Physico-chemical properties of Staphylococcus epidermidis and Staphylococcus saprophyticus as studied by aqueous polymer two-phase systems.

The physico-chemical surface characteristics, i.e. charge, charge density and hydrophobic interaction liability, of two strains of Staphylococcus saprophyticus were studied by the partition in aqueous polymer two-phase systems and compared to that of three strains of Staphylococcus epidermidis. The two strains of S. saprophyticus, one with and one without sheep erythrocyte agglutinating ability, were found to be negatively charged at pH 7.2 and 5.5, but exhibited a charge reduction at the lower pH. The three strains of S. epidermidis were found to carry a lower charge and lost relatively more charge at pH reduction than did S. saprophyticus. All strains of both bacterial species had a poor hydrophobic interaction liability. Incubation of one strain of S. saprophyticus with specific immune serum did not influence on hydrophobicity, but reduced charge drastically. Charge reduction was found to be associated with an immune serum fraction containing IgG and IgA.