Multidrug Resistance, Biofilm-Forming Ability, and Molecular Characterization of Vibrio Species Isolated from Foods in Thailand.

Background: Vibrio species are common foodborne pathogens that cause gastrointestinal tract inflammation. Multidrug resistance (MDR) in Vibrio spp. is a global health concern, especially in aquaculture systems and food chain systems. This study aimed to detect Vibrio contamination in food collected from 14 markets in Nakhon Si Thammarat, Thailand, and determine their antibiotic susceptibility.

Methods: One hundred and thirty-six food samples were investigated for Vibrio contamination. All isolates were tested for antibiogram and biofilm-forming ability. Moreover, the ceftazidime or cefotaxime resistance isolates were additionally investigated for extended-spectrum β-lactamase (ESBL) producers. The isolates were additionally examined for the presence of antibiotic resistance genes. The ESBL-suspected isolates with moderate-to-high biofilm-forming ability were further analyzed for their whole genome.

Results: The prevalence of Vibrio contamination in food samples was 42.65%, with V. parahaemolyticus demonstrating the highest prevalence. Most isolates were resistant to β-lactam antibiotics, followed by aminoglycosides. The overall MDR of isolated Vibrio was 18.29%, with an average multiple antibiotic resistance (MAR) index of 16.41%. Most isolates were found to have β-lactam resistance-related genes (bla_TEM) for 41.46%, followed by aminoglycoside resistance genes (aac(6')-Ib) for 18.29%. Most Vibrio showed moderate to strong biofilm-forming ability, particularly in MDR isolates (92.86%). Two ESBL-suspected isolates, one V. parahaemolyticus isolate and one V. navarrensis, were sequenced. Interestingly, V. parahaemolyticus was an ESBL producer that harbored the bla_CTX-M-55 gene located in the mobile genetic element region. While V. navarrensis was not ESBL producer, this isolate carried the bla_AmpC gene in the region of horizontal gene transfer event. Remarkably, the Inoviridae sp. DNA integration event was present in two Vibrio genomes.

Conclusions: These findings impact the understanding of antibiotic-resistant Vibrio spp. in food samples, which could be applied for implementing control measures in aquaculture farming and food safety plans.