TABLE 1.

cagA status and vacA genotypes of strains used in this study as assessed by PCR typing

Country of origin	No. of strains tested	No. of strains
		cagA status		vacA signal sequence type				vacA midregion type
								Original method			New method
		+ Positive	− Negative	s1a or s1ca	s1b	s1, not s1a or -c, or s1b	s2	m1	m2	Neither	m1	m2	Neither
United Statesb	41	31	10	18	13	0	10	15	26	0	15	26	0
Peru	8	7	1c	5d	1e	2f	0	3	4	1	4	4	0
Japan	13	13	0	13	0	0	0	0	0	13	13	0	0
Thailand	9	9	0	9	0	0	0	0	6	3	3	6	0
China	6	6	0	6	0	0	0	0	1	5	4	1	1g
Total	77	66	11	51	14	2	10	18	37	22	39	37	1

^aThe vacA s1 subtyping system that we used was not designed to distinguish between types s1a and s1c. 

^bThese U.S. strains were described previously (1) but are included here because they were retyped with our new primers. 

^cThis cagA-negative strain was vacA s1 (not s1a or -c, or s1b) and m2. 

^dNucleotide sequence analysis of two of these alleles showed that they were intermediate between s1a and s1b. 

^eThis vacA s1b strain was cagA positive and vacA m1. 

^fOne of these strains was cagA positive and vacA m1, and the other was cagA negative and vacA m2. The vacA alleles of these strains were intermediate between s1a and s1b but were more similar to s1b. 

^gThe vacA allele of this strain was an m1/m2 hybrid.