Extended-Spectrum Beta-Lactamases among <i>Enterobacter</i> Isolates Obtained in Tel Aviv, Israel

<jats:title>ABSTRACT</jats:title> <jats:p> The extended-spectrum beta-lactamase (ESBL)-producing phenotype is frequent among <jats:italic>Enterobacter</jats:italic> isolates at the Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. We examined the clonal relatedness and characterized the ESBLs of a collection of these strains. Clonal relatedness was determined by pulsed-field gel electrophoresis. Isoelectric focusing (IEF) and transconjugation experiments were performed. ESBL gene families were screened by colony hybridization and PCR for <jats:italic>bla</jats:italic> <jats:sub>TEM</jats:sub> , <jats:italic>bla</jats:italic> <jats:sub>SHV</jats:sub> , <jats:italic>bla</jats:italic> <jats:sub>CTX-M</jats:sub> , <jats:italic>bla</jats:italic> <jats:sub>IBC</jats:sub> , <jats:italic>bla</jats:italic> <jats:sub>PER</jats:sub> , <jats:italic>bla</jats:italic> <jats:sub>OXA</jats:sub> , <jats:italic>bla</jats:italic> <jats:sub>VEB</jats:sub> , and <jats:italic>bla</jats:italic> <jats:sub>SFO</jats:sub> ; and the PCR products were sequenced. The 17 <jats:italic>Enterobacter</jats:italic> isolates studied comprised 15 distinct genotypes. All isolates showed at least one IEF band (range, one to five bands) whose appearance was suppressed by addition of clavulanate; pIs ranged from 5.4 to ≥8.2. Colony hybridization identified at least one family of beta-lactamase genes in 11 isolates: 10 harbored <jats:italic>bla</jats:italic> <jats:sub>TEM</jats:sub> and 9 harbored <jats:italic>bla</jats:italic> <jats:sub>SHV</jats:sub> . PCR screening and sequence analysis of the PCR products for <jats:italic>bla</jats:italic> <jats:sub>TEM</jats:sub> , <jats:italic>bla</jats:italic> <jats:sub>SHV</jats:sub> , and <jats:italic>bla</jats:italic> <jats:sub>CTX-M</jats:sub> identified TEM-1 in 11 isolates, SHV-12 in 7 isolates, SHV-1 in 1 isolate, a CTX-M-2-like gene in 2 isolates, and CTX-M-26 in 1 isolate. In transconjugation experiments with four isolates harboring <jats:italic>bla</jats:italic> <jats:sub>TEM-1</jats:sub> and <jats:italic>bla</jats:italic> <jats:sub>SHV-12</jats:sub> , both genes were simultaneously transferred to the recipient strain <jats:italic>Escherichia coli</jats:italic> HB101. Plasmid mapping, PCR, and Southern analysis with TEM- and SHV-specific probes demonstrated that a single transferred plasmid carried both the TEM-1 and the SHV-12 genes. The widespread presence of ESBLs among <jats:italic>Enterobacter</jats:italic> isolates in Tel Aviv is likely due not to clonal spread but, rather, to plasmid-mediated transfer, at times simultaneously, of genes encoding several types of enzymes. The dominant ESBL identified was SHV-12. </jats:p>