Atypical staphylococcal mastitis in a dairy herd

Area of Science:

• Veterinary Microbiology
• Bovine Diseases
• Zoonotic Pathogens

Background:

• Mastitis is a significant concern in dairy herds, impacting animal health and milk production.
• Coagulase-positive staphylococci are common mastitis pathogens, but specific strain identification is crucial for control.
• Previous investigations noted increased mastitis prevalence in this specific herd.

Purpose of the Study:

• To investigate the cause of increased mastitis prevalence in a cattle herd.
• To characterize the staphylococcal isolates from milk samples.
• To determine the potential link between human and bovine staphylococcal strains.

Main Methods:

• Bacteriologic analysis of milk samples from the cattle herd.
• Characterization of staphylococcal isolates using hemolysin production and phage typing.
• Investigation of nasal carriage of staphylococci in human contacts.
• Coagulase reaction testing in bovine plasma.

Main Results:

• Approximately 50% of the herd yielded coagulase-positive staphylococci in milk.
• 55% of these isolates exhibited characteristics similar to human staphylococcal strains.
• Human contacts were identified as nasal carriers of these staphylococci.
• The bovine staphylococcal isolates produced a granular coagulase reaction, differing from the typical clot-type.
• Mastitis in the herd was predominantly nonclinical and resistant to antibiotic treatment.

Conclusions:

• Human-like staphylococcal strains are circulating in the investigated cattle herd.
• These strains are associated with nonclinical mastitis that is difficult to treat with antibiotics.
• Human-bovine transmission of specific staphylococcal strains is likely occurring, necessitating further investigation into control strategies.