Detection of SXT/R391 integrative conjugative elements carrying tigecycline resistance genes in spp. isolated from retail seafood.

Tigecycline is a last resort antibiotic that is used to treat serious infections; however, some bacteria have developed tigecycline resistance by producing a tigecycline-inactivating enzyme or tigecycline resistance efflux pump, encoded by (X) and genes, respectively. Tons of seafood are consumed annually in China; however, whether seafood harbors tigecycline-resistant bacteria is not known. In this study, we isolated various tigecycline-resistant bacteria from retail seafood; among these, was the predominant tigecycline-resistant genus (33/76, 43.4%). Genomic sequencing revealed that two strains carried the (X4) gene, while one strain co-harbored and genes. The (X4) and were found to be located on novel members of the SXT/R391 family of integrated conjugative elements (ICEs). As per our knowledge, this is the first report on the emergence of SXT/R391 ICEs carrying (X4) or gene in strains. The SXT/R391 family ICEs could mediate the spread of tigecycline resistance genes among aquatic bacteria, and contact between seafood and consumers may lead to the dissemination of tigecycline-resistant bacteria. Our study revealed that spp. may act as potential reservoirs of tigecycline resistance genes.