Clostridium are Gram-positive spore forming bacilli, anaerobes.
I – CLASSIFICATION:
Among the bacilli and gram-positive cocci forming endospores, there are different kinds:
Aerobic Bacillus Sporosarcina
Strict anaerobes Clostridium
The observation of the spore is not always obvious, and put it in evidence using the properties conferred by this structure:
– Resistance to heating at 70 ° C for 10 min,
– Resistance to ethanol (95%) at 45 ° C or use environments supportive of sporogenesis.
This direct or indirect research spore has an interest to differentiate Clostridium other Gram-positive bacilli non-spore forming anaerobes:
– Bifidobacterium, which are classified in Bergey’s Manual among the “non-regular or irregular spore forming bacilli.”
Within Clostridium, a schematic classification based on the hydrolysis of protein and carbohydrate fermentation is convenient to classify Clostridium into four groups.
The validity of this classification is confirmed by the results obtained by DNA-DNA and DNA-rRNA.
The study of GC% Clostridium shows two groups.
– The first 24-29% GC, includes bifermentans C., C. botulinum, C. cadaveris, C. difficile, C. fallax, C. limosum, C. novyi, C. perfringens, C. septicum, C. sordellii , C. sporogenes and C. sucking,
– The second, GC 41-49%, includes innocuum C., C. and C. symbiosum sphenoid.
II – HABITAT:
Most Clostridium species are soil bacteria, but are also isolated in the gut and feces of man and various animals.Thus the presence of Clostridium in water or food, for example, sign in general faecal contamination.
III – CHARACTER BACTERIOLOGICAL:
A – Morphological characteristics: (figure 1)
Are Gram-positive bacilli, whose wall usually contains meso-diaminopimelic acid.
They are mobile or immobile cilia peritrichous.
They produce oval or spherical endospores, which can distort the bacteria.
B – Metabolic Characteristics:
– These are strictly anaerobic bacteria, including vis-à-vis the oxygen tolerance varies among species, some species may (but sporulate) grow in the presence of oxygen.
– Clostridium are usually devoid of catalase.
– Clostridium usually produce organic acids and alcohols from carbohydrates and peptones. Knowledge of species behavior on the plane:
– Proteolysis of indole production, possession of a urease
– Sweet fermentation: glucose, esculin, lactose, sucrose, mannitol …
– The production of caproic, butyric, isovaleric, propionic …,
– Lipids and phospholipids, allows for the diagnosis of the species (Table I).
IV – PATHOGENICITY:
Pathogenicity is linked to toxins and / or enzymatic activities.
Schematically the main aspects are grouped below.
CLINICAL CASE INVOLVED
C. botulinum Botulism
C. perfringens food poisoning
Necrotic enteritis C. perfringens
Pseudomembranous colitis C.difficile
C. perfringens gas gangrene, C.septicum, C.novyi, C.sordellii.
In hospitals Clostridium represent slightly more than 10% of all isolates of anaerobic bacteria (Table II).