Four strains of a novel Helicobacter species were isolated from the stomachs of cheetahs (Acinonyx jubilatus) with gastritis. These isolates were phenotypically similar to Helicobacter pylori. The isolates were gram-negative, spiral bacteria which grew under microaerophilic conditions at 37 degrees C, but not at 25 or 42 degrees C, and produced urease, catalase, oxidase, alkaline phosphatase, and gamma-glutamyl transpeptidase. The isolates did not ferment glucose, mannitol, inositol, sorbitol, rhamnose, sucrose, melibiose, amygdalin, or arabinose; hydrolyze hippurate or indoxyl acetate; or reduce nitrate. They did not produce H2S from triple sugar iron agar, and they did not grow in the presence of 1.0% glycine or 1.5% NaCl. They were resistant to nalidixic acid and sensitive to cephalothin and metronidazole. Cells were typically 0.3 by 2.0 microns and possessed tufts of two to five sheathed, monopolar flagella. The G+C content of strain 90-119 was 30 mol%. Cluster analysis of densitometry scans of polyacrylamide protein gels revealed more than 70% similarity of the cheetah isolates to H. pylori, less than 60% similarity to Helicobacter felis, and less than 50% similarity to Helicobacter mustelae. Complete 16S rRNA sequences were determined for two of the cheetah isolates. Phylogenetic analysis was performed by comparing the cheetah sequences to those of 19 reference strains, including H. pylori, H. felis (two strains), H. mustelae, Helicobacter muridarum, "Flexispira rappini," Wolinella succinogenes, Campylobacter coli, Campylobacter concisus, Campylobacter curvus, Campylobacter fetus, Campylobacter hyointestinalis, Campylobacter jejuni, Campylobacter lari, Campylobacter rectus, Campylobacter sputorum subsp. bubulus, a Campylobacter sp. (pig isolate), [Bacteroides] gracilis, and [Bacteroides] ureolyticus.(ABSTRACT TRUNCATED AT 250 WORDS)

A mutant strain of Helicobacter pylori with weak urease activity was created by using N-methyl-N'-nitro-N-nitrosoguanidine. The urease activity of the mutant (0.036 +/- 0.009 nmol of urea per micrograms of bacterial protein per min) was 0.4% of that of the parental strain (8.20 +/- 2.30 nmol of urea per micrograms of bacterial protein per min). The mutant was otherwise indistinguishable from the parental strain. Both demonstrated prominent catalase and oxidase activities, and both produced vacuolating cytotoxin. Restriction endonuclease and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns and ultrastructure were identical for the two strains. The mutant was fully motile, as evaluated by spreading in soft agar and by direct microscopic examination. Growth rate and colony size and morphology were identical for the mutant and parental strains. Seventeen gnotobiotic piglets were challenged with either the mutant or the parental strain and sacrificed 3 or 21 days after challenge. Gastric tissue was examined histologically and cultured for H. pylori. Of seven piglets challenged with the parental strain, all became infected. H. pylori was not recovered from any of 10 piglets challenged with the urease-negative strain. Lymphofollicular gastritis was present in all seven piglets challenged with the parental strain but in none of the piglets challenged with the urease-negative strain. These results suggest that prominent urease activity is essential for colonization by H. pylori.

Two kinds of gastric spiral bacilli were identified in the stomachs of captive cheetahs with naturally occurring gastritis. One type was morphologically similar to 'Gastrospirillum hominis'. This organism could not be cultured in vitro. Some of these bacteria had superficial helical filaments, and others did not. The other type was morphologically, biochemically, and bacteriologically similar to Helicobacter pylori. This organism is most likely a new species of Helicobacter. One or both of these bacteria may have been responsible for the gastritis seen in these cheetahs.

Helicobacter pylori has recently been recognized as a gastric pathogen in humans. Experimental oral inoculation of gnotobiotic piglets with this organism results in gastritis that exhibits many features of the corresponding disease in humans. In piglets the organism is restricted to the gastric microenvironment and persists in that location despite prompt humoral and cellular responses to antigens of H. pylori. The gnotobiotic piglet model is useful for delineation of the role of suspected bacterial virulence factors (i.e., motility and urease production) in gastric colonization and for preclinical determination of the efficacy of various antimicrobial substances.

Thirty-three gnotobiotic piglets from four litters were challenged with motile and nonmotile strains of Campylobacter pylori. The most motile strain, 26695, was the most virulent, with a 100% infection rate. The least motile strain, Tx30a, was the least virulent, with an infection rate of only 17%. Strain 60190 was weakly motile and had intermediate virulence, with an infection rate of 40%. Strains recovered from piglets were more motile than the challenge strains. The challenge strains also differed in cytotoxin production. The least virulent strain, Tx30a, was nontoxigenic, while the other two strains produced high levels of cytotoxin. Thus, virulence of C. pylori for gnotobiotic piglets correlated very well with motility and not as well with cytotoxin production.

ABSTRACTMembers of the genus Aeromonas are frequently found in the environment, food, and water. Aeromonas hydrophila is a human pathogen which causes skin infections, septicemia, and endocarditis predominantly in immunocompromised patients. Epidemiological studies indicate that A. hydrophila may be an important cause of food‐borne gastroenteritis, but studies in primates and humans have not confirmed the pathogenic role. Further characterization of virulence determinants may clarify the importance of this organism. In this review, the organisms, epidemiological evidence, and the challenge studies are discussed in an attempt to determine the role of Aeromonas sp. in the pathogenesis of food‐borne gastroenteritis.