Abstract
Antimicrobial resistance is a major public health concern restricted not only to healthcare settings but also to veterinary and environmental ones. In this study, we analyzed, by whole genome sequencing (WGS) the resistome, mobilome and virulome of 12 multidrug-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 enzyme 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 a 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.
Highlights
Shewanellae are non-fermentative Gram-negative, motile rods that inhabit aquatic and sedimentary environments
In our study we report the results obtained concerning the resistome, mobilome and virulome analysis of 12 MDR marine bacterial strains by whole genome sequencing (WGS), providing new insights on the genes involved in the antimicrobial resistance (AMR) mechanisms
Next-generation sequencing (NGS) technology is a useful means of detecting antimicrobial resistance gene (ARG), mobile genetic elements (MGEs) and virulence factors its reliability is dependent upon the availability of updated databases
Summary
Shewanellae are non-fermentative Gram-negative, motile rods that inhabit aquatic and sedimentary environments. The antibiotic therapy adopted includes beta-lactams, aminoglycosides and quinolones These bacteria are generally susceptible to third and fourth generation cephalosporins, carbapenems, beta-lactamase inhibitor combinations, aminoglycosides, chloramphenicol, erythromycin, aztreonam and quinolones [2,5,6]. V. anguillarum represents the causative agent of a deadly haemorrhagic septicaemic disease affecting various marine and fresh or brackish water fish, bivalves and crustaceans [21]. It harbors a genome containing several MGEs such as plasmids, superintegrons and insertion sequences (ISs) carrying cargo genes, resistance and virulence genes [21]. Tetracyclines, aminoglycosides, third generation cephalosporins and fluoroquinolones are generally used as antibiotic therapy in human vibriosis outbreaks [13,22] but, several cases of multidrug-resistant (MDR) vibrios are reported in literature even to the last-resort antibiotics used in human medicine such as carbapenems [22,23,24,25,26,27]
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