Mycobacterium avium subspecies

Mycobacterium is often found in patients with AIDS, one cause of night sweats, due to the vulnerability of their immune system. The combination of MAC and aids make it very difficult eliminate due to antimicrobial resistance and unclear knowledge of acquisition. Sweating is usually a problem during sleep with this disorder.

Definition

Mycobacterium avium subspecies paratuberculosis is a pathogenic bacteria in the genus Mycobacteria. It is often abbreviated MAP, M. paratuberculosis, or M. avium sub. paratuberculosis.

MAP causes Johne's disease in cattle and ruminants, and it has long been suspected as a causative agent in Crohn's disease in humans.

Recent studies have shown that MAP present in milk can survive pasteurization, which has raised human health concerns due to the widespread nature of MAP in modern dairy herds. MAP is heat resistant and it is capable of sequestering itself inside white blood cells, which may contribute to its persistence in milk. It has also been reported to survive chlorination in municipal water supplies.

Even though MAP is hardy, it is slow growing and "fastidious", which means it is difficult to culture. Many negative studies for MAP presence in living tissue, food, and water have used culture methods to determine whether the bacteria is present. Due to recent advances in our knowledge of the bacterium, some or all of these studies may need to be re-evaluated on the basis of culture methodology.

MAP, like most mycobacteria, is difficult to treat. It is not susceptible to anti-tuberculosis drugs (which can generally kill Mycobacterium tuberculosis), but can only be treated with a combination of antibiotics such as Rifabutin and a macrolide such as Clarithromycin. Treatment regimes can last years.

Clinical Features

Several different syndromes are caused by Mycobacterium avium complex (MAC). Disseminated infections are usually associated with HIV infection. Less commonly, pulmonary disease in nonimmunocompromised persons is a result of infection with MAC. In children, the most common syndrome is cervical lymphadenitis.

Etiologic Agent

Mycobacterium avium complex (comprising M. avium and M.intracellulare).

Incidence

Not reportable. Population-based data available for Houston and Atlanta metropolitan areas suggest a rate of 1/100,000/year. Incidence is decreasing among HIV- infected patients as a result of new treatment modalities e.g., combination therapy with nucleoside reverse transcriptase inhibitors and protease inhibitors, as well as antimycobacterial prophylaxis.

Sequelae

In HIV infected persons, manifestations include night sweats, weight loss, abdominal pain, fatigue, diarrhea, and anemia.

Transmission         Although the mode of transmission is unclear, MAC is most likely environmentally acquired.

Risk Groups          HIV-infected persons. Rarely in children or nonimmuno-compromised persons.

Surveillance MAC is not nationally reportable. Currently under active surveillance in the Houston and Atlanta metropolitan areas.

Trends

Incidence is decreasing because of changes in treatment for HIV-infected patients; however, antimicrobial resistance may be increasing.

Challenges   Antimicrobial resistance and better treatment for affected persons. Unclear knowledge of acquisition of MAC from the environment.

Opportunities

Reduction in MAC infection as a significant cause of morbidity and mortality in HIV-infected patients as a result of changes in available therapies.