characterization of β-lactamases from urinary isolates of escherichia coli in tehran

Authors

سید مهدی حسینی مزینانی

seyed mehdi hosseini-mazinani فرشته افتخار

fereshteh eftekhar مهناز میلانی

mahnaz milani سهیلا قندیلی

soheila ghandili

abstract

knowledge of antimicrobial resistance patterns in e. coli, the predominant pathogen associated with urinary tract infections (uti) is important as a guide in selecting empirical antimicrobial therapy. methods: to describe the antimicrobial susceptibility of e. coli associated with uti in a major university hospital in tehran (iran), seventy-six clinical isolates of e. coli were studied for susceptibility to b-lactam antibiotics by the disc diffusion method and minimal inhibitory concentrations determination. results: all isolates were resistant to ampicillin, amoxicillin and oxacillin. resistance to the other tested antibiotics was shown to be 93.4% to cefradine, 76.3% to carbenicillin, 47.3% to cefazoline, 50% to cefalexin and 32.8% to cephalothin while 1.3% expressed resistance to cefoxitime, and 2.6% were resistant to ceftizoxime and ceftriaxone. two isolates (2.4%) harbored extended spectrum b-lactamases (esbl) shown by the double disc diffusion method. substrate hydrolysis by ultra violet spectroscopy showed that 87.4% harbored penicillinases, 9% produced cephlosporinases and 3.6% degraded both substrates. clavulanic acid inhibited enzyme activity in 82.9%, of which 78.95% was penicillinases (group iia) and 3.95% was cephalosporinases (group iib) of the bush classification system. the rest of the isolates (6.58 %) were placed in group iv b-lactamases. no group iii b-lactamase was found, as edta inhibited none of the enzymes. dna amplification by polymerase chain reaction using specific primers for ampc, tem and shv type b-lactamases for all of the isolates showed that 47 organisms (60%) carried the tem gene and 18 isolates (24%) harbored blatem and ampc genes. about 26% of the organisms harbored shv type enzymes. conclusion: these results indicate that e. coli can posses a variety of b-lactamases that are responsible for β-lactam resistance.

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Journal title:
iranian biomedical journal

جلد ۱۱، شماره ۲، صفحات ۹۵-۹۹

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