Draft Whole-Genome Sequencing and Phenotypic Analysis of Salmonella from Retail Aquatic Products in Weifang.

Abstract

Salmonella is one of the most common causative agents of infectious diarrhea in humans, but in China, there are very limited data on the presence of Salmonella in aquatic products. This study describes the isolation of Salmonella from aquatic products in Weifang, China, from April 2022 to April 2023. Seven out of 160 (4.38%) retail aquatic product samples were positive for Salmonella. Two distinct serotypes were identified: Salmonella enterica subsp. enterica serovar Senftenberg (n = 4) and S. enterica subsp. diarizonae serovar IIIb 59:z10:z57 (n = 3). The results of molecular typing of isolates with the same serotype were consistent. Only one of the isolates was resistant to ampicillin, while the other isolates were not resistant to the tested antibiotics, suggesting that Salmonella in aquatic products in this region are relatively susceptible to antibiotics. There were 17 resistance genes in the 7 strains, 13 of which were shared. golS, MdtK, mdsA, and mdtG were unique to S. Senftenberg. A total of 155 virulence genes were annotated in the S. Senftenberg isolates, and 136 virulence genes were annotated in the S. IIIb 59:z10:z57 isolates. The S. Senftenberg isolates harbored more adhesion-related genes than the S. IIIb 59:z10:z57 isolates. Multilocus sequence typing analysis revealed that ST34 has been the most prevalent type of Salmonella in China since 2020, followed by ST11. The predominant type of Salmonella in aquaculture is ST14. This study provided additional genetic information about Salmonella in aquatic sources, providing a basis for subsequent research related to risk assessment, antibiotic resistance mechanisms, and so forth.