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The safety of food production as concerns Listeria is the key to the sanitary wellbeing of manufactured products. Molecular-genetic methods for the analysis of Listeria, including whole-genome sequencing, are effective in monitoring persistent contaminants and in the epidemic investigation of cases of foodborne infections. They have been adopted in the European Union, United States, and Canada. In Russia, multilocus and whole-genome sequencing has proven itself in the analysis of clinical food isolates and Listeria from the environment. The objective of the study was molecular-genetic characterization of Listeria detected in the industrial environment of meat processing. To characterize the Listeria isolates, microbiological methods were used according to GOST (State Standard) 32031-2012, as well as multilocus sequencing, including the analysis of seven housekeeping genes and four virulence genes, as well as whole-genome sequencing. In swabs that were positive for the presence of Listeria spp. taken at two meat-processing plants in Moscow, Listeria monocytogenes constituted 81% and L. welshimeri 19%. The predominant genotype (Sequence Type, ST) of L. monocytogenes was ST8. The variety was supplemented with ST321, ST121, and ST2330 (CC9 (Clonal Complex 9)). L. welshimeri, which prevailed in the second production, was represented by ST1050 and ST2331. The genomic characteristics of L. welshimeri isolates confirmed that they have high adaptive capabilities both as concerns production conditions (including resistance to disinfectants) and the metabolic peculiarities of the gastrointestinal tract of animals. L. monocytogenes CC9 and CC121 are also correlated with food production in other countries. However, L. monocytogenes CC8 and CC321 can cause invasive listeriosis. The concordance in the internalin profile of the ST8 isolates from the industrial environment with the clinical isolates ST8 and ST2096 (CC8) is a cause for concern. The study showed the effectiveness of molecular-genetic methods in determining the diversity of Listeria detected in the production environment of meat processing, and laid the foundation for monitoring of persistent contaminants.

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The article discusses main directions and stages of the 45 years of Legionnaires disease study. Analysis of epidemiology and laboratory diagnostics of infection show as unknown until 1976 microorganism occupied a notable niche in the etiology of severe pneumonia. Control and monitoring of potential dangerous water systems, generating water aerosol containing Legionella in high concentration, plays a major role in the prevention of Legionnaires disease.

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AIM: Study the effect of water temperature from 40 to 70 degrees C on viability of plankton forms and model Legionella pneumophila under experimental conditions. MATERIALS AND METHODS: Monospecies legionella biofilms, obtained in plates for enzyme immunoassay during 96 hours at 28 degrees C, and water suspension of BCYE agar cultivated cells of L. pneumophila at a concentration of 10(3) - 10(5) CFU per liter were used in the study for evaluation of bactericidal effect of temperature on various legionella forms. RESULTS: Analysis of effects of various temperature regimens on plankton forms and model legionella biofilms has shown that at a temperature range from 50 to 60 degrees C a significant reduction of quantity of viable legionella cells occurs. Model legionella biofilms have partially conserved viability at a temperature of 60 degrees C and only exposition to a temperature of 70 degrees C resulted in death of legionella biofilms and plankton forms of bacteria. A dependence of viability conservation of legionella from the initial concentration of the causative agent in water and duration of exposition at varying temperature was shown. CONCLUSION: Short-term heating at a temperature of at least 70 degrees C has the most pronounced bactericidal effect on plankton forms and model L. pneumophila biofilms under experimental conditions. Such temperature regimen could be used as one of the prophylaxis approaches during maintenance of especially dangerous water system and, fist of all, systems of hot water supply.

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A panel of mAb (IgG1, IgG3, IgM) against Legionella pneumophila cytolysin (CL)-protease of 37 kDa was obtained. Subtyping of L. pneumophila strains of serogroup 1 by using mAb against CL (mAb-CL) was carried out. The results of comparative analysis of the specificity of mAb-CL and the panel of mAb kindly provided by Dr. J. M. Barbaree (Centers for Disease Control, Atlanta, GA) allowed us to recommend mAb-CL to be used as a diagnostic tool to reveal the pathogenicity of L. pneumophila strains of serogroup 1. Hybridomas were also raised in a syngenic system which produced anti-idiotypic mAb (mAb2) against anti-CL mAb B6/1. The Ab2 belonged to Ab2 gamma type: 1) Ab2 reacted with B6/1 Id only, 2) Ab2 inhibited the interaction of B6/1 Ab1 with CL, and 3) CL inhibited the reaction of Ab2 with Ab1. The use of Ab2 allowed us to show that B6/1 Id is expressed in 4 to 32% of serum antibodies during the primary and secondary immune responses of BALB/c mice to CL. Ab2 induced the production of anti-anti-idiotypic antibodies (Ab3) in BALB/c mice, and some of them reacted with CL. Thus, we have demonstrated the possibility of inducing an antibody response to CL (one of the main L. pneumophila pathogenic factors) in intact syngenic mice with anti-idiotypic antibodies.

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Phenylalanineaminopeptidase was isolated and purified from the culture filtrate of Legionella pneumophila by affinity chromatography on O-tert-butyl-L-threonyl-L-phenylalanyl-L-prolylglycyl-aminosilo chrom and by gel-filtration; a 401-fold purification with a yield of 18% was achieved. The enzyme was a metalloenzyme with a molecular weight of 35000 and a pI of 5.8. It was stable at pH 7-9 and had an activity optimum in the range of pH 8-9.5 with L-phenylalanine p-nitroanilide as substrate. Enzyme activity was highest towards the latter compound, substantially lower towards L-leucine p-nitroanilide and only marginal towards other p-nitroanilides. Besides phenylalanineaminopeptidase, a metalloproteinase and a serine proteinase were also detected in L. pneumophila culture filtrate.

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