Cell culture models as ancillary tools in the isolation and characterization of mycoplasmas

Since the late 1960s, there have been an increasing number of reports describing the isolation and identification of fastidious strains of Mycoplasma hyorhinis in cell cultures but not in conventional mycoplasma media, i.e., agar and broth. The application of those techniques normally used in studying viruses, i.e., infection of cell cultures coupled with the subsequent use of immunological and biological test procedures, has provided a reliable alternative procedure for M. hyorhinis detection. Major isolation surveys have revealed that as many as 60 to 80% of M. hyorhinis isolates from contaminated tissue cultures failed to grow in agar medium. Efforts to elucidate the mechanisms involved in failure of the cell culture-derived M. hyorhinis strain to grow in standard cell-free mycoplasma media are ongoing. Initial data indicated that extracts prepared from tissue cultures (BHK 21) and incorporated in Macpherson's broth and agar medium would permit growth of fastidious strains. Moreover, it appears that these strains are particularly sensitive to inhibition by yeast products often found in mycoplasma media. While M. hyorhinis appears to be unique with respect to its sensitivity to medium components, these fastidious strains are isolated with such frequency that the routine use of an indicator cell system is strongly recommended.