Abstract
A discrepancy between the MIC and the MBC of penicillin (pen) against GBS has been reported, suggesting that the relapses of GBS disease after treatment with conventional doses of pen may be a result of this discrepancy. In this study, we measured pen MIC and MBC levels against GBS and compared them with levels obtained for GAS, an organism that has been successfully treated for years with conventional doses of pen without evidence of relapse in normal hosts. These experiments confirmed the reports that a large MIC/MBC discrepancy exists in GBS(10 fold); however, a larger discrepancy exists for GAS(25 fold). These findings diminish the likelihood of clinical significance of the MIC/MBC ratio alone in accounting for the relative difficulty in treating GBS. Other factors, such as the lower absolute sensitivity of GBS to pen compared to that of GAS, must be playing a role: both the MIC and the MBC values were significantly higher for GBS than for GAS.
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Allen, J., Sprunt, K. 750 DISCREPANCY BETWEEN MINIMUM INHIBITORY CONCENTRATION (MIC) AND MINIMUM BACTERICIDAL CONCENTRATION (MBC) OF PENICILLIN DEMONSTRATED IN GROUP A (GAS) AND GROUP B β- HEMOLYTIC STREPTOCOCCI (GBS). Pediatr Res 12 (Suppl 4), 488 (1978). https://doi.org/10.1203/00006450-197804001-00755
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DOI: https://doi.org/10.1203/00006450-197804001-00755