目的 分析不同时期难治性支原体肺炎（refractory Mycoplasma pneumoniae pneumonia, RMPP）患儿支气管肺泡灌洗液（bronchoalveolar lavage fluid, BALF）菌群分布特点及其与免疫功能的关系。 方法 选取RMPP患儿108例，比较急性期（61例）、恢复期（47例）BALF菌群相对丰度、丰富度、均匀度及免疫功能；分析丰富度、均匀度与免疫功能的相关性。 结果 急性期丙酸杆菌属相对丰度及BALF菌群Simpson指数、Shannon指数、Chao1指数、Observed species指数均低于恢复期（P<0.05），链球菌属、普雷沃菌属相对丰度，补体C3、补体C4、免疫球蛋白A、免疫球蛋白G、免疫球蛋白M水平均高于恢复期（P<0.05）；Simpson指数、Shannon指数、Chao1指数、Observed species指数与补体C3、补体C4、免疫球蛋白A、免疫球蛋白M、免疫球蛋白G水平均呈负相关（P<0.05）。 结论 急性期RMPP患儿BALF中丙酸杆菌属相对丰度及菌群丰富度、均匀度均低于恢复期，链球菌属、普雷沃菌属相对丰度均高于恢复期，菌群丰富度及均匀度与免疫功能密切相关。

Objective To study the characteristics of bronchoalveolar lavage fluid (BALF) microbial distribution at different stages of refractory Mycoplasma pneumoniae pneumonia (RMPP) in children and its relationship with immune function. Methods A total of 108 children with RMPP were enrolled. The relative abundance, richness, and diversity of BALF microbiota, as well as immune function, were compared between the acute phase (n=61) and recovery phase (n=47). The correlations between the richness and diversity of BALF microbiota and immune function were analyzed. Results The relative abundance of Propionibacterium, as well as the Simpson index, Shannon index, Chao1 index, and Observed species index of BALF microbiota in the acute phase were significantly lower than those in the recovery phase (P<0.05). The relative abundances of Streptococcus and Prevotella, as well as the levels of complement C3, complement C4, immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM), were significantly higher in the acute phase than in the recovery phase (P<0.05). Simpson, Shannon, Chao1, and Observed species indices were negatively correlated with levels of complement C3, complement C4, IgA, IgM, and IgG (P<0.05). Conclusions In children with RMPP, the relative abundance of Propionibacterium and the richness and diversity of BALF microbiota in the acute phase are lower than those in the recovery phase, while the relative abundances of Streptococcus and Prevotella are higher in the acute phase. Microbial richness and diversity are closely related to immune function.