Distribution of Staphylococcus aureus drug resistance genes, biofilm formation and cell wall characteristics in dairy cattle from dairy farms in Northeast China

Staphylococcus aureus (Staph. aureus) prevalence in dairy cattle herds jeopardizes both herd productivity and public safety. In this study, a total of 282 clinical samples were collected form cattle farms in Heilongjiang, Jilin, and Inner Mongolia, and isolation of Staph. aureus from 62 samples. Through spa typing and disk diffusion assays of 62 isolates, the predominant spa type was identified as t034. Notably, 54 isolates exhibited multidrug resistance, with a penicillin resistance rate as high as 87.1%, and 34 isolates were identified as methicillin-resistant Staph. Aureus ( MRSA ). Among the 11 resistance genes tested, the detection rate of tetM gene was 100%. The Congo red plates and crystal violet staining assay showed that the isolated strains all produced biofilms, with no significant changes in the cell wall. In addition, icaA , SarA , and CidA genes identified as critical regulators of biofilm formation. Results from this study suggest that the feces and milk of dairy cows in Northeast China were contaminated with Staph. aureus including MRSA strains, and these strains carry a variety of resistance genes and have the ability to form biofilms, showing a resistance phenotype to a variety of antimicrobial agents.