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Cell surface hydrophobicity and charge of Staphylococcus aureus and coagulase-negative staphylococci from bovine
Abstract:
The effects of seven growth media on cell surface hydrophobicity of a collection of Staphylococcus aureus and coagulase-negative staphylococci isolated from bovine mastitis were compared in the salt-aggregation test. Thirty-three per cent of Staph. aureus strains showed extremely high cell surface hydrophobicity (auto-aggregated) and 28% were moderately hydrophobic while 26% were hydrophilic after growth on horse blood agar at 37 degrees C for 18 h. There were great variations in the proportion and degree of the hydrophobicity depending on the medium used. Cultivations on/in capsule-inducing media caused a shift from a high to a low degree of hydrophobicity, although a microscopically detectable capsule or slime layer was seen in only one strain. This strain and encapsulated reference strains had a hydrophilic cell surface and migrated faster in free zone electrophoresis than cells of unencapsulated strains. Cells of strains grown on staphylococcus medium 110 agar migrated faster than those grown on horse blood agar regardless of their capsule production. Coagulase-negative staphylococci showed uniformly hydrophilic cell surface after cultivation on horse blood agar, but not when grown in tryptic soy broth or proteose peptone broth. It was concluded that most of the Staph. aureus strains from bovine mastitis under a variety of growth conditions in stationary phase culture constantly expressed hydrophobic cell surface.
Insights
Growth media significantly impact Staphylococcus aureus cell surface hydrophobicity in bovine mastitis isolates. Most Staphylococcus aureus strains consistently showed hydrophobic surfaces, regardless of growth conditions.
Area of Science:
- Microbiology
- Veterinary Science
- Biochemistry
Background:
- Bovine mastitis is a significant economic concern in the dairy industry, often caused by Staphylococcus aureus.
- Staphylococcus aureus and coagulase-negative staphylococci are common pathogens in bovine mastitis.
- Cell surface hydrophobicity plays a crucial role in bacterial adhesion and pathogenesis.
Purpose of the Study:
- To investigate the influence of different growth media on the cell surface hydrophobicity of Staphylococcus aureus and coagulase-negative staphylococci from bovine mastitis.
- To determine the variability of hydrophobicity based on growth conditions.
- To correlate cell surface properties with electrophoretic mobility.
Main Methods:
- Salt-aggregation test to assess cell surface hydrophobicity.
- Cultivation of bacterial strains on seven different growth media.
- Free zone electrophoresis to measure cell migration and electrophoretic mobility.
- Microscopic examination for capsule or slime layer presence.
Main Results:
- Significant variations in hydrophobicity were observed depending on the growth medium used.
- Thirty-three percent of Staphylococcus aureus strains exhibited extremely high hydrophobicity, while 28% were moderately hydrophobic and 26% hydrophilic on horse blood agar.
- Growth on capsule-inducing media shifted hydrophobicity from high to low, though capsules were rarely observed.
- Encapsulated strains showed hydrophilic surfaces and faster electrophoretic migration.
- Staphylococcus aureus grown on Staphylococcus medium 110 agar exhibited faster migration than those on horse blood agar.
- Coagulase-negative staphylococci generally displayed hydrophilic surfaces on horse blood agar but varied on other media.
Conclusions:
- Most Staphylococcus aureus strains from bovine mastitis consistently express a hydrophobic cell surface in stationary phase culture, irrespective of growth conditions.
- Growth medium composition is a critical factor influencing bacterial cell surface properties.
- Understanding these variations is essential for developing effective control strategies against bovine mastitis.