Jpn. J. Infect. Dis., 52, 183-197, 1999 Invited Review Association of Helicobacter pylori with Gastroduodenal Diseases Yoshikazu Hirai*, Shunji Hayashi, Hirofumi Shimomura, Keiji Ogumal and Kenji Yokotal Department of Microbiology, Jichi Medical School, Yakushiji 3311 -1 , Minamikawachi-machi, Kawachi-gun, Tochigi 329-0498 and JDepartment of Bacteriology, Okayama UniversityMedical School, Shikata-cho 2-5-1 , Okayama 700-8558, Japan (Received October 22, 1999) SUMMARY: Helicobacter pylori was first cultured in vitro in 1982･ This bacterium is a spiral gram-negative rod which grows under microaerophilic conditions･ The ecological● niche is the mucosa bf the human stomach which had been thought to be aseptic before the discovery of this bacterium･ This organism causes a long-lasting infection throughout a person's life if there is no medical intervention･ Numerous persons are infected with the organism around the world, and the rate of infection in Japan is nearly 50% of the population･ However, the route of infection remains unclear because the organism has not been isolatedfromany environment other thanseveral animals･ H･ pylori is now recognlZed● as a causative agent of gastritis and peptic ulcers･ Though gastritis, and especially chronic active gastritis, is observed at least histologlCally● in all persons with H. pylori, peptic ulcers develop ln● Only some infectedpersons. Specific factors in the host and/Or the bacteria are needed for the development of peptic ulcer disease･ Furthermore, H･ pylori is considered to be related to the development of gastric mucosa- associated lymphoid tissue (MAIJ) lymphoma, especially those of low grade. Also, H. pylori infection is a major● determinant for initiating the sequence of events leading to gastric cancer･ In some patients with low-grade gastric MAIJ lymphoma, the eradication of H. pylori led to a regression of lesion. Gastric cancer has been induced in Mongolian gerbils with long-term H･ pylori infection･ The combinations of drugs, which consist of an antisecretory agent (acid-supressing agent) and antimicrobial agents, are used for the eradication of the organism. ● Eradication therapy lS recommended at least fわr patients with peptlC ulcers･ ● 1. 1mtroduction 2. BacteriologICal features Helicobacter pylori is a curved or splral gram-negative H. pylori is a short spiral or S-shaped gram-negative rod, bacterium, and can colonize in and under the mucus layer of 0.5-0.9 〝m wide and about 3 〝m long, in the stomach. It is humangastriC mucosa without the copresence of other bacterial motile by means of a tuft of up to eight sheathed flagella at species. The bacterium was first cultured in Perth, Western one pole (Fig. 1). The sheath is a kind of membrane and its Australia, and was first reported in 1983 as a Campylobacter- bi∝hemical composition resembles that of the outer membrane･ like organism ( I ,2). The organism was named Campylobacter The organism grows under microaerophilic conditions･ pyloridis, but this was later changed to C. pylori. Subsequently, Mediathat contain serum or blood are usually used. For the it was asslgned to the new genus Helicobacter, and is now first isolation from gastric biopsy, Ski汀OW's medium is known as Helicobacter pylori (3). commonly recommended･ However, H･ pylori can grow in a The first paper relating to H. pylori described its association serum-free medium containing 0.1-0.2% of dimethyl β- with gastritis ( 1 ). Researchers indicated that the organism can cyclodextrin (7,8). The growth of H･ pylori i.n a synthetic cause human gastritis by oral self-administration of the living medium was reported, but it contained largeamounts of tDVine bacteria to the stomach (4,5). H. pylori infection is now recog- serum albumin (9). In liquid culture, shaking is necessary for ● nized as the pnmary cause of active chronic gastritis and as good quality and uniform growth･ an important causal factor in peptic ulcers. Furthermore, the By a time-expired culture or changes in gas conditions, 〃･ infection is regarded to be deeply associated with low-grade pylori transforms to a coccoid form (Fig･ l)･ The coccoid B-cell gastric lymphoma and gastric cancer. It was reported form of the bacteria (C∝coid body) cannot grow in any media in 1998 that H. pylori infection induced gastric cancer in or under any artificial conditions･ However, it is reported that mongolian. gerbils (6)･ the oral inoculation of the coccoid body induces gastritis in This revleW fauses onand summarizes mainly the bacteri0- mice (10). It remains unclear whether the coccoid body is in logicalfeatures of H. pylori and the association between the a viable but non-culturable state (VNC). organism and gastroduodenal diseases. In representatives of conventional biochemical tests, 〃･ pylori is positive for oxidase, catalase, urease, alkaline phos- *Corresponding author: Tel: +81 -285-58-733 1 , Fax: +81 -285-44- phatase, and T-glutamyl transpeptidase, and is negative fわr nitrate reduction･ The organism utilizes glucose but gives no 1175 indication of acid production･ Some Helicobacter spp･ have periplasmic fibers (Fig･ 2), but H･ pylori does not･ Of these ThisarticleisanⅠnVitedReviewbasedonalecturepresentedat characteristics, urease is of the most importance. The urease the9thSymposlumOftheNationalInstituteofInfectiousDiseases, of the organism indicates a low Km value as compared to Tokyo,21May1999. other ureases (Table l ). Furthermore, the large content of urease 183 Fig･ l･ Electron micrographs of Helicobacter pylori (negative staining) A; A spiral form of the bacteria with sheathed flagella at the end of the cell･ B; A curved-rod form of the bacteria. C; Coccoid forms induced by a time-expired culture･ Sheathed nagella remain･ D', Sheated nagella (highmagnification)･ True nagella are observed at the site indicated by arrows. the backbone of lipid A, D一gulcosamine disaccharide (19)･ ● Because of these unlque features, the endotoxic activity of the LPS is very low compared with that of Enterobacteriaceae (20,21). However, the LPS is recognized as an important factor in the inducement of gastritis, becausethe C3H/He mouse which minimally responds to LPS shows very low-grade gastritis in H. pylori infection compared with the C3H/H mouse which is a responder (22). H. pylori has three kinds of cholesteryl glucosides (CGs) (Fig. 3) (23). CGs are very rare in animals and bacteria･ In bacteria, CGs have been reported only ln● Mollicutes (Acholeplasma spp. , Mycoplasam gallinarum, Spiroplasma citri) and Borrelia hermsii. We, however, found for the first time a phosphate-linked cholesteryl glucoside like cholesteryl phosphatidyl glucoside (CPG) in Helicobacter･ In the organism, CGs contribute about 25% by weight of the total extractable Fig･ 2･ An electron micrograph ofH･ rappini (Flexispira rawini) (nega- tive staining). lipids. The organism cannot synthesize cholesterol in the same Periplasmic fibers (PFs) are observed. In this photograph, views or way as other bacteria, but appears to accumulate free choles- PFs on the upside and downside or a bacterium are overlapped･ terol from media (24). Furthermore, CGs appear to be a unique feature of genus Helicobacter, because they are present in 1 6 exists at the su血ce ofcells (17), whereas it exists only in the of 18 Helicobacter species (25,26). cytoplasm of other bacteria. Therefわre, the organism exhibits As mentioned above, urease is located on the outer mem- very high urease activity in the whole cell, which is commonly brane. Heat shock protein (HSP) 60 is also fわund in the same used as a method for diagnosis of H. pylori infection. H. pylori location. It was reported that this was synthesized in the itself is intolerant of strong acids, but the organism prefers cytoplasm and absorbed on the su血ce after spontaneous mildly acidic conditions and can withstand a pH as low as autolysis (27)･ Theseチre majo.r proteins in the organism･ 1.5 when urea is present (18). The overall genomlC OrganlZation has been fわund in two H･ pylori shows unlque● membrane features. On lipopolysac- strains, J99 (28) and 26695 (29), of H. pylori. The general charide (LPS), Compared with lipid A of members of Enter?- features are listed in Table 2. The annotated genome sequences ● bacteriaceae, the lipid A of H. pylori has an unusual composl- and further information concernlng Strains J99 and 26695 are tion of fatty acids (310H C18:0) and also a different phos- available on the World Wide Web site (http://www.tigr.org/ phorylation pattern, with 1 '- but not 4'-phosphate present in tdb/mdb/hpdb/hpdb.html) and in the H･ pylori database 184 Table 1 ･ Biochemical characters of purified ureases Kml) specific native Mr subunit Mrs) subunit metal (mM) acti v i ty 1 ･2) (kDa) (kDa) composl tlOn COntent Helicobacter pylori O･ 17 1 , I 00 530 α =26.6 (α･β) 1.0 Ni/β -0.48 - 1 ,700 β =60.5 ×6 Klebsiella aerogenes 2.8 2,200 224 α=9 (α2･β2･γ) 2.1 Ni β=11 ×2 /(α2･β2･γ) γ =72 Ureaplasma urealyticum 2.5 33,530 150 α=66 α2or α5or α6 -4. 5 - 1 80,000 -380 -76 Jack bean(plant) 2.9 1 ,000 590 α=98 α6 2.0 Ni/α -5,500 1)These data were measured with different buffers, temperatures, and pHs･ 2) LLmol of urea/min per mg of protein 3)The small, mediumand large subunits are designated as a, B, and T, respectively. (from refs. ll-16 ) CGL (G･2): Table 2･ General features of the H･ pylori genomes Cholesteryl･a･D･glucopyranoside (base substance) strain 26695 strain J99 Patient (Country) gastritis duodenal ulcer (the UK) (the USA) Size (base pairs) 1 ,667,867 1 ,643,83 I G+C content (%) 39 39 Regions of different