Prevalence and genetic characteristics of fosB-positive Staphylococcus aureus in duck farms in Guangdong, China in 2020.

Abstract

To investigate the epidemiology of fosB-positive Staphylococcus aureus in waterfowl farms in the Pearl River tributaries in Guangdong Province, China in 2020. A total of 63 S. aureus were recovered from 315 samples collected from six duck farms and one goose farm. PFGE, WGS and analysis were performed on 19 fosB-positive S. aureus. The fosfomycin resistance rate of the strains was as high as 52.4% (33/63), and 30.1% (19/63) of the strains carried fosB. Resistance gene prediction results showed that duck farm environment-derived strains contained the oxazolidinone drug resistance gene optrA. All fosB-positive S. aureus were MRSA and most of them were MDR, mainly ST9-t899 and ST164-t899. PFGE showed that fosB-positive S. aureus from humans and ducks could be clustered into the same clade. In addition, core-genome SNP analysis showed that clonal transmission of S. aureus occurred between humans and water. Pan-genome analysis showed that S. aureus had an open pangenome. The fosB gene was located on 2610-2615 bp plasmids, which all contained a broad host-range plasmid replication protein family 13. Small plasmids carrying the fosB gene could be found in different multilocus STs of S. aureus. This study indicated that duck farms in Guangdong, China could be an important reservoir of fosB-positive S. aureus. The spread of drug-resistant bacteria in waterfowl farms requires further monitoring.