Physiochemical factors affecting in vitro growth of Pasteurella multocida

Pasteurella multocida causes fowl cholera (FC), a contagious bacterial disease of domestic and wild avian species. It is a Gram negative coccobacilli causing acute highly fatal septicemia with high morbidity and mortality rate. Control of fowl cholera is primarily performed by good management practice and vaccination in areas where disease is endemic. For a quality vaccine, high density growth of P. multocida along with its capsule and outer membrane protein (OMP) is necessary. In the present study, physiochemical factors (growth medium, temperature, pH, incubation time and stirring along with aeration affecting growth density) were evaluated. Growth density was determined by colony forming unit (CFU) and dry mass. Physiochemical factors used in maximum growth density (1.32×1012CFU or 9 mg/ml) of bacteria were between 35 to 40°C, 7.2 to 8.2 pH and 1000 rpm stirring, along with aeration during incubation of 24 h in Brain Heart infusion (BHI) broth. P. multocida showed maximum growth (1.32×1012 or 9 mg/ml) in BHI broth with continuous stirring and aeration (1000 rpm) at 38°C for 24 h. Thus, there was a positive co-relation between colony forming unit (CFU) and dry mass of bacteria.   Key words: Brain heart infusion (BHI), aeration, agitation, fermentor, dry mass.