The clostridia are Gram positive bacilli which are spore bearing and anaerobic.
Spores are helpful for this organisms to survive in adverse conditions. Vegetative cells of clostridia are killed by lower temperatures like 72°C – 75°C, in short time.
However, spores cannot be destroyed by this temperature.
They need 121°C or temperatures above that. Most species are obligate anaerobes.
Few species grow in the presence of small amounts of air.
However their growth is very slow in normal atmospheric conditions.
They are normally occur in soil, water and decomposing plant and animal matter. Most species are saprophytes.
They play an important role in putrefaction which is an important natural process.
Some Clostridia are commensals of the animal and human gut.
As an example Clostridium perfringens can be taken.
These organisms and other intestinal flora rapidly initiate the decomposition of the bodies after death of the host.
Medically important species are Clostridium tetani, Clostridium botulinum, and Clostridium perfringens.
They mainly cause gas gangrene or food poisoning.
Clostridium difficile also a medically important species.
The clostridia are large, straight rods. They have rounded ends.
In stained smears from cultures or wounds, there are pleomorphic forms.
Filaments or elongated cells and club and spindle shaped forms can be seen.
The meaning of Latin word Clostridium is “Little spindle”.
Clostridia have saccharolytic and proteolytic properties.
Many species produce highly toxic substances. Some toxins are toxic to nervous system called as neurotoxins.
Neurotoxins are produced by C. tetani and C. botulinum. The gas gangrene producing clostridia like C. perfringens produce histotoxic substances which attack to soft tissues.
C. difficile and some strains of C. perfringens produce enterotoxins.
Transmission
Transmission occurs in different ways.
Some species transmitted by the spores in the soil. These spores enter via wounds.
Some species transmitted as exotoxins when foods are ingested.
Some strains cause diseases due to the inappropriate usage of antibiotics.
Due to that suppressing of normal flora, clostridia attack the colon mucosa.
Clinical findings
Different toxins produced by clostridia act in different ways.
Some toxins causes spastic paralysis and flaccid paralysis in muscles.
In cytotoxic producing infections Pain, edema, cellulitis, and gangrene occur in the wound area. Mortality rates are high
According to the shape and location of spores organisms can be identified.
To identify some clostridia animal inoculation is done.
Mainly identification is done by gram stained smears. But the organisms can be cultured anaerobically.
Sugar fermentation tests are useful for the identification of organisms.
Clostridium perfringens can be differentiated by the double zone of hemolysis on blood agar.
Most of the times serologic tests are not useful. For the identification of exotoxins enzyme-linked immunosorbent assay (ELIZA) and tissue cultures also used.
By observing the dying of cells in tissue cultures due to cytotoxicity confirms the identification.
PCR test also used for the identification.
Treatment
Immune globulins (antitoxins) are used to neutralize the toxin.
Antibiotics are not used widely as they do not give good results.
Metronidazole or penicillin G can be given as antibiotics.
Clostridia also sensitive to the antibiotics Vancomycin, Carbapenems, Tetracyclines and so on.
Prevention
Toxoid vaccine is given to prevent the Tetanus caused by C. tetani.
Proper canning, storing and cooking of food is necessary to prevent the food poisonings.
Proper usage of antibiotics is useful to prevent the diseases caused by C. difficile.
No responses yet