Role of genetic resistance in invasive pneumococcal infection: Identification and study of susceptibility and resistance in inbred mouse strains

From a panel of nine inbred mice strains intranasally infected with Strepto coccus pneumoniae type 2 strain, BALB/c mice were resistant and CBA/Ca and SJL mice were susceptible to infection. Further investigation revealed that BALB/c mice were able to prevent proliferation of pneumococci in the lungs and blood, whereas CBA/Ca mice showed no bacterial clearance. Rapidly incr easing numbers of bacteria in the blood was a feature of CBA/Ca but not BAL B/c mice. In the lungs, BALB/c mice recruited significantly more neutrophil s than CBA/Ca mice at 12 and 24 h postinfection. Inflammatory lesions in BA LB/c mice were visible much earlier than in CBA/Ca mice, and there was a gr eater cellular infiltration into the lung tissue of BALB/c mice at the earl ier time points. Our data suggest that resistance or susceptibility to intr anasal pneumococci may have an association with recruitment and/or function of neutrophils.