Shewanella algae and Vibrio spp. strains isolated in Italian aquaculture farms are reservoirs of antibiotic resistant genes that might constitute a risk for human health.

The aquatic environment can represent a reservoir of antimicrobial resistance genes. In the present study, phenotypical, biochemical and molecular techniques were used to screen a collection of marine strains isolated in Italian aquaculture farms to investigate their beta-lactam resistance profiles. The genome of 12 carbapenemase and/or beta-lactamase producing strains was sequenced and a phylogenetic analysis of the beta-lactamases found in their chromosomes was performed. Gene annotation and prediction revealed the presence of bla _AmpC and bla _OXA-55-like in all the Shewanella algae isolates whereas in Vibrio anguillarum and Vibrio parahaemolyticus strains, bla _AmpC and bla _CARB-19 were found, respectively. Multiple alignments of OXA-55-like and AmpC protein sequences showed different point mutations. Finally, comparisons between enzyme phylogeny and strain clusterization based on sampling sites and dates indicate the diffusion of specific Multi Drug Resistant (MDR) Shewanella algae clones along the Italian Adriatic coast.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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