Panel of enterotoxins in Staphylococcus aureus, isolated from milk of cows with clinical and subclinical mastitis

Abstract

Milk and its derivatives are one of the most consumed foods in the world, and its quality is essential for human consumption to avoid foodborne diseases. But in Brazil, despite the advances in the past decades, approximately 27% of the population still consumes unpasteurized or "informal" milk and derivatives. One of the main pathogenic bacteria found in this kind of food is Staphylococcus aureus, which causes food poisoning due to the ingestion of enterotoxins pre-formed in the food. This bacterium is very frequent in milk because it is also one of the main causes of bovine mastitis, configuring an example of One Health since it involves a pathogen causing diseases in livestock and in humans, representing a serious public health problem. Mastitis is the disease that causes most economic losses to producers and can manifest itself in clinical and subclinical forms, the latter being the most common. The first one, causes visual symptoms, such as swelling, fever, hardening of the mammary gland, or any change in the characteristics of the milk. Considering subclinical mastitis, there are no visible signs in the animal nor changes in the milk. S. aureus has many important virulence factors for the establishment of its pathogenicity in animals, such as enterotoxins, which are also responsible for foodborne poisoning. The objective of the present study is to perform a comparative analysis between isolates of S. aureus, obtained from the milk of cows with clinical and subclinical mastitis, in relation to the presence of these enterotoxins. All enterotoxins described till now will be investigated. Isolates showing the classical enterotoxins genes (sea-sed) will also be tested for in vitro production. In addition, since these bacteria can be ingested when unpasteurized milk is consumed, there may be methicillin-resistant isolates (MRSA), which can adapt to the intestinal microbiota and the individual becomes a carrier of this multiresistant bacteria, and therefore, the two genes (mecA and mecC) responsible for this resistance to most ²-lactam antimicrobials will also be investigated. (AU)