Workshop I: Mycoplasma Contamination and Infection of Cell Cultures

K. Yamamoto reviewed the many different procedures which have been employed in attempting to eliminate mycoplasmas from contaminated cell cultures. These have included antibiotics (tetracyclines, kanamycin, chloramphenicol, novobiocin, tylosin, and gentamicin). In addition, surface-active compounds such as triton-X or SPS, gold salts, photodynamic inactivation, and hyperimmune sera have been utilized. Unfortunately, failures have been reported for each of these procedures. Dr. Yamamoto re-explored the effectiveness of antibiotics using four randomly selected strains of M. orale (designated I, J, M, and V). Each of the four strains was highly resistant to gentamicin and tylosin and less resistant to josamycin and minocycline. The V strain of M. orale was subsequently selected for treatment using several regimens including incubation with minocycline alone and in combination with antiserum and complement. M. orale was successfully eliminated in only one instance, viz., when mycoplasma-infected VERO cells were treated simultaneously with minocycline (2 itg/ml), antiserum, and complement. During the treatment period monolayers were left undisturbed and the medium was replaced at twoto three-day intervals. The effectiveness of the procedure was confirmed using five other cell lines. Dr. Yamamoto pointed out that this was a unique situation since cultures are rarely freed of mycoplasmas by antibiotic treatment. He cautioned that one should continue to consider prevention as the most effective approach to quality control. However, in instances in which the culture is extremely valuable, such an effort might be worthwhile.