INFLUENCE OF PH ON RECOVERY OF MYCOPLASMA FROM THE HUMAN OROPHARYNX.
NAVAL MEDICAL RESEARCH UNIT NO 4 GREAT LAKES ILL
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Recently published data indicate that a pH of 5.5 to 6.5 rather than usual pH 7.8 favors growth of T strain Mycoplasma and at least one classical species, M. salivarium. This information, based on laboratory-adapted cultures, raises the question of whether or not a pH lower than 7.8 would increase the sensitivity of PPLO agar for isolation of mycoplasmas from the human oropharynx. The number of colonies and variety of species from throat swabs of the first 50 patients was compared on pH 5.0, 6.0, 7.0, and 8.0 PPLO agar enriched with 10 horse serum. The recovery of M. pneumoniae from throat swabs of another 50 patients was compared at the above pH levels on PPLO agar containing 20 horse serum and 0.002 methylene blue. Positive cultures in the first group were as follows 78 at pH 5.0, 94 at pH 6.0, 88 at pH 7.0, and 78 at pH 8.0. Highest incidence of M. pharyngis occurred at pH 7.0 and of M. salivarium at pH 5.0 and 6.0. The one M. hominis type 1 isolate grew evenly over the entire range of pH tested. In the second group, a pH of 7.0 and 8.0 was optimal for the recovery of M. pneumoniae. It was concluded that, excepting M. pneumoniae, the human oral mycoplasmas are more frequently isolated on PPLO agar of pH 6.0 and 7.0. Author