Staphylococcus aureus de origem bovina: tipagem genotípica e fenotípica de fatores de virulência, produção de biofilme, perfil de susceptibilidade a antimicrobianos criticamente importantes e genes promissores ao desenvolvimento de vacinas

Abstract

The knowledge of the virulence factors of Staphylococcus aureus is essential for the development of epidemiological studies, as they show the potential pathogenicity of strains involved in bovine mastitis, and possible targets for the development of vaccines. The main objective of the work was to associate the genotypic and phenotypic profiles, with typing by spa Typing in S. aureus isolates from bovine milk, to gather evidence on the frequency of genes linked to virulence factors, and their possible relationships in the determination of mastitis. Specifically, correlations were observed between the results of the spa Typing, with the formation of biofilm and antimicrobial resistance, as well as the combinations between the spa types with the frequency of promising genes for the development of vaccines, leukotoxins, superantigens and the gene of the lactose carrier. From 56 animals with subclinical and clinical intramammary infection, samples of milk and nasal cavities were collected, with subsequent confirmation of S. aureus by microbiological, biochemical and nuc gene PCR. To identify the panel of S. aureus virulence factors, regulatory genes, biofilm production, antimicrobial resistant, candidate proteins for vaccine development, leukotoxins, superantigens and the lactose transporter were selected. The biofilm formation phenotype and the minimal inhibitory concentration of ten antimicrobials critically important for unique health were also evaluated. Variations in the protein A gene of S. aureus isolates were evaluated by spa Typing. The results showed simultaneous amplification of agr, icaABCD operon and bap gene in 42.2% of the isolates. The weakly adherent phenotype for biofilm formation was identified in 86.2% of the isolates and multidrug resistance was detected in 18.4%. The lukED gene was present in 90.4% of the isolates and can be an efficient mechanism for maintaining the pathogen in the mammary gland, while pvl was identified in 0.9%. No evaluated superantigen (sea, seb, sec1 and tst) was identified in the herds and the lactose transporter gene was observed in 99.7% of the isolates. The presence of the sdrE, isdH, eno, fusA, pgk, cysS, atpF and dapE genes was frequently observed in herds, suggesting that they are conserved and suitable for future epidemiological surveys seeking antigen-coding gene targets for vaccines against bovine mastitis caused by S. aureus.