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Diversity of Genetic Lineages Among CTX-M-15 and CTX-M-14 Producing Escherichia coli Strains in a Tunisian Hospital

Diversity of Genetic Lineages Among CTX-M-15 and CTX-M-14 Producing Escherichia coli Strains in a Tunisian Hospital,10.1007/s00284-011-9930-4,Current

Diversity of Genetic Lineages Among CTX-M-15 and CTX-M-14 Producing Escherichia coli Strains in a Tunisian Hospital  
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Fourteen broad-spectrum-cephalosporin-resistant Escherichia coli isolates were recovered between June and December 2007 in a Tunisian hospital. Genes encoding extended-spectrum-beta-lactamases (ESBL) and other resistance genes were characterized by PCR and sequencing. The following ESBL genes were identified: bla CTX-M-15 (12 isolates), bla CTX-M-14a (one isolate), and bla CTX-M-14b (one isolate). The bla OXA-1 gene was detected in 13 bla CTX-M-producing strains and a bla TEM-1 gene in 6 of them. The ISEcp1 sequence was found upstream of bla CTX-M genes in 8 of 14 strains, and orf477 or IS903 downstream of this gene in 13 strains. Nine of the strains carried class 1 integrons and five different gene cassette arrangements were detected, dfrA17–aadA5 being the most common. One of the strains (bla CTX-M-14a-positive) harbored three class 1 integrons, and one of them was non-previously described containing as gene cassettes new variants of aac(6′)-Ib and cmlA1 genes and it was linked to the bla CTX-M-14a gene flanked by a truncated ISEcp1 sequence (included in GenBank with accession number JF701188). CTX-M-15-producing strains were ascribed to phylogroup B2 (six isolates) and D (six isolates). Multilocus-sequence-typing revealed ten different sequence-types (STs) among ESBL-positive E. coli strains with prevalence of ST405 (four strains of phylogroup D) and ST131 types (two strains of phylogroup B2 and serogroup O25b). A high clonal diversity was also observed among studied strains by pulsed-field-gel-electrophoresis (11 unrelated profiles). CTX-M-15 is an emergent mechanism of resistance in the studied hospital and the world-disseminated 0:25b-ST131-B2 and ST405-D clones have been identified among CTX-M-15-producing isolates.
Journal: Current Microbiology - CURR MICROBIOL , vol. 62, no. 6, pp. 1794-1801, 2011
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