Abstract
To assess possible synergy or antagonism of anpicillin (A) and chloramphenicol (C), we performed killing curves on 9 strains of Haemophilus influenzae type B (HITB) isolated from blood or CSF. All were susceptible to A (mean MIC 0.33 ± 0.15 μg/ml, range 0.2 - 0.625) and C (mean MIC 0.79 ± 0.43 μg/ml, range 0.3 - 1.5) by the broth dilution technique at an inoculum of 105 CFU. Killing curves were performed with an early log phase inoculum of 105 CFU. Bactericidal activity was examined at the following antibiotic concentrations: the MIC of A, 50% of the MIC of A, 25% of the MIC of A, the MIC of C, 50% of the MIC of C, 25% of the MIC of C, and combinations of these concentrations. For each strain, killing was assessed after 0, 4, and 8 hours of incubation at 37°C; bacteria were enumerated by serial tube dilution in cold phosphate buffered saline. No antagonism or synergy were found after 4 and 8 hours. At 4 hours, mean colony counts of all 9 strains incubated at the MIC of A were significantly higher (2.2 × 105 ± 0.7) than those incubated at the MIC of C (2.1 × 104 ± 1.5) (p < 0.01) and significantly higher than those incubated at the MIC of A plus the MIC of C (1.5 × 104 ± 1.0) (p < 0.01). These data and the rates of killing observed with other concentrations of A and C suggest that C kills HITB more rapidly than A, and that C defines the rate of killing when A and C are present together.
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Cole, F., Goldmann, D., Teller, L. et al. 760 KILLING CURVE ASSESSMENT OF SYNERGY/ANTAGONISM OF AMPICILLIN AND CHLORAMPHENICOL VS. HAEMOPHILUS INFLU-ENZAE TYPE B. Pediatr Res 12 (Suppl 4), 490 (1978). https://doi.org/10.1203/00006450-197804001-00765
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DOI: https://doi.org/10.1203/00006450-197804001-00765
