Bacillus anthracis: anthrax
Bacillus anthracis: anthrax
Bacillus anthracis: anthrax
Few cases of anthrax are seen in western countries but about100000 cases occur in the world each year. The Grampositiverods of B. anthracis give rise to endospores in conditionsunfavourable for replication, and these can survivefor many years in the soil. Making use of this property theyhave been used in warfare in both world wars during the20th century, and as a terrorist weapon on other occasions.The spores can contaminate the hides, hooves and bones ofherded animals, and contact with these can cause cutaneousanthrax both in the endemic areas and in industrializedcountries to which these animal materials are taken forprocessing. Bacilli are found in the tissues of animals dyingof systemic infections. Transmission to humans is by skincontact with infected material such as hides or meat, byinhalation of spores or by ingestion of infected meat,causing skin, respiratory and gastrointestinal disease,respectively. Disease onset is within 5 days in all forms, andis usually about 2 days. Pathogenesis depends on the expressionof virulence factors coded by two plasmids. Oedematoxin, lethal factor and protective antigen are the productsof these plasmids. Endospores ingested by macrophagesbecome vegetative and rupture macrophages, releasingorganisms that replicate further in lymphatics and in thebloodstream, producing massive septicaemia, up to 108/mL.Expression of virulence factors is increased by elevated hosttemperature.
Cutaneous anthrax Cutaneous anthrax is the most common form of the disease and the most benign. A red macule or papule develops atthe contact site, e.g. the neck of a meat carrier in a slaughterhouse.A pruritic vesicle develops, satellite lesionsappear, and the whole evolves into an ulcer, then a blackeschar. There is usually some surrounding oedema, butoccasionally there is a severe local reaction with grossoedema, and general toxaemia ensures. Despite the sizeand appearances of the lesion it is painless unless secondarily infected.
Inhalation anthrax At first there are mild general symptoms and a nonproductivecough. Improvement over a few days is followedby abrupt decline. The patient rapidly becomes veryill, with cough, fever, tachypnoea, cyanosis, tachycardia,vomiting and chills. Diffuse crackles are heard over theaffected lung fields. The spleen may enlarge. There ismassive enlargement and oedema of the neck and chestwall. Untreated, the patient often dies within 24 hours.There is an 80% mortality in this form.
Gastrointestinal anthrax This may occur in clusters if a family or tribal group eatcontaminated meat. Following ingestion, lesions can occuranywhere in the gastrointestinal tract, including the throat.There is diffuse abdominal pain, with rebound tenderness.Ascites can develop, and with this the abdominal paindeclines. There are varying degrees of gastroenteritis withhaemorrhage, and mortality is high.
Symptoms resolveafter about 14 days in those surviving. Haematogenous disseminationof organisms can sometimes cause meningitiswith bloody CSF.
Diagnosis Many cases probably go undiagnosed in the tropics andsubtropics. The cutaneous form is probably most oftendiagnosed on the clinical appearances. Occupational exposuremay be suspected from the nature of the patient's job.The severity of a pneumonic illness may prompt considerationof pulmonary anthrax.The organisms are readily found in Gram-stained smearsfrom skin lesions and grow well in blood culture samples.
Management The cutaneous form may resolve without treatment. PenicillinV, 2 g/day in divided doses, is very effective. For moresevere infections benzyl penicillin, 4.8-7.2 g in divideddoses intravenously, is used. When the patient is allergicto penicillin, ciprofloxacin 400 mg twice daily intravenouslyor 500 mg twice daily by mouth, tetracycline 2 g/day or chloramphenicollOOmg/kg/day in divided doses orally or intravenouslycan be used. The latter is given to children andpregnant women. Pulmonary or intestinal cases will requiresupportive care, with maintenance of oxygenation, givingnormal saline, plasma or blood transfusions as necessary tomaintain blood volume and hydration.
Prevention is by elimination of the infection fromanimals. Immunization is available when there is danger ofoccupational exposure. Vaccines are available for thosewho may be exposed to anthrax.
Many Uses For Clear Glass Vases: What You Can Do With Them Experience The Fun Of Hiking With A Gps ziyang Ziyang, Shaanxi Slate Industry Schnell Abnehmen Tipps Captains Share Marine Gps Schnell Abnehmen In 2 Wochen Glass Blowing Art Throwing A Margaritaville Birthday Theme Party That Will Knock Everyone's Socks Off! Trout Rigs are Lacking If You Don't Have Synthetic Trout Baits Watch FIFA World Cup 2010 semi finals How To Find An Orthodontist How To Lose A Pound A Day Opc-3 - The Indispensible Supplement