides-resistance genes. Furthermore, the molecular detection of the colistin resistance gene showed that 12.9% of isolates harbored mcr-1 gene. Concerning mobile genetic element markers (intI, traA, tnp513, and merA), intI was the highest detected gene as it was amplified in 67 isolates (95.7%). Finally, phylogenetic and molecular typing of the isolates via ERIC-PCR analysis revealed 10 different ERIC fingerprints.

CONCLUSION

The present study revealed a high prevalence of XDR-PA in hospital settings which were resistant to a variety of antibiotics due to several mechanisms. In addition, 98% of the XDR-PA clinical isolates contained at least one gene associated with movable genetic elements, which could have aided the evolution of these XDR-PA strains. To reduce spread of drug resistance, judicious use of antimicrobial agents and strict infection control measures are therefore essential.

A comparison of strategies for identifying patients at risk for carbapenem-resistant or extended β-lactam-resistant Pseudomonas aeruginosa

OBJECTIVES

To assess risk factors for carbapenem-resistant Pseudomonas aeruginosa (CR) and extended-β-lactam-resistant P. aeruginosa (EBR) infection/colonization, and to develop and compare tools for predicting isolation of CR and EBR from clinical cultures.

METHODS

This retrospective study analysed hospitalized patients with positive P. aeruginosa cultures between 2015 and 2021. Two case-control analyses were performed to identify risk factors and develop scoring tools for distinguishing patients with CR versus carbapenem-susceptible (CS) P. aeruginosa and EBR versus CS P. aeruginosa. The performance of institutionally derived scores, externally derived scores and the presence/absence of key risk factors to predict CR and EBR were then compared.

RESULTS

A total of 2379 patients were included. Of these, 8.3% had a positive culture for CR, 5.0% for EBR and 86.7% for CS P. aeruginosa. There was substantial overlap in risk factors for CR and EBR. Institutional risk scores demonstrated modestly higher area under the ROC curve values than external scores for predicting CR (0.67 versus 0.58) and EBR (0.76 versus 0.70). Assessing the presence/absence of ≥1 of the two strongest predictors (prior carbapenem use or CR isolation within 90 days) was slightly inferior to scoring tools for predicting CR, and comparable for predicting EBR.

CONCLUSIONS

Clinicians concerned about CR in P. aeruginosa should consider the likelihood of EBR when making treatment decisions. A simple approach of assessing recent history of CR isolation or carbapenem usage performed similarly to more complex scoring tools and offers a more pragmatic way of identifying patients who require coverage for resistant P. aeruginosa.

Sepsis-Related Lung Injury and the Complication of Extrapulmonary Pneumococcal Pneumonia

Globally, sepsis and pneumonia account for significant mortality and morbidity. A complex interplay of immune-molecular pathways underlies both sepsis and pneumonia, resulting in similar and overlapping disease characteristics. Sepsis could result from unmanaged pneumonia. Similarly, sepsis patients have pneumonia as a common complication in the intensive care unit. A significant percentage of pneumonia is misdiagnosed as septic shock. Therefore, our knowledge of the clinical relationship between pneumonia and sepsis is imperative to the proper management of these syndromes. Regarding pathogenesis and etiology, pneumococcus is one of the leading pathogens implicated in both pneumonia and sepsis syndromes. Growing evidence suggests that pneumococcal pneumonia can potentially disseminate and consequently induce systemic inflammation and severe sepsis. Streptococcus pneumoniae could potentially exploit the function of dendritic cells (DCs) to facilitate bacterial dissemination. This highlights the importance of pathogen-immune cell crosstalk in the pathophysiology of sepsis and pneumonia. The role of DCs in pneumococcal infections and sepsis is not well understood. Therefore, studying the immunologic crosstalk between pneumococcus and host immune mediators is crucial to elucidating the pathophysiology of pneumonia-induced lung injury and sepsis. This knowledge would help mitigate clinical diagnosis and management challenges.

Extensively drug-resistant Pseudomonas aeruginosa: clinical features and treatment with ceftazidime/avibactam and ceftolozane/tazobactam in a tertiary care university hospital center in Portugal - A cross-sectional and retrospective observational study

Introduction

Extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) is a growing concern due to its increasing incidence, limited therapeutic options, limited data on the optimal treatment, and high mortality rates. The study aimed to characterize the population, the outcome and the microbiological characteristics of XDR-PA identified in a Portuguese university hospital center.

Methods

All XDR-PA isolates between January 2019 and December 2021 were identified. XDR-PA was defined as resistance to piperacillin-tazobactam, third and fourth generation cephalosporins, carbapenems, aminoglycosides and fluoroquinolones. A retrospective analysis of the medical records was performed.

Results

One hundred seventy-eight individual episodes among 130 patients with XDR-PA detection were identified. The most common sources of infection were respiratory (32%) and urinary tracts (30%), although skin and soft tissue infections (18%) and primary bacteremia (14%) were also prevalent. Colonization was admitted in 64 cases. Several patients had risk factors for complicated infections, most notably immunosuppression, structural lung abnormalities, major surgery, hemodialysis or foreign intravascular or urinary devices. XDR-PA identification was more frequent in male patients with an average age of 64.3 ± 17.5 years. One non-susceptibility to colistin was reported. Only 12.4% were susceptible to aztreonam. Ceftazidime-avibactam (CZA) was susceptible in 71.5% of the tested isolates. Ceftolozane-tazobactam (C/T) was susceptible in 77.5% of the tested isolates. Antibiotic regimens with XDR-PA coverage were reserved for patients with declared infection, except to cystic fibrosis. The most frequently administered antibiotics were colistin (41 cases), CZA (39 cases), and C/T (16 cases). When combination therapy was used, CZA plus colistin was preferred. The global mortality rate among infected patients was 35.1%, significantly higher in those with hematologic malignancy (50.0%, p < 0.05), followed by the ones with bacteremia (44.4%, p < 0.05) and those medicated with colistin (39.0%, p < 0.05), especially the ones with respiratory infections (60.0%). Among patients treated with CZA or C/T, the mortality rate seemed to be lower.

Discussion

XDR-PA infections can be severe and difficult to treat, with a high mortality rate. Even though colistin seems to be a viable option, it is likely less safe and efficient than CZA and C/T. To the best of the authors' knowledge, this is the first description of the clinical infection characteristics and treatment of XDR-PA in Portugal.

Repurposing Mitomycin C in Combination with Pentamidine or Gentamicin to Treat Infections with Multi-Drug-Resistant (MDR) Pseudomonas aeruginosa

The aims of this study were (i) to determine if the combination of mitomycin C with pentamidine or existing antibiotics resulted in enhanced efficacy versus infections with MDR P. aeruginosa in vivo; and (ii) to determine if the doses of mitomycin C and pentamidine in combination can be reduced to levels that are non-toxic in humans but still retain antibacterial activity. Resistant clinical isolates of P. aeruginosa, a mutant strain over-expressing the MexAB-OprM resistance nodulation division (RND) efflux pump and a strain with three RND pumps deleted, were used. MIC assays indicated that all strains were sensitive to mitomycin C, but deletion of three RND pumps resulted in hypersensitivity and over-expression of MexAB-OprM caused some resistance. These results imply that mitomycin C is a substrate of the RND efflux pumps. Mitomycin C monotherapy successfully treated infected Galleria mellonella larvae, albeit at doses too high for human administration. Checkerboard and time-kill assays showed that the combination of mitomycin C with pentamidine, or the antibiotic gentamicin, resulted in synergistic inhibition of most P. aeruginosa strains in vitro. In vivo, administration of a combination therapy of mitomycin C with pentamidine, or gentamicin, to G. mellonella larvae infected with P. aeruginosa resulted in enhanced efficacy compared with monotherapies for the majority of MDR clinical isolates. Notably, the therapeutic benefit conferred by the combination therapy occurred with doses of mitomycin C close to those used in human medicine. Thus, repurposing mitomycin C in combination therapies to target MDR P. aeruginosa infections merits further investigation.

Genomic and metabolic versatility of Pseudomonas aeruginosa contributes to its inter-kingdom transmission and survival

Pseudomonas aeruginosa is one of the most versatile bacteria with renowned pathogenicity and extensive drug resistance. The diverse habitats of this bacterium include fresh, saline and drainage waters, soil, moist surfaces, taps, showerheads, pipelines, medical implants, nematodes, insects, plants, animals, birds and humans. The arsenal of virulence factors produced by P. aeruginosa includes pyocyanin, rhamnolipids, siderophores, lytic enzymes, toxins and polysaccharides. All these virulent elements coupled with intrinsic, adaptive and acquired antibiotic resistance facilitate persistent colonization and lethal infections in different hosts. To date, treating pulmonary diseases remains complicated due to the chronic secondary infections triggered by hospital-acquired P. aeruginosa. On the contrary, this bacterium can improve plant growth by suppressing phytopathogens and insects. Notably, P. aeruginosa is one of the very few bacteria capable of trans-kingdom transmission and infection. Transfer of P. aeruginosa strains from plant materials to hospital wards, animals to humans, and humans to their pets occurs relatively often. Recently, we have identified that plant-associated P. aeruginosa strains could be pathologically similar to clinical isolates. In this review, we have highlighted the genomic and metabolic factors that facilitate the dominance of P. aeruginosa across different biological kingdoms and the varying roles of this bacterium in plant and human health.

Evolving trends among Pseudomonas aeruginosa: a 12-year retrospective study from the United Arab Emirates

INTRODUCTION

Pseudomonas is a group of ubiquitous non-fermenting Gram-negative bacteria (NFGNB). Of the several species associated with humans, Pseudomonas aeruginosa (PA) can acclimate to diverse environments. The global frequency of PA infections is rising and is complicated by this organism's high intrinsic and acquired resistance to several clinically relevant antibiotics. Data on the epidemiology, levels, and trends of antimicrobial resistance of PA in clinical settings in the MENA/GCC region is scarce.

METHODS

A retrospective 12-year analysis of 56,618 non-duplicate diagnostic Pseudomonas spp. from the United Arab Emirates (UAE) was conducted. Data was generated at 317 surveillance sites by routine patient care during 2010-2021, collected by trained personnel and reported by participating surveillance sites to the UAE National antimicrobial resistance (AMR) Surveillance program. Data analysis was conducted with WHONET (https://whonet.org/).

RESULTS

Among the total isolates (N = 56,618), the majority were PA (95.6%). Data on nationality revealed 44.1% were UAE nationals. Most isolates were from soft tissue (55.7%), followed by respiratory tract (26.7%). PA was more commonly found among inpatients than among outpatients, followed by ICUs. PA showed a horizontal trend for resistance to fluoroquinolones, 3rd- and 4th-generation cephalosporins, and decreasing trends of resistance for aminoglycosides and meropenem. The highest percentage of multidrug resistant (MDR) isolates was reported in 2011 at 35.6%. As an overall trend, the percentage of MDR, extensively drug-resistant (XDR), and possible pandrug-resistant (PDR) isolates generally declined over the study period. Carbapenem-resistant PA (CRPA) were associated with a higher mortality (RR: 2.7), increased admission to ICU (RR: 2.3), and increased length of stay (LOS) (12 excess inpatient days per case), as compared to carbapenem-susceptible PA (CSPA).

CONCLUSION

The resistance trends in Pseudomonas species in the UAE indicated a decline in AMR and in percentages of Pseudomonas isolates with MDR and XDR profiles. The sustained Pseudomonas spp. circulation particularly in the hospital settings highlights the importance of surveillance techniques, infection control strategies, and stewardship to limit the continued dissemination. This data also shows that CRPA are associated with higher mortality, increased ICU admission rates, and a longer hospitalization, thus higher costs due to increased number of in-hospital and ICU days.

Risk factors and outcome associated with coinfection with carbapenem-resistant Klebsiella pneumoniae and carbapenem-resistant Pseudomonas aeruginosa or Acinetobacter baumanii: a descriptive analysis

Background

Nearly 30% of patients infected with carbapenem-resistant Klebsiella pneumoniae (CRKP) were previously shown to be coinfected with carbapenem-resistant Pseudomonas aeruginosa (CRPA) or Acinetobacter baumannii (CRAB). Infections caused by multiple carbapenem-resistant pathogens present significant challenge to infection control and therapeutic management. The study objective was to identify risk factors for acquisition of multiple carbapenem-resistant pathogens and associated outcomes.

Methods

A descriptive analysis of adults infected with either CRKP alone or coinfected with CRPA or CRAB was performed. Patient groups were compared on demographics, clinical characteristics, treatment, and outcome.

Results

86 patients with CRKP monoinfection and 60 patients with coinfections were evaluated. Respiratory tract was the predominant infection site for coinfected patients involving mostly CRPA whereas urinary tract was the primary site for CRKP-only group. More coinfected patients were severely debilitated, had prior carbapenem exposure (37% vs 13%, p<0.001) and history of pneumonia in the past year (67% vs 41%, p<0.01). More coinfected patients required direct ICU admission (45% vs 27%, p=0.02) and had prolonged length of stay (median 15 vs 10 days, p<0.01) than the CRKP-only group but mortality rates (18% vs 16%) were similar.

Conclusions

CRKP coinfection with another carbapenem-resistant pathogen adds significant morbidity and healthcare burden overall. Empiric therapy with reliable activity against both CRKP and carbapenem-resistant Pseudomonas aeruginosa may be prudent for at risk patients with pneumonia.

Carbapenems versus β-lactam and β-lactamase inhibitors for treatment of nosocomial pneumonia: A systematic review and meta-analysis

Background

Carbapenems and β-lactam and β-lactamase inhibitors (BLBLIs) have been used empirically in nosocomial pneumonia, but their efficacy and safety are controversial.

Objective

We carried out a systematic review with meta-analysis to evaluate the efficacy and safety of carbapenems versus BLBLIs against nosocomial pneumonia.

Methods

PubMed, Embase, Cochrane Central Register of Controlled Trials, CNKI, Wangfang, VIP and Sinomed were searched systematically through April 29, 2023 for clinical trials comparing carbapenems with BLBLIs for treatment of nosocomial pneumonia. Random-effects models were used to evaluate the impact of treatment on the risk ratio (RR) of all-cause mortality, clinical response, microbiologic response, resistance by Pseudomonas aeruginosa, adverse effects (AEs), and serious adverse effects. The quality of the evidence was assessed with the Cochrane risk of bias tool. The review was registerted in the INPLASY (INPLASY202340113).

Results

Seven randomized controlled trials containing 3306 patients met our inclusion criteria Our meta-analysis showed no significant difference in all-cause mortality (RR = 0.88, 95% confidence interval [CI] = 0.75-1.03, I2 = 0%) or clinical cure (1.02, 0.96-1.09, 30%) or clinical failure (1.19, 0.97-1.47, 0%) or microbiologic clinical cure (0.98, 0.89-1.06, 40%) or Pseudomonas aeruginosa resistance (RR 2.43, CI 0.86-6.81, 49%, P = 0.09) or adverse events (0.98, 0.93-1.02, 0%) between carbapenems groups versus BLBLIs groups, but a significant difference was found for severe adverse events (RR 0.83, CI 0.73-0.94, 0%).

Conclusion

Differences in the prevalence of mortality, clinical cure, or clinical failure were not observed between carbapenems groups versus BLBLIs groups in terms of nosocomial pneumonia. The use of carbapenems was linked to a tendency towards the emergence of P. aeruginosa resistance, however, no statistically significant difference was observed.

Case Commentary: Successful Use of Cefepime/Zidebactam (WCK 5222) as a Salvage Therapy for the Treatment of Disseminated Extensively Drug-Resistant New Delhi Metallo-β-Lactamase-Producing Pseudomonas aeruginosa Infection in an Adult Patient with Acute T-Cell Leukemia

Multidrug-resistant/extensively drug-resistant (MDR/XDR) Pseudomonas aeruginosa (PA) are critical antimicrobial resistance threats. Despite their increasing prevalence, treatment options for metallo-β-lactamase (MBL)-producing PA are limited, especially for New Delhi metallo-β-lactamase (NDM) producers. Pending further clinical studies, this case provides support for limited-scope use of cefepime-zidebactam for treating disseminated infections secondary to NDM-producing XDR PA. Susceptibilities should be tested and/or alternative regimens considered when treating isolates with alternative MBLs or increased efflux pump expression because some in vitro data suggest associated loss of cefepime-zidebactam susceptibility.

The study of NF-κB transcription factor activation by Pseudomonas aeruginosa recombinant proteins in eukaryotic cell culture

The transcription factor NF-κB is a key factor in the activation of immune responses; it is in turn activated by pattern recognition receptors, such as TLR and NLR receptors. The search for ligands activating innate immunity receptors is an important scientific problem due to the possibility of their use as adjuvants and immunomodulators. In this study the effect of recombinant Pseudomonas aeruginosa OprF proteins and a toxoid (a deletion atoxic form of exotoxin A) on the activation of TLR4, TLR9, NOD1, and NOD2 receptors has been investigated. The study was carried out using free and co-adsorbed on Al(OH)₃ P. aeruginosa proteins and eukaryotic cells encoding these receptors and having NF-κB-dependent reporter genes. The enzymes encoded by the reported genes are able to cleave the substrate with the formation of a colored product, the concentration of which indicates the degree of receptor activation. It was found that free and adsorbed forms of the toxoid were able to activate the TLR4 surface receptor for lipopolysaccharide. OprF and the toxoid activated the intracellular NOD1 receptor, but only in the free form. This may be due to the fact that the cell lines used were not able to phagocytize aluminum hydroxide particles with protein adsorbed on them.

The impact of multi-drug resistant Pseudomonas aeruginosa infections on acute pancreatitis patients

INTRODUCTION

Acute pancreatitis (AP) accounts for a high proportion of digestive diseases worldwide and has a high risk of infection. Pseudomonas aeruginosa, a common pathogen of hospital infections, has been observed to increase the resistance rate to several antibiotics, causing difficulties in treatments. Our study aims to investigate the impact of the multi-drug resistant Pseudomonas aeruginosa (MDR-PA) infections on AP patients.

METHODS

At two Chinese tertiary referral centers for AP patients infected with MDR-PA, a retrospective case-control study with a 1:2 case-control ratio was performed. Comparisons were preformed between with/without MDR-PA infections and different drug-resistance of MDR-PA infections patients, respectively. Independent risk factors of overall mortality were assessed via univariate and multivariate binary logistic regression analyses, and the distribution and antibiotic resistant rates of strains were described.

RESULTS

Mortality in AP patients with MDR-PA infections was significantly higher than in those without MDR-PA infections (7 (30.4%) vs. 4 (8.7%), P = 0.048). The rate of prophylactic use of carbapenem for 3 days (0 vs. 50%, P = 0.019) and the incidence rate of multiple organ failure (MOF) (0 vs. 57.1%, P = 0.018) were remarkably higher in the carbapenem-resistant Pseudomonas aeruginosa group compared with the carbapenem-sensitive Pseudomonas aeruginosa group. In the multivariate analysis, the severe categories of AP (OR = 13.624, 95% CIs = 1.567-118.491, P = 0.018) and MDR-PA infections (OR = 4.788, 95% CIs = 1.107-20.709, P = 0.036) were independent risk factors for mortality. The resistance rates of MDR-PA strains were low for amikacin (7.4%), tobramycin (3.7%), and gentamicin (18.5%). The resistance rates of MDR-PA strains to imipenem and meropenem were up to, 51.9% and 55.6%, respectively.

CONCLUSION

In AP patients, severe categories of AP and MDR-PA infections were both independent risk factors for mortality. Inappropriate use of carbapenem antibiotics and MOF were related to carbapenem-resistant Pseudomonas aeruginosa infections. Amikacin, tobramycin, and gentamicin are recommended for the treatment of AP patients with MDR-PA infections.

Infected pancreatic necrosis: outcomes and clinical predictors of mortality. A post hoc analysis of the MANCTRA-1 international study

The identification of high-risk patients in the early stages of infected pancreatic necrosis (IPN) is critical, because it could help the clinicians to adopt more effective management strategies. We conducted a post hoc analysis of the MANCTRA-1 international study to assess the association between clinical risk factors and mortality among adult patients with IPN. Univariable and multivariable logistic regression models were used to identify prognostic factors of mortality. We identified 247 consecutive patients with IPN hospitalised between January 2019 and December 2020. History of uncontrolled arterial hypertension (p = 0.032; 95% CI 1.135-15.882; aOR 4.245), qSOFA (p = 0.005; 95% CI 1.359-5.879; aOR 2.828), renal failure (p = 0.022; 95% CI 1.138-5.442; aOR 2.489), and haemodynamic failure (p = 0.018; 95% CI 1.184-5.978; aOR 2.661), were identified as independent predictors of mortality in IPN patients. Cholangitis (p = 0.003; 95% CI 1.598-9.930; aOR 3.983), abdominal compartment syndrome (p = 0.032; 95% CI 1.090-6.967; aOR 2.735), and gastrointestinal/intra-abdominal bleeding (p = 0.009; 95% CI 1.286-5.712; aOR 2.710) were independently associated with the risk of mortality. Upfront open surgical necrosectomy was strongly associated with the risk of mortality (p < 0.001; 95% CI 1.912-7.442; aOR 3.772), whereas endoscopic drainage of pancreatic necrosis (p = 0.018; 95% CI 0.138-0.834; aOR 0.339) and enteral nutrition (p = 0.003; 95% CI 0.143-0.716; aOR 0.320) were found as protective factors. Organ failure, acute cholangitis, and upfront open surgical necrosectomy were the most significant predictors of mortality. Our study confirmed that, even in a subgroup of particularly ill patients such as those with IPN, upfront open surgery should be avoided as much as possible. Study protocol registered in ClinicalTrials.Gov (I.D. Number NCT04747990).

Pathogen Distribution, Drug Resistance Risk Factors, and Construction of Risk Prediction Model for Drug-Resistant Bacterial Infection in Hospitalized Patients at the Respiratory Department During the COVID-19 Pandemic

Objective

To investigate the distribution and drug resistance of pathogens among hospitalized patients in the respiratory unit during the COVID-19 pandemic, analyze the risk factors of drug resistance, construct a risk prediction model.

Methods

This study isolated 791 strains from 489 patients admitted to the Affiliated Hospital of Chengdu University, who were retrospectively enrolled between December 2019 and June 2021. The patients were divided into training and validation sets based on a random number table method (8:2). The baseline information, clinical characteristics, and culture results were collected using an electronic database and WHONET 5.6 software and compared between the two groups. A risk prediction model for drug-resistant bacteria was constructed using multi-factor logistic regression.

Results

K. pneumoniae (24.78%), P. aeruginosa (17.19%), A. baumannii (10.37%), and E. coli (10.37%) were the most abundant bacterial isolates. 174 isolates of drug-resistant bacteria were collected, ie, Carbapenem-resistant organism-strains, ESBL-producing strains, methicillin-resistant S. aureus, multi-drug resistance constituting 38.51%, 50.57%, 6.32%, 4.60%, respectively. The nosocomial infection prediction model of drug-resistant bacteria was developed based on the combined use of antimicrobials, pharmacological immunosuppression, PCT>0.5 ng/mL, CKD stage 4-5, indwelling catheter, and age > 60 years. The AUC under the ROC curve of the training and validation sets were 0.768 (95% CI: 0.624-0.817) and 0.753 (95% CI: 0.657-0.785), respectively. Our model revealed an acceptable prediction demonstrated by a non-significant Hosmer-Lemeshow test (training set, p=0.54; validation set, p=0.88).

Conclusion

K. pneumoniae, P. aeruginosa, A. baumannii, and E. coli were the most abundant bacterial isolates. Antimicrobial resistance among the common isolates was high for most routinely used antimicrobials and carbapenems. COVID-19 did not increase the drug resistance pressure of the main strains. The risk prediction model of drug-resistant bacterial infection is expected to improve the prevention and control of antibacterial-resistant bacterial infection in hospital settings.

Pseudomonas aeruginosa Bloodstream Infection, Resistance, and Mortality: Do Solid Organ Transplant Recipients Do Better or Worse?

BACKGROUND

The prevalence of antimicrobial resistance of Pseudomonas aeruginosa (P. aeruginosa) in solid organ transplant (SOT) recipients is higher than that of the general population. However, the literature supporting this statement is scarce. Identifying patients at risk of carbapenem resistance (CR) is of great importance, as CR strains more often receive inappropriate empiric antibiotic therapy, which is independently associated with mortality in bloodstream infections (BSIs).

METHODS

We prospectively recorded data from all consecutive BSIs from January 1991 to July 2019 using a routine purpose-designed surveillance database. The following variables were included: age, sex, type of transplant, use of vascular and urinary catheters, presence of neutropenia, period of diagnosis, treatment with steroids, origin of BSI, source of bacteremia, septic shock, ICU admission, mechanical ventilation, previous antibiotic treatment, treatment of bacteremia, and 30-day all-cause mortality.

RESULTS

We identified 2057 episodes of P. aeruginosa BSI. Of these, 265 (13%) episodes corresponded to SOT recipients (130 kidney transplants, 105 liver, 9 hearts, and 21 kidney-pancreas). Hematologic malignancy [OR 2.71 (95% CI 1.33-5.51), p = 0.006] and prior carbapenem therapy [OR 2.37 (95% CI 1.46-3.86), p < 0.001] were associated with a higher risk of having a CR P. aeruginosa BSI. Age [OR 1.03 (95% CI 1.02-1.04) p < 0.001], urinary catheter [OR 2.05 (95% CI 0.37-3.06), p < 0.001], shock at onset [OR 6.57 (95% CI 4.54-9.51) p < 0.001], high-risk source [OR 4.96 (95% CI 3.32-7.43) p < 0.001], and bacteremia caused by CR strains [OR 1.53 (95% CI 1.01-2.29) p = 0.036] were associated with increased mortality. Correct empirical therapy was protective [OR 0.52 (95% CI 0.35-0.75) p = 0.001]. Mortality at 30 days was higher in non-SOT patients (21% vs. 13%, p = 0.002). SOT was not associated with a higher risk of having a CR P. aeruginosa BSI or higher mortality.

CONCLUSIONS

In our cohort of 2057 patients with P. aeruginosa BSIs, hematologic malignancies and previous carbapenem therapy were independently associated with a risk of presenting CR P. aeruginosa BSI. Age, urinary catheter, high-risk source, bacteremia caused by carbapenem-resistant strains, and severity of the infection were independently associated with mortality, whereas correct empirical therapy was a protective factor. An increasing trend in the resistance of P. aeruginosa was found, with >30% of the isolates being resistant to carbapenems in the last period. SOT was not associated with a higher risk of carbapenem-resistant BSIs or higher mortality.

Pseudomonas aeruginosa: Infections, Animal Modeling, and Therapeutics

Pseudomonas aeruginosa is an important Gram-negative opportunistic pathogen which causes many severe acute and chronic infections with high morbidity, and mortality rates as high as 40%. What makes P. aeruginosa a particularly challenging pathogen is its high intrinsic and acquired resistance to many of the available antibiotics. In this review, we review the important acute and chronic infections caused by this pathogen. We next discuss various animal models which have been developed to evaluate P. aeruginosa pathogenesis and assess therapeutics against this pathogen. Next, we review current treatments (antibiotics and vaccines) and provide an overview of their efficacies and their limitations. Finally, we highlight exciting literature on novel antibiotic-free strategies to control P. aeruginosa infections.

Ceftazidime-avibactam activity against Gram-negative respiratory isolates collected between 2018 and 2019

OBJECTIVES

The objective of this study was to assess the in vitro activity of ceftazidime-avibactam (CAZ-AVI) and a panel of comparator agents against isolates of Enterobacter spp., Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa collected in 2018 and 2019 by different centres worldwide from patients with respiratory tract infections.

METHODS

Susceptibility and minimum inhibitory concentration (MIC) of all organisms were determined using broth microdilution methodology for CAZ-AVI, and a panel of comparator antimicrobial agents by a central reference laboratory according to Clinical and Laboratory Standards Institute guidelines and European Committee on Antimicrobial Susceptibility Testing guidelines.

RESULTS

CAZ-AVI demonstrated potent antimicrobial activity against isolates of Enterobacter spp. (97.6% susceptibility, MIC₉₀, 1 µg/ml), E. coli (98.5% susceptibility, MIC₉₀^, 0.25 µg/ml), K. pneumoniae (94.7% susceptibility, MIC₉₀ 2 µg/ml), and P. aeruginosa (91.2% susceptibility, MIC₉₀ 8 µg/ml). CAZ-AVI was also active (susceptibility >85%) against MDR isolates for all organisms except P. aeruginosa. Only a small proportion (<10%) of all isolates of Enterobacter spp. and E. coli were identified as XDR compared to isolates of K. pneumoniae and P. aeruginosa isolates (>20%). Susceptibility to CAZ-AVI was high (>70%) among XDR isolates of Enterobacter spp., K. pneumoniae, and E. coli, compared to P. aeruginosa (<70%). Among the comparator agents, only colistin showed consistent activity across all the organisms (>85%).

CONCLUSION

Gram-negative respiratory isolates collected in 2018-2019 showed high susceptibility to CAZ-AVI; CAZ-AVI represents a potential treatment option against infection caused by these organisms.

Pseudomonas infection reduction in the ICU: a successful multidisciplinary quality improvement project

Pseudomonas aeruginosa infection causes high morbidity and mortality, especially in immunocompromised patients. Pseudomonas can develop multidrug resistance. As a result, it can cause serious outbreaks in hospital and intensive care unit (ICU) settings, increasing both length of stay and costs. In the second quarter of 2020, in a community hospital's 15-bed ICU, the P. aeruginosa-positive sputum culture rate was unacceptably high, with a trend of increasing prevalence over the previous 3 quarters. We performed a multidisciplinary quality improvement (QI) initiative to decrease the P. aeruginosa-positive rate in our ICU. We used the Define, Measure, Analyze, Improve, and Control model of Lean Six Sigma for our QI initiative to decrease the P. aeruginosa-positive sputum culture rate by 50% over the following year without affecting the baseline environmental services cleaning time. A Plan-Do-Study-Act approach was used for key interventions, which included use of sterile water for nasogastric and orogastric tubes, adherence to procedure for inline tubing and canister exchanges, replacement of faucet aerators, addition of hopper covers, and periodic water testing. We analyzed and compared positive sputum culture rates quarterly from pre-intervention to post-intervention. The initial P. aeruginosa-positive culture rate of 10.98 infections per 1,000 patient-days in a baseline sample of 820 patients decreased to 3.44 and 2.72 per 1,000 patient-days in the following 2 post-intervention measurements. Environmental services cleaning time remained stable at 34 minutes. Multiple steps involving all stakeholders were implemented to maintain this progress. A combination of multidisciplinary efforts and QI methods was able to prevent a possible ICU P. aeruginosa outbreak.

The Efficacy of Colistin Combined with Amikacin or Levofloxacin against Pseudomonas aeruginosa Biofilm Infection

Pseudomonas aeruginosa (PA) biofilm infection is clinically prevalent and difficult to eradicate. In the present work, we aimed to evaluate the in vitro and in vivo efficacy of colistin (COL)-based combinations against PA biofilm. MICs and fractional inhibitory concentration indexes (FICIs) of four antibiotics (COL, amikacin, levofloxacin, and meropenem) to bioluminescent strain PAO1, carbapenem-resistant PAO1 (CRPAO1), and clinically isolated strains were assessed. Minimal biofilm eradication concentrations (MBECs) of monotherapy and combinations were examined by counting the live bacteria in biofilm, accompanied by visual confirmation using confocal laser-scanning microscopy. An animal biofilm infection model was established by implanting biofilm subcutaneously, and the therapeutic effect was evaluated according to the change in luminescence through a live animal bio-photonic imaging system. In vitro, even combined with 4 or 8 mg/L COL, meropenem needed to reach 128 or 256 mg/L to eradicate the biofilm. Moreover, 2 mg/L COL combined with 32 mg/L amikacin or 4-8 mg/L levofloxacin could kill the PAO1 and CRPAO1 in biofilm within 24 h. In vivo, COL combined with amikacin or levofloxacin could shorten the eradication time of biofilm than monotherapy. For PAO1 biofilm, combination therapy could eradicate the biofilm in all mice on the 5th day, whereas monotherapy only eradicated biofilms in almost half of the mice. For CRPAO1 biofilm, the biofilm eradication rate on the 6th day in the COL+ amikacin, amikacin, or COL alone regimen was 90%, 10%, or 40%, respectively. COL combined with levofloxacin did not show a better effect than each individual antibiotic. COL-based combinations containing levofloxacin or amikacin were promising choices for treating PA biofilm infection. IMPORTANCE Infections associated with PA biofilm formation are extremely challenging. When monotherapy fails to achieve optimal efficacy, combination therapy becomes the last option. After evaluating multiple drug combinations through a series of experiments in vitro and in vivo, we confirmed that colistin-based combinations containing levofloxacin or amikacin were promising choices for treating PA biofilm infection. The efficacy of these combinations derives from the different bactericidal mechanisms and the bacterial susceptibility to each antibiotic. This study provided a new regimen to solve the incurable problem of biofilm by using COL combined with other antibiotics.

Carbapenem-Only Combination Therapy against Multi-Drug Resistant Pseudomonas aeruginosa: Assessment of In Vitro and In Vivo Efficacy and Mode of Action

The aim of the study was to determine the efficacy of carbapenem-only combination treatments derived from four approved drugs (meropenem, doripenem, ertapenem and imipenem) against a MDR strain of P. aeruginosa in a Galleria mellonella larvae infection model. G. mellonella larvae were infected with P. aeruginosa NCTC 13437 (carrying the VIM 10 carbapenamase) and the efficacy of the six possible dual, four triple, and one quadruple carbapenem combination(s) were compared to their constituent monotherapies. Four of these combinations showed significantly enhanced survival compared to monotherapies and reduced the bacterial burden inside infected larvae but without complete elimination. Bacteria that survived combination therapy were slower growing, less virulent but with unchanged carbapenem MICs-observations that are consistent with a persister phenotype. In vitro time-kill assays confirmed that the combinations were bactericidal and confirmed that a low number of bacteria survived exposure. Mass spectrometry was used to quantify changes in the concentration of carbapenems in the presence of carbapenemase-carrying P. aeruginosa. The rate of degradation of individual carbapenems was altered, and often significantly reduced, when the drugs were in combinations compared with the drugs alone. These differences may account for the enhanced inhibitory effects of the combinations against carbapenem-resistant P. aeruginosa and are consistent with a 'shielding' hypothesis. In conclusion, carbapenem combinations show promise in combating MDR P. aeruginosa and are worthy of additional study and development.

Risk Factors and Outcomes for Multidrug Resistant Pseudomonas aeruginosa Infection in Immunocompromised Patients

Background: Pseudomonas aeruginosa (PSA) infection often occurs in immunocompromised patients, which also face an increased risk of multidrug-resistant (MDR) bacteria. A deeper knowledge of the risk factors for MDR-PSA infection in this patient population may help to choose appropriate empirical antibiotic therapy. Methods: a single-center case-control (1:2) retrospective study that included 48 patients with underlying immunosuppression developing MDR-PSA infection (cases) and 96 patients also immunocompromised that were infected with non-MDR-PSA (controls) was conducted. Both groups were matched by site of infection, clinical features and type of immunosuppression. Risk factors for MDR-PSA were assessed by logistic regression. Clinical outcomes were also compared between both groups. Results: immunosuppression was due to solid cancer in 63 (43.8%) patients, solid organ transplantation in 39 (27.1%), hematological disease in 35 (24.3%) and other causes in 7 (4.9%). Independent risk factors for MDR-PSA infection were diabetes mellitus (odds ratio [OR]: 4.74; 95% confidence interval [CI]: 1.63−13.79; p = 0.004), antibiotic therapy in the previous 3 months (OR: 5.32; 95% CI: 1.93−14.73; p = 0.001), previous MDR-PSA colonization (OR: 42.1; 95% CI: 4.49−394.8; p = 0.001) and septic shock (OR: 3.73; 95% CI: 1.36−10.21; p = 0.010). MDR-PSA cases were less likely to receive adequate empirical therapy (14 [29.2%] vs. 69 [71.9%]; p < 0.001). 30-day clinical improvement was less common in MDR-PSA cases (25 [52.1%] vs. 76 [79.2%]; p = 0.001). Conclusions: diabetes mellitus, previous MDR-PSA colonization, prior receipt of antibiotics and septic shock acted as risk factors for developing MDR-PSA infections in immunocompromised patients, who have a poorer outcome than those infected with non-MDR-PSA strains.

The Mechanism of Action of Lactoferrin - Nucleoside Diphosphate Kinase Complex in Combating Biofilm Formation

BACKGROUND

The ESKAPE group of pathogens which comprise of multidrug resistant bacteria, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species are the cause of deadly nosocomial infections all over the world. While these pathogens have developed robust strategies to resist most antibiotics, their ability to form biofilms is one of their most combative properties. Hence there is an urgent need to discover new antibacterial agents which could prevent or destroy the biofilms made by these bacteria. Though it has been established that lactoferrin (LF), a potent iron binding antibacterial, antifungal, and antiviral protein displays anti-biofilm properties, its mechanisms of action, in addition to its iron chelation property, still remains unclear.

OBJECTIVE

The binding and inhibition studies of LF with the enzyme Nucleoside diphosphate Kinase (NDK) and its elastase cleaved truncated 12 kDa fragment (12-NDK).

METHODS

The characterization studies of NDK and 12-NDK using florescence spectroscopy, dynamic light scattering, size exclusion chromatography and ADP-glo Kinase Assay. Inhibition studies of LF-NDK using ADP-glo kinase assay, Surface Plasmon Resonance and Biofilm inhibition studies.

RESULTS

NDK and 12-NDK were cloned, expressed and purified from Acinetobacter baumannii and Pseudomonas aeruginosa. The characterization studies revealed NDK and 12-NDK from both species are stable and functional. The inhibition studies of LF-NDK revealed stable binding and inhibition of kinase activity by LF.

CONCLUSION

The binding and inhibition studies have shown that while LF binds with both the NDK and their truncated forms, it tends to have a higher binding affinity with the truncated 12 kDa fragments, resulting in their decreased kinase activity. This study essentially gives a new direction to the field of inhibition of biofilm formation, as it proves that LF has a novel mechanism of action in other than iron sequestration.

Predictors of multidrug resistant Pseudomonas aeruginosa involvement in bloodstream infections

PURPOSE OF REVIEW

In the last decades, there has been a worldwide worrisome spread of multidrug resistant (MDR) Pseudomonas aeruginosa. Treatment of these infections is challenging, in part due to the lack of therapeutic options, and the importance of prescribing an adequate empirical treatment. Bacteraemia is one of the most severe infections, with mortality rates ranging between 20 and 40%.

RECENT FINDINGS

It is key to understand which patients are at a higher risk of MDR P. aeruginosa bloodstream infection (BSI) to better direct empirical therapies and improve overall survival. Immunocompromised patients are among the most vulnerable for the worst outcomes. Environmental exposure, integrity of the microbiota, and host immunity are the key determinants for the initial colonization and expansion on mucosal surfaces and potential invasion afterwards by MDR P. aeruginosa.

SUMMARY

Available data suggest that high colonization pressure (settings with high prevalence like intensive care units), disruption of healthy microbiota (prior use of antibiotics, in particular fluoroquinolones), immunosuppression (neutropenia) and breaking natural barriers (venous or urine catheters), are the main risk factors for MDR P. aeruginosa BSI.

Rapid and Direct Action of Lipopolysaccharide (LPS) on Skeletal Muscle of Larval Drosophila

The endotoxin lipopolysaccharide (LPS) from Gram-negative bacteria exerts a direct and rapid effect on tissues. While most attention is given to the downstream actions of the immune system in response to LPS, this study focuses on the direct actions of LPS on skeletal muscle in Drosophila melanogaster. It was noted in earlier studies that the membrane potential rapidly hyperpolarizes in a dose-dependent manner with exposure to LPS from Pseudomonas aeruginosa and Serratia marcescens. The response is transitory while exposed to LPS, and the effect does not appear to be due to calcium-activated potassium channels, activated nitric oxide synthase (NOS), or the opening of Cl- channels. The purpose of this study was to further investigate the mechanism of the hyperpolarization of the larval Drosophila muscle due to exposure of LPS using several different experimental paradigms. It appears this response is unlikely related to activation of the Na-K pump or Ca2+ influx. The unknown activation of a K+ efflux could be responsible. This will be an important factor to consider in treatments of bacterial septicemia and cellular energy demands.

Antimicrobial Susceptibility Trends and Risk Factors for Antimicrobial Resistance in Pseudomonas aeruginosa Bacteremia: 12-Year Experience in a Tertiary Hospital in Korea

BACKGROUND

Infections caused by multidrug-resistant Pseudomonas aeruginosa (MDRPA) have been on the rise worldwide, and delayed active antimicrobial therapy is associated with high mortality. However, few studies have evaluated increases in P. aeruginosa infections with antimicrobial resistance and risk factors for such antimicrobial resistance in Korea. Here, we analyzed changes in antimicrobial susceptibility associated with P. aeruginosa bacteremia and identified risk factors of antimicrobial resistance.

METHODS

The medical records of patients with P. aeruginosa bacteremia who were admitted to a tertiary hospital between January 2009 and October 2020 were retrospectively reviewed. Antibiotic resistance rates were compared among the time periods of 2009-2012, 2013-2016, and 2017-2020 and between the intensive care unit (ICU) and non-ICU setting. Empirical antimicrobial therapy was considered concordant, if the organism was susceptible to antibiotics in vitro, and discordant, if resistant.

RESULTS

During the study period, 295 patients with P. aeruginosa bacteremia were identified. The hepatobiliary tract (26.8%) was the most common primary site of infection. The rates of carbapenem-resistant P. aeruginosa (CRPA), MDRPA, and extensively drug-resistant P. aeruginosa (XDRPA) were 24.7%, 35.9%, and 15.9%, respectively. XDRPA showed an increasing trend, and CRPA, MDRPA, and XDRPA were also gradually increasing in non-ICU setting. Previous exposure to fluoroquinolones and glycopeptides and urinary tract infection were independent risk factors associated with CRPA, MDRPA, and XDRPA. Previous exposure to carbapenems was an independent risk factor of CRPA. CRPA, MDRPA, and XDRPA were associated with discordant empirical antimicrobial therapy.

CONCLUSION

The identification of risk factors for antimicrobial resistance and analysis of antimicrobial susceptibility might be important for concordant empirical antimicrobial therapy in patients with P. aeruginosa bacteremia.

[Not Available]

Antibiotics are one of the greatest advances in modern medicine. Antibiotic resistance is one of the most serious threats to global health, aggravating the prognosis of immunocompromised patients, especially burn patients. Our objective was to study the consumption of antibiotics of critical importance according to the WHO and the correlation between antibiotic resistance in Pseudomonas æruginosa and the consumption of these antibiotics. Our study took place in the Medical Laboratory in collaboration with the Trauma and Burn Center's Burn Unit in Tunisia. In our retrospective study, 1384 non-repetitive strains of Pseudomonas æruginosa responsible for colonization or infection were included, between January 2012 and December 2019. Pseudomonas æruginosa was the most isolated bacterial strain in the service, with an average rate of 15.9% of the service's bacterial ecology. The antibiotic resistance rates tested were high: 77.1% to piperacillin-tazobactam, 56% to ceftazidime, 74.9% to imipenem, 78.8% to amikacin, 54.7% to ciprofloxacin and 32.8% to fosfomycin. Among our strains, 81.8% were multi drug-resistant strains. The analysis of the correlation between the level of consumption of antibiotics and the antibiotic resistance levels in Pseudomonas æruginosa showed that the increased consumption of piperacillin-tazobactam increased resistance not only to piperacillin-tazobactam but also to imipenem and amikacin as well as multi drug resistance. Similarly, the increase in the consumption of fosfomycin correlates with resistance to piperacillin-tazobactam and imipenem.

Nationwide Surveillance and Molecular Characterization of Critically Drug-Resistant Gram-Negative Bacteria: Results of the Research University Network Thailand Study

A large-scale surveillance is an important measure to monitor the regional spread of antimicrobial resistance. We prospectively studied the prevalence and molecular characteristics of clinically important Gram-negative bacilli, including Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii complex (ABC), and Pseudomonas aeruginosa, from blood, respiratory tract, urine, and sterile sites at 47 hospitals across Thailand. Among 187,619 isolates, 93,810 isolates (50.0%) were critically drug resistant, of which 12,915 isolates (13.8%) were randomly selected for molecular characterization. E. coli was most commonly isolated from all specimens, except the respiratory tract, in which ABC was predominant. Prevalence of extended-spectrum cephalosporin resistance (ESCR) was higher in E. coli (42.5%) than K. pneumoniae (32.0%), but carbapenem-resistant (CR)-K. pneumoniae (17.2%) was 4.5-fold higher than CR-E. coli (3.8%). The majority of ESCR/CR-E. coli and K. pneumoniae isolates carried bla_CTX-M (64.6% to 82.1%). bla_NDM and bla_OXA-48-like were the most prevalent carbapenemase genes in CR-E. coli/CR-K. pneumoniae (74.9%/52.9% and 22.4%/54.1%, respectively). In addition, 12.9%/23.0% of CR-E. coli/CR-K. pneumoniae cocarried bla_NDM and bla_OXA-48-like. Among ABC isolates, 41.9% were extensively drug resistant (XDR) and 35.7% were multidrug resistant (MDR), while P. aeruginosa showed XDR/MDR at 6.3%/16.5%. A. baumannii was the most common species among ABC isolates. The major carbapenemase gene in MDR-A. baumannii/XDR-A. baumannii was bla_OXA-23-like (85.8%/93.0%), which had much higher rates than other ABC species. bla_IMP, bla_VIM, bla_OXA-40-like, and bla_OXA-58-like were also detected in ABC at lower rates. The most common carbapenemase gene in MDR/XDR-P. aeruginosa was bla_IMP (29.0%/30.6%), followed by bla_VIM (9.5%/25.3%). The findings reiterate an alarming situation of drug resistance that requires serious control measures.

Carbapenem Resistance Determinants Acquired through Novel Chromosomal Integrations in Extensively Drug-Resistant Pseudomonas aeruginosa

Two novel bla_DIM-1- or bla_IMP-1-containing genomic islands (GIs) were discovered by whole-genome sequence analyses in four extensively drug-resistant (XDR) Pseudomonas aeruginosa isolates from inpatients at a tertiary hospital in Ghana. The strains were of sequence type 234 (ST234) and formed a phylogenetic clade together with ST111, which is recognized as a global high-risk clone. Their carbapenem resistance was encoded by two Tn402-type integrons, In1592 (bla_DIM-1) and In1595 (bla_IMP-1), both carrying complete tni mobilization modules. In1595 was bound by conserved 25-bp inverted repeats (IRs) flanked by 5-bp direct repeats (DRs) associated with target site duplication. The integrons were embedded in two GIs that contained cognate integrases and were distinguished by a lower GC content than the chromosomal average. PAGI-97A (52.659 bp; In1592), which encoded a P4-type site-specific integrase of the tyrosine recombinase family in its 3′ border, was integrated into tRNA-Pro(ggg) and bracketed by a 49-bp perfect DR created by 3′-end target duplication. GIs with the same structural features, but diverse genetic content, were identified in 41/226 completed P. aeruginosa genomes. PAGI-97B (22,636 bp; In1595), which encoded an XerC/D superfamily integrase in its 5′ border, was inserted into the small RNA (sRNA) PrrF1/PrrF2 locus. Specific insertions into this highly conserved locus involved in iron-dependent regulation, all leaving PrrF1 intact, were identified in an additional six phylogenetically unrelated P. aeruginosa genomes. Our molecular analyses unveiled a hospital-associated clonal dissemination of carbapenem-resistant ST234 P. aeruginosa in which the XDR phenotype resulted from novel insertions of two GIs into specific chromosomal sites.

Evaluation of Pseudomonas aeruginosa pathogenesis and therapeutics in military-relevant animal infection models

Modern combat-related injuries are often associated with acute polytrauma. As a consequence of severe combat-related injuries, a dysregulated immune response results in serious infectious complications. The gram-negative bacterium Pseudomonas aeruginosa is an opportunistic pathogen that often causes life-threatening bloodstream, lung, bone, urinary tract, and wound infections following combat-related injuries. The rise in the number of multidrug-resistant P. aeruginosa strains has elevated its importance to civilian clinicians and military medicine. Development of novel therapeutics and treatment options for P. aeruginosa infections is urgently needed. During the process of drug discovery and therapeutic testing, in vivo testing in animal models is a critical step in the bench-to-bedside approach, and required for Food and Drug Administration approval. Here, we review current and past literature with a focus on combat injury-relevant animal models often used to understand infection development, the interplay between P. aeruginosa and the host, and evaluation of novel treatments. Specifically, this review focuses on the following animal infection models: wound, burn, bone, lung, urinary tract, foreign body, and sepsis.

Colistin Dosing Regimens against Pseudomonas aeruginosa in Critically Ill Patients: An Application of Monte Carlo Simulation

Our aims are to assess various colistin dosing regimens against Pseudomonas aeruginosa (P. aeruginosa) infection in critically ill patients and to propose an appropriate regimen based on microbiological data. A Monte Carlo simulation was performed using the published colistin’s pharmacokinetic parameters of critically ill patients, the published pharmacodynamic target from a mouse thigh infection model, and the minimum inhibitory concentration (MIC) results from a Vietnamese hospital. The probability of target attainment (PTA) of 80% and cumulative fraction of response (CFR) of 90% were used to evaluate the efficacy of each regimen. Of 121 P. aeruginosa laboratory datasets, the carbapenem-resistant P. aeruginosa (CRPA) and the colistin-resistant P. aeruginosa rates were 29.8% and 0.8%, respectively. MIC_50,90 were both 0.5 mg/L. The simulated results showed that at MIC of 2 mg/L, most regimens could not reach the PTA target, particularly in patients with normal renal function (Creatinine clearance (CrCl) ≥ 80 mL/min). At MIC of 0.5 mg/L and 1 mg/L, current recommendations still worked well. On the basis of these results, aside from lung infection, our study recommends three regimens against P. aeruginosa infection at MIC of 0.5 mg/L, 1 mg/L, and 2 mg/L. In conclusion, higher total daily doses and fractionated colistin dosing regimens could be the strategy for difficult-to-acquire PTA cases, while a less aggressive dose might be appropriate for empirical treatment in settings with low MIC_50/90.

Molecular Characterization of, and Antimicrobial Resistance in, Clostridioides difficile from Thailand, 2017-2018

Antimicrobial resistance (AMR) plays an important role in the pathogenesis and spread of Clostridioides difficile infection (CDI). Many antimicrobials, such as fluoroquinolones, have been associated with outbreaks of CDI globally. This study characterized AMR among clinical C. difficile strains in Thailand, where antimicrobial use remains inadequately regulated. Stool samples were screened for tcdB and positives were cultured. C. difficile isolates were characterized by toxin profiling and PCR ribotyping. Antimicrobial susceptibility testing was performed by agar incorporation, and whole-genome sequencing and AMR genotyping were performed on a subset of strains. There were 321 C. difficile strains isolated from 326 stool samples. The most common toxigenic ribotype (RT) was RT 017 (18%), followed by RTs 014 (12%) and 020 (7%). Resistance to clindamycin, erythromycin, moxifloxacin, and rifaximin was common, especially among RT 017 strains. AMR genotyping revealed a strong correlation between resistance genotype and phenotype for moxifloxacin and rifaximin. The presence of erm-class genes was associated with high-level clindamycin and erythromycin resistance. Point substitutions in the penicillin-binding proteins were not sufficient to confer meropenem resistance, but a Y721S substitution in PBP3 was associated with a 4.37-fold increase in meropenem minimal inhibitory concentration. No resistance to metronidazole, vancomycin, or fidaxomicin was observed.

High incidence of MDR and XDR Pseudomonas aeruginosa isolates obtained from patients with ventilator-associated pneumonia in Greece, Italy and Spain as part of the MagicBullet clinical trial

OBJECTIVES

To characterize the antimicrobial susceptibility, molecular epidemiology and carbapenem resistance mechanisms in Pseudomonas aeruginosa isolates recovered from respiratory tract samples from patients with ventilator-associated pneumonia enrolled in the MagicBullet clinical trial.

METHODS

Isolates were collected from 53 patients from 12 hospitals in Spain, Italy and Greece. Susceptibility was determined using broth microdilution and Etest. MALDI-TOF MS was used to detect carbapenemase activity and carbapenemases were identified by PCR and sequencing. Molecular epidemiology was investigated using PFGE and MLST.

RESULTS

Of the 53 isolates, 2 (3.8%) were considered pandrug resistant (PDR), 19 (35.8%) were XDR and 16 (30.2%) were MDR. Most (88.9%) of the isolates from Greece were MDR, XDR or PDR, whereas fewer of the isolates from Spain (33.3%) and Italy (43.5%) showed antibiotic resistance. Three Greek isolates were resistant to colistin. Overall, the rates of resistance of P. aeruginosa isolates to imipenem, ciprofloxacin, ceftolozane/tazobactam and ceftazidime/avibactam were 64.1%, 54.7%, 22.6% and 24.5%, respectively. All isolates resistant to ceftolozane/tazobactam and ceftazidime/avibactam (Greece, n = 10; and Italy, n = 2) carried blaVIM-2. Spanish isolates were susceptible to the new drug combinations. Forty-eight restriction patterns and 27 STs were documented. Sixty percent of isolates belonged to six STs, including the high-risk clones ST-111, ST-175 and ST-235.

CONCLUSIONS

MDR/XDR isolates were highly prevalent, particularly in Greece. The most effective antibiotic against P. aeruginosa was colistin, followed by ceftolozane/tazobactam and ceftazidime/avibactam. blaVIM-2 is associated with resistance to ceftolozane/tazobactam and ceftazidime/avibactam, and related to highly resistant phenotypes. ST-111 was the most frequent and disseminated clone and the clonal diversity was lower in XDR and PDR strains.

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Pseudomonas æruginosa (PA) is among the major agents of infection in burns. Multidrug-resistant strains are commonly isolated, which hampers the management of these patients. Our purpose was to study the incidence density of PA colonization and PA infection and to investigate the antibiotic susceptibility of strains isolated in patients hospitalized in the Trauma and Burn Center's Burn Unit (TBC-BU) in Tunisia. It is a retrospective study including 1649 non-repetitive strains of PA during an 8-year period (2012- 2019). PA was the most common organism in TBC-BU bacterial ecology (15%). The incidence density of PA colonization and PA infection was 16.1‰ days of in-patient stay (DH) and 16.5‰ DH, respectively. A positive and statistically significant correlation was found between PA colonization and PA infection (rs=1; p=0,004). The colonization strains were mainly isolated from skin (25.1%) and central catheters (22.3%). Bacteremia was the most common infection (19.5%). The skin was the most common source of bacteremia (22.1%) followed by central catheters (18.3%). The highest rates of antibiotic resistance were found with piperacillin-tazobactam (72.4%), ceftazidime (49.4%), meropenem (74%), imipenem (70.5%), amikacin (74.6%), ciprofloxacin (56.5%) and fosfomycin (35.3%). We did not identify any colistin-resistant strain. The multidrug resistance rate was 78%. The metallo-carbapenemase-producing strains rate was 14.4%.

Analysis of Metallo-β-lactamases, oprD Mutation, and Multidrug Resistance of β-lactam Antibiotic-Resistant Strains of Pseudomonas aeruginosa Isolated from Southern China

The purpose of this study was to analyze the metallo-β-lactamases (MBLs) genotype and oprD mutations of the β-lactam antibiotic-resistant Pseudomonas aeruginosa (PA) strains isolated from southern China. We collected 110 strains of β-lactam antibiotic-resistant PA from 2 hospitals during January 2016–December 2017 from Dongguan, South China. MBLs were detected, amplified, and typed using EDTA disc synergy test, PCR, and Sanger gene sequencing. The mutations and expression levels of oprD were detected using Sanger gene sequencing and qPCR. A total of 16.36% (18/110) β-lactam antibiotic-resistant PA strains produced MBLs, and the main genotypes of MBLs were IMP-25, VIM-2, and SIM-2. Sanger gene sequencing results showed that 107 of the 110 strains harbored mutations in oprD sequence, while 3 strains were negative for oprD amplification (2.73%). Among the 107 strains with positive amplification (97.27%), the rate of intentional mutations (including deletions, insertions, and premature stop codons) was 93.46% (100/107) and that of no disrupted mutation was 6.54% (7/107). qPCR analysis confirmed that the expression level of the OprD protein in the 7 strains of no disrupted mutation was significantly reduced. Among the β-lactam antibiotic-resistant PA strains in southern China, 16.36% were positive for MBLs. The loss rate of oprD was 2.73%, and almost all PA strains showed oprD amplification variation or transcription downregulation. Thus, impaired oprD expression and MBLs production may be some of the mechanisms of β-lactam antibiotic-resistance of PA strains in southern China.

The Effect of Bacterial Endotoxin LPS on Serotonergic Modulation of Glutamatergic Synaptic Transmission

The release of the endotoxin lipopolysaccharides (LPS) from gram-negative bacteria is key in the induction of the downstream cytokine release from cells targeting cells throughout the body. However, LPS itself has direct effects on cellular activity and can alter synaptic transmission. Animals experiencing septicemia are generally in a critical state and are often treated with various pharmacological agents. Since antidepressants related to the serotonergic system have been shown to have a positive outcome for septicemic conditions impacting the central nervous system, the actions of serotonin (5-HT) on neurons also exposed to LPS were investigated. At the model glutamatergic synapse of the crayfish neuromuscular junction (NMJ), 5-HT primarily acts through a 5-HT2A receptor subtype to enhance transmission to the motor neurons. LPS from Serratia marcescens also enhances transmission at the crayfish NMJ but by a currently unknown mechanism. LPS at 100 µg/mL had no significant effect on transmission or on altering the response to 5-HT. LPS at 500 µg/mL increased the amplitude of the evoked synaptic excitatory junction potential, and 5-HT in combination with 500 µg/mL LPS continued to promote enhanced transmission. The preparations maintained responsiveness to serotonin in the presence of low or high concentrations of LPS.

Risk stratification for multidrug-resistant Gram-negative infections in ICU patients

PURPOSE OF REVIEW

Antimicrobial resistance among Gram-negative microorganisms has alarmingly increased in the past 10 years worldwide. Infections caused by these microorganisms are difficult to treat, especially in critically ill patients.The present review examines how to accurately predict which patients carry a greater risk of colonization or infection on which to base the timely choice of an effective empirical antibiotic treatment regimen and avoid antibiotic overuse.

RECENT FINDINGS

There are many risk factors for acquiring one of many multidrug-resistant Gram-negative microorganisms (MDR-GN); however, scores anticipating colonization, infection among those colonized, or mortality among those infected have a variable accuracy. Accuracy of scores anticipating colonization is low. Scores predicting infections among colonized patients are, in general, better, and ICU patients infected with MDR-GN have a worse prognosis than those infected by non-resistant microorganisms. Scores are, in general, better at excluding patients.

SUMMARY

Despite these limitations, scores continue to gain popularity including those by Giannella, Tumbarello, Johnson, or the scores INCREMENT carbapenem-producing Enterobacteriaceae score, Cano, Tartof, or CarbaSCORE.

Characterization of carbapenem-resistant and XDR Pseudomonas aeruginosa in Canada: results of the CANWARD 2007-16 study

OBJECTIVES

Carbapenem-resistant Pseudomonas aeruginosa are emerging worldwide with increasing reports of carbapenemase-producing isolates. Carbapenem-resistant isolates may also be XDR. This study characterized carbapenem-resistant and XDR P. aeruginosa isolated from patients receiving care at Canadian hospitals from 2007 to 2016.

METHODS

Antimicrobial susceptibility testing was performed using CLSI broth microdilution methods. PCR was used to detect carbapenemases (GES, KPC, NDM, IMP, VIM, OXA-48) and other resistance markers; specific carbapenemase gene variants were identified by DNA sequencing. Genetic relatedness was assessed by MLST and PFGE.

RESULTS

From 2007 to 2016, 3864 isolates of P. aeruginosa were collected; 466 (12.1%) isolates were carbapenem resistant. The prevalence of carbapenem-resistant P. aeruginosa reached a peak of 17.3% in 2014. Colistin (94% susceptible) and ceftolozane/tazobactam (92.5%) were the most active agents against carbapenem-resistant P. aeruginosa. XDR P. aeruginosa comprised 4.5% of isolates; they were found to be genetically diverse and remained susceptible to colistin and ceftolozane/tazobactam. Only 4.3% (n = 20) of carbapenem-resistant P. aeruginosa harboured a carbapenemase; most were blaGES-5 (35%, n = 7). Wide genetic diversity was observed among carbapenem-resistant P. aeruginosa with >200 different sequence types identified.

CONCLUSIONS

Although the prevalence of carbapenem-resistant P. aeruginosa in Canada spiked in 2014 and 2015, carbapenemase-producing P. aeruginosa remain rare with only 20 (4.3%) isolates identified over a 10 year period. Broad genetic diversity was observed among both carbapenem-resistant and XDR phenotypes of P. aeruginosa. Pan-drug-resistant P. aeruginosa have not yet been identified in Canada.

Antimicrobial activity of cephalosporin-beta-lactamase inhibitor combinations against drug-susceptible and drug-resistant Pseudomonas aeruginosa strains

Objectives

We conducted this study to test the susceptibility of P. aeruginosa to the routinely used drugs and to the two recently available antimicrobial agents, ceftazidime-avibactam and ceftolozane-tazobactam.

Methods

We isolated the non-replicate strains of P. aeruginosa from inpatients between December 2018 and April 2019. The VITEK® MS system was used for phenotypic identification and VITEK 2 for initial antimicrobial susceptibility testing. We supplemented these tests with determination of the minimum inhibitory concentration (MIC) of four antimicrobials; imipenem, meropenem, ceftazidime-avibactam and ceftolozane-tazobactam. The standards of the Clinical and Laboratory Standards Institute were followed.

Results

A total of 67 strains of P. aeruginosa, including 38 multidrug-resistant strains, were obtained from various specimens. Susceptibility to various tested aminoglycosides and fluoroquinolones was maintained in 49.3–56.7% and 40.0–43.3% of the total isolates. Amongst β-lactams, the strains were susceptible to the following agents in an ascending order: ceftazidime (32.8%), cefepime (37.3%), imipenem (36.0%), piperacillin-tazobactam (39.0%), meropenem (44.8%), ceftazidime-avibactam (61.2%) and ceftolozane-tazobactam (62.7%). The susceptibility rates of the multidrug-resistant strains to both ceftazidime-avibactam and ceftolozane-tazobactam were less than 35%. High levels of resistance to the new agents (MIC > 256 ug/ml) were detected in 21 and 22 isolates.

Conclusion

Our study shows limitation in the empirical use of ceftazidime-avibactam and ceftolozane-tazobactam as therapeutics in serious infections. Moreover, our data highlights the need for prompt antimicrobial susceptibility testing to guide their clinical usage.

IL-17C Protects Nasal Epithelium from Pseudomonas aeruginosa Infection

IL-17 family cytokines are directly involved in host immune responses and the critical mediators for host defense against infection or inflammation. IL-17C is highly expressed in respiratory epithelium and is induced after acute bacterial lung infection. However, the definite function of IL-17C induced by Pseudomonas aeruginosa (PAO1 strain) is not fully understood, and our study was designed to demonstrate IL-17C-induced immune response against PAO1 infection in nasal epithelium. Passage-2 normal human nasal epithelial (NHNE) cells were infected with PAO1 and the relationship between IL-17C-related immune responses and the iron absorption of PAO1, depending on inoculation of recombinant human IL-17C (rhIL-17C), was assessed by measuring the siderophore activity of PAO1. Microarray data showed that IL-17C expression increased 34.7 times at 8 hours postinfection (hpi) in NHNE cells, and IL-17C mRNA levels increased until 48 hpi. The PAO1 colonies significantly increased from 8 hpi in NHNE cells, and siderophore activity of PAO1 was enhanced in the supernatants of PAO1-infected NHNE cells. Interestingly, PAO1 colonies were reduced in PAO1-infected NHNE cells treated with rhIL-17C, and supernatants from NHNE cells treated with rhIL-17C also exhibited decreased PAO1 colonies. We found that the siderophore activity of PAO1 was significantly reduced in the supernatants of NHNE cells treated with rhIL-17C where LCN2 expression was highly elevated. Our findings indicate that IL-17C mediates an antibacterial effect against PAO1 by inhibiting siderophore activity in nasal epithelium. We propose that IL-17C might be an efficient mediator to suppress PAO1 infection through disturbing iron absorption of PAO1 in nasal epithelium.

The Construction of Carbon Nanotubes Containing an Anti-Bacterial Chemical Component and its Effect on MDR and XDR Isolates of Pseudomonas Aeruginosa

Background

Pseudomonas aeruginosa is an opportunistic human pathogen that causes severe acute and chronic nosocomial infections, especially in immunocompromised burn patients. and can lead to severe mortality and morbidity. The emergence of antibiotic resistant P. aeruginosa infections has created significant challenges in treating these patients. A potential alternative treatment for antibiotic resistant pathogens includes the use of carbon nanotubes (CNTs), which have received considerable attention due to their potent antibacterial activity. The aim of this study was to construct a novel CNT containing an anti-bacterial chemical component to effectively combat drug resistant P. aeruginosa infections.

Methods

In this study, a novel chemical component was synthesized and coated the CNT. The antimicrobial effects were then evaluated on MDR, XDR, and PDR strains of P. aeruginosa isolated from burn patients. Antibiotic susceptibility was evaluated using the disk diffusion test and minimum inhibitory concentration (MIC) testing. In order to determine the potential cytotoxicity, an MTT assay was performed on Human Dermal Fibroblasts. The effect of treatment on the expression of wound healing genes was analyzed via qRT-PCR.

Results

Experimental data indicates that our CNT coated chemical compound had antibacterial properties, negligible cytotoxicity, and could accelerate the wound healing process.

Conclusion

Given the antibacterial properties of our CNT chemical compound, it has the potential to treat and reduce the occurrence of multi-drug resistant P. aeruginosa burn wound infections and aid in wound healing by turning on genes (VEGFA, EGF and PDEGF) involved in the wound healing process.

The art of suicidal molecular seduction for targeting drug resistance

The development of drug resistance is one of the most significant challenges of the current century in the pharmaceutical industry. Superinfections, cancer chemoresistance, and resistance observed in many non-infectious diseases are nullifying the efforts and monetary supplies, put in the advent of new drug molecules. Millions of people die because of this drug resistance developed gradually through extensive use of the drugs. Inherently, some drugs are less prone to become ineffective by drug resistance than others. Covalent inhibitors bind to their targets via a biologically permanent bound with their cognate receptor and therefore display more potent inhibiting characteristics. Suicide inhibitors or mechanism-based inhibitors are one of the covalent inhibitors, which require a pre-activation step by their targeting enzyme. This step accrues their selectivity and specificity with respect to other covalent inhibitors. After that pre-activation step, they produce an analogue of the transition state of the catalytic enzyme, which is practically incapable of dissociating from the enzyme. Suicide inhibitors, due to their high intrinsic affinity toward the related enzyme, are resistant to many mechanisms involved in the development of drug resistance and can be regarded as one of the enemies of this scientific hurdle. These inhibitors compete even with monoclonal antibodies in terms of their cost-effectiveness and efficacy.