Asymptomatic infection of adult volunteers with a temperature sensitive mutant of Mycoplasma pneumoniae.

Temperature sensitive mutants of Mycoplasma pneumoniae were developed with the expectation that their temperature sensitive defects would restrict replication in vivo at the temperature of the lower respiratory tract, whereas such defects would not seriously impair replication in the cooler environment of the upper respiratory passages. One such ts mutant, ts-H43, which does not replicate at a temperature of 37 degrees or above, although noninfectious for hamsters, infected each of 16 seronegative adult volunteers when given by the intranasal route. The mutant remained genetically stable throughout the course of infection and stimulated a moderate systemic and local antibody response. The mutant was entirely avirulent for the volunteers but appeared to stimulate resistance to subsequent challenge with partially attenuated wild-type (ts(+)) Mycoplasma pneumoniae.