A Comparative Study on the Resistance of Protein A-deficient Mutant and Cowan I Strains of Staphylococcus aureus to Hydrogen Peroxide in Vitro
A protein A-deficient strain, HL-87, was isolated from Staphylococcus aureus (S. aureus) Cowan I strain possessing protein A. Using the two strains, Cowan I and HL-87, the resistance to the bactericidal effect of hydrogen peroxide (H202) in vitro was investigated. It has been revealed that the viability of HL-87 strain was significantly lower than that of Cowan I strain after incubation in the presence of H202. When the catalase activity in both strains was assayed, HL-87 strain showed higher activity than Cowan I strain did, indicating that the difference in the resistance to in vitro H202 between the two strains did not depend on their catalase activity. These results suggested that protein A in the cell walls of Cowan I strain was directly related to the protection from the H202-bactericidal effect.