First Detection of Ampicillin Resistant Gene (blaTEM) Isolated from Vibrio Species in Northern Italy

With this study we investigated the resistance and the presence of resistance genes in 22 Vibrio spp. strains isolated from Crassostrea gigas oysters collected from the Golfo della Spezia (Liguria, Italy). Colonies were identified by MALDITOF mass spectrometry and tested for antibiotic susceptibility using a broth microdilution method. Primer pairs for gene amplification of tet, bla, qnr, sul and mcr were used to screen for resistance determinants. Potentially pathogenic Vibrio species were detected: V. alginolyticus (68%), V. harveyi (18%), and V. parahaemolyticus (14%). Multiplex PCR revealed the blaTEM gene, which was responsible for ampicillin resistance in 68% of identified strains. High levels of resistance were observed also for ciprofloxacin (91%), ampicillin (73%), and colistin (73%); 45% of the isolates were resistant to three antibiotics. To the best of our knowledge, this is the first study to report Vibrio strains encoding the blaTEM gene in Crassostrea gigas oyster samples from Northern Italy and to find an association between phenotypic and genotypic ampicillin resistance. This finding indicates raw oysters as a possible source of antibiotic-resistant Vibrio carrying resistance determinants and a potential for spread of resistance through the food chain.