Detecção molecular de patógenos causadores de mastite bovina e a sua relação com a contagem das células somáticas do leite cru refrigerado

Abstract

Mastitis is a common infection of the mammary gland in dairy cattle, caused by various organisms and affecting milk quality. For milk to be considered acceptable, it must meet specific physicochemical standards that include limits for total bacterial count and somatic cell count (SCC), with the latter serving as a critical indicator of mastitis. The real-time polymerase chain reaction (PCR) technique proves to be effective in detecting multiple pathogens, facilitating the diagnosis and control of the disease. This study aimed to develop a molecular method to identify the principal microorganisms associated with mastitis in 39 samples of refrigerated raw milk. The results indicated that the primers allowed for the specific amplification of 14 targets, capable of detecting up to 200 copies of DNA per PCR, without cross-reactions with the assessed non-target microorganisms. Of the samples, 82.1% exceeded the permissible SCC limit, signifying a risk to herd health. Although 52.3% of the samples harbored high-risk pathogens, none amplified all 14 target primers, suggesting a high SCC does not invariably reflect active bacterial infections. The most prevalent pathogens included Streptococcus dysgalactiae, Enterococcus faecalis, and Staphylococcus aureus, along with coagulase-negative Staphylococcus strains, which can cause intramammary infections, particularly in herds with low immunity. The results demonstrate that the assay is precise, specific, and sensitive, rendering it an invaluable tool for detecting the key mastitis pathogens in both clinical and subclinical forms. This empowers producers to enhance herd health and milk quality.