Frequency and Diversity of CTX-M Enzymes Among Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae Isolates from Caracas,Venezuela

Abstract

CTX-M-type extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae have been previously reported in Venezuela. We assessed the frequency and diversity of CTX-M enzymes among 97 ESBL-producing Enterobacteriaceae isolates as well as to establish the genetic relationship among CTX-M producers collected from six hospitals in Caracas. Polymerase chain reaction (PCR) assays identified the bla_CTX-M genes in 42 isolates (43.3%). The bla_CTX-M-1 group was the most common in Escherichia coli (91 %) and the bla_CTX-M-2 in Klebsiella pneumoniae (56.6%). Presence of bla_CTX-M-1, bla_CTX-M-2, bla_CTX-M-15, and bla_CTX-M-14 was revealed by sequencing analysis. The CTX-M producers were mainly isolated from urine samples (46%). Antimicrobial susceptibility tests showed that a high proportion of CTX-M-producing isolates was resistant to ciprofloxacin and trimethoprim-sulfamethoxazole. Analysis of enterobacterial repetitive intergenic consensus PCR and repetitive extragenic palindromic PCR profiles revealed several genetic clusters between isolates carrying the bla_CTX-M-1 group, while complete genotypic diversity among isolates carrying the bla_CTX-M-2 group was observed. This study documented that CTX-M has achieved a citywide distribution, with the CTX-M-1 group as the most frequent (66.7%). The CTX-M clusters detected suggest that patient–patient transmission may have played an important role in the widespread and high prevalence of the CTX-M-1 group. To our knowledge, this is the first report of the CTX-M-15 in Venezuela.