Current concepts on the impact of coagulase-negative staphylococci causing bovine mastitis as a threat to human and animal health – a review*

Staphylococci are the main aetiological factor of bovine mastitis in many dairy herds. Traditionally, coagulase-negative staphylococci (CNS) were considered a normal skin microbiota. Lately the role of CNS in bovine mastitis has increased, as in some countries these pathogens had started to outnumber other mastitis aetiological factors. Given the scale of mastitis problems, the intensive use of antibiotics in dairy cattle, the number of animals and the consumption of milk products there is an urgent need to highlight the threat to both human and animal health originating from CNS. The knowledge of how CNS mastitis develops, spreads in herd and persists is limited. Bovine strains of CNS are poorly characterised; moreover, they are characterised mainly in terms of phenotypes. This review summarises knowledge on the characterisation of CNS strains, stressing the role of the bacterial genotype, in the context of the risk to human and animal health. Selected CNS virulence factors that play a role during mastitis in dairy cattle are listed and described in this paper. They have been selected subjectively by the authors in view of their significance for public health (toxins, antimicrobial resistance) and their importance for animal health (formation of biofilm, prevention of phagocytosis intracellular survival) and mastitis outcome.