Selection of the Nutrient Base and Experimental Quality Assessment of a Bacteriological Growth Medium for the Cultivation of Listeria

Abstract

The causative agent of listeriosis refers to pathogens when clinical diagnosis is difficult due to the polymorphism of the manifestation of the disease. In this regard, the use of express methods of laboratory diagnostics, which include the agglutination reaction, is an urgent need for rapid diagnosis and timely treatment. To obtain an experimental diagnostic listeriosis agglutinating highly specific serum, a sufficient volume of immunogen is required, the source of which is the inactivated bacterial mass of Listeria monocytogenes 766. The development of a bacterial nutrient medium for the cultivation of listeriosis microbe is caused by need to ensure high growth of listeria biomass in a short time. Pacific herring (Clupea pallasii), pollock (Gadus chalcogrammus), roach (Rutilus rutilus) and European squid (Loligo vulgaris) were used as raw materials for obtaining hydrolysates. Comparative physico-chemical studies of tested nutrient bases have shown that optimal basis of nutrient medium is pancreatic hydrolysate of roach, in which the maximum indicators of enzymatic process speed, the content of amine nitrogen, stable preservation of acidic properties for a long time are determined. Using the method of NMR spectroscopy, the amino acid composition of the nutrient medium for accumulation of listeria biomass was established, which is represented by alanine, valine, threonine, arginine, lysine, leucine, methionine, histidine, tyrosine and tryptophan and the amino acids phenylalanine and glycine, which are most important for the growth of listeria. It was found that nutrient medium based on pancreatic hydrolysate of roach had advantages over other bases (Pacific herring, pollock and European squid pancreatic hydrolysates) in terms of germination, sensitivity and efficiency, growth rate of the nutrient medium for listeria cultivation, while maintaining the typical listeria cultural-morphological, biochemical and serological properties. It has been established that effectiveness of experimental nutrient medium f, designed by specialists of laboratory of nutrient media of Irkutsk Anti-Plague Institute, is not inferior to such commercial medical products as GRM-agar and meatpeptone agar. Experimental results confirmed the ability of culture medium for the cultivation of listeria to preserve the biological properties of test strain L. monocytogenes 766 (collection of pathogenic bacteria of the Irkutsk Anti-Plague Institute) for one year. Based on the data obtained, we concluded that the high growth rates of listeria on proposed nutrient medium were achieved through use of pancreatic roach hydrolysate and components optimal concentrations that stimulate the growth of listeria, providing a significant accumulation of bacterial mass in shortest possible time.