engleski

Prevalence and molecular characterisation of extended-spectrum beta-lactamases amongst Escherichia coli isolates from coastal marine environment

The emergence of antibiotic resistant bacteria in the marine environment is a growing concern, but data about the abundance and diversity of antibiotic resistant bacteria and resistance genes encoding extended-spectrum beta- lactamases (ESBLs) in coastal marine waters is limited. This study was performed to investigate the patterns of antibiotic resistance and molecular diversity genes encoding ESBLs among antibiotic resistant Escherichia coli strains. Total of 258 E. coli isolates were recovered from 34 samples collected between February and July 2009 from the three coastal sites in the Kaštela Bay (Adriatic Sea, Croatia). The susceptibility pattern of the isolates was determinated by disk diffusion method and double-disk synergy tests for the production of ESBLs. The genes responsible for the ESBL phenotype (blaTEM, blaSHV, blaCTX-M) were screened by individual PCR. The ability to transfer antimicrobial resistance determinants was tested by broth mating experiments. The isolates from the Kaštela Bay showed high resistance to ampicillin (87%), tetracycline (56%), trimethoprim- sulfamethoxazole (39%), ticarcillin (33%), and gentamicin (31%). Resistance was also observed to nalidixic acid, cefotaxime, ciprofloxacin and ceftazidime. Approximately 54% of the E. coli isolates showed multidrug resistance (MDR) phenotypes. The MDR index ranged from 0.38 to 0.45 in the samples collected from the three coastal sites. Sequencing of selected amplicons revealed the presence of ESBL genes have found in 32/258 (12%) of E. coli isolates. Most of the ESBL producing isolates carried the CTX-M genotype, in which the CTX-M-1 group genes were dominant 78.12% (25/32).Interestingly, 25 CTX-M and 7 SHV-12 ESBL producing isolates were found express TEM-1 broad- spectrum β-lactamases.High clonal diversity was found amongst ESBL- producing E. coli isolates by random amplified polymorphic DNA (RAPD) analysis. This is the first report of the occurrence of ESBL- producing E. coli in the coastal waters of the Kaštela Bay that have acquired the CTX-M-1 group genes and could function as a mediator for gene flow between marine coastal areas and clinical settings.

Escherichia coli; antibiotic resistance; resistance gene; ESBL; coastal water

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