In vitro susceptibility of Helicobacter pylori to trospectomycin, pirlimycin (U-57930E), mirincamycin (U-24729A) and N-demethyl clindamycin (U-26767A).

The in vitro activity of trospectomycin, pirlimycin, mirincamycin and N-demethyl clindamycin was measured against 46 clinical isolates of Helicobacter pylori using an agar dilution technique. The MIC50 and MIC90 were 4 and 64 micrograms/ml for pirlimycin and N-demethyl clindamycin, and 32 and 128 micrograms/ml for mirincamycin, respectively. All 46 strains were sensitive to trospectomycin with an MIC50 of 8 micrograms/ml and an MIC90 of 16 micrograms/ml. Of seven strains with the highest trospectomycin MICs (8 or 16 micrograms/ml) 100% were found to be resistant to metronidazole. Among ten strains with low trospectomycin MICs (2 micrograms/ml or less) 100% were sensitive to metronidazole. Possible explantations for the apparent correlation between the MICs of the two drugs are discussed. Since all metronidazole resistant strains were sensitive to trospectomycin, this drug may be useful in treating infection with metronidazole resistant Helicobacter pylori.