Naegler’s reaction is shown by
Correct Answer: Clostridium perfringens
Description: Ans. b (Clostridium perfringens) (Ref. Ananthanarayan, Microbiology, 8th/ p. 256)When Cl. perfringens is grown on a medium with the antitoxin spread on one half of plate, colonies on the other half without antitoxin will be surrounded by a zone of opacity. There will be no opacity around the colonies on the half of the plate with the antitoxin; due to specific neutralization of alpha toxin. This is known as Naegler reaction.CLOSTRIDIUM PERFRINGENS (I.E., CLOSTRIDIUM WELCHII)# Clostridia are ubiquitous gram-positive, spore-forming, obligate anaerobes.# In human, Clostridia normally reside in GIT and in female genital tract. They are present in normal colonic flora at concentration of 109 to 1010 per gram and are excreted in faeces.# C. perfringens is the most common of the clostridial species isolated from tissue infections and bacteremia. 80% cases of gas gangrene are caused by C. perfringens. Is an anaerobic gram positive, spore-bearing bacillus. Gas gangrene producing strains of C. perfringens produce spores that are heat-labile.# Clostridium welchii is most frequently encountered (60%) in cases of gas gangrene. Clostridium novyi and Clostridium septicum (20-40%) are next common. Clostridium tetani do not cause gas gangrene.# Other Clostridia that can cause are C. bifermantans, C. sporogenes, C. fallax, and .C. histolyticum.# Major toxins of Cl. Perfringens (i.e. Cl. welchii) are: Alpha (is phospholipase ), Beta, Epsilon and Iota.# The alpha toxin produced by C. perfringens has been associated with gas gangrene and is known to be hemolytic, to destroy platelets and PMN leukocytes and cause widespread capillary damage. It is the principal toxin, a phospholipase C (Lecithinase).# Two factors are essential for development of severe disease, tissue necrosis and low oxidation-reduction potential.# Exposure of all the affected muscles with debridement of devitalized muscle tissue is the treatment of choice though systemic antibiotics (penicillin is the drug of choice) and hyperbaric oxygen are useful adjuncts.# Anti-gas gangrene serum is of doubtful value.Additional Educational Points:# Botulism is caused by protein neurotoxins elaborated by the Clostridium botulinum anaerobic gram-positive organism. These organisms form spores that are found in soils and marine environments throughout the world.# Eight toxin types have been described; each can be inactivated by cooking at high temperatures.
Category:
Microbiology
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