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.