Long-term evolution of a nosocomial outbreak of Pseudomonas aeruginosa producing VIM-2 metallo-enzyme

Changing Genotypic Distribution, Antimicrobial Susceptibilities, and Risk Factors of Urinary Tract Infection Caused by Carbapenemase-Producing Pseudomonas aeruginosa

Background

Carbapenem-resistant Pseudomonas aeruginosa (CrPA) is a leading cause of healthcare-associated urinary tract infections (UTIs). Carbapenemase production is an important mechanism that significantly alters the efficacy of frequently used anti-pseudomonal agents. Reporting the current genotypic distribution of carbapenemase-producing P. aeruginosa (CPPA) isolates in relation to antimicrobial susceptibility, UTI risk factors, and mortality is necessary to increase the awareness and control of these strains.

Methods

In total, 1,652 non-duplicated P. aeruginosa strains were isolated from hospitalized patients between 2015 and 2020. Antimicrobial susceptibility, carbapenemase genotypes, risk factors for UTI, and associated mortality were analyzed.

Results

The prevalence of carbapenem-non-susceptible P. aeruginosa isolates showed a decreasing trend from 2015 to 2018 and then increased in the background of the emergence of New Delhi metallo-β-lactamase (NDM)-type isolates since 2019. The CPPA strains showed 100.0% non-susceptibility to all tested antibiotics, except aztreonam (94.5%) and colistin (5.9%). Carbapenems were identified as a risk and common predisposing factor for UTI (odds ratio [OR]=1.943) and mortality (OR=2.766). Intensive care unit (ICU) stay (OR=2.677) and white blood cell (WBC) count (OR=1.070) were independently associated with mortality.

Conclusions

The changing trend and genetic distribution of CPPA isolates emphasize the need for relentless monitoring to control further dissemination. The use of carbapenems, ICU stay, and WBC count should be considered risk factors, and aggressive antibiotic stewardship programs and monitoring may serve to prevent worse outcomes.

Intravenous Fosfomycin for Systemic Multidrug-Resistant Pseudomonas aeruginosa Infections

Human Pseudomonas infections have high morbidity and mortality rates. Pseudomonas bacteria can cause sepsis or septic shock; they produce biofilm and commonly exhibit a multidrug-resistant phenotype. The choice of antimicrobial therapy in many cases is challenging, and deep knowledge of clinical, microbiological, and pharmacological issues is required. Intravenous fosfomycin is being repurposed in a combination given its favorable pharmacokinetic/pharmacodynamic properties (a small molecule with favorable kinetic both in bloodstream infection and in deep-seated infections), antibiofilm activity, and its interesting synergistic effects with other antimicrobials. Recent literature on epidemiological, microbiological, pharmacological, and clinical data on intravenous fosfomycin therapy against Pseudomonas is herein reviewed and discussed.

Localized outbreaks of Pseudomonas aeruginosa belonging to international high-risk clones in a south Indian hospital

Introduction. Pseudomonas aeruginosa is now considered as a major bacterial pathogen associated with hospital infections. Frequently, multidrug-resistant (MDR) and extensively drug-resistant (XDR) P. aeruginosa are being encountered. Unusual increase in the P. aeruginosa infections led to the suspicion of outbreaks in the urology ward and cardiothoracic and vascular surgery intensive care unit (CTVS-ICU).Hypothesis. We hypothesize that the localized outbreaks may have originated from environmental sources within the hospital premises. An alternative possibility is the transmission from a previously infected patient or hospital attendant. Understanding the drug-resistance profile and genome characteristics of these clinical samples would determine the likely source of infection and spread.Aim. To perform epidemiological and molecular investigations on the suspected outbreaks of P. aeruginosa in the study centre and identify potential sources of infection.Methodology. Fourteen drug-resistant P. aeruginosa isolated from patients of the urology ward, CTVS-ICU and tap waters collected during the suspected outbreaks were subjected to microbiological and genomic analysis. Comparative genome (CG) analysis of these 14 study genomes with 284 complete P. aeruginosa genomes was performed.Results. Multilocus sequence typing analysis revealed that the isolates belonged to five different sequence types (ST235, ST357, ST639, ST654 and ST1203) and clustered into three distinct groups while two CTVS-ICU isolates remained as singletons. Genome analysis distinguished that the outbreaks in the urology ward and CTVS-ICU are independent, epidemiologically unrelated to each other and with the tap-water isolates.Conclusion. This study highlights the presence of distinct, clonally unrelated, drug-resistant P. aeruginosa within a hospital setting. The genome analysis of the two localized outbreaks revealed their distinct genetic background and phylogenetically unrelated origin. Vigilant screening and effective implementation of infection control measures led to the successful containment of potential environmental reservoirs of P. aeruginosa within the premises.

First Italian outbreak of VIM-producing Serratia marcescens in an adult polyvalent intensive care unit, August-October 2018: A case report and literature review

BACKGROUND

Carbapenem-resistant Enterobacteriaceae has become a significant public health concern as hospital outbreaks are now being frequently reported and these organisms are becoming difficult to treat with the available antibiotics.

CASE SUMMARY

An outbreak of VIM-producing Serratia marcescens occurred over a period of 11 wk (August, 1 to October, 18) in patients admitted to the adult polyvalent intensive care unit of the University of Campania “Luigi Vanvitelli” located in Naples. Four episodes occurred in three patients (two patients infected, and one patient colonized). All the strains revealed the production of VIM.

CONCLUSION

After three decades of carbapenem antibiotics use, the emergence of carbapenem-resistance in Enterobacteriaceae has become a significant concern and a stricter control to preserve its clinical application is mandatory. This is, to our knowledge, the first outbreak of VIM-producing Serratia marcescens in Europe. Surveillance policies must be implemented to avoid future outbreaks.

Nosocomial Infections with IMP-19-Producing Pseudomonas aeruginosa Linked to Contaminated Sinks, France

We isolated IMP-19–producing Pseudomonas aeruginosa from 7 patients with nosocomial infections linked to contaminated sinks in France. We showed that bla_IMP-19 was located on various class 1 integrons among 8 species of gram-negative bacilli detected in sinks: P. aeruginosa, Achromobacter xylosoxidans, A. aegrifaciens, P. putida, Stenotrophomonas maltophilia, P. mendocina, Comamonas testosteroni, and Sphingomonas sp.

In vivo efficacy of humanized high dose meropenem and comparators against Pseudomonas aeruginosa isolates producing verona integron-encoded metallo-β-lactamase (VIM)

Introduction

We aimed to describe the in vivo efficacy of meropenem, in addition to cefepime and levofloxacin as comparators against VIM-producing Pseudomonas aeruginosa and compare the findings to our previous observations with Enterobacteriaceae.

Methods

Eight clinical P. aeruginosa isolates with meropenem MICs from 4 to 512 mg/L were studied in a murine neutropenic thigh infection model. Animals were treated with doses of the antibiotics to simulate the human exposure of meropenem 2 g q8 h 30-min infusion, cefepime 2 g q8 h 30-min infusion and levofloxacin 500 mg q24 h. After 24 hours, the animals were euthanized and efficacy was calculated as the change in thigh bacterial density (log₁₀ CFU) relative to the starting inoculum (0 h).

Results

As expected, levofloxacin was ineffective against all isolates due to their resistant phenotype (8 to>64 mg/L). Cefepime also showed minimal activity against all isolates consistent with its failure to achieve pharmacodynamic target exposures due to high MICs of 32 to>512 mg/L. In the presence of low MICs (4 to 16 mg/L), the fT> MIC of meropenem was sufficiently high to result in CFU reductions. However, conflicting activity was noted for isolates with MICs = 128 mg/L that possessed the same enzymatic profile, suggesting that other mechanisms of resistance are responsible for driving CFU outcomes. No activity was noted for organisms with a meropenem MIC = 512 mg/L.

Conclusion

Unlike previous observations with MBL-producing Enterobacteriaceae that showed discordance between in vitro resistance and in vivo efficacy in the murine infection model, we found that the efficacy of humanized cefepime and meropenem was generally concordant with the phenotypic profile of VIM-producing P. aeruginosa.

Detection and Genetic Characterization of Metallo-β-Lactamase IMP-1 and VIM-2 in Pseudomonas aeruginosa Strains From Different Hospitals in Kermanshah, Iran

Background:

Pseudomonas aeruginosais a frequent nosocomial pathogen that causes severe diseases in many settings. Carbapenems, including meropenem and imipenem, are effective antibiotics against this organism. However, the use of carbapenems has been hampered by the emergence of strains resistant to carbapenemsvia different mechanisms such as the production of metallo-β-lactamases (MBLs), which hydrolyze all carbapenems. Several kinds of MBLs have been reported, among them VIM and IMP types being the most clinically significant carbapenemases.

Objectives:

We aimed to determine the distribution of bla_VIM-2 and bla_IMP-1 transferable genes encoding MBLs in P. aeruginosa isolated from three academic hospitals in Kermanshah.

Patients and Methods:

From 22nd June to 22nd September 2012, 225 isolates of P. aeruginosa were collected. These isolates were tested for antibiotic susceptibility with the Kirby-Bauer disk-diffusion method, and the MBLs were assessed using the imipenem-EDTA double-disk synergy test. The isolates were investigated for bla_VIM-2 and bla_IMP-1 genes using polymerase chain reaction.

Results:

Among the 225 isolates, 33.7% (76/225) and 18.1% (41/225) were resistant to imipenem and meropenem, respectively. Of the 76 imipenem-resistant P. aeruginosa strains, 45 (59.2%) were positive for MBLs, 34 (75%) strains carried the bla_IMP-1 gene, and 1 (2.2%) strain carried the bla_VIM-2 gene.

Conclusions:

Our results showed that there was a high frequency of IMP-1 positive P. aeruginosa in the different wards of the hospitals.

The difficult-to-control spread of carbapenemase producers among Enterobacteriaceae worldwide

The spread of carbapenemase producers in Enterobacteriaceae has now been identified worldwide. Three main carbapenemases have been reported; they belong to three classes of β-lactamases, which are KPC, NDM, and OXA-48. The main reservoirs of KPC are Klebsiella pneumoniae in the USA, Israel, Greece, and Italy, those of NDM are K. pneumoniae and Escherichia coli in the Indian subcontinent, and those of OXA-48 are K. pneumoniae and Escherichia coli in North Africa and Turkey. KPC producers have been mostly identified among nosocomial isolates, whereas NDM and OXA-48 producers are both nosocomial and community-acquired pathogens. Control of their spread is still possible in hospital settings, and relies on the use of rapid diagnostic techniques and the strict implemention of hygiene measures.

Detection and termination of an extended low-frequency hospital outbreak of GIM-1-producing Pseudomonas aeruginosa ST111 in Germany

BACKGROUND

Metallo-β-lactamase German imipenemase-1 (GIM-1)-mediated carbapenem resistance is emerging in Germany but has not spread beyond a very localized region. The aim of this study was to describe the first outbreak of an extensively drug-resistant GIM-1-carrying Pseudomonas aeruginosa strain affecting 29 patients in a tertiary care hospital from 2002-2013.

METHODS

The outbreak was studied retrospectively and prospectively by a combination of molecular methods (carbapenemase polymerase chain reaction [PCR]), genotyping (DiversiLab, pulsed field gel electrophoresis and multi-locus sequence typing, bioMérieux, Marcy l'Etoile, France), descriptive epidemiology, and extensive environmental investigations using swabs with liquid transport medium, blaGIM-1 PCR, directly from the medium and culture.

RESULTS

Of the 29 affected patients, 24 had been admitted to a surgical intensive care unit at some point, where environmental sampling revealed a high burden of blaGIM-1 in the wastewater system. The outbreak strain was found in several sinks and on a reusable hair washbasin. Initially, general infection control measures were applied; thereafter, specific measures were implemented, including the restriction of washbasin use. Continued surveillance over a period of 2 years has revealed no further case of GIM-1-carrying Pseudomonas aeruginosa.

CONCLUSION

This long-term outbreak highlights the potential of molecular methods in surveillance for multidrug-resistant pathogens and in environmental sampling and the successful containment by application of specific control measures targeting biofilms within sink drains as potential environmental reservoirs for P aeruginosa.

Analysis of a long-term outbreak of XDR Pseudomonas aeruginosa: a molecular epidemiological study

OBJECTIVES

Here we report on a long-term outbreak from 2009 to 2012 with an XDR Pseudomonas aeruginosa on two wards at a university hospital in southern Germany.

METHODS

Whole-genome sequencing was performed on the outbreak isolates and a core genome was constructed for molecular epidemiological analysis. We applied a time-place-sequence algorithm to improve estimation of transmission probabilities.

RESULTS

By using conventional infection control methods we identified 49 P. aeruginosa strains, including eight environmental isolates that belonged to ST308 (by MLST) and carried the metallo-β-lactamase IMP-8. Phylogenetic analysis on the basis of a non-recombinant core genome that contained 22 outbreak-specific SNPs revealed a pattern of four dominant clades with a strong phylogeographic structure and allowed us to determine the potential temporal origin of the outbreak to July 2008, 1 year before the index case was diagnosed. Superspreaders at the root of clades exhibited a high number of probable and predicted transmissions, indicating their exceptional position in the outbreak.

CONCLUSIONS

Our results suggest that the initial expansion of dominant sublineages was driven by a few superspreaders, while environmental contamination seemed to sustain the outbreak for a long period despite regular environmental control measures.

Nosocomial infections with metallo-beta-lactamase-producing Pseudomonas aeruginosa: molecular epidemiology, risk factors, clinical features and outcomes

BACKGROUND

Metallo-β-lactamases (MBLs) have emerged as one of the most important bacterial resistance mechanisms because of their ability to hydrolyse virtually all β-lactam agents. MBL-producing Pseudomonas aeruginosa (MBL-PA) are an important cause of nosocomial infections, particularly in intensive care units (ICUs), where they are associated with serious infections and present a significant clinical risk.

AIM

To assess the molecular epidemiology, risk factors and outcomes of nosocomial infections caused by MBL-PA in a teaching hospital in Southern Brazil.

METHODS

From January 2001 to December 2008, 142 carbapenem-resistant P. aeruginosa strains were isolated from distinct clinical samples from hospitalized patients. These isolates were screened for MBLs, and underwent polymerase chain reaction, sequencing and pulsed-field gel electrophoresis (PFGE). Patients infected with carbapenem-resistant MBL-PA were considered as cases, and patients infected with non-MBL-PA were considered as controls.

FINDINGS

Eighty-four of 142 patients with positive carbapenem-resistant P. aeruginosa cultures met the criteria of the Centers for Disease Control and Prevention for infection. Fifty-eight patients were infected with MBL-PA (69%) and 26 patients were infected with non-MBL-PA (31%). Multi-variate analysis revealed that ICU stay [P = 0.003, odds ratio (OR) 4.01, 95% confidence interval (CI) 1.15-14.01] and urinary tract infection (P = 0.001, OR 9.67, 95% CI 1.72-54.48) were important risk factors for MBL-PA infection. Patients infected with MBL-PA showed faster onset of infection (P = 0.002) and faster progression to death (P = 0.04).

CONCLUSIONS

These results showed the severity of MBL-PA infections, and demonstrated the urgent need for strategies to improve infection control measures to prevent an increase in these nosocomial infections.

Carbapenem-resistant Pseudomonas aeruginosa strains from a Spanish hospital: characterization of metallo-beta-lactamases, porin OprD and integrons

Molecular typing and mechanisms of carbapenem resistance such as alterations in porin OprD and presence of metallo-beta-lactamases (MBLs), as well as integrons have been studied in a collection of carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates from a Spanish hospital. One hundred and twenty-three CRPA isolates were recovered from different samples of 80 patients. Clonal relationship among CRPA was analyzed by SpeI-PFGE. Susceptibility testing to 11 antibiotics and MBL phenotype was determined by microdilution, IP/IPI E-test and double disc method. The oprD gene was studied by PCR and sequencing, and mutations were determined comparing with P. aeruginosa PAO1 sequence. Characterization of MBLs, and class 1 and 2 integrons were studied by PCR and sequencing. SDS-PAGE analysis of outer membrane proteins of selected strains was performed. Seventy-four-per-cent of patients with CRPA were hospitalised in the ICU setting and 50% had long hospitalization stays. Sixty-four different PFGE patterns were detected, and 87 CRPA strains were further analyzed. MBL phenotype was detected in 43 of 87 strains (49.4%), which contained blaVIM-2 gene inside class 1 integrons. VIM-2-producing strains belonged to lineages ST175, ST235, and ST973. A great diversity of nucleotide insertions, deletions, and mutations in oprD gene, and the presence of a new insertion sequence (ISPa45) truncating oprD were identified among CRPA strains. Class 1 integrons were detected in 75% of CRPA strains, blaVIM-2 and the new arrangement aac(3)-Ia+ISPa34+aadA1 (named as In661) being the most frequent gene-cassette arrays detected. Other gene cassettes detected in integrons were: aadB, aadA6, aadA7, aac(6')-Ib', and blaOXA-46.

First outbreak of VIM-2 metallo-β-lactamase-producing Pseudomonas aeruginosa in The Netherlands: microbiology, epidemiology and clinical outcomes

This study was designed to investigate the prevalence and characteristics of metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa in a tertiary care centre in The Netherlands, a country that is considered to have a low prevalence of antibiotic-resistant bacteria. Imipenem-resistant P. aeruginosa isolates cultured from clinical specimens during 2008-2009 were analysed phenotypically and molecularly by polymerase chain reaction (PCR) with sequencing. Genotyping was performed by multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA). Clinical information was obtained by electronic chart review for all patients infected or colonised with an imipenem-resistant P. aeruginosa isolate that was included in the study. In total, 106 imipenem-resistant P. aeruginosa isolates were included. The bla(VIM-2) gene was detected in 35/106 isolates (33%) and was associated with integrons. Compared with non-MBL-producing imipenem-resistant P. aeruginosa, VIM-2 MBL-producing isolates showed higher rates of multidrug resistance. Patients with VIM-2 MBL-producing isolates were more likely to be admitted to the Intensive Care Unit (ICU) and had a higher risk of invasive infection, including development of bacteraemia. MLVA identified two separate VIM-2 MBL-producing clones, responsible for outbreaks in the ICU but also affecting 10 other departments. This is the first reported outbreak of VIM-2 MBL-producing P. aeruginosa in The Netherlands. Once introduced, VIM-2 MBL-producing P. aeruginosa cause significant infections and are easily spread within the hospital setting.

The accessory genome of Pseudomonas aeruginosa

Pseudomonas aeruginosa strains exhibit significant variability in pathogenicity and ecological flexibility. Such interstrain differences reflect the dynamic nature of the P. aeruginosa genome, which is composed of a relatively invariable "core genome" and a highly variable "accessory genome." Here we review the major classes of genetic elements comprising the P. aeruginosa accessory genome and highlight emerging themes in the acquisition and functional importance of these elements. Although the precise phenotypes endowed by the majority of the P. aeruginosa accessory genome have yet to be determined, rapid progress is being made, and a clearer understanding of the role of the P. aeruginosa accessory genome in ecology and infection is emerging.

Intrahospital spread of carbapenem-resistant Pseudomonas aeruginosa in a University Hospital in Florianópolis, Santa Catarina, Brazil

INTRODUCTION: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) has been isolated with increasing frequency in Brazilian hospitals. Since June 2003, its detection in a teaching hospital in the city of Florianópolis, Brazil, has increased. This study aimed to investigate the minimal inhibitory concentration (MIC), presence of Metallo-β-lactamase (MβL) and a possible clonal relationship among the isolates. METHODS: The study included 29 CRPA and seven isolates with reduced susceptibility. The MIC was determined by agar-dilution. Detection of MβL was performed by Double Disk Sinergism (DDS) and Combined Disk (CD). The MβL gene was verified by PCR and nucleotide sequence analysis. Epidemiological typing was performed by pulsed-field gel electrophoresis. RESULTS: Among the 29 carbapenem-resistant isolates, polymyxin B presented 100% susceptibility and piperacillin/tazobactam 96.7%. Seventeen (62%) strains were verified as clonal (A clone) and among these, six isolates indicated phenotypically positive tests for MβL and harbored the blaSPM-1 gene. The first CRPA isolates were unrelated to clone A, harbored blaIMP-16 and were phenotypically positive only by CD. CONCLUSIONS: The spread of a high-level of resistance clone suggests cross transmission as an important dissemination mechanism and has contributed to the increased rate of resistance to carbapenems. This study emphasizes the need for continuous surveillance and improved strategies.

Three decades of beta-lactamase inhibitors

Since the introduction of penicillin, beta-lactam antibiotics have been the antimicrobial agents of choice. Unfortunately, the efficacy of these life-saving antibiotics is significantly threatened by bacterial beta-lactamases. beta-Lactamases are now responsible for resistance to penicillins, extended-spectrum cephalosporins, monobactams, and carbapenems. In order to overcome beta-lactamase-mediated resistance, beta-lactamase inhibitors (clavulanate, sulbactam, and tazobactam) were introduced into clinical practice. These inhibitors greatly enhance the efficacy of their partner beta-lactams (amoxicillin, ampicillin, piperacillin, and ticarcillin) in the treatment of serious Enterobacteriaceae and penicillin-resistant staphylococcal infections. However, selective pressure from excess antibiotic use accelerated the emergence of resistance to beta-lactam-beta-lactamase inhibitor combinations. Furthermore, the prevalence of clinically relevant beta-lactamases from other classes that are resistant to inhibition is rapidly increasing. There is an urgent need for effective inhibitors that can restore the activity of beta-lactams. Here, we review the catalytic mechanisms of each beta-lactamase class. We then discuss approaches for circumventing beta-lactamase-mediated resistance, including properties and characteristics of mechanism-based inactivators. We next highlight the mechanisms of action and salient clinical and microbiological features of beta-lactamase inhibitors. We also emphasize their therapeutic applications. We close by focusing on novel compounds and the chemical features of these agents that may contribute to a "second generation" of inhibitors. The goal for the next 3 decades will be to design inhibitors that will be effective for more than a single class of beta-lactamases.

Emergence of extensive-drug-resistant Pseudomonas aeruginosa in a French university hospital

The aim of this study was to describe the molecular epidemiology and the mechanisms of resistance to beta-lactams of emerging extensive-drug-resistant Pseudomonas aeruginosa (XDRPA) in a tertiary-care university hospital over a three-year period. Analysis included antimicrobial susceptibility profiling and pulsed-field gel electrophoresis (PFGE). Resistance mechanisms to beta-lactams were identified: production of naturally occurring and acquired beta-lactamases, overproduction of MexAB-OprM and MexXY efflux systems and loss of porin OprD were assessed. Eighteen patients were colonised or infected with XDRPA which remained susceptible to colistin and, to a lesser extent, to rifampicin. beta-lactam resistance was, in most cases, due to the overproduction of AmpC, overproduction of the MexXY efflux system and loss of porin OprD. One isolate produced the class D extended-spectrum oxacillinase (OXA-ESBL) Oxa-28, but none produced metallo-beta-lactamase (MBL) or class A extended-spectrum beta-lactamase (ESBL). The XDRPA clustered in eight PFGE patterns and both the acquisition and loss of resistance determinants was observed within a single clone during its spread. The emergence of XDRPA isolates in our university hospital has been characterised by genotypic heterogeneity, variation of mechanisms of resistance to beta-lactams in a single clone and the predominance of chromosomally encoded resistance mechanisms.

Molecular epidemiology of outbreak-related pseudomonas aeruginosa strains carrying the novel variant blaVIM-17 metallo-beta-lactamase gene

A study was designed to investigate the molecular epidemiological characteristics of multidrug-resistant outbreak-related Pseudomonas aeruginosa isolates collected in a university hospital in northern Greece. Of 29 nonreplicate P. aeruginosa isolates resistant to carbapenems and ceftazidime, 14 were positive for metallo-beta-lactamase production. PCR analyses with primers specific for bla(VIM) and bla(IMP) revealed that 13 isolates carried a novel bla(VIM-2) gene variant, designated bla(VIM-17), and only 1 isolate carried bla(VIM-2), a gene predominant among P. aeruginosa strains in Greek hospitals. Pulsed-field gel electrophoresis of XbaI-digested genomic DNAs showed a close genetic relationship for 12 of 13 bla(VIM-17)-carrying outbreak-related isolates, which were of the O11 serotype; the clonally unrelated isolate carrying bla(VIM-17) was of the O12 serotype. PCR mapping strategies for the detection of class 1 integrons and sequencing approaches revealed the presence of integrons containing one bla(VIM) cassette flanked by two aacA29 cassettes. These integrons were similar but not identical to In59 (GenBank accession number AF263519) initially described in France. All isolates carrying bla(VIM-17), regardless of their genetic profile, had an identical integron, named In59.3, indicating that although the hospital outbreak was mainly due to clonal dissemination, the horizontal transmission of the bla(VIM-17)-containing integron among P. aeruginosa isolates should also have occurred. An outbreak-related isolate and a control strain, both of which carried the bla(VIM-2) gene but which were clonally distinct, had an identical integron, named In59.2, which differed only at the level of the bla(VIM) gene from In59.3 integrons, suggesting a common ancestry. The spread of the bla(VIM-17)-containing integron in clonally unrelated P. aeruginosa isolates without any evidence of plasmid carriage is probably associated with a transposon.

Metallo-beta-lactamase-producing Pseudomonas aeruginosa isolated from a large tertiary centre in Kenya

This study was designed to characterize the beta-lactamase content of carbapenem-resistant Pseudomonas aeruginosa isolates recovered during 2006 and 2007 in a large tertiary-care centre in Nairobi, Kenya. Molecular characterization was done using PCR and sequencing, and typing was performed using pulsed-field gel electrophoresis (PFGE). In total, 416 P. aeruginosa isolates were obtained during that period, of which 57 (13.7%) were resistant to carbapenems. All carbapenem-resistant isolates tested positive for metallo-beta-lactamase (MBL) production. All MBL isolates produced VIM-2 with two types of integron structures. PFGE identified three clonally related groups of VIM-2-producing P. aeruginosa, including a pan-resistant clone that was responsible for nosocomial outbreaks during 2006 and 2007 in the intensive-care unit. These findings suggest that continuous molecular surveillance needs to be performed to monitor the spread within the hospital of this pan-resistant strain. This study is the first report of VIM-2-producing P. aeruginosa from the African continent.