Potentiating effect of Mycoplasma pneumoniae infection on the development of pneumococcal septicemia in hamsters.

Intranasal inoculation of hamsters with Mycoplasma pneumoniae followed by pneumococcus type 1 virulent for mice resulted in a severe pneumococcal septicemia accompanied by high morbidity and mortality. This potentiating effect of M. pneumoniae on the development of pneumococcal septicemia was absent if M. pneumoniae was inoculated after the pneumococci (Diplococcus pneumoniae) or if a temperature-sensitive mutant of M. pneumoniae was used instead. Immunization of hamsters with live M. pneumoniae conferred a substantial protective effect against the development of pneumococcal septicemia when these animals were subjected to subsequent challenge with combined infections of M. pneumoniae and pneumococci. The experimental data suggest that active mycoplasmal multiplication in the respiratory tract before pneumococcal inoculation was essential for potentiation of development of pneumococcal septicemia. The exact mechanism by which mycoplasmal infection potentiates the development of septicemia warrants further investigation.