In-vitro susceptibility of oral streptococci to pristinamycin.

The inhibitory activity of pristinamycin against oral streptococci was compared with that of amoxycillin, erythromycin and vancomycin. Minimum inhibitory concentrations (MICs) of pristinamycin ranged from 0.03-1 mg/l (mode 0.25 mg/l), similar to those for amoxycillin. Erythromycin had a mode MIC of 0.06 mg/l and vancomycin, the least active, 1 mg/l. However, in killing curve experiments to compare the bactericidal activities of pristinamycin and erythromycin against several strains of oral streptococci, pristinamycin was substantially more active, consistently producing a rapid decrease in viable count during the first few hours of incubation. Pristinamycin may prove to be of value for the prophylaxis of post-dental extraction bacteraemia.