Mycobacterium Haemophilum Workup

Updated: Oct 07, 2015
  • Author: Natalie C Klein, MD, PhD; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
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Workup

Laboratory Studies

Evaluate the CBC count, liver enzymes, and serum electrolyte levels, including creatinine.

Acid-fast bacillus smear and culture

M haemophilum is a slow-growing, acid-fast–positive, nontuberculous mycobacterium that requires media supplemented with ferric iron–containing compounds and grows best at 30-32°C. Growth on solid media usually takes 2-3 weeks. The organism typically does not stain with Gram stain.

Aspirate of lesions may reveal acid-fast bacilli.

Perform an acid-fast bacillus (AFB) smear on excised lymph nodes. Culture a specimen at 30-32°C in media supplemented with iron or heme.

In patients with septic arthritis and osteomyelitis, submit synovial fluid specimens and bone biopsy samples for AFB smear and culture. Synovial fluid is usually purulent, and M haemophilum may be isolated from the fluid.

Submit sputum from immunosuppressed patients with pneumonia for AFB smear and culture. M haemophilum can be cultured from the blood of some patients with AIDS using special isolator tubes.

In appropriate clinical settings (eg, skin lesions, lymphadenopathy), informing the mycobacteriology laboratory to culture for M haemophilum may be useful. Iron must be added to grow this organism.

M haemophilum is unlikely to be a saprophyte (an innocent bystander) or a laboratory contaminant in the appropriate clinical setting.

Polymerase chain reaction (PCR)–restriction endonuclease analysis has been used for direct identification of M haemophilum in clinical specimens from immunocompromised patients. [35, 36, 37]

M haemophilum –specific PCR has been used to diagnosis M haemophilum cervicofacial lymphadenitis in children and was superior to culture in one series of patients from the Netherlands. [38]

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Imaging Studies

Radiography of involved joints or bone may demonstrate soft tissue swelling and lytic lesions. Chest radiograph findings are abnormal in patients with pneumonia. Unilateral or bilateral infiltrates may appear.

CT scans of the chest may reveal abnormalities that are not revealed with chest radiography. Regular cuts of 5-7 mm should be sufficient; high-resolution CT scan is rarely necessary.

MRI demonstrates medullary lesions and cortical disruption.

Diagnosis has been made using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) scanning. [39]

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Other Tests

In children with lymphadenitis a tuberculin skin test result with purified protein derivative (PPD) of tuberculosis may be positive; however, it is rarely larger than 9 mm. [40]

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Procedures

Aspirate of lesions may reveal AFB.

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Histologic Findings

Biopsy specimens of skin lesions show granulomatous panniculitis and caseating or noncaseating granulomas. Patients with AIDS have poorly formed granulomas. A neutrophilic infiltrate with multinucleated giant cells may be observed. AFB smear results are usually positive, revealing large, pleomorphic, or curved AFB.

Lymph node biopsy may reveal granulomas, necrosis, granulating tissue, or multinucleated giant cells, and the specimen may be smear-positive for AFB.

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