MODEL OF STREPTOCOCCUS-PNEUMONIAE MENINGITIS IN ADULT-RATS

The purpose of this study was to develop a model of bacterial meningit is in young adult rats for assessing the efficacy of antimicrobial age nts, Sixty 200- to 300-g male Sprague Dawley CD rats were inoculated i ntracisternally with 5.78 log(10) CFU of a clinical isolate of Strepto coccus pneumoniae in 5% hog gastric mucin. Inoculated rats mere assign ed to six groups containing 10 animals each, Group-1 rats served as co ntrols and did not receive antibiotics, Rats of groups 2 to 4 received (subcutaneously every 12 h) cefotaxime (25, 6.25, and 1.56 mg/kg of b ody weight respectively). Rats of groups 5 and 6 received ampicillin ( 50 and 12.5 mg/kg respectively) and gentamicin (2.0 and 0.5 mg/kg resp ectively), Five additional Sprague Dawley CD rats were inoculated with only gastric hog mucin and were assigned to group 7. At postinoculati on day 4 all animals were euthanized. Cerebral spinal fluid was collec ted for culturing, Brains were harvested for histologic examination an d culturing, Untreated, infected control (group-1) animals were cultur e-positive for S. pneumoniae in the brain and cerebral spinal fluid. O f the antibiotic regimens evaluated, only cefotaxime (25 mg/kg) eradic ated bacteria from the cerebral spinal fluid and brain, Cefotaxime at 25 or 6.25 mg/kg significantly (P less than or equal to 0.05) decrease d the bacterial burden of S. pneumoniae, whereas cefotaxime at 1.56 mg /kg and ampicillin/gentamicin combinations did not, There was histopat hological evidence of subacute meningitis in infected rats, No meningi tis was observed in rats receiving 25 mg of cefotaxime/kg. This model demonstrates the ability to induce bacterial meningitis with S. pneumo niae in adult rats and the ability to clear infection in 90 to 100% of the animals by administration of cefotaxime at dosages of 6.25 and 25 mg/kg given subcutaneously every 12 h.