Pleuropneumonialike organisms in tissue cultures

Of 55 continuous cell lines 32 gave growth of P.P.L.O. whereas 26 primary cell cultures were free from this contamination.Biochemical and serological typing proved that 31 of these 32 P.P.L.O. wereMycoplasma hominis I. One strain was identical with a recently described oralMycoplasma.It was demonstrated that insufficiently rigorous techniques tend to cause spreading of P.P.L.O. in tissue culture laboratories.There was no indication that either the sera or other ingredients of the media used might have introduced this contamination. HeLa cells, however, probably are the source.The minor differences between genital strains propagated in the laboratory, and tissue culture strains, are probably due to differences between the two media.By treatment of a contaminated cell line with serum againstM. hominis I a double infection with P.P.L.O. could be demonstrated. The cells were freed from the remaining P.P.L.O. by treatment with the serum against this strain.Contamination of cell lines withM. hominis I did not affect the growth rate of the wild poliovirus I strains tested, nor that of a Sabin type I strain. M. fermentans grows well in tissue cultures but has no cytopathic effect.M. salivarium cannot be propagated in ordinary tissue cultures unless Fildes extract, which contains catalase, is added. In cultures with this extractM. salivarium has a cytopathic effect.