Phylum Firmicutes, Class Clostridia, Order Clostridiales, Family Clostridiaceae, Genus Clostridium, Cluster XIVa (Clostridium
non-sensu stricto), Clostridium nexile Holdeman and Moore 1974.
Gram-positive, ovals or straight rods, 0.8-1.7 x 0.8-6.3 µm, occuring in pairs or chains.
Nonmotile. Spores are round / oval, subterminal, but are rarely seen, even in cultures
that resist heating at 80 ºC for 10 min. Spores have been seen in 6-days-old cultures
of PYG broth.
Surface colonies on blood agar plates are 0.5-1 mm in diameter, circular, convex to
raised, semiopaque or with opaque centers and translucent edges, smooth, shiny,
white to yellowish, nonhemolytic, and with entire margins.
Cultures in PYG broth have a smooth or ropy sediment, often with no turbidity, and a
pH of 4.9-5.3 after incubation for 5 days.
Obligately anaerobic. Growth is stimulated by fermentable carbohydrates.
Optimum temperature for growth is 30-37 ºC. Grow at 25 ºC (weak) and at 45 ºC.
Growth is inhibited by 6.5% NaCl and 20% bile. Abundant gas is detected in PYG
deep agar cultures. Products in PYG broth are formic and acetic acids and ethanol;
abundant H2 is detected.
Isolated from human feces as part of normal flora. Susceptible to chloramphenicol and clindamycin.
Considered normal flora in human feces.
- 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,
- Holdeman L.V. and Moore W.E.C., 1974. New genus, Coprococcus, twelve new species, and emended descriptions of four
previously described species of bacteria from human feces. IJSB vol. 24, No.2, 260-277.
Milk reaction is variable. Meat is not digested.
Positive results for esculin hydrolysis, neutral red reduction, resazurin reduction, substrate utilization and/or acid production from:
fructose, galactose, lactose, sucrose & xylose (weak reactions).
Negative results for ammonia, catalase, gelatin hydrolysis, indole production, lecithinase, lipase, nitrate reduction, orotic acid
hydrolysis, starch hydrolysis, urease, Voges-Proskauer, substrate utilization and/or acid production from: adonitol, arabinose,
cellobiose, dulcitol, erythritol, glycogen, glycerol, inositol, maltose, mannitol, melezitose, rhamnose, ribose, sorbitol & sorbose.
Variable or weak results for H2S production, substrate utilization and/or acid production from: amygdalin, esculin, inulin, mannose,
melibiose, raffinose, salicin, starch & trehalose.
(c) Costin Stoica