Evaluation of Aptamer Fluorescence Microscopy in the Diagnosis of Pulmonary Tuberculosis.

Sputum smear microscopy for tuberculosis diagnosis has stood the test of time. However, due to its low sensitivity, the positive detection rate for tuberculosis in clinical specimens is not high. To improve the sensitivity of microscopic observation in Mycobacterium tuberculosis (MTB) detection, we developed the MTB-specific aptamer MA1. To further improve the binding reactivity of MA1 with MTB, we constructed a new derivative aptamer with a pocket-stem-loop-structure, MA1-39, and identified it to have high binding reactivity with the MTB reference strain. We developed an aptamer fluorescence microscopy test for MTB based on MA1-39 and evaluated its feasibility for diagnosing pulmonary tuberculosis. Among 56 tested strains, MA1-39 was proven to effectively discriminate MTB from the control strains, including 12 non-tuberculosis mycobacterial (NTM) reference strains, 6 NTM isolates, and 7 other bacteria. Next, this approach was applied to 169 clinical sputum samples from suspected tuberculosis patients and non-tuberculosis controls. Molecular tests together with both clinical and bacteriological identification were used as a protocol to evaluate the efficacy of aptamer detection. Compared with the traditional acid-fast staining light microscope, the aptamer fluorescence microscope showed a higher detection rate for MTB in clinical specimens (48.8% versus 32.6%), and the specificities of the two techniques had almost no significant difference (90.4% versus 94%). In addition, aptamer fluorescence microscopy showed the same positive predictive value (PPV) as staining (84% versus 84.9%), but a higher negative predictive value (NPV; 63% versus 57.3%). In conclusion, the newly established aptamer fluorescence microscopy approach is likely to be a feasible method for microbiological diagnosis of tuberculosis.