It is the causative agent of the potentially fatal condition tetanus.
It is an obligate anaerobe, gram-positive, rod-shaped bacillus. It has a characteristic “drumstick” or “tennis racket” appearance due to a terminal endospore. It is endospore-forming and motile, with rotary peritrichous flagella.
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Disease occurs when spores enter the body, most commonly through cuts or breaks in the skin. It can also occur when non-sterile instruments contaminated with spores are used to cut the umbilical cord during birth, causing neonatal tetanus. “Skin popping” by drug addicts can also introduce spores and lead to tetanus.
Two toxins play a key role in pathogenesis and disease manifestations: tetanospasmin and tetanolysin.
Tetanospasmin is transported retrograde from the neuromuscular junction to the spinal cord. There, it inhibits the release of the inhibitory neurotransmitters GABA and glycine. This leads to hyperactivity of lower motor neurons, which manifests as muscle rigidity and spasms. Tetanolysin acts as a tissue lysin and breaks down tissues.
Tetanus can be neonatal (in newborns), cephalic (localized to the head region), local, or generalized. It presents with a stiff neck, opisthotonus (backward arching of the head, neck, and spine due to extreme spasm), trismus (lockjaw), and “risus sardonicus” (a grin-like facial expression due to sustained spasm of facial muscles). Generalized rigidity can cause apnoea and dysphagia, eventually leading to death.
Clinical evaluation is key for diagnosis. Organisms are rarely isolated from the wound site. On Gram stain, they show typical morphology with terminal endospores. If culture is done, it must be anaerobic only.
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