In Vivo Antagonism between Gentamicin and Chloramphenicol in Neutropenic Mice

Abstract

The combination of gentamicin and chloramphenicol provides broad antimicrobial coverage for both aerobic and anaerobic gram-negative bacteria. Chloramphenicol, however, impairs the early bactericidal activity of gentamicin in vitro. The significance of this antagonism was examined in experimental Proteus mirabilis infections in mice. Survival did not differ significantly between groups of normal mice treated with gentamicin plus chloramphenicol and those treated with gentamicin alone. If the animals were first rendered neutropenic by whole-body radiation, a marked reduction in survival was observed with the combination as compared with gentamicin alone. Antibiotic antagonism may become clinically significant when phagocytic function is reduced.