engleski

First report of the emergence of CTX-M-type extended spectrum beta-lactamase among Aeromonas species in coastal waters of the central Adriatic Sea, Croatia

The spread of multiresistant Aeromonas species is widely recognized, but data about their sources, presence, mechanisms of antimicrobial resistance in the coastal marine ecosystems remains a scarcely explored. Here we describe a molecular survey aimed at determining the population structure, antimicrobial resistance patterns, the presence of extended-spectrum- beta-lactamases (ESBLs) and prevalence of class 1 and 2 integrons in Aeromonas strains recovered from seawater along the eastern coast of the central Adriatic Sea, Croatia. For this purpose, a total of 127 Aeromonas isolates (85 A. caviae and 42 A. hydrophila) were surveyed in this study. Sampling was carried out between 2008 and 2010. Isolates were previously identified from 16S rDNA and gyrB sequencing. Susceptibility to 20 antibiotics was tested by disk-diffusion method. Searches for blaTEM, blaSHV, blaCTX-M genes were performed by PCR amplification, and the genotypes of ESBLs were determined by direct nucleotide sequence analysis. Epidemiological relatedness of isolates harboring bla genes was assessed using macrorestriction profile analysis by RAPD-PCR. Out of 127 Aeromonas isolates recovered, 92 (72.4%) demonstrated multiresistance phenotype. The resistances detected most frequently were against ampicillin, tetracycline, piperacillin, gentamicin, tobramicin, trimethoprim/ sulfamethoxazole. Among those thirty two cephalosporins resistant Aeromonas isolates, 29 displayed an ESBL phenotype. All the ESBL- positive isolates were multiresistant, with resistance to six to eleven of the antibiotics tested, and were positive for the blaSHV-12 and blaCTX-M-15 genes. Sixty percent of multiresistant strains harbored class 1 or 2 integrase genes. This study constitutes the first description of blaCTX-M-15 genes among Aeromonas strains recovered from seawater used for human recreation or consumption seafood, highlighting the coastal seawater as potential reservoirs and/or vehicles of these clinically relevant resistance genes.

Aeromonas; CTX-M; extended spectrum beta-lactamase; antimicrobial resistance; coastal marine waters

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