The genomic fingerprinting of the causative agents of sapronoses

The genome polymorphism of the causative agents of sapronoses (Vibrio cholerae, Legionella and Leptospira) has been studied. The use of the method of genome fingerprinting [correction of dactyloscopy] has been shown to permit the differentiation of closely related strains of such causative agents. The epidemically significant strains of the causative agents of sapronoses, isolated in different geographical regions, have been found to be genotypically related, i.e., they are probably of clonal origin. Avirulent and nontoxigenic strains are genotypically heterogeneous and differ both from one another and from epidemically significant strains. Using V. cholerae as an example, the hypothesis of the appearance of potentially dangerous variants at the epidemic period in the absence of their release at the period between epidemics is considered.     

Effect of penicillin on the intensity of formation of penicillin-resistant staphylococcal populations in the suppurative foci of patients]

The dynamics of sensitivity to penicillin of staphylococcal populations in purulent inflammatory foci of patients treated and not treated with antibiotics was estimated according to 4 indices. No reliable differences in the dynamics of sensitivity to penicillin were found in 2 groups of the patients, when estimation was performed with respect to the frequency of the penicillin resistant or penicillin sensitive staphylococci and detection of the penicillin resistant staphylococci by direct inoculation of the focal excretion to the medium with penicillin. A reliable increase in the percentage of the penicillin resistant staphylococci in the microbial population was observed only in the patients treated with penicillin.     

Determination of toxigenicity of Escherichia coli and Vibrio cholerae strains by radioimmunologic method

A solid phase variant of radioimmunoassay has been elaborated for screening toxin-producing strains of E. coli and V. cholerae grown on agar plates. The method is based on the ability of cholera-like toxins to be absorbed on nitrocellulose filters and their further identification with the use of homologous sera and [125I]-A protein from staphylococci. Sensitivity of the method reaches 20 pg. The proposed technique permits identification of intracellular enterotoxin and is aimed at a massive screening of E. coli strains, NAG-vibrios and V. cholerae strains for toxin production.