Table 1.

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

Country of originNo. of strains testedNo. of strains
cagAstatusvacA signal sequence typevacA midregion type
Original methodNew method
+ Positive− Negatives1a or s1cas1bs1, not s1a or -c, or s1bs2m1m2Neitherm1m2Neither
United Statesb41311018130101526015260
Peru871c5d1e2f0341440
Japan131301300000131300
Thailand9909000063360
China6606000015411g
Total776611511421018372239371
  • a The vacA s1 subtyping system that we used was not designed to distinguish between types s1a and s1c.

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

  • c This cagA-negative strain wasvacA s1 (not s1a or -c, or s1b) and m2.

  • d Nucleotide sequence analysis of two of these alleles showed that they were intermediate between s1a and s1b.

  • e This vacA s1b strain wascagA positive and vacA m1.

  • f One of these strains was cagApositive and vacA m1, and the other was cagAnegative and vacA m2. The vacA alleles of these strains were intermediate between s1a and s1b but were more similar to s1b.

  • g The vacA allele of this strain was an m1/m2 hybrid.