Microbiology Of Anthrax

Anthrax is an acute infection that usually affects the skin, lungs, and the digestive tract.

This disease is caused by the spore- forming, rod- shaped bacterium known as Bacillus anthracis. The gram positive spores of Bacillus anthracis are usually spread to humans from livestock, especially from goats, cows, and sheep. This type of infection can not spread from person to person. The dormant spores of Bacillus anthracis can live in soil and animal products, such as leather, for many years and is not easily killed by heat or cold. Once these spores are eaten by the livestock, they are quickly activated and the bacteria reproduce. The exposed animal usually dies, and the bacteria is returned to the soil and water as spores, creating an on going cycle. Although humans are more susceptible to this infection through the skin (cutaneous), it can also result from inhalation, or from eating contaminated meat.

The most common form of infection is known as cutaneous anthrax and results in about ninety five percent of all cases. Cutaneous anthrax usually occurs when bacteria from infected animal products, such as carcasses or wool, enter a break in the skin. This skin infection begins as a painless red bump similar to that of an insect bite. After about one to five days, the bump forms a blister that eventually breaks open to form a eschar (a black scab). Lymph nodes in the infected area may swell and the person may experience fever, nausea, muscle aches, headaches, and vomiting. Death from cutaneous anthrax is rare with the appropriate antimicrobial therapy. One out of five people who contract cutaneous anthrax and are left untreated will die.

Gastrointestinal tract anthrax, or anthrax of the digestive tract is not very common and has not been known to have occurred in the United States. When a person eats contaminated meat, the bacterium Bacillus anthracis begins to grow in the throat, mouth, or intestines. The bacteria releases toxins that causes excessive bleeding and tissue death. Symptoms of gastrointestinal anthrax would usually include fever, sore throat, vomiting, abdominal pain, and bloody diarrhea. This form of anthrax infection is fatal if not treated immediately.

Inhalation anthrax, also known as pulmonary anthrax (woolsorter's disease), results from inhalation of the anthrax bacterial spores. The spores multiply near the lungs, in the lymph nodes. Toxins produced by the bacteria cause these lymph nodes to swell, burst, and bleed, thus spreading the infection to the lungs and other nearby organs. Infected fluid gathers in the lungs and in the gap between the lungs and the chest wall. For the first two days, the symptoms of pulmonary anthrax resemble those of a common cold or sore throat. The person soon develops severe breathing problems, sweating, a high fever, and suddenly followed by shock and coma. A release of toxins occurs throughout the brain and meninges. Once the bacteria have reached this stage, treatment is difficult, and death is usually the result. Even with early treatment, most infected people die within twenty four to thirty six hours after severe symptoms begin. Ninety nine percent of untreated patients die from gastrointestinal anthrax.

Treatment of anthrax begins with preventing it among people who are at a high risk of being infected. An anthrax vaccine is currently being given to protect veterinarians, livestock handlers, postal workers, and employees of textile mills that process animal products. Since anthrax has the potential of being used as biological warfare, most members in the military are also vaccinated. This vaccine consists of filtered proteins and other components of a weakened Bacillus anthracis strain absorbed to aluminum hydroxide. There have been over 1.25 million people who have received this vaccine without any serious adverse reaction. Still, health experts do not recommend giving the vaccine to the general public because of the rarity of anthrax and the adverse side affects of the vaccine. Preventative treatment can also be carried out with antibiotics. People exposed to anthrax can be given oral ciprofloxcin or doxycycline, if the

bacteria's susceptibility to penicillin is unknown. If susceptibility to penicillin is found, oral amoxicillin can be used as a preventative treatment in children.

Actual anthrax infection can be treated if diagnosed early. However, much of the time, infected people confuse early symptoms with more common infections and do not seek out medical assistance. With the exception of cutaneous anthrax, gastrointestinal and inhalation anthrax are often mistaken for common illnesses Once severe symptoms appear, destructive anthrax toxins have already risen to

...