Clostirdium

Clostridium

It is gram positive rod shaped bacteria. It is obligate anaerobes capable of producing endospores in most species. The spore of most species are located terminally or subterminally. Clostrdia are motile with peritrichous flagella. Their natural habitat is the soil or the intestinal tract of animals and human, where they are live as saprophytes .Clostridium contains around 100 species that include common free living bacteria, as well as important pathogens. The four main species responsible for diseases in human are:

C. botulinum causing botulism
C. tetani causing tetanus
C. perfringens causing gas gangrene
C. difficle causing pseudomembranecolitis

Clostridial that produce invasive infetions

Many different toxin- producing clostridia(C. perfringens and related clostridia) can produce invasive infection(including myonecrosis and gas gangrene)if introduced into damaged tissue. A bout 30 species of clostridia may produce such an effect, but the most common in invasive bacteria is C.perfringens (90%). C.perfringens producing enterotoxin is a common cause of food poisoning.


Clostridium tetani, which causes tetanus, worldwide in distribution in the soil and in the feces of horses and other animals. The spores are located at one end of the bacilli (drum-stick). Several types of C tetani can be distinguished by specific flagellar antigens

Pathogenesis

C.tetani is not an invasive organism. The infection remains strictly localized in the area of devitalized tissue (wound, burn, injury, umbilical stump, surgical suture) into which the spores have been introduced. The volume of infected tissue is small, and the disease is almost entirely a toxemia. Germination of the spore and development of vegetative organisms that produce toxin are aided by
(1) necrotic tissue,
(2) calcium salts
(3) associated pyogenic infections, all of which aid establishment of low oxidation-reduction potential. The toxin released from vegetative cells reaches the central nervous system and rapidly becomes fixed to receptors in the spinal cord and brain stem and exerts the actions.
Clostridium botulinum

Clostridium botulinum, which causes botulism, it is worldwide in distribution; it is found in soil and occasionally in animal feces. Types of C botulinum are distinguished by the antigenic type of toxin they produce. Spores of the organism are highly resistant to heat, withstanding 100 °C for several hours

Pathogenesis

It is an intoxication resulting from the ingestion of food in which C. botulinum has grown and produced toxin. The most common offenders food are spiced, smoked, vacuum packed, or canned alkaline foods that are eaten without cooking. In such foods, spores of C botulinum germinate; under anaerobic conditions, vegetative forms grow and produce toxin. The toxin acts by blocking release of acetylcholine at synapses and neuromuscular junctions. Flaccid paralysis results.
Clostridia difficle and diarrheal diseases

Pseudomembranous colitis is diagnosed by detection of one or both C difficile toxins in stool and by endoscopic observation of pseudomembranes or microabscesses in patients who have diarrhea and have been given antibiotics. Plaques and microabscesses may be localized to one area of the bowel. The diarrhea may be watery or bloody, and the patient frequently has associated abdominal cramps, leukocytosis, and fever.
Although many antibiotics have been associated with pseudomembranous colitis, most common are ampicillin.

The disease is treated by orally giving metronidazole or vancomycin. Administration of antibiotics results in proliferation of drug-resistant C difficile that produces two toxins. Toxin A, a potent enterotoxin that also has some cytotoxic activity, binds to the membranes of the gut at receptor sites. Toxin B is a potent cytotoxin. Both toxins are found in the stools of patients with pseudomembranous colitis.