Bovine milk microbiota: molecular characterization and evaluation of mastitis pathogens detection methodologies

• Ano de defesa: 2022
• Autor(a) principal: Trevisoli, Priscila Anchieta
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Bovine milk; Leite bovino; Mastitis pathogen; Microbioma; Microbiome; Patógenos de mastite; Sequenciamento 16S; Sequencing 16S
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/11/11139/tde-13122022-102859/

Bovine milk has high nutritional values and is an important food for the human diet. Its composition rich in water, fats, proteins, carbohydrates, vitamins and minerals provides a favorable environment for the growth and proliferation of microorganisms. Microorganisms classified as psychrotrophic have the ability to proliferate and produce proteolytic and lipolytic enzymes at low temperatures. These enzymes are heat resistant and therefore, even with thermal procedures for the elimination of the microorganism, these enzymes remain active, degrading proteins and fats, spoiling the final quality of the dairy product. Others pathogenic microorganisms are carried by milk causing diseases in humans, such as brucellosis, listeriosis and tuberculosis. The presence of certain microorganisms in the mammary gland can cause inflammation, a disease commonly known as mastitis. Due to its great financial impact, the correct and rapid detection of the causative pathogen is very important. Currently, the most used methods, such as conventional culture, culture with chromogenic media and by mass spectrometry (MALDI-TOF), are dependent on bacterial culture and therefore have a low efficiency. With the advances in molecular techniques, methods such as quantitative PCR (qPCR) and sequencing of part of the 16S gene have been establishing space as alternative methodologies for the detection of these pathogens. In this work, the bovine raw milk microbial profile produced in southeastern Brazil was characterized using sequencing of the v4 region of the 16S gene. The microbial profile was also correlated with milk quality indicators such as somatic cell count (SCC) and total bacterial count (SPC). As results, abundances of Streptococcus agalactiae was correlated with SCC and SPC; Streptococcus dysgalactiae was correlated with SCC, Lactococcus lactis and Staphylococcus aureus with SPC. In addition, we comparatively tested five methodologies, namely conventional culture, chromogenic medium culture, MALDI-TOF MS, multiplex qPCR and 16S sequencing, and discussed their advantages and limitations for a sensitive, rapid and accurate detection of mastitis-related pathogens.