Research of Staphylococcus aureus genes to enterotoxins and quantification in bulk tank milk

Abstract

Mastitis is the most important disease in dairy herds because has high prevalence, causes damages on production, modifies the gland mammary function. It is a threat to public health because can transmit pathogens to human. The principal bovine mastitis agent is Staphylococcus aureus. These bacteria are very important to public health because produces enterotoxins heat-resistant, resisting to pasteurization and ultrapasteurization, remaining in milk and milk products. The molecular biology is a viable alternative regarding traditional culture methods to microbiology diagnosis to detection and characterization of bacteria. This because it has more typifying and description capacity, speed, good limit of detection, good selectivity and specificity. One hundred samples will be collected from bulk tanks of infected herds with Staphylococcus aureus. These samples will be isolated on Baird-Parker agar to counting CFU and blood agar and later biochemical identification. Following, Staphylococcus aureus and encoding genes to enterotoxins will be identified by genotypic detection. The enterotoxins will be detected and quantified. After, this sample will be divided in two parts. One will be refrigerated and another will be stored at 25ºC, at bacteriological chamber, for 5 hours. In both samples, it will be detected by research, using Polymerase Chain Reaction PCR, encoding genes to enterotoxins sea, seb, sec and sed, and by Reverse Passive Latex Agglutination (RPLA) the enterotoxins A, B, C and D. The present study has as goal to compare the PCR sensitivity and specificity with microbiology exams in identification of Staphylococcus aureus in bulk tank milk. Results obtained will provide important data to standardization the use of PCR and RPLA directly from milk, without be necessary microbiologic isolation to Staphylococcus aureus. Moreover, it will be determinated risks to public health with the growth of enterotoxigenic Staphylococcus aureus in milk stored on field on bad conditions of refrigeration. (AU)