RESUMEN

A gram-positive, rod-shaped anaerobe (strain F-6) was isolated from soil. This organism was identified by cellular morphology as well as fermentative and biochemical data as Clostridium bifermentans. Strain F-6 formed 7-ketolithocholic acid from chenodeoxycholic acid and 7-ketodeoxycholic acid from cholic acid in whole cell cultures, but did not transform deoxycholic acid, ursodeoxycholic acid, or ursocholic acid. This reaction is reversible. The structures of 7-ketolithocholic acid and 7-ketodeoxycholic acid were verified by mass spectroscopy and by thin-layer chromatography using Komarowsky's spray reagent. When incubated with the strain F-6 glycine and taurine conjugates of the primary bile acids were partially hydrolyzed and transformed to 7-keto products. Optimal yields of 7-ketolithocholic acid and 7-ketodeoxycholic acid were obtained after 78 h of incubation. Culture pH changed with time and was characterized by an initial drop (1.1 pH units) and a gradual increase back to the starting pH (7.3). Corroborating these observations, an inducible, NADP-dependent, 7 alpha-hydroxysteroid dehydrogenase was demonstrated in cell extracts of strain F-6. A trace of NAD-dependent 7 alpha-hydroxysteroid dehydrogenase was also found. A substantial increase in the specific activity of the NADP-dependent 7 alpha-hydroxysteroid dehydrogenase was observed when either 7-ketolithocholic acid, chenodeoxycholic acid, or deoxycholic acid was included in the growth medium. Optimal induction of the NADP-dependent 7 alpha-hydroxysteroid dehydrogenase was achieved with 0.3-0.4 mM 7-ketolithocholic acid. Production of the enzyme(s) was optimal at 6-8 h of growth and the 7 alpha-hydroxysteroid dehydrogenases had a pH optimum of approximately 11.(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

Asunto(s)

RESUMEN

Seventy-three freshly isolated oral strains representing 10 Bacteroides spp. were tested for their ability to coaggregate with other oral gram-negative and gram-positive bacteria. None coaggregated with any of the gram-negative strains tested, which included Capnocytophaga gingivalis, C. ochracea, C. sputigena, and Actinobacillus actinomycetemcomitans. Strains of Bacteroides buccae, B. melaninogenicus, B. oralis, and B. gingivalis failed to coaggregate with any of the gram-positive strains tested. However, six Bacteroides spp. coaggregated with one or more species of gram-positive bacteria. Most isolates of B. buccalis, B. denticola, B. intermedius, B. loescheii, B. oris, and B. veroralis coaggregated with strains of Actinomyces israelii, A. viscosus, A. naeslundii, A. odontolyticus, Rothia dentocariosa, or Streptococcus sanguis. The strongest coaggregations involved B. denticola, B. loescheii, or B. oris; 22 of 25 strains coaggregated with A. israelii. Only B. loescheii interacted with certain strains of S. sanguis; these coaggregations were lactose inhibitable and were like coaggregations between A. viscosus and the same strains of S. sanguis. In fact, B. loescheii and A. viscosus were competitors for binding to S. sanguis. Many bacteroides also acted as coaggregation bridges by mediating coaggregations between two noncoaggregating cell types (e.g., S. sanguis and A. israelii). Evidence for binding-site competition and coaggregation bridging involving noncoaggregating cell types from three different genera provides support for the hypothesis that these intergeneric cell-to-cell interactions have an active role in bacterial colonization of the oral cavity.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

A gram-positive, rod-shaped anaerobe (isolate F-14) was isolated from soil. This organism was identified by cellular morphology as well as by fermentative and biochemical data as Clostridium limosum. Isolate F-14 formed ursocholic acid (UC) and 7-ketodeoxycholic acid (7-KDC) from cholic acid (CA), and ursodeoxycholic acid (UDC) and 7-ketolithocholic acid (7-KLC) from chenodeoxycholic acid (CDC) in whole cell cultures, but did not transform deoxycholic acid (DC). No hydrolysis or transformation occurred when either taurine- or glycine-conjugated bile acids were incubated with F-14. The type stain of Clostridium limosum (American Type Culture Collection 25620) did not transform bile acids. The structures of ursocholic, ursodeoxycholic, 7-ketodeoxycholic, and 7-ketolithocholic acids were verified by mass spectroscopy and by thin-layer chromatography using Komarowsky's spray reagent. The organism transformed cholic and chenodeoxycholic acids at concentrations of 20 mM and 1 mM, respectively; higher concentrations of bile acids inhibited growth. Optimal yields of ursocholic and ursodeoxycholic acids were obtained at 9-24 hr of incubation and depended upon the substrate used. Increasing yields of 7-ketodeoxycholic and 7-ketolithocholic acids, and decreasing yields of ursocholic and ursodeoxycholic acids were observed with longer periods of incubation. Culture pH changed with time and was characterized by a small initial drop (0.2-0.4 pH units) and a subsequent increase to a pH (8.1-8.2) that was above the starting pH (7.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

RESUMEN

A hitherto unknown species of Clostridium, provisionally designated strain 19, was isolated from the fecal flora of a healthy human adult. This strain synthesizes a constitutive desmolase that cleaves the side chain of cortisol to form 11 beta-hydroxy-4-androstene-3,17-dione. The enzymatic conversion is best demonstrated in supplemented peptone broth and in prereduced brain-heart infusion broth. The fecal concentration of strain 19 is 10(7)-10(8) cells/g. The strain adapts with difficulty to growth on Mueller-Hinton agar and Columbia agar base; colony formation is enhanced by the addition of 5% sheep blood. The organism is sensitive to penicillin G and resistant to tetracycline, chloramphenicol, clindamycin, and erythromycin.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

A fecal isolate, Streptococcus sp. strain FRP-17, and strain VGH-1 of Streptococcus faecium were shown to contain beta-glucosidases which converted rutin (quercetin-3-O-beta-D-glucose-alpha-L-rhamnose) to quercetin and were active against o-nitrophenyl-beta-D-glucose. The activity against rutin could be measured by increased mutagenicity in the Ames assay or visualized on thin-layer chromatography plates. In both organisms, the beta-glucosidase activities were inducible by the addition of rutin to the growth media. Several closely related strains of Streptococcus spp. lacked any beta-glucosidase activity. In cell preparations of the active organisms, activities with rutin and o-nitrophenyl-beta-D-glucose were optimal at pH 6.8 and could be enhanced by increasing the ionic strength of the assay system. At low ionic strengths, both quercetin and a new product (intermediate between the polarities of rutin and quercetin) were formed by the incubation of rutin with cell preparations of either active organism. This product disappeared with increased ionic strength, suggesting that it may be a reaction intermediate, quercetin-3-O-beta-D-glucose. These results suggest that the beta-glucosidase active against rutin and that active against o-nitrophenyl-beta-D-glucose are the same.

Asunto(s)

RESUMEN

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.

Asunto(s)

RESUMEN

The coaggregation properties of recent human oral streptococcal and actinomyces isolates from the same site were determined and compared with the coaggregation properties of well-characterized stock strains of these two kinds of bacteria. Streptococcus sanguis, Actinomyces viscosus, Actinomyces naeslundii, and phenotypically similar strains of actinomyces were isolated from subgingival samples from periodontally healthy older individuals, from persons participating in an experimental gingivitis study, and from young persons with localized (juvenile) and generalized (severe) periodontitis. All 34 of the actinomyces isolates coaggregated with reagent strains of S. sanguis that represented the four streptococcal coaggregation groups. Most of these actinomyces exhibited coaggregations identical to those of actinomyces stock strains. However, five isolates of an Actinomyces WVa-963 serovar exhibited a coaggregation pattern different from any previously described, which was used to define coaggregation group F. All coaggregations with members of this group were lactose inhibitable. Only 57% (8 of 14) of the recent S. sanguis isolates coaggregated with actinomyces reagent strains. But when the nonreactive streptococcal isolates were tested for their ability to coaggregate with actinomyces from the same patient, a new, highly specific coaggregation pattern (group 6) for S. sanguis was discovered. Coaggregation of these streptococci was observed only with certain isolates of A. naeslundii (members of coaggregation group D) from the same site, and none of these coaggregations were inhibited by lactose. Subsequent testing revealed that streptococci of group 6 coaggregated with group D actinomyces from other sources but not with actinomyces of other coaggregation groups. Only two strains of S. sanguis failed to coaggregate with any strain of actinomyces tested. These results indicate that nearly all fresh isolates of these species obtained from both diseased and healthy sites exhibit specific, nonrandom patterns of coaggregation and suggest the widespread occurrence of in vivo cell-to-cell recognition between oral actinomyces and streptococci.

Asunto(s)

RESUMEN

DNA was purified from 16 strains of Fusobacterium nucleatum and from five strains representing other Fusobacterium species. The relationships among fusobacteria were examined by DNA-DNA hybridization and by determining the guanine plus cytosine content of the DNA. F. nucleatum was found to comprise a heterogenous group of organisms related to Fusobacterium periodonticum and Fusobacterium simiae, but unrelated to any of the other species of Fusobacterium tested.

Asunto(s)

RESUMEN

Necrotic hepatitis resembling black disease of ruminants is described in a group of five water snakes (Natrix sipedon pictiventirs). Lesions varied from multifocal granulomas to massive coagulation necrosis. A bacterium recovered from the livers could not be classified, but closely resembled Eubacterium tarantellus. The bacterium was isolated from all snake livers and from snake mites (Ophionyssus natricis) which were probably implicated in the transmission of the disease and it is possible that trematodes were concerned in producing the initial damage to the liver.

Asunto(s)

RESUMEN

Thirty-four strains representing 15 species of anaerobic bacteria were screened for acetone, isopropanol, and n-butanol (solvent) production. Under our culture conditions, several strains of Clostridium beijerinckii and C. aurantibutyricum produced at least 40 mM n-butanol (C. acetobutylicum strains produced up to 41 mM n-butanol under similar conditions). Both solvent-producing and non-solvent-producing strains of C. beijerinckii have high DNA homology with a reference strain of C. beijerinckii. Strains labeled "Clostridium butylicum" are phenotypically similar to C. beijerinckii and showed at least 78% DNA homology to a reference strain of C. beijerinckii. Therefore, these "C. butylicum" strains are members of C. beijerinckii. An earlier DNA homology study has shown that C. beijerinckii, C. aurantibutyricum, and C. acetobutylicum are distinct species.

RESUMEN

An anaerobic continuous-flow (CF) culture method has been developed which reproduces a number of bacterial interactions that occur in the large intestine of mice. These were determined in the following ways. (i) Bacterial counts in smears stained with 37 specific fluorescent antisera showed that the numeric balance between 37 strict anaerobes isolated from conventional mice was maintained in CF culture of conventional mouse flora in the same manner as in conventional mice. (ii) Mixed populations of various complexity of bacteria isolated from conventional mice were able to suppress Escherichia coli populations to similar levels in gnotobiotic mice and in CF cultures. (iii) Contents of CF cultures when fed to germfree mice were found to redress the germfree abnormalities studied, namely, cecal size and size of the E. coli population. Furthermore, dense layers of bacterial growth formed on the wall of CF cultures of mouse cecal flora, in a manner analogous to the colonization of mouse large intestinal mucosa. In the absence of such bacterial layers, the culture no longer exhibited these interactions. Because of the complexity and diversity of the interactions studied it is highly probable that at least the major underlying ecological control mechanisms operating in the culture model resemble those of the mouse intestine. We speculate that the somewhat surprising similarity between the ecology of the mouse large intestine and that of a CF culture in a glass vessel is due to the fact that both are dominated by thick layers of complex bacterial flora, the composition of which is controlled by their metabolic activities and by their relative ability to adhere to each other.

Asunto(s)

Asunto(s)

RESUMEN

A total of 78 bacteriological samples were taken from the supragingival tooth surface after superficial cleaning with toothpicks or from the periodontal sulci of 42 affected sites in 21 adolescents or young adults with severe generalized periodontitis. Of 190 bacterial species, subspecies, or serotypes detected among 2,723 isolates, 11 species exceeded 1% of the subgingival flora and were most closely associated with the diseased sulci. Eleven others were also sufficiently frequent to be suspect agents of tissue destruction. Many of these species are known pathogens of other body sites. In addition, 10 species of Treponema were isolated. One of these and the "large treponeme" were also more closely associated with severe periodontitis than they were with healthy sites or gingivitis. There were highly significant differences between the composition of the flora of the affected sulci and the flora of (i) the adjacent supragingival tooth surface, (ii) the gingival crevice of periodontally healthy people, and (iii) sites with a gingival index score of 0 or 2 in experimental gingivitis studies. The floras of different individuals were also significantly different. There was no statistically detectable effect of sampling per se upon the composition of the flora of subsequent samples from the same sites. The composition of the supragingival flora of the patients with severe generalized periodontitis that had serum antibody to Actinobacillus actinomycetemcomitans was significantly different from the supragingival flora of patients without this serum antibody. However, there was no statistically significant difference in the composition of their subgingival floras.

Asunto(s)

RESUMEN

From replicate trials of experimental gingivitis in four periodontally healthy subjects, 166 bacterial species and subspecies were detected among 3,034 randomly selected isolates from 96 samples. Of these bacteria, Actinomyces naeslundii (serotype III and phenotypically similar strains that were unreactive with available antisera), Actinomyces odontolyticus (serotype I and phenotypically similar strains that were unreactive with available antisera), Fusobacterium nucleatum, Lactobacillus species D-2, Streptococcus anginosus, Veillonella parvula, and Treponema species A appeared to be the most likely etiological agents of gingivitis. Statistical interpretations indicated that the greatest source of microbiological variation of the total flora observed was person-to-person differences in the floras. The next greatest source of variation was the inflammatory status of the sample sites. Person-to-person differences were smallest at experimental day 4. The floras became more diverse with time and as gingivitis developed and progressed. Analyses indicated that sequential colonization by certain species was repeatable and therefore probably predictable. Variation was relatively small between replicate trials, between two sites on the same teeth sampled on the same day, and between the same sites sampled at the same relative time in a replicate trial.

Asunto(s)

RESUMEN

A gram-positive, anaerobic, chain-forming, rod-shaped anaerobe (isolate G20-7) was isolated from normal human feces. This organism was identified by cellular morphology as well as fermentative and biochemical data as Eubacterium aerofaciens. When isolate G20-7 was grown in the presence of Bacteroides fragilis or Escherichia coli (or another 7 alpha-hydroxysteroid dehydrogenase producer) and chenodeoxycholic acid, ursodeoxycholic acid produced. Time course curves revealed that 3 alpha-hydroxy-7-keto-5 beta-cholanoic acid produced by B. fragilis or E. coli or introduced into the medium as a pure substance was reduced by G20-7 specifically to ursodeoxycholic acid. The addition of glycine- and taurine-conjugated primary bile acids (chenodeoxycholic and cholic acids) and other bile acids to binary cultures of B. fragilis and G20-7 revealed that (i) both conjugates were hydrolyzed to give free bile acids, (ii) ursocholic acid (3 alpha, 7 beta, 12 alpha-trihydroxy-5 beta-cholanoic acid) was produced when conjugated (or free) cholic acid was the substrate, and (iii) the epimerization reaction was at least partially reversible. Corroborating these observations, an NADP-dependent 7 beta-hydroxysteroid dehydrogenase (reacting specifically with 7 beta-OH-groups) was demonstrated in cell-free preparations of isolate G20-7; production of the enzyme was optimal at between 12 and 18 h of growth. This enzyme, when measured in the oxidative direction, was active with ursodeoxycholic acid, ursocholic acid, and the taurine conjugate of ursodeoxycholic acid (but not with chenodeoxycholic, deoxycholic, or cholic acids) and displayed an optimal pH range of 9.8 to 10.2

Asunto(s)