Relationship between some Staphylococcus aureus pathogenic factors and growth rates and somatic cell counts

Area of Science:

• Veterinary Microbiology
• Bacterial Pathogenesis
• Dairy Herd Health

Background:

• Staphylococcus aureus causes udder infections in dairy cows, with virulence factors influencing disease severity.
• Understanding the genetic basis of Staph. aureus pathogenicity is crucial for managing intra-mammary infections (IMI).

Purpose of the Study:

• To investigate the association between the genetic polymorphism of coagulase (coa), protein A (spa), collagen-binding protein (cna), and fibrinogen-binding protein (efb) genes in Staph. aureus.
• To determine the impact of these genetic variations on somatic cell count (SCC) and bacterial growth rate in dairy cows.

Main Methods:

• Analyzed 50 Staph. aureus isolates from 13 dairy herds across seven provinces.
• Examined polymorphisms in coa, spa, cna, and efb genes.
• Correlated genetic profiles with SCC and in vitro growth rates.

Main Results:

• The cna gene was infrequent, while the efb gene was highly prevalent, suggesting a role in epithelial adhesion.
• spa gene polymorphism significantly correlated with inflammatory response and growth rate, differing from human isolate patterns.
• Specific clusters (VI and VII) exhibited higher growth rates and lower SCC, indicating potential for herd dissemination.
• Cluster V isolates were prevalent and suggested to have increased invasiveness despite a stronger inflammatory response.

Conclusions:

• Genetic profiling of Staph. aureus provides insights into virulence and herd epidemiology.
• Isolates with faster growth and reduced inflammatory response may spread more readily within dairy herds.
• The proposed genomic method is a practical tool for diagnostic labs to study Staph. aureus IMI epidemiology.