Abstract
BackgroundStaphylococcus aureus, a common cause of bovine mastitis, is known for its ability to acquire to antimicrobial resistance and to secrete numerous virulence factors that can exacerbate inflammation. In addition, alpha-hemolysin has an important role in S. aureus infections, diversity of the hla gene (that produces alpha-hmolysin) in S. aureus isolated from bovine mastitis has not been well characterized. The objective was, therefore, to determine diversity of virulence genes, hla gene sequences, and clonal profiles of S. aureus from bovine mastitis in Chinese dairy herds, and to evaluate inter-relationships.ResultsThe antimicrobials resistance varies from as low as 1.9% (2/103) for CTX to as high as 76.7% (79/103) for penicilin in the 103 isolates and 46 (44.7%) S. aureus were determined as multi-resistant isolates with diverse resistance patterns. Thirty-eight virulence gene patterns (with variable frequencies) were identified in the 103 isolates and correlated with MLST types, indicating a great diversity. Although the hla gene also had great diversity (14 genotypes), Hla peptides were relatively more conserved. With 7 clonal complexes identified from 24 spa types and 7 MLST types. Regarding the letter, ST 97 was the dominant type in S. aureus from bovine mastitis in China. Furthermore, based on phylogenetic analysis, there was a distinct evolutionary relationship between the hla gene and MLST.ConclusionMulti-resistant S. aureus occurred in bovine mastitis with diverse resistance patterns. The diversity of virulence gene profiles, especially the hla gene and, their relationship with molecular types were reported for the first time in S. aureus from bovine mastitis, which will be useful for future studies on immunogenicity and vaccine development. In addition, based on the distinct evolutionary relationship between the hla gene and MLST types, we inferred that the hla gene has potential role for molecular typing of S. aureus.
Highlights
Staphylococcus aureus, a common cause of bovine mastitis, is known for its ability to acquire to antimicrobial resistance and to secrete numerous virulence factors that can exacerbate inflammation
A total of 103 S. aureus isolates from 1021 clinical mastitis samples collected from 2013 to 2016 on 19 dairy farms in 9 provinces of China were used in this study (Table 1)
Antimicrobial resistance patterns Overall, there were only 5 S. aureus isolates susceptible to all tested antimicrobial compounds, as shown in Number of types Patterns of resistance of resistance
Summary
Staphylococcus aureus, a common cause of bovine mastitis, is known for its ability to acquire to antimicrobial resistance and to secrete numerous virulence factors that can exacerbate inflammation. Alpha-hemolysin has an important role in S. aureus infections, diversity of the hla gene (that produces alphahmolysin) in S. aureus isolated from bovine mastitis has not been well characterized. Staphylococcus aureus, one of the most prevalent etiologic agents, has an important role in clinical and subclinical mastitis, characterized by Staphylococcus aureus is known for the ability to develop resistance to antimicrobial agents (e.g. methicillinresistant S. aureus, vancomycin-intermediate S. aureus, and vancomycin-resistant S. aureus) and to secrete numerous virulence factors to exacerbate inflammation. Characterization of virulence gene profiles and clonal diversity among S. aureus populations are very important in development of anti-virulence therapies [6,7,8,9]. It is important to characterize genetic polymorphism of the hla gene
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