engleski

The frequency of isolation of ESBL producing strains of Enterobacter cloacae from the outpatient's urine samples

During the year 2003. in the Laboratory for Urogenital Infections of the Public Health Institute in Rijeka we have analyzed 20 963 urine samples obtained from outpatients from the region. A total of 6 524 isolates were further analyzed as the probable cause of infection. 4 399 isolates (67, 43%) were identified as the members of the family Enterobacteriaceae with Escherichia coli as the most prevalent isolate. Enterobacter cloacae was isolated from 400 urine samples. When antibiotic susceptibility was tested we noticed that a significant proportion of Enterobacter cloacae isolates (43 or 10, 75%) was multiply resistant against almost all antibiotics tested (beta-lactams, aminoglycosides, fluoroquinolones, trimethoprim-sulfamethoxazole) except imipenem. Therefore, we further analyzed these strains for the production of beta-lactamases to get the insight to the possible presence of extended spectrum beta-lactamases (ESBL) among them. We have designed a simple biological assay for the determination of beta-lactam substrate degradation by beta-lactamases produced. We tested seven different cephalosporins belonging to the first (1), second (1), third (4) and fourth (1) generation. One of the strains tested exhibited no beta-lactamase activity. From the rest of 42 strains two strains (4, 76%) degraded all cephalosporins tested. Eight strains (19, 05%) degraded six and nine (21, 43%) of them degraded five of the cephalosporin substrates. The most resistant cephalosporin against beta-lactamase activity was ceftazidime. Only four of the strains (9, 52%) successfully degrade it while the degradation rate for all other antibiotics was between 42, 86% for cefepime and 97, 62% for cefazolin. Interestingly, cefoperazone, a member of the third generation was degraded by 40 of 42 strains tested (95, 24%).

ESBL; resistance; Enterobacter cloacae

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