Clostridium perfringens

Clostridium perfringens
Photomicrograph of gram-positive Clostridium perfringens bacilli.
Scientific classification
Kingdom:	Bacteria
Phylum:	Firmicutes
Class:	Clostridia
Order:	Clostridiales
Family:	Clostridiaceae
Genus:	Clostridium
Species:	C. perfringens
Binomial name
Clostridium perfringens Veillon & Zuber 1898 Hauduroy et al. 1937

Clostridium perfringens (formerly known as C. welchii) is a Gram-positive, rod-shaped, anaerobic, spore-forming bacterium of the genus Clostridium.^[1] C. perfringens is ever present in nature and can be found as a normal component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates, insects, and soil.

C. perfringens is the third most common cause of food poisoning in the United Kingdom and the United States^[2] though it can sometimes be ingested and cause no harm.^[3]

Infections due to C. perfringens show evidence of tissue necrosis, bacteremia, emphysematous cholecystitis, and gas gangrene, which is also known as clostridial myonecrosis. The toxin involved in gas gangrene is known as α-toxin, which inserts into the plasma membrane of cells, producing gaps in the membrane that disrupt normal cellular function.^[2] C. perfringens can participate in polymicrobial anaerobic infections.^[4] Clostridium perfringens is commonly encountered in infections as a component of the normal flora.^[5] In this case, its role in disease is minor.

The action of C. perfringens on dead bodies is known to mortuary workers as tissue gas and can be halted only by embalming.

Food poisoning

In the United Kingdom and United States, C. perfringens bacteria are the third-most-common cause of food-borne illness, with poorly prepared meat and poultry the main culprits in harboring the bacterium.^[2] The clostridium perfringens enterotoxin (CPE) mediating the disease is heat-labile (inactivated at 74 °C) and can be detected in contaminated food, if not heated properly, and feces.^[6] Incubation time is between six and 24 (commonly 10-12) hours after ingestion of contaminated food. Often, meat is well prepared, but too far in advance of consumption. Since C. perfringens forms spores that can withstand cooking temperatures, if let stand for long enough, germination ensues and infective bacterial colonies develop. Symptoms typically include abdominal cramping and diarrhea; vomiting and fever are unusual. The whole course usually resolves within 24 hours. Very rare, fatal cases of clostridial necrotizing enteritis (also known as pigbel) have been known to involve "Type C" strains of the organism, which produce a potently ulcerative β-toxin. This strain is most frequently encountered in Papua New Guinea.

Many cases of C. perfringens food poisoning likely remain subclinical, as antibodies to the toxin are common among the population. This has led to the conclusion that most of the population has experienced food poisoning due to C. perfringens.^[2]

Despite its potential dangers, C. perfringens is used as the leavening agent in salt rising bread. The baking process is thought to reduce the bacterial contamination, precluding negative effects.^[7]

Infection

Clostridium perfringens is the most common bacterial agent for gas gangrene, which is necrosis, putrefaction of tissues, and gas production. It is caused primarily by Clostridium perfringens alpha toxin. The gases form bubbles in muscle (crepitus) and the characteristic smell in decomposing tissue. After rapid and destructive local spread (which can take hours), systemic spread of bacteria and bacterial toxins may result in death. This is a problem in major trauma and in military contexts. C. perfringens grows readily on blood agar plate in anaerobic conditions and often produces a zone of hemolysis.

Treatment

If detected on clinical grounds, treatment should begin without waiting for lab results. Traumatic wounds should be cleaned. Wounds that cannot be cleaned should not be stitched shut. Penicillin prophylaxis kills clostridia, and is thus useful for dirty wounds and lower leg amputations. A high infectious dose is required; the carrier state persists for several days.

Colony characteristics

C. perfringens colonies on an egg yolk agar plate showing a white precipitate

On blood agar plates, C. perfringens grown anaerobically produces β-haemolytic, flat, spreading, rough, translucent colonies with irregular margins. A distinguishing charachteristic of C. perfringens is a zone of double beta haemolysis. Nagler agar plates, containing 5-10% egg yolk, are used to identify strains that produce α-toxin, a diffusible lecithinase that interacts with the lipids in egg yolk to produce a characteristic precipitate around the colonies. One-half of the plate is inoculated with antitoxin to act as a control in the identification.

Salt Rising Bread

Clostridium perfringens is the main rising agent in salt rising bread.

References

1. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9. ^{[page needed]}
2. ^ ^{a b c d} Warrell et al. (2003). Oxford Textbook of Medicine (4th ed.). Oxford University Press. ISBN 0-19-262922-0. ^{[page needed]}
3. ^ Juckett, G; Bardwell, G; McClane, B; Brown, S (2008). "Microbiology of salt rising bread". The West Virginia medical journal 104 (4): 26–7. PMID 18646681. 
4. ^ Brook, I (2007). "The role of anaerobic bacteria in cutaneous and soft tissue abscesses and infected cysts". Anaerobe 13 (5–6): 171–7. doi:10.1016/j.anaerobe.2007.08.004. PMID 17923425. 
5. ^ Wells CL, Wilkins TD (1996). Clostridia: Sporeforming Anaerobic Bacilli. In: Barron's Medical Microbiology (Barron S et al., eds.) (4th ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1. (via NCBI Bookshelf). ^{[page needed]}
6. ^ Murray et al. (2009). Medical Microbiology (6th ed.). Mosby Elsevier. ISBN 978-0-323-05470-6. ^{[page needed]}
7. ^ Juckett, G; Bardwell, G; McClane, B; Brown, S (2008). "Microbiology of salt rising bread". The West Virginia medical journal 104 (4): 26–7. PMID 18646681. 

External links

• Clostridium perfringens genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
• Pathema-Clostridium Resource