Quantitative Detection of Mycoplasma DNA Using Competitive PCR

Mycoplasma are free-living pleomorphic prokaryotes that can pass through regular bacteriological filters. These organisms have a small genome with low G + C content, and lack the rigid peptidoglycan cell wall of eubacteria. There are more than 80 species known to date, the major cell culture contaminants of human, bovine, or porcine origin being: Mycoplasma orale, M. fermentants, M. hyorhinus, M. arginini, M. salivarium, and Acholeplasma laidlawii (McGarrity et al., 1985). More than 15–30% of all the cell lines used are contaminated with mycoplasma species (Mowles et al., 1988; Gignac et al., 1991). Mycoplasma grow in the cell culture supernatant and are attached to the extracellular surface of the cell membranes. The growth of these microorganisms may not necessarily destroy the cells but produces significant changes in the culture medium composition, which leads to alterations in the host cell metabolism, thus rendering infected cells unacceptable for use in any research or diagnostic procedure. Cell culture infections by various mycoplasma species, as well as their effects, are well documented. Some of the effects of mycoplasma on cell cultures include induction or suppression of enzymes and cytokines, alteration of cell surface antigenicity, interference with viral expression, and induction of chromosomal breaks. A few mycoplasma species have also been reported to produce transformation of cells in culture (Macpherson and Russel, 1966).