Clostridium perfringens

Clostridium perfringens

Clostridium perfringens (Latin perfringere, break through ') is a rod-shaped, Gram-positive, endosporenbildendes, unbegeißeltes bacterium of the genus Clostridium. In ( older ) literature there is also sometimes called " Welch Fraenkelscher Gasbazillus " or Clostridium welchii.

Occurrence

C. perfringens is a strict anaerobe but survived the brief exposure problems in oxygen-rich atmosphere. The organism can in the soil ( anaerobic zones) can be detected in water, dust and foods, but also in the intestines of humans and animals ( 1,000 to 10,000 cells / g faeces). In the soil are the major clostridial anaerobic cellulose - degrading microorganisms.

The temperature optimum of C. perfringens is about 43 to 47 ° C ( with generation times of 8 to 12 minutes ), Extreme range min. at 10 to 18 ° C and max. at 50 to 52 ° C. The spores can survive temperatures of 60 ° C, depending on various environmental factors. The heat resistance is highly variable depending on the strain and can at 100 ° C for up to 60 min be. The toxin is heat labile (4 minutes at 60 ° C). As Decimal reduction time are given 15-145 min at 90 ° C and from 0.31 to 38 min at 100 ° C.

Toxins

C. perfringens serotypes A, B, C, D and E forms of pathogenic exotoxins ( enterotoxins ) for humans. Α by the detection of significant toxins, β, ε, ι, these serotypes of C. perfringens are distinguished. Gasbrandbazillen form at least twelve toxins that act as enzymes (proteases, collagenases, deoxyribonucleases and phospholipases ). These enzymes break down tissue and cause necrosis in the affected muscle tissue.

Pathogenesis and pathology

The pathogen counts with other clostridia to the group of Gasbrandbazillen and is the most common causative agent of gas Brands (70 to 80%). In addition, the bacterium is more common cause of necrotizing pneumonia, gangrenous cholecystitis, sepsis or other non-specific infections. In human medicine, in particular, type A and type C is important. In addition, Clostridium perfringens can cause infections of the central nervous system, of which the most common is the clostridial meningitis, which usually develops from a clostridial sepsis, but also due to local trauma or surgery, as can the removal of a subdural hematoma arise. More rarely, cases of clostridial encephalitis have been described. In animals, the disease caused by Clostridium perfringens toxins are called enterotoxemia.

Gas gangrene

The gas gangrene caused by Clostridium perfringens is considered severe form of wound infection and is also referred to as " clostridial myositis ", " clostridial myonecrosis " or gas gangrene. The infection usually develops after injury in gardening or activities in the agricultural sector, but also by bite wounds or amputations and has an incubation period of about 2 days. The infected area is characterized by swelling and brownish- livid discoloration. On palpation may optionally be determined a " crackle " ( Crepitatio ). From the infected wound frequently emptied stinking, serous wound discharge. In the absence of prompt treatment, this can lead to death of the infected by a toxin- induced shock within hours. Despite optimal therapy, the mortality rate is high and ranges from 40 to 60%. However, the disease has become rare because of good surgical care in the Federal Republic of Germany; in 1998 there were in Germany 114 reported cases of gas gangrene.

As pathomechanical cause of the gas fire can be Clostridium perfringens bacteria serotype A prove. These destroy by their α - toxin - a lecithinase, the membrane-bound lecithin into phosphorylcholine and diacylglycerol splits - the cell membranes from the infected area. The proliferation of toxin-producing pathogens or the germination of spores of C. perfringens is determined by a reduction of the redox potential in tissues - stimulated - for example, with reduced blood circulation, secretion accumulation or necrosis. Accordingly favor contusions, abrasions soiled, large wound cavities after amputation or Pfählungswunden an infection.

Intestinal infections

C. perfringens is also one of the Lebensmittelvergiftern. The infectious dose is usually even higher, with 700,000 organisms / g, in foodstuffs. Endangered foods are hot -held meat ( beef, poultry), oysters and other seafood. The intestinal toxin infections are caused in the majority of cases of C. perfringens type A strains. In the United States of America Clostridium perfringens with an estimated 248,000 annual cases, the most common reported cause of food poisoning. The germinating after eating clostridia in the gut begin with the production of the perfringens enterotoxin, which increases the permeability of the intestinal epithelium and leads to diarrhea and intestinal cramps, but is rarely accompanied by fever or vomiting. The first symptoms occur within 7-15 hours after eating the contaminated food and often disappear after 24 hours. The mortality rate is low.

Much more serious is in humans induced by C. perfringens enteritis necrotizing ( " intestinal fire " ), which is a highly necrotizing infection of the jejunum. This is caused by β - toxin-producing strains of the bacterium of serotype C and often fatal. The exact pathogenetic mechanisms are not yet fully understood. In the animal kingdom, the type C causes necrotic enteritis necrotic enteritis of piglets or lambs, sheep and calves ..

Diagnosis

The food poisoning by Clostridium perfringens type A is diagnosed by isolation of the pathogen from the gut or most reliably determined by an enzyme -linked immunosorbent assay (ELISA ) for the detection of bacteria in the intestine. A laboratory diagnosis, however, can usually allow only a subsequent confirmation of the infection, because the symptoms of the disease are already decayed mostly after 24 hours.

The diagnosis of gas gangrene is first made ​​clinically. The bacterial culture can not wait due to the rapid progression of the gas fire in the rule and can therefore only serve to subsequent confirmation.

Microbiological evidence

Detection of Clostridium perfringens is first performed by microscopic preparation of a Gram -stained preparation, are visible in the approximately 4 to 6 × 1 micron large rods with rounded ends. The pathogens can be partially surrounded by capsules in original preparations, which can be identified on the unstained zones around the bacteria. Spores are occasionally found in fecal and soil samples, but usually not in the cultured cultures. As a feature is used, inter alia, immobility due to the lack flagella and the lack of formation of spores in vitro.

Furthermore, cultured the suspected material on anaerobes or standard blood agar and egg yolk agar. Clostridium perfringens colonies are visible under incubation usually after 10 to 12 hours. Characteristic are round, convex, moist, shiny, occasionally shimmering red colonies 3-5 mm in diameter, the presence of oxygen only gray, then light brown and later greenish discolor and are not enclosed by a larger Hämolysefeld the anaerobic blood agar. On standard blood agar takes place Doppelzonenhämolyse around the colonies. On egg yolk agar, the released from the pathogen Lecithinase causes a characteristic whitish brightening around the lawn of growth ( " Seiffert Nailer reaction" ). Add broths quickly cause turbidity with vigorous evolution of gas.

In special laboratories serotypes of Clostridium perfringens also can be determined by means of identification of exotoxins in animal experiments using specific antisera.