TABLE 2.

Frequency of occurrence of spontaneous mutants in H. pylori strains resistant to rifampin, KRM-1648, KRM-1657, and amoxicillin and MICs for parental strain and mutant clone

Strain	Druga	Frequency of mutation	Mutant cloneb	MIC (μg/ml)
				Rifampin	KRM-1648	KRM-1657
NCTC11637				0.25	0.004	0.001
	Rifampin	2.1 × 10−8	NCTC11637-RFPr	>50	>10	10
	KRM-1648	7.1 × 10−8	NCTC11637-K48r	>50	>10	1.6
	KRM-1657	7.1 × 10−8	NCTC11637-K57r	>50	>10	3.2
	Amoxicillin	<7.1 × 10−9
HPK5				0.25	0.004	0.001
	Rifampin	2.9 × 10−7	HPK5-RFPr	>50	>10	>10
	KRM-1648	2.1 × 10−7	HPK5-K48r	>50	>10	>10
	KRM-1657	5.3 × 10−7	HPK5-K57r	>50	>10	>10
	Amoxicillin	<5.1 × 10−9
CPY1124				8	0.004	0.001
	Rifampin	2.0 × 10−6	CPY1124-RFPr	>50	>10	>10
	KRM-1648	1.5 × 10−6	CPY1124-K48r	>50	>10	>10
	KRM-1657	8.7 × 10−7	CPY1124-K57r	>50	>10	>10
	Amoxicillin	<5.0 × 10−9
CPY3281				4	0.016	0.001
	Rifampin	1.2 × 10−6	CPY3281-RFPr	>50	>10	10
	KRM-1648	6.4 × 10−7	CPY3281-K48r	>50	>10	10
	KRM-1657	7.9 × 10−7	CPY3281-K57r	>50	>10	10
	Amoxicillin	<3.0 × 10−9
CPY3401				0.125	0.004	0.0005
	Rifampin	6.6 × 10−7	CPY3401-RFPr	>50	>10	1
	KRM-1648	4.6 × 10−8	CPY3401-K48r	>50	>10	>10
	KRM-1657	2.3 × 10−7	CPY3401-K57r	>50	>10	>10
	Amoxicillin	<1.5 × 10−9
CPY6071				4	0.008	0.001
	Rifampin	4.5 × 10−7	CPY6071-RFPr	>50	>10	>10
	KRM-1648	8.2 × 10−8	CPY6071-K48r	>50	>10	>10
	KRM-1657	1.9 × 10−8	CPY6071-K57r	>50	>10	3.2
	Amoxicillin	<4.5 × 10−9

^aThe concentrations selected for isolation were 50, 3.1, 0.1, and 3.1 μg/ml for rifampin, KRM-1648, KRM-1657, and amoxicillin, respectively. 

^bRFP^r, K48^r, and K57^r represent clones of each strain resistant to rifampin, KRM-1648, and KRM-1657, respectively.