Some current concepts in intestinal bacteriology.

Quantitative studies of the fecal flora of populations at different risk of colon cancer indicate that the relative proportions of some particular species of bacteria rather than of different genera of bacteria may be correlated with colon cancer incidence. Since the metabolic activity of different species in each genus varies widely, a shift in proportions of species could cause a major change in total metabolic activity in the individual. In samples taken from various areas of the intestinal tract and in scrapings from the intestinal wall, the composition of the flora remained relatively constant from the ascending colon to the rectum. Therefore, the bacteria in feces do reflect the flora of the large colon. The composition of the flora was not significantly affected by drastic changes in diet, but statistically significant shifts in the proportions of some species were noted in individuals under conditions of anger or fear stress. Although diet may not change the flora the individual maintains, the bacteria present may convert the different substrates provided by a high-fat diet as opposed to a high-fiber diet into metabolites that are potentially carcinogenic. The conversion of dietary components to carcinogenic compounds, identification of the bacteria capable of effecting such conversions, and the conditions favoring the proliferation of such bacteria will be investigated in greater detail.

Bacteriology of human gingivitis.

The subgingival bacterial floras of naturally occurring gingivitis in adults and children were characterized and compared with the floras of other periodontal conditions previously studied. The composition of the gingivitis floras was found to be distinct from that of floras associated with health or with moderate, severe, or juvenile periodontitis. There were no major differences between the floras of naturally-occurring gingivitis and the floras of the human experimental gingivitis model. Data indicated that the flora of healthy sites within a mouth is influenced by the number of inflamed sites, which argues against independence of sites bacteriologically. Proportions of ten bacterial species increased in both gingivitis and periodontitis, as compared with health, in both adults and children. These species were found in both affected and unaffected sites of people with gingivitis. The numbers of five other cultivable species and the "large treponeme", which was not cultivated, increased in gingivitis and periodontitis of adults only. Significant differences in non-spirochetal floras between children and adults were not found, although they were in the experimental gingivitis model studied previously. Cultivable spirochetes did differ between children and adults. Children had fewer samples positive for spirochetes, and children's positive samples contained greater proportions of T. socranskii subsp. paredis. Some species that predominate in periodontitis, but which are absent from healthy gingivae, were found as a small percentage of the flora in gingivitis. This suggests that increased serum and blood in the gingival crevice encourage species that relate to periodontitis.

Taxonomy of anaerobes: present state of the art.

Results of nucleic acid studies, which indicate relationships among strains and species more clearly than do usual phenotypic tests, have led to new bacteriologic nomenclature. Some major changes in Bacteroides include the recognition of three species (Bacteroides melaninogenicus, Bacteroides denticola, and Bacteroides loescheii) formerly grouped in B. melaninogenicus subspecies melaninogenicus; two species (Bacteroides intermedius with two closely related homology groups and Bacteroides corporis) formerly grouped together as B. melaninogenicus subspecies intermedius; and two species (Bacteroides buccae and Bacteroides oris) formerly thought to be human isolates of Bacteroides ruminicola subspecies brevis. Former subspecies of Bacteroides fragilis have been elevated to species rank; and Bacteroides uniformis and an unnamed group ("3452A"), recognized. A new genus, Capnocytophaga, with three species, is composed of strains formerly classified as Bacteroides ochraceus or Centers for Disease Control (CDC) group DF-1. Strains previously thought to be human isolates of "Vibrio succinogenes" and related organisms that derive energy by reduction of fumarate or nitrate with formate or hydrogen have been reclassified in Bacteroides (Bacteroides gracilis), Campylobacter (Campylobacter concisus), or in a new genus, Wolinella.

Electrophoretic study of Clostridium species.

Polyacrylamide gel electrophoretic analysis of soluble cellular proteins (without sodium dodecyl sulfate) of 70 Clostridium species indicated that the procedure was readily applicable to the differentiation of species in the genus. The protein patterns correlated well with the available DNA homology data and with most accepted differential tests. Results indicated that several earlier names for species were synonyms of those of accepted species and that two accepted species may be synonymous.

Polyacrylamide slab gel electrophoresis of soluble proteins for studies of bacterial floras.

A polyacrylamide slab gel electrophoresis procedure was used to compare cellular proteins from bacterial isolates of gingival crevice floras. Isolates with identical protein patterns consistently were shown to be members of the same species. When used to screen isolates, the procedure reduced total analytical time and expense without sacrificing accuracy, and it provided additional verification of the identity of strains characterized by conventional phenotypic tests.

Bacteriology of moderate (chronic) periodontitis in mature adult humans.

A total of 171 taxa was represented among 1,900 bacterial isolates from 60 samples of sites affected with moderate periodontitis in 22 mature adult humans. The composition of the subgingival sulcus flora was statistically significantly different from that of the adjacent supragingival flora and the subgingival flora of 14 people with healthy gingiva, but was not significantly different from that of sulci affected with severe periodontitis in 21 young human adults. The sulcus floras of moderate periodontitis and severe periodontitis shared many of their predominant bacterial species, but there were differences in the relative proportions of some of these species. Similar relationships were found for seven taxa of treponemes that were cultured from the samples.

Effect of high-fiber and high-oil diets on the fecal flora of swine.

Six pairs of pigs were fed a basal diet, a high-fiber diet, and a diet high in corn oil in different sequences to minimize the carry-over effect of diet. After 2 months on each diet, a fecal specimen from each pig was cultured on nonselective medium in roll tubes. Fifty colonies were randomly selected from each fecal sample, and isolates were characterized to identify a representative cross section of the fecal flora. The bacterial composition of the fecal flora differed between basal and high-fiber diets (P = 0.002) and between high-fiber and high-oil diets (P = 0.015). However, the floras were not significantly different between the basal and the high-oil diets (P = 0.135), nor were the floras of the 12 individual pigs (each on all three diets) statistically different (P = 0.103). Only 14 of the 160 observed taxa have been detected in the human fecal flora, and only 159 of 1,871 total isolates (8.5%) were members of described species. The most common isolate was a Streptococcus species similar to that reported by Robinson et al. (I. M. Robinson, S. C. Whipp, J. A. Bucklin, and M. J. Allison, Appl. Environ. Microbiol. 48:964-969, 1984), which was found in 34 of 36 samples and which represented 27.5% of all isolates. Lactobacillus, Fusobacterium, Eubacterium, Bacteroides, and Peptostreptococcus species were the next most common bacteria. Escherichia coli represented 1.7% of all fecal isolates, which is somewhat higher than the 0.1 to 0.6% observed in human feces cultured similarly with prereduced anaerobically sterilized media.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriology of experimental gingivitis in children.

Children are more resistant to gingivitis than are adults. To determine possible differences in their periodontal floras, an experimental gingivitis study, identical in design to one reported earlier with young adults, was conducted with four 4- to 6-year-old children. The incidence of sites that developed gingival index scores of 2 in children was less than one-third of the incidence observed in adults. The composition of the flora of each child was statistically significantly different from that of any other child or adult. The floras of the children as a group were statistically significantly different from those of the adults. Children had 3-fold greater proportions of Leptotrichia species, 2.5-fold greater proportions of Capnocytophaga species, 2.3-fold greater proportions of Selenomonas species, 2-fold greater proportions of bacterial species that require formate and fumarate, and 1.5-fold greater proportions of Bacteroides species. Adults had greater proportions of Fusobacterium, Eubacterium, and Lactobacillus species. Fusobacterium nucleatum, Actinomyces WVa 963, Selenomonas D04, and Treponema socranskii were predominant species that correlated with increasing gingival index scores in both children and adults.

Variation in periodontal floras.

Statistical analyses indicated (i) that the floras of individual samples taken from the depth of sulci with nickel-plated Morse 00 scalers were highly reproducible and representative of the flora present at any given time, (ii) that the different compositions of floras of different people with similar clinical signs were statistically highly significant, and (iii) that floras of different affected sites may differ significantly in some (two of three) people at any one time or may differ from week to week in other people (one of three). Thus the flora composition of individual sites appears to be in dynamic flux, probably in response either to environmental changes or to host responses. There was no evidence that double sampling per se (two single passes with 00 scalers) changed the composition of the flora. Repeat samples taken after 1 week were slightly more similar to the initial samples than were samples taken after 3 weeks.

Comparative bacteriology of juvenile periodontitis.

Statistical comparisons of the floras associated with juvenile periodontitis, severe periodontitis, and moderate periodontitis indicated that differences in the bacterial compositions of affected sites in these populations were not statistically significant. The subgingival flora of affected juvenile periodontitis sites was statistically significantly different from the adjacent supragingival flora and from the subgingival floras of people with healthy gingiva and of children with developing (experimental) gingivitis. However, the subgingival flora of affected juvenile periodontitis sites was not significantly different from the flora of sites with gingival index scores of 1 or 2 in adults with developing (experimental) gingivitis. Of 357 bacterial taxa among over 18,000 isolates, 54 non-treponemal species, 2 treponemal species, and mycoplasma were most associated with diseased periodontal sulci. These species comprised an increasing proportion of the flora during developing gingivitis and constituted over half of the cultivable flora of diseased sites.