Relationship between S. aureus gene pattern and dairy herd mastitis prevalence

Area of Science:

• Veterinary Microbiology
• Bacterial Genetics
• Dairy Science

Background:

• Staphylococcus aureus is a major cause of mastitis in dairy cattle.
• Understanding the genetic basis of S. aureus virulence is crucial for effective control strategies.
• Microarray technology offers a high-throughput method for analyzing bacterial virulence genes.

Purpose of the Study:

• To investigate the relationship between the genetic patterns of Staphylococcus aureus isolates and their prevalence in dairy herds.
• To assess the utility of DNA microarray technology for characterizing S. aureus virulence factors in a dairy setting.

Main Methods:

• Genotyping of 33 Staphylococcus aureus isolates from 11 dairy herds using a 157-gene diagnostic DNA microarray.
• Analysis of virulence gene presence/absence and agr allele types.
• Comparison of genetic data with herd-specific mastitis prevalence data.

Main Results:

• Only 19 genes were conserved across all isolates, including those for leukocidin, haemolysins, and enterotoxin X.
• Most antimicrobial resistance genes were absent, except for tetracycline resistance.
• Agr type II was significantly associated with the most prevalent and widespread S. aureus isolates.
• Several agr alleles were not identified in the studied isolates.

Conclusions:

• Microarray analysis is a valuable tool for assessing S. aureus virulence characteristics in dairy herds.
• Specific Staphylococcus aureus genetic profiles are associated with mastitis prevalence and dissemination.
• Agr type II may play a role in the high prevalence of S. aureus mastitis in dairy farms.