The susceptibility of Helicobacter pylori to the rifamycin, rifaximin.

Forty strains of Helicobacter pylori had an MIC(50) of 4 mg/L of the non-absorbably antibiotic, rifaximin. Neither synergy nor antagonism was demonstrated when the drug was combined with ampicillin, metronidazole and omeprazole and the rate of spontaneous mutation was less than 1 in 10(8). With these in-vitro characteristics, rifaximin should now be assessed for clinical efficacy.