tailieunhanh - Chapter 133. Tetanus (Part 1)

Harrison's Internal Medicine Chapter 133. Tetanus Definition Tetanus is a neurologic disorder, characterized by increased muscle tone and spasms, that is caused by tetanospasmin, a powerful protein toxin elaborated by Clostridium tetani. Tetanus occurs in several clinical forms, including generalized, neonatal, and localized disease. †A contributor to HPIM since the 12th edition, Dr. Abrutyn passed away on February 22, 2007. Etiologic Agent C. tetani is an anaerobic, motile, gram-positive rod that forms an oval, colorless, terminal spore and thus assumes a shape resembling a tennis racket or drumstick. The organism is found worldwide in soil, in the inanimate environment, in animal feces,. | Chapter 133. Tetanus Part 1 Harrison s Internal Medicine Chapter 133. Tetanus Definition Tetanus is a neurologic disorder characterized by increased muscle tone and spasms that is caused by tetanospasmin a powerful protein toxin elaborated by Clostridium tetani. Tetanus occurs in several clinical forms including generalized neonatal and localized disease. fA contributor to HPIM since the 12th edition Dr. Abrutyn passed away on February 22 2007. Etiologic Agent C. tetani is an anaerobic motile gram-positive rod that forms an oval colorless terminal spore and thus assumes a shape resembling a tennis racket or drumstick. The organism is found worldwide in soil in the inanimate environment in animal feces and occasionally in human feces. Spores may survive for years in some environments and are resistant to various disinfectants and to boiling for 20 min. Vegetative cells however are easily inactivated and are susceptible to several antibiotics including metronidazole and penicillin. Tetanospasmin is formed in vegetative cells under plasmid control. With autolysis the single-chain toxin is released and cleaved to form a heterodimer consisting of a heavy chain 100 kDa which mediates binding to and entry into nerve cells and a light chain 50 kDa which blocks neurotransmitter release. The genome of C. tetani has been sequenced. The amino acid structures of the two most powerful toxins known botulinum toxin and tetanus toxin are partially homologous. Epidemiology Tetanus occurs sporadically and almost always affects unimmunized persons partially immunized persons and fully immunized individuals who fail to maintain adequate immunity with booster doses of vaccine may be affected as well. Although tetanus is entirely preventable by immunization the burden of disease worldwide is great. Tetanus is a notifiable disease in many countries but reporting is known to be inaccurate and incomplete particularly in developing countries. As a result the World Health Organization .