Clostridium botulinum: Properties of the Bacteria

Clostridium botulinum

C. botulinum is a heterogeneous group of spore-forming,anaerobic, Gram-positive bacteria causing botulism, a paralytic disease with the presentation of food poisoning.

Properties of the Bacteria

◗ Morphology

C. botulinum shows following features:

·           C. botulinum is Gram-positive in young cultures less than18 hours’ old. The organism may be Gram-negative in cultures after 18 hours of incubation.

·           The bacillus measures 51 m.

·           The bacillus is motile by the presence of peritrichous flagella,

·           and possesses subterminal and oval bulging spores.

·           The bacteria are noncapsulated.

◗ Culture

C. botulinum is a strict anaerobe. The bacteria grow at anoptimum temperature of 35°C. The bacteria can grow on a wide range of media including blood agar, Mueller–Hinton agar, and RCM media. On blood agar, C. botulinum produces large, irregular, and semitransparent colonies with irregular fimbriate border. They produce spores when grown in alkaline glucose gelatin media at 20–25°C.

◗ Biochemical reactions

C. botulinum shows following reactions:

·            C. botulinum is identified by its ability to ferment glucose, hydro-lyze gelatin, digest protein, and produce the enzyme lipase.

·           Production of enzyme lipase is demonstrated by formation of iridescent film on C. botulinum colonies grown on egg yolk agar.

◗ Other properties

Susceptibility to physical and chemical agents: C. botulinumorganisms as well as spores are highly resistant. They are resistant to boiling at 100°C for several hours, but are killed by pressure cooking at 120°C for 10 minutes. C. botulinum types B, E, and F spores are relatively less heat resistant. The toxins are destroyed by boiling for 10 minutes or cooking at 80°C for 30 minutes.

Typing: C. botulinumis a heterogeneous group of spore-forming, anaerobic, Gram-positive microorganisms. They are classified into seven types (A to G) on the basis of the antigenic specificities of their toxins.