Sung-Yong Seol

Occurrence of CTX-M-3, CTX-M-15, CTX-M-14, and CTX-M-9 Extended-Spectrum β-Lactamases in Enterobacteriaceae Clinical Isolates in Korea

ABSTRACT Among 603 isolates of Enterobacteriaceae collected between June and November 2003 from three university hospitals within Korea, blaCTX-M-3, blaCTX-M-15, blaCTX-M-14, and blaCTX-M-9 were detected in 41 isolates of species from five different genera of Enterobacteriaceae, Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Enterobacter spp., and Serratia marcescens.

Diversity of Tn1546-Like Elements in Vancomycin-Resistant Enterococci Isolated from Humans and Poultry in Korea

ABSTRACT To investigate the possible spread of vancomycin resistance among enterococci through horizontal gene transfer between two sources of vancomycin-resistant enterococci (VRE) isolated from farm animals and humans in Korea, molecular characterization of VRE isolated from poultry (20 isolates) and humans (35 isolates) was performed by PCR-restriction fragment length polymorphism typing of the vanA gene cluster (Tn1546). PCR mapping of Tn1546 finally distinguished seven different transposon types (types A to G). Type A was observed only in the poultry isolates, while the other six types were present only in the human isolates. An insertion sequence and deleted sequence were detected in most of the human isolates in the orf2-vanR and vanX-vanY regions in the Tn1546-like element, but not in the poultry isolates. Tn1546-like elements were found in conjugal plasmids of most human VRE, whereas they were detected in the chromosomes of all poultry VRE. Accordingly, no evidence was found of any recent transmission of vancomycin resistance genes between poultry and humans in Korea.

Involvement of curli fimbriae in the biofilm formation of Enterobacter cloacae

In this study, we examined the biofilm forming ability, the mRNA expression of curli genes and the morphologies of curli fimbriae and biofilms in clinical isolates of Enterobacter cloacae. The csgBA operon was found in 11 (78.6%) of the 14 isolates. The ability of E. cloacae isolates to form biofilms was significantly correlated with the mRNA expression level of the csgA and csgD genes. The curli protein fimbriae appeared as tangled fibers and the curli-proficient strain formed mature biofilms. Our data suggest that the expression of the curli fimbriae play an important role in biofilm formation in E. cloacae.