Legend: + = positive > 85%, - = negative > 85%, d = variable, w = weak positive reaction
Phylum Firmicutes, Class Clostridia, Order Clostridiales, Family Clostridiaceae, Genus Clostridium, Cluster I (Clostridium sensu
stricto), Clostridium novyi (Migula 1900) Bergey, Harrison, Breed, Hammer and Huntoon 1923. Three biotypes: A, B and C.
Historical synonyms: Bacillus oedematis maligni Novy 1894, Bacillus novyi Migula 1900, Clostridium oedematiens Bergey, Harrison,
Breed, Hammer and Huntoon 1923.
Type A and C: Gram-positive (becoming Gram-negative) straight rods, 0.6-1.4 x
1.6-17.0 µm, occuring singly or in pairs. Type B: Gram-positive straight to curved rods,
1.1-2.5 x 3.3-22.5 µm.
Motility is variable. Spores are oval, central/subterminal, and may swell the cell;
sporulation of most strains occurs most readily on blood agar plates incubated for 3
Surface colonies on blood agar plates are 1-5 mm in diameter, beta-haemolytic (weak
hemolysis for type C), flat or raised, translucent or opaque, gray, dull or glistening,
circular, with a crystalline or mosaic internal structure, and a scalloped, undulate,
lobate, or rhizoid margin. They may appear as a spreading film over the entire plate.
Cultures in PYG (peptone, yeast extract and glucose) broth are turbid with a smooth or
flocculent sediment and have a pH of 5.1-5.8 after incubation for 7 days. Poor growth
in nutrient broth or cooked meat broth.
Growth is inhibited by 6.5% NaCl, 20% bile, or pH of 8.5. Grows at: 30 ºC, optimum at 37-45 ºC. Growth at 25 ºC is weak and variable.
Growth is stimulated by fermentable carbohydrates, serum or peptic digest of blood. Products in PYG broth: propioinic and butyric
acids, H2 (type A). Fermentable carbohydrates greatly stimulates growth moderate/abundant gas is produced in PYG deep agar
Require strictly anaerobic conditions and will not grow in the presence of even traces of O2.
Isolated from soil, marine sediments, animal and human wounds including gas
gangrene, feces (type A & B). Type C was isolated from water buffalo osteomyelitis.
Susceptible to chloramphenicol, clindamycin, erythromycin, penicillin G.
Types A and B are pathogenic for laboratory animals (mice, guinea pigs, rabbits, rats
The principal lethal toxin of both types A and B is the necrotizing alpha toxin.
Type A strains also produce gamma (phospholipase C) and epsilon (lipase) toxins;
some strains may produce delta (oxygen-labile hemolysin) toxin. The gamma toxin
(lecithinase of type A) is active on horse red-blood cells. The epsilon toxin (lipase)
produces a pearly layer on colonies on egg yolk agar plates and is useful in
differentiating between type A and type B strains. Also, the type A lecithinase (gamma
toxin) is antigenically distinct from the lecithinase (beta toxin) of C. novyi type B.
Type B strains also produce zeta (hemolysin) and eta (tropomyosinase) toxins. Produces “infectious necrotic hepatitis” (“black
disease”) in sheep.
Type C produces only small amounts of lecithinase (gamma toxin) that are not detected on egg-yolk agar.
Nontoxic strains can be converted to toxic strains through the mediation of specific bacteriophages.
Plasmids have been found in both toxic and nontoxic variants of the same strains and may be involved in this transfer of toxigenicity.
C. septicum, C. perfringens, and C. novyi are the three most common causes of clostridial myonecrosis (gas gangrene).
- N.A. Logan and P. De Vos, 2009. Genus I. Clostridium Prazmowski 1880. In: (Eds.) P.D. Vos, G. Garrity, D. Jones, N.R. Krieg, W.
Ludwig, F.A. Rainey, K.-H. Schleifer, W.B. Whitman. Bergey’s Manual of Systematic Bacteriology, Volume 3: The Firmicutes,
- Smith L.D.S. and Hobbs G., 1975. Genus III. Clostridium Prazmowski 1880. In: (Eds.) Buchanan R.E. and Gibbons N.E., Bergey’s
Manual of Determinative Bacteriology, Eighth Edition, The William & Wilkins Company, Baltimore, 551-572.
- Macovei A., 2009. Identificarea bacteriilor anaerobe. In: Tratat de Microbiologie Clinica (Ed. Buiuc D. si Negut M.), editia a IIIa,
Editura Medicala, Bucuresti, 900-927.
- Secasiu V., 2001. Boli produse de germeni din genul Clostridium. In: Boli infectioase ale animalelor, Moga Manzat R., Ed. Brumar,
H2 is produced very abundantly by type A, variable by type B and weak by type C. Milk reaction: curd (type A), variable (type B) or
negative (type C). Meat digestion is variable in types A, and positive in types B & C.
Positive results for H2 production, substrate utilized and/or acid produced from glucose (weak reaction for type C).
Negative results for esculin hydrolysis, H2S production, starch hydrolysis, Voges-Proskauer reaction, urease, substrate utilized and/or
acid produced from: amygdalin, arabinose, cellobiose, dulcitol, glycogen, inulin, lactose, mannitol, melezitose, melibiose, raffinose,
rhamnose, sorbitol, sorbose, starch, sucrose, trehalose & xylose.
(c) Costin Stoica
Differential characters of the Clostridium novyi biotypes: