TABLE 3

H. pylori resistance to MET, CLR, and PAa

Passage no. (3×)MIC (μg/ml) of drug to strain:
NCTC26695NCTC11637SS1
METCLRPAMETCLRPAMETCLRPA
00.50.0156250.50.0156250.50.015625
110.03122510.03122510.031225
220.06242520.06242520.062425
340.12482540.12482540.124825
480.249680.249680.2496
5160.49921616
6320.99843232
7641.99686464
81283.9936128128
92567.9872256256
10512512
  • a MET, metronidazole; CLR, clarithromycin. The MICs of MET, CLR, and PA for the original strains before passage are shown in the first row, and the MICs for three control groups remained constant (data not shown). Every three passages in antibiotic plates meant one-step induction, and 3× means three successive passages were cultured in the plate with the same antibiotic concentration. —, end of induction. The end of the resistance induction experiment was indicated by the absence of any change in MIC after nine passages at the same concentration or when the MICs were more than 1,024 times the original values.