Abstract
Extended-spectrum β-lactamases (ESBL), including the most wide spread CTX-M-15 enzyme, are major antibiotic resistant mechanisms of Enterobacteriaceae. Emergence of this plasmid-mediated enzyme poses a global threat particularly in Asian countries struggling with war. In this study, we investigated CTX-M-15 in clinical isolates of Enterobacteriaceae from healthy Afghan refugees in Iran and analyzed the association between CTX-M-15 and pattern of antibiotic resistance as well as the location of this gene among the isolates. No correlation was found between clonal groups and antimicrobial resistance patterns of the Enterobacteriaceae species. The frequency of cephalosporin resistance was significantly higher among CTX-M-15-producing isolates compared with other ESBL-producing isolates (P<0.05) with 70 and 30 resistant isolates, respectively; however the association between CTX-M-15 and quinolone resistance was not significant as 4 isolates were quinolone resistant in both CTX-M-15-positive and other ESBL-producing group of isolates. All 20 tetracycline resistant isolates were CTX-M-15-positive (P<0.05) and resistance to aminoglycosides among CTX-M-15-positive isolates were considerably higher (n=22) than other ESBL-producing isolates (n=7) (P<0.05). Resistance to meropenem, imipenem, aztreonam, piperacillin and ampicillin was not significantly associated with CTX-M-15-production. Plasmid analysis revealed that the CTX-M-15 gene is located on a large plasmid ranged between 90 and 100 kb. This is amongst the premier report describing the association between CTX-M-15-production and different antibiotic resistance patterns in Enterobacteriaceae isolates collected from healthy individuals. The significant association between cephalosporin, aminoglycoside and tetracycline resistance and CTX-M-15-production emphasizes a need for introducing new antibiotic choices for the treatment of infections caused by Enterobacteriaceae. Key words: Extended-spectrum β-lactamases (ESBL), CTX-M-15, Enterobacteriaceae, antibiotic resistance, plasmid.
Highlights
Extended-spectrum β-lactamases (ESBLs) represent a major threat among Enterobacteriaceae species (Jemima and Verghese, 2008; Leflon-Guibout et al, 2004)
Dominant emergence of CTX-M types has been observed in Asia (Sidjabat and Paterson, 2015; Eckert et al, 2004; Robicsek et al, 2006; Stiles et al, 1981); recently high prevalence of CTX-M-15 was reported from South India as an Asian country neighboring Middle East countries (Ensor et al, 2006)
Enterobacteriaceae isolates collected from Afghan refugees in Iran according to the fact that CTX-M-15 was present in about one third of the 100 ESBL-producing isolates confirmed by DNA sequencing
Summary
Extended-spectrum β-lactamases (ESBLs) represent a major threat among Enterobacteriaceae species (Jemima and Verghese, 2008; Leflon-Guibout et al, 2004). ESBLs are capable of hydrolyzing β-lactam antibiotics, and are. Plasmid-mediated β-lactamases that are transferable among different bacteria (Nemec et al., 2004). The production of ESBLs in Enterobacteriaceae confers resistance to the most of cephalosporins that have been commonly used to treat gram negative bacterial infections (Poirel et al, 2002). Combination therapy with β-lactams and aminoglycosides is one of the alternative choices for the treatment of systemic infections caused by Enterobacteriaceae (Livermore, 1995)
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