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atypical mycobacterioses

Thursday 7 December 2006

atypical mycobacterial infection



- histiocytic infiltration in atypical mycobacteriosis

Atypical mycobacterial infection has been described in the medical literature since the mid 1950s.

The development and introduction of a rapid radiometric mycobacterial detection system has advanced the field of mycobacteriology over the past 20 years. This method has allowed the distinction of Mycobacterium tuberculosis from other mycobacteria and enabled the performance of antimicrobial susceptibility testing of mycobacteria.

The increased frequency of atypical mycobacterial infection stems from advances in the diagnostic procedures concerning the infection paired with the prevalence of mycobacterial disease in immunocompromised patients infected with the human immunodeficiency virus (HIV).

In the immunocompetent pediatric host

Suppurative cervical or submandibular lymphadenopathy that produces or does not produce systemic symptoms is the most common presentation of atypical mycobacterial infection caused by Mycobacterium avium-intracellulare and Mycobacterium scrofulaceum in the immunocompetent pediatric host.

Immunocompetent children with adenitis secondary to MAC present with suppurative adenitis that may or may not produce constitutional symptoms such as fever. Fistula may be present with coalescence of involved cervical or mandibular nodes.

In the immunodeficient host

In a cohort of children infected with HIV prospectively monitored by Hoyt et al in 1992, recurrent and persistent fever and chronic anemia were the most common signs and symptoms, followed by chronic diarrhea and a history of recurrent abdominal pain with disseminated Mycobacterium avium complex (MAC) disease.

In immunocompromised children with HIV/AIDS, no pathognomonic signs are present.

Physical examination may reveal that a debilitated patient has a history of failure to gain weight, chronic fatigue, chronic diarrhea, and recurrent abdominal pain. Hepatosplenomegaly may be present.

Early during disseminated MAC disease, some patients may not have fever and may not appear acutely or chronically ill.

Weight loss, failure to gain weight, and wasting syndrome are part of the long-term presentations of disseminated MAC disease in immunocompromised children.

Other signs and symptoms include leukopenia, hepatosplenomegaly, and persistent generalized lymphadenopathies. Ulcerative lesions of the colon and mesenteric disease with abscess formation have been reported.

Primary cutaneous infections with MAC are rare; most cases are caused by dissemination, with manifestations including scaling plaques, crusted ulcers, ecthymalike lesions, verrucous ulcers, inflammatory nodules, panniculitis, pustular lesions, and draining sinuses.

Skeletal infections

Atypical mycobacteria may cause skeletal infections. A large outbreak of spinal infections after discovertebral surgery was reported in 2001.

Tenosynovitis, multifocal osteomyelitis, septic arthritis, protracted carpal tunnel syndrome, and spondylitis implicating Mycobacterium chelonae, Mycobacterium kansasii, MAC, or Mycobacterium xenopi have been described in the literature.

Other infections

Numerous atypical mycobacterial infections are known. The most common forms of diseases are chronic pulmonary disease resembling tuberculosis (occurring mainly in adults), cervical adenopathy in children, skin and soft tissue infections, and disseminated disease in immunocompromised persons.

Lymphadenitis is the most common manifestation in children.

However, progressive immunodeficiency due to infection with HIV appears to be the most significant factor for disseminated MAC disease.

A unique MAC syndrome that develops in patients with AIDS in the first 1-2 months following the initiation of HAART has been described by 3 groups of investigators.

The symptom consists of fever and focal MAC lymphadenitis, with a blood culture negative for mycobacteria in most cases. The symptom is also known as immune reconstitution syndrome.

It may occur in patients who already had subclinical MAC disease that becomes unmasked by HAART.

The atypical mycobacteria observed in children are Mycobacterium avium-intracellulare complex, Mycobacterium scrofulaceum, and, rarely observed in children with AIDS, Mycobacterium kansasii.

Keratitis and endophthalmitis after intravitreous injection of steroids or other ophthalmoscopic procedures secondary to Mycobacterium chelonae invasion have been reported.

Although most of those infections secondary to atypical mycobacteria have been described in the adult population, cases of cutaneous mycobacteriosis manifesting as cellulitis, skin abscess, or sporotrichoid lesions secondary to Mycobacterium chelonae abscessus and Mycobacterium kansasii have been reported.

Mycobacterium kansaii and Mycobacterium marinum have been reported in aquariumworkers.

Mycobacterium avium–associated typhlitis mimicking appendicitis has been described in an immunocompetent host.

Catheter-related infections are the most common nosocomial nontuberculous mycobacterial infections encountered.

The fast-growing atypical mycobacteria, such as Mycobacterium fortuitum, cause most catheter-related infections.

Patients with long-term central intravenous catheters are most susceptible. However, infections have occurred in patients with peritoneal and shunt catheters.

Local catheter site drainage; tunnel infections; and mycobacteremia, with or without fever, are the usual manifestations, but granulomatous hepatitis and, sometimes, pulmonary infiltrates have been observed.

Case reports of atypical mycobacterial infection in transplant patients due to Mycobacterium chelonae and Mycobacterium xenopi have been described in the medical literature.

Chronic granulomatous infections

Both rapidly growing and slow-growing species of NTM have been implicated in chronic granulomatous infections.

Those infections mostly involve tendon sheaths, bursae, bones, and joints after direct inoculation through accidental trauma, surgical incisions, or puncture wounds.

Tenosynovitis of the hand secondary to MAC and Mycobacterium marinum has been described. Osteomyelitis of the sternum caused by Mycobacterium abscessus has been found in clustered and sporadic outbreaks.

Mycobacterium fortuitum and Mycobacterium chelonae strains, also known as the rapidly growing organisms, have occasionally been implicated in wound, soft tissue, pulmonary, and middle ear infections.

Mycobacterium marinum

Mycobacterium marinum is the causative agent of swimming pool granuloma.

Buruli ulcer and Mycobacterium ulcerans

Buruli ulcer is a chronic ulcerative skin disease, caused by in the immunocompetent pediatric host Mycobacterium ulcerans, that mostly affects the limbs.

The lack of acute inflammatory response is typical and is likely due to an immunosuppressive toxin called mycolactone, which is produced by mycobacteria.

Buruli ulcer mainly affects children living in humid areas of the tropical rain forest. Following a microinjury, the organism penetrates the skin.

A subcutaneous nodule develops a few weeks later, followed by necrosis of the subcutaneous fat and finally by a large dermal ulceration. Constitutional symptoms are normally absent.


- atypical mycobacterial adenitis
- atypical mycobacterial dermatitis

Laboratory Studies

- Organisms from blood, biopsy material, bone marrow, and stools grow on routine bacterial media, but growth is best achieved using selective mycobacterial media, such as a Lowenstein-Jensen medium or Middlebrook 7K10 and 7K11 agar.

- Nucleic acid hybridization probes using target sequences or ribosomal RNA are available for rapid identification of clinical isolates.55

- Species can be identified using high-performance liquid chromatography or biochemical tests.

- Polymerase chain reaction (PCR)-restriction analysis of clinical isolates have been used for the identification of M kansasii.

- Disseminated Mycobacterium avium complex (MAC) disease is most commonly diagnosed using culture of blood and bone marrow or other normally sterile tissues or body fluids.

- Other ancillary studies, such as acid-fast bacilli smear or radiographic imaging of the abdomen or mediastinum for detection of lymphadenopathy, may provide supportive diagnosis information.

See also

- infectious diseases