Microbiological characteristics and antibiotic sensitivity of <i>Mycobacterium avium</i> subsp. <i>paratuberculosis (MAP)</i> isolated on the territory of Western Siberia

Abstract

The results of the studies of microbiological features of cultures of standardized and clinical strains isolated from biological material of the animals on the territory of Western Siberia belonging to Mycobacterium avium subsp. paratuberculosis (MAP) are presented. Microbiological studies of the pathogens consisted of the bacterioscopic method (staining of smears of cultures according to Ziehl – Neelsen) and the culture method (processing of biomaterial by the method of A.P. Alikaeva with subsequent sowing of the obtained sediment on Lowenstein-Jensen and Finn-2 egg nutrient media with mycobactin). In addition, biochemical tests with the cultures isolated from the material were used, including examination of colony growth at 30, 37 and 42 C, on the medium with sodium salicylate, with 5% sodium chloride, nitrate reduction, determination of amidase, catalase, arylsulfatase activity, hydrolysis of Tween-80 and a biological method consisting of intravenous infection with suspensions of standardized and clinical strains of non-linear white mice. The results of the studies showed that the cultures of clinical strains belonged to the 3rd group of mycobacteria according to the Runyon classification and their properties were identical to the standardized strain of M. paratuberculosis, which allows us to attribute them to mycobacteria of paratuberculosis. Antibiotic sensitivity studies of the standardized strain of M. paratuberculosis (Central-Lubinsky) and clinical strains revealed their susceptibility to all the drugs used in the studies. In a biological assay, mice infected with paratuberculosis pathogens had lower body weight than in the control groups. Autopsy revealed enlargement of lungs, spleen and liver, single purulent foci on liver, spleen and mesentery, and the liver was marbled, the mucosa of the small intestine is not changed. The growth intensity of cultures from the biomaterial (lungs, liver, spleen) was 2(++) to 3(+++) to 4(++++) points, the growth intensity of the cultures from the mucosa of the small intestine is 0(+/-) points. Bacterioscopic examination of smears of colony cultures of the studied pathogens isolated from the internal organs of mice of the experimental groups and stained by Ziehl – Neelsen staining showed the presence of single acid-fast granular bacilli arranged in groups or in the form of a "palisade", which is characteristic of the causative agent of paratuberculosis. The biological method of research on laboratory animals revealed the susceptibility of nonlinear white mice to the tested cultures and the possibility of reproducing experimental paratuberculosis infection on them.