Comparative study of hemolytic activity of Bordetella species

Bordetella species colonize the respiratory tract of mammals and thereby cause the whooping cough. Most of the species produce adenylate cyclase - a toxin (hemolysin) responsible for increasing intracellular cyclic AMP (cAMP) levels in mammalian neutrophils and macrophages and as a consequence their phagocytic function get impaired. This study was carried out to isolate species of Bordetella and to study the hemolytic activity of each species on RBCs of sheep, human and poultry at varied culture conditions by altering the temperature, pH and cell age. Three pathogenic Bordetella species were isolated from fifty suspected whooping cough patients on Bordet-Gengou agar and identified by their biochemical profiles. The hemolytic activity of B. pertussis, B. parapertussis and B. bronchiseptica was investigated in terms of cell bound and cell free hemolysin on human, poultry and sheep RBCs at variable pH, temperature and cell age in Stainer Scholt broth. The hemolysin activity was also determined qualitatively on blood agar containing different blood samples. All the species revealed optimum hemolytic activity in pH range 7.5-8.0 (in slight alkaline condition), temperature 37°C and cell age up to 20-24 hrs. The cell bound hemolytic activity was found to be maximum than cell free activity and varied with blood samples of different species. B. pertussis showed maximum hemolytic activity on human red blood cells followed by poultry and sheep RBCs. B. parapertussis and B. bronchiseptica showed maximum hemolytic activity on sheep and poultry RBCs respectively. The findings of our study revealed that different determinants are involved in host interactions and virulence of Bordetella species.