title: Meningitis due to Haemophilus influenzae type b resistant to both ampicillin and chloramphenicol.
abstract: A strain of Haemophilus influenzae type b with considerable resistant to both ampicillin and chloramphenicol was recovered from a South Dakota child with meningitis. There was an initial lack of response to conventional doses but the child improved after a brief period of 200 mg/kg/day of chloramphenicol. The organism showed in vitro resistance to ampicillin, carbenicillin, tetracycline, and chloramphenicol (for each antibiotic the minimal inhibitory concentration (MIC) was 8 micrograms/ml or greater with a bacterial challenge of 10(5) colony-forming units (CFU)/ml), but it was sensitive to both streptomycin and rifampin (MIC 1.6 micrograms/ml, respectively). Isobolograms constructed from the results of testing various concentrations of ampicillin and chloramphenicol showed additive effects with high bacterial inocula (10(5) or 10(7) CFU/ml), but antagonism with low inocula (10(2) or 10(4) CFU/ml).
mesh_terms: D000667:Ampicillin / Q000494:pharmacology*; D002701:Chloramphenicol / Q000494:pharmacology*; D006193:Haemophilus influenzae / Q000187:drug effects*; D006801:Humans; D007223:Infant; D008297:Male; D008583:Meningitis, Haemophilus / Q000188:drug therapy*; D010403:Penicillin Resistance
chemical_list: D002701:Chloramphenicol; D000667:Ampicillin