Tuesday, February 09, 2010

General FAQ on Atypical Mycobacterium.

This is a general FAQ on Atypical Mycobacterium infections. Please do not hesitate to get in contact if you have any questions or information which you would like to see answered or added.

What are atypical mycobacteria?

Atypical mycobacteria are a group of bacteria that are widely distributed in nature. They can be found in water, soil, unpasteurised milk, and animals and may cause disease in humans. These microbes are also found  in: tap water, fresh and ocean water, milk, bird droppings, soil, and house dust. The manner in which these bacteria are transmitted is not completely understood. There is no evidence that they are transmitted from person to person.

Are these the same organisms that cause tuberculosis?

No. Atypical mycobacteria do not cause tuberculosis. These bacteria belong to the same family as Mycobacterium tuberculosis (MTB) but only MTB causes tuberculosis. Atypical mycobacteria in this family include other species such as M. avium, M. intracellularae, M. kansasii, M. xenopi, and M. fortuitum.

Do these organisms cause disease?

Many people become infected with and harbor atypical mycobacteria without any symptoms or evidence of disease. In some individuals, however, infection with these organisms may result in disease involving the lungs, skin, lymph nodes, or other parts of the body. These organisms may also infect open wounds. One species, M. paratuberculosis has been suggested as the cause of Crohn’s disease. Risk factors for disease from these organisms include a weakened immune system, lung diseases, heavy smoking, and alcohol abuse.

What are the signs and symptoms of atypical mycobacterial infection?

Patients with disease caused by atypical mycobacteria commonly have respiratory symptoms, such as cough and increased sputum production, and an abnormal chest x-ray. Patients may also experience fever, weakness, and weight loss. These symptoms may be similar to tuberculosis so further medical and laboratory tests are needed for an accurate diagnosis. A weakened immune system, underlying illness or tissue damage may make a person more likely to develop disease if infected with atypical mycobacteria. Symptoms include shortness of breath, fever, night sweats, weight loss, appetite loss, fatigue, and progressively severe diarrhoea, stomach pain, nausea and vomiting. If the infection spreads to the brain, the patient may experience weakness, headaches, vision problems, and loss of balance. In CF the recent introduction of high dose ibuprofen raises concerns about its possible contribution to the progression of the infection, although this has not been proved  and can only be speculated at this time[1].

Can people with atypical mycobacterial disease infect others?

With the exception of organisms causing skin lesions, there is very little evidence of person-to-person spread of these organisms. Individuals with respiratory disease from atypical mycobacteria do not readily infect others and, therefore, do not need to be isolated from others. The majority of atypical mycobacterial infections come from the environment and is not spread from person to person. Exceptions include organisms in skin lesions, M. kansasii, and possibly M. simiae.

How is disease caused by atypical mycobacteria treated?

Treatment is based on results of laboratory testing that will identify an effective antibiotic for treatment. Preventive treatment of close contacts of persons with disease caused by atypical mycobacterium is not necessary.

How do I find out if I am infected?
The diagnosis is made from the patient's symptoms and organisms grown in culture from the site of infection. In cases of lung infection, a diagnostic work-up will include a chest x ray, CT scan and tests on discharges from the respiratory passages (sputum).

How can you prevent getting atypical mycobacteria? 
Since these mycobacteria are found in most city water systems, in hospital water supplies, and in bottled water, at-risk persons should boil drinking water. Persons at risk should also avoid raw foods, especially salads, root vegetables, and unpasteurised milk or cheese. Fruits and vegetables should be peeled and rinsed thoroughly. Conventional cooking (baking, boiling or steaming) destroys mycobacteria, which are killed at 176°F (80°C).

Treatment protocols
Leeds Protocol to Treating Atypical Mycobacterium infections in Cystic Fibrosis patients can be found here. (PDF File).

It is not clear what the optimum treatment regimens for NTMs (Non-Tuberculosis Mycobacterium) are and much of the evidence is provided by in-vitro rather than in-vivo studies. They are often resistant to most of the antibiotics commonly used to treat other infections in CF and to standard treatments used to treat Mycobacterium tuberculosis. Most isolates of M. avium appear susceptible to macrolides, such as clarithromycin and azithromycin, on initial isolation and these are most effective when combined with two or three other drugs, such as rifampicin and ethambutol. The most active drug against rapid growers is amikacin, although other agents with in vitro activity include cefoxitin, clarithromycin, imipenem and linezolid. M abscessus is more resistant than other members of the group. Tigecycline has in vitro activity against rapid growers, but not against M. avium. There is some evidence that patients with defects in immunological pathways, particularly those associated with interferon, may be more susceptible to infection with NTMs.

As a rule atypicals do build resistance to antibiotics quite quickly but they also 'forget' the resistance as quickly. Short sharp doses of antibiotics with gaps between is preferred.

*I have included a source and a PDF file in this post which may be helpful to you.

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