[The biological properties of Salmonella strains isolated from adult patients at different seasons of the year]. / Biologicheskie svoistva shtammov sal'monell, vydelennykh ot vzroslykh bol'nykh v razlichnye sezony goda.

Biological properties of Salmonella strains, isolated in different seasons from patients with the corresponding disease of moderate severity, were compared. Their morphological, biochemical, serologic properties, sensitivity to antibiotics, capacity for synthesizing O-antigen, as well as their virulence for experimental animals, have been studied. Seasonal changes in the virulence of Salmonella strains have been established: the strains isolated in autumn have proved to be more virulent than those isolated in winter. In winter the isolation rate of Salmonella strains resistant to the therapeutic doses of antibiotics is significantly higher than in other seasons. In spring and summer Salmonella O-antigen is synthesized more intensively.

[Enterotoxigenicity and neuraminidase activity of bacteria of the genus Citrobacter]. / Enterotoksigennost' i neiraminidaznaia aktivnost' bakterii roda Citrobacter.

The data obtained in the study of Citrobacter strains isolated from patients with diarrheal diseases and from healthy persons are presented: enterotoxigenicity was studied in 68 strains, while neuraminidase activity in 41 strains. Among the strains of these groups 9 strains with active enterotoxin and 2 strains producing active neuraminidase were detected. The criteria for subdividing Citrobacter strains according to the activity of their thermolabile enterotoxin are proposed.

[Biological properties of the causative agents of salmonellosis in young children]. / Biologicheskie svoistva vozbuditelei sal'monelleza u detei rannego vozrasta.

The study of the biological properties of 161 Salmonella strains isolated from the feces and faucial mucus of 121 young children revealed that at the initial period of salmonellosis the occurrence of Salmonella strains in these materials was the same. Salmonella strains sensitive to antibiotics, as well as group C salmonellae, were shown to be capable of causing hospital infections. Statistically significant results revealed that Salmonella strains isolated from the nasopharynx were more virulent than those isolated simultaneously from the feces of the same children.

[Various aspects of competitive relationship between Shigella and Escherichia coli]. / Nekotorye storony konkurentnykh otnoshenii mezhdu Shigellami i E. coli.

One of the aspects of antagonistic relations could be the competence of microorganisms for specific sites of attachement to the epithelium common for shigellae and some E. coli serological types; this was demonstrated on a model of shigella-induced keratoconjunctivitis and in experiments with the HEp-2 cells infected with H3-glucose-labeled Sh. flexneri 5a, with combined administration of the latter with E. coli 08 and 028. The data obtained emphasized the importance for the development of the infectious process of the primary stage of shigella attachment to the epithelium. It was also revealed that the presence of common pili in the strains or production of colicine by bacteria intensified the antagonistic activity of E. coli, irrespective of their serological type.

[Intraspecies antagonism of Sh. flexneri in an HEp-2 cell line model]. / Izuchenie vnutrividovogo antagonizma Sh. flexneri na modeli kletochnoi linii HEp-2.

The authors describe an effect of suppression of invasion of the guinea pig eye conjunctiva and the HEp-2 epithelial cells by virulent Sh. flexneri bacilli, with a simultaneous administration of the same dose of avirulent shigella mutants, genetically connected with them. The data of morphological study and experiments with 3H-glucose labeled shigellae carried out on the cell species model indicated that the bacterial competition for the specific sites for absorption on the epithelial cells underlay the observed phenomenon.

[Study of the virulence of Shigella sonnei isolated from persons with different forms of dysenteric infection]. / Izuchenie virulentnosti shigell Zonne, vydelennykh ot lits s razlichnymi formami dizenteriinoi infektsii

Possible ranges of virulence of Sh. sonnei strains isolated from the patients and carriers in the foci of Sonne dysentery, supposedly with the same source of infection, were studied. Sh. sonnei strains isolated from carriers proved to be less virulent than the strains isolated from patients with the clinical manifestation of the infection. A hypothesis was put forward explaining some aspects of carrier state in Sonne dysentery, which most probably was explained by the refracterity of the macroorganism, not by the alterations in the genom of the causative agent.