Prevalence and genetic characteristics of<i>fosB</i>-positive<i>Staphylococcus aureus</i>in duck farms in Guangdong, China in 2020

Abstract

OBJECTIVES: To investigate the epidemiology of fosB-positive Staphylococcus aureus in waterfowl farms in the Pearl River tributaries in Guangdong Province, China in 2020. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.