Effect of Vacuum Concentration on Survival and Behavior of S. aureus 234

ABSTRACT Staphylococcus aureus 234 population was reduced from 18 × 105 cfu/mL to 31 × 104 cfu/mL after 1:3 vacuum concentration of cow's milk. However, the corresponding figures during concentration of buffalo milk were 20 × 105 cfu/mL and 109 × 104 cfu/mL. The ability to produce enterotoxin B was completely lost in all the five variants (survivors) examined. However, coagulase and Thermonuclease (TNase) activities were only slightly decreased as compared to those of the parent strain. The egg yolk clearing by some variants on Baird Parker agar was delayed by 24 hrs and the colonies were of diffused type. The other activities like phosphatase, gelatin liquefaction, aerobic and anaerobic glucose and mannitol utilization, and hemolysis were not affected in the survivors.