Relationship between penicillin and cephalosporin resistance of Streptococcus pneumoniae strains and its inflammatory activity in the experimental model of meningitis

Using a rabbit model of meningitis, we sought to compare the inflammatory activity induced by three pneumococcal strains with different susceptibilities to penicillin and cephalosporins, belonging to the serotypes 3, 6B and 23F at different inoculum sizes. These serotypes are prevalent in Western Europe and are believed to produce a moderate-to-severe cerebrospinal fluid (CSF) inflammatory response. Only minor differences were observed in the inflammatory activity evoked by the three strains in the subarachnoid space, and most were probably related to differences in bacterial counts. Infection by serotype 23F caused secondary bacteremia in all challenged animals. Our findings reinforce the concept that resistant pneumococci are not more virulent, a fact that should be taken into account when evaluating the efficacy of different anti-pneumococcal therapies. However, the frequent induction of secondary bacteremia by the resistant serotype 23F requires further study.