Tetanus pathophysiology: Difference between revisions
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[[ | [[Image:Clostridium tetani bacteria.jpg|center|thumb|Group of Clostridium tetani bacteria, responsible for causing tetanus in humans]] | ||
Image:Clostridium tetani bacteria.jpg|center|thumb|Group of Clostridium tetani bacteria, responsible for causing tetanus in humans]] | |||
C. tetani usually enters the body through a [[wound]]. In the presence of [[anaerobic]] (low oxygen) conditions, the spores [[germinate]]. Toxins are produced and disseminated via [[blood]] and [[lymphatics]]. [[Toxins]] act at several sites within the [[central nervous system]], including [[peripheral]] motor end plates, [[spinal cord]], and [[brain]], and in the [[sympathetic nervous system]]. The typical clinical manifestations of tetanus are caused when tetanus toxin interferes with release of [[neurotransmitters]], blocking inhibitor impulses. This leads to unopposed muscle contraction and spasm. Seizures may occur, and the autonomic nervous system may also be affected. | C. tetani usually enters the body through a [[wound]]. In the presence of [[anaerobic]] (low oxygen) conditions, the spores [[germinate]]. Toxins are produced and disseminated via [[blood]] and [[lymphatics]]. [[Toxins]] act at several sites within the [[central nervous system]], including [[peripheral]] motor end plates, [[spinal cord]], and [[brain]], and in the [[sympathetic nervous system]]. The typical clinical manifestations of tetanus are caused when tetanus toxin interferes with release of [[neurotransmitters]], blocking inhibitor impulses. This leads to unopposed muscle contraction and spasm. Seizures may occur, and the autonomic nervous system may also be affected. | ||
Revision as of 19:24, 22 May 2017
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The bacteria that causes tetanus, Clostridium tetani is introduced into the human body usually by a wound. The toxins produced by the bacterium, utilize the blood and/or lymphatics to gain access to target tissues. The toxins can act at various places in the central nervous system, including the spinal cord, peripheral motor end plates, and the brain. They can also act on the sympathetic nervous system.
Pathophysiology
Tetanus is an acute, often fatal, disease caused by an exotoxin produced by the bacterium Clostridium tetani. It is characterized by generalized rigidity and convulsive spasms of skeletal muscles. The muscle stiffness usually involves the jaw (lockjaw) and neck and then becomes generalized. C. tetani is a slender, gram-positive, anaerobic rod that may develop a terminal spore, giving it a drumstick appearance. The organism is sensitive to heat and cannot survive in the presence of oxygen. The spores, in contrast, are very resistant to heat and the usual antiseptics. They can survive autoclaving at 249.8°F (121°C) for 10–15 minutes. The spores are also relatively resistant to phenol and other chemical agents. The spores are widely distributed in soil and in the intestines and feces of horses, sheep, cattle, dogs, cats, rats, guinea pigs, and chickens. Manure-treated soil may contain large numbers of spores. In agricultural areas, a significant number of human adults may harbor the organism. The spores can also be found on skin surfaces and in contaminated heroin. C. tetani produces two exotoxins, tetanolysin and tetanospasmin. The function of tetanolysin is not known with certainty. Tetanospasmin is a neurotoxin and causes the clinical manifestations of tetanus. On the basis of weight, tetanospasmin is one of the most potent toxins known. The estimated minimum human lethal dose is 2.5 nanograms per kilogram of body weight (a nanogram is one billionth of a gram), or 175 nanograms for a 70-kg (154lb) human.
C. tetani usually enters the body through a wound. In the presence of anaerobic (low oxygen) conditions, the spores germinate. Toxins are produced and disseminated via blood and lymphatics. Toxins act at several sites within the central nervous system, including peripheral motor end plates, spinal cord, and brain, and in the sympathetic nervous system. The typical clinical manifestations of tetanus are caused when tetanus toxin interferes with release of neurotransmitters, blocking inhibitor impulses. This leads to unopposed muscle contraction and spasm. Seizures may occur, and the autonomic nervous system may also be affected.