Tetanus is caused by the neurotoxin tetanospasmin, which is produced by the Gram-positive, anaerobic bacillus Clostridium tetani. The spores from C. tetani are ubiquitous in soil worldwide and most often enter through wound tissue, either traumatically or by inoculation of a pre-existing wound. In countries with poor access to vaccination and sterile medical care, it is a known complication of birthing. After wound tissue necrosis begins, giving the bacteria an environment to germinate and produce tetanospasmin, the neurotoxin then enters peripheral nerves, moving proximally to the spinal cord and brainstem. Ultimately, tetanospasmin creates excessive motor neuron discharges by blocking inhibitory interneurons.