Objective To explore the clinical curative effect of azithromycin combined with high-dose vitamin C (VC) in children with Mycoplasma pneumoniae pneumonia (MPP)and its influences on peripheral blood T lymphocyte subsets, serum interleukin (IL)-17, high-sensitivity C-reactive protein (hs-CRP), E2-associated factor 2 (Nrf2) in peripheral blood mononuclear cells and P1 proteins in throat swab.

Methods A total of 240 children with MPP confirmed in the hospital were enrolled as observation objects between June 2020 and June 2023. They were randomly divided into high-dose VC group, low-dose VC group and control group, with 80 cases in each group. The control group was treated with azithromycin, low-dose VC group was treated with azithromycin plus low-dose VC, and high-dose VC group was treated with azithromycin plus high-dose VC, the three groups all treated for 2 weeks. The clinical curative effect and duration of clinical symptoms in the three groups were recorded. Before and after treatment, fasting venous blood and throat swabs were collected in the three groups. T lymphocyte subsets (CD3⁺, CD4⁺, CD8⁺, CD4⁺/CD8⁺) in peripheral blood were detected by flow cytometry. The levels of serum IL-17, hs-CRP and VC were detected by enzyme-linked immunosorbent assay (ELISA). The mRNA levels of Nrf2 protein in peripheral blood mononuclear cells and P1 protein in throat swabs were detected by real-time fluorescence quantitative polymerase chain reaction (qRT-PCR). The adverse reactions during treatment in the three groups were recorded and compared.

Results After treatment, time of fever, cough, expectoration and lung moist rale, and length of hospital stay were shorten in high-dose VC group and low-dose VC group when compared with those in the control group (P < 0.05), and were shorten in the high-dose VC group when compared with those in the low-dose VC group (P < 0.05). After treatment, levels of peripheral blood T lymphocyte subsets (CD3⁺, CD4⁺, CD4⁺/CD8⁺) were increased when compared with those before treatment in the three groups (P < 0.05). The levels of CD3⁺, CD4⁺ and CD4⁺/CD8⁺ in the high-dose VC group were higher than those in the low-dose VC group and control group (P < 0.05), and CD4⁺ level in the low-dose VC group was higher than that in the control group (P < 0.05). After treatment, levels of serum IL-17 and hs-CRP were decreased as compared with those before treatment in the three groups (P < 0.05). The levels of serum IL-17 and hs-CRP in the high-dose VC group were lower than those in the low-dose VC and control group, but there was no difference between low-dose VC group and control group (P>0.05). After treatment, levels of serum VC were increased as compared with that before treatment in high-dose VC group and low-dose VC group, and it was higher in the high-dose VC group than low-dose VC group (P < 0.05). There were no differences in IL-17 and hs-CRP between low-dose VC group and control group (P>0.05). After treatment, mRNA levels of Nrf2 protein in peripheral blood mononuclear cells and P1 protein in throat swabs were decreased compared with those before treatment in the three groups (P < 0.05). The expression level of Nrf2 mRNA in the high-dose VC group was higher than that in the low-dose VC group and control group (P < 0.05), but there was no significant difference in mRNA expression of PI protein among the three groups (P>0.05). There were no obvious adverse reactions in any group during treatment.

Conclusion Azithromycin combined with high-dose VC can effectively improve clinical symptoms, enhance immunity, reduce IL-17 and hs-CRP levels, maintain Nrf2 mRNA level and improve clinical curative effect in MPP children, and has higher safety.