POSTANTIBIOTIC EFFECT, AND POSTANTIBIOTIC EFFECT OF SUBINHIBITORY CONCENTRATIONS, OF SPARFLOXACIN ON GRAM-NEGATIVE BACTERIA

The postantibiotic effect (PAE), the postantibiotic sub-MIC effect (PA SME), and the sub-MIG effect (SME) of a new oral quinolone, sparfloxa cin, were determined for different strains of gram-negative bacteria. A PAE was induced by 10 x MIC of sparfloxacin for 2 h and the antibiot ic was then eliminated by washing and dilution. The PA SME was studied by adding different sub-MICs during the postantibiotic phase, and the SME by exposing the controls to the sub-MICs alone. Growth curves wer e followed for 20 h by continuous monitoring of optical density in an automatic incubator. Sparfioxacin induced a PAE of 0.9-2.4 h for all s trains except two clinical strains of Enterobacter cloacae. In accorda nce with earlier experiments with sparfloxacin and gram-positive bacte ria, this study showed a PA SME that was nearly equal to the PAE plus the effect of the subinhibitory concentration alone (SME).