Section 40
Chapter 39,606

Combined action of chloramphenicol and ampicillin on chloramphenicol-resistant Haemophilus influenzae

Mackenzie, A.M.; Chan, F.T.

Antimicrobial Agents and ChemoTherapy 29(4): 565-569


ISSN/ISBN: 0066-4804
PMID: 3486629
DOI: 10.1128/aac.29.4.565
Accession: 039605410

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The interaction of ampicillin and chloramphenicol on three ampicillin-susceptible, chloramphenicol-resistant strains of Haemophilus influenzae was studied by checkerboard testing with subcultures, time-kill experiments, and a disk method. In all three strains there was inhibition of the bactericidal action of ampicillin by chloramphenicol at concentrations close to the MIC (10 micrograms/ml). This chloramphenicol concentration was close to that which might be achieved in cerebrospinal fluid during treatment for meningitis and was in the bactericidal range for chloramphenicol-susceptible organisms. It is suggested however that in the initial treatment of meningitis caused by ampicillin-susceptible, chloramphenicol-resistant strains, inhibition of the action of ampicillin by chloramphenicol may represent a clinical risk.

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