Resistome, mobilome and virulome analysis of Shewanella and Vibrio strains isolated in Italian aquaculture centers

Antimicrobial resistance is a great public health concern restricted not only to healthcare settings but affecting also the veterinary and environmental ones. In this study, we analyzed by Whole Genome Sequencing (WGS) the resistome, mobilome and virulome of 12 multi drug resistant (MDR) marine strains belonging to Shewanellaceae and Vibrionaceae families collected at aquaculture centers in Italy. The results evidenced the presence of several resistance mechanisms including enzymes and efflux pump systems conferring resistance to beta-lactams, quinolones, tetracyclines, macrolides, polymyxins, chloramphenicol, fosfomycin, erythromycin, detergents and heavy metals. Mobilome analysis did not find circular elements but class I integrons, Integrative and Conjugative Element (ICE) associated modules, prophages and different Insertion Sequence (IS) family transposases. These Mobile Genetic Elements (MGEs) are usually present in other aquatic bacteria but also in Enterobacteriaceae suggesting their transferability among autochthonous and allochthonous bacteria of the resilient microbiota. Regarding the presence of virulence factors, hemolytic activity was detected both in the Shewanella algae and in Vibrio spp. strains. To conclude, these data indicate the role as reservoir of resistance and virulence genes in the environment of the aquatic microbiota present in the examined Italian fish farms that potentially might be transferred to bacteria of medical interest.