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Expanded-spectrum beta-lactamase producing Klebsiella pneumoniae-related peritonitis in a patient on peritoneal dialysis.

While hospitalized for pneumonia with ventilator-dependent respiratory failure, a 45-year-old man on continuous ambulatory peritoneal dialysis (CAPD) had nosocomial peritonitis secondary to infection by expanded spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-Kp). He was treated successfully with a 3-week course of intraperitoneal (IP) flomoxef therapy without subsequent relapse, loss of peritoneal catheter, ultrafiltration failure, or dialysis inadequacy. The International Consensus Panel recommends IP ceftazidime as the treatment of choice for CAPD patients suffering Klebsiella species-related peritonitis. However, the most appropriate form of IP antibiotic therapy and the outcomes for expanded-spectrum beta-lactamase (ESBL)-producing bacteria-related peritonitis for CAPD patients have not been established yet. Further, the ability to correctly report minimal inhibitory concentrations (MICs) of ceftazidime for ESBL bacteria in the resistant range varies between laboratories, making the diagnosis of ESBL-Kp-related CAPD peritonitis more complex and difficult. Thus, it appears reasonable to suggest that its incidence is probably underestimated and its significance ignored. The authors suggest that a 3-week IP treatment with flomoxef, a synthesized oxacephem, with loading and maintenance doses of 250 and 125 mg/L, respectively, is effective and safe for ESBL-Kp-related peritonitis in these patients. ESBL producing bacterial infection should be considered as a possible cause of overt CAPD-related peritonitis. Early detection of ESBLB pathogens and institution of effective antibiotic treatment may improve the prognosis.

Bacterial Proteins↗

Risk factors in the acquisition of extended-spectrum beta-lactamase Klebsiella pneumoniae: a case-control study in a district teaching hospital in Taiwan.

A case-control study was performed to find the risk factors in the acquisition of extended-spectrum beta-lactamase (ESBL) Klebsiella pneumoniae. From 1 May 2001 to 30 September 2001, 422 isolates ofK. pneumoniae identified by the microbiological laboratory in Hsin-Chu hospital were collected, 59 of which were ESBL-producing strains. The prevalence rate was 14% (59/422). There were 43 case patients (ESBL-producing K. pneumoniae) and 86 controls (non-ESBL-producing K. pneumoniae). Tracheostomy, insertion of a Foley catheter, endotracheal tube, nasogastric tube and central venous catheter were found to be risk factors in the acquisition of K. pneumoniae with ESBLs by univariate analysis. Tracheostomy (odds ratio, 5.13; 95% CI, 1.24-21.1;P =0.023) and ceftazidime use (odds ratio, 13.40; 95% CI, 1.21-148.85; P=0.035) remained as risk factors by multivariate analysis with logistic regression. Other anti-pseudomonal agents should be used as empirical therapy to treat possible Pseudomonas aeruginosa infection in order to reduce ceftazidime use and thereby decrease the prevalence of ESBL producing strains of Enterobacteriaceae.

Adult↗

Extended-spectrum beta-lactamases.

Extended-spectrum beta-lactamases (ESBLs) were discovered in Europe in the early 1980s after widespread use of broad-spectrum antibiotics. They are largely derivatives of 3 progenitor beta-lactamases that confer resistance to ampicillin in gram-negative bacteria and are now carried on plasmids. Substitutions at the active enzyme site of these progenitor enzymes at single or multiple amino sites have resulted in altered substrate affinities for ESBLs. Depending on the location of the substitution, susceptibility to broad-spectrum antibiotics is variably diminished. ESBLs are most commonly found in Klebsiella species and Escherichia coli, but also in other bacteria including Pseudomonas, Salmonella, Proteus, and Enterobacter species. The discovery of ESBLs in hospital and nursing-home outbreaks and their ability to be transferred to other bacterial species makes management and treatment of ESBLs of great medical concern.This article provides a review of ESBLs and their impact on patient care.

Bacterial Infections↗

Detection of extended spectrum beta-lactamases in the routine clinical microbiology laboratory.

AIMS: To compare three methods of confirming the presence of an extended spectrum beta-lactamase (ESBL) enzyme with the initial detection (i.e., screening) by the Vitek AMS. METHODS: Gram-negative bacteria which flagged as ESBL-positive in the Vitek GNS card, or were suspected of harbouring an enzyme, were further tested by each of the following methods: (a) combination disc test using cefpodoxime, ceftazidime and cefotaxime with and without clavulanate; (b) cefotaxime ESBL Etest; and (c) Jarlier keyhole method with cefpodoxime (10 microg), cefotaxime (5 microg) and aztreonam (30 microg) placed 15mm away from an augmentin (30 microg) disc. RESULTS: A total of 52 isolates were investigated, representing an 18-month time period. Fifty of these were positive by Vitek. Twenty-eight (56%) were confirmed by other methods (true positives). Of the 44% Vitek-positive/confirmatory test-negative (false positives), eight were Escherichia coli which was 53% of all E. coli tested. The majority of other false-positive isolates were Klebsiella oxytoca (24% overall) which were all Vitek- and Etest-positive but negative by the combination disc test. CONCLUSIONS: All ESBL-positive strains by Vitek should be confirmed by the combination disc test using all three antibiotics. This will enable differentiation of 'true' ESBLs from false-positive organisms, including K1 hyperbetalactamase-producing Klebsiella oxytoca and AmpC-producing organisms. The cefpodoxime combination discs gave the best differentiation in this study with only one ESBL organism being missed.

Adult↗

Modified double-disc test for detection of extended-spectrum beta-lactamases in Escherichia coli and Klebsiella pneumoniae.

This study evaluates the performance of a modified double-disc test (MDDT) for the detection of extended-spectrum beta-lactamases (ESBLs) in clinical isolates of Escherichia coli and Klebsiella pneumoniae. Ninety-six isolates of E. coli and 40 K. pneumoniae are studied for ESBL production by the National Committee for Clinical Laboratory Standards (NCCLS) combination disc tests and MDDT A total of 112 (82%) isolates (80 [83%] E. coli, 32 [80%] K. pneumoniae) were positive for ESBL by MDDT compared to 102 (75%; 72 [75%] E. coli and 30 [75%] K. pneumoniae) by the NCCLS method. In 10 (7.4%) isolates, ESBLs were detected only by MDDT Twenty-four (17.6%) isolates were negative for ESBL by both methods. The protocol described in this study provides a more sensitive approach than does the NCCLS method for ESBL detection in E. coli and K. pneumoniae.

Anti-Bacterial Agents↗

Epidemiology of ciprofloxacin resistance and its relationship to extended-spectrum beta-lactamase production in Klebsiella pneumoniae isolates causing bacteremia.

A prospective study of Klebsiella pneumoniae bacteremia was performed in 12 hospitals in 7 countries. Of 452 episodes of bacteremia, 25 (5.5%) were caused by K. pneumoniae that was resistant in vitro to ciprofloxacin. Extended-spectrum beta-lactamase (ESBL) production was detected in 15 (60%) of 25 ciprofloxacin-resistant isolates, compared with 68 (16%) of 427 ciprofloxacin-susceptible strains (P=.0001). Multivariate analysis revealed that risk factors for ciprofloxacin resistance in K. pneumoniae included prior receipt of a quinolone (P=.0065) and an ESBL-producing strain (P=.012). In all, 18% of ESBL-producing isolates were also ciprofloxacin-resistant. Pulsed-field gel electrophoresis showed that 11 of the 15 ciprofloxacin-resistant ESBL-producing strains belonged to just 4 genotypes, suggesting that patient-to-patient transmission of such strains occurred. The close relationship between ESBL production and ciprofloxacin resistance is particularly worrisome because the first reported instance of plasmid-mediated ciprofloxacin resistance has been in an isolate of K. pneumoniae also possessing an ESBL.

Anti-Infective Agents↗

Antibiotic therapy for Klebsiella pneumoniae bacteremia: implications of production of extended-spectrum beta-lactamases.

The prevalence of extended-spectrum beta -lactamase (ESBL) production by Klebsiella pneumonia approaches 50% in some countries, with particularly high rates in eastern Europe and Latin America. No randomized trials have ever been performed on treatment of bacteremia due to ESBL-producing organisms; existing data comes only from retrospective, single-institution studies. In a prospective study of 455 consecutive episodes of Klebsiella pneumoniae bacteremia in 12 hospitals in 7 countries, 85 episodes were due to an ESBL-producing organism. Failure to use an antibiotic active against ESBL-producing K. pneumoniae was associated with extremely high mortality. Use of a carbapenem (primarily imipenem) was associated with a significantly lower 14-day mortality than was use of other antibiotics active in vitro. Multivariate analysis including other predictors of mortality showed that use of a carbapenem during the 5-day period after onset of bacteremia due to an ESBL-producing organism was independently associated with lower mortality. Antibiotic choice is particularly important in seriously ill patients with infections due to ESBL-producing K. pneumoniae.

Anti-Bacterial Agents↗

Overview of the epidemiological profile and laboratory detection of extended-spectrum beta-lactamases.

Extended-spectrum beta-lactamases (ESBLs) are plasmid-mediated bacterial enzymes that confer resistance to a broad range of beta-lactams. They are descended by genetic mutation from native beta-lactamases found in gram-negative bacteria, especially infectious strains of Escherichia coli and Klebsiella species. Genetic sequence modifications have broadened the substrate specificity of the enzymes to include third-generation cephalosporins, such as ceftazidime. Because ESBL-producing strains are resistant to a wide variety of commonly used antimicrobials, their proliferation poses a serious global health concern that has complicated treatment strategies for a growing number of hospitalized patients. Another resistance mechanism, also common to Enterobacteriaceae, results from the overproduction of chromosomal or plasmid-derived AmpC beta-lactamases. These organisms share an antimicrobial resistance pattern similar to that of ESBL-producing organisms, with the prominent exception that, unlike most ESBLs, AmpC enzymes are not inhibited by clavulanate and similar beta-lactamase inhibitors. Recent technological improvements in testing and in the development of uniform standards for both ESBL detection and confirmatory testing promise to make accurate identification of ESBL-producing organisms more accessible to clinical laboratories.

Enterobacteriaceae↗

Production of CTX-M-3 extended-spectrum beta-lactamase and IMP-1 metallo beta-lactamase by five Gram-negative bacilli: survey of clinical isolates from seven laboratories collected in 1998 and 2000, in the Kinki region of Japan.

The aim of this study was to research the distribution in the Kinki region of Japan of Enterobacteriaceae and Pseudomonas aeruginosa that produce extended-spectrum beta-lactamase (ESBL) and metallo beta-lactamase (MBL). One thousand isolates, 200 of each of four enterobacterial species (i.e. Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae and Serratia marcescens) and 200 of P. aeruginosa, were collected from seven different laboratories during two 2 month periods, one in 1998 and one in 2000. A double-disc synergy test (DDST) and 2-mercaptopropionic acid inhibition test (2-MPAT) were used to confirm beta-lactamase-producing isolates. The DDST was positive for one isolate of E. coli, five of K. pneumoniae, two of E. cloacae and 14 of S. marcescens. The 2-MPAT was positive for five isolates of S. marcescens and two of P. aeruginosa. We identified the beta-lactamase type of each isolate by molecular confirmatory tests (isoelectric focusing, PCR and DNA sequencing): CTX-M-3 ESBLs (three isolates of K. pneumoniae, two of E. cloacae and 13 of S. marcescens), CTX-M-2 ESBL (one isolate of K. pneumoniae), SHV-12 ESBLs (one isolate of E. coli and one of S. marcescens), CTX-M-3 and SHV-12 combination ESBL (one isolate of K. pneumoniae) and IMP-1 MBLs (five isolates of S. marcescens and two of P. aeruginosa). In conclusion, many species of Gram-negative bacilli that produce CTX-M-3 ESBLs and IMP-1 MBLs were disseminated widely in different hospitals of the Kinki region of Japan. Therefore, monitoring of laboratory bacterial ecology seems important to stop the spread of these strains through nosocomial outbreaks.

Cross Infection↗

Predominance and genetic diversity of community- and hospital-acquired CTX-M extended-spectrum beta-lactamases in York, UK.

OBJECTIVES: This study was conducted to detect the presence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae within the faecal flora of both community- and hospital-based patients in York and to characterize the bla(TEM), bla(SHV) and bla(CTX-M) genes present in these isolates. METHODS: One thousand faeces samples were collected and screened at York Hospital during October-December 2003. Ninety-five non-duplicate Enterobacteriaceae isolates resistant to third-generation cephalosporins were recovered; 22 isolates were selected for further study on the basis of a positive double disc diffusion test for ESBL production. Antibiotic susceptibility testing was performed to a range of antibiotics. The TEM, SHV and CTX-M genes were detected by PCR and the DNA sequenced. RESULTS: The distribution of ESBL-positive isolates from the hospital and community was 1.4:1. These included nine Escherichia coli, seven Enterobacter cloacae, four Citrobacter freundii and a single isolate each of Klebsiella spp. and Salmonella spp. A total of 17 isolates contained bla(CTX-M) (five bla(CTX-M-15), three bla(CTX-M-14) and nine bla(CTX-M-9)). ISEcp1 was present in isolates expressing CTX-M-14 and -15, but was absent upstream of In60-associated bla(CTX-M-9). E. coli isolates also contained either a bla(TEM-1) or bla(TEM-2), whereas six of the E. cloacae carried bla(SHV-12) and the Klebsiella spp. bla(SHV-36) in addition to bla(CTX-M-9). The single Salmonella spp. carried bla(SHV-12). CONCLUSIONS: The overall prevalence of ESBL in isolates of Enterobacteriaceae from York was 1.9%. ESBL-producing isolates were found in both the community and hospital, with the CTX-M type most common. This is also the first report of an ESBL-producing Salmonella in the UK.

Community-Acquired Infections↗

Detection and characterization of extended-spectrum beta-lactamases among bloodstream isolates of Enterobacter spp. in Hong Kong, 2000-2002.

OBJECTIVES: A total of 139 consecutive and non-duplicate bloodstream isolates of Enterobacter spp. collected from inpatients in Hong Kong during 2000-2002 were studied for production of extended-spectrum beta-lactamases (ESBLs). METHODS: All isolates were evaluated by the modified double-disc synergy test (m-DDST), the combined disc method (CDM) and the three-dimensional (3D) test. The m-DDST and CDM were modified by the use of cefepime discs. beta-Lactamases were characterized by isoelectric focusing and PCR sequencing using specific primers. RESULTS: ESBLs were identified in nine isolates (overall 6.5%), including seven of 39 (17.9%) Enterobacter hormaechei, one of 27 (3.7%) Enterobacter aerogenes and the only Enterobacter intermedius strain. The E. intermedius strain was positive only in the 3D test but not in the other two tests. The other eight strains were positive in all three tests. No ESBL was detected in the other species, including non-hormaechei members of the Enterobacter cloacae complex (n=61), Enterobacter agglomerans (n=7), Enterobacter gergoviae (n=4) and Enterobacter sakazakii (n=1). The ESBL content included five different CTX-M enzymes (CTX-M-9, CTX-M-13, CTX-M-14, CTX-M-24 and a novel CTX-M-2-like beta-lactamase), SHV-12 (n=2) and unidentifiable ESBLs with a pI of 7.7 or 7.9 in two strains. The seven ESBL-producing E. hormaechei were genotyped by pulsed-field gel electrophoresis and were found to be unrelated to each other. In three of the CTX-M-producing strains, ISEcp1-like elements, including promoters for the beta-lactamase gene, were found. CONCLUSIONS: Our data underscore the diversity of CTX-M enzymes among Enterobacter spp. in Hong Kong.

Bacteremia↗

Disc diffusion-based screening tests for extended-spectrum beta-lactamases in Haemophilus influenzae.

OBJECTIVES: To establish a suitable screening test for the detection of extended-spectrum beta-lactamases (ESBLs) in Haemophilus influenzae. METHODS: Double disc diffusion tests using cephalosporin discs adjacent to an amoxicillin/clavulanate 3 microg disc, prediffusion tests, where an amoxicillin/clavulanate 3 microg disc was prediffused before being replaced with a cephalosporin disc, and combination cephalosporin/clavulanate discs were used to screen recombinant H. influenzae expressing cloned ESBLs. Methods initially determined to be suitable were validated by testing a range of clinical strains. RESULTS: Enhanced zones around cephalosporin discs due to synergy with an adjacent amoxicillin/clavulanate disc were not reliably demonstrated with the recombinant H. influenzae strains expressing ESBLs. Cefotaxime 5 microg or 30 microg and cefpodoxime 10 microg discs prediffused with an amoxicillin/clavulanate 3 microg disc, and cefotaxime 30 microg/clavulanate 10 microg and cefpodoxime 10 microg/clavulanate 1 microg combination discs all gave zone sizes > or = 5 mm greater than the corresponding plain disc for all recombinant ESBL-producing strains. None of the clinical strains gave enhanced zones. CONCLUSIONS: Cefotaxime 5 or 30 microg or cefpodoxime 10 microg discs prediffused with an amoxicillin/clavulanate 3 microg disc, or cefotaxime 30 microg/clavulanate 10 microg and cefpodoxime 10 microg/clavulanate 1 mug combination discs are all suitable for screening H. influenzae isolates for the presence of ESBLs. ESBL-producing strains should show an increase in zone diameter of > or = 5 mm compared with the corresponding plain cephalosporin disc.

Amoxicillin↗

Molecular epidemiology of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a neonatal intensive care unit.

OBJECTIVES: To investigate the molecular epidemiology of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae in the neonatal intensive care unit of a university hospital in Italy. METHODS: Antibiotic susceptibility was evaluated by disc diffusion and Etest. ESBLs were identified by isoelectric focusing, PCR and DNA sequencing analysis. Genotyping was performed by PFGE analysis. Conjugation was performed by broth mating. RESULTS: Molecular typing of K. pneumoniae isolates identified three distinct PFGE patterns. Isolates of PFGE profile A were isolated during an epidemic in 1996, while isolates of PFGE profiles B and C were sequentially isolated from September 2002 to December 2004, when 233 colonizations and 19 infections by K. pneumoniae occurred. All K. pneumoniae strains of different PFGE types were identified as ESBL producers. DNA sequencing of amplified beta-lactamase genes identified a novel bla(TEM) ESBL (bla(TEM-136)) along with bla(SHV-1) in chromosomal and plasmid DNA from K. pneumoniae of PFGE type A, respectively, and bla(TEM-1) and bla(SHV-12) in plasmid DNA from K. pneumoniae of PFGE types B and C. Conjugation experiments demonstrated that resistance to third-generation cephalosporins, along with an approximately 80 kb plasmid containing bla(SHV-12) and bla(TEM-1), was transferred from K. pneumoniae epidemic strains of PFGE types B and C to a susceptible Escherichia coli host at a frequency of 4 x 10(-6) and 1 x 10(-6) cfu/recipient cell, respectively. CONCLUSIONS: The selection of ESBL-producing clones and the transfer of the bla(SHV-12) ESBL gene between different clones were responsible for the spread of K. pneumoniae in the neonatal intensive care unit.

Anti-Bacterial Agents↗

Extended-spectrum beta-lactamase-producing Enterobacteriaceae in different environments (humans, food, animal farms and sewage).

OBJECTIVES: This study aimed to determine the presence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in different environments. METHODS: Clinical samples and stool samples from animal farms, sewage, human faecal carriers attending the emergency room and faecal carriers in the context of food-borne disease outbreaks were subcultured onto MacConkey agar supplemented with cefotaxime for the detection of ESBL-producing Enterobacteriaceae. Identification, susceptibility pattern and ERIC-PCR were used for clone delineation in each sample. Community consumption of antibiotics was also recorded. RESULTS: An ESBL-producing Enterobacteriaceae prevalence of 1.9% was observed in human infections. A cross-sectional survey of human faecal carriers in the community showed a general prevalence of 6.6% with a temporal distribution. High use of antibiotics in winter coincided with a lower prevalence in carriers. ESBL-producing Enterobacteriaceae were detected in the five samples of human sewage, in samples from 8 of 10 pig farms, 2 of 10 rabbit farms, from all 10 poultry farms and in 3 of 738 food samples studied. Faecal carriage of ESBL-producing Enterobacteriaceae was detected in samples from 19 of 61 food-borne outbreaks evaluated. All food-borne outbreaks were due to enteropathogens. The prevalence of carriers in these outbreaks ranged from 4.4% to 66.6%. CONCLUSIONS: This widespread occurrence of ESBL-producing Enterobacteriaceae suggests that the community could act as a reservoir and that food could contribute to the spread of these strains.

Agriculture↗

Comparative susceptibility of clinical isolates producing extended spectrum beta-lactamases to ceftibuten: effect of large inocula.

BACKGROUND: Infections caused by Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLs) are a growing clinical problem. However, there is wide variation in the level of resistance to third generation beta-lactams conferred by these enzymes. METHODS: We studied 33 Klebsiella pneumoniae and 4 Escherichia coli isolates producing ESBLs obtained from outbreaks in 14 different hospitals and a nursing home in the United States. Microdilution testing with standard (10(4-5) colony-forming units/ml) and large (10(6-7) colony-forming units/ml) inocula, was used to compare the minimum inhibitory concentrations (MICs) of ceftibuten, a novel oral oxyimino beta-lactam, with those of other third generation beta-lactams (cefotaxime, ceftazidime, aztreonam, cefixime, cefpodoxime and cefoxitin). RESULTS: Twenty-seven of the clinical isolates had well-characterized ESBLs of 10 different types, 7 of which produced TEM-1; 1 isolate also produced LXA-1. Two strains produced more than 1 ESBL. The remaining 10 strains produced 8 as yet uncharacterized types of ESBL. With large inocula 73% tested susceptible to ceftibuten, whereas 8 to 22% tested susceptible to the other third generation beta-lactam antibiotics. Ceftibuten MICs increased with higher inocula when tested against strains producing SHV-4 or SHV-5 and, to a lesser extent, strains producing multiple beta-lactamases. Only cefoxitin showed a smaller inoculum effect. CONCLUSION: Ceftibuten merits clinical evaluation in infections caused by bacteria that produce ESBLs.

Anti-Bacterial Agents↗

Beta-lactam antibiotic resistance in aerobic commensal fecal flora of newborns.

BACKGROUND: The purpose of the present paper was to prospectively determine the rate of beta-lactam antibiotic resistance in commensal fecal flora of newborns and the risk factors leading to this colonization. METHODS: One hundred and eighteen newborns in the neonatal intensive care unit (NICU) group (n = 38), the neonatal ward group (n = 36), and the control group (n = 44) were enrolled. Three or four stool samples were obtained from each infant, 15 days apart. Bacterial growth in Eozin Methylene Blue (EMB) agar + 10 microg ampicillin/mL was considered to be ampicillin-resistant bacteria, and antibiotic susceptibility and extended spectrum beta-lactamases (ESBL) production was investigated in those bacteria. RESULTS: Colonization with ampicillin-resistant commensal fecal flora microorganisms was determined in 75.2% of 367 stool samples. Klebsiella spp. and Escherichia coli were identified in 59% and 41% of the samples, respectively. The lowest rate of ampicillin-resistant bacterial colonization was determined in the NICU group. Microorganisms producing ESBL were identified in 33.7% of 367 stool samples. Fifty-one and 73 of ampicillin-resistant E. coli and Klebsiella spp. isolates were determined to produce ESBL, respectively. There was no difference with respect to colonization with ESBL-producing microorganisms between the three groups. When risk factors related to colonization with ESBL-producing microorganisms in stool samples were evaluated through the whole study period, very low birthweight, vaginal delivery, infant antibiotic usage, maternal antibiotic usage, male sex and premature rupture of membranes were determined as risk factors, while feeding with nasogastric tube was identified as a protective factor. When the risk factors related to colonization with ESBL-producing bacteria in stool samples after discharge from the hospital were evaluated, failure to feed breast milk was determined as the only risk factor. CONCLUSIONS: To decrease mortality and morbidity due to infection caused by resistant microorganisms colonized in the intestine flora of the infant, protection of normal non-pathogenic bacterial colonization is important. This can be provided by feeding neonates with breast milk, application of infection control measures efficiently, and limitation of antibiotic usage only to strict clinical indications.

Bacteria, Aerobic↗

Prevalence of extended-spectrum beta-lactamases in isolates of the Enterobacter cloacae complex from German hospitals.

In 2002, 119 isolates of the Enterobacter cloacae complex were collected randomly from 11 German laboratories nationwide. Antibiotic susceptibilities were tested by disk-diffusion tests according to CLSI guidelines, and MICs were determined using Etests. PCRs were performed to amplify all TEM and SHV, and most CTX-M and OXA beta-lactamase genes. PCR products were sequenced to identify the precise extended spectrum beta-lactamase (ESBL) types. Isoelectric focusing (IEF) and PM/PML Etests were used to confirm production of the respective ESBLs. According to susceptibility tests and CLSI criteria, 49 (40%) isolates were resistant to extended-spectrum cephalosporins. Seven (5.8%) isolates were positive in at least one of the PCR assays. Sequencing identified production of TEM-1 beta-lactamase genes by three (2.9%) isolates, and ESBL genes of the CTX-M and SHV beta-lactamase families by five (4.2%) isolates. IEF confirmed the production of beta-lactamases in the expected pI ranges of the respective ESBLs, and four of the five ESBL-producers were detected using the PM/PML Etest. All ESBL-producing isolates showed co-resistance to sulphonamides.

Anti-Bacterial Agents↗

Characterisation and molecular epidemiology of extended-spectrum beta-lactamase-producing Enterobacter cloacae isolated from a district teaching hospital in Taiwan.

Enterobacter cloacae (n = 110) isolates from a district hospital in Taiwan were screened for extended-spectrum beta-lactamases (ESBLs). In total, 17 ESBL-producers were identified, based on the combination-disk synergy test using cefotaxime and ceftazidime +/- clavulanic acid. Investigation of ESBL genes in 33 ceftazidime-resistant isolates revealed the SHV-12 gene in the same 17 ESBL-producers. In addition, one isolate also carried the CTX-M-3 gene, and two isolates also carried the CTX-M-9 gene. No major epidemic clone of ESBL-producers was identified by pulsed-field gel electrophoresis. Routine screening for the ESBL phenotype, focusing on ceftazidime-resistant E. cloacae, should be undertaken in this area.

Anti-Bacterial Agents↗