Abstract: Objective: To compare the effects of eco-friendly dewaxing solution and two different decolorizing solutions on acid-fast staining of granuloma paraffin sections. Methods: Three methods were applied to process 41 skin tissue specimens previously pathologically diagnosed with leprosy: xylene as a clearing and dewaxing solution, an eco- friendly dewaxing solution as a clearing and dewaxing solution, and 20% sulfuric acid aqueous solution or 1% hydrochloric acid alcohol solution as a decolorizing solution after specimens dewaxed by eco-friendly dewaxing solution. The Zienkl - Neelsen acid - fast staining method was used to detect the density and morphology of Mycobacterium leprae in each group. Results: The positivity rate of Mycobacterium leprae in the eco-friendly dewaxing solution group was 63.4%, higher than 58.5% in the xylene group. The positivity rate of Mycobacterium leprae in the 1% hydrochloric acid alcohol group was the same as that in the 20% sulfuric acid aqueous solution group, which was 63.4%, with a significant difference (P＜0.05). After acid - fast staining, Mycobacterium leprae showed bright red under the microscope. The background after decolorization with 1% hydrochloric acid-alcohol was purplish red, and the background after decolorization with 20% sulfuric acid aqueous solution was gray - blue, in which color contrast between the background and Mycobacterium leprae was more obvious. After all specimens were decided by two doctors independently, the result showed that the difference specimens of acid - fast bacilli morphological indexes between the two methods were 26 and 13 respectively, with a significant difference (χ2 =8.264, P＜0.05). Conclusion: Compared with xylene, eco-dewaxing solution is beneficial for improving the detection rate of Mycobacterium leprae acid-fast staining. The color contrast between the background and Mycobacterium leprae was more obvious using 20% sulfuric acid aqueous solution as a decolorizing solution, which is help to identify of Mycobacterium leprae.

Key words: Mycobacterium leprae, acid-fast staining, environmental dewaxing solution, decolorizing fluid