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Infection and Immunity, November 2000, p. 6240-6249, Vol. 68, No. 11
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Distribution of Open Reading Frames of Plasticity Region of Strain J99 in Helicobacter pylori Strains Isolated from Gastric Carcinoma and Gastritis Patients in Costa Rica

Alessandra Occhialini,1 Armelle Marais,1 Richard Alm,2 Fernando Garcia,3 Rafaela Sierra,4 and Francis Mégraud1,*

Laboratoire de Bactériologie, Université Victor Ségalen Bordeaux 2, 33076 Bordeaux, France1; AstraZeneca R&D Boston, Waltham, Massachusetts 024512; and Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología,3 and Instituto de Investigaciones en Salud,4 Universidad de Costa Rica, 2060 Ciudad Universitaria Rodrigo Facio, San José, Costa Rica

Received 11 May 2000/Returned for modification 27 June 2000/Accepted 14 August 2000

The plasticity region of Helicobacter pylori strain J99 is a large chromosomal segment containing 33 strain-specific open reading frames (ORFs) with characteristics of a pathogenicity island. To study the diversity of the plasticity region, 22 probes corresponding to 20 ORFs inside the plasticity region and two ORFs on its boundaries were hybridized to genomic DNA isolated from clinical strains of H. pylori from patients with gastritis or gastric adenocarcinoma. Highly variable hybridization patterns were observed. The majority of the clinical strains presented a hybridization profile similar to that of J99; thus, these ORFs are not J99 strain specific. No association was found between a particular hybridization pattern and the clinical origin of the strain. Nevertheless, two single ORFs (JHP940 and JHP947) were more likely to be found in gastric cancer strains. They may be new pathogenicity markers. An in vitro expression study of these ORFs was also performed for the J99 strain, under different conditions. Thirteen ORFs were consistently expressed, six were consistently shut off, and three were expressed differentially. Most of the constitutionally expressed genes were located on the 3' part of the plasticity region. Our results show that the plasticity region, rather than being considered a pathogenicity island per se, should be considered a genomic island, which represents a large fragment of foreign DNA integrated into the genome and not necessarily implicated in the pathogenic capacity of the strain.

* Corresponding author. Mailing address: Laboratoire de Bactériologie, Hôpital Pellegrin, Place Amélie Raba Léon, 33076 Bordeaux Cédex, France. Phone: 33 5 56 79 59 10. Fax: 33 5 56 79 60 18. E-mail: francis.megraud{at}chu-bordeaux.fr.

Infection and Immunity, November 2000, p. 6240-6249, Vol. 68, No. 11
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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