First Description of Klebsiella pneumoniae Harboring CTX-M β-Lactamases (CTX-M-14 and CTX-M-3) in Taiwan

A new series of extended-spectrum -lactamase (ESBL) enzymes, cefotaximases (CTX-M), resulting in higher MICs of cefotaxime and ceftriaxone than of ceftazidime, has been discovered in several members of the family Enterobacteriaceae and in various countries (10). A previous study in southern Taiwan (11) showed that CTX-M-3 was the predominant ESBL among clinical isolates of Escherichia coli. We have also discovered that 87 of 211 (41%) ESBL-producing Klebsiella pneumoniae isolates from Taiwan expressed a CTX-M phenotype (ceftriaxone MIC, 16 g/ml; ceftazidime MIC, 8 g/ml [unpublished data]). CTX-M enzymes have not been previously identified in klebsiellae from Taiwan. In the present study, we determined the CTX-M identification by nucleotide sequencing, the distribution of MICs of various broad-spectrum -lactams, and the molecular epidemiology of these CTX-M-producing strains.