doi: 10.15389/agrobiology.2013.4.70eng
UDC 579.62:579.869.1.083.18
APPROACH TO CLASSIFICATION of Listeria monocytogenes ISOLATES ON THEIR VIRULENCE FOR THE EXPERIMENTAL ANIMALS
I.Yu. Egorova
All-Russian Research Institute of Veterinary Virology and Mirobiology, Russian Academy of Agricultural Sciences,
Pokrov, Petushinskii Region, Vladimir Province, 601120 Russia,
e-mail: iegorova@list.ru
Received March 5, 2013
A pathogenicity of Listeria isolates is usually determined in the qualitative kerato-conjunctival test on guinea pigs. That test allows to subdivided the strains into two main groups, i.e. pathogenic and non-pathogenic, but not to carry out an intraspecific typing of the pathogen, which is necessary for establishing the source of infection and the ways of its expansion, and also for the evaluation of epidemiological significance of isolates from the environment and food products. In our study, the pathogenicity of different Listeria monocytogenes cultures was investigated in test with outbred white mice, and the approach to Listeria classification is proposed on the base of the virulence manifested after an intraperitoneal injection of different bacterial culture. It is shown that the seasons, as well as the composition and type of media, used for bacteria cultivation, did not affect significantly the virulence of the isolates for laboratory animals. The LD100 and LD50 were estimated, and LD50 was found to be the most reliable index for intraspecific typing of L. monocytogenes isolates. The LD50 for white outbred mice was estimated in 30 cultures of L. monocytogenes. According to the LD50/min and LD50/max, all isolates were divided into five groups, which can be designated as a highly virulent strains (LD50/min and LD50/max within 104 to 106 colony-forming unit per animal), virulent strains (LD50/min and LD50/max of 106 to 107 CFU per animal), the strains of moderate virulence (LD50/min and LD50/max of 107-108 CFU per animal) and low virulence (LD50/min and LD50/max within 108-109 CFU per animal), and the avirulent ones, which LD50 has not been titrated (LD100 more then 109 CFU per animal).
Keywords: Listeria monocytogenes,white mice, virulence, LD50.
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