Antimicrobial resistance and virulence genes of Arcobacter isolates recovered from edible bivalve molluscs

The goals of this study were to assess the prevalence, antimicrobial susceptibility and the presence of virulence genes of arcobacters recovered from edible bivalve molluscs. A total of 106 samples (21 clams, 18 mussels, 20 oysters, 20 razor clams, 11 scallops and 16 surf clams) were analysed by culture between 2010 and 2013. The obtained colonies were identified by multiplex PCR and PCR-RFLP and genotyped by ERIC-PCR. Furthermore, nine putative virulence genes (cadF, ciaB, cjl349, irgA, hecA, hecB, mviN, pldA and tlyA) were assessed by PCR and the antimicrobial resistance was tested by the dilution agar method. The global prevalence was 40.5%, with the highest value in surf clams (87.5%) followed by razor clams (65.0%), mussels (33.3%), clams (23.8%), scallops (18.0%) and oysters (15.0%). The most commonly found species was Arcobacter butzleri (62%) followed by Arcobacter cryaerophilus (21%), Arcobacter skirrowii (16%) and Arcobacter defluvii (1%). A high resistance was found to nalidixic acid and ampicillin, while the predominant detected virulence genes were mviN (83.8%), ciaB (82.8%) and tlyA (72.7%). Our results indicate a high prevalence of arcobacters in shellfish and the pathogenic potential of the recovered isolates suggests that this type of food could be a plausible transmission route of virulent strains to humans.