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Synergistic hemolysis associated with coagulase-negative staphylococci isolated from bovine mammary glands
1Mastitis Research Laboratory, Louisiana State University Agricultural Center, Homer 71040.
Abstract:
A total of 353 coagulase-negative staphylococcus (CNS) isolates from infected bovine mammary glands were tested for cytolysin production by using the synergistic hemolysin assay (SHA). Overall, 34.6% of CNS isolates were SHA positive. Human-associated, coagulase-negative staphylococcal species contained the greatest number of SHA-positive strains. Milk leukocyte levels expressed as somatic cell counts (SCC) were elevated with SHA-positive Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus warneri strains. Elevated SCC levels were associated with strains of Staphylococcus hyicus and Staphylococcus chromogenes. However, no difference in SCC levels was observed between SHA-positive and SHA-negative strains. Results indicated that the SHA was a sensitive test for the detection of cytolysin-producing CNS.
Insights
Coagulase-negative staphylococci (CNS) from bovine mastitis can produce cytolysins, detected by the synergistic hemolysin assay (SHA). Certain CNS species, particularly human-associated ones, showed higher cytolysin production, impacting milk somatic cell counts.
Area of Science:
- Veterinary Microbiology
- Bovine Mastitis Pathogenesis
- Bacterial Toxinology
Background:
- Coagulase-negative staphylococci (CNS) are significant opportunistic pathogens in bovine mastitis.
- Cytolysin production by CNS may contribute to mammary gland inflammation and infection severity.
- Accurate detection of cytolysin-producing CNS is crucial for understanding pathogenesis.
Purpose of the Study:
- To evaluate the prevalence of cytolysin production in CNS isolates from infected bovine mammary glands.
- To assess the correlation between cytolysin production and milk somatic cell counts (SCC).
- To determine the efficacy of the synergistic hemolysin assay (SHA) for detecting cytolysin-producing CNS.
Main Methods:
- A total of 353 CNS isolates from bovine mammary glands were collected.
- Synergistic hemolysin assay (SHA) was employed to detect cytolysin production.
- Milk somatic cell counts (SCC) were analyzed in relation to CNS isolates and their cytolysin production.
Main Results:
- 34.6% of the tested CNS isolates were positive for cytolysin production via SHA.
- Human-associated CNS species exhibited the highest prevalence of SHA-positive strains.
- Elevated SCC levels were associated with specific SHA-positive CNS strains (S. epidermidis, S. hominis, S. warneri, S. hyicus, S. chromogenes), though not universally between SHA-positive and negative strains.
Conclusions:
- The synergistic hemolysin assay (SHA) is a sensitive method for detecting cytolysin-producing CNS.
- Cytolysin-producing CNS, particularly from human-associated species, are present in bovine mastitis.
- The relationship between cytolysin production and SCC elevation is complex and strain-dependent.