Cell cultures must be continuously screened for the presence of mycoplasma because, although these microorganisms sometimes pass unoticed, they may cause chromosomic alterations and interfere with viral replication, antibody and interferon production etc. The International Organization for Mycoplasmology (IOM) recommends the isolation and identification of mycoplasma with a view to the detection of the origin of the infection and the improvement of the quality of the cultures. In this paper, 37 samples belonging to 27 cell lines contaminated with mycoplasma were assayed by the growth inhibition test. It is known that Mycoplasma orale is the most common human mycoplasma contaminant of cell cultures, the major vehicle of contamination being mouth pippeting, while commercial bovine serum in the main source for Mycoplasma arginini and Acholeplasma laidlawii. M. arginini was found in 18 (48.65%) of the cell samples tested, A. laidlawii in 15 (40.55%), and M. orale in two (5.40%). Two other samples could not be identified by the antisera used (antisera against M. arginini, M. orale, Mycoplasma hyorhinis and A. laidlawii) their characteristics being "fried egg" colonies, digitonine sensitivity, Dienes stained, positive glucose catabolism, negative arginini hydrolysis, and negative tetrazolium reduction. No more than one type of mycoplasma was found in each cell culture. In the light of the results of the study, it is suggested that: a) cell cultures should be tested for mycoplasma on a routine basis; b) microbial control techniques be unproved; c) mouth pippeting be abolished; d) serum and cell culture media components purchased be of certified quality; e) the presence of mycoplasma when cell lines are exchanged among institutions be investigated; f) data obtained when mycoplasma infected cell cultures are used be carefully evaluated.
Cells, cultured; Mycoplasma; Bacterial typing technics
