Table 2.

Frequency of spontaneous mutations

Selective antibiotic (concn [μg/ml])aH. pylori strainNo. of independent culturesNo. of cells per culture (108)Resistant bacteriaFrequency of mutantsMutation rate per cell divisionb
Zero fractioncMeanMedian
RIF (20)UA802305.02/3033d 276.6 × 10−8 1.6 × 10−8
RIF (20)26695154.82/1518.1153.8 × 10−8 1.1 × 10−8
RIF (20)11639154.51/1520.8204.6 × 10−8 1.4 × 10−8
CIP (1)UA802154.02/1515.2123.8 × 10−8 1.1 × 10−8
CLA (0.5)UA802125.08/121.503 × 10−9 8 × 10−10
MTZ (8)11639154.511/152.305.1 × 10−9 6.9 × 10−10
AMX (1)11639124.312/1200 ?e ?
  • a RIF, rifampin; CIP, ciprofloxacin; CLA, clarithromycin; MTZ, metronidazole; AMX, amoxicillin.

  • b For calculation of mutation rate, see reference 28. The most likely number of mutations per culture was calculated by the p0 method for Clar and Mtzr and by the Lea-Coulson method of median for Cipr and Rifr.

  • c Proportion of cultures without mutants. For example, 2 of 30 cultures of UA802 used for selection of Rifr gave rise to no resistant mutants.

  • d A jackpot (∼1,000) was removed for calculation of the mean number of resistant mutants.

  • e ?, undetectable.