Atypical tuberculosis diagnosis

Covering the complex terminology of Tuberculosis and other assoicated disease
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Atypical tuberculosis diagnosis

#1 Post by auntiebi0tic » Thu Jan 16, 2020 12:20 am

Clinical Diagnosis and Microbiologic Testing

Healthcare providers should have a high level of suspicion to diagnose illness caused by NTM because nonspecific symptoms are common and routine bacterial cultures are often inadequate to diagnose these infections. Time from exposure to clinical manifestation can be prolonged. Similarly, time from clinical manifestation to diagnosis may be delayed due to various factors including the failure to order appropriate tests.
Specific laboratory testing, such as acid-fast bacilli (AFB) stain and culture, should be ordered when NTM infection is suspected.
Culture of the site of infection is needed for definitive diagnosis. Examples include AFB culture of sputum or bronchial alveolar lavage for suspected pulmonary infections, AFB culture of wound for suspected skin infection, AFB culture of blood for disseminated infections, or AFB culture of appropriate tissue or body fluid for musculoskeletal infections or lymphadenitis.
AFB stain can detect the presence of mycobacteria. The laboratory will then perform additional testing to differentiate NTM from M. tuberculosis.
It may take several weeks for a laboratory to grow NTM by culture and identify the species.
Not all hospital labs have the infrastructure to identify NTM to the species-level. You may need to work with your laboratory to ensure testing is done at an appropriate reference laboratory.
Nucleic acid amplification tests (NAAT) can be used to classify NTM into groups or complexes and are also helpful in identifying M. gordonae, which is usually a contaminant. Further speciation using a testing method such as matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is highly encouraged. However, MALDI-TOF MS identification does not always generate an acceptable match. Sanger DNA sequencing should be used to supplement MALDI-TOF MS in instances where it fails to produce acceptable results.

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