[Effect of sisomicin on intestinal microflora and colonization resistance in rats and their offspring]. / Vliianie sizomitsina na sostav kishechnoi mikroflory i kolo- nizatsionnuiu rezistentnos't krys i ikh potomstva.

In experiments with Wistar female rats it was shown that after administration in the form of inhalations (10.87 mg/m3) sisomicin was present in the animal feces in a concentration of 26.6 micrograms/g. Prolonged exposure to the antibiotic during the pregnancy term led to changes in microbiocenosis of the animal large intestine which was observed even a month after the delivery. The progeny of the animals was characterized by the presence of significant numbers of aerobic bacteria resistant to sisomicin and potentially pathogenic gram-negative bacteria including various species of Proteus in the intestine, as well as by higher periods of persistence of Klebsiella indicator strains administered orally.

[Changes in the microbial ecology and morphology of large intestine biofilm in albino rats under the influence of rifampicin]. / Izmenenie mikrobnoi ékologii i morfologii bioplenki tolstoi kishki belykh krys pod vliianiem rifampitsina.

After oral administration in single doses of 40 and 160 mg/kg to Wistar rats rifampicin was detected in 3 hours in the contents of the large intestine The maximum rifampicin concentrations in the feces (120 and 300 micrograms/g) were detected in 24 hours. The antibiotic was present in the animal feces for 6-7 days. The antibiotic administration led to marked changes in microbiocenosis of the large intestine: disappearance of coccal flora, lower quantities of Escherichia and Lactobacillus and lower total quantities of anaerobic bacteria. It was also accompanied by changes in the structure of the typhlon biofilm. By the 28th day after discontinuation of the antibiotic administration (the end of the observation period) the large intestine microflora did not recover completely.

[Evaluation of the antimicrobial action of substances for the setting of hygienic standards]. / Otsenka antimikrobnogo deistviia veshchestv s tsel'iu gigienicheskogo normirovaniia.

The notion of antimicrobial effect threshold as an index of hygienic importance for toxicological estimation of chemotherapeutic agents is grounded by the generally accepted conception of thresholds of substances harmful effect. The methodical means used in determining the antimicrobial effect threshold including the recommended set of the measurable indices of intestinal microflora are discussed.

[Problems of the hygienic standardization of antibiotics]. / Problemy gigienicheskogo normirovaniia antibiotikov.

Some of the results of the development of hygienic standardization of antibiotics are discussed. The main scheme proposed earlier was tested in hygienic investigation of antibiotics of various groups. Separate elements of the scheme were shown to be reliable and approaches to its further improvement were suggested. The trends of promising studies on toxicology of antibiotics aimed at their hygienic standardization are presented.

[Assessment of the reproductive function of white rats exposed to cephalexin by inhalation]. / Otsenka sostoianiia reproduktivnoi funktsii belykh krys pri ingaliatsionnom vozdeistvii tsefaleksinom.

The embryotoxic and teratogenic effects of cefalexin were studied on Wistar albino rats subjected to inhalations of the antibiotic within the whole gravidity term. It was shown that in a concentration of 1.29 mg/m3 cefalexin did not increase the rate of fetus intrauterine death, had no unfavourable effect on the fetus and placenta development and did not induce anomalies in development of the fetus internal organs. The frequency of sensitization in the gravid and nongravid animals was the same. No signs of sensitization were detected in the litter of the rats treated with cefalexin inhalations.

[Colonizing resistance of rats born of animals with experimental dysbacteriosis]. / Kolonizatsionnaia rezistentnost' krys, rodivshikhsia ot zhivotnykh s éksperimental'nym disbakteriozom.

It was shown that long-term oral administration of rifampicin (40 mg/kg) to rats was accompanied by a marked decrease in the number of enterococci and staphylococci in their large intestine. A significant decrease in the number of colibacilli and anaerobic nonsporulating gramnegative bacteria was also observed. Discontinuation of the antibiotic administration resulted in rapid recovery of the intestinal flora with respect to all the indices tested. It was found for the first time that pregany of rats with experimental disbacteriosis was characterized by lowered colon resistance in spite of similarity in the intestinal flora of the experimental and control pregany. This was evident from increased periods of indicator microorganism retention in the animal intestine.

[Experimental study of the effect of rifampicin on the embryogenesis of white rats]. / Eksperimental'noe izuchenie vliianiia rifampitsina na émbriogenez belykh krys.

The embryotoxic and teratogenic effects of rifampicin were studied on Wistar albino rats exposed to the antibiotic inhalations during the whole period of gravidity. It was found that in the concentrations used (6.1 +/- 0.4 and 0.81 +/- 0.08 mg/m3) the antibiotic did not induce any increase in the rate of the fetus intrauterine death or any pronounced anomaly in the fetus development. Still, at higher concentrations there was a decrease in the anthropometric characteristics of the fetus, higher incidence of hemoperitoneum and disorders in liver and renal functions of the 2-month-old progeny. The damaging effect of rifampicin on the fetus should be considered as mediated since it was observed in the presence of disorders in the mother's body (changes in liver and renal function, suppressed phagocytosis).

[Placental permeability for rifampicin]. / O pronitsaemosti platsenty dlia rifampitsina.

Albino rats were exposed to rifampicin inhalations for a prolonged period of time (during gravidity). It was found that the antibiotic penetrated through the placental barrier and its levels in the fetus were proportional to its content in the air inhaled. At later gravidity periods rafampicin absorption in albino rats increased and in parallel its levels in the ovum also increased. The exposure of albino rats to rifampicin inhalations during the whole period of their gravidity in concentrations lower than the Limac (the limit of the acute effect with respect to the general toxic parameters) did not affect the structure of the placenta and its permeability by the antibiotic.

[Comparative study of rifampicin distribution in the body of pregnant and nonpregnant white rats exposed to the antibiotic by inhalation]. / Sravnitel'noe izuchenie raspredeleniia rifampitsina v organizme beremennykh i neberemennykh belykh krys pri ingaliatsionnom vvedenii antibiotika.

When rifampicin was administered to albino rats in the form of inhalations, it was absorbed by the blood and penetrated into various organs, the levels of the antibiotic in the biosubstrates being dependent on its concentration in the inhalation air. Rifampicin distribution in the gravid animals was mainly of the same character as that in the nongravid rats. However, when the animals were exposed to the antibiotic effect during the whole period of the gravidity, a significant increase in the antibiotic levels in the blood and internal organs was observed.

[Comparative toxicity of oxytetracycline and its semisynthetic derivatives, methacycline and doxycycline]. / Sravnitel'naia toksichnost' oksitetratsiklina i ego polusinteticheskikh proizvodnykh metatsiklina i doksitsiklina.

The acute toxicity parameters of oxytetracycline and its semisynthetic derivatives was determined on laboratory animals of various species. The three antibiotics were described as belonging to the group of low toxic compounds according to the classification adopted in industrial toxicology. However, the absolute values of LD50 indicated that doxycycline was 5.6 or 2.8 times more toxic than oxyteyracycline or methacycline respectively. In addition, doxycycline had the most pronounced hepatoxic effect.

[Experimental studies to set hygienic standards for benzylpenicillin in the air of a work area]. / Eksperimental'nye issledovaniia po gigienicheskomu normirovaniiu benzilpenitsillina v vozdukhe rabochei zony.

The character and level of benzylpenicillin toxic effect was studied in accordance with the methodic instruction for performance of the experiments on toxicological estimation and hygienic norms of antibiotics in the air of working areas in production premises. It was shown that the antibiotic was of low toxicity under conditions of a single exposure, did not cumulate and had no local irritating and resorbing effect. It was shown to be an allergen. Prolonged inhalation of benzylpenicillin in a concentration of 14 mg/m3 resulted in reversible changes in the function of the kidneys and liver of the animals, their sensitization and development of pronounced dysbacteriosis of the mouth and intestine mucosa. In a concentration of 1 mg/m3 benzylpenicillin had no general toxic and sensitizing effect but induced reversible changes in the normal autoflora. This allowed the authors to consider the above concentration to be maximum with respect to the antibacterial effect. On the basis of the experiments the maximum permissible norm (MPN) of the aerosol of benzylpenicillin disintegration was recommended at the level of 0.1 mg/m3.

[Experimental study of the embryotropic action of tetracycline]. / Eksperimental'noe issledovanie émbriotropnogo deistviia tetratsiklina

The general toxic and embryotropic effect of tetracycline was studied on unbred pregnant albino rats. The antibiotic was used in concentrations of 1 and 0.1 mg/m3, the maximum permissible concentration (MPC). The animals were exposed to tetracycline inhalation for 20 days of their pregnancy. On the basis of the results it was concluded that tetracycline in the concentration at the level of the MPC, i.e. 0.1 mg/m3 had under the experimental conditions a negative effect on the pregnant animals. In concentrations of 1 and 0.1 mg/m3 it had in addition an embryotropic effect. It was also shown that the pregnant animals were more sensitive to the antibiotic than the non-pregnant ones.