STUDY OF BETA-LACTAM RESISTANCE IN CEFTAZIDIME-RESISTANT CLINICAL ISOLATES OF ENTEROBACTERIACEAE

Mechanisms and transferability of beta-lactam resistance in 50 ceftazi dime resistant strains of Enterobacteriaceae was studied. These strain s were selected from 1991 E. coli, 1035 Enterobacter spp., 168 Citroba cter spp. and 1371 Klebsiella spp., isolated from patients hospitalize d in ICUs and in the pediatric and urology departments of six hospital s in Bratislava during the years 1994-1996. The selected strains expre ssed the resistance not only to ceftazidime (50/50) but also to ampici llin (50/50), ceftriaxone (50/50), cefotaxime (49/50) and cefoxitin (4 5/50). The mechanism of resistance in all 50 strains was the productio n of beta-lactamases by conjugation, using either ceftazidime or cefot axime for the selection of transconjugants and by isolation of R-plasm ids ranging from to 55-87 kb from donor strains and from transconjugan ts. A total of 21 isolates possessed chromosomally encoded resistance and 25 clinical isolates and their transconjugants expressed ESBL sens itive to clavulanate. Selected E. coli and Klebsiella pneumoniae isola tes expressed the presence of TEM and SHV enzymes determined by isoele ctric focusing. The possible trends in the development of antimicrobia l resistance in Slovakia in the future are indicated. (C) 1998 Elsevie r Science B.V./International Society of Chemotherapy. All rights reser ved.