Host immune response factors associated with Staphylococcus aureus chronic intramammary infections

Staphylococcus aureus is one of the main causes of mastitis in dairy cows worldwide. The most common form of the disease is characterized by chronic subclinical infection with sporadic clinical episodes that can persist throughout the life of the animal. Once infection evolves to chronicity, the bacteriological cure rate following classic antibiotic therapy is low and persistently infected cows become the main reservoir of the organism in a dairy herd. The establishment and persistence of S. aureus intramammary infection (IMI) has been associated with certain characteristics of the pathogen that induce an impaired immune response unable to eliminate the pathogen. In a related review, the most relevant pathogen factors associated with the establishment and chronicity of S. aureus IMI were covered. This review summarizes current knowledge about the most relevant components of the host’s innate and adaptive immune response that are associated with the establishment and chronicity of S. aureus IMI. A better understanding of these factors will allow the development of intervention strategies aimed at improving different aspects of the control of this disease, including diagnostic methods, therapeutics and modulation of the host immune response.