Approach Considerations
At least three positive culture results or one positive AFB stain result with two positive culture results are required to consider a diagnosis of true M gordonae disease. One positive culture result from a sterile site is probably not enough to start treatment. All cases of possible M gordonae disease should be published in a medical journal.
Laboratory Studies
See the list below:
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Documentation of M gordonae disease
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Microbiologic characteristics, as follows:
Smear-positive specimens for acid-fast bacilli
Isolation of organism in large numbers, quantified as growth per culture in colony-forming units (ie, >100)
Repeated isolation of M gordonae (ie, more than twice)
Detection of specific biochemical characteristics (to prove identity)
Consideration of confirmation from a reference laboratory
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Isolation of M gordonae from a sterile source
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Positive result from tissue culture
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Histopathologic changes characteristic of M gordonae infection
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Repeat mycobacterial cultures of sputum, blood, bone marrow, and urine (if disease is suspected)
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Blood cultures to determine presence of mycobacterial organisms
Imaging Studies
Obtain a chest radiograph in patients with respiratory symptoms.
Use CT scanning of the lungs, abdomen, or both to evaluate for possible dissemination.
Consider performing abdominal ultrasonography.
Other Tests
The "3-2-1" rule is useful for a more accurate determination of disease as opposed to contamination or colonization without pathogenicity. To prove disease, one would want to see at least 3 cultures with M gordonae, 2 cultures with one positive acid-fast bacilli smear, or one culture from a sterile source such as blood, bone marrow, or pleural fluid.
Procedures
Fiberoptic bronchoscopy helps evaluate for infiltrates.
Consider obtaining biopsy specimens (eg, from bone marrow) to help diagnose possible dissemination.
Histologic Findings
Acid-fast stains are positive for M gordonae, and/or granulomas are present.
