patt ern of resis tance to beta-lactams in e.coli isolated from urinary tract infections in iran

a total of 385 urine specimens from suspected urinary tract infections were subjected to bacteriological analysis and susceptibility testing at a major university hospital laboratory in tehran. a battery of eight beta-iactam antibiotics, commonly prescribed in iran, and three third-generation cephalosporins (ceftazidime, ceftriaxone and ceftizoxime) that are usually reserved for limited use in the hospital setting were tested against e.coli urine isolates, using kirby-bauer disk diffusion method. e. coli was the most common isolate from both the inpatient (37.8%) and outpatient (30.5%) populations. the susceptibility testing revealed a high degree of resistance to oxacillin, ampicillin, amoxyciliin, carbenicillin and cephradine. furthermore, a marked difference in the sensitivity/resistance ratio between the inpatient and outpatient populations was observed. the e.coli isolates exhibited the highest rate of resistance to oxacillin, ranging from 49.4% in the outpatients to 81.6% in the inpatients. the frequency of the isolate resistance to first-generation cephalosporins was less widespread. despite the absence of resistance to third-generation cephalosporins among the outpatient isolates, a significant resistance to ceftazidime (9.6%) and ceftriaxone (8.8%) was observed among the outpatient bacterial isolates. the susceptibility testing of the e.coli isolates to a combination of amoxycillin and clavulanic acid revealed 6.9% resistance among outpatient and 12.5% among inpatient isolates. these results are particularly significant in that this study was performed immediately before the introduction of co-amoxyclav to the iranian drug market and can be served as a basis for monitoring the spread of resistance to this drug in iran.