Virulence Factor Profile of Staphylococcus aureus Isolated from Bovine Milk from Brazil

Abstract

This\rstudy investigates the biofilm formation, presence and distribution of\rvirulence genes and the capacity to induce an inflammatory response in strains\rof Staphylococcus aureus isolated\rfrom milk samples in Bahia, Brazil. A total of 132 samples of raw milk were\rcollected from four dairy farms (designated A to D) located in southwestern\rBahia, in the municipality of Vitória da Conquista, from October/2009 to\rSeptember/2010. After processing of the samples, 94 (71.2%) S. aureus isolates were obtained. These\rstrains were subjected to the antibiogram method MIC (Minimum Inhibitory\rConcentration). As for the pathogenicity, tests were performedin vitrobiofilm formation induced by\rglucose. Moreover, we performed PCR for their virulence genes: sea (enterotoxin A), seb (B), sec (C), pvl (Panton-Valentine\rLeukocidin), clfA (Clumping Factor A)\rand spa (protein A) and analysis of\rcytokine induction in the inflammatory response of J774 macrophages by\rexocellular lipoteichoic acid. No isolates were resistant to oxacillin and\rvancomycin. In biofilm production, 5.31% (5/94) isolates did not produce\rbiofilm, 5.31% (5/94) of the samples were poor\rproducers, 15.96% (15/94) strains were moderate producers, 18.09% (17/94) were\rproducers and 55.32% (55/94) of isolates were strong biofilm producers.\rOne (1.06%) isolate expressed the seb gene, one (1.06%) sec, 18 (19.2%) cflA and 44 (46.8%) had spa. There was no expression of sea and pvl between isolates analyzed. The analysis of cytokine induction\rin the inflammatory response did not show statistical difference in the levels\rof IL-6, TNF-α and IL-10 induction.\rHowever, there was statistical difference in IL-1 induction between isolates\rfrom different farms. Thus, it appears that the results obtained in this study\rshow significant effects for the region studied, since it is an important dairy\rregion, hence the need for further studies, with the intent of attracting\rfunding that contributes to improving prevention and control in both dairy\rfarms and dairy industries, since milk contamination poses a serious potential\rhealth risk to consumers.