BACKGROUND: The aim of this study was to determine the yearly prevalence and genotype distribution of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae collected over a 3-yr period in Gwangju, Korea. METHODS: Clinical isolates of E. coli and K. pneumoniae collected at Chosun University Hospital from September 15, 2005 to September 14, 2008 were evaluated. Antimicrobial susceptibility testing was performed using the Vitek II system (bioMerieux, USA) and agar dilution methods. Screening for ESBL and AmpC beta-lactamase genes was performed using PCR amplification of plasmid DNA followed by direct sequencing of the PCR products. RESULTS: The percentage of ESBL-producing isolates was 12.6% (196/1,550) for E. coli and 26.2% (294/1,121) for K. pneumoniae. The ESBL gene sequencing results showed that the most prevalent ESBL types were CTX-M (93.5%) and SHV (12.9%) in E. coli, and SHV (73.2%) and CTX-M (46.3%) in K. pneumoniae. The most common ESBL in E. coli was CTX-M-15-like, followed by CTX-M-14-like, SHV-2a-like, and SHV-12-like. The most prevalent ESBL type in K. pneumoniae was SHV-12, followed by CTX-M-14-like and CTX-M-15-like. Fifty-one percent (21/41) of ESBL-producing K. pneumoniae with ESBL types verified by sequencing also had DHA-1-like AmpC beta-lactamases. However, none of the ESBL-producing E. coli was positive in the AmpC beta-lactamase PCR analysis. CONCLUSIONS: In this study, the most common types of class A ESBLs identified were CTX-M-15-like in E. coli and SHV-12-like in K. pneumoniae.
Bacterial Proteins/*genetics ; Drug Resistance, Bacterial/genetics ; Escherichia coli/*genetics/isolation & purification ; Gene Frequency ; Genotype ; Hospitals, University ; Humans ; Klebsiella pneumoniae/*genetics/isolation & purification ; Microbial Sensitivity Tests ; Republic of Korea ; Sequence Analysis, DNA ; beta-Lactamases/*genetics

BACKGROUND: The incidence of infections with imipenem- resistant Acinetobacter baumannii (IRAB) and Pseudomonas aeruginosa (IRPA) is increasing worldwide, and recent molecular studies indicate that the prevalence of carbapenemases is increasing in various parts of the world. However, few long-term longitudinal studies have assessed the prevalence of IRAB- and IRPA-derived carbapenemases and integrases in a hospital setting in Korea. METHODS: The carbapenemase genes (blaOXA-23, blaOXA-24, blaOXA-58, blaIMP-1, blaVIM-2, blaSIM-1, blaSPM-1) and integrase genes (intI1, intI2, intI3) produced by 46 IRAB strains and 51 IRPA strains collected at Chosun University Hospital between 2003 and 2006 were determined by PCR. RESULTS: The IRAB strains produced class 1 integrases more often than did the IRPA strains. However, the incidence increased steadily in both strains, reaching 100% in 2006. Carbapenemases of blaIMP-1 and blaVIM-2 types were found in 57% and 64% of the IRAB strains, respectively, in 2003. However, only one strain with blaVIM-2 was found in 2004 and another one with blaIMP-1 in 2005. The prevalence of carbapenemases was very low in the IRPA strains, just one strain with blaVIM-2 in 2005 and another one with blaoxa-23 in 2006. No other types of carbapenemase genes were detected in both strains. Rep-PCR of IRAB strains in 2003 showed different patterns. CONCLUSION: The incidence of carbapenemase varied by year but was generally low, except in 2003. The prevalence of class 1 integrases was consistently high and increased every year. The reason for the high prevalence of carbapenemases in 2003 is still unknown, but we assumed that it was not from the spread of a clone containing either blaIMP-1 or blaVIM-2 because the strains exhibited different rep-PCR patterns.
Acinetobacter baumannii* ; Acinetobacter* ; Clone Cells ; Imipenem ; Incidence ; Integrases* ; Korea ; Polymerase Chain Reaction ; Prevalence* ; Pseudomonas aeruginosa* ; Pseudomonas*