Comparison of in vitro activity of @entity1536 antibiotics and @entity2176 against XXXX - and @entity3256 -resistant @entity794 by time-kill kinetic studies.

@entity3256 @entity801 @entity2176 @entity4258 @entity71084 @entity794 @entity2177 @entity1536
@entity1536 antibiotics have been proposed as possible alternatives to @entity2176 for @entity3256 -resistant @entity794 infections. We investigated the activities of @entity71084 , @entity2177 , @entity4258 , and @entity2176 by time-kill kinetic studies. Antibiotic concentrations of 0, 1.0, and 4.0 times the MIC were used against four strains of @entity801 - and @entity3256 -resistant @entity794 . Staphylococci were plated onto @entity2177 -containing agar at all time points, in repeat time-kill kinetic studies. Macrobroth dilution MICs and MBCs were determined. @entity2177 levels were measured by bioassay. Replica plating was performed from the original susceptible inoculum (MIC, 0.125 micrograms/ml) onto @entity2177 -supplemented agar. At 4.0 times the MIC, only with @entity2177 was there regrowth at 24 and 48 h. All four strains of staphylococci grew on agar supplemented with 1 microgram of @entity2177 per ml; three of four grew on agar supplemented with 2 micrograms of @entity2177 per ml. MICs and MBCs for these resistant clones ranged from 8 to 32 micrograms/ml. No degradation in activity or amount of @entity2177 could be detected in the bioassay. Replica-plated staphylococci grew on agar containing 1 microgram/ml but not higher concentrations of @entity2177 at 48 h. @entity71084 and @entity4258 sustained bactericidal activity comparable to that of @entity2176 . We conclude that heteroresistant subpopulations of @entity801 - and @entity3256 -resistant @entity794 can emerge under antibiotic selection pressure. Such resistant clones may then mutate in the presence of subinhibitory concentrations of antibiotic to higher levels of @entity2177 resistance.
