engleski

ANTIB IOTIC SUSCEPTIBILITY AND BETA-LACTAMASE PRODUCTION OF GRAM-NEGATIVE BACTERIA FROM THE SWIMING POOLS IN SLOVENIA

β-lactamases are enzymes which hydrolyze β- lactam antibiotics. The first β-lactamases were reported before the β-lactams were introduced into the clinical practice, mostly from environmental bacteria. Therefore, it is likely to expect that there is a pool of β-lactamase encoding genes in the environment. Gram- negative bacteria are ubiquitous in nature and are widely distributed in soil and water. Extended-spectrum β-lactamases (ESBLs) hydrolyze penicillins, cephalosporins of the 1st, 2nd, 3rd and fourth generation and monobactams. Carbapenemases hydrolyze carbapenems and belong to class A, B (metallo- β-lactamases or MBLs) and D (carbapenem- hydrolyzing oxacillinases). The aim of the study was to analyze antibiotic susceptibility and β-lactamase production of Gram-negative isolates collected from the swiming pools in Slovenia. The collection included 10 Pseudomonas aeruginosa strains, 1 Pseudomonas putida, one Serratia marcescens, 1 Citrobacter farmeri, one Citrobacter brackii, one Citrobacter koseri, one Klebsiella oxytoca, one Escherichia coli, three Acinetobacter baumannii and one Cryseobacterium spp. In total 21 Gram-negative strains were collected from various swiming pools in Slovenia. The antimicrobial susceptibilty was determined by disk-diffusion and broth microdilution method according to CLSI. Production of ESBLs was detected by double-disk synergy test (DDST) and combined disk test with clavulanic acid. MBLs were detected by combined disk test with EDTA. Resistance genes including those encoding ESBLs (blaTEM, blaSHV, blaCTX-M), carbapenemases (blaKPC, blaVIM, blaIMP, blaNDM) and fluoroquinolone resistance (qnr A, B, and S) were determined by PCR. A. baumannii and P. aeruginosa strains showed resistance to amoxycillin alone and combined with clavulanate, and first and second generation of cephalospoirns. DDST was positive in eight strains. The Enterobactericeae were resistant only to ampicillin and two to cefuroxime as well. CTX-M β-lactamases belonging to 8 and 25 group were identified in five Citrobacter spp, E. coli and S. marcescens strains. VIM-1 β-lactamase was identified in one Citrobacter brackii strain. Unexpectedly high number of ESBL positive enterobacteriaceae was found in spite of the evident susceptibility to expanded-spectrum cephalosporins. We can assume that the expression of blaESBL genes is weak in environmental bacteria due to the lack of selection pressure. The study demonstrated spread of Gram-negative isolates carrying resistance genes into th environment.

antibiotic susceptibility, Acinetobacter baumannii, Pseudomonas aeruginosa, swimming pool, resistance,

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