Pulmonary and Disseminated Complex Cases Confirmed by Tissue-Direct Polymerase Chain Reaction-Based Nucleic Acid Lateral Flow Immunoassay of Formalin-Fixed Paraffin-Embedded Tissues.

BACKGROUND

Detection of complex (MAC) in tissue is essential for the diagnosis of MAC infections when the is not isolated from sputum. However, detection of MAC in paraffin-embedded sections has not been established.

METHODS

We encountered two patients with suspected MAC infections after surgery: patient 1 had a pulmonary nodule that was initially suspected to be lung cancer and was excised under video-assisted thoracoscopic surgery (VATS). Patient 2, who was under treatment with steroids and anti-IL-6 inhibitors for rheumatoid arthritis, was suspected to have disseminated ileocecal cancer with metastasis to the lung and skin. In both cases, we postoperatively detected MAC genes in paraffin-embedded tissue sections using the novel mycobacterial nucleic acid identification test, ie tissue-direct polymerase chain reaction (tdPCR)-based nucleic acid lateral flow immunoassay (NALFIA). Both patients showed granulomatous lesions with hematoxylin-eosin staining, and mycobacteria by Ziehl-Neelsen staining in tissue sections from the lung and skin, respectively, although MAC were not isolated from the sections. MAC genes were finally detected by tdPCR-NALFIA in both cases.

CONCLUSION

Although Ziehl-Neelsen staining and culture tests are the gold standard in identifying causative mycobacteria, the rapid results of tdPCR-NALFIA performed simultaneously with sputum and/or tissue culture may make it an important auxiliary diagnostic tool for identifying mycobacterial infection, leading to improvement in the management of MAC patients.