Incidence of mycobacteria in pulmonary granulomatous lesions

Abstract

Mycobacteria infections are caused by species of the Mycobacterium tuberculosis complex (MTB) and other species called Non-Tuberculosis Mycobacteria (NTM). Identification of mycobacteria species is very important to define treatment and it can be achieved by direct culture. However, the lack of clear protocols regarding the use of culture or molecular tests on specimens diagnosed with granulomatous lesions causes delays in the diagnosis of the etiological agents and, consequently, the definition of the right treatment. This work aimed to characterize the incidence of mycobacteria species in pulmonary granulomatous lesions and the contribution of Polymerase Chain Reaction (PCR) in Formalin-Fixed Paraffin-Embedded Tissue (FFPE), direct culture, and Ziehl-Neelsen histological stain to the diagnosis. The authors performed an observational, centralized, and retrospective study in a cohort of 336 cases with pulmonary granulomatous lesions. Mycobacteria were detected by ZNS in 54/323 (16.72 %) and by direct culture in 40/198 (20.20 %). MTB DNA was detected by PCR in 10/57 (17.54 %). Mycobacterial culture results revealed MTB in 26/40 (65.00 %), whereas NTM was detected in 13/40 (32.50 %). NTM was represented by M. avium (n = 4), M. intracellulare (n = 3), M. kansasii (n = 3), M. colombiense (n = 1), M. paraffinicum (n = 1), and M. abscessus subsp. massiliense (n = 1). In conclusion, this study demonstrated that mycobacteria are detected in 16.72 % to 20.20 % of pulmonary granulomatous lesions. Moreover, MTB and NTM were detected in these lesions. The use of different methods for mycobacteria detection, in addition to culture, is complementary and contributes to fastening and increasing the detection of mycobacteria in these lesions.

Keywords: FFPE specimens; Lung granulomatous lesions; Mycobacteria detection.