Study of tolerance of enterobacteria to chlorine-based biocides in experimental models using chromogenic indicator tests
N.R. Efimochkina, I.B. Bykova, Yu.V. Korotkevich, Yu.M. Markova, L.P. Minaeva, S.A. Sheveleva
FSBI "Institute of Nutrition", Russian Federation, Moscow, 2/14 Ustinsky Passage, 109240
The species-specific composition of microbial contaminants of vegetable raw materials and equipment used in the production of biotechnological products and beverages fermentation are studied. 85 enterobacteria strains was isolated and investigated, 46 strains of the genera Enterobacter, Pantoea, Citrobacter, Serratia, Escherichia, Cronobacter was identified to the species level; the most frequently detected bacteria of the genera Enterobacter and Pantoea (about 50 %). For the first time developed and tested chromogenic in vitro model based that allows to quantify the degree of inhibition of gram-negative microflora under the influence of antimicrobial agents depending on the concentrations of biocides and density of bacterial populations. A comparative analysis of the tolerance of Enterobacteriaceae strains from different biotopes was conducted. Sensitivity to the treatment of chlorine-containing biocides in 26 strains of enterobacteria from plant material and 9 strains of Escherichia coli from the intestine of male rats of Wistar line was tested. Enterobacteria from vegetable raw materials and swabs were more resistant to antimicrobial action of chlorine, than the representatives of the populations of the normal intestinal microbiota. It is established that the active chlorine concentration of 50–100 mg/dm 3 , the most commonly used in the processing of vegetable raw materials, is not effective for Enterobacteriaceae, if the density of the microbial population is 10 5–7 cells/cm 3 and above. At an initial level of contamination with Enterobacteriaceae not more than 10 3 cells/cm 3 processing solutions with a concentration of active chlorine of 75 to 100 mg/dm 3 can provide effective disinfection of raw materials, equipment, or inventory. Experimental chromogenic in vitro model proposed to assess the impact of chlorine-based biocides on the degree of the enterobacteria inhibition, can be used to justify the selection and doses of antimicrobial agents, effective against other groups of microbial contaminants. This will optimize the use of modes of decontamination of raw materials and sanitizing equipment in the food industry.
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