[Lymphadenitis due to non-tuberculous mycobacteria: Experience over 15 years]

Development and Evaluation of an NTM-IGRA to Guide Pediatric Lymphadenitis Diagnosis

BACKGROUND

Diagnosis of nontuberculous mycobacteria (NTM) infections remains a challenge. In this study, we describe the evaluation of an immunological NTM-interferon (IFN)-γ release assay (IGRA) that we developed using glycopeptidolipids (GPLs) as NTM-specific antigens.

METHODS

We tested the NTM-IGRA in 99 samples from pediatric patients. Seventy-five were patients with lymphadenitis: 25 were NTM confirmed, 45 were of unknown etiology but compatible with mycobacterial infection and 5 had lymphadenitis caused by an etiologic agent other than NTM. The remaining 24 samples were from control individuals without lymphadenitis (latently infected with M. tuberculosis , uninfected controls and active tuberculosis patients). Peripheral blood mononuclear cells were stimulated overnight with GPLs. Detection of IFN-γ producing cells was evaluated by enzyme-linked immunospot assay.

RESULTS

NTM culture-confirmed lymphadenitis patient samples had a significantly higher response to GPLs than the patients with lymphadenitis of unknown etiology but compatible with mycobacterial infection ( P < 0.001) and lymphadenitis not caused by NTM ( P < 0.01). We analyzed the response against GPLs in samples from unknown etiology lymphadenitis but compatible with mycobacterial infection cases according to the tuberculin skin test (TST) response, and although not statistically significant, those with a TST ≥5 mm had a higher response to GPLs when compared with the TST <5 mm group.

CONCLUSIONS

Stimulation with GPLs yielded promising results in detecting NTM infection in pediatric patients with lymphadenitis. Our results indicate that the test could be useful to guide the diagnosis of pediatric lymphadenitis. This new NTM-IGRA could improve the clinical handling of NTM-infected patients and avoid unnecessary misdiagnosis and treatments.

Risk factors of non-tuberculous mycobacterial lymphadenitis in children: a case-control study

The aim of the present study is to clarify the association between environmental exposures and non-tuberculous mycobacterial (NTM) lymphadenitis, during the last decade, in a population of children. In children up to 14 years of age in a pediatric tertiary hospital, all cases of NTM lymphadenopathy with a specific microbiological diagnosis, from January 2004 to January 2015, were reviewed. This is a case-control study (1:5 proportion), in which the prevalence of environmental factors between cases and controls was compared by means of a multivariate logistic regression analysis. A total of 24 cases were diagnosed in the aforementioned period, and 18 of them included in the case-control study. Mycobacterium avium-intracellulare was the predominant mycobacterium species isolated (83.3%). Exposure to hens showed a clear trend to be significantly associated with the disease (OR = 4.33; IC95% 0.97-19.41, p = 0.055), with no significant differences for the rest of the risk factors studied.

CONCLUSION

M. avium is still the predominant bacteria causing NTM lymphadenitis in children of our region. Contact with hens has been the only risk factor for NTM lymphadenitis detected in the present study. What is Known: • M. avium is the predominant bacteria causing NTM lymphadenitis in children of our region. • There is no consensus on which environmental factors are associated with NTM lymphadenitis in children. What is New: • The only risk factor for NTM lymphadenitis found in the present study was regular contact with hens. Contact with other farm animals was not associated to NTM lymphadenitis.