Clostridium Perfringens

It is a normal inhabitant  of the large intestine of human and animals. It cab be easily found in feces. The spores of it are commonly found in soil, dust and air.

Morphology

It is a plump, gram positive bacillus with straight, parallel sides and rounded or truncated ends, about 4 – 6 micrometer x 1 micrometer, usually occurring single or in chains or small bundles.

Cl. Perfringens are capsulated and non motile. It is pleomorphic, and filamentous and involution forms are common.

Cultural Characteristics

It grows anaerobically but can also grow under microaerophilic conditions. Oxygen is not toxic for this bacillus and cultures do not die on exposure to air. It grow better over a pH range of 5.5 – 8.0 and temperature range from 20 – 50 C. a temperature of 45 C is optimal for many strains. The generation time at this temperature may be as short as 10 minutes. This property of Cl. Perfringens can be used to obtain pure culture of it.

Robertson’s cooked meat medium shows good growth of it. After overnight of incubation on rabbit, sheep or human blood agar, colonies of most strains show a ‘target hemolysis’, resulting from a narrow zone of complete hemolysis due to theta toxin and a much wider zone of incomplete hemolysis due to alpha toxin. This type of double zone of hemolysis may fade on longer incubation.

Biochemical Reactions

It ferment sugar glucose, maltose, lactose and sucrose with the production of acid and gas. It is indole negative, MR positive and VP negative. H2S is formed abundantly. Most strains reduce nitrates.

Resistance

Its spores can be destroyed easily by boiling for five minutes. But food poisoning strains of Type A and certain Type C strains can resist boiling for 1 – 3 hours. Autoclaving of 121 C for 15 minutes is lethal. Spores are resistant to the antiseptics and disinfectants in common use.

Toxins

Cl. Perfringens is one of the most prolific of toxin – producing bacteria, forming at least 12 distinct toxins, besides many other enzymes and biologically active soluble substances. The four major toxins alpha, beta, epsilon an iota, are predominantly responsible for pathogenicity. Alpha toxin is produced by all types of Cl. Perfringens and most abundantly by type A strains. This is the most important toxin biologically and is responsible for the profound toxemia of gas gangrene. It is lethal, dermonecrotic and hemolytic.

Pathogenicity

In human Cl. Perfringens produces infection like Gas gangrene, food poisoning, gangrenous appendicitis, necrotising enteritis, biliary tract infection, brain abscess and meningitis, panophthalmitis, thoracic infections, urogenital infections.

Gas Gangrene

Cl. Perfringens type A is the predominant agent causing gas gangrene. It can be produced alone but it more commonly seen in association with other clostridia as well as nonclostridial anaerobes and even aerobes. All clostridia wound infections do not result in gas gangrene.

Food Poisoning

Some strains of Type A can produce food poisoning. They have been shown to produce a heat labile enterotoxin which, like the enterotoxins of V. cholerae and enterotoxigenic E. coli, lead to fluid accumulation in the rabbit ileal loop.

Reference: The Text Book Of Microbiology

Gaurav Singh

Editor in Chief Medical Microbiology & RDT Labs - RDT Labs Magazine

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