Genetic control of susceptibility to group A streptococcal infection

The influence of genetic background on the ability to control infection with group A strepto-cocci was investigated in different inbred strains of mice. Whereas BALB/c, C57BL/10, and DBA/2 mice were the most resistant strains, with lower bacteria loads and higher survival times, C3H/HeN and CBA/J mice exhibited substantially higher bacterial growth and 100% mortality. Differences in susceptibility were not dependent on the inoculum size. Resistance was influenced by sex, with males being much more susceptible than females. B cell – and T cell–deficient mice from the resistant background were as resistant to infection as were im-munocompetent mice, which suggests that the effector mechanisms are independent of adap-tive immunity. These results demonstrate for the first time the influence of genetic background and sex on susceptibility to infection with Streptococcus pyogenes in mice. The use of this mouse model of group A streptococcal infection will allow for a better definition of parameters involved in the outcome of the disease. Group A streptococci (GAS) are among the most common human pathogens, with extremely variable clinical manifesta-tions ranging from self-limited infection on the skin or mucosa