engleski

Widespread dissemination of SHV-12 extended spectrum beta-lactamase among bacterial species in coastal waters of the Kaštela Bay

Coastal microbial communities maintain diverse collections of resistance genes, which can be mobilized into pathogenic bacteria. Recently, exceptional environmental releases of antibiotics and other contaminants have been documented, but the effects on the promotion of resistance genes and the potential for horizontal gene transfer have yet received limited attention. Therefore, this study aimed to evaluate antimicrobial resistance profiles and the types of extended spectrum beta- lactamase (ESBL) genes and their location on plasmids among 352 isolates recovered from seawater of the Kaštela Bay, Adriatic Sea, Croatia. Susceptibility to panel antimicrobials was tested by broth microdilution and showed similar profiles in thirty-three isolates, characterized by elevated MICs (256 mg/ml) of amoxicillin, ceftazidime and cefepime but remained susceptible to imipenem. Screening for ESBL gene was performed by PCR. An 875-pb fragment of SHV-type gene was amplified and after sequencing was identified as a blaSHV-12 gene in nine Escherichia coli, six Enteribacter cloaceae, one E. intermedius, three E aerugenes, one Klebsiella pneumoniae, one K. oxytoca, four Raultella terrigena, nine Aeromonas caviae, and one A. hydrophylla isolates. PCR mapping of the genetic environment surrounding the blaSHV-12 gene with primers specific for insertion sequence IS26 for blaSHV gene showed that the eleven strains contained the same IS26 elements. This study suggests that the dissemination of blaSHV-12 among different species may be mediated by the mobile element. In all, the conjugation experiments transconjugants indicated that the blaSHV-12 was located on over 100 kb single conjugative plasmid. The results suggest that contaminated coastal seawater plays a role in the promotion of resistance genes and their mobilization from environmental microbes to other species and eventually to human pathogens.

antimicrobial resistance; SHV-12; extended-spectrum beta-lactamase; coastal waters

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