Characterization of Two New CTX-M-25-Group Extended-Spectrum β-Lactamase Variants Identified in Escherichia coli Isolates from Israel

Abstract

ObjectivesWe characterized two new CTX-M-type extended-spectrum β-lactamase (ESBL) variants in Escherichia coli isolates from stool samples of two elderly patients admitted at the Tel Aviv Sourasky Medical Center, Israel. Both patients underwent treatment with cephalosporins prior to isolation of the E. coli strains.MethodsESBLs were detected by the double-disk synergy test and PCR-sequencing of β-lactamase genes. The bla CTX-M genes were cloned into the pCR-BluntII-TOPO vector in E. coli TOP10. The role of amino-acid substitutions V77A and D240G was analyzed by site-directed mutagenesis of the bla CTX-M-94 and bla CTX-M-100 genes and comparative characterization of the resulting E. coli recombinants. MICs of β-lactams were determined by Etest. Plasmid profiling, mating experiments, replicon typing and sequencing of bla CTX-M flanking regions were performed to identify the genetic background of the new CTX-M variants.ResultsThe novel CTX-M β-lactamases, CTX-M-94 and -100, belonged to the CTX-M-25-group. Both variants differed from CTX-M-25 by the substitution V77A, and from CTX-M-39 by D240G. CTX-M-94 differed from all CTX-M-25-group enzymes by the substitution F119L. Glycine-240 was associated with reduced susceptibility to ceftazidime and leucine-119 with increased resistance to ceftriaxone. bla CTX-M-94 and bla CTX-M-100 were located within ISEcp1 transposition units inserted into ∼93 kb non-conjugative IncFI and ∼130 kb conjugative IncA/C plasmids, respectively. The plasmids carried also different class 1 integrons.ConclusionsThis is the first report on CTX-M-94 and -100 ESBLs, novel members of the CTX-M-25-group.

blaCTX-M-152, a Novel Variant of CTX-M-group-25, Identified in a Study Performed on the Prevalence of Multidrug Resistance among Natural Inhabitants of River Yamuna, India

“…Unlike CTX-M-1, CTX-M-25 like β-lactamases has been observed less frequently worldwide. Similar to our study, two other novel variants, CTX-M-94 and CTX-M-100 belonging to group-25 were reported in Israel (Vervoort et al, 2012 ). The bla CTX-M-152 variant identified in K. georgiana isolate was found localized on chromosomal DNA while those identified in E. coli isolates screened from samples collected from downstream region of river Yamuna were found localized on plasmid.…”

Antibiotic-resistant <i>Escherichia coli</i> isolated from urban rodents in Hanoi, Vietnam

“…The bla CTX-M-8 group was found in E. coli isolated from chicken meats in Brazil [36], humans in the United States [30] and gulls in Spain [52]. The bla CTX-M-25 group was reported from clinical samples in Israel [56] and broiler chickens in Japan [61]. In this study, we found the bla CTX-M-1 group in three ESBL-producing E. coli isolated from rodent feces.…”

The Occurrence ofblaCTX-M,blaSHV, andblaTEMGenes in Extended-Spectrumβ-Lactamase-Positive Strains ofKlebsiella pneumoniae,Escherichia coli, andProteus mirabilisin Poland

“…Furthermore, in the present study CTX-M-91 and CTX-M-89 among P. mirabilis were identified. These genes exhibit genetic similarity with CTX-M-25 encode enzymes belonging to the sub-CTX-M-25 with extended-spectrum -lactamase activity [15,16]. Genes CTX-M-91 and CTX-M-89 are uncommon but their occurrence in P. mirabilis and Enterobacter cloacae was reported [17,18].…”