Systematic Veterinary Bacteriology and Mycology

MORPHOLOGY, CULTURAL AND BIOCHEMICAL CHARACTERS

• Large, pleomorphic, Gram+ve rods with oval to cylindrical subterminal spores are characteristic.
• There is little or no swelling of the mother cell, non-capsulated, motile by peritrichous flagella.
• Clostridium novyi type B and C.haemolyticum are very demanding in both their anaerobic and nutritional requirements.
• Very strict anaerobic procedures are necessary and media containing cysteine should be used. These clostridia can die within 15mts of being exposed to atmospheric O_{2 .}
• These organisms are difficult to grow on primary culture and the growth is enhanced by agar enriched with glucose or freshly prepared blood or fresh brain infusions.
• On blood agar C.novyi produces characteristic large, irregular colonies with a rhizoid edge and a large zone of clear haemolysis.
• On moist surface of solid media after 3-4 days of incubation colonial motility develops which is characterized by the movement of daughter colonies moving away from parent colonies in spirals or arc and few return and fuse to the parent colony.
• In horse blood agar, the colonies are haemolytic, small and usually rhizoidal in nature.
• Areas of hemolysis develop beneath the colonies and develop into wider zone after 48-72hrs incubation.
• In Sheep blood agar very slight haemolysis develop. In Robertson’s cooked meat medium C.novyi type D is very strongly proteolytic.
• Type A, B and C are saccharolytic. The lecithinase activity of beta toxin of type B and D, and Gamma toxin of type A produces quite distinct opacity changes on egg-yolk agar.
• C.novyi type A exhibits lipase activity on egg-yolk agar.
• It will produce characteristic iridescent pearly layer on the surface of the colonies, extending on to the surface of the medium immediately surrounding them.
• C.novyi type A is the only species among clostridia that produces both a lecithinase and a lipase.
• Saccharolytic type ferment glucose and maltose but not lactose.