FALSE COMBINED DISCS TEST FOR DETECTION OF EXTENDED-SPECTRUM B-LACTAMASE (ESBL) IN ACINETOBACTER ISOLATES

Background and Aim:The combination disc test (CDT) was used for phenotypic detection of ESBL production. The CDT methods compare the zones of cephalosporin discs to those of the same cephalosporin plus clavulanate. β-Lactamases Responsible for Resistance to Expanded-Spectrum Cephalosporins in Acinetobacter baumannii isolates. Enzymes with marginal ESBL activity, those expressed weakly, and those produced alongside other enzymes are the hardest to detect.Methods:A total of 100 Acinetobacter baumannii isolates identified from patients at hospitals in Ahvaz, Iran, were studied. The CDT method was used for detection of ESBL production. The isolates were examined for the inhibition zone of ceftazidime (CAZ) 30 µg + clavulanic (CA) 10 µg adjacent to disk containing ceftazidime (CAZ) alone and cefotaxime (CTX) 30 µg + clavulanic (CA) 10 µg adjacent to disk containing cefotaxime alone on Muller Hinton agar. ESBL test was considered positive if the inhibition zone diameter in presence of clavulanic acid was ≥ 5 mm larger than that in the lack of it.Results:Among 100 Acinetobacter baumannii isolates, combined disc test showed that only one isolate (1%) has been considered as ESBL producing isolate.Conclusion:The results of this study showed that the majority of Acinetobacter baumannii isolates were resistant to the antibiotics ceftazidime and cefotaxime alone or in combination with clavulanic acid. So the CDT method outlined here will never be as precise as the best molecular analysis, but will detect most producers.

Keywords:

Acinetobacter baumannii , Combination disc test , ESBL