Occurrence and Molecular Characterization of Potentially Pathogenic Vibrio spp. in Seafood Collected in Sicily

Public health aspects of Vibrio spp. related to the consumption of seafood in the EU

Vibrio parahaemolyticus, Vibrio vulnificus and non-O1/non-O139 Vibrio cholerae are the Vibrio spp. of highest relevance for public health in the EU through seafood consumption. Infection with V. parahaemolyticus is associated with the haemolysins thermostable direct haemolysin (TDH) and TDH-related haemolysin (TRH) and mainly leads to acute gastroenteritis. V. vulnificus infections can lead to sepsis and death in susceptible individuals. V. cholerae non-O1/non-O139 can cause mild gastroenteritis or lead to severe infections, including sepsis, in susceptible individuals. The pooled prevalence estimate in seafood is 19.6% (95% CI 13.7-27.4), 6.1% (95% CI 3.0-11.8) and 4.1% (95% CI 2.4-6.9) for V. parahaemolyticus, V. vulnificus and non-choleragenic V. cholerae, respectively. Approximately one out of five V. parahaemolyticus-positive samples contain pathogenic strains. A large spectrum of antimicrobial resistances, some of which are intrinsic, has been found in vibrios isolated from seafood or food-borne infections in Europe. Genes conferring resistance to medically important antimicrobials and associated with mobile genetic elements are increasingly detected in vibrios. Temperature and salinity are the most relevant drivers for Vibrio abundance in the aquatic environment. It is anticipated that the occurrence and levels of the relevant Vibrio spp. in seafood will increase in response to coastal warming and extreme weather events, especially in low-salinity/brackish waters. While some measures, like high-pressure processing, irradiation or depuration reduce the levels of Vibrio spp. in seafood, maintaining the cold chain is important to prevent their growth. Available risk assessments addressed V. parahaemolyticus in various types of seafood and V. vulnificus in raw oysters and octopus. A quantitative microbiological risk assessment relevant in an EU context would be V. parahaemolyticus in bivalve molluscs (oysters), evaluating the effect of mitigations, especially in a climate change scenario. Knowledge gaps related to Vibrio spp. in seafood and aquatic environments are identified and future research needs are prioritised.

Multidrug resistant Vibrio spp. identified from mussels farmed for human consumption in Central Italy

AIMS

This study investigated phenotypic and genotypic antimicrobial resistance profiles of Vibrio strains identified from Mytilus galloprovincialis farmed for human consumption in the Adriatic Sea Central Italy.

METHODS AND RESULTS

A total of 475 mussels (M. galloprovincialis) were involved in the present study, and culture-dependent microbiological methods permitted to identify a total of 50 Vibrio strains that were tested for antibiotic susceptibility followed by the genetic determinant detections. Antibiograms showed resistance against ampicillin (36.0%), amoxicillin-clavulanic acid (30.0%), gentamycin (14.0%), and imipenem (18.0%). Biomolecular assays amplified a total of 264 antibiotic resistance genes harbored by both susceptible and resistant Vibrio species. Among resistance genes, aacC2 (62.0%) and aadA (58.0%) for aminoglycosides, blaTEM (54.0%) for beta-lactams, qnrS (24.0%) for quinolones, tetD (66.0%) for tetracyclines, and vanB (60.0%) for glycopeptides were mainly amplified by PCR assays.

CONCLUSIONS

Vibrio genus is involved in the antibiotic resistance phenomenon diffusion in the aquatic environments, as demonstrated by the harboring of many genetic determinants representing a kind of genetic "dark world".

Detection of pathogenic Vibrio spp. in foods: polymerase chain reaction-based screening strategy to rapidly detect pathogenic Vibrio parahaemolyticus, Vibrio cholerae, and Vibrio vulnificus in bivalve mollusks and preliminary results

The majority of human diseases attributed to seafood are caused by Vibrio spp., and the most commonly reported species are Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae. The conventional methods for the detection of Vibrio species involve the use of selective media, which are inexpensive and simple but time-consuming. The present work aimed to develop a rapid method based on the use of multiplex real-time polymerase chain reaction (PCR) to detect V. parahaemolyticus, V. vulnificus, and V. cholerae in bivalve mollusks. 30 aliquots of bivalve mollusks (Mytilus galloprovincialis) were experimentally inoculated with two levels of V. parahaemolyticus, V. vulnificus, and V. cholerae. ISO 21872-1:2017 was used in parallel for qualitative analysis. The limit of detection of 50% was 7.67 CFU/g for V. cholerae, 0.024 CFU/g for V. vulnificus, and 1.36 CFU/g for V. parahaemolyticus. For V. vulnificus and V. cholerae, the real-time PCR protocol was demonstrated to amplify the pathogens in samples seeded with the lowest and highest levels. The molecular method evaluated showed a concordance rate of 100% with the reference microbiological method. V. parahaemolyticus was never detected in samples contaminated with the lowest level, and it was detected in 14 samples (93.33%) seeded with the highest concentration. In conclusion, the developed multiplex real-time PCR proved to be reliable for V. vulnificus and V. cholerae. Results for V. parahaemolyticus are promising, but further analysis is needed. The proposed method could represent a quick monitoring tool and, if used, would allow the implementation of food safety.

Microbiological and Toxicological Investigations on Bivalve Molluscs Farmed in Sicily

Bivalves can concentrate biological and chemical pollutants, causing foodborne outbreaks whose occurrence is increasing, due to climatic and anthropic factors that are difficult to reverse, hence the need for improved surveillance. This study aimed to evaluate the hygienic qualities of bivalves sampled along the production and distribution chain in Sicily and collect useful data for consumer safety. Bacteriological and molecular analyses were performed on 254 samples of bivalves for the detection of enteropathogenic Vibrio, Arcobacter spp., Aeromonas spp., Salmonella spp., and beta-glucuronidase-positive Escherichia coli. A total of 96 out of 254 samples, collected in the production areas, were processed for algal biotoxins and heavy metals detection. Bacterial and algal contaminations were also assessed for 21 samples of water from aquaculture implants. Vibrio spp., Arcobacter spp., Aeromonas hydrophila, Salmonella spp., and Escherichia coli were detected in 106/254, 79/254, 12/254, 16/254, and 95/254 molluscs, respectively. A total of 10/96 bivalves tested positive for algal biotoxins, and metals were under the legal limit. V. alginolyticus, A. butzleri, and E. coli were detected in 5, 3, and 3 water samples, respectively. Alexandrium minutum, Dinophysis acuminata, Lingulodinium polyedra, and Pseudonitzschia spp. were detected in water samples collected with the biotoxin-containing molluscs. Traces of yessotoxins were detected in molluscs from water samples containing the corresponding producing algae. Despite the strict regulation by the European Commission over shellfish supply chain monitoring, our analyses highlighted the need for efficiency improvement.

Predominance of Multidrug-Resistant Gram-Negative Bacteria Isolated from Supermarket Retail Seafood in Japan

Reports have documented antimicrobial usage in aquaculture, and the aquatic ecosystem can be considered a genetic storage site for antibiotic-resistant bacteria. This study assessed the prevalence of antimicrobial resistance (AMR) among Gram-negative bacteria recovered from retail seafood in Hiroshima, Japan. A total of 412 bacteria were isolated and screened for the presence of β-lactamases, acquired carbapenemases, and mobile colistin-resistance (mcr) genes. Forty-five (10.9%) isolates were dominated by Morganella (28%), Proteus (22%), Aeromonas (14%), Citrobacter (8%), and Escherichia (8%) and carried AMR genes. The identified AMR genes included those encoded in integrons (19), aac(6՛)-Ib (11), blaTEM-1 (7), blaCTX-M-like (12), blaCTX-M-65 (2), blaSHV-12 (1), blaSHV-27 (1), blaOXA-10 (1), blaOXA-2 (1), and mcr (2). The most common clinical resistances were against ampicillin, colistin, sulfamethoxazole/trimethoprim, tetracycline, and ciprofloxacin. Multidrug resistance (MDR) occurred in 27 (60%) AMR isolates, and multiple antibiotic resistance indices ranged from 0.2 to 0.8. A conjugation experiment showed that 10 of the 11 selected MDR strains harbored conjugable plasmids, although PCR-based replicon typing described seven strains as untypable. IncF replicon was identified in MDR extended-spectrum β-lactamase-producing Escherichia coli of the pathogenic B2 phylogroup. Our findings suggest that retail seafood harbors MDR bacteria of human interest that require strict resistance surveillance in the seafood production continuum.