<P> Tetanus is often associated with rust, especially rusty nails . Although rust itself does not cause tetanus, objects that accumulate rust are often found outdoors or in places that harbour anaerobic bacteria . Additionally, the rough surface of rusty metal provides a habitat for C. tetani, while a nail affords a means to puncture skin and deliver endospores deep within the body at the site of the wound . An endospore is a non-metabolizing survival structure that begins to metabolize and cause infection once in an adequate environment . Hence, stepping on a nail (rusty or not) may result in a tetanus infection, as the low - oxygen (anaerobic) environment may exist under the skin, and the puncturing object can deliver endospores to a suitable environment for growth . </P> <P> Tetanus affects skeletal muscle, a type of striated muscle used in voluntary movement . The other type of striated muscle, cardiac, or heart muscle, cannot be tetanized because of its intrinsic electrical properties . </P> <P> The tetanus toxin initially binds to peripheral nerve terminals . It is transported within the axon and across synaptic junctions until it reaches the central nervous system . There it becomes rapidly fixed to gangliosides at the presynaptic inhibitory motor nerve endings, and is taken up into the axon by endocytosis . The effect of the toxin is to block the release of inhibitory neurotransmitters glycine and gamma - aminobutyric acid (GABA) across the synaptic cleft, which is required to check the nervous impulse . If nervous impulses cannot be checked by normal inhibitory mechanisms, the generalized muscular spasms characteristic of tetanus are produced . The toxin appears to act by selective cleavage of a protein component of synaptic vesicles, synaptobrevin II, and this prevents the release of neurotransmitters by the cells . </P> <P> There are currently no blood tests for diagnosing tetanus . The diagnosis is based on the presentation of tetanus symptoms and does not depend upon isolation of the bacterium, which is recovered from the wound in only 30% of cases and can be isolated from patients without tetanus . Laboratory identification of C. tetani can be demonstrated only by production of tetanospasmin in mice . Having recently experienced head trauma may indicate cephalic tetanus if no other diagnosis has been made . </P>

Which bacterial infection of the intestines is characterized by paralysis