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Secretion of alpha-hemolysin by bovine mammary isolates of Staphylococcus aureus
K Kenny1, F D Bastida, N L Norcross
1Department of Clinical Sciences, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853.
Abstract:
A total of 262 strains of Staphylococcus aureus isolated from the mammary gland of dairy cows were examined for the production of alpha-hemolysin. Strains were cultured in a liquid medium of casein hydrolysate and yeast extract in an atmosphere of 7% (v/v) CO2 in air. The assay consisted of a dot immunoblotting technique employing bacterial culture supernatants and a mouse monoclonal antibody specific for alpha-hemolysin. Ninety-four percent (247) of 262 strains were positive for alpha-hemolysin by this method, when cultured in the laboratory. This figure is compared with those obtained in previous studies which typically based their results on the hemolytic patterns of isolates on blood agar plates.
Insights
Most Staphylococcus aureus strains from dairy cows produce alpha-hemolysin, a key virulence factor. This study identified a high prevalence of alpha-hemolysin production in bovine mastitis pathogens.
Area of Science:
- Microbiology
- Veterinary Medicine
- Bacterial Pathogenesis
Background:
- Staphylococcus aureus is a significant pathogen causing bovine mastitis.
- Alpha-hemolysin is a toxin produced by S. aureus, contributing to virulence.
- Accurate detection of alpha-hemolysin is crucial for understanding mastitis pathogenesis.
Purpose of the Study:
- To quantify the production of alpha-hemolysin in Staphylococcus aureus strains isolated from dairy cows.
- To evaluate a dot immunoblotting technique for detecting alpha-hemolysin production.
- To compare laboratory-based detection with traditional methods like hemolytic patterns on blood agar.
Main Methods:
- Isolation and culturing of 262 Staphylococcus aureus strains from dairy cow mammary glands.
- Cultivation in a casein hydrolysate and yeast extract liquid medium under 7% CO2.
- Detection of alpha-hemolysin using a dot immunoblotting assay with a specific mouse monoclonal antibody.
Main Results:
- Ninety-four percent (247 out of 262) of the tested S. aureus strains were positive for alpha-hemolysin production.
- The dot immunoblotting technique demonstrated high sensitivity in detecting alpha-hemolysin.
- Results indicate a higher prevalence compared to studies relying solely on blood agar hemolysis.
Conclusions:
- The majority of Staphylococcus aureus strains associated with bovine mastitis possess the genetic capability to produce alpha-hemolysin.
- The dot immunoblotting assay is an effective method for identifying alpha-hemolysin-producing strains.
- Findings highlight the widespread presence of this virulence factor in bovine S. aureus isolates.