Spread of extensively resistant VIM-2-positive ST235 Pseudomonas aeruginosa in Belarus, Kazakhstan, and Russia: a longitudinal epidemiological and clinical study

Tracing the origin of NDM-1-producing and extensively drug-resistant Pseudomonas aeruginosa ST357 in the Netherlands

BACKGROUND

In the hospital environment, carbapenemase-producing Pseudomonas aeruginosa (CPPA) may lead to fatal patient infections. However, the transmission routes of CPPA often remain unknown. Therefore, this case study aimed to trace the origin of CPPA ST357, which caused a hospital-acquired pneumonia in a repatriated critically ill patient suffering from Guillain-Barré Syndrome in 2023.

METHODS

Antimicrobial susceptibility of the CPPA isolate for 30 single and combination therapies was determined by disk-diffusion, Etest or broth microdilution. Whole-genome sequencing was performed for three case CPPA isolates (one patient and two sinks) and four distinct CPPA ST357 patient isolates received in the Dutch CPPA surveillance program. Furthermore, 193 international P. aeruginosa ST357 assemblies were collected via three genome repositories and analyzed using whole-genome multi-locus sequence typing in combination with antimicrobial resistance gene (ARG) characterization.

RESULTS

A Dutch patient who carried NDM-1-producing CPPA was transferred from Kenya to the Netherlands, with subsequent dissemination of CPPA isolates to the local sinks within a month after admission. The CPPA case isolates presented an extensively drug-resistant phenotype, with susceptibility only for colistin and cefiderocol-fosfomycin. Phylogenetic analysis showed considerable variation in allelic distances (mean = 150, max = 527 alleles) among the ST357 isolates from Asia (n = 92), Europe (n = 58), Africa (n = 21), America (n = 16), Oceania (n = 2) and unregistered regions (n = 4). However, the case isolates (n = 3) and additional Dutch patient surveillance program isolates (n = 2) were located in a sub-clade of isolates from Kenya (n = 17; varying 15-49 alleles), the United States (n = 7; 21-115 alleles) and other countries (n = 6; 14-121 alleles). This was consistent with previous hospitalization in Kenya of 2/3 Dutch patients. Additionally, over half of the isolates (20/35) in this sub-clade presented an identical resistome with 9/17 Kenyan, 5/5 Dutch, 4/7 United States and 2/6 other countries, which were characterized by the blaNDM-1, aph(3')-VI, ARR-3 and cmlA1 ARGs.

CONCLUSION

This study presents an extensively-drug resistant subclone of NDM-producing P. aeruginosa ST357 with a unique resistome which was introduced to the Netherlands via repatriation of critically ill patients from Kenya. Therefore, the monitoring of repatriated patients for CPPA in conjunction with vigilance for the risk of environmental contamination is advisable to detect and prevent further dissemination.

Extensively Drug-Resistant Pseudomonas aeruginosa Outbreak Associated With Artificial Tears

BACKGROUND

Carbapenemase-producing, carbapenem-resistant Pseudomonas aeruginosa (CP-CRPA) are extensively drug-resistant bacteria. We investigated the source of a multistate CP-CRPA outbreak.

METHODS

Cases were defined as a US patient's first isolation of P. aeruginosa sequence type 1203 with carbapenemase gene blaVIM-80 and cephalosporinase gene blaGES-9 from any specimen source collected and reported to the Centers for Disease Control and Prevention during 1 January 2022-15 May 2023. We conducted a 1:1 matched case-control study at the post-acute care facility with the most cases, assessed exposures associated with case status for all case-patients, and tested products for bacterial contamination.

RESULTS

We identified 81 case-patients from 18 states, 27 of whom were identified through surveillance cultures. Four (7%) of 54 case-patients with clinical cultures died within 30 days of culture collection, and 4 (22%) of 18 with eye infections underwent enucleation. In the case-control study, case-patients had increased odds of receiving artificial tears versus controls (crude matched OR, 5.0; 95% CI, 1.1-22.8). Overall, artificial tears use was reported by 61 (87%) of 70 case-patients with information; 43 (77%) of 56 case-patients with brand information reported use of Brand A, an imported, preservative-free, over-the-counter (OTC) product. Bacteria isolated from opened and unopened bottles of Brand A were genetically related to patient isolates. Food and Drug Administration inspection of the manufacturing plant identified likely sources of contamination.

CONCLUSIONS

A manufactured medical product serving as the vehicle for carbapenemase-producing organisms is unprecedented in the United States. The clinical impacts from this outbreak underscore the need for improved requirements for US OTC product importers.

Unveiling the microevolution of antimicrobial resistance in selected Pseudomonas aeruginosa isolates from Egyptian healthcare settings: A genomic approach

The incidence of Pseudomonas aeruginosa infections in healthcare environments, particularly in low-and middle-income countries, is on the rise. The purpose of this study was to provide comprehensive genomic insights into thirteen P. aeruginosa isolates obtained from Egyptian healthcare settings. Phenotypic analysis of the antimicrobial resistance profile and biofilm formation were performed using minimum inhibitory concentration and microtiter plate assay, respectively. Whole genome sequencing was employed to identify sequence typing, resistome, virulome, and mobile genetic elements. Our findings indicate that 92.3% of the isolates were classified as extensively drug-resistant, with 53.85% of these demonstrating strong biofilm production capabilities. The predominant clone observed in the study was ST773, followed by ST235, both of which were associated with the O11 serotype. Core genome multi-locus sequence typing comparison of these clones with global isolates suggested their potential global expansion and adaptation. A significant portion of the isolates harbored Col plasmids and various MGEs, all of which were linked to antimicrobial resistance genes. Single nucleotide polymorphisms in different genes were associated with the development of antimicrobial resistance in these isolates. In conclusion, this pilot study underscores the prevalence of extensively drug-resistant P. aeruginosa isolates and emphasizes the role of horizontal gene transfer facilitated by a diverse array of mobile genetic elements within various clones. Furthermore, specific insertion sequences and mutations were found to be associated with antibiotic resistance.

Pseudomonas aeruginosa antibiotic susceptibility profiles, genomic epidemiology and resistance mechanisms: a nation-wide five-year time lapse analysis

Background

Pseudomonas aeruginosa healthcare-associated infections are one of the top antimicrobial resistance threats world-wide. In order to analyze the current trends, we performed a Spanish nation-wide high-resolution analysis of the susceptibility profiles, the genomic epidemiology and the resistome of P. aeruginosa over a five-year time lapse.

Methods

A total of 3.180 nonduplicated P. aeruginosa clinical isolates from two Spanish nation-wide surveys performed in October 2017 and 2022 were analyzed. MICs of 13 antipseudomonals were determined by ISO-EUCAST. Multidrug resistance (MDR)/extensively drug resistance (XDR)/difficult to treat resistance (DTR)/pandrug resistance (PDR) profiles were defined following established criteria. All XDR/DTR isolates were subjected to whole genome sequencing (WGS).

Findings

A decrease in resistance to all tested antibiotics, including older and newer antimicrobials, was observed in 2022 vs 2017. Likewise, a major reduction of XDR (15.2% vs 5.9%) and DTR (4.2 vs 2.1%) profiles was evidenced, and even more patent among ICU isolates [XDR (26.0% vs 6.0%) and DTR (8.9% vs 2.6%)] (p < 0.001). The prevalence of Extended-spectrum β-lactamase/carbapenemase production was slightly lower in 2022 (2.1%. vs 3.1%, p = 0.064). However, there was a significant increase in the proportion of carbapenemase production among carbapenem-resistant strains (29.4% vs 18.1%, p = 0.0246). While ST175 was still the most frequent clone among XDR, a slight reduction in its prevalence was noted (35.9% vs 45.5%, p = 0.106) as opposed to ST235 which increased significantly (24.3% vs 12.3%, p = 0.0062).

Interpretation

While the generalized decrease in P. aeruginosa resistance, linked to a major reduction in the prevalence of XDR strains, is encouraging, the negative counterpart is the increase in the proportion of XDR strains producing carbapenemases, associated to the significant advance of the concerning world-wide disseminated hypervirulent high-risk clone ST235. Continued high-resolution surveillance, integrating phenotypic and genomic data, is necessary for understanding resistance trends and analyzing the impact of national plans on antimicrobial resistance.

Funding

MSD and the Instituto de Salud Carlos III, Ministerio de Ciencia e Innovación and Unión Europea-NextGenerationEU.

Spread of multidrug-resistant Pseudomonas aeruginosa in animal-derived foods in Beijing, China

Pseudomonas aeruginosa is the most common bacterium occurred in nosocomial infections and is also an important indicator of food spoilage. The worldwide spread of multidrug resistant (MDR) P. aeruginosa is threatening public health. However, the prevalence and spread of MDR P. aeruginosa through the food chain is little referred under the One Health perspective. Here, we collected a total of 259 animal-derived foods (168 chicken and 91 pork) from 16 supermarkets and farmer's markets in six regions of Beijing, China. The prevalence of P. aeruginosa in chicken and pork was 42.1 %. The phenotypic antimicrobial susceptibility testing showed that 69.7 % of isolates were MDR, and isolates from Chaoyang district exhibited a higher resistance rate compared to that from Xicheng district (p < 0.05). P. aeruginosa isolates exhibited high levels of resistance against β-lactams (91.7 %), cephalosporins (29.4 %), and carbapenems (22.9 %). Interestingly, none of strains showed resistance to amikacin. Whole-genome sequencing showed that all isolates carried various kinds of antimicrobial resistance genes (ARGs) and virulence genes (VGs), especially for blaOXA genes and phz genes. Multilocus sequence typing (MLST) analysis indicated that ST111 (12.8 %) was the most predominant ST. Notably, the emergence of ST697 clones in food-borne P. aeruginosa was firstly reported. In addition, the toxin pyocyanin was detected in 79.8 % of P. aeruginosa strains. These findings help to decipher the prevalence and the strong toxigenic ability of MDR P. aeruginosa from animal-derived foods and highlight the effective supervision of animal-derived food hygiene should be strengthened to prevent the spread of ARGs in a One Health strategy.

The Prevalence of Metallo-Beta-Lactamese-(MβL)-Producing Pseudomonas aeruginosa Isolates in Brazil: A Systematic Review and Meta-Analysis

The purpose of the current study is to describe the prevalence of Pseudomonas aeruginosa (PA)-producing MβL among Brazilian isolates and the frequency of blaSPM-1 in MβL-PA-producing isolates. From January 2009 to August 2023, we carried out an investigation on this subject in the internet databases SciELO, PubMed, Science Direct, and LILACS. A total of 20 papers that met the eligibility requirements were chosen by comprehensive meta-analysis software v2.2 for data retrieval and analysis by one meta-analysis using a fixed-effects model for the two investigations. The prevalence of MβL-producing P. aeruginosa was 35.8% or 0.358 (95% CI = 0.324-0.393). The studies' differences were significantly different from one another (x2 = 243.15; p < 0.001; I2 = 92.18%), so they were divided into subgroups based on Brazilian regions. There was indication of asymmetry in the meta-analyses' publishing bias funnel plot; so, a meta-regression was conducted by the study's publication year. According to the findings of Begg's test, no discernible publishing bias was found. blaSPM-1 prevalence was estimated at 66.9% or 0.669 in MβL-PA isolates (95% CI = 0.593-0.738). The analysis of this one showed an average heterogeneity (x2 = 90.93; p < 0.001; I2 = 80.20%). According to the results of Begg's test and a funnel plot, no discernible publishing bias was found. The research showed that MβL-P. aeruginosa and SPM-1 isolates were relatively common among individuals in Brazil. P. aeruginosa and other opportunistic bacteria are spreading quickly and causing severe infections, so efforts are needed to pinpoint risk factors, reservoirs, transmission pathways, and the origin of infection.

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.

In vitro activity of cefiderocol against MBL-producing Gram-negative bacteria collected in North America and Europe in five consecutive annual multinational SIDERO-WT surveillance studies (2014-2019)

OBJECTIVES

To evaluate the in vitro antibacterial activity of cefiderocol, a siderophore cephalosporin against MBL-producing clinical isolates.

METHODS

MBL-producing strains were selected from clinical isolates of Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii complex collected in North America and Europe in five consecutive annual multinational SIDERO-WT surveillance studies from 2014 to 2019. MICs of cefiderocol and comparator agents were determined by the broth microdilution method according to the CLSI guideline.

RESULTS

A total of 452 MBL-producing strains consisting of 200 Enterobacterales, 227 P. aeruginosa and 25 A. baumannii complex were identified. The highest number of MBL-producing Enterobacterales strains were detected in Greece. MBL-producing strains of both P. aeruginosa and A. baumannii complex were isolated most frequently in Russia. For Enterobacterales, 91.5% or 67.5% of MBL-producing strains had cefiderocol MIC values ≤4 mg/L (CLSI susceptibility breakpoint) or ≤2 mg/L (EUCAST susceptibility breakpoint), respectively. All MIC values of cefiderocol for MBL-producing P. aeruginosa strains were ≤4 mg/L (CLSI susceptibility breakpoint), and 97.4% of them had cefiderocol MIC values ≤2 mg/L (EUCAST susceptibility breakpoint). For A. baumannii complex, 60.0% or 44.0% of MBL-producing strains had cefiderocol MIC values ≤4 mg/L (CLSI susceptibility breakpoint) or ≤2 mg/L (EUCAST pharmacokinetic-pharmacodynamic susceptibility breakpoint), respectively. Against all types of MBL-producing strains, MIC distribution curves of cefiderocol were located in the lowest numerical values, compared with other β-lactams and β-lactam/β-lactamase inhibitor combinations tested and ciprofloxacin.

CONCLUSIONS

Although the types of MBL-producing strains isolated by country varied, cefiderocol showed potent in vitro activity against all types of MBL-producing Gram-negative bacteria regardless of the bacterial species.

Insight into phylogenomic bias of blaVIM-2 or blaNDM-1 dissemination amongst carbapenem-resistant Pseudomonas aeruginosa

OBJECTIVES

Pseudomonas aeruginosa (P. aeruginosa) are ubiquitous opportunistic pathogens that combine intrinsic and acquired multidrug resistance phenotypes. Due to different types of acquired genes, carbapenem resistance has been expanding in this species. This study hypothesised that the spread of carbapenem resistance among P. aeruginosa is influenced by phylogenomic features, being distinct for different genes.

METHODS

To test this hypothesis, the genomes of P. aeruginosa harbouring blaVIM-2 or blaNDM-1 genes were compared. The blaVIM-2 gene was selected because, although frequent, it is almost restricted to this species and blaNDM-1 gene due to its wide interspecies distribution. A group of genomes harbouring the genes blaVIM-2 (n = 116) or blaNDM-1 (n = 27), available in GenBank, was characterised based on core phylogenomic analysis, functional categories in the accessory genome and mobile genetic elements flanking the selected genes.

RESULTS

Most blaVIM-2 gene hosts belonged to multilocus sequence types (ST) ST111 (n = 32 of 116) and ST233 (n = 27 of 116) and were reported in Europe (n = 75 of 116). The blaNDM-1 gene hosts were distributed by different STs (ST38, ST773, ST235, ST357 and ST654), frequently from Asia (n = 11 of 27). Significant differences in the prevalence of functional protein/enzyme annotations per number of accessory genomes were observed between blaVIM-2+ and blaNDM-1+. The blaVIM-2 gene was frequently inserted in the Tn402-like and Tn21 transposons family and rarely in IS6100, while blaNDM-1 gene was preferentially flanked by ISAba125 and bleMBL genes or associated with IS91 insertion sequence.

CONCLUSION

The hypothesis that carbapenem resistance gene acquisition is not random among phylogenomic lineages was confirmed, suggesting the importance of phylogeny in the dissemination of antibiotic resistance genes.

The primary pharmacology of ceftazidime/avibactam: resistance in vitro

This article reviews resistance to ceftazidime/avibactam as an aspect of its primary pharmacology, linked thematically with recent reviews of the basic in vitro and in vivo translational biology of the combination (J Antimicrob Chemother 2022; 77: 2321-40 and 2341-52). In Enterobacterales or Pseudomonas aeruginosa, single-step exposures to 8×  MIC of ceftazidime/avibactam yielded frequencies of resistance from <∼0.5 × 10-9 to 2-8 × 10-9, depending on the host strain and the β-lactamase harboured. β-Lactamase structural gene mutations mostly affected the avibactam binding site through changes in the Ω-loop: e.g. Asp179Tyr (D179Y) in KPC-2. Other mutations included ones proposed to reduce the permeability to ceftazidime and/or avibactam through changes in outer membrane structure, up-regulated efflux, or both. The existence, or otherwise, of cross-resistance between ceftazidime/avibactam and other antibacterial agents was also reviewed as a key element of the preclinical primary pharmacology of the new agent. Cross-resistance between ceftazidime/avibactam and other β-lactam-based antibacterial agents was caused by MBLs. Mechanism-based cross-resistance was not observed between ceftazidime/avibactam and fluoroquinolones, aminoglycosides or colistin. A low level of general co-resistance to ceftazidime/avibactam was observed in MDR Enterobacterales and P. aeruginosa. For example, among 2821 MDR Klebsiella spp., 3.4% were resistant to ceftazidime/avibactam, in contrast to 0.07% of 8177 non-MDR isolates. Much of this was caused by possession of MBLs. Among 1151 MDR, XDR and pandrug-resistant isolates of P. aeruginosa from the USA, 11.1% were resistant to ceftazidime/avibactam, in contrast to 3.0% of 7452 unselected isolates. In this case, the decreased proportion susceptible was not due to MBLs.

Prevalence and microbiological and genetic characteristics of multidrug-resistant Pseudomonas aeruginosa over three years in Qatar

OBJECTIVES

Antimicrobial resistance (AMR) is a global priority with significant clinical and economic consequences. Multidrug-resistant (MDR) Pseudomonas aeruginosa is one of the major pathogens associated with significant morbidity and mortality. In healthcare settings, the evaluation of prevalence, microbiological characteristics, as well as mechanisms of resistance is of paramount importance to overcome associated challenges.

METHODS

Consecutive clinical specimens of P. aeruginosa were collected prospectively from 5 acute-care and specialized hospitals between October 2014 and September 2017, including microbiological, clinical characteristics and outcomes. Identification and antimicrobial susceptibility test were performed using the BD Phoenix identification and susceptibility testing system, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS), and minimum inhibitory concentration (MIC) test strips. Overall, 78 selected MDR P. aeruginosa isolates were processed for whole-genome sequencing (WGS).

RESULTS

The overall prevalence of MDR P. aeruginosa isolates was 5.9% (525 of 8,892) and showed a decreasing trend; 95% of cases were hospital acquired and 44.8% were from respiratory samples. MDR P. aeruginosa demonstrated >86% resistance to cefepime, ciprofloxacin, meropenem, and piperacillin-tazobactam but 97.5% susceptibility to colistin. WGS revealed 29 different sequence types: 20.5% ST235, 10.3% ST357, 7.7% ST389, and 7.7% ST1284. ST233 was associated with bloodstream infections and increased 30-day mortality. All ST389 isolates were obtained from patients with cystic fibrosis. Encoded exotoxin genes were detected in 96.2% of isolates.

CONCLUSIONS

MDR P. aeruginosa isolated from clinical specimens from Qatar has significant resistance to most agents, with a decreasing trend that should be explored further. Genomic analysis revealed the dominance of 5 main clonal clusters associated with mortality and bloodstream infections. Microbiological and genomic monitoring of MDR P. aeruginosa has enhanced our understanding of AMR in Qatar.

The primary pharmacology of ceftazidime/avibactam: in vitro translational biology

Previous reviews of ceftazidime/avibactam have focused on in vitro molecular enzymology and microbiology or the clinically associated properties of the combination. Here we take a different approach. We initiate a series of linked reviews that analyse research on the combination that built the primary pharmacology data required to support the clinical and business risk decisions to perform randomized controlled Phase 3 clinical trials, and the additional microbiological research that was added to the above, and the safety and chemical manufacturing and controls data, that constituted successful regulatory licensing applications for ceftazidime/avibactam in multiple countries, including the USA and the EU. The aim of the series is to provide both a source of reference for clinicians and microbiologists to be able to use ceftazidime/avibactam to its best advantage for patients, but also a case study of bringing a novel β-lactamase inhibitor (in combination with an established β-lactam) through the microbiological aspects of clinical development and regulatory applications, updated finally with a review of resistance occurring in patients under treatment. This first article reviews the biochemistry, structural biology and basic microbiology of the combination, showing that avibactam inhibits the great majority of serine-dependent β-lactamases in Enterobacterales and Pseudomonas aeruginosa to restore the in vitro antibacterial activity of ceftazidime. Translation to efficacy against infections in vivo is reviewed in the second co-published article, Nichols et al. (J Antimicrob Chemother 2022; dkac172).

Bacteriophage-Loaded Poly(lactic-co-glycolic acid) Microparticles Mitigate Staphylococcus aureus Infection and Cocultures of Staphylococcus aureus and Pseudomonas aeruginosa

Lung infections caused by Gram-positive Staphylococcus aureus (S. aureus) and coinfections caused by S. aureus and Gram-negative Pseudomonas aeruginosa (P. aeruginosa) are challenging to treat, especially with the rise in the number of antibiotic-resistant strains of these pathogens. Bacteriophage (phage) are bacteria-specific viruses that can infect and lyse bacteria, providing a potentially effective therapy for bacterial infections. However, the development of bacteriophage therapy is impeded by limited suitable biomaterials that can facilitate effective delivery of phage to the lung. Here, the ability of porous microparticles engineered from poly(lactic-co-glycolic acid) (PLGA), a biodegradable polyester, to effectively deliver phage to the lung, is demonstrated. The phage-loaded microparticles (phage-MPs) display potent antimicrobial efficacy against various strains of S. aureus in vitro and in vivo, and arrest the growth of a clinical isolate of S. aureus in the presence of sputum supernatant obtained from cystic fibrosis patients. Moreover, phage-MPs efficiently mitigate in vitro cocultures of S. aureus and P. aeruginosa and display excellent cytocompatibility with human lung epithelial cells. Therefore, phage-MPs represents a promising therapy to treat bacterial lung infection.

Evaluation of Blood-Brain-Barrier Permeability, Neurotoxicity, and Potential Cognitive Impairment by Pseudomonas aeruginosa’s Virulence Factor Pyocyanin

Pyocyanin (PCN) is a redox-active secondary metabolite produced by Pseudomonas aeruginosa as its primary virulence factor. Several studies have reported the cytotoxic potential of PCN and its role during infection establishment and progression. Considering its ability to diffuse through biological membranes, it is hypothesized that PCN can gain entry into the brain and induce oxidative stress across the blood-brain barrier (BBB), ultimately contributing towards reactive oxygen species (ROS) mediated neurodegeneration. Potential roles of PCN in the central nervous system (CNS) have never been evaluated, hence the study aimed to evaluate PCN's probable penetration into CNS through blood-brain barrier (BBB) using both in silico and in vivo (Balb/c mice) approaches and the impact of ROS generation via commonly used tests: Morris water maze test, novel object recognition, elevated plus maze test, and tail suspension test. Furthermore, evidence for ROS generation in the brain was assessed using glutathione S-transferase assay. PCN demonstrated BBB permeability albeit in minute quantities. A significant hike was observed in ROS generation (P < 0.0001) along with changes in behavior indicating PCN permeability across BBB and potentially affecting cognitive functions. This is the first study exploring the potential role of PCN in influencing the cognitive functions of test animals.

Empiric Treatment in HAP/VAP: “Don’t You Want to Take a Leap of Faith?”

Ventilator-associated pneumonia is a frequent cause of ICU-acquired infections. These infections are associated with high morbidity and mortality. The increase in antibiotic resistance, particularly among Gram-negative bacilli, makes the choice of empiric antibiotic therapy complex for physicians. Multidrug-resistant organisms (MDROs) related infections are associated with a high risk of initial therapeutic inadequacy. It is, therefore, necessary to quickly identify the bacterial species involved and their susceptibility to antibiotics. New diagnostic tools have recently been commercialized to assist in the management of these infections. Moreover, the recent enrichment of the therapeutic arsenal effective on Gram-negative bacilli raises the question of their place in the therapeutic management of these infections. Most national and international guidelines recommend limiting their use to microbiologically documented infections. However, many clinical situations and, in particular, the knowledge of digestive or respiratory carriage by MDROs should lead to the discussion of the use of these new molecules, especially the new combinations with beta-lactamase inhibitors in empirical therapy. In this review, we present the current epidemiological data, particularly in terms of MDRO, as well as the clinical and microbiological elements that may be taken into account in the discussion of empirical antibiotic therapy for patients managed for ventilator-associated pneumonia.

Pseudomonas aeruginosa Pneumonia: Evolution of Antimicrobial Resistance and Implications for Therapy

Pseudomonas aeruginosa (PA), a non-lactose-fermenting gram-negative bacillus, is a common cause of nosocomial infections in critically ill or debilitated patients, particularly ventilator-associated pneumonia (VAP), and infections of urinary tract, intra-abdominal, wounds, skin/soft tissue, and bloodstream. PA rarely affects healthy individuals, but may cause serious infections in patients with chronic structural lung disease, comorbidities, advanced age, impaired immune defenses, or with medical devices (e.g., urinary or intravascular catheters, foreign bodies). Treatment of pseudomonal infections is difficult, as PA is intrinsically resistant to multiple antimicrobials, and may acquire new resistance determinants even while on antimicrobial therapy. Mortality associated with pseudomonal VAP or bacteremias is high (> 35%) and optimal therapy is controversial. Over the past three decades, antimicrobial resistance (AMR) among PA has escalated globally, via dissemination of several international multidrug resistant "epidemic" clones. We discuss the importance of PA as a cause of pneumonia including health care-associated pneumonia, hospital-acquired pneumonia, VAP, the emergence of AMR to this pathogen, and approaches to therapy (both empirical and definitive).

Extensively Drug-Resistant Carbapenemase-Producing Pseudomonas aeruginosa and Medical Tourism from the United States to Mexico, 2018-2019

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) producing the Verona integron‒encoded metallo-β-lactamase (VIM) are highly antimicrobial drug-resistant pathogens that are uncommon in the United States. We investigated the source of VIM-CRPA among US medical tourists who underwent bariatric surgery in Tijuana, Mexico. Cases were defined as isolation of VIM-CRPA or CRPA from a patient who had an elective invasive medical procedure in Mexico during January 2018‒December 2019 and within 45 days before specimen collection. Whole-genome sequencing of isolates was performed. Thirty-eight case-patients were identified in 18 states; 31 were operated on by surgeon 1, most frequently at facility A (27/31 patients). Whole-genome sequencing identified isolates linked to surgeon 1 were closely related and distinct from isolates linked to other surgeons in Tijuana. Facility A closed in March 2019. US patients and providers should acknowledge the risk for colonization or infection after medical tourism with highly drug-resistant pathogens uncommon in the United States.

Biomaterial-based delivery of antimicrobial therapies for the treatment of bacterial infections

The rise in antibiotic-resistant bacteria, including strains that are resistant to last-resort antibiotics, and the limited ability of antibiotics to eradicate biofilms, have necessitated the development of alternative antibacterial therapeutics. Antibacterial biomaterials, such as polycationic polymers, and biomaterial-assisted delivery of non-antibiotic therapeutics, such as bacteriophages, antimicrobial peptides and antimicrobial enzymes, have improved our ability to treat antibiotic-resistant and recurring infections. Biomaterials not only allow targeted delivery of multiple agents, but also sustained release at the infection site, thereby reducing potential systemic adverse effects. In this Review, we discuss biomaterial-based non-antibiotic antibacterial therapies for the treatment of community- and hospital-acquired infectious diseases, with a focus in in vivo results. We highlight the translational potential of different biomaterial-based strategies, and provide a perspective on the challenges associated with their clinical translation. Finally, we discuss the future scope of biomaterial-assisted antibacterial therapies.

WEB SUMMARY

The development of antibiotic tolerance and resistance has demanded the search for alternative antibacterial therapies. This Review discusses antibacterial biomaterials and biomaterial-assisted delivery of non-antibiotic therapeutics for the treatment of bacterial infectious diseases, with a focus on clinical translation.

Antimicrobial Resistance and Type III Secretion System Virulotypes of Pseudomonas aeruginosa Isolates from Dogs and Cats in Primary Veterinary Hospitals in Japan: Identification of the International High-Risk Clone Sequence Type 235

This study aimed to investigate the current trends in antimicrobial resistance among Pseudomonas aeruginosa clinical isolates of canine and feline origin and the prevalence of their sequence types (STs) and type III secretion system (T3SS) virulotypes, which remains unknown in Japan. A total of 240 nonduplicate clinical isolates of P. aeruginosa from dogs (n = 206) and cats (n = 34) collected from 152 primary care animal hospitals between August 2017 and October 2019 were examined. PCR detection of T3SS genes (exoU and exoS) and carbapenemase genes, multilocus sequence typing, and whole-genome sequencing of the representative carbapenem-resistant isolates were performed. Resistance rates to imipenem and meropenem were 6.67% and 2.08%, respectively. A high resistance rate (17.92%) was encountered with ciprofloxacin. The exoU−/exoS+ was the predominant T3SS virulotype (195 isolates, 81.3%), followed by exoU+/exoS− (35 isolates, 14.6%), exoU−/exoS− (7 isolates, 2.9%), and exoU+/exoS+ (3 isolates, 1.3%). A high frequency of the high-risk clones ST235 and clonal complex 235 (CC 235) (28.9%), followed by ST357 (21.1%), were noted among these 38 exoU+ isolates. Seventeen carbapenem-resistant isolates comprising 2 exoU+ isolates, including an ST235 isolate, and 15 exoU−/exoS+ isolates belonging to non-ST235/CC235 were detected, of which all were carbapenemase negative. Different combinations of mutations among oprD, efflux pump regulatory genes, and AmpC β-lactamase regulatory genes were identified among representative isolates with high-level resistance to imipenem. This study emphasizes the occurrence of ST235 isolates among companion animals, which may represent a threat to public health because of the ability of this clone to acquire and spread resistance elements, including carbapenemase genes.

IMPORTANCEPseudomonas aeruginosa is an environmentally ubiquitous and important opportunistic human pathogen responsible for life-threatening health care-associated infections. Because of its extensive repertoire of virulence determinants and intrinsic and acquired resistance mechanisms, the organism could be one of the most clinically and epidemiologically important causes of morbidity and mortality. In recent years, worldwide spreading of multidrug-resistant high-risk clones, particularly sequence type 235 (ST235), has become a serious public health threat. Companion animals which share much of their living environment with humans could be important reservoirs and spreaders of antimicrobial-resistant bacteria and resistance genes of clinical importance in humans, such as extended-spectrum β-lactamase-producing Enterobacterales and methicillin-resistant Staphylococcus aureus. However, antimicrobial resistance, virulence, and genotyping of P. aeruginosa in companion animals remain largely unknown. This work sheds light on the potential spread of high-risk clones in companion animals.

CRISPR Element Patterns vs. Pathoadaptability of Clinical Pseudomonas aeruginosa Isolates from a Medical Center in Moscow, Russia

Pseudomonas aeruginosa is a member of the ESKAPE opportunistic pathogen group, which includes six species of the most dangerous microbes. This pathogen is characterized by the rapid acquisition of antimicrobial resistance, thus causing major healthcare concerns. This study presents a comprehensive analysis of clinical P. aeruginosa isolates based on whole-genome sequencing data. The isolate collection studied was characterized by a variety of clonal lineages with a domination of high-risk epidemic clones and different CRISPR/Cas element patterns. This is the first report on the coexistence of two and even three different types of CRISPR/Cas systems simultaneously in Russian clinical strains of P. aeruginosa. The data include molecular typing and genotypic antibiotic resistance determination, as well as the phylogenetic analysis of the full-length cas gene and anti-CRISPR genes sequences, predicted prophage sequences, and conducted a detailed CRISPR array analysis. The differences between the isolates carrying different types and quantities of CRISPR/Cas systems were investigated. The pattern of virulence factors in P. aeruginosa isolates lacking putative CRISPR/Cas systems significantly differed from that of samples with single or multiple putative CRISPR/Cas systems. We found significant correlations between the numbers of prophage sequences, antibiotic resistance genes, and virulence genes in P. aeruginosa isolates with different patterns of CRISPR/Cas-elements. We believe that the data presented will contribute to further investigations in the field of bacterial pathoadaptability, including antimicrobial resistance and the role of CRISPR/Cas systems in the plasticity of the P. aeruginosa genome.

Genomic surveillance of Pseudomonas aeruginosa in the Philippines, 2013-2014

Pseudomonas aeruginosa is an opportunistic pathogen that often causes nosocomial infections resistant to treatment. Rates of antimicrobial resistance (AMR) are increasing, as are rates of multidrug-resistant (MDR) and possible extensively drug-resistant (XDR) infections. Our objective was to characterize the molecular epidemiology and AMR mechanisms of this pathogen.

We sequenced the whole genome for each of 176 P. aeruginosa isolates collected in the Philippines in 2013–2014; derived the multilocus sequence type (MLST), presence of AMR determinants and relatedness between isolates; and determined concordance between phenotypic and genotypic resistance.

Carbapenem resistance was associated with loss of function of the OprD porin and acquisition of the metallo-β-lactamase (MBL) gene bla^VIM. Concordance between phenotypic and genotypic resistance was 93.27% overall for six antibiotics in three classes, but varied among aminoglycosides. The population of P. aeruginosa was diverse, with clonal expansions of XDR genomes belonging to MLSTs ST235, ST244, ST309 and ST773. We found evidence of persistence or reintroduction of the predominant clone ST235 in one hospital, and of transfer between hospitals.

Most of the ST235 genomes formed a distinct lineage from global genomes, thus raising the possibility that they may be unique to the Philippines. In addition, long-read sequencing of one representative XDR ST235 isolate identified an integron carrying multiple resistance genes (including bla^VIM-2), with differences in gene composition and synteny from the P. aeruginosa class 1 integrons described previously.

The survey bridges the gap in genomic data from the Western Pacific Region and will be useful for ongoing surveillance; it also highlights the importance of curtailing the spread of ST235 within the Philippines.

Molecular and genomic epidemiology of VIM/IMP-like metallo-β-lactamase-producing Pseudomonas aeruginosa genotypes in Poland

OBJECTIVES

To identify key factors of the expansion of metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa (MPPA) in Poland, focusing on the role of clonal epidemic(s).

METHODS

MPPA isolates were typed by PFGE, followed by MLST. blaVIM/IMP MBL genes were amplified and sequenced within class 1 integrons. Their location was assessed by S1 nuclease-hybridization assays. Short-read WGS was performed, and genomes were subjected to SNP-based phylogenetic and resistome analyses.

RESULTS

Of 1314 MPPA isolates collected in 2005-15 from 212 hospitals, 454 representatives were selected. The isolates belonged to 120 pulsotypes and 52 STs, of which ST235 (∼31%), ST111 (∼17%), ST273 (∼16%) and ST654 (∼9%) prevailed, followed by ST244, ST17, ST395, ST175 and ST1567. The isolates produced seven VIM variants (97.5%) and four IMPs encoded by 46 integrons, most of which were observed only or mainly in Poland. Around 60% of the isolates resulted from (inter)regional clonal outbreaks of 10 individual ST235, ST111, ST273 and ST654 genotypes. The phylogenetic analysis of 163 genomes revealed heterogeneity of ST235 and ST111 populations, arising from transnational circulation and on-site differentiation of several clades/branches. Contrarily, ST273 and ST654 formed relatively homogeneous and apparently Poland-specific lineages, and a unique ST273 genotype with integron In249 was the most expansive organism.

CONCLUSIONS

Together with a previous report on self-transmissible In461-carrying IncP-2-type plasmids, this study revealed the molecular/genomic background of the rapid MPPA increase in Poland in 2001-15, evidencing multi-clonal spread as its leading factor. Numerous novel/specific MPPA characteristics were identified.

Longitudinal analysis of ESBL and carbapenemase carriage among Enterobacterales and Pseudomonas aeruginosa isolates collected in Europe as part of the International Network for Optimal Resistance Monitoring (INFORM) global surveillance programme, 2013-17

OBJECTIVES

To determine the spread of ESBLs and carbapenemases in Enterobacterales and Pseudomonas aeruginosa in Europe.

METHODS

45 335 Gram-negative bacilli were collected in 18 European countries as part of the International Network for Optimal Resistance Monitoring (INFORM) global surveillance programme from 2013 to 2017. Antimicrobial susceptibility was determined using broth microdilution, and 9546 isolates were screened for β-lactamase genes by PCR and sequencing.

RESULTS

ESBLs were identified in 35.5% of Klebsiella pneumoniae and 18.5% of Escherichia coli. ESBL carriage was lowest among isolates in Northern/Western Europe and highest in Eastern Europe. CTX-M-15 was the dominant ESBL in all countries except Greece, where SHV-type ESBLs were more common. Carbapenemases (KPC, OXA-48-like, GES, NDM and VIM) were found in 3.4% of Enterobacterales and were most common among K. pneumoniae (10.5% of those collected). Carbapenemase carriage was lowest in Northern/Western and highest in Southern Europe. KPC-positive Enterobacterales were most abundant but the percentages of OXA-48-like-, NDM- and VIM-positive isolates increased over time and were correlated with an increase in meropenem non-susceptibility. Carbapenemases (VIM, IMP, NDM and GES) were also identified in 5.1% of P. aeruginosa and were commonly found in Eastern Europe. Carbapenemase carriage and meropenem non-susceptibility among P. aeruginosa fluctuated over the 5 years studied and were not well correlated.

CONCLUSIONS

ESBL and carbapenemase carriage varied by species and European subregion. Meropenem non-susceptibility in European isolates of Enterobacterales can be attributed to carbapenemase carriage and is increasingly caused by MBLs and OXA-48-like carbapenemases. Carbapenemases or other β-lactamases are not a common cause of meropenem non-susceptibility in P. aeruginosa in Europe.

Antimicrobial Susceptibility Profiles To Predict the Presence of Carbapenemase Genes among Carbapenem-Resistant Pseudomonas aeruginosa Isolates

Detection of carbapenem-resistant Pseudomonas aeruginosa (CRPA) with carbapenemase-producing (CP) genes is critical for preventing transmission. Our objective was to assess whether certain antimicrobial susceptibility testing (AST) profiles can efficiently identify CP-CRPA. We defined CRPA as P. aeruginosa with imipenem or meropenem MICs of ≥8 μg/ml; CP-CRPA was CRPA with CP genes (bla _KPC/bla _IMP/bla _NDM/bla _OXA-48/bla _VIM). We assessed the sensitivity and specificity of AST profiles to detect CP-CRPA among CRPA isolates collected by CDC's Antibiotic Resistance Laboratory Network (AR Lab Network) and the Emerging Infections Program (EIP) during 2017 to 2019. Three percent (195/6,192) of AR Lab Network CRPA isolates were CP-CRPA. Among CRPA isolates, adding not susceptible (NS) to cefepime or ceftazidime to the definition had 91% sensitivity and 50% specificity for identifying CP-CRPA; adding NS to ceftolozane-tazobactam had 100% sensitivity and 86% specificity. Of 965 EIP CRPA isolates evaluated for CP genes, 7 were identified as CP-CRPA; 6 of the 7 were NS to cefepime and ceftazidime, and all 7 were NS to ceftolozane-tazobactam. Among 4,182 EIP isolates, clinical laboratory AST results were available for 96% of them for cefepime, 80% for ceftazidime, and 4% for ceftolozane-tazobactam. The number of CRPA isolates needed to test (NNT) to identify one CP-CRPA isolate decreased from 138 to 64 if the definition of NS to cefepime or ceftazidime was used and to 7 with NS to ceftolozane-tazobactam. Adding not susceptible to cefepime or ceftazidime to CRPA carbapenemase testing criteria would reduce the NNT by half and can be implemented in most clinical laboratories; adding not susceptible to ceftolozane-tazobactam could be even more predictive once AST for this drug is more widely available.

Activity of cefepime/zidebactam (WCK 5222) against 'problem' antibiotic-resistant Gram-negative bacteria sent to a national reference laboratory

BACKGROUND

Triple-action diazabicyclooctanes, e.g. zidebactam, combine β-lactamase inhibition, antibacterial activity, and 'enhancement' of PBP3-targeted β-lactams.

OBJECTIVES

To examine the activity of cefepime/zidebactam against consecutive 'problem' Gram-negative bacteria referred to the UK national reference laboratory.

METHODS

MICs were determined by BSAC agar dilution for 1632 Enterobacterales, 745 Pseudomonas aeruginosa and 450 other non-fermenters, categorized by carbapenemase detection and interpretive reading.

RESULTS

Universal susceptibility to cefepime/zidebactam 8 + 8 mg/L was seen for otherwise multidrug-resistant Enterobacterales with AmpC, extended-spectrum, K1, KPC and OXA-48-like β-lactamases, or with impermeability and 'unassigned' mechanisms. Unlike ceftazidime/avibactam and all other comparators, cefepime/zidebactam 8 + 8 mg/L also inhibited most (190/210, 90.5%) Enterobacterales with MBLs. Resistance in the remaining minority of MBL producers, and in 13/24 with both NDM MBLs and OXA-48-like enzymes, was associated with Klebsiella pneumoniae ST14. For Pseudomonas aeruginosa, MICs of cefepime/zidebactam rose with efflux grade, but exceeded 8 + 8 mg/L for only 11/85 isolates even in the highly-raised efflux group. Among 103 P. aeruginosa with ESBLs or MBLs, 97 (94.5%) were inhibited by cefepime/zidebactam 8 + 8 mg/L whereas fewer than 15% were susceptible to any comparator. MICs for Acinetobacter baumannii with acquired OXA carbapenemases clustered around 8 + 8 to 32 + 32 mg/L, with higher values for MBL producers. A strong enhancer effect augmented activity against many isolates that were highly resistant to cefepime and zidebactam alone and which had mechanisms not inhibited by zidebactam.

CONCLUSIONS

Assuming successful clinical trials, cefepime/zidebactam has scope to widely overcome critical resistances in both Enterobacterales and non-fermenters.

How to kill Pseudomonas-emerging therapies for a challenging pathogen

As the number of effective antibiotics dwindled, antibiotic resistance (AR) became a pressing concern. Some Pseudomonas aeruginosa isolates are resistant to all available antibiotics. In this review, we identify the mechanisms that P. aeruginosa uses to evade antibiotics, including intrinsic, acquired, and adaptive resistance. Our review summarizes many different approaches to overcome resistance. Antimicrobial peptides have potential as therapeutics with low levels of resistance evolution. Rationally designed bacteriophage therapy can circumvent and direct evolution of AR and virulence. Vaccines and monoclonal antibodies are highlighted as immune-based treatments targeting specific P. aeruginosa antigens. This review also identifies promising drug combinations, antivirulence therapies, and considerations for new antipseudomonal discovery. Finally, we provide an update on the clinical pipeline for antipseudomonal therapies and recommend future avenues for research.

AMRmap: An Interactive Web Platform for Analysis of Antimicrobial Resistance Surveillance Data in Russia

Surveillance of antimicrobial resistance (AMR) is crucial for identifying trends in resistance and developing strategies for prevention and treatment of infections. Globally, AMR surveillance systems differ in terms of organizational principles, comprehensiveness, accessibility, and usability of data presentation. Until recently, the data on AMR in Russia were scarcely available, especially to international community, despite the fact that the large prospective multicenter surveillance in Russia was conducted and data were accumulated for over 20 years. We describe the source of data, structure, and functionality of a new-generation web platform, called AMRmap (https://amrmap.net/), for analysis of AMR surveillance data in Russia. The developed platform currently comprises susceptibility data of >40,000 clinical isolates, and the data on abundance of key resistance determinants, including acquired carbapenemases in gram-negatives, are updated annually with information on >5,000 new isolates. The AMRmap allows smart data filtration by multiple parameters and provides interactive data analysis and visualization tools: MIC and S/I/R distribution plots, time-trends and regression plots, associated resistance plots, prevalence maps, statistical significance graphs, and tables.

Mobile Carbapenemase Genes in Pseudomonas aeruginosa

Carbapenem-resistant Pseudomonas aeruginosa is one of the major concerns in clinical settings impelling a great challenge to antimicrobial therapy for patients with infections caused by the pathogen. While membrane permeability, together with derepression of the intrinsic beta-lactamase gene, is the global prevailing mechanism of carbapenem resistance in P. aeruginosa, the acquired genes for carbapenemases need special attention because horizontal gene transfer through mobile genetic elements, such as integrons, transposons, plasmids, and integrative and conjugative elements, could accelerate the dissemination of the carbapenem-resistant P. aeruginosa. This review aimed to illustrate epidemiologically the carbapenem resistance in P. aeruginosa, including the resistance rates worldwide and the carbapenemase-encoding genes along with the mobile genetic elements responsible for the horizontal dissemination of the drug resistance determinants. Moreover, the modular mobile elements including the carbapenemase-encoding gene, also known as the P. aeruginosa resistance islands, are scrutinized mostly for their structures.

Diversity and Distribution of Resistance Markers in Pseudomonas aeruginosa International High-Risk Clones

Pseudomonas aeruginosa high-risk clones are disseminated worldwide and they are common causative agents of hospital-acquired infections. In this review, we will summarize available data of high-risk P. aeruginosa clones from confirmed outbreaks and based on whole-genome sequence data. Common feature of high-risk clones is the production of beta-lactamases and among metallo-beta-lactamases NDM, VIM and IMP types are widely disseminated in different sequence types (STs), by contrast FIM type has been reported in ST235 in Italy, whereas GIM type in ST111 in Germany. In the case of ST277, it is most frequently detected in Brazil and it carries a resistome linked to bla_SPM. Colistin resistance develops among P. aeruginosa clones in a lesser extent compared to other resistance mechanisms, as ST235 strains remain mainly susceptible to colistin however, some reports described mcr positive P. aeurigonsa ST235. Transferable quinolone resistance determinants are detected in P. aeruginosa high-risk clones and aac(6′)-Ib-cr variant is the most frequently reported as this determinant is incorporated in integrons. Additionally, qnrVC1 was recently detected in ST773 in Hungary and in ST175 in Spain. Continuous monitoring and surveillance programs are mandatory to track high-risk clones and to analyze emergence of novel clones as well as novel resistance determinants.

Susceptibility of clinical Enterobacterales and Pseudomonas aeruginosa isolates to ceftazidimeavibactam in Russia: multicenter local laboratory databased surveillance

Objective. To assess the in vitro activity of ceftazidime-avibactam against clinical Enterobacterales and Pseudomonas aeruginosa isolates in various regions of Russia based on results of local susceptibility testing by disk diffusion method. Materials and Methods. Overall, 160 laboratories located in 61 Russian cities participated in this surveillance during 2018-2020. All consecutive clinical isolates of Enterobacterales and Pseudomonas aeruginosa in each participating laboratory were included in the study. Ceftazidime-avibactam susceptibility testing was done by disc-diffusion method in accordance with current EUCAST recommendations. Susceptibility data for carbapenems and III-IV generation cephalosporins, as well as results of carbapenemases detection, were also reported, if available. All the data were recorded in electronic case report form developed on the OpenClinica online platform (www.openclinica.com). Data analysis and reporting were done using AMRcloud online platform (https://amrcloud.net/). Results. In total, we received information on antimicrobial susceptibility of 22,121 isolates, including 17,456 (78.9%) Enterobacterales and 4,665 (21.1%) P. aeruginosa. Less than 9% of Enterobacterales isolates were resistant to ceftazidime-avibactam. At the same time rates of resistance to ceftazidime, cefotaxime, cefepime, ertapenem, imipenem, and meropenem were 54.1%, 58.9%, 59.4%, 41.4%, 23.9%, and 21.3%. Among Enterobacterales the highest level of resistance to ceftazidime-avibactam was detected in K. pneumoniae (16.5%), lowest – in E. coli (2.1%). Some increase of resistance to ceftazidimeavibactam was noted during the study – from 7.8% in 2018-2019 to 9.6% in 2020 (p = 0.0001). Rate of resistance to ceftazidime-avibactam in P. aeruginosa was 33.1%. At the same time rates of resistance to ceftazidime, cefepime, imipenem, and meropenem were 51.1%, 54.5%, 50%, and 47.3%. During the study there was statistically significant decrease in resistance to ceftazidime-avibactam in P. aeruginosa (p = 0.0001). Resistance rates for all beta-lactams for both Enterobacterales and P. aeruginosa were higher in nosocomial isolates than in community-acquired isolates. Conclusions. Ceftazidime-avibactam demonstrated significantly higher in vitro activity against Enterobacterales and P. aeruginosa Russian clinical isolates comparing with commonly used carbapenems and extended spectrum cephalosporins. Access for all study data available at the AMRcloud online platform (https://amrcloud.net/ru/project/cazavi-1-2/).

Phenotypic and Genomic Comparison of the Two Most Common ExoU-Positive Pseudomonas aeruginosa Clones, PA14 and ST235

Genotyping of 2,882 Pseudomonas aeruginosa isolates that had been collected during the last 40 years identified the ExoU-positive lineages PA14 (ST253) and ST235 as the second and third most frequent clones in the P. aeruginosa population. Both clones were approximately 2-fold more frequently detected in animate habitats than in soil or aquatic habitats. While ST253 clone isolates were causing mainly acute and chronic infections in humans, ST235 isolates had been preferentially collected from hospitalized patients with severe acute infections, particularly, keratitis, urinary tract infections, burn wounds, and ventilator-associated pneumonia. The two major exoU clones differed substantially in the composition and flexibility of the accessory genome and by more than 8,000 amino acid sequences. Pronounced sequence variation between orthologs was noted in genes encoding elements of secretion systems and secreted effector molecules, including the type III secretion system, indicating the modes of action of the different clones. When comparing representatives of the two clones in batch culture, the PA14 strain orchestrated the quorum sensing circuitry for the expression of pathogenic traits and stopped growing in batch culture when it entered the stationary phase, but the quorum sensing-deficient ST235 strain expressed high type III secretion activity and continued to grow and to divide. In summary, unrestricted growth, high constitutive type III secretion activity, and facilitated uptake of foreign DNA could be major features that have made ST235 a global high-risk clone associated with poor outcomes of acute nosocomial infections.IMPORTANCE The ubiquitous and metabolically versatile environmental bacterium Pseudomonas aeruginosa can cause infections in a wide variety of hosts, including insects, plants, animals, and humans. P. aeruginosa is one of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens that are the major cause of nosocomial infections in the United States and are a threat all over the world because of their capacity to become increasingly resistant to all available antibiotics. Most experimental work on P. aeruginosa has been performed with reference strains PAO1 and PA14, providing deep insight into key metabolic and regulatory pathways thought to be applicable to all P. aeruginosa strains. However, this comparative study on the two most common exoU-positive clones taught us that there are major lineages in the population such as the global high-risk clone ST235 that exhibit uncommon traits of lifestyle, genome mobility, and pathogenicity distinct from those in our knowledge gained from the studies with the reference strains.

Unravelling the Features of Success of VIM-Producing ST111 and ST235 Pseudomonas aeruginosa in a Greek Hospital

The objective of this study was to analyze the characteristics that contribute to the successful dissemination of VIM-producing Pseudomonas aeruginosa (P. aeruginosa), belonging to ST111 and ST235, in a Greek hospital. A total of 120 non-repetitive P. aeruginosa, which had meropenem minimal inhibitory concentrations (MICs) greater than 2 mg/L, were studied. VIM-encoding genes were amplified and sequenced within their integrons. Isolates were typed by multilocus sequence typing (MLST). Six VIM-producers, representative of different integron structures and sequence types (STs), were completely sequenced using Illumina platform. Sixty-one P. aeruginosa were confirmed to produce VIM-type carbapenemases. ST111 dominated (n = 34) among VIM-producers, while 15 VIM-producers belonged to ST235. The blaVIM-like genes were located in three integron types, including In59, In595 and In1760, which were integrated into P. aeruginosa chromosomes. Whole genome sequencing (WGS) data demonstrated that ST111 and ST235 MBL producers carried several resistance and virulence genes. Additionally, the presence of type I-C and type I-E clustered regularly interspaced short palindromic repeats (CRISPR)/Cas locus was observed in ST235 and ST395 isolates, respectively. In conclusion, our findings confirmed the clonal spread of ST111 P. aeruginosa, carrying the VIM-2-encoding integron In59, in the University Hospital of Larissa (UHL). In addition, they highlighted the important role of high-risk clones, ST111 and ST235, in the successful dissemination and establishment into hospital settings of clinically important pathogens carrying resistance determinants.

Agents of Last Resort: An Update on Polymyxin Resistance

Polymyxin resistance is a major public health threat, because the polymyxins represent last-line therapeutics for gram-negative pathogens resistant to essentially all other antibiotics. Minimizing any potential emergence and dissemination of polymyxin resistance relies on an improved understanding of mechanisms of and risk factors for polymyxin resistance, infection prevention and stewardship strategies, together with optimization of dosing of polymyxins (eg, combination regimens).

Evaluation of in vitro activity of ceftazidime/avibactam and ceftolozane/tazobactam against MDR Pseudomonas aeruginosa isolates from Qatar

OBJECTIVES

To investigate the in vitro activity of ceftazidime/avibactam and ceftolozane/tazobactam against clinical isolates of MDR Pseudomonas aeruginosa from Qatar, as well as the mechanisms of resistance.

METHODS

MDR P. aeruginosa isolated between October 2014 and September 2015 from all public hospitals in Qatar were included. The BD PhoenixTM system was used for identification and initial antimicrobial susceptibility testing, while Liofilchem MIC Test Strips (Liofilchem, Roseto degli Abruzzi, Italy) were used for confirmation of ceftazidime/avibactam and ceftolozane/tazobactam susceptibility. Ten ceftazidime/avibactam- and/or ceftolozane/tazobactam-resistant isolates were randomly selected for WGS.

RESULTS

A total of 205 MDR P. aeruginosa isolates were included. Of these, 141 (68.8%) were susceptible to ceftazidime/avibactam, 129 (62.9%) were susceptible to ceftolozane/tazobactam, 121 (59.0%) were susceptible to both and 56 (27.3%) were susceptible to neither. Twenty (9.8%) isolates were susceptible to ceftazidime/avibactam but not to ceftolozane/tazobactam and only 8 (3.9%) were susceptible to ceftolozane/tazobactam but not to ceftazidime/avibactam. Less than 50% of XDR isolates were susceptible to ceftazidime/avibactam or ceftolozane/tazobactam. The 10 sequenced isolates belonged to six different STs and all produced AmpC and OXA enzymes; 5 (50%) produced ESBL and 4 (40%) produced VIM enzymes.

CONCLUSIONS

MDR P. aeruginosa susceptibility rates to ceftazidime/avibactam and ceftolozane/tazobactam were higher than those to all existing antipseudomonal agents, except colistin, but were less than 50% in extremely resistant isolates. Non-susceptibility to ceftazidime/avibactam and ceftolozane/tazobactam was largely due to the production of ESBL and VIM enzymes. Ceftazidime/avibactam and ceftolozane/tazobactam are possible options for some patients with MDR P. aeruginosa in Qatar.

Metallo-β-Lactamases: Structure, Function, Epidemiology, Treatment Options, and the Development Pipeline

Modern medicine is threatened by the global rise of antibiotic resistance, especially among Gram-negative bacteria. Metallo-β-lactamase (MBL) enzymes are a particular concern and are increasingly disseminated worldwide, though particularly in Asia. Many MBL producers have multiple further drug resistances, leaving few obvious treatment options. Nonetheless, and more encouragingly, MBLs may be less effective agents of carbapenem resistance in vivo, under zinc limitation, than in vitro Owing to their unique structure and function and their diversity, MBLs pose a particular challenge for drug development. They evade all recently licensed β-lactam-β-lactamase inhibitor combinations, although several stable agents and inhibitor combinations are at various stages in the development pipeline. These potential therapies, along with the epidemiology of producers and current treatment options, are the focus of this review.

Spanish nationwide survey on Pseudomonas aeruginosa antimicrobial resistance mechanisms and epidemiology

OBJECTIVES

To undertake a Spanish nationwide survey on Pseudomonas aeruginosa molecular epidemiology and antimicrobial resistance.

METHODS

Up to 30 consecutive healthcare-associated P. aeruginosa isolates collected in 2017 from each of 51 hospitals were studied. MICs of 13 antipseudomonal agents were determined by broth microdilution. Horizontally acquired β-lactamases were detected by phenotypic methods and PCR. Clonal epidemiology was evaluated through PFGE and MLST; at least one XDR isolate from each clone and hospital (n = 185) was sequenced.

RESULTS

The most active antipseudomonals against the 1445 isolates studied were colistin and ceftolozane/tazobactam (both 94.6% susceptible, MIC50/90 = 1/2 mg/L) followed by ceftazidime/avibactam (94.2% susceptible, MIC50/90 = 2/8 mg/L). Up to 252 (17.3%) of the isolates were XDR. Carbapenemases/ESBLs were detected in 3.1% of the isolates, including VIM, IMP, GES, PER and OXA enzymes. The most frequent clone among the XDR isolates was ST175 (40.9%), followed by CC235 (10.7%), ST308 (5.2%) and CC111 (4.0%). Carbapenemase production varied geographically and involved diverse clones, including 16.5% of ST175 XDR isolates. Additionally, 56% of the sequenced XDR isolates showed horizontally acquired aminoglycoside-modifying enzymes, which correlated with tobramycin resistance. Two XDR isolates produced QnrVC1, but fluoroquinolone resistance was mostly caused by QRDR mutations. Beyond frequent mutations (>60%) in OprD and AmpC regulators, four isolates showed AmpC mutations associated with resistance to ceftolozane/tazobactam and ceftazidime/avibactam.

CONCLUSIONS

ST175 is the most frequent XDR high-risk clone in Spanish hospitals, but this nationwide survey also indicates a complex scenario in which major differences in local epidemiology, including carbapenemase production, need to be acknowledged in order to guide antimicrobial therapy.

Genetic Characterization of Carbapenemase-Producing Enterobacter cloacae Complex and Pseudomonas aeruginosa of Food of Animal Origin from Egypt

The increasing spread of carbapenem resistance is a serious global public health concern that negatively affects human and animal health. In this study we characterized the carbapenemase production in gram-negative bacteria isolated from different meat and meat products in Egypt. Phenotypic and genotypic susceptibility testing were investigated. Two Enterobacter cloacae complex strains, isolated from kofta and beef burger, and one Pseudomonas aeruginosa isolated from minced meat, were found to harbor VIM-1 and VIM-2, respectively. These isolates showed multidrug resistance phenotype. The phenotypic carbapenemase production was confirmed with Carba NP test in addition to modified Hodge test, modified carbapenem inactivation method, and ethylenediaminetetraacetic acid inhibition test. The bla_VIM-1 gene in both non-clonally related E. cloacae complex strains was part of a class 1 integron that also carried other resistance gene cassettes such as aacA7, dfrA1, ΔaadA, and smr. This integron was uncommonly disrupted by the insertion sequence ISPa21, located on a self-conjugative plasmid of either the A/C or HI2 incompatibility group with a size of >93 kb. The bla_VIM-2 gene was identified within a class 1 integron, followed downstream by resistance genes aadB and bla_OXA-10. The transfer of bla_VIM-2 gene from P. aeruginosa failed, suggesting that this gene was located on the chromosome. Further studies are needed to screen the dissemination of carbapenemase-producing bacteria in both the environment and food chain.

Determination of carbapenems in water samples by UHPLC-MS/MS

A rapid and reliable method for the detection of five carbapenems (biapenem, imipenem, doripenem, meropenem, and faropenem) in water was developed and validated. After acidification of water samples with acetic acid, carbapenems were isolated using a Bond Elut PPL cartridge. The target compounds were separated using ultra high performance liquid chromatography with a chromatographic run time of 5 min and detected on a triple quadrupole mass spectrometer operated in positive electrospray ionization and multiple reaction monitoring mode. Mean recoveries were in the range of 76.6-106.5%, with satisfactory intraday and interday relative standard deviations lower than 10.0 and 10.8%, respectively. The limits of detection and quantification were in the ranges of 0.05-0.2 µg/L and 0.1-0.5 µg/L, respectively, depending on the analyte. The proposed method was applied to the analysis of river samples and wastewater samples from swine farms, and no carbapenems were detected in the collected samples.

4-Amino-1,2,4-triazole-3-thione as a Promising Scaffold for the Inhibition of Serine and Metallo-β-Lactamases

The emergence of bacteria that co-express serine- and metallo- carbapenemases is a threat to the efficacy of the available β-lactam antibiotic armamentarium. The 4-amino-1,2,4-triazole-3-thione scaffold has been selected as the starting chemical moiety in the design of a small library of β-Lactamase inhibitors (BLIs) with extended activity profiles. The synthesised compounds have been validated in vitro against class A serine β-Lactamase (SBLs) KPC-2 and class B1 metallo β-Lactamases (MBLs) VIM-1 and IMP-1. Of the synthesised derivatives, four compounds showed cross-class micromolar inhibition potency and therefore underwent in silico analyses to elucidate their binding mode within the catalytic pockets of serine- and metallo-BLs. Moreover, several members of the synthesised library have been evaluated, in combination with meropenem (MEM), against clinical strains that overexpress BLs for their ability to synergise carbapenems.

VNRX-5133 (Taniborbactam), a Broad-Spectrum Inhibitor of Serine- and Metallo-β-Lactamases, Restores Activity of Cefepime in Enterobacterales and Pseudomonas aeruginosa

As shifts in the epidemiology of β-lactamase-mediated resistance continue, carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) are the most urgent threats. Although approved β-lactam (BL)-β-lactamase inhibitor (BLI) combinations address widespread serine β-lactamases (SBLs), such as CTX-M-15, none provide broad coverage against either clinically important serine-β-lactamases (KPC, OXA-48) or clinically important metallo-β-lactamases (MBLs; e.g., NDM-1). VNRX-5133 (taniborbactam) is a new cyclic boronate BLI that is in clinical development combined with cefepime for the treatment of infections caused by β-lactamase-producing CRE and CRPA. Taniborbactam is the first BLI with direct inhibitory activity against Ambler class A, B, C, and D enzymes. From biochemical and structural analyses, taniborbactam exploits substrate mimicry while employing distinct mechanisms to inhibit both SBLs and MBLs. It is a reversible covalent inhibitor of SBLs with slow dissociation and a prolonged active-site residence time (half-life, 30 to 105 min), while in MBLs, it behaves as a competitive inhibitor, with inhibitor constant (K_i ) values ranging from 0.019 to 0.081 μM. Inhibition is achieved by mimicking the transition state structure and exploiting interactions with highly conserved active-site residues. In microbiological testing, taniborbactam restored cefepime activity in 33/34 engineered Escherichia coli strains overproducing individual enzymes covering Ambler classes A, B, C, and D, providing up to a 1,024-fold shift in the MIC. Addition of taniborbactam restored the antibacterial activity of cefepime against all 102 Enterobacterales clinical isolates tested and 38/41 P. aeruginosa clinical isolates tested with MIC₉₀s of 1 and 4 μg/ml, respectively, representing ≥256- and ≥32-fold improvements, respectively, in antibacterial activity over that of cefepime alone. The data demonstrate the potent, broad-spectrum rescue of cefepime activity by taniborbactam against clinical isolates of CRE and CRPA.

Genotypes, carbapenemase carriage, integron diversity and oprD alterations among carbapenem-resistant Pseudomonas aeruginosa from Russia

Pseudomonas aeruginosa is a serious opportunistic pathogen demonstrating a high level of resistance to many groups of antibiotics, including carbapenems. This study aimed to characterise the molecular epidemiology and prevalence of mobile genetic elements associated with resistance to carbapenems among P. aeruginosa (CRPA) clinical isolates. Among 145 carbapenem-resistant P. aeruginosa isolates, 34 different sequence types (STs) were detected; the six most common STs were ST654 (24%), ST235 (24%), ST111 (8%), ST446 (6%), ST357 (5%) and ST2592 (a novel single-locus variant of ST357) (4%). A carbapenemase gene was found in 94 isolates (64.8%). The bla_VIM-2 gene was harboured by 64 isolates (44.1%) restricted to ST111, ST235 and ST654, and the bla_GES-type and bla_OXA-10 group genes were each detected in 15 isolates (10.3%); none of other tested carbapenemase genes, including bla_IMP, bla_NDM and bla_GIM, were detected. Among the bla_VIM-2-positive isolates, five types of bla_VIM-2-containing integrons were discovered, including In56, In559, In59-like, In59 and In249. The oprD gene was disrupted by an insertion sequence (IS) in 15.9% of isolates. Overall, five types of IS elements were found (ISPsme1, ISPa1328, ISPa26, ISPst2 and ISPa195). Observed rearrangements within variable regions of bla_VIM-2-carrying integrons in conjunction with the discovery of a novel type of oprD-disrupting IS element illustrate the ongoing evolution of CRPA a, which warrants further investigation.

Antimicrobial susceptibility of Pasteurella multocida isolated from sheep and pigs in Spain - Short communication

Pasteurella multocida is responsible for economically important diseases in sheep and pigs. Antimicrobial susceptibility studies are essential for initiating rational and effective empirical therapy of P. multocida infections. In this study we investigated the antimicrobial susceptibility to 18 antimicrobial agents of 156 clinical isolates of P. multocida from sheep (n = 87) and pigs (n = 69) using the microdilution method. Both sheep and pig isolates exhibited low levels of resistance (≤ 15%) to ceftiofur, gentamicin, neomycin, spectinomycin, chlortetracycline, tulathromycin, florfenicol, danofloxacin, and enrofloxacin and trimethoprim/sulphamethoxazole, high resistance rates (> 15% up to 50%) to oxytetracycline, tilmicosin, and tiamulin, and very high resistance rates (> 50%) to tylosin tartrate, clindamycin, and sulphadimethoxine. However, sheep isolates exhibited significantly lower percentages of resistance and lower MIC₉₀ values (P < 0.05) than pig isolates for most of the antimicrobials tested. In addition, sheep isolates exhibited also significantly lower phenotypic antimicrobial resistance diversity (8 resistotypes vs. 30 resistotypes). LAC-LIN-SUL-MAC was the resistotype most frequently detected in sheep (39.1%) and LIN-SUL-MAC in pig isolates (26.1%). The differences in susceptibility patterns could be influenced by the lower use of antimicrobials in the small ruminant industry compared with the pig farming industry.

β-Lactamases and β-Lactamase Inhibitors in the 21st Century

The β-lactams retain a central place in the antibacterial armamentarium. In Gram-negative bacteria, β-lactamase enzymes that hydrolyze the amide bond of the four-membered β-lactam ring are the primary resistance mechanism, with multiple enzymes disseminating on mobile genetic elements across opportunistic pathogens such as Enterobacteriaceae (e.g., Escherichia coli) and non-fermenting organisms (e.g., Pseudomonas aeruginosa). β-Lactamases divide into four classes; the active-site serine β-lactamases (classes A, C and D) and the zinc-dependent or metallo-β-lactamases (MBLs; class B). Here we review recent advances in mechanistic understanding of each class, focusing upon how growing numbers of crystal structures, in particular for β-lactam complexes, and methods such as neutron diffraction and molecular simulations, have improved understanding of the biochemistry of β-lactam breakdown. A second focus is β-lactamase interactions with carbapenems, as carbapenem-resistant bacteria are of grave clinical concern and carbapenem-hydrolyzing enzymes such as KPC (class A) NDM (class B) and OXA-48 (class D) are proliferating worldwide. An overview is provided of the changing landscape of β-lactamase inhibitors, exemplified by the introduction to the clinic of combinations of β-lactams with diazabicyclooctanone and cyclic boronate serine β-lactamase inhibitors, and of progress and strategies toward clinically useful MBL inhibitors. Despite the long history of β-lactamase research, we contend that issues including continuing unresolved questions around mechanism; opportunities afforded by new technologies such as serial femtosecond crystallography; the need for new inhibitors, particularly for MBLs; the likely impact of new β-lactam:inhibitor combinations and the continuing clinical importance of β-lactams mean that this remains a rewarding research area.

Local outbreak of extended-spectrum β-lactamase SHV2a-producing Pseudomonas aeruginosa reveals the emergence of a new specific sub-lineage of the international ST235 high-risk clone

BACKGROUND

Pseudomonas aeruginosa is a major bacterial pathogen responsible for hospital-acquired infections. Although its epidemiology is considered as non-clonal, certain international high-risk multidrug-resistant clones have been recognized.

AIM

From the first report of an intra-hospital outbreak due to an SHV2a-producing P. aeruginosa strain, to describe the emergence of a new ST235-specific lineage harbouring this rare extended-spectrum β-lactamase (ESBL).

METHODS

Between May and October 2018, four patients hospitalized in the cardiovascular intensive care unit of a French teaching hospital were infected by a multidrug-resistant P. aeruginosa isolate. Serotype and antimicrobial susceptibility were tested; multi-locus sequence type (MLST), core genome MLST, and resistome were determined through whole genome sequencing. A phylogenetic analysis based on single nucleotide polymorphism was performed using available ST235 genomes.

FINDINGS

The four strains were susceptible to colistin, ciprofloxacin, ceftazidime-avibactam, and ceftolozane-tazobactam. bla_SHV2a was identified in each genome of this ST235-O11 serotype cluster that showed an identical cgMLST profile (0-2 out of 4162 different alleles). The phylogenic analysis of 162 ST235 genomes showed that only four other strains harboured a bla_SHV2a, originating from France and USA, clustering together although being different from the outbreak strains.

CONCLUSIONS

Among the ST235 P. aeruginosa strains, a sub-lineage sharing a common genetic background and harbouring the bla_SHV2a ESBL seems to emerge from different locations, yielding secondary local outbreaks.

Longitudinal analysis of the in vitro activity of ceftazidime-avibactam vs. Pseudomonas aeruginosa, 2012-2016

The in vitro activities of ceftazidime-avibactam and comparator agents were analyzed against 14,330 isolates of Pseudomonas aeruginosa from 188 centers distributed globally (except North America) from 2012 (2014 for colistin) to 2016 as part of the International Network for Optimal Resistance Monitoring (INFORM) global surveillance program. Susceptibility testing used in-house prepared broth microdilution panels following CLSI guidelines. Multiplex PCR assays identified the presence of β-lactamases. Ceftazidime-avibactam (MIC₉₀ 8 mg/L; 91.5% susceptibility) and colistin (N = 11,032; MIC₉₀ 2 mg/L, 96.2%) were the 2 most active agents. Susceptibility of multidrug-resistant isolates (N = 3770, 26.3%) was ≤54.4% to all agents except colistin (N = 2956; 95.2% susceptible) and ceftazidime-avibactam (68.2%). Metallo-β-lactamase-positive isolates (N = 621, 4.3%) were not susceptible to any agents except colistin (N = 504; 98.2% susceptible). Novel therapeutic options are needed for infections caused by P. aeruginosa-resistant phenotypes.

Italian nationwide survey on Pseudomonas aeruginosa from invasive infections: activity of ceftolozane/tazobactam and comparators, and molecular epidemiology of carbapenemase producers

Objectives

Pseudomonas aeruginosa is a major cause of severe healthcare-associated infections and often shows MDR phenotypes. Ceftolozane/tazobactam is a new cephalosporin/β-lactamase inhibitor combination with potent activity against P. aeruginosa. This survey was carried out to evaluate the susceptibility of P. aeruginosa, circulating in Italy, to ceftolozane/tazobactam and comparators and to investigate the molecular epidemiology of carbapenemase-producing strains.

Methods

Consecutive non-replicate P. aeruginosa clinical isolates (935) from bloodstream infections and lower respiratory tract infections were collected from 20 centres distributed across Italy from September 2013 to November 2014. Antimicrobial susceptibility testing was performed by broth microdilution and results were interpreted according to the EUCAST breakpoints. Isolates resistant to ceftolozane/tazobactam were investigated for carbapenemase genes by PCR, and for carbapenemase activity by spectrophotometric assay. WGS using an Illumina platform was performed on carbapenemase-producing isolates.

Results

Ceftolozane/tazobactam was the most active molecule, retaining activity against 90.9% of P. aeruginosa isolates, followed by amikacin (88.0% susceptibility) and colistin (84.7% susceptibility). Overall, 48 isolates (5.1%) were positive for carbapenemase genes, including blaVIM (n = 32), blaIMP (n = 12) and blaGES-5 (n = 4), while the remaining ceftolozane/tazobactam-resistant isolates tested negative for carbapenemase production. Carbapenemase producers belonged to 10 different STs, with ST175 (n = 12) and ST621 (n = 11) being the most common lineages. Genome analysis revealed different trajectories of spread for the different carbapenemase genes.

Conclusions

Ceftolozane/tazobactam exhibited potent in vitro activity against P. aeruginosa causing invasive infections in Italy. Carbapenemase production was the most common mechanism of resistance to ceftolozane/tazobactam.

Treatment of infections caused by multidrug-resistant Gram-negative bacteria: report of the British Society for Antimicrobial Chemotherapy/Healthcare Infection Society/British Infection Association Joint Working Party

The Working Party makes more than 100 tabulated recommendations in antimicrobial prescribing for the treatment of infections caused by multidrug-resistant (MDR) Gram-negative bacteria (GNB) and suggest further research, and algorithms for hospital and community antimicrobial usage in urinary infection. The international definition of MDR is complex, unsatisfactory and hinders the setting and monitoring of improvement programmes. We give a new definition of multiresistance. The background information on the mechanisms, global spread and UK prevalence of antibiotic prescribing and resistance has been systematically reviewed. The treatment options available in hospitals using intravenous antibiotics and in primary care using oral agents have been reviewed, ending with a consideration of antibiotic stewardship and recommendations. The guidance has been derived from current peer-reviewed publications and expert opinion with open consultation. Methods for systematic review were NICE compliant and in accordance with the SIGN 50 Handbook; critical appraisal was applied using AGREE II. Published guidelines were used as part of the evidence base and to support expert consensus. The guidance includes recommendations for stakeholders (including prescribers) and antibiotic-specific recommendations. The clinical efficacy of different agents is critically reviewed. We found there are very few good-quality comparative randomized clinical trials to support treatment regimens, particularly for licensed older agents. Susceptibility testing of MDR GNB causing infection to guide treatment needs critical enhancements. Meropenem- or imipenem-resistant Enterobacteriaceae should have their carbapenem MICs tested urgently, and any carbapenemase class should be identified: mandatory reporting of these isolates from all anatomical sites and specimens would improve risk assessments. Broth microdilution methods should be adopted for colistin susceptibility testing. Antimicrobial stewardship programmes should be instituted in all care settings, based on resistance rates and audit of compliance with guidelines, but should be augmented by improved surveillance of outcome in Gram-negative bacteraemia, and feedback to prescribers. Local and national surveillance of antibiotic use, resistance and outcomes should be supported and antibiotic prescribing guidelines should be informed by these data. The diagnosis and treatment of both presumptive and confirmed cases of infection by GNB should be improved. This guidance, with infection control to arrest increases in MDR, should be used to improve the outcome of infections with such strains. Anticipated users include medical, scientific, nursing, antimicrobial pharmacy and paramedical staff where they can be adapted for local use.