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In order to study a possible etiological relationship between Clostridium and diarrhea in children of the first half year of life and to characterize the colonization of the intestine with these bacteria, bacteriological investigations of feces were carried out in neonates and babies aged 1, 4 and 14 days and 1, 3 and 6 months. The development of the children and their health status were monitored under home conditions. It has been established that the colonization of the neonates' intestine with Clostridium including C. Difficile occurs within the early times (since the 4th day of life). Later the colonization with C. difficile becomes wavy in nature. Among 7 types of Clostridium isolated from the intestine of the children, C. difficile occurred most frequently (29.1%). The overwhelming majority of the strains of these bacteria produced toxin whose activity did no exceed 10(-1)-10(-2). The cytopathic effect was mostly demonstrable in 72 hours. No convincing evidence was obtained about the etiological importance of C. difficile in the development of diarrhea in the children placed under observation. It is likely that the latter one was due to the disturbance of intestinal biocenosis, that manifested by profound quantitative disorders (proliferation of the opportunistic aerobic flora, a dramatic reduction of the content of bifido- and lactic acid bacteria up to their complete absence). At the same time a great number of children carrying C. difficile attests to a potential development of specific diarrheas (under hospital conditions and during massive antibacterial therapy).

The results of the comparative study of different substrates prepared from foodstuffs and inedible raw materials and intended for use as the nutrient base of a medium for cultivating the organisms of the genera Bacteroides and Fusobacterium have demonstrated that commonly used nutrient bases prepared from meat, fish, casein and inedible animal blood (blood substitutes) are suitable for this purpose. The dried nutrient base prepared from the mixture of outdated blood substitutes (hydrolysin and casein hydrolysate) (see text for Russian letters) has been found to ensure the optimum growth of Bacteroides and Fusobacterium.

The improved technique of cultivation allowed to detect obligatorily anaerobic microorganisms in 58 out of 94 samples from patients with purulent inflammatory processes. The results of the studies showed that anaerobic microorganisms were most frequently isolated from the exudate of the abdominal cavity and the purulent discharge of wounds in peritonitis patients. Gram-negative nonsporulating bacilli made up 25.3% of all the isolated cultures. The identification of these microorganisms allowed to determine that in the exudate of the abdominal cavity, the discharge of surgical and posttraumatic wounds, and of the pleural cavity the representatives of the family Bacteroidaceae mainly occurred. Most frequently B. thetaiotaomicron and B. fragilis were isolated.

The comparative study of the specific composition of bacteroids isolated from the intestine of healthy persons and from clinical material obtained from patients with different purulent inflammatory diseases has been carried out. This study has revealed that in the former case the prevalent bacteroid species are B. vulgatus and B. distasonis and in the latter case, B. thetaiotaomicron and B. fragilis.

Experiments on the intraperitoneal infection of F1 (CBA X C57BL/6) mice with bacteroids of the group Fragilis in combination with E. coli have revealed the presence of a synergic effect leading to more pronounced (greater frequency of abscess formation) and even qualitatively new (necrotic lesions of the liver) pathological changes in comparison with those observed in monoinfections. Bacteroides fragilis strain 1/1087 gamma has been shown to have greater virulence than that of Bacteroides vulgaris strain 18; their virulence was determined from the capacity of microorganisms for survival in the abdominal cavity of mice, as well as from their capacity for inducing the formation of necrotic lesions and abscesses.

The interrelations of the population of microorganisms belonging to the genus Bacteroides with the structures of the mucous membrane of the gastrointestinal tract of germ-free guinea pigs and mini-pigs have been studied. A considerable part of the population of these anaerobic microorganisms is associated in some way with the intestinal mucosa; at least, quite a number of these organisms inhabit mucins covering the mucosa. The determination of this ecological niche occupied by bacteroids in the intestinal microbiocenosis suggests that these organisms have considerable influence on the physiological functions and pathological states of the digestive tract.

A review of methods for determination of sensitivity of nonsporulating anaerobic bacteria to antibacterial drugs with paper disks is presented and the prospects for using the method of cultivation in solid media in Petri dishes under a polymer film are discussed. It is shown that cultivation at a temperature of 42 degrees C for obtaining earlier results instead of the temperature of 37 degrees C usually used for cultivation has no advantages. With an account of the result variability depending on the inoculation dose and other factors it is necessary to determine the boundary values of the growth inhibition zones for resistant, moderate sensitive and sensitive strains with respect to every antibiotic.

Three variants of the procedure for determination of antibiotic sensitivity in anaerobic microorganisms with the use of standard paper discs were developed. According to the first variant the solid nutrient medium is melted at 46 degrees C and mixed with the culture of the microbe being tested. The mixture is added to the cover of a Petri dish. When the medium becomes solid, antibiotic sensitivity discs are placed onto the agar surface. After that one more layer of the medium is added. The medium is allowed to solidify and some more medium is poured near the cover edge. Immediately after that the Petri dish is placed with its flat surface onto the agar layer in its cover. According to the first and second variants the mixture of the medium and culture is added to a Petri dish and immediately a transparent gas-proof polymer film of the dish size is placed onto the agar surface. Previously antibiotic paper discs or solutions are fixed on the films. THe incubation temperature for all three variants is 37 degrees C. The procedure allows one to observe the culture growth and to obtain the results earlier than in case the culture is incubated in an aerostate. The procedure is simple and saves labor and time.

The method requiring the use of a semi-liquid medium with the reduced content of protein hydrolysates and with bromo-thymol blue added as indicator and permitting the determination of sugar fermentation by bacteroids and fusobacteria is presented. The determination is made by a change in the color of the indicator and the intensity of microbial growth (opacity) after the incubation of the inoculated medium under free access of air. A study has been made for comparing the above method with the electrometric method for the determination of fermentative features in anaerobic microorganisms.