DIFFERENTIATION OF MYCOPLASMA-HYOPNEUMONIAE, MYCOPLASMA-FLOCCULARE, AND M-HYORHINIS ON THE BASIS OF AMPLIFICATION OF A 16S RIBOSOMAL-RNA GENE SEQUENCE

To differentiate mycoplasma hyopneumoniae, the cause of mycoplasmal pn eumonia in pigs, from M flocculare and M hyorhinis, an assay, using th e polymerase chain reaction to amplify a segment of the 16S rRNA gene sequence, was developed, The assay was found to be useful for identifi cation of field isolates, as well as for identification of laboratory- adapted strains. Amplification of DNA from M hyopneumoniae and M flocc ulare resulted in products of 200 and 400 base pairs, respectively. Th e DNA from M hyorhinis was not amplified. The assay was sensitive enou gh to detect as little as 1,000 genome equivalents of M hyopneumoniae and M flocculare DNA. Sensitivity was increased 100-fold by increasing the concentration of magnesium ion in the reaction buffer from 2 to 4 mM; however, DNA from M hyorhinis was also amplified under these cond itions. The DNA from several walled bacteria and from other mycoplasma s was also tested, but none of these DNA samples was amplified, sugges ting that the assay was specific for porcine mycoplasmas.