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The capacity of leptospiras to get acclimated in the organism of unusual hosts has been studied. Cultures of Icterohaemorrhagiae from musquashes, house mice and field voles have been isolated of leptospirosis sources under intensive epizootics among rats. A possibility to reproduce Leptospira carrying by the cultures of leptospirae of serogroup icterohaemorrhagiae in musquashes and water voles has been shown. One can conclude that under icterohemorrhagic leptospirosis musquashes and water voles can take the part of additional source of infection but they cannot independently preserve leptospirae in nature as a biological species grey rats being their main hosts.

It was shown that the cultures of Pseudomonas aeruginosa were sensitive to 75-100 micrograms/ml and resistant to 25-50 micrograms/ml of carbenicillin when tested by the method of serial dilutions in the synthetic medium developed by the authors and in Jorgensen's medium. The cultures were incubated for 4 and 16 hours, respectively. The data did not confirm the resistance of the cultures to 25-75 and 100 micrograms/ml carbenicillin when it was determined with the serial dilution method in Pal's medium and the disk diffusion method, respectively. The advantages of the medium developed by the authors for testing P. aeruginosa sensitivity to carbenicillin are discussed.

Bacterial suspensions of cultures (10(7) PFU) of pathogenic Staphylococcus, vulgar Proteus and pyocyanic bacterium are resistant to 2.9-46.87 mg per disc of iodopyron in 100% of cases. Sensitivity of 32 and 100% of cultures of pyocyanic bacteria (of 25 under study) being in the suspension (10(5) PFU) to 11.71 and 23.43-9.375 mg of idopyron, respectively, in a hole has been established. To determine sensitivity of pyocyanic bacteria to iodopyron it is suggested to use the procedure of adding of 11.71 mg of the preparation (water solution) to the holes in MPA.

Sensitivity to antibacterial drugs of 510 strains of Shigella Newcastle isolated from both sporadic patients and cases during the disease outbreaks was studied. The studies revealed a rather high percentage of Shigella Newcastle resistant to the antibiotics widely used in clinical practice. Most of the strains, i.e. 90.5 per cent were resistant to tetracycline and a significant number of the isolates, i.e. 55.6--53.3 per cent were resistant to streptomycin and erythromycin. A statistically reliable predominance of the Shigella resistant to levomycetin and streptomycin in the disease foci was noted as compared to the Shigella isolated from the sporadic patients. Most of the isolates were simultaneously resistant to several antibiotics. Thus, resistance to 2,3--4 and 5--6 antibiotics was found in 28, 54.3 and I.I per cent of the cultures respectively. At the same time almost all Shigella Newcastle strains were sensitive to rifampicin, neomycin and monomycin (aminoglycoside antibiotics), enteroseptol (oxychinoline drug) and furazolidone (nitrofuran drug).

For rational antibiotic therapy of patients with persisting bacterial infections, the routine determination of antibiotic resistance in the microorganisms may be insufficient. In this case estimation of the total bactericidal activity of the antibacterial drugs and sera against the causative agents is required. It was shown experimentally that in the presence of human blood sera sensitivity of the P. mirabilis strains to benzylpenicillin, ampicillin, gentamicin, kanamycin and cephaloridin increased, the sensitivity to rifampicin varied and the sensitivity to chloramphenicol and nalidixic acid lowered. The quantitative indices of the sensitivity depended on the biological properties of the strains. The bactericidal activity of the human blood sera lowered under the action of nalidixic acid, chloramphenicol and rifampicin, with the concentrations of the antibacterial drugs being equal to those attained in the blood of patients during chemotherapy. A method for determination of the bactericidal activity of human blood sera in the presence of the antibacterial drugs with the use of P. mirabilis is described. The method is relatively simple and provides satisfactory coincidence of the results indicative of the nonspecific resistance of the blood. This allows the physician to choose the rational antibiotic therapy.

Resistance to antibiotics and sulfanilamides was determined in enterobacteria (E. coli, Pr. mirabilis, Sh. sonnei, Sh. flexneri) isolated from children with intestinal disorders. Elimination of the resistance determinants in polyresistant strains, conjugation of R plasmids (75 per cent in Pr. mirabilis, 70 per cent in E. coli, 78 per cent in Sh. sonnei, 69 per cent in Sh. flexneri), mobilization of nonconjugative plasmids on triple crossing and capacity of R plasmids for repression of the F-factor functions were studied. The data of the study are evident of the plasmid background in enterobacteria isolated from children with intestinal disorders and confirm the plasmid nature of the resistance in the predominating number of the strains. It is suggested that Proteus plays a significant role in the prevalence of plasmid resistance among enterobacteria.