First Outbreak of Multidrug-Resistant Klebsiella pneumoniae Producing both SHV-12-Type Extended-Spectrum beta-Lactamase and DHA-1-Type AmpC beta-Lactamase at a Korean Hospital

PURPOSE: Coexistence of different classes of beta-lactamases in a single bacterial isolate may pose diagnostic and therapeutic challenges. We investigated a spread of Klebsiella pneumoniae isolates co-producing an AmpC beta-lactamase and an extended-spectrum beta-lactamase (ESBL) in a university hospital. MATERIALS AND METHODS: Over a three-month period, a total of 11 K. pneumoniae isolates, which exhibited resistance to cefotaxime, aztreonam, and cefoxitin, were isolated. These isolates showed positive to ESBLs by double disk tests. Minimal inhibitory concentrations (MICs) were determined by broth microdilution testing. All isolates were examined by isoelectric focusing, PCR and sequence analysis to identify bla(SHV) and bla(DHA), and molecular typing by pulsed-field gel electrophoresis (PFGE). RESULTS: All 11 isolates were highly resistant (MIC, > or = 128microngram/ml) to ceftazidime, aztreonam, and cefoxitin, while they were susceptible (MIC, < or = 2microngram/ml) to imipenem. The bla(SHV-12) and bla(DHA-1) genes were detected by PCR and sequence analysis. PFGE revealed a similar pattern in 10 of the 11 strains tested. CONCLUSION: This is the first outbreak report of K. pneumoniae in Korea which co-produced SHV-12 and DHA-1 beta-lactamase, and we suggest a clonal spread of multidrug-resistant K. pneumoniae at a hospital.

Emergence of CTX-M-9 Extended-Spectrum beta-Lactamase-Producing Enterobacter cloacae Isolates / 대한임상미생물학회지

BACKGROUND: The aim of this study is to assess the prevalence and to investigate the molecular epidemiology of Ambler class A extended-spectrum beta-lactamase (ESBL)-producing Enterobacter cloacae isolates in a university hospital in Busan, Korea. METHODS: Non-duplicated clinical isolates of E.cloacae from patients admitted in Kosin University Gospel Hospital were collected during the period from January through September, 2003. ESBL-production was examined by the double-disk synergy test (DDST) and the transferability of cefotaxime-resistance by conjugation. MICs of beta-lactam antibiotics were determined by the agar dilution method and Ambler class A ESBL genes were searched by PCR amplification. Enterobacterial repetitive intergenic consensus (ERIC) PCR was performed to investigate epidemiological relationships among bla CTX-M-9 gene-carrying E.cloacae isolates. RESULTS: Antimicrobial resistance rates of E.cloacae isolates (n=148) to ceftazidime, cefotaxime, and aztreonam were 50.0%, 29.6%, and 48.0%, respectively. Among 50 E.cloacae isolates intermediate or resistant to more than one expanded-spectrum beta-lactam agent, 41 (27.7%) showed positive results in DDST; of these 41 isolates, 1 was found to carry bla TEM-52 gene, 16 carried bla SHV-12 gene, 4 bla CTX-M-9 gene, and 19 both bla SHV-12 and bla CTX-M-9 genes. The 23 E.cloacae isolates carrying bla CTX-M-9 gene showed 9 different profiles by ERIC PCR. CONCLUSION: ESBL-producing E.cloacae was not uncommon in a university hospital in Busan, Korea. The commonest types of ESBLs produced by E.cloacae isolates were SHV-12 and CTX-M-9. CTX-M-9 ESBL-producing E.cloacae isolates showed diverse ERIC-PCR profiles, indicating that they were not originated from a common source.

Characterization of Extended-Spectrum-beta-Lactamase Genes from Clinical Isolates of Enterobacter species / 대한임상미생물학회지

BACKGROUND: Among Enterobacter spp. isolates from clinical specimens in Korea, the incidence of resistance to expanded-spectrum cephalosporins is becoming an ever-increasing problem. This study was designed to determine the prevalence of expanded-spectrum cephalosporins-resistant Enterobacter spp. isolates from patients in a tertiary care hospital in Busan, Korea, and to characterize the mechanism of resistance. MATERIALS AND METHODS: Nonduplicated clinical isolates of Enterobacter spp. were collected during the period of 1999-2000 in Kosin Medical Center, Busan, Korea. Antimicrobial susceptibilities were tested by disk diffusion method. Cefotaxime-resistant or intermediate isolates were examined for extended-spectrum beta-lactamase (ESBL)-production by double disk synergy (DDS) test. Minimal inhibitory concentrations were determined by agar dilution method. For detection of blaTEM and blaSHV genes, polymerase chain reactions (PCRs) were performed, and the DNA sequences of blaTEM and blaSHV genes were determined by using dideoxy-chain termination method. RESULTS: From 1999 to 2000, a total of 306 Enterobacter spp. strains were isolated from patients in Kosin Medical Center. Forty one percents of Enterobacter spp. isolates were susceptible to cefotaxime. Among 90 isolates resistant or intermediate to cefotaxime, 26 isolates (29%) showed positive results in double disk synergy test. Among DDS-positive- isolates, 22 isolates contained both of blaTEM and blaSHV genes, while one isolate only contained blaTEM gene and two isolates only contained blaSHV gene. Among 64 DDS-negative isolates, 47 isolates contained blaTEM genes, and 12 isolates also contained blaSHV genes. Nucleotide sequence analysis of PCR products from 10 DDS-positive and 6 DDS-negative isolates, which contained both of blaTEM and blaSHV genes, revealed that blaTEM-1b and blaSHV-12 genes were the dominant types of beta-lactamase gene. CONCLUSION: Expanded-spectrum cephalosporins-resistant Enterobacter spp. were wide spread in Kosin Medical Center, Busan, Korea. Some of the resistant isolates acquired resistance by production of ESBLs, and blaSHV-12 gene was the most frequent ESBL gene in cefotaxime-resistant Enterobacter spp.

The characteristics of extended-spectrum beta-lactamases in Korean isolates of Enterobacteriaceae

Extended-spectrum beta-lactamases (ESBLs) in gram-negative organisms have been implicated as the enzymes responsible for resistance to oxyimino-cephalosporins. The incidence of ESBL- producers in Korean isolates of Escherichia coli and Klebsiella pneumoniae were in the range of 4.8 7.5% and 22.5 22.8%, respectively. The ESBL-producing isolates revealed variable levels of resistance to cefotaxime, ceftazidime and aztreonam. They also showed the elevated MIC values of non-beta-lactam antibiotics. SHV-12 and SHV-2a were the enzymes most frequently found in K. pneumoniae strains, but TEM-52 was the most prevalent in E. coli isolates. About 15% of ESBL-producing isolates of Enterobacteriaceae produced CMY-1 enzyme, which conferred resistance to cephamycins such as cefoxitin as well as oxyimino-cephalosporins. Thus, the most common types of ESBLs in Korea are TEM-52, SHV-12, SHV-2a, and CMY-1.