TABLE 2.

Effect of prior exposure to metronidazole on the efficacy of H. pylori eradication therapy

Characteristic	Infection, treatments,a and results for group 3 mice, by subgroups
	Control	Expt 1	Expt 2	Expt 3	Expt 4
No. of mice	10	10	9	10	8
Inoculating suspension	PTB	H. pylori SS1	H. pylori SS1	H. pylori SS1	H. pylori SS1
Treatment 1	PTB	PTB	MTZ	PTB	MTZ
Treatment 2	PTB	PTB	PTB	OCM	OCM
Infection with H. pylorib	0/10	10/10	7/9	3/10d	6/8d
Infection with MTZ-resistant H. pyloric	0/10	0/10	6/9	2/10d	6/8d
Ratio of resistant to sensitive isolates			1:100	<1:200	1:25
Range of MICs for resistant isolates (μg/ml)			16–32	16	16–32

^aPTB, peptone trypsin broth; MTZ, metronidazole; OCM, omeprazole, clarithromycin, and metronidazole. 

^bProportion of mice infected with H. pylori 2 months after the completion of treatment. 

^cProportion of mice from which resistant strains were isolated. In all cases, these were mixed with sensitive strains. 

^dStatistically significant difference (P < 0.01).