CTX-M-2 and a new CTX-M-39 enzyme are the major extended-spectrum beta-lactamases in multiple Escherichia coli clones isolated in Tel Aviv, Israel

Fecal Carriage of Extended-Spectrum β-Lactamase-/AmpC-Producing Escherichia coli in Pet and Stray Cats

Dogs have been reported as potential carriers of antimicrobial-resistant bacteria, but the role of cats has been poorly studied. The aim of this study was to investigate the presence and the risk factors associated with the fecal carriage of extended-spectrum β-lactamase and AmpC (ESBL/AmpC)-producing Escherichia coli (E. coli) in pet and stray cats. Fecal samples were collected between 2020 and 2022 from healthy and unhealthy cats and screened for ESBL/AmpC-producing E. coli using selective media. The presence of ESBL/AmpC-producing E. coli was confirmed by phenotypic and molecular methods. The evaluation of minimum inhibitory concentrations (MICs) was performed on positive isolates. Host and hospitalization data were analyzed to identify risk factors. A total of 97 cats' samples were collected, and ESBL/AmpC-producing E. coli were detected in 6/97 (6.2%), supported by the detection of blaCTX-M (100%), blaTEM (83.3%), and blaSHV (16.7%) genes and the overexpression of chromosomal ampC (1%). All E. coli isolates were categorized as multidrug-resistant. Unhealthy status and previous antibiotic therapy were significantly associated with ESBL/AmpC-producing E. coli fecal carriage. Our results suggest that cats may be carriers of ESBL/AmpC-producing E. coli, highlighting the need for antimicrobial stewardship in veterinary medicine and an antimicrobial-resistance surveillance program focusing on companion animals, including stray cats.

Fecal Carriage of Extended-Spectrum β-Lactamases and pAmpC Producing Enterobacterales in an Iranian Community: Prevalence, Risk Factors, Molecular Epidemiology, and Antibiotic Resistance

This study aimed to determine the prevalence and risk factors associated with intestinal carriage of extended-spectrum β-lactamases producing Enterobacterales (ESBL-PE) and plasmid-mediated AmpC β-lactamase producing Enterobacterales (AmpC-PE) in healthy children in Ardabil, Iran. A total of 305 fecal samples were collected. Isolates underwent antimicrobial susceptibility testing, phenotypic and genotypic identification of β-lactamase production, and epidemiologic molecular typing. In total, 21.5%, 1.5%, and 1.2% of volunteers were extended-spectrum β-lactamase (ESBL)-, AmpC-, and simultaneous ESBL/AmpC-PE carriers, respectively. Escherichia coli was the predominant ESBL producing bacterium (70.2%) found in ESBL-PE colonized subjects. Beyond ESBL positive isolates, bla _CTX-M group genes were the most common type (75.6%) and bla _TEM (non-bla _TEM-1 and non- bla _TEM-2) were in the second place (25.6%). Among bla _CTX-M genes, bla _CTX-M-1 (55.3%) and bla _CTX-M-15 (55.3%) were the most predominant types with equal prevalence. Some isolates were multi-enzyme producers. bla _CIT and bla _DHA genes were common AmpC type enzyme encoding genes found in AmpC-PE isolates. Most isolates produced both enzymes at the same time. The number of students in the classes was statistically associated with ESBL-PE intestinal carriage (p < 0.05). Moreover, 46 (65.7%), 3 (60%), 4 (100%), and 98 (39.8%) ESBL-, AmpC-, ESBL/AmpC, and non-ESBL/AmpC-PE isolates were multidrug-resistant, respectively. Overall, regardless of β-lactam antibiotics, 62% and 59.5% of isolates were resistant to co-trimoxazole and tetracycline, respectively. The majority of ESBL producing E. coli isolates (69.2%) belonged to phylogroup A. According to Enterobacterial repetitive intergenic consensus polymerase chain reaction, there was no clonal relatedness between isolates. This study showed a high rate of multi-resistant ESBL-PE intestinal carriage among healthy individuals in Iran.

Comparison of approaches for source attribution of ESBL-producing Escherichia coli in Germany

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia (E.) coli have been widely described as the cause of treatment failures in humans around the world. The origin of human infections with these microorganisms is discussed controversially and in most cases hard to identify. Since they pose a relevant risk to human health, it becomes crucial to understand their sources and the transmission pathways. In this study, we analyzed data from different studies in Germany and grouped ESBL-producing E. coli from different sources and human cases into subtypes based on their phenotypic and genotypic characteristics (ESBL-genotype, E. coli phylogenetic group and phenotypic antimicrobial resistance pattern). Then, a source attribution model was developed in order to attribute the human cases to the considered sources. The sources were from different animal species (cattle, pig, chicken, dog and horse) and also from patients with nosocomial infections. The human isolates were gathered from community cases which showed to be colonized with ESBL-producing E. coli. We used the attribution model first with only the animal sources (Approach A) and then additionally with the nosocomial infections (Approach B). We observed that all sources contributed to the human cases, nevertheless, isolates from nosocomial infections were more related to those from human cases than any of the other sources. We identified subtypes that were only detected in the considered animal species and others that were observed only in the human population. Some subtypes from the human cases could not be allocated to any of the sources from this study and were attributed to an unknown source. Our study emphasizes the importance of human-to-human transmission of ESBL-producing E. coli and the different role that pets, livestock and healthcare facilities may play in the transmission of these resistant bacteria. The developed source attribution model can be further used to monitor future trends. A One Health approach is necessary to develop source attribution models further to integrate also wildlife, environmental as well as food sources in addition to human and animal data.

ESBL Producing Escherichia coli in Faecal Sludge Treatment Plants: An Invisible Threat to Public Health in Rohingya Camps, Cox's Bazar, Bangladesh

Introduction: Human faecal sludge contains diverse harmful microorganisms, making it hazardous to the environment and public health if it is discharged untreated. Faecal sludge is one of the major sources of E. coli that can produce extended-spectrum β-lactamases (ESBLs).

Objective: This study aimed to investigate the prevalence and molecular characterization of ESBL-producing E. coli in faecal sludge samples collected from faecal sludge treatment plants (FSTPs) in Rohingya camps, Bangladesh.

Methods: ESBL producing E. coli were screened by cultural as well as molecular methods and further characterized for their major ESBL genes, plasmid profiles, pathotypes, antibiotic resistance patterns, conjugation ability, and genetic similarity.

Results: Of 296 isolates, 180 were phenotypically positive for ESBL. All the isolates, except one, contained at least one ESBL gene that was tested (bla_CTX−M−1, bla_CTX−M−2, bla_CTX−M−8, bla_CTX−M−9, bla_CTX−M−15, bla_CTX−M−25, bla_TEM, and bla_SHV). From plasmid profiling, it was observed that plasmids of 1–211 MDa were found in 84% (151/180) of the isolates. Besides, 13% (24/180) of the isolates possessed diarrhoeagenic virulence genes. From the remaining isolates, around 51% (79/156) harbored at least one virulence gene that is associated with the extraintestinal pathogenicity of E. coli. Moreover, 4% (3/156) of the isolates were detected to be potential extraintestinal pathogenic E. coli (ExPEC) strains. Additionally, all the diarrhoeagenic and ExPEC strains showed resistance to three or more antibiotic groups which indicate their multidrug-resistant potential. ERIC-PCR differentiated these pathogenic isolates into seven clusters. In addition to this, 16 out of 35 tested isolates transferred plasmids of 32–112 MDa to E. coli J53 recipient strain.

Conclusion: The present study implies that the faecal sludge samples examined here could be a potential origin for spreading MDR pathogenic ESBL-producing E. coli. The exposure of Rohingya individuals, living in overcrowded camps, to these organisms poses a severe threat to their health.

Burden, Antibiotic Resistance, and Clonality of Shigella spp. Implicated in Community-Acquired Acute Diarrhoea in Lilongwe, Malawi

Although numerous studies have investigated diarrhoea aetiology in many sub-Saharan African countries, recent data on Shigella species’ involvement in community-acquired acute diarrhoea (CA-AD) in Malawi are scarce. This study investigated the incidence, antibiotic susceptibility profile, genotypic characteristics, and clonal relationships of Shigella flexneri among 243 patients presenting with acute diarrhoea at a District Hospital in Lilongwe, Malawi. Shigella spp. were isolated and identified using standard microbiological and serological methods and confirmed by identifying the ipaH gene using real-time polymerase chain reaction. The isolates’ antibiotic susceptibility to 20 antibiotics was determined using the VITEK 2 system according to EUCAST guidelines. Genes conferring resistance to sulfamethoxazole (sul1, sul2 and sul3), trimethoprim (dfrA1, dfrA12 and dfrA17) and ampicillin (oxa-1 and oxa-2), and virulence genes (ipaBCD, sat, ial, virA, sen, set1A and set1B) were detected by real-time PCR. Clonal relatedness was assessed using ERIC-PCR. Thirty-four Shigella flexneri isolates were isolated (an overall incidence of 14.0%). All the isolates were fully resistant to sulfamethoxazole/trimethoprim (100%) and ampicillin (100%) but susceptible to the other antibiotics tested. The sul1 (79%), sul2 (79%), sul3 (47%), dfrA12 (71%) and dfrA17 (56%) sulfonamide and trimethoprim resistance genes were identified; Oxa-1, oxa-2 and dfrA1 were not detected. The virulence genes ipaBCD (85%), sat (85%), ial (82%), virA (76%), sen (71%), stx (71%), set1A (26%) and set1B (18%) were detected. ERIC-PCR profiling revealed that the Shigella isolates were genetically distinct and clonally unrelated, indicating the potential involvement of genetically distinct S. flexneri in CA-AD in Malawi. The high percentage resistance to ampicillin and sulfamethoxazole/trimethoprim and the presence of several virulence determinants in these isolates emphasises a need for continuous molecular surveillance studies to inform preventive measures and management of Shigella-associated diarrhoeal infections in Malawi.

Wild Boars Carry Extended-Spectrum β-Lactamase- and AmpC-Producing Escherichia coli

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) represent major healthcare concerns. The role of wildlife in the epidemiology of these bacteria is unclear. The purpose of this study was to determine their prevalence in wild boars in Germany and to characterize individual isolates. A total of 375 fecal samples and 439 nasal swabs were screened for the presence of ESBL-/AmpC-E. coli and MRSA, respectively. The associations of seven demographic and anthropogenic variables with the occurrence of ESBL-/AmpC-E. coli were statistically evaluated. Collected isolates were subjected to antimicrobial susceptibility testing, molecular typing methods, and gene detection by PCR and genome sequencing. ESBL-/AmpC-E. coli were detected in 22 fecal samples (5.9%) whereas no MRSA were detected. The occurrence of ESBL-/AmpC-E. coli in wild boars was significantly and positively associated with human population density. Of the 22 E. coli, 19 were confirmed as ESBL-producers and carried genes belonging to bla_CTX-M group 1 or bla_SHV-12. The remaining three isolates carried the AmpC-β-lactamase gene bla_CMY-2. Several isolates showed additional antimicrobial resistances. All four major phylogenetic groups were represented with group B1 being the most common. This study demonstrates that wild boars can serve as a reservoir for ESBL-/AmpC-producing and multidrug-resistant E. coli.

Prevalence of blaCTX-M and Emergence of blaCTX-M-5-Carrying Escherichia coli in Chrysomya megacephala (Diptera: Calliphoridae), Northern Thailand

This study was undertaken to assess the prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-EC) among blow fly (Chrysomya megacephala) populations in Northern Thailand. Of 600 blow flies collected from rural (n = 400) and urban (n = 200) areas, 334 blow flies carried ESBL-EC (55.7%). Prevalence of ESBL-EC in blow flies captured from rural areas was significantly higher than that from urban region (72.5% vs. 22.0%, p < 0.001). Susceptibility tests revealed that 68.6% of ESBL-EC possessed multidrug-resistant phenotypes. Coresistance to gentamicin (85%) was common, while resistance to ciprofloxacin was relatively low (18.0%). Of the 334 isolates, 253 isolates (75.7%) harbored bla_CTX-M, in which bla_{CTX-M group 1} was predominant (56.5%), followed by bla_{CTX-M group 9} (39.1%). Interestingly, a single isolate was found to carry bla_CTX-M-5, which resided on the IncA/C conjugative plasmid. This is the first report of bla_CTX-M-5 from Thailand and its first identification in blow fly. Pulsed field gel electrophoresis (PFGE) demonstrated high genetic diversity among ESBL-EC isolates. Nevertheless, identical and closely related PFGE profiles were detected among isolates within the same regions and the regions which are several kilometers apart, suggesting that clonal transmission has occurred. Moreover, epidemiologically related isolates were observed between ESBL-EC from blow flies and human intestinal tract. This study provides evidences that blow flies, C. megacephala, are important reservoirs for ESBL-EC and could potentially act as vectors for the spread of ESBL-EC in a Thai community.

Association of intestinal colonization of ESBL-producing Enterobacteriaceae in poultry slaughterhouse workers with occupational exposure-A German pilot study

Background

Bacteria that have acquired antimicrobial resistance, in particular ESBL-producing Enterobacteriaceae, are an important healthcare concern. Therefore, transmission routes and risk factors are of interest, especially for the carriage of ESBL-producing E. coli. Since there is an enhanced risk for pig slaughterhouse employees to carry ESBL-producing Enterobacteriaceae, associated with animal contact as potential risk factor, the present study investigated the occurrence of ESBL-producing Enterobacteriaceae in poultry slaughterhouse employees. Due to the higher level of resistant Enterobacteriaceae in primary poultry production than in pig production, a higher risk of intestinal colonization of poultry slaughterhouse employees was expected.

Results

ESBL-producing Enterobacteriaceae were detected in 5.1% (5 of 99) of the fecal samples of slaughterhouse workers. The species of these isolates was confirmed as E. coli. PCR assays revealed the presence of the genes bla_CTX-M-15 (n = 2) and bla_SHV-12 (n = 3) in these isolates, partly in combination with the β-lactamase gene bla_TEM-135. Participants were divided into two groups according to their occupational exposure and results indicated an increased probability of colonization with ESBL-producing Enterobacteriaceae for the group of ‘higher exposure’ (OR 3.7, exact 95% CI 0.6–23.5; p = 0.4). For intestinal colonization with ESBL-producing Enterobacteriaceae, a prevalence of 10% (3/30) was observed in the group of ‘higher exposure’ versus 2.9% (2/69) in the group of ‘lower exposure’. Employees in working steps such as ‘hanging’ poultry in the process of slaughter and ‘evisceration’ seemed to have a higher risk for intestinal colonization with ESBL-producing Enterobacteriaceae compared to the group of ‘lower exposure’.

Conclusion

This study is the first of its kind to collect data on the occupational exposure of slaughterhouse workers to ESBL-producing Enterobacteriaceae in Europe. The results suggested that colonization with ESBL-producing Enterobacteriaceae is associated with occupational exposure in poultry slaughterhouses. However, the presence of ESBL-producing E. coli isolates in only 5.1% (5/99) of the tested employees in poultry slaughterhouses suggests a lower transmission risk than in pig slaughterhouses.

Antibiotic-resistant Escherichia coli isolated from urban rodents in Hanoi, Vietnam

Antimicrobial resistance (AMR) is a global public health concern for both clinical and veterinary medicine. Rodent feces are one of the major infectious sources of zoonotic pathogens including AMR bacteria. So far, there are limited studies reported focused on Escherichia coli isolated in rodent feces from rural and suburban areas in Vietnam. In this study, we investigated the prevalence of antimicrobial resistance in E. coli isolated from feces samples of 144 urban rodents caught in Hanoi, Vietnam. A total of 59 AMR E. coli was isolated from urban rodents of which 42 were multidrug-resistant (MDR) isolates (resistance to at least three classes of antimicrobial agents), four were extended-spectrum β-lactamase (ESBL) producing isolates and five were colistin-resistant isolates. The highest prevalence of the resistance was against ampicillin (79.7%: 47/59), followed by tetracycline (78.0%: 46/59), nalidixic acid (67.8%: 40/59), sulfamethoxazole-trimethoprim (59.3%: 35/59), chloramphenicol (45.8%: 27/59), ciprofloxacin (44.1%: 26/59), cefotaxime (30.5%: 18/59), cefodizime (23.7%: 14/59), amoxicillin-clavulanate (22.0%: 13/59), and gentamicin (22.0%: 13/59). With regard to the virulence genes associated with diarrheagenic E. coli (DEC), only aaiC gene found in one AMR isolate. In general, the use of antimicrobials does not aim to treat rodents except for companion animals. However, our findings show the carriage of AMR and MDR E. coli in urban rodents and highlight the potential risk of rodents in Hanoi acting as a reservoir of transferable MDR E. coli, including ESBL-producing, colistin-resistant E. coli, and virulence-associated with DEC.

Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in cattle production - a threat around the world

Food producing animal is a global challenge in terms of antimicrobial resistance spread. Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae are relevant opportunistic pathogens that may spread in many ecological niches of the One Health approach as human, animal and environment due to intestinal selection of antimicrobial resistant commensals in food production animals. Cattle production is a relevant ecological niche for selection of commensal bacteria with antimicrobial resistance from microbiota. Enterobacteriaceae show importance in terms of circulation of resistant-bacteria and antimicrobial resistance genes via food chain creating a resistance reservoir, setting up a threat for colonization of humans and consequent health risk. ESBL-producing Enterobacteriaceae are a threat in terms of human health responsible for life threatening outbreaks and silent enteric colonization of community populations namely the elder population. Food associated colonization is a risk difficult to handle and control. In a time of globalization of food trading, population intestinal colonization is a mirror of food production and in that sense this work aims to make a picture of ESBL-producing Enterobacteriaceae in animal production for food over the world in order to make some light in this reality of selection of resistant threats in food producing animal.

Occurrence of diverse aminoglycoside modifying enzymes with co-existing extended-spectrum-β-lactamases within Enterobacteriaceae isolated in India

OBJECTIVE

The present study describes aminoglycoside modifying enzymes (AMEs) among clinical isolates with coexisting extended spectrum beta-lactamases.

METHODOLOGY

A total of 227 non duplicate enterobacterial isolates were collected and identified from patients who were admitted to different wards or attended OPD of a tertiary referral hospital of North-East India. Isolates were initially screened for antimicrobial susceptibility testing followed by PCR based screening of aminoglycosides modifying enzymes and co-existing ESBLs and carbapenemases. Horizontal transferability, incompatibility typing and stability of plasmids were also analyzed.

RESULTS

Diverse types of AMEs were observed namely; ant(3″)-I, ant(4')-Ia, aac(3)-IIc, ant(3')-I, aac(6')-Ib, ant(2″)-Ia and aac(6'). Majority of the AME positive isolates harboured bla_TEM followed by bla_CTX-M-15 and a combination of bla_TEM and bla_CTX-M-15 were also observed. Nine isolates were found to harbour carbapenemases genes. AME genes were found to be located within a self conjugative plasmid of Inc FIA, IncY, IncN, IncFIB and IncA/C incompatibility types. It was observed that most AME genes were stable over 50 days of serial passages whereas aph(3')-Via and aph(3')-IIb were completely lost within 50 days.

CONCLUSION

This study underscores the co-existence of AMEs and ESBLs within enterobacteriaceae which emphasize a reassessment of combination therapy in the health settings.

Characterization of Unexpressed Extended-Spectrum Beta-Lactamase Genes in Antibiotic-Sensitive Klebsiella pneumoniae Isolates

OBJECTIVE

The current investigation explores whether extended-spectrum β-lactamase (ESBL) genes exist in clinical non-ESBL-producing Klebsiella pneumoniae isolates.

METHODS

A total of 202 clinical isolates with non-ESBL-producing K. pneumoniae were collected from southern and middle of China. Thirteen β-lactamase genes (bla_SHV, _CTX-M, _TEM, _OXA-2, _OXA-10, _VEB, _PER, _SFO, _GES, _CSP, _TLA, _BEL, _{and IBC}) were screened by PCR and their identity confirmed by sequencing of PCR products. The ESBL-producing phenotype of the isolates that carried ESBL genes was tested and confirmed in 9 of the 18 isolates by a double-disc synergy test. The sequences upstream of ESBL genes of isolates with ESBL-producing genotype (+)/phenotype (-) were also subjected to PCR and sequencing. The ESBL genes and their upstream regions were cloned into Escherichia coli DH5α for functional evaluation.

RESULTS

A total of 8.9% (18/202) isolates carried ESBL genes. All of them harbored only one ESBL gene, including 33.3% (6/18) bla_SHV and 66.7% (12/18) bla_CTX-M. Among the isolates carrying ESBL genes, nine isolates were confirmed as ESBL phenotype (-). The ESBL genotype (+)/phenotype (-) isolates had bla_{SHV-27,38,41,42} (66.7%, 6/9) and bla_{CTX-M-3,15,24} (33.3%, 3/9). The upstream gene sequences, including promoters of these unexpressed ESBL genes, were intact without any mutations or spacers and effective among eight strains. The ISEcp1 element in the upstream region was not found in one isolate carrying an unexpressed bla_CTX-M-15 gene.

CONCLUSIONS

Clinical non-ESBL-producing K. pneumoniae isolates could carry ESBL genes with intact promoter, but without the correlated phenotype. Specific silencing mechanisms may play an important role in regulating ESBL gene expression. This kind of isolates has the potential to transfer their ESBL genes to other bacteria with effective promoters, resulting in ESBL phenotype.

A multicenter study of the clonal structure and resistance mechanism of KPC-producing Escherichia coli isolates in Israel

Little is known about the molecular epidemiology of Klebsiella pneumoniae carbapenemase-producing Escherichia coli (KPCEC). We aimed to describe the clonal structure and resistance mechanisms of KPCEC in a multicenter study. The study included 88 isolates from four medical centres in Israel: Tel Aviv Medical Center (n = 17), Laniado Medical Center (n = 12), Sha'are-Zedek Medical Center (n = 38), and Rambam Medical Center (n = 21). Twelve (14%) KPCEC were from clinical sites and 86% from surveillance cultures. The clonal structure was studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) and was highly diverse, with 79 and 45 different PFGE types and STs, respectively. The most common clones were ST-131 and ST-410, identified in 21 isolates (23%). Dominant clonal complexes (CCs) were CC131 (n = 16), CC410 (n = 14), CC10 (n = 17), and CC-69 (n = 6). The blaKPC-2 and blaKPC-3 genes were identified in 68 and 20 isolates, respectively. All isolates were non-susceptible to ertapenem; 16 (18%) and 35 (40%) isolates were susceptible (minimal inhibitory concentration ≤1 mg/L) to imipenem and meropenem, respectively. Isolates were susceptible to colistin, amikacin, ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole in 100%, 87%, 28%, 27%, and 21% of the cases, respectively. blaKPC-Harbouring plasmids from Tel Aviv Medical Center as well as from six CC-131 isolates from the other centres were studied by Inc and pMLST typing. Sixteen of the 20 blaKPC2-harbouring plasmids were of identical type, IncN-pMLST ST-15. In conclusion, the clonal structure of KPCEC in Israel is characterized by the predominance of known international extended-spectrum β-lactamase-producing clones and by high intra- and inter-institutional diversity. This suggests that in Israel, clonal spread does not play a major role in the dissemination of KPCEC.

First Report of OXA-4, an ESBL Isolated from Pseudomonas aeruginosa a South Indian Strain

The OXA-type β-lactamases are so named because of their oxacillin-hydrolyzing abilities. In this study we characterize an extended spectrum β-lactamase, designated OXA-4, produced by a clinical isolate of Pseudomonas aeruginosa. ESBL production was detected by double disk synergy test. The P. aeruginosa isolate was obtained from endotracheal suction tip of 84 years old male patient diagnosed with CVA and hypertension. ESBL producing OXA β-lactamases was detected by PCR with primers specific to the conserved regions of the coding genes. Iso electric focusing was done to confirm the significance, sequencing the amplified product was also done. In the phenotypic identification, the strain was highly resistant to third generation cephalosporins and also to imipenem. The PCR amplified product for OXA β-lactamase was viewed at 919 bp. The pI point for the same was identified at 7.2. With the help of sequencing the amplified OXA β-lactamase was identified as OXA-4 gene. Here we report P. aeruginosa producing OXA-4 ESBL for the first time in the Indian subcontinent.

Structural diversity of class 1 integrons and their associated gene cassettes in Klebsiella pneumoniae isolates from a hospital in China

Background

Klebsiella pneumoniae strains carrying class 1 integrons are becoming more common worldwide, and their role in the dissemination of drug resistance is significant. The aim of this study was to characterize the structural diversity of class 1 integrons and their associated gene cassettes in K. pneumoniae isolates from hospital settings.

Methodology/Principal Findings

We analyzed a total of 176 K. pneumoniae isolates in a tertiary-care hospital in Beijing, China for the period of November 1, 2010-October 31, 2011. The presence of class 1 integrons and gene cassettes was analyzed by PCR and sequencing. The prevalence of class 1 integrons was 51.1% (90/176). Fourteen different gene cassettes and 10 different gene cassette arrays were detected. dfrA and aadA cassettes were predominant and cassette combination dfrA1-orfC was most frequently found (13.6%, 24/176). Strong association between resistance to a variety of drugs (both phenotypes and the associated genes) and the presence of class 1 integrons was observed. In addition, we also identified an association between some previously identified prevalent sequence types (such as ST11, ST15, ST147, ST562, and ST716) and the presence of class 1 integrons.

Conclusions/Significance

Data from this study demonstrated that class 1 integrons are highly diverse and are associated with a variety of drug resistance phenotypes, drug resistance genes, as well as genotypes among K. pneumoniae isolates. Continuous monitoring of gene cassettes in class 1 integrons is warranted to improve the understanding and control of drug resistance among hospital settings.

A binational cohort study of intestinal colonization with extended-spectrum β-lactamase-producing Proteus mirabilis in patients admitted to rehabilitation centres

The aims of our study were to analyse the risk factors for colonization by Extended-spectrum β-lactamases (ESBL)-producing Proteus mirabilis (ESBL-PM) in rehabilitation patients and to characterize the molecular features of these strains. The study was conducted in two rehabilitation centres located in Rome, Italy (Fondazione Santa Lucia IRCCS (FSL)), and Tel-Aviv, Israel (Tel-Aviv Sourasky Medical Center (TASMC)). Carriage of ESBL-PM was surveyed by rectal swabs. Strain typing was performed by pulsed-field gel electrophoresis (PFGE). Identification of ESBL genes was done by PCR and sequencing. Patients admitted to the same institutions without ESBL carriage were included as controls. The study group included 70 and 41 patients from FSL and TASMC, respectively. In FSL, the multivariate analysis identified severe acute brain injury (OR = 15, 95% CI = 3.2-69.5, p 0.001), decubitus ulcer (OR = 3.5, 95% CI = 1.2-9.8, p 0.018) and recent treatment with quinolones (OR = 5.7, 95% CI = 1.07-30.1, p 0.042) as independent risk factors. ESBL-PM carriers stayed longer in the hospital on average and were less likely to be discharged home. No significant risk factor was identified in TASMC. There were no similarities in PFGE types or ESBL genes between the ESBL-PM isolates from the two institutions. In both hospitals, a variety of PFGE types existed but a single ESBL type predominated, namely TEM-92 in FSL (n = 64/70; 91%) and CTX-M-2 in TASMC (n = 37/41; 90%). A new TEM ESBL variant, TEM-177 was identified in FSL. The clonal diversity and the predominance of a single ESBL type suggested that horizontal gene transfer played an important role in dissemination of resistance. The development of a population analysis tool that would allow tracing deeper genetic relationships is required.

Characterization of two new CTX-M-25-group extended-spectrum β-lactamase variants identified in Escherichia coli isolates from Israel

Objectives

We characterized two new CTX-M-type extended-spectrum β-lactamase (ESBL) variants in Escherichia coli isolates from stool samples of two elderly patients admitted at the Tel Aviv Sourasky Medical Center, Israel. Both patients underwent treatment with cephalosporins prior to isolation of the E. coli strains.

Methods

ESBLs were detected by the double-disk synergy test and PCR-sequencing of β-lactamase genes. The bla_CTX-M genes were cloned into the pCR-BluntII-TOPO vector in E. coli TOP10. The role of amino-acid substitutions V77A and D240G was analyzed by site-directed mutagenesis of the bla_CTX-M-94 and bla_CTX-M-100 genes and comparative characterization of the resulting E. coli recombinants. MICs of β-lactams were determined by Etest. Plasmid profiling, mating experiments, replicon typing and sequencing of bla_CTX-M flanking regions were performed to identify the genetic background of the new CTX-M variants.

Results

The novel CTX-M β-lactamases, CTX-M-94 and -100, belonged to the CTX-M-25-group. Both variants differed from CTX-M-25 by the substitution V77A, and from CTX-M-39 by D240G. CTX-M-94 differed from all CTX-M-25-group enzymes by the substitution F119L. Glycine-240 was associated with reduced susceptibility to ceftazidime and leucine-119 with increased resistance to ceftriaxone. bla_CTX-M-94 and bla_CTX-M-100 were located within ISEcp1 transposition units inserted into ∼93 kb non-conjugative IncFI and ∼130 kb conjugative IncA/C plasmids, respectively. The plasmids carried also different class 1 integrons.

Conclusions

This is the first report on CTX-M-94 and -100 ESBLs, novel members of the CTX-M-25-group.

Analysis of drug resistance determinants in Klebsiella pneumoniae isolates from a tertiary-care hospital in Beijing, China

Background

The rates of multidrug-resistant (MDR), extensively drug-resistant (XDR) and pandrug-resistant (PDR) isolates among Enterobacteriaceae isolates, particularly Klebsiella pneumoniae, have risen substantially worldwide.

Methodology/Principal Findings

To better understand the molecular mechanisms of drug resistance in K. pneumoniae, we analyzed the drug resistance determinants for K. pneumoniae isolates collected from the 306 Hospital, a tertiary-care hospital in Beijing, China, for the period of September 1, 2010-October 31, 2011. Drug susceptibility testing, PCR amplification and sequencing of the drug resistance determinants were performed. Conjugation experiments were conducted to examine the natural ability of drug resistance to disseminate among Enterobacteriaceae strains using a sodium azide-resistant Escherichia coli J53 strain as a recipient. Among the 223 consecutive non-repetitive K. pneumoniae isolates included in this study, 101 (45.3%) were extended-spectrum beta-lactamases (ESBLs) positive. The rates of MDR, XDR, and PDR isolates were 61.4% (n = 137), 22.0% (n = 49), and 1.8% (n = 4), respectively. Among the tested drug resistance-associated genes, the following ones were detected at relatively high rates bla_CTX-M-10 (80, 35.9%), aacC2 (73, 32.7%), dhfr (62, 27.8%), qnrS (58, 26.0%), aacA4 (57, 25.6%), aadA1 (56, 25.1%). Results from conjugation experiments indicate that many of the drug resistance genes were transmissible.

Conclusions/Significance

Our data give a “snapshot” of the complex genetic background responsible for drug resistance in K. pneumoniae in China and demonstrate that a high degree of awareness and monitoring of those drug resistance determinants are urgently needed in order to better control the emergence and transmission of drug-resistant K. pneumoniae isolates in hospital settings.

A swordless knight: epidemiology and molecular characteristics of the blaKPC-negative sequence type 258 Klebsiella pneumoniae clone

In June 2010, a bla(KPC)-negative, ertapenem-resistant ST-258 Klebsiella pneumoniae strain was isolated from a patient in the Laniado Medical Center (LMC). Our aims were (i) to describe its molecular characteristics and resistance mechanisms and (ii) to assess whether the bla(KPC)-negative ST-258 K. pneumoniae clone spreads as efficiently as its KPC-producing isogenic strain. In a prospective study, surveillance of all ertapenem-resistant, carbapenemase-negative K. pneumoniae (ERCNKP) isolates was conducted from June 2010 to May 2011 at LMC (314 beds) and from July 2008 to December 2010 at the Tel Aviv Sourasky Medical Center (TASMC) (1,200 beds). Molecular typing was done by arbitrarily primed PCR, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). A total of 8 of 42 (19%) ERCNKP isolates in LMC and 1 of 32 (3.1%) in TASMC belonged to the ST-258 clone. These strains carried the bla(CTX-M-2) or the bla(CTX-M-25) extended-spectrum β-lactamase (ESBL) gene. Sequencing of the ompK genes showed a frameshift mutation in the ompK35 gene. The fate of the bla(KPC)-carrying plasmid, pKpQIL, was determined by S1 analysis and by PCR of the Tn4401 transposon, repA, and the truncated bla(OXA-9). Plasmid analysis of the ERCNKP ST-258 isolates showed variability in plasmid composition and absence of the Tn4401 transposon and the pKpQIL plasmid. In addition, the ST-258 clone was identified in 35/35 (100%) of KPC-producing K. pneumoniae isolates but in none of 62 ertapenem-susceptible K. pneumoniae isolates collected in the two centers. Our results suggest that ERCNKP ST-258 evolved by loss of the bla(KPC)-carrying plasmid pKpQIL. ERCNKP ST-258 appears to have low epidemic potential.

Epidemiology and genetics of CTX-M extended-spectrum β-lactamases in Gram-negative bacteria

CTX-M enzymes, the plasmid-mediated cefotaximases, constitute a rapidly growing family of extended-spectrum β-lactamases (ESBLs) with significant clinical impact. CTX-Ms are found in at least 26 bacterial species, particularly in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. At least 109 members in CTX-M family are identified and can be divided into seven clusters based on their phylogeny. CTX-M-15 and CTX-M-14 are the most dominant variants. Chromosome-encoded intrinsic cefotaximases in Kluyvera spp. are proposed to be the progenitors of CTX-Ms, while ISEcp1, ISCR1 and plasmid are closely associated with their mobilization and dissemination.

Molecular characterization of resistance to extended-spectrum cephalosporins in clinical Escherichia coli isolates from companion animals in the United States

Resistance to extended-spectrum cephalosporins (ESC) among members of the family Enterobacteriaceae occurs worldwide; however, little is known about ESC resistance in Escherichia coli strains from companion animals. Clinical isolates of E. coli were collected from veterinary diagnostic laboratories throughout the United States from 2008 to 2009. E. coli isolates (n = 54) with reduced susceptibility to ceftazidime or cefotaxime (MIC ≥ 16 μg/ml) and extended-spectrum-β-lactamase (ESBL) phenotypes were analyzed. PCR and sequencing were used to detect mutations in ESBL-encoding genes and the regulatory region of the chromosomal gene ampC. Conjugation experiments and plasmid identification were conducted to examine the transferability of resistance to ESCs. All isolates carried the bla(CTX-M-1)-group β-lactamase genes in addition to one or more of the following β-lactamase genes: bla(TEM), bla(SHV-3), bla(CMY-2), bla(CTX-M-14-like), and bla(OXA-1.) Different bla(TEM) sequence variants were detected in some isolates (n = 40). Three isolates harbored a bla(TEM-181) gene with a novel mutation resulting in an Ala184Val substitution. Approximately 78% of the isolates had mutations in promoter/attenuator regions of the chromosomal gene ampC, one of which was a novel insertion of adenine between bases -28 and -29. Plasmids ranging in size from 11 to 233 kbp were detected in the isolates, with a common plasmid size of 93 kbp identified in 60% of isolates. Plasmid-mediated transfer of β-lactamase genes increased the MICs (≥ 16-fold) of ESCs for transconjugants. Replicon typing among isolates revealed the predominance of IncI and IncFIA plasmids, followed by IncFIB plasmids. This study shows the emergence of conjugative plasmid-borne ESBLs among E. coli strains from companion animals in the United States, which may compromise the effective therapeutic use of ESCs in veterinary medicine.

Extended-spectrum beta-lactamase-producing bacteria isolated from hematologic patients in Manaus, State of Amazonas, Brazil

Antibiotic therapy in hematologic patients, often weak and susceptible to a wide range of infections, particularly nosocomial infections derived from long hospitalization periods, is a challenging issue. This paper presents ESBL-producing strains isolated from such hematologic patients treated at the Amazon Hematology and Hemotherapy Foundation (HEMOAM) in the Brazilian Amazon Region to identify the ESBL genes carried by them as well as the susceptibility to 11 antimicrobial agents using the E-test method. A total of 146 clinical samples were obtained from July 2007 to August 2008, when 17 gram-negative strains were isolated in our institution. The most frequent isolates confirmed by biochemical tests and 16S rRNA sequencing were E. coli (8/17), Serratia spp. (3/17) and B.cepacia (2/17). All gram-negative strains were tested for extended-spectrum-beta-lactamases (ESBLs), where: (12/17) strains carried ESBL; among these, (8/12) isolates carried bla TEM, bla CTX-M, bla OXA , bla SHV genes, (1/12) bla TEM gene and (3/12) bla TEM, bla CTX-M, bla OXA genes. Antibiotic resistance was found in (15/17) of the isolates for tetracycline, (12/17) for ciprofloxacin, (1/17) resistance for cefoxitin and chloramphenicol, (1/17) for amikacin and (3/17) cefepime. This research showed the presence of gram-negative ESBL-producing bacteria infecting hematologic patients in HEMOAM. These strains carried the bla TEM, bla SHV, bla CTX-M and bla OXA genes and were resistant to different antibiotics used in the treatment. This finding was based on a period of 13 months, during which clinical samples from specific populations were obtained. Therefore, caution is required when generalizing the results that must be based on posological orientations and new breakpoints for disk diffusion and microdilution published by CLSI 2010.

Carbapenem-resistant KPC-2-producing Escherichia coli in a Tel Aviv Medical Center, 2005 to 2008

All of the carbapenem-resistant Escherichia coli (CREC) isolates identified in our hospital from 2005 to 2008 (n = 10) were studied. CREC isolates were multidrug resistant, all carried bla(KPC-2), and six of them were also extended-spectrum beta-lactamase producers. Pulsed-field gel electrophoresis indicated six genetic clones; within the same clone, similar transferable bla(KPC-2)-containing plasmids were found whereas plasmids differed between clones. Tn4401 elements were identified in all of these plasmids.

Treatment with fluoroquinolones or with beta-lactam-beta-lactamase inhibitor combinations is a risk factor for isolation of extended-spectrum-beta-lactamase-producing Klebsiella species in hospitalized patients

Antibiotic exposure exerts strong selective pressure and is an important modifiable risk factor for antibiotic resistance. We aimed to identify the role of various antibiotics as risk factors for the isolation of extended-spectrum-beta-lactamase (ESBL)-producing Klebsiella spp. in hospitalized patients at a tertiary-care hospital. A parallel multivariable model was created to compare two groups of cases with either nosocomially acquired ESBL- or non-ESBL-producing Klebsiella spp. to a common control group of hospitalized patients (a case-case-control design). Seventy-eight ESBL cases, 358 non-ESBL cases, and 444 controls were analyzed. Significant factors associated with the isolation of Klebsiella spp. were an age of >65 years, transfer from a health care facility, an intensive care unit (ICU) stay, and the presence of a comorbid malignancy or lung, hepatic, or renal disease. A propensity score was generated from the above, and our ability to discriminate between Klebsiella cases and controls (area under the receiver-operating-characteristic [ROC] curve, 0.78) was good. The ESBL phenotype was tightly linked with fluoroquinolone resistance (95% versus 18%, P < 0.001). Factors associated with isolation of ESBL Klebsiella spp. in a multivariable analysis, adjusting for the propensity score, included exposure to beta-lactam-beta-lactamase inhibitor combinations (odds ratio [OR], 10.17; 95% confidence interval [CI], 1.19 to 86.92) and to fluoroquinolones (OR, 2.86; 95% CI, 1.37 to 5.97). Exposure to broad-spectrum cephalosporins was statistically associated with ESBL Klebsiella spp. only among the subgroup of patients not treated with fluoroquinolones. In our institution, where the ESBL-producing-Klebsiella phenotype is coselected with fluoroquinolone resistance, fluoroquinolone and beta-lactam-beta-lactamase inhibitor combinations, rather than cephalosporins, are the main risk factors for ESBL isolates. Formulary interventions to limit the spread of ESBL-producing isolates should be tailored to each setting.

Ertapenem resistance among extended-spectrum-beta-lactamase-producing Klebsiella pneumoniae isolates

Ertapenem resistance in Klebsiella pneumoniae is rare. We report on an ertapenem-nonsusceptible phenotype among 25 out of 663 (3.77%) extended-spectrum-beta-lactamase (ESBL)-producing K. pneumoniae isolates in a multicenter Israeli study. These isolates originated from six different hospitals and were multiclonal, belonging to 12 different genetic clones. Repeat testing using Etest and agar dilution confirmed ertapenem nonsusceptibility in only 15/663 (2.3%) of the isolates. The molecular mechanisms of ertapenem resistance in seven single-clone resistant isolates was due to the presence of ESBL genes (CTX-M-2 in four isolates, CTX-M-10 and OXA-4 in one isolate, SHV-12 in one isolate, and SHV-28 in one isolate) combined with the absence of OMPK36. Seven of 10 isolates initially reported as ertapenem nonsusceptible and subsequently classified as susceptible showed an inoculum effect with ertapenem but not with imipenem or meropenem. Population analysis detected the presence of an ertapenem-resistant subpopulation at a frequency of 10(-6). These rare resistant subpopulations carried multiple ESBL genes, including TEM-30, SHV-44, CTX-M-2, and CTX-M-10, and they lacked OMPK36. The clinical and diagnostic significance of the results should be further studied.

Phenotypic and enzymatic comparative analysis of the novel KPC variant KPC-5 and its evolutionary variants, KPC-2 and KPC-4

A novel Klebsiella pneumoniae carbapenemase (KPC) variant, designated bla(KPC-5), was discovered in a carbapenem-resistant Pseudomonas aeruginosa clinical isolate from Puerto Rico. Characterization of the upstream region of bla(KPC-5) showed significant differences from the flanking regions of other bla(KPC) variants. Comparison of amino acid sequences with those of other KPC enzymes revealed that KPC-5 was an intermediate between KPC-2 and KPC-4, differing from KPC-2 by a single amino acid substitution (Pro(103)-->Arg), while KPC-4 contained Pro(103)-->Arg plus an additional amino acid change (Val(239)-->Gly). Transformation studies with an Escherichia coli recipient strain showed differences in the properties of the KPC variants. KPC-4 and KPC-5 both had pIs of 7.65, in contrast with the pI of 6.7 for KPC-2. KPC-2 transformants were less susceptible to the carbapenems than KPC-4 and KPC-5 transformants. These data correlated with higher rates of imipenem hydrolysis for KPC-2 than for KPC-4 and KPC-5. However, KPC-4 and KPC-5 transformants had higher ceftazidime MICs, and the enzymes from these transformants had slightly better hydrolysis of this drug than KPC-2. KPC-4 and KPC-5 were more sensitive than KPC-2 to inhibition by clavulanic acid in both susceptibility testing and hydrolysis assays. Thus, KPC enzymes may be evolving through stepwise mutations to alter their spectra of activity.

Plasmid-mediated 16S rRNA methylases in aminoglycoside-resistant Enterobacteriaceae isolates in Shanghai, China

High-level resistance to aminoglycosides produced by 16S rRNA methylases in Enterobacteriaceae isolates was investigated. The prevalences of armA in Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae were 0.6%, 3.0%, and 10%, respectively. rmtB was more prevalent than armA. Pulsed-field gel electrophoresis patterns indicated that armA and rmtB have spread horizontally and clonally.

Prevalence and spread of extended-spectrum beta-lactamase-producing Enterobacteriaceae in Europe

Extended-spectrum beta-lactamases (ESBLs) represent a major threat among resistant bacterial isolates. The first types described were derivatives of the TEM-1, TEM-2 and SHV-1 enzymes during the 1980s in Europe, mainly in Klebsiella pneumoniae associated with nosocomial outbreaks. Nowadays, they are mostly found among Escherichia coli isolates in community-acquired infections, with an increasing occurrence of CTX-M enzymes. The prevalence of ESBLs in Europe is higher than in the USA but lower than in Asia and South America. However, important differences among European countries have been observed. Spread of mobile genetic elements, mainly epidemic plasmids, and the dispersion of specific clones have been responsible for the increase in ESBL-producing isolates, such as those with TEM-4, TEM-24, TEM-52, SHV-12, CTX-M-9, CTX-M-14, CTX-M-3, CTX-M-15 and CTX-M-32 enzymes.

Interspecies spread of CTX-M-32 extended-spectrum beta-lactamase and the role of the insertion sequence IS1 in down-regulating bla CTX-M gene expression

OBJECTIVES

To characterize the extended-spectrum beta-lactamases (ESBLs) as well as their genetic environment in different isolates of Enterobacteriaceae from a patient with repeated urinary tract infections.

METHODS

Two isolates of Escherichia coli and one Proteus mirabilis, all with ESBL phenotypes, were studied. Conjugation experiments and restriction fragment length polymorphisms (RFLPs) were performed. Cloning of the bla genes was by plasmid restriction and fragments ligation. Antibiotic susceptibility testing was by Etest. The genetic environment was analysed by direct sequencing of the DNA surrounding the bla gene. RT-PCR was performed to study the differences in the bla(CTX-M) gene expression.

RESULTS

The bla gene was transferred by conjugation from the three clinical isolates, which by RFLP showed the same plasmid. The bla gene and surrounding sequences were cloned, an approximately 9 kbp AccI fragment was sequenced and the bla(CTX-M-32) gene was identified. The MICs of ceftazidime for transconjugants and transformants bearing the bla(CTX-M-32) gene were lower than those previously reported. Analysis of the DNA surrounding the ESBL gene revealed a new genetic structure with two insertion sequences, IS5 and IS1, located immediately upstream of the bla(CTX-M-32) gene; IS1 was located between the bla gene and IS5, and within the -10 and -35 promoter boxes of the bla(CTX-M-32) gene. Microbiological and biochemical studies revealed lower bla(CTX-M-32) gene expression in bacterial isolates with IS1 between the promoter boxes.

CONCLUSIONS

Data suggest putative in vivo horizontal bla(CTX-M-32) gene transfer between two different genera of Enterobacteriaceae. A new complex structure, IS5-IS1, was detected upstream of the bla gene and IS1 negatively modulated expression of the bla(CTX-M-32) gene because its location modified the bla promoter region.

Extended-spectrum β-lactamase-producing Shigella strains in Israel, 2000–2004

Routine susceptibility testing of 5,616 Shigella isolates at the National Shigella Reference Centre in Israel over a 5-year period (2000-2004) revealed resistance to ceftriaxone in one strain of Shigella boydii 2 and in two strains each of Shigella flexneri 2a, S. flexneri 6, and Shigella sonnei. All seven isolates were confirmed as producers of extended-spectrum beta-lactamase (ESBL) by the combination disk method, the Vitek 1 system, and a modification of the double-disk synergy test, which is based on the inhibitory properties of clavulanic acid, tazobactam, and sulbactam. Tazobactam had the strongest effect in all seven strains. Molecular characterization of the ESBLs identified CTX-M-type enzymes, consisting of the CTX-M-9 group (n = 3), CTX-M-3 (n = 2), CTX-M-39 (n = 1), and CTX-M-2 group (n = 1). Three of the strains also carried bla-(OXA) genes and a bla-(TEM) gene. Although the prevalence of ESBLs in this study was low, further research is needed on the spread and transfer of resistance genes, both in hospitals and in the community.

A novel reverse-line hybridization assay for identifying genotypes of CTX-M-type extended-spectrum β-lactamases

OBJECTIVES

To develop a reverse-line hybridization assay to identify CTX-M genotypes, potentially useful for large-scale investigation of surveillance collections.

METHODS

Isolates carrying previously characterized bla(CTX-M) genes were used to develop the method. In addition, 334 isolates from five separate surveys were used to validate the method. CTX-M group was known from an independent multiplex PCR for 122 isolates and genotype was confirmed for 80 isolates by DNA sequencing. A multiplex PCR was designed to amplify a genotype-specific region within the bla(CTX-M) open-reading frame. Oligonucleotides were designed to hybridize to regions within each amplicon, covering mutations that distinguish among bla(CTX-M) genotypes.

RESULTS

CTX-M phylogenetic groups were identified by the multiplex PCR with 100% concordance. The reverse-line hybridization assay specifically identified commonly-reported variants within these groups (98.7% concordance).

CONCLUSIONS

The hybridization method enabled precise identification of CTX-M genes, rather than just to group level, without the need for DNA sequencing. In its present format, the method enables 43 isolates to be processed per membrane, giving results within one working day. It is a useful tool for the epidemiological investigation of bla(CTX-M) genes among survey collections of Enterobacteriaceae.

Plasmid-mediated imipenem-hydrolyzing enzyme KPC-2 among multiple carbapenem-resistant Escherichia coli clones in Israel

Carbapenem resistance in Escherichia coli is rare. We report four genetically unrelated carbapenem-resistant E. coli isolates cultured from four patients hospitalized in Tel Aviv Medical Center. PCR, sequencing, and Southern blot analysis identified KPC-2 as the imipenem-hydrolyzing enzyme in all four strains, carried on different plasmids with a possible common origin. This is the first discovery of KPC-2 in E. coli and the first report of this enzyme originating outside the United States.

Characterisation of CTX-M and AmpC genes in human isolates of Escherichia coli identified between 1995 and 2003 in England and Wales

CTX-M and AmpC genes in human isolates of Escherichia coli, their genetic environment and their host plasmids were examined. Isolates (n=103) were selected based on resistance (minimum inhibitory concentration (MIC)> or =1 microg/mL) to ceftriaxone and cefotaxime. Polymerase chain reaction (PCR) and sequencing identified 29 isolates containing bla(CTX-M-15), 1 each of bla(CTX-M-2) (a strain originating from Israel) and bla(CTX-M-40), 20 isolates containing bla(CMY-7), 4 bla(CMY-2) and 1 bla(CMY-21). This is the first study of plasmid-mediated AmpC genes in E. coli in the UK. Eleven cefoxitin-resistant, AmpC PCR-negative isolates had ampC promoter region mutations. All bla(CTX-M-15) and 24 of 25 bla(CMY) genes were associated with an ISEcp1-like element. The bla(CTX-M-2) was located in an orf513-bearing class 1 integron. Plasmid restriction digests suggest transfer of genes between different plasmid backbones.

The beta-lactamase threat in Enterobacteriaceae, Pseudomonas and Acinetobacter

Over the past 60 years, the use of successive generations of beta-lactam antibiotics has selected successive generations of beta-lactamase enzymes, each more potent than the last. Currently, rising problems include CTX-M extended-spectrum beta-lactamases (ESBLs), plasmid-mediated AmpC beta-lactamases and KPC carbapenemases in Enterobacteriaceae, while OXA- and metallo- carbapenemases are of growing importance in Acinetobacter spp. and (less so) in other non-fermenters. Escherichia coli isolates with CTX-M ESBLs are spreading multiresistance in the community and in hospitals, while carbapenemase-producing Acinetobacter spp., mostly from intensive care, are among the most multiresistant nosocomial bacteria known and are often susceptible only to polymyxins and, potentially, tigecycline. This review discusses the epidemiology and microbiology of these resistance problems, along with possible solutions.