Diversity and pathogenesis of Staphylococcus aureus from bovine mastitis: current understanding and future perspectives

Abstract

Staphylococcus aureus is a leading cause of bovine mastitis worldwide. Despite some improved understanding of disease pathogenesis, progress towards new methods for the control of intramammary infections (IMI) has been limited, particularly in the field of vaccination. Although herd management programs have helped to reduce the number of clinical cases, S. aureus mastitis remains a major disease burden. This review summarizes the past 16 years of research on bovine S. aureus population genetics, and molecular pathogenesis that have been conducted worldwide. We describe the diversity of S. aureus associated with bovine mastitis and the geographical distribution of S. aureus clones in different continents. We also describe studies investigating the evolution of bovine S. aureus and the importance of host-adaptation in its emergence as a mastitis pathogen. The available information on the prevalence of virulence determinants and their functional relevance during the pathogenesis of bovine mastitis are also discussed. Although traits such as biofilm formation and innate immune evasion are critical for the persistence of bacteria, the current understanding of the key host-pathogen interactions that determine the outcome of S. aureus IMI is very limited. We suggest that greater investment in research into the genetic and molecular basis of bovine S. aureus pathogenesis is essential for the identification of novel therapeutic and vaccine targets.

Keywords: Bovine mastitis; Clonal complexes; Pathogenesis; Staphylococcus aureus.

Fig. 1

Proteins that have been implicated in the pathogenesis of Staphylococcus aureus of bovine origin. Surface proteins interact with host proteins to promote bacterial adhesion and invasion. Biofilm-associated protein (Bap) interferes in the internalization pathway mediated by FnBP and contributes to biofilm formation, a process that also depends on the ica locus. Toxins such as alpha and beta hemolysins, promote necrosis of the mammary gland tissue and lyse bovine erythrocytes to use hemoglobin as a source of iron. Leukotoxin LukMF´ binds to neutrophils present in the bovine milk. Staphylococcal superantigens activate T-cells resulting in the release of various pro-inflammatory cytokines. Figure created by authors using resources from Smart Servier Medical Art and BioRender