FIG. 4.

The Sca2 mutant displays reduced virulence in a guinea pig model. (A) Five guinea pigs were inoculated with either the congenic parental R. rickettsii strain (R), the mutant strain 9-3 (R 9-3), the Sca2 mutant 9-7 (R 9-7), or formalin-fixed R. rickettsii (R fixed) or were sham infected with K36 buffer alone (Buffer Only). Rectal temperatures were taken daily for 14 days beginning the day of inoculation. The error bars represent standard errors of the mean from 5 individual animals. (B) Sera collected at 30 days postinfection were used to determine anti-R. rickettsii titers by microimmunofluorescence. Bars indicate the means ± standard errors of the means.