METRONIDAZOLE SENSITIVITY TESTING OF HELICOBACTER-PYLORI - THE IMPORTANCE OF MEDIA

Successful triple-therapy: treatment for Helicobacter pylori infection depends upon metronidazole (Mz) susceptibility, and many hospital lab oratories routinely screen H.pylori isolates for Mt resistance using d isc diffusion methods. We report the importance of culture medium a he n testing for metronidazole susceptibilitly. In this laboratory, Mz re sistance in strains of H. pylori from patients in our area was found i n approximately 80%. In other areas, Mt resistance is found in approxi mately 30%. This high rate of Mz resistance was not reflected clinical ly. Added haemin (X factor) and menadione in the culture medium drasti cally reduced zone size to Mz and also interfered with the minimal inh ibitory concentration (MIC) as determined by Etest(R) When strains of H. pylori were re-tested on media which did not contain X factor or me nadione, Mz resistance fell from 80% to 39%, a level similar to that s een in other areas.