Investigação da presença do bacilo Mycobacterium tuberculosis em amostras sugestivas de tuberculose oral

Abstract

Tuberculosis (TB) is a significant global public health issue. In 2021, according to the World Health Organization (WHO), it was estimated that approximately 10.6 million people developed TB worldwide, and 1.4 million died from the disease. Consequently, it became the leading cause of death due to infection worldwide and one of the top ten overall causes of death. TB primarily affects the lungs and is referred to as Pulmonary TB (PTB). However, it can be diagnosed in various organs of the body as Extrapulmonary TB (EPTB), with lymph nodes being the most common site of involvement. Moreover, pleural, neurological, synovial, pericardial, abdominal, genitourinary, and oral involvement have been described, demonstrating the potential for Mycobacterium tuberculosis (MTB) dissemination. The detection of Acid-Fast Bacilli (AFB) typically involves the observation of microscopic tissue characteristics, the presence of granulomas with caseous necrosis, epithelioid histiocytes, and Langhans giant cells, along with AFB staining using the Ziehl-Neelsen (ZN) technique. Furthermore, immunohistochemistry (IHC), nucleic acid amplification tests by Nested Polymerase Chain Reaction (nested-PCR), and the automated detection system GeneXpert® MTB/RIF are methods employed for diagnosing the infection. Therefore, the aim of this study was to investigate the presence of Mycobacterium tuberculosis in paraffin-embedded oral samples containing granulomas with caseous necrosis. Inclusion criteria were based on the selection of biopsies displaying granulomas with caseous necrosis, suggesting a diagnosis of TB. Biopsies without these features upon review of records and histological findings, as well as intraosseous biopsies, were excluded. M. tuberculosis was sought using ZN staining, IHC, nested-PCR, and GeneXpert® MTB/RIF assays. Nine samples with granulomas and caseous necrosis were selected. The majority of individuals were male (2.5:1 ratio), with an average age of 50 years (±23.08; range 19-89), and the tongue was the most affected anatomical site (n=4). AFB was not identified by the ZN technique in any of the samples, and IHC staining exhibited a coarse granular pattern, suggestive of M. tuberculosis, in three of them. Nested-PCR and GeneXpert® MTB/RIF assays yielded positive results in two and three of the samples, respectively. In conclusion, molecular tests and IHC can be valuable auxiliary methods for suspected cases of tuberculosis.