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

This study investigates the biofilm formation, presence and distribution of virulence genes and the capacity to induce an inflammatory response in strains of Staphylococcus aureus isolated from milk samples in Bahia, Brazil. A total of 132 samples of raw milk were collected from four dairy farms (designated A to D) located in southwestern Bahia, in the municipality of Vitória da Conquista, from October/2009 to September/2010. After processing of the samples, 94 (71.2%) S. aureus isolates were obtained. These strains were subjected to the antibiogram method MIC (Minimum Inhibitory Concentration). As for the pathogenicity, tests were performedin vitrobiofilm formation induced by glucose. Moreover, we performed PCR for their virulence genes: sea (enterotoxin A), seb (B), sec (C), pvl (Panton-Valentine Leukocidin), clfA (Clumping Factor A) and spa (protein A) and analysis of cytokine induction in the inflammatory response of J774 macrophages by exocellular lipoteichoic acid. No isolates were resistant to oxacillin and vancomycin. In biofilm production, 5.31% (5/94) isolates did not produce biofilm, 5.31% (5/94) of the samples were poor producers, 15.96% (15/94) strains were moderate producers, 18.09% (17/94) were producers and 55.32% (55/94) of isolates were strong biofilm producers. One (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 in the inflammatory response did not show statistical difference in the levels of IL-6, TNF-α and IL-10 induction. However, there was statistical difference in IL-1 induction between isolates from different farms. Thus, it appears that the results obtained in this study show significant effects for the region studied, since it is an important dairy region, hence the need for further studies, with the intent of attracting funding that contributes to improving prevention and control in both dairy farms and dairy industries, since milk contamination poses a serious potential health risk to consumers.

Virulence Factors in Methicillin-Resistant Staphylococcus aureus Isolated from ICU Units in Brazil

Species of Staphylococcus are common in hospital infection (HI). Methicillin resistant S. aureus (MRSA) has also become a serious problem in Brazilian HI. The aim of this study was to characterize the pathogenicity of methicillin-resistant S. aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) isolated in public hospitals. The clinical isolates were obtained from intensive care unit. The MRSA and MSSA strains were genotyped by PCR for detection genes related to virulence factors. Moreover, the strains were tested for biofilm formation and cytokine induction in macrophages. Three strains of MRSA (9.68%) expressed the Sea gene, one (3.23%) Seb, 17 (54.84%) Spa and seven (22.58%) had PVL. Two MSSA strains (2.98%) expressed the Sea gene, three (4.48%) Seb, 18 (26.87%) Spa and 11 (16.42%) showed positive results for the PVL gene. There was no expression of Sec and CflA between MRSA and MSSA strains. Among MRSA and MSSA isolates, none statistical differences were observed in biofilm production. The analysis of cytokine induction in the inflammatory response of J774 macrophages by MRSA and MSSA isolates did not show statistical difference. Understanding the mechanisms of pathogenesis of S. aureus could provide important clues for both preventing and treating infection caused by these organisms.