Journal of Clinical Microbiology, September 1999, p. 3001-3004, Vol. 37, No. 9
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Department of Microbiology & Parasitology,
Received 4 January 1999/Returned for modification 16 March
1999/Accepted 7 June 1999
Helicobacter pylori virulence determinants have not
previously been studied in detail in Latin Americans with H. pylori infections. We characterized the vacA
(vacuolating cytotoxin gene A) and cagA (cytotoxin-associated gene A) types of more than 400 single-colony isolates from 20 patients in Mexico City. For 17 patients H. pylori strains of two or more different vacA
genotypes were isolated from gastric biopsy specimens, indicating
infection with two or more strains of H. pylori. The most
frequent vacA genotype was s1b/m1. vacA
diversity was more marked than that described previously, in that
isolates from seven patients had untypeable vacA midregions and isolates from nine patients had type s1 signal sequence coding regions which could not be further subtyped. Previously undescribed vacA type s2/m1 strains were found in five patients. All
patients were infected with cagA-positive strains, but
occasionally, these coexisted with small numbers of
cagA-negative strains. In conclusion, coinfection with
multiple H. pylori strains is common in Mexico, and
vacA in these strains is genetically more diverse than has been described in other populations.
*
Corresponding author. Mailing address: Department of
Microbiology & Parasitology, Faculty of Medicine, Avenida Universidad 3000, Copilco-Universidad, CP. 04510 Mexico City, Mexico. Phone: (525)
616-0844. Fax: (525) 603-2416*51. E-mail:
lvidal{at}servidor.unam.mx.
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