Hayflick et al. (1965) reported that mycoplasma (M.) orale was isolated directly on PPLO agar from the bone marrow samples of patients with acute leukemia, but it has been still unknown whether M. orale has been identified as a pathogen in some kinds of human diseases. However, it has been generally accepted that M. orale does not have a pathogenicity in the human.
In order to determine the significance of the existence of M. orale in the respiratory tract, experiments in the hamster infected with M. orale were performed.
Materials and Methods;
Young hamsters, 3 weeks old, were utilized. A suspension of M. orale strain containing 1.6-107 colony forming unit (CFU) per ml was introduced into the hamster by the inhalation of an aerosol spray. Throat swabs were cultured onto each of two PPLO agar plates at intervals of 2-3 days for up to 42 days after exposure. The hamsters were also sacrificed at intervals of 2 to 3 days. During this time, blood samples were taken for serological studies. Both lungs were removed aseptically for bacteriological and histological studies. For controls, a group of hamsters was infected with M. pneumoniae and a 2nd group was given PPLO broth alone. Then these animals were killed and evaluated by the same methods.
Results;
In the groups infected with M. orale and in those exposed to PPLO broth alone, only one hamster organisms isolated from the nasopharynx or from the lungs for up to 42 days after inoculation.
In the M. orale group minimal histopathologic inflammatory changes including edema in the bronchus observed from 2 to 21 days after infection. In contrast, in the group infected with M. pneumoniae, organisms were present in cultures of the lungs of all of the hamsters in the maximum concentration of 108 CFU per ml during the period of observation. Further findings such as peribronchitis and interstitial pneumonitis were present in this group for up to 28 days.
No significant differences were recognized in the serological and the hematological studies in these three groups.
