TITLE:
Virulence Factor Profile of Staphylococcus aureus Isolated from Bovine Milk from Brazil
AUTHORS:
Verena M. Santos, Hellen B. Martins, Izadora S. Rezende, Maysa S. Barbosa, Ewerton F. Andrade, Simone G. Souza, Guilherme B. Campos, Pollianna S. Oliveira, Daniel S. Sousa, Danilo C. C. Da Silva, Aline T. Amorim, Jorge Timenetsky, Mariluze P. Cruz, Regiane Yatsuda, Lucas M. Marques
KEYWORDS:
Milk, Staphylococcus aureus, Resistance, Virulence Factors
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.5 No.15,
August
27,
2014
ABSTRACT: 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.