BACKGROUND: The emergence of carbapenem-resistant Klebsiella pneumoniae poses a serious problem to antibiotic management. We investigated the beta-lactamases in a group of carbapenem-resistant K. pneumoniae clinical isolates from Turkey. METHODS: Thirty-seven strains of K. pneumoniae isolated from various clinical specimens were analyzed by antimicrobial susceptibility testing, PCR for the detection of beta-lactamase genes, DNA sequencing, and repetitive extragenic palindronic (REP)-PCR analysis. RESULTS: All 37 isolates were resistant to ampicillin, ampicillin/sulbactam, piperacillin, piperacillin/tazobactam, ceftazidime, cefoperazone/sulbactam, cefepime, imipenem, and meropenem. The lowest resistance rates were observed for colistin (2.7 ), tigecycline (11 ), and amikacin (19 ). According to PCR and sequencing results, 98 (36/37) of strains carried at least one carbapenemase gene, with 32 (86 ) carrying OXA-48 and 7 (19 ) carrying NDM-1. No other carbapenemase genes were identified. All strains carried a CTX-M-2-like beta-lactamase, and some carried SHV- (97 ), TEM- (9 ), and CTX-M-1-like (62 ) beta-lactamases. Sequence analysis of bla(TEM) genes identified a bla(TEM-166) with an amino acid change at position 53 (Arg53Gly) from bla(TEM-1b), the first report of a mutation in this region. REP-PCR analysis revealed that there were seven different clonal groups, and temporo-spatial links were identified within these groups. CONCLUSIONS: Combinations of beta-lactamases were found in all strains, with the most common being OXA-48, SHV, TEM, and CTX-M-type (76 of strains). We have reported, for the first time, a high prevalence of the NDM-1 (19 ) carbapenemase in carbapenem-resistant K. pneumoniae from Turkey. These enzymes often co-exist with other beta-lactamases, such as TEM, SHV, and CTX-M beta-lactamases.