The Interaction Of Staphylococci Grown In Vivo And In Vitro With PolyMorphonuclear Leucocytes

The resistance to phagocytic uptake and intracellular killing of staphylococci grown in vivo and in vitro has been compared. Strains O (original) and P (rabbit passaged) grown in vitro and strain V (isolated directly from rabbits infected with strain P) did not differ in their susceptibility to ingestion by polymorphs. Intracellular killing was most marked in the 1st hr after phagocytosis; survival of strain V was substantially greater than that of strains O and P. This is in agreement with earlier observations on the resistance of these strains to the bactericidins of polymorph lysates. In contrast to behaviour in lysates, strain P was not significantly different from strain O in resistance to phagocytic killing. It is suggested that the virulence difference between strains P and O depends on the properties of the phenotypic form that each assumes in vivo.