Elimination of mycoplasmas

Most contaminated cultures should be autoclaved to prevent spread of the mycoplasmas. Occasionally, a very important cell strain may become or be found to be contaminated, and it has been reported that kanamycin (0.1 mg/ml) prevents the growth (Fogh and Hacker, 1960) and tylocine (6.0 /rg/ml) is also reported to be effective against PPLO (Gibco Biocult catalogue Appendix 3). Boehringer 

Mannheim market a combination of two antibiotics for sequential use (BM cycle) and quinolones such as ciprofloxacin (Schmitt et al., 1988) and MRA (available from Flow Laboratories for use at 0.5-10 fig/ml) are very effective at eliminating mycoplasma. The quinolones inhibit the prokaryotic DNA gyrase. 

Mycoplasma can be eliminated from cell culture by treatment with immune serum (Pollock and Kenny, 1963) and passage through an animal is often effective in removing mycoplasma from tumour producing cell lines. 

Since the possibility was recognised that bovine serum may be contaminated with several viruses (e.g. bovine herpesvirus and parainfluenza 3-virus) sera are now routinely tested by the manufacturer. The effectiveness of this screening has, however, been questioned (Kniazeff, 1973), and the use of serum-free media ( 5.8) is recommended as the only secure method of eliminating serum-borne viral contamination cytopathic effect. The problem is more serious, however, if no cytopathic effect is seen but the virus continues to replicate at a slow rate or in a few cells only. Thus primary cells from children with Burkitt s lymphoma show no signs of Epstein-Barr virus (EBV) until several passages when a few cells show positive immunofluorescence (Henle and Henle, 1966). 

Cells transformed with the papovaviruses polyoma (e.g. BHK 21PyY, Dulbecco, 1968) and SV40 (e.g. SV28, Wiblin and Macpher-son, 1972) show the presence of tumour antigen by immunofluorescence, but this is not harmful it rather results in an increased growth potential and consequent disregard for neighbouring cells. 

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Mowles JM (1988) The use of Ciprofloxacin for the elimination of mycoplasmas from naturally infected cell lines. Cyto-technology 1 355-358. 

Van Diggelen OP, Shin S Phillips DM (1977) Reduction in cellular tumour-genicity after mycoplasma infection and elimination of mycoplasma from infected cultures by passage in nude mice. Cancer Research 37 2680-2687. 

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