BACTERICIDAL ACTIVITY OF CEFOTAXIME, DESACETYLCEFOTAXIME, RIFAMPIN, AND VARIOUS COMBINATIONS TESTED AT CEREBROSPINAL-FLUID LEVELS AGAINST PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE

Penicillin resistance is increasingly prevalent amongst clinical isola tes of Streptococcus pneumoniae. Recently, isolates resistant to the e xtended-spectrum cephalosporins have also begun to emerge, and combina tion therapy may be necessary for infection with such organisms. We ha ve studied the activity of cefotaxime, ceftriaxone, ceftazidime, rifam pin, chloramphenicol, and vancomycin against 10 S. pneumoniae strains with penicillin minimum inhibitory concentrations (MICs) ranging from 0.03-8 mu g/ml. The bactericidal activity of cefotaxime, desacetylcefo taxime, rifampin, and combinations of these agents (cerebrospinal flui d levels) against these isolates was determined. Elevated MICs to peni cillin were associated with generally twofold lower cefotaxime MICs. A ll strains remained susceptible to vancomycin and rifampin. The bacter icidal activity of cefotaxime with or without desacetylcefotaxime was reduced by the addition of rifampin. Pneumococcal isolates with penici llin MICs of less than or equal to 1 mu g/ml were slowly killed by cef otaxime alone or with desacetycefotaxime. At present, there is little evidence to support the addition of rifampin to cefotaxime for therapy of meningitis.