Introduction and objective: Escherichia coli is a major cause of urinary tract and other opportunistic infections. Emergence of antibacterial resistance and production of extended spectrum β-lactamases (ESBLs) are responsible for the frequently observed empirical therapy failures. ESBLs producing bacteria and AmpC are serious threat in treating bacterial infections. Existence of various mechanisms which create resistance to antibiotics accounts for treatment failure in infections with these bacteria. The aim of this study was to determine the presence and the prevalence of blaCTX-M, blaSHV, blaTEM and blaAmpC β-lactamases genes in clinical isolates of E. coli in Kerman.
Materials and methods: Agar dilution method was used to determine the minimum inhibitory concentration of cefotaxime, ceftazidime and ceftizoxime in138 E. coli isolates. Resistance to imipenem, cefepime and cefoxitin was determined by disk diffusion method. Phenotypes of ESBLs and AmpC were also determined by combined disk method and non β-lactam inhibitor based method (boronic acid) respectively. PCR was used to determine blaCTX-M, blaSHV, blaTEM and blaAmpC genes in the ESBLs positive isolates.
Results: From 138 E. coli isolates 68.1% produced ESBLs by phenotypic method. Incidence rate of blaTEM, blaSHV and blaCTX-M among ESBL producing isolates were 63.8%, 51% and 23.4%, respectively. Presence of blaTEM, blaSHV and blaCTX-M genes at the sametime was detected in10.6% of isolates. Simultaneous production of AmpC and ESBLs was observed in 6.5 % of isolates. blaAmpC gene by PCR was seen in three isolates.
Conclusion: TEM and SHV β-lactamases are the dominant β-lactamases in this area. Simultaneous production of various β-lactamases in these isolates reflects the increased ability of these isolates against antibacterial agents and; therefore, this can cause serious problems in future in the treatment of infections especially nosocomial infections of such isolates.
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