TABLE 2.
Frequency of spontaneous mutations
| Selective antibiotic (concn [μg/ml])a | H. pylori strain | No. of independent cultures | No. of cells per culture (108) | Resistant bacteria
|
Frequency of mutants | Mutation rate per cell divisionb | ||
|---|---|---|---|---|---|---|---|---|
| Zero fractionc | Mean | Median | ||||||
| RIF (20) | UA802 | 30 | 5.0 | 2/30 | 33d | 27 | 6.6 × 10−8 | 1.6 × 10−8 |
| RIF (20) | 26695 | 15 | 4.8 | 2/15 | 18.1 | 15 | 3.8 × 10−8 | 1.1 × 10−8 |
| RIF (20) | 11639 | 15 | 4.5 | 1/15 | 20.8 | 20 | 4.6 × 10−8 | 1.4 × 10−8 |
| CIP (1) | UA802 | 15 | 4.0 | 2/15 | 15.2 | 12 | 3.8 × 10−8 | 1.1 × 10−8 |
| CLA (0.5) | UA802 | 12 | 5.0 | 8/12 | 1.5 | 0 | 3 × 10−9 | 8 × 10−10 |
| MTZ (8) | 11639 | 15 | 4.5 | 11/15 | 2.3 | 0 | 5.1 × 10−9 | 6.9 × 10−10 |
| AMX (1) | 11639 | 12 | 4.3 | 12/12 | 0 | 0 | ?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.