Study of the effectiveness of using a selective cephalexin component in a CCA nutrient medium for the detection of clinical isolates of Bordetella bronchiseptica

Bordetellosis is a highly contagious infectious disease of farm and small domestic animals caused by bacteria of the species Bordetella bronchiseptica (B. bronchiseptica). According to the scientific literature and the results of our previous studies, the bacteriological method of laboratory diagnosis of bordetellosis remains the main diagnostic tool. Our preliminary studies show that the efficiency of bacteriological studies and isolation of clinical isolates of B. bronchiseptica from nasopharyngeal secretions is increased when using charcoal- casein agar (CCA) with 5% blood and cephalexin. Our work aimed to determine how different concentrations of cephalexin as a selective component would affect the growth activity of the CCA medium for the primary isolation of clinical B. bronchiseptica isolates and their growth intensity. It has been established that it is optimal to freeze the selective additive cephalexin in the medium of the CCA for the detection of clinical isolates of B. bronchiseptica at a concentration of 4 mg/ml. The yield of microbial cells to B. bronchiseptica strain No 16K from 1 ml of CCA core with the addition of cephalexin at a concentration of 4 mg/100 ml is 5.99 ± 0.34 billion. And when cephalexin is administered at a concentration of 6 mg/100 ml, the yield of microbial cells to the B. bronchiseptica strain No. 16K per 1 ml of the core is 5.38 ± 0.44 billion (p ≤ 0.05). There is a 10.35 % lower yield of microbial cells in the B. bronchiseptica strain No 16K from the CCA middle when cephalexin is added at a concentration of 4 mg/100 m. The concentration of cephalexin in the body center of CCA is 6 mg/100 ml or more and is inhibitory to the growth of B. bronchiseptica, therefore such a concentration in the body in the form of a selective additive cannot be used. The study results show that the use of a selective cephalexin supplement at a concentration of 4 mg/ml can reduce the time for isolation of clinical isolates of B. bronchiseptica by 2-4 days due to inhibition of the growth of extraneous nasopharyngeal microflora and significantly simplify the isolation of pure culture from sick animals