MOLECULAR EPIDEMIOLOGY OF EXTENDED-SPECTRUM BETA-LACTAMASE-PRODUCING KLEBSIELLA-PNEUMONIAE ISOLATES IN A DISTRICT HOSPITAL IN TAIWAN

Thirty-one of 104 clinical isolates of Klebsiella pneumoniae collected over a period of 8 months were found to be putative extended-spectrum beta-lactamase (ESBL) producers. Isoelectric focusing and an iodine o verlay agar method were used for preliminary identification of the ESB Ls, They were further identified by DNA sequencing, Seventy-one percen t of the isolates were found to produce SHV-5. The variation in the ES BL patterns of these isolates was slight, with only five patterns bein g identified. The strains were typed by pulsed-field gel electrophores is (PFGE), and 16 different genotypes were identified, When the PFGE p atterns were analyzed by the algorithmic clustering method called the unweighted-pair group method using arithmetic averages, five clusters were found, However, significant genetic variations were found among 1 1 isolates and between each cluster. A plasmid of 36 kb was found in a ll clinical isolates :Ind in the transconjugants. Our results indicate that the increase in the number of ESBL-producing K. pneumoniae isola tes in this hospital is due mainly to the dissemination of a resistanc e plasmid rather than to the clonal spread of a few epidemic strains.