Optimization of growth conditions for Dichelobacter nodosus in a modified reducing broth without gas phase

Abstract

Virulent footrot represents as a significant contagious ailment affecting hooves of sheep, with Dichelobacter nodosus being the primary agent responsible for transmitting the disease. Vaccinations and various management practices are utilized to control the disease. D. nodosus is a highly fastidious anaerobic bacterium and it is very difficult to grow under laboratory conditions. For the mass production of bacteria as needed for vaccine manufacturing, it must be cultivated in a broth culture. In this study, the broth culture of D. nodosus was optimized and simplified under reducing conditions with three different strains belonging to serogroup B and E. The bacteria were grown in TAS broth supplemented with sodium carbonate (2 mg/ml) and differing levels of sodium thioglycolate (3 to 10 mM), with no gas supplementation, at 37 °C in an incubator. The most favorable growth conditions for the D. nodosus strain JKS-07B (serogroup B) were observed in a broth containing 6mM sodium thioglycolate with a pH of 4.8, before autoclaving and the subsequent addition of sodium carbonate. The bacterial cell density in the broths ranged from 1.9 108 to 2.5 108 CFU/ml, which seemed to be optimum for vaccine formulation.