Intracellular polysaccharide of Bacteroides fragilis.

Formation of iodophilic polysaccharide (IPS) from glucose was demonstrated in 27 strains of Bacteroides fragilis. Synthesis was dependent on the glucose concentration of the medium, the pH and the growth phase. When glucose was in short supply the cellular polysaccharide was degraded rapidly at pH 4.5 to 6.5 and fatty acids accumulated in the medium. Storage of IPS was not responsible for the low carbon recoveries observed in fermentation balance studies. In electron micrographs of thin sections, the IPS was observed as cytoplasmic granules dispersed throughout the whole cell. After extraction and purification the IPS was characterized as a glycogen.

Composition and ecology of the human intestinal flora.

Longitudinal quantitative cultures of fecal flora of 20 newborns, 4 older babies and 10 healthy adults were carried out to study the composition and development of the intestinal flora. In all newborns the same sequence of colonization was observed. The numbers of aerobic and anaerobic bacteria fluctuated and reached finally numbers of 10(10)/g wet weight. In adults the flora was in balance with 10(5)-10(7) aerobic and 10(10)-10(11) anaerobic bacteria/g wet weight. Interaction experiments in vitro showed growth inhibition of Bacteroides fragilis by all intestinal species isolated. Bifidobacteria were not inhibited. The assumption was made that this type of interaction could be one of the mechanisms involved in the intestinal micro-ecology. Three of the Bacteroides fragilis strains tested were able to grow on "natural intestinal substrates" as gastric mucin, glycogen and a variety of plant polysaccharides. Acetic, lactic, propionic and succinic acids were detected as fermentation products.

Reaction of the vaginal flora to ornidazol in patients with cervicitis.

The cervical and high vaginal flora of 76 patients with cervicitis were studied before and after therapy with Ornidazol by quantitative culture methods. Lactobacilli were the predominant organisms, but Peptostreptococci, Bacteroides and Trichomonas were encountered in 17, respectively 32 and 81% of all specimens. During and after therapy Trichomonas disappeared completely, the bacterial flora normalized and became comparable to that of healthy women with incidences for Bacteroides of 8-13% and Peptostreptococci of 4-5%. The in vitro susceptibility (MIC and MBC) of 50 strains of Bacteroides to Ornidazol was determined by a broth dilution method and an agar plate technique. The MIC varied from 0.07 to 10 microgram/ml. All strains were susceptible to 10 microgram/ml. There was a slight variation in resistance between the various species tested. B. fragilis was less susceptible to Ornidazol than other Bacteroides species. Within the species B. fragilis the subspecies thetaiotaomicron and 'other' were most susceptible, spp. fragilis and spp. distasonis least.

Quantitative gas chromatography of Bacteroides species under different growth conditions.

From 56 strains of strictly anaerobic gram-negative rods isolated from stool and purulent lesions the fermentation products in the presence and absence of hemin were determined by quantitative gas-solid chromatography, using a simple and more rapid chromatographic procedure. With hemin the fermentation products were propionic, acetic, lactin and succinic acid. Without hemin no or little succinic acid was formed and the main products were lactic and acetic acid. In both groups the distribution of subspecies was determined and the production of fatty acids measured quantitatively. Fourteen strains of the lesion group showed a higher metabolic activity, resulting in an increased total acid production caused by an excessive production of acetic and lactic acid. This characteristic is probably a virulence factor in these strains. All strains were protoporphyrin- and oxgall-dependent. It is postulated that these substances are used for the production of cytochromes which permits the formation of succinic acid by a fumarate reductase resulting in an increased growth rate and growth yield.