[Enhancement of treatment efficacy in experimental plague by the sequential administration of antibiotics]. / Povyshenie éffektivnosti lecheniia éksperimental'noi chumy putem posledovatel'nogo vvedeniia antibiotikov.

It was shown that the use of ampicillin, azlocillin or polymyxin 24 or 96 hours after the plague infection at the background of the every-day use of rifampicin in the doses protecting only 30 per cent of the animals from death provided 80-100-percent survival of the animals. With the every-day use of ampicillin, azlocillin or polymyxin in succession with rifampicin there was observed a 3-fold increases in the survival of the albino mice as compared to those exposed to an analogous dose of rifampicin alone. A decrease in the number of administrations of the above drugs and an increase in the intervals between the administration also resulted in a significant rise of the animal survival in comparison with that after the every-day use of a similar dose of rifampicin.

[A method of sequential administration of antibiotics in preventive treatment of experimental plague in albino mice]. / Metod posledovatel'nogo vvedeniia antibiotikov v predupreditel'nom lechenii éksperimental'noi chumy belykh myshei.

Combination of a betalactam antibiotic (ampicillin or azlocillin) or polymyxin B with rifampicin were studied with their administration in succession at various intervals in an experimental model of plague infection of albino mice. It was shown that when the administration of the betalactams or polymyxin B preceded the administration of rifampicin, the efficacy of the preventive therapy considerably increased. The time of the intervals was noted to be of importance and should be predetermined for every subsequent administration.

[Detoxifying effect of antibiotics and their effectiveness in experimental plague at the stage of explicit intoxication]. / Detoksitsiruiushchee deistvie antibiotikov i ikh éffektivnost' pri éksperimental'noi chume na stadii vyrazhennoi intoksikatsii.

The effect of antibiotics such as amikacin, rifampicin, doxycycline, polymyxin B and cefotaxime on the toxins of the plague microbe (lipopolysaccharide + fraction II according to Beiker) was studied in vitro and in vivo. The study on the antibiotic neutralization of plague toxins revealed that only polymyxin had toxin neutralizing capacity which depended on the dose. Investigation of the polymyxin effect at various stages of plague infection showed that when polymyxin in a dose of 1250 units and a mixture of plague toxins in lethal doses were administered simultaneously to albino mice, the positive effect amounted to 100 per cent. When the antibiotic was administered 30 or 60 minutes later, the antibiotic efficacy proved to be lower by 90 or 76.6 per cent, respectively. The intoxication in later periods (in 90-120 minutes) resulted in a decrease in animal survival up to 40-15 per cent. It was demonstrated on the model of the plague infection in albino mice that the use of amikacin, cefotaxime, rifampicin or doxycycline during polymyxin therapy at the stage of marked generalization of the infection provided a significant increase in the animal survival (60 to 80 per cent) as compared to that after the use of the same drugs alone (0 to 20 per cent).

[The lytic activity of Yersinia pestis phage P 3d serovar]. / Liticheskaia aktivnost' faga Yersinia pestis P 3-go serovara.

The lytic activity of plague phage II, serovar 3, with respect to 1,800 bacterial strains has been studied: 760 Yersinia pestis strains, 262 Y. pseudotuberculosis strains, 252 Y. enterocolitica strains, 166 Escherichia coli strains, 90 Shigella strains and 270 strains of other species. The phage has been found to lyse 81.8% of Y. pestis strains, 1 Y. pseudotuberculosis strain and 1 Y. enterocolitica strain. The representatives of other 19 bacterial species have proved to be resistant to the phage. Though having a wide range of action within Y. pestis, the phage does not lyse most of the strains of the causative agent of plague, isolated in certain natural foci. This fact offers promise for using the phage for the differentiation of Y. pestis.