AEROSOLS AS A SOURCE OF WIDESPREAD MYCOPLASMA CONTAMINATION OF TISSUE CULTURES

Biosafety Recommendations on the Handling of Animal Cell Cultures

The first steps in tissue culture are dating back to the beginning of the nineteenth century when biosafety measures did not yet exist. Later on, animal cell culture became essential for scientific research, diagnosis and biotechnological activities. Along with this development, biosafety concerns have emerged pointing to the risks for human health and in a lesser extent for the environment associated to the handling of animal cell cultures. The management of these risks requires a thorough risk assessment of both the cell cultures and the type of manipulation prior the start of any activity. It involves a case-by-case evaluation of both the intrinsic properties of the cell culture genetically modified or not and the probability that it may inadvertently or intentionally become infected with pathogenic micro-organisms. The latter hazard is predominant when adventitious contaminants are pathogenic or have a better capacity to persist in unfavourable conditions. Consequently, most of the containment measures primarily aim at protecting cells from adventitious contamination. Cell cultures known to harbour an infectious etiologic agent should be manipulated in compliance with containment measures recommended for the etiologic agent itself. The manipulation of cell cultures from human or primate origin necessitates the use of a type II biosafety cabinet. The scope of this chapter is to highlight aspects relevant for the risk assessment and to summarize the main biosafety recommendations and the recent technological advances allowing a mitigation of the risk for the handling of animal cell cultures.

Prevention and detection of Mycoplasma contamination in cell culture

One of the main problems in cell culture is mycoplasma infection. It can extensively affect cell physiology and metabolism. As the applications of cell culture increase in research, industrial production and cell therapy, more concerns about mycoplasma contamination and detection will arise. This review will provide valuable information about: 1. the ways in which cells are contaminated and the frequency and source of mycoplasma species in cell culture; 2. the ways to prevent mycoplasma contamination in cell culture; 3. the importance of mycoplasma tests in cell culture; 4. different methods to identify mycoplasma contamination; 5. the consequences of mycoplasma contamination in cell culture and 6. available methods to eliminate mycoplasma contamination. Awareness about the sources of mycoplasma and pursuing aseptic techniques in cell culture along with reliable detection methods of mycoplasma contamination can provide an appropriate situation to prevent mycoplasma contamination in cell culture.

Presence of the arginine dihydrolase pathway in Mycoplasma

Barile, Michael F. (Division of Biologics Standards, National Institutes of Health, Bethesda, Md.), Robert T. Schimke, and Donald B. Riggs. Presence of the arginine dihydrolase pathway in Mycoplasma. J. Bacteriol. 91:189-192. 1966.-The presence of the arginine dihydrolase pathway was examined in 61 Mycoplasma strains representing at least 18 Mycoplasma species isolated from nine different sources: human, bovine, avian, murine, swine, goat, canine, sewage, and tissue cell culture origin. Some species were represented by only one or two strains. Different strains of the same species gave the same results. Ten species (56%) were positive. Many nonpathogenic Mycoplasma species (M. hominis, type 1 and 2, M. fermentans, M. salivarium, and M. gallinarum) were positive, whereas most pathogenic species (M. pneumoniae, M. gallisepticum, M. neurolyticum, and M. hyorhinis) were negative. The presence of arginine dihydrolase activity among Mycoplasma species may prove to be useful for purposes of identification and classification.

Control of Pleuropneumonia-like Organisms in Cell Culture

Mammalian cell culture systems were maintained free of mycoplasmas by using a 3-day agar plate test as a weekly routine to monitor the conditions of the cells. If contaminated cell cultures were found, they were discarded and replaced from a pleuropneumonia-like organism (PPLO)-free cell bank. PPLO-free lines were established by treatment with various antibiotics. The KB cell line was freed of mycoplasmas by treatment for 1 week with a mixture of chlortetracycline, kanamycin, and chloramphenicol. L-929 cells were cleared of contamination with either spectinomycin or tylosin, and a synovial cell line was cleared with lincomycin or tylosin. Each cell line, after eradication of the contaminant, was stored in liquid nitrogen. A number of agents were tested to determine minimal inhibitory concentration against three known and three unidentified mycoplasmas. Chlortetracycline and tetracycline were found to be highly active against all strains, whereas tylosin, spectinomycin, and lincomycin, though less active, were equally useful because of their low toxicity against cells. Kanamycin was highly active against three strains, but inactive at high levels against the KB cell contaminants. A disc plate test was used to check isolated cell contaminants for sensitivity to various agents.

Isolation of Acholeplasma laidlawii from commercial, serum-free tissue culture medium and studies on its survival and detection

This report documents the first isolation of Acholeplasma laidlawii from a commercial lot of serum-free Dulbecco basal medium. Experimental studies demonstrated survival of the organism for at least 1 year depending on the concentration of the contaminating organism as well as pH and temperature of storage of the serum-free medium. A comparison of isolation methods showed that concentration by filtration through 220-nm membrane filters and testing the filters for mycoplasma recovery, especially when using phenol red-diphasic Hayflick medium, was both sensitive and practical for the average laboratory.

A simple method for detecting mycoplasma infection of cell cultures

This paper describes the overnight Giemsa staining method for detecting mycoplasma infection of cell cultures. This simple method requires no special equipment and has practical application in most cell culture laboratories. This technique has been used conveniently to monitor stock cell cultures for mycoplasma infection over a 12-month period avoiding any contamination.

Mycoplasmas and cell cultures

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New assay procedure for separation of mycoplasmas from virus pools and tissue culture systems

Presence of mycoplasma organisms in tissue culture systems and virus pools was detected by titration of the contaminated material on agarose-suspended BHK21/13S cells. The use of this method permitted isolation of mycoplasmas which could not be detected by standard assay methods. Mycoplasma colonies at concentrations ranging from 10(4) to 10(6) colony-forming units/ml in agarose-BHK21/13S media could be distinguished from virus plaques, and the two populations of microorganisms could be easily disassociated either by electron microscopy or by biological methods. All isolated mycoplasmas were identified in growth inhibition tests as belonging to the GDL group. The growth inhibition test on agarose-BHK21/13S cell suspension plates could also be applied directly to those strains which could not be isolated by standard assay procedures.

Suppression of Rous Sarcoma Virus Growth in Tissue Cultures by Mycoplasma orale

Somerson, Norman L. (National Institute of Allergy and Infectious Diseases, Bethesda, Md.), and M. K. Cook . Suppression of Rous sarcoma virus growth in tissue cultures by Mycoplasma orale . J. Bacteriol. 90: 534–540. 1965.—An agent which produced cell destruction in human diploid and chick-embryo fibroblasts was isolated from WI-26 strain of human diploid fibroblasts and shown to be a mycoplasma. The multiplication of Rous sarcoma virus (RSV) and Rous associated virus (RAV) was inhibited in WI-26, WI-38, and chick-embryo fibroblasts infected with this mycoplasma. The mycoplasma isolate, designated strain 941, reacted strongly in the complement-fixation test with antiserum to Mycoplasma orale CH19299, an isolate obtained from the human oral cavity. The cytopathic effect of mycoplasma strain 941 could be eliminated by growing the mycoplasma on an artificial agar medium before inoculation into chick-embryo fibroblasts. Serial passage in chick-embryo fibroblasts restored the cytopathogenicity of the agar-grown mycoplasma. However, growth of RSV and RAV was inhibited by both the tissue culture-grown and the agar-grown 941 strain, and also by the CH19299 strain which did not produce any cytopathic effect.