SUMMARY.The succession of bacterial populations in the large bowel of seven breast-fed and seven formula-fed infants was examined during the first year of life. The composition of the intestinal microflora varied according to the infant's diet. During the first week of life breast-fed and formula-fed infants were colonised by enterobacteria and enterococci followed by bifidobacteria, Bacteroides spp., clostridia and anaerobic streptococci. From week 4 until solid foods were given, breast-fed babies had a simple flora consisting of bifidobacteria and relatively few enterobacteria and enterococci. Formula-fed babies during the corresponding period were more often colonised by other anaerobes in addition to bifidobacteria and had higher counts of facultatively anaerobic bacteria. The introduction of solid food to the breast-fed infants caused a major disturbance in the microbial ecology of the large bowel as counts of enterobacteria and enterococci rose sharply and colonisation by Bacteroides spp., clostridia and anaerobic streptococci occurred. This was not observed when formula-fed infants began to take solids; instead, counts of facultative anaerobes remained high while colonisation by anaerobes other than bifidobacteria continued. At 12 months, the anaerobic bacterial populations of the large bowel of breast-fed and formula-fed infants were beginning to resemble those of adults in number and composition and there was a corresponding decrease in the number of facultative anaerobes. These changes are discussed in relation to changes in susceptibility to gastro-intestinal infection.
Strain CSIT (T = type strain) is a gram-negative, microaerophilic, urease-positive, spiral-shaped bacterium that was isolated from the gastric mucosa of a cat. Additional strains which possessed biochemical and ultrastructural characteristics similar to those of strain CSIT were isolated from the gastric mucosa of cats and dogs. The guanine-plus-cytosine content of the DNA of strain CSIT was 42.5 mol%. The 16s rRNA sequences of strain CSIT, strain DS3 (a spiral-shaped isolate from a dog), and Helicobacter musteke were determined by direct RNA sequencing, using a modified Sanger method. These sequences were compared with the 16s rRNA sequences of Helicobacter pylon', "Flexispira rappini, " Wolinella succinogenes, and 11 species of campylobacters. A dendrogram was constructed based upon sequence similarities. Strains CSIT and DS3 were very closely related (level of similarity, 99.3%). Two major phylogenetic groups were formed; one group consisted of strains CSIT and DS3, H . mustelae, H . pylori, "F. rappini," and W . succinogenes, and the other group contained the true campylobacters. The average level of similarity between members of these two groups was 84.9%. Within the first group, strains CSIT and DS3, H . pylon', and H. mustelae formed a cluster of organisms with an interspecies similarity level of 94.5% The phylogenetic positions of W. succinogenes and "F. rappini" were just outside this cluster. On the basis of the results of this study, we believe that strains CSIT (= ATCC 49179T) and DS3 represent a new species of the genus Helicobacter, for which we propose the name Helicobacter felis.Cumpylobacter species commonly colonize the alimentary and genital tracts of mammals and birds, and some are responsible for gastrointestinal diseases (32). It has been proposed that the mucus lining the gut mucosa is the ecological niche inhabited by these bacteria (22, 25). Recently, increased attention has been focused on the species isolated from the stomachs of mammals, including humans (14,24). The gastric mucus appears to be the natural habitat of Helicobacter pylori, a bacterium associated with histological gastritis in human stomachs (27, 31), and Helicobacter mustelae, an organism associated with gastritis and ulcers in adult ferrets (9, 10). On the basis of 16s rRNA sequencing data and biochemical and phenotypic criteria, these two species were recently transferred from the genus Campylobacter to the genus Helicobacter (13). The overall phylogeny of members of the genus Campylobacter and related bacteria has been studied extensively (21, 34, 36, 40). These bacteria fall into three phylogenetic groups. have their own distinctive gastric floras (11, 23). A gramnegative, microaerophilic, urease-positive, spiral-shaped rod (strain CSIT [T = type strain]) was isolated from the gastric mucosa of a cat and has been described previously (28). Strain CSIT is physiologically similar to, but morphologically different from, H. pylori and H . mustelae. The gastric bacteria isolated thus far have different distinctive morpho...
Abstract. Five gnotobiotic Beagle dogs were orally inoculated with a pure culture of Helicobacter felis. The remaining two littermates served as contact controls. Thirty days after infection, all animals were euthanatized and specimens were collected for evaluation. In infected dogs, H. felis was recovered from all areas of the stomach. Colonization was heaviest in the fundus and antrum. H. felis was not cultured from any segment of the gastrointestinal tract distal to the duodenum. Two weeks after infection, all five infected dogs had detectable IgM and IgG serum antibody to H. felis, whereas control dogs had no measurable H. felis serum antibody throughout the study. Histopathologic changes in the stomachs of infected dogs included large numbers of lymphoid nodules throughout all regions of the gastric mucosa and were most numerous in the fundus and body. A mild, diffuse lymphocytic infiltrate with small numbers of plasma cells and eosinophils was also present in the subglandular region of all portions of the gastric mucosa. Electron microscopic examination revealed large numbers of spiral-shaped H. felis in gastric mucus adjacent to or superimposed over the areas of inflammation. Occasionally, however, H. felis was observed within the canaliculi of gastric parietal cells. Histopathologic changes in the stomachs of the contact control dogs were limited to focal infiltrates of eosinophils and small aggregates of lymphocytes in the subglandular portions of the gastric mucosa in one animal. Infection with H. felis is a likely cause of naturally occurring lymphofollicular gastritis.
Helical organisms with novel ultrastructural characteristics were isolated from the intestinal mucosa of rats and mice. These bacteria were characterized by the presence of 9 to 11 periplasmic fibers which appeared as concentric helical ridges on the surface of each cell. The cells were motile with a rapid corkscrewlike motion and had bipolar tufts of 10 to 14 sheathed flagella. The bacteria were microaerophilic, nutritionally fastidious, and physiologically similar to Helicobucter species and Wolinella succinogenes but could be differentiated from these organisms by their unique cellular ultrastructure. Using 16s rRNA sequencing, we found that strain STIT (T = type strain) was related to previously described Helicobucter species, "Flexispira rappini," and W . succinogenes. The closest relatives of strain STIT were Helicobacter mustelae and "F. rappini" (average similarity value, 96%). On the basis of phylogenetic data, strain STIT (= ATCC 49282T) represents a new species of the genus Helicobucter, for which we propose the name HeZicobucter muridarum.Bacteria with a variety of spiral morphologies are common inhabitants of the gastrointestinal tracts of both humans and animals (8-10, 20, 24-26, 30, 34, 39). Several of these spiral bacteria are helically coiled and possess bipolar tufts of flagella and concentric ridges that are due to periplasmic fibers that run the length of each cell. They have been seen in a variety of gastrointestinal preparations, including ceca (8) and ilea of rats (34), colons of mice (39), and gastric mucosa (26) and fundic glands of dogs and cats (20). Recently, organisms with a similar morphology have been implicated in ovine abortions (5, 21) and in intestinal diseases in animals and humans (1, 37).Much of the recent work on spiral bacteria has concentrated on Helicobacter pylori and other Campylobacter-like organisms because of the postulated association of these bacteria with human gastrointestinal disease (6,18,28,29). The taxonomy of this group of organisms is now being clarified. Recent phylogenetic work has resulted in the creation of the genus Helicobacter, and new species of this genus are rapidly being recognized (14, 17,32,33,36,40,43). Although three of the gastric helicobacters are very similar physiologically and show high degrees of similarity (96%) in their 16s rRNA sequences, these bacteria have very different morphologies (19,24,31). H. pylori is a relatively short organism with one or two turns in its spiral body, while Helicobacter musteleae is a short, slightly curved, rodshaped organism with an unusual flagellum configuration. In contrast, Helicobacter felis is 5 to 7 pm long and has a tightly spiralled body with five or six turns; it is entwined with a distinctive series of periplasmic fibers.The distinctive periplasmic fibers are not new to us because 10 years ago we observed similar structures on a bacterium isolated from a rat ileum (34). The same organism * Corresponding author.has been described previously in the elegant electron microscopic studies of Erland...
SUMMARYHorizontal transmission of Campylobacter jejuni was investigated in campylobacter-free broiler chicks. One hundred and twenty chicks housed individually, were provided with water containing 1O2-1O9 c.f.u./ml C. jejuni. Colonization was rapid [47 of 73 (64 %) positive cloacal cultures within 3 days and 65 of 73 (89 %) within 7 days], dependent on C. jejuni strain and inoculum size but independent of chick age. Groups of 5-24 chicks in isolators were exposed to C. jejuni-contaminated water or colonized seeder chicks. Transmission occurred in 2-7 days concurrent with a gradual increase of C. jejuni in litter, water and feed. Environmental samples were culture-negative within 3 days following removal of colonized chicks. Treatment of 1-day-old chicks with adult caecal microbiota did not affect colonization. Treated and control chicks were all C. jejuni-positive within 3 days of seeder challenge.
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