Guidelines Summary
Below is a summary of the British Thoracic Society [26] and American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) guidelines for diagnosis and treatment of NTM infections, which are relevant to M kansasii infection. [26, 24]
British Thoracic Society Guidelines for the Workup and Treatment of Nontuberculous Mycobacterial Pulmonary Disease
Workup for nontuberculous mycobacterial infections
Sputum, induced sputum, bronchial washings, bronchoalveolar lavage, or transbronchial biopsy samples can be used to evaluate individuals suspected of having nontuberculous mycobacterial (NTM) pulmonary disease.
Whenever possible, less invasive sampling should be attempted first to minimize procedural risks.
Respiratory samples should be processed within 24 hours of collection (or refrigerated at 4°C if delays are anticipated).
Oropharyngeal swab culture or serology testing should not be used to diagnose NTM pulmonary infection.
If sputum cultures are negative but clinical suspicion of NTM infection is high, consider performing CT-directed bronchial washings to obtain targeted samples.
If individuals undergoing diagnostic evaluation for NTM infection are taking antibiotics that may impair NTM growth (eg, aminoglycosides, macrolides, tetracyclines, cotrimoxazole, linezolid), consider discontinuing these antibiotics 2 weeks before collecting samples.
A validated rapid method should be used to detect NTM in respiratory samples.
All respiratory samples should be stained using auramine-phenol after liquefaction and concentration and then examined by microscopy.
Respiratory tract samples should be cultured (following decontamination) on solid and liquid media in a ISO15189-accredited clinical laboratory for 8 weeks, extending to 12 weeks if necessary.
Routine use of non–culture-based detection methods is not recommended at the present time.
All NTM isolates from respiratory samples should be identified to at least species level using validated molecular or mass spectrometry techniques.
Drug susceptibility testing and reporting
Drug susceptibility testing and reporting should follow the Clinical Laboratory Standards Institute (CLSI) guidelines.
For M kansasii, rifampin susceptibility testing should be performed on an isolate prior to initiation of treatment and on subsequent isolates if the patient fails to respond to treatment or recultures M kansasii after culture conversion.
Rifampin-resistant M kansasii isolates should be tested against a wider panel of antibiotics to guide, but not dictate, treatment regimens.
A minimum of 2 sputum samples collected on separate days should be sent for mycobacterial culture when investigating an individual suspected of having NTM pulmonary disease.
Individuals suspected of having NTM pulmonary disease whose sputum samples are consistently culture-negative for mycobacteria should have CT-directed bronchial washings sent for mycobacterial culture.
Individuals suspected of having NTM pulmonary disease who are unable to expectorate sputum should have CT-directed bronchial washings sent for mycobacterial culture.
Transbronchial biopsies should not be performed routinely in individuals suspected of having NTM pulmonary disease.
Treatment recommendations for M kansasii infection
Rifampin-sensitive M kansasii pulmonary disease should be treated with rifampin, ethambutol, and isoniazid or a macrolide (clarithromycin or azithromycin) using a daily oral regimen.
Rifampin-resistant M kansasii pulmonary disease should be treated with a three-drug regimen guided, but not dictated by, drug susceptibility test results using a daily oral regimen.
Antibiotic treatment for M kansasii pulmonary disease should continue for a minimum of 12 months after culture conversion.
Diagnostic Criteria Based on American Thoracic Society/Infectious Disease Society of America Guidelines
In 1997, the American Thoracic Society (ATS) established diagnostic criteria for NTM lung disease, regardless of the host's HIV status. [28] These guidelines were revised and approved by the American Thoracic Society and Infectious Disease Society of America (IDSA) in 2007. [24]
M kansasii is considered a highly pathogenic mycobacterium, and many experts advise that M kansasii isolated from lungs or elsewhere almost always warrants treatment, especially in patients with HIV/AIDS and in other immunocompromised groups. The authors of the ATS/IDSA guidelines also acknowledge and suggest that the treatment decisions for M kansasii should be made carefully, even if some specimens are not positive for M kansasii or if multiple specimens are not available, and they recommend expert consultation in the decision-making process.
The general diagnostic criteria for all NTM pulmonary infections based on 2007 ATS/IDSA guidelines are summarized below. [24]
Clinical criteria
Both of the following clinical criteria are required to establish a diagnosis of NTM lung disease:
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Pulmonary symptoms, nodular or cavitary opacities on chest radiography, or a HRCT scan that shows multifocal bronchiectasis with multiple small nodules
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Appropriate exclusion of other diagnoses
Microbiologic criteria
One of the following microbiologic criteria is required for diagnosis of NTM lung disease:
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Positive culture results from at least 2 separate expectorated sputum samples (If these culture results are nondiagnostic, consider repeat sputum AFB smears and cultures.)
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Positive culture result from at least one bronchial wash or lavage
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Transbronchial or other lung biopsy sample with mycobacterial histopathologic features (granulomatous inflammation or AFB) and positive culture for NTM; alternatively, a biopsy sample showing mycobacterial histopathologic features (granulomatous inflammation or AFB) and one or more sputum or bronchial washings that are culture-positive for NTM
The ATS/IDSA guideline also recommends the followings for diagnosis:
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Expert consultation should be obtained when NTM that are either infrequently encountered or that usually represent environmental contamination are recovered.
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Patients with suspected NTM lung disease but who do not meet the diagnostic criteria should be observed until the diagnosis is firmly established or excluded.
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A diagnosis of NTM lung disease does not automatically necessitate the institution of therapy, which is a decision based on potential risks and benefits of therapy in individual patients.
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Chest radiograph in a patient with Mycobacterium kansasii pulmonary infection shows left lower lung infiltrates.
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Chest CT scan in a patient with Mycobacterium kansasii pulmonary infection.
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Chest radiograph in a patient with classic right upper lobe cavitary lung disease secondary to Mycobacterium kansasii infection. Courtesy of Raj Sreedhar, MD, SIU School of Medicine, Springfield, IL.
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CT thorax of a patient with classic right upper lobe cavitary lung disease secondary to Mycobacterium kansasii infection. Courtesy of Raj Sreedhar, MD, SIU School of Medicine, Springfield, IL.
