From the Research
Mycobacterium szulgai is a species of nontuberculous mycobacteria (NTM) that does not cause false positive results on Interferon-Gamma Release Assays (IGRAs). Unlike many other NTM species such as M. marinum, M. kansasii, and M. gordonae which can cross-react with IGRA tests due to shared antigens with Mycobacterium tuberculosis, M. szulgai lacks the specific antigens (ESAT-6 and CFP-10) that IGRAs detect. This is clinically significant because it allows for more accurate differentiation between true tuberculosis infection and NTM colonization or infection when using IGRA testing, as supported by studies such as 1.
Key Points
- The specificity of M. szulgai regarding IGRA testing helps clinicians make more confident diagnostic decisions when evaluating patients with suspected mycobacterial infections.
- M. szulgai infections still require appropriate diagnosis and treatment as this organism can cause pulmonary disease, lymphadenitis, and other infections that may clinically resemble tuberculosis.
- Other NTM species, such as Mycobacterium avium complex (MAC), can cause false positive results on IGRA tests, as seen in studies such as 2.
- The T-SPOT.TB Test had a specificity of 94% for distinguishing between patients with prior MAC disease and prior tuberculosis disease, as reported in 2.
- The QuantiFERON-TB-Gold Test (QFT) is more specific than the Mantoux skin-test to discriminate between Mycobacterium tuberculosis (MTB) and non-tuberculous mycobacterial (NTM) infections, as shown in 1.
Considerations
- Healthcare providers should be aware of the potential for NTM infections to cause false positive results on IGRA tests, and consider the use of additional diagnostic tests to confirm the diagnosis.
- The treatment of NTM infections, such as those caused by M. avium complex, requires a comprehensive approach, including the use of multiple antibiotics, as discussed in 3.
- The diagnosis and treatment of NTM infections can be challenging, and require a thorough understanding of the epidemiology, pathogenesis, and management of these infections, as reviewed in 4.