Toxic bovine mastitis caused by Staphylococcus aureus in twin cows

Area of Science:

• Veterinary Medicine
• Microbiology
• Genomics

Background:

• Bovine mastitis is a significant concern in dairy farming.
• Toxic mastitis, a severe form, requires rapid diagnosis and understanding of causative agents.
• Staphylococcus aureus (S. aureus) is a common pathogen in bovine mastitis.

Observation:

• Two recently calved cows presented with anorexia, pyrexia, elevated heart rate, and signs of severe mastitis.
• Affected mammary glands were swollen, hardened, and secreted brownish or bloody fluid.
• Both cows rapidly deteriorated and were euthanized within 48 hours.

Findings:

• The S. aureus strain isolated from both cows belonged to spa type t267, agr type I, capsule type 5, and CC97.
• This CC97 clonal complex is linked to emerging methicillin-resistant S. aureus (MRSA) clones.
• The identified strain lacked antimicrobial resistance genes, enterotoxin genes, toxic shock syndrome toxin, and exfoliative toxins.

Implications:

• The absence of known virulence and resistance genes suggests host susceptibility plays a key role in this rare toxic mastitis presentation.
• Understanding host-pathogen interactions is critical for managing severe S. aureus infections in cattle.
• Further research into host factors influencing toxic mastitis pathogenesis is warranted.