Comparative Characteristics of Discrimination of S. enterica Isolates by Phagotyping Test and Dienes Test.

We propose an original methodological approach to discrimination of newly isolated Salmonella enterica strains with the use of Dienes test. Dienes test is used for identification of P. vulgaris and P. mirabilis strains. It consists in growth suppression by mobile bacterial strain cultures and the formation of a demarcation line (Dienes line) between the strains growing towards each other. Similarities and differences between salmonella phagotyping method and Dienes test-based discrimination of the strains are detected. The studied sample of salmonellas was divided into 12 phagotypes. Cluster analysis has shown that most of the salmonella strains could not be clusterized by both methods. Discrimination by different methods has shown that the largest clusters contain the same strains. Clusterization of salmonella strains by different methods shows moderate congruency. Rand index used for comparison of the results of the sample clusterization by different methods is 0.88. High heterogeneity of salmonella strains is presumably explained by heterogeneity of antagonism factors within the S. enterica species. Intraspecies antagonism is essential for limitation of the horizontal gene transfer in closely related strains and for increase of the genetic heterogeneity of salmonella population in the host.

Antagonistic Activity of Intestinal Lactobacteria from Domestic Fowl against Clinical Isolates of Salmonella enterica.

Strain parameters of Salmonellas and Lactobacteria affecting their antagonistic activity were studied using an original method. Real-time PCR was applied for measuring the decrease in the concentration of field isolates of Salmonellas isolated from chickens in the presence of field isolates of Lactobacteria also isolated from the gastrointestinal tract of chickens and broiler chickens. Dispersion analysis showed that the probability of suppression of Salmonella growth by Lactobacteria is determined by strain parameters of both Lactobacteria and Salmonellas (p<0.001). However, strain parameters of Lactobacteria were found to be more important that Salmonella strain parameters during co-culturing.