Human Bacteroides Research Articles

Whole-cell and Periplasmic Protein Banding Patterns of Environmental and Human Bacteroides fragilis Strains

In order to investigate the relationship among virulent and avirulent Bacteroides fragilis strains, SDS-PAGE of whole-cell proteins (WP) and periplasmic proteins (PP) were used to establish a protein profile of strains isolated from human infections, fecal flora and environmental water. Despite different sources of the strains, no significant differences were observed as determined by the WP SDS-PAGE analysis. In contrast, the proteins obtained from the bacterial periplasm showed differences in the electrophoretic protein profile. Two distinct PP profile patterns were obtained. Pattern A included 6 out of the 8 virulent strains and pattern B, 6 out of 8 avirulent strains. Interestingly, an environmental strain that was capable of inducing abscesses in mice, had a PP profile highly similar to that of the virulent strains from human infections. These data indicate that PP from B. fragilis may be useful to characterize differences among virulent and avirulent strains. Moreover, strains isolated from environmental water may also be a source of exogenous infections by B. fragilis.

Natural occurrence of black-pigmented Bacteroides species in the gingival crevice of the squirrel monkey.

The objective of this study was to determine whether the squirrel monkey (Saimiri scuireus) is indigenously colonized with black-pigmented bacteroides (BPB) resembling human Bacteroides gingivalis and Bacteroides intermedius (suspected periodontal pathogens) and to determine the usefulness of the squirrel monkey as an in vivo model for studying colonization by putative pathogens. We assayed the subgingival plaques of 138 monkeys of various ages and in four different colonies for the presence of anaerobic BPB microorganisms. We also tested half the animals for the presence of Actinobacillus actinomycetemcomitans. Clinical indices and levels of serum antibody to B. gingivalis were recorded. We detected BPB in 50% of the animals and A. actinomycetemcomitans in 69% of the animals. The presence of BPB was generally associated with increased age, increased gingival index, presence of calculus, and increased levels of serum antibody. These data indicate that the squirrel monkey may be a good model for studying the parameters of natural infection of the gingival crevice with suspected periodontopathogenic BPB microorganisms.

Ultrastructure of Bacteroides species: Bacteroides asaccharolyticus, Bacteroides fragilis, Bacteroides melaninogenicus subspecies melaninogenicus, and B. melaninogenicus subspecies intermedius.

Representative strains of two subspecies of Bacteroides melaninogenicus (subspecies melaninogenicus and subspecies intermedius) and Bacteroides asaccharolyticus as well as B. asaccharolyticus strain 536B isolated from a human perirectal abscess and Bacteroides fragilis ATCC 25285 were examined by glutaraldehyde-osmium fixation, ruthenium red fixation and staining, and thorium hydroxyde staining as well as by the physical preparative techniques of critical point drying--transmission electron microscopy (CPD--TEM) and scanning electron microscopy (SEM). All strains, with the exception of B. fragilis 25285, possessed an electron-dense material external to their outer membranes. Ruthenium red staining further revealed a layer, external to the surface of the outer membrane, that was distinct for each species examined. Thorium hydroxide, as well as CPD--TEM and SEM, showed the cells to be interconnected by thin fibers that not only connected adjacent cells but also traversed several microns to connect cell aggregates.

Fermentations by saccharolytic intestinal bacteria

Most nonsporing anaerobes of the intestinal tract use the Embden-Meyerhof-Parnas scheme to ferment carbohydrates. Almost all of them oxidize pyruvate, the key fermentation intermediate, to acetyl coenzyme A and CO2 with reduction of a low-potential electron acceptor. H2 is formed from the low potential acceptor or from NADH. Pyruvate is a precursor of lactate, and phosphoenolpyruvate is a precursor of succinate and propionate. Ethanol, acetate, and butyrate are formed from acetyl coenzyme A. Formate is produced by reduction of CO2 by Ruminococcus albus. Heme is required by human Bacteroides for the formation of succinate and, in the presence of vitamin B12, propionate. A fermentation equation derived from the concentration of volatile acids found in human feces suggests that the fermentation in the large intestine is similar to the rumen fermentation.

Isolation of Bacterium Typhosum When Mixed With Anaerobic, Non-Spore Forming, Gram-Negative Rods (Bacteroides)

The enormous numbers of anaerobic non-spore forming, gramnegative rods reported in the intestinal contents of man (Sanborn and Eggerth and Gagnon) have not been considered in the routine isolation of pathogenic bacteria, or in the false presumptive tests in water analyses. Bacteroides are small gram-negative or gram-positive rods, some of the gram-negative forms being indistinguishable morphologically from the gram-negative pathogenic bacteria. Although they are strict anaerobes, the possibility that they might find conditions favorable for multiplication in mixed cultures with aerobes was considered in this investigation. Bacterium typhosum (Rawlings) and 2 strains of Bacteroides, one isolated from a colon specimen from man and the other from a monkey colon, were studied. The biochemical reactions of the 2 strains of Bacteroides are listed in Table I. A mixed suspension of these Bacteroides strains and Bacterium typhosum produced acid without gas in lactose broth incubated aerobically. An experiment was performed with the human Bacteroides strain in mixture with Bacterium typhosum. This suspension was plated on endo and eosine-methylene blue agar media and incubated aerobically for 24 hours, after which colonies were picked and put into lactose broth. Bacteroides was demonstrated in a few of these colonies by the production of acid in the lactose broth after 36 hours' incubation. All of the colonies on the plates were colorless and identical with those of a pure culture of the typhoid bacillus, although plates prepared in a similar manner, incubated aerobically for 48 hours and then placed in an anaerobic jar and incubated for 3 days longer, contained some isolated colonies of Bacteroides and some which appeared to be superimposed on the typhoid colonies. A mixed suspension of Bacteroides (monkey strain) and Bacterium typhosum was used for inoculation of 12 freshly prepared veal infusion agar slants.