Prevalence and genetic basis of tetracycline resistance in Vibrio parahaemolyticus isolates recovered from food products in Shenzhen, China during 2013 to 2021

Understanding tetracycline resistance in Vibrio parahaemolyticus from food products is crucial for effective control measures against this foodborne pathogen. This study aimed to investigate the prevalence, evolution routes, and mechanism of transmission of tetracycline resistance in Vibrio parahaemolyticus isolates collected from food products in Shenzhen, China. A total of 2342 non-duplicate Vibrio parahaemolyticus were isolated from 3509 food samples during the period 2013-2021. Among these 2342 Vibrio parahaemolyticus strains, 530 (21.37 %) were resistant to tetracycline. These tetracycline-resistant Vibrio parahaemolyticus strains were mainly isolated from shrimp samples, with the highest resistance rate (46.9 %) observed in 2019. Phylogenetic and genomic analyses of 387 isolates carrying the tet genes revealed that five different types of tet genes (tet(34), tet(A), tet(B), tet(M), and tet(E)) were present. The tet(A) gene was the most common (65 % of isolates), while tet(E) and tet(M) genes were only detected in specific years. Although tet(A) is the most commonly detected gene, it only encodes resistance in a low percentage of strains (47/129). On the other hand, the resistance rate is highest in isolates carrying tet(B) (41/55). Interestingly, V. parahaemolyticus carrying the tet genes were not necessarily tetracycline-resistant, and vice versa. A total of six different types of plasmids and two transposable units were found to carry the tet genes. V. parahaemolyticus strains that harbored these plasmids were often resistant to multiple antibiotics, indicating that horizontal transfer of antibiotic resistance genes is common among V. parahaemolyticus strains. Our findings suggest a high prevalence of tetracycline resistance in Vibrio parahaemolyticus strains recovered from food products in Shenzhen, China. These results provide valuable insight into the evolution and transmission of tetracycline resistance in foodborne Vibrio parahaemolyticus isolates and highlight the need for effective control measures to prevent the spread of antibiotic resistance.