Tissue culture contamination with nontuberculous mycobacteria.

Abstract

Contamination of cultured eukaryotic cells with unwanted viruses, myco­plasmas, protozoa, fungi, and bacteria is a major problem for those who use suchcells in biologic and biochemical research (2). Among the many microorganismswhich have been isolated as cell culture contaminants, nontuberculous mycobac­teria have not been described previously. We recently encountered these orga­nisms in various lymphoblastoid cell lines such as CEM and RAJI as well as indiploid human fibroblasts and monkey kidney lines such as VERO. The presenceof contaminants had been suspected because of low virus yields.Gram stains of culture fluids bathing the tissue cultures, such as RPMI 1640or Eagle's basal medium with 10% bovine serum (Grand Island Biological Co.,Madison, Wis.) showed pleomorphic gram-positiverods resembling corynebacteria.There was, however, no gross alteration of the tissue culture and cells and no tur­bidity of the medium. Subcultures to media which would normally supportgrowth of corynebacteria, i.e., aerobic Tryptic Soy Agar (Difco Laboratories, De­troit, Mich.) with 5% sheep blood agar, Columbia Broth (Difco), Brain HeartInfusion (Difco), and Sabouraud Dextose Agar (Difco), did not reveal growth.Light growth consisting of slight flocculation near the top of the tube was occa­sionally seen in Fluid Thioglycollate Medium (Difco) after two weeks' incubation at