Antimicrobial Resistance, Virulence Factors, and Genetic Profiles of Vibrio parahaemolyticus from Seafood

Abstract

Vibrio parahaemolyticus is a widespread bacterium in the marine environment and is responsible for gastroenteritis in humans. Foodborne infections are mainly associated with the consumption of contaminated raw or undercooked fish and shellfish. The aim of this study was to determine the antimicrobial resistance, virulence factors, and genetic profiles of V. parahaemolyticus isolates from seafood originating from different countries. A total of 104 (17.5%) isolates were recovered from 595 analyzed samples. The isolates were tested for the presence of the tdh and trh genes, involved in the pathogenesis of V. parahaemolyticus infections in humans, and these genes were detected in 3 (2.9%) and 11 (10.6%) isolates, respectively. The trh-positive isolates also possessed the ure gene, which is responsible for urease production. Moreover, the activity of protease A was identified in all V. parahaemolyticus strains. Antimicrobial resistance revealed that most isolates were resistant to ampicillin (75.0%) and streptomycin (68.3%), whereas all strains were sensitive to chloramphenicol and tetracyclines. Most of the isolates (55.8%) showed resistance against two classes of antimicrobials, mainly to ampicillin and streptomycin (46.2%). Only one isolate displayed a multiresistant pattern. Genotypic analysis of V. parahaemolyticus revealed a high degree of diversity among the isolates tested. The pulsed-field gel electrophoresis (PFGE) method distinguished 73 clonal groups, and the most numerous group consisted of 7 strains. Sequencing by the multilocus sequence typing (MLST) method showed 76 sequence types (STs), of which ST481 and ST1361 were most frequently identified. In addition, 51 (67.1%) new sequence types were discovered and added to the PubMLST international database. IMPORTANCE The presence of V. parahaemolyticus in seafood may pose a risk for consumers, especially in countries where shellfish are eaten raw. In recent years, a significant increase of food poisoning caused by these bacteria has been also observed in Europe. Our results highlight the high level of V. parahaemolyticus contamination of seafood, along with the isolates being potentially pathogenic for humans. However, the first-line antimicrobials, such as tetracyclines and fluoroquinolones, remained highly effective against V. parahaemolyticus. The monitoring of antimicrobial resistance of isolates is important to ensure the high efficacy in the treatment of human infections. Most of V. parahaemolyticus strains possessed new sequence types (STs), which showed the high genetic diversity of the isolates tested.