Colistin Sulphate as a Substitute of Thallium Acetate in Culture Media for Isolation of Mycoplasma from Cattle Diseased by Mycoplasmosis

Mycoplasmas cause several diseases in cattle as pneumonia in calves and mastitis in cows and also reproductive disorders, abortions, arthritis and conjunctivitis. The difficulty of culturing mycoplasmas in vitro is a major obstacle to research and laboratory diagnosis of these fastidious organisms. A total of 120 preputial swabs, 70 vaginal swabs and 65 milk samples were collected from cattle at several farms (in which mycoplasma infection was suspected) suffering from mastitis and/or reproductive disorders and artificial insemination centers for isolation of Mycoplasma and Ureaplasma, the recovery rates of Mycoplasma and Ureaplasma from the prepuce of bulls were (12.5% and 6.6% respectively) in addition to the isolation rate from vagina of cows were (5.7% and 1.4% respectively) while in milk the isolation rate of Mycoplasma was 3% and Ureaplasma was not isolated from milk samples, Mycoplasma bovigentalium was the most frequent species isolated (46.7 %) followed by Ureaplasma diversum (30%) and Mycoplasma bovis (23.3%). Thallium acetate is commonly used in the laboratories as a selective element against Gram-negative bacteria in selective media for the detection of mollicutes. Thallium acetate is enormously toxic and because it is not biodegradable its accumulation in the environment presents a very serious problem also Ureaplasma species and some mycoplasmas are very sensitive to thallium acetate and must be omitted from the media. The results of analysis of tests with six mycoplasma species are presented here (Mycoplasma bovis, Mycoplasma bovigentalium, Mycoplasma arginini, Mycoplasma canis, Mycoplasma bovirhinis and Ureaplasma diversum). The medium containing colistin sulphate appeared to be a useful substitute of thallium acetate for the detection and culture of the species tested in these experiments.