Objective To explore the correlation between the amount of bacteria in alveolar lavage fluid and Th1/Th2 cell immune response in children with refractory Mycoplasma pneumoniae pneumonia.

Methods 96 children with refractory Mycoplasma pneumoniae pneumonia diagnosed and treated in our hospital were randomly selected as the research objects. They were grouped according to the DNA content of Mycoplasma pneumoniae in alveolar lavage fluid, that was, more than 10⁶/mL was the high bacterial volume group (n=35), 10³~10⁶/mL was the medium bacterial volume group (n=30), and less than 10³/mL was the low bacterial volume group (n =31). The levels of inflammatory factors in alveolar lavage fluid of the three groups were detected. The levels of inflammatory factors, lung imaging and laboratory examination results, clinical manifestations, and basic conditions of the three groups were compared, and the correlation between Mycoplasma pneumoniae DNA content in alveolar lavage fluid and inflammatory factors was analyzed.

Results The proportion of children with body temperature higher than 39 ℃, heat course higher than 10 days, total fever time, heat course after antibiotics, hospitalization time, lactate dehydrogenase, platelet count, neutrophil count, lymphocyte count. Above, there was a significant difference in the comparison between the high bacterial count group, the medium bacterial count group, and the low bacterial count group (P<0.05). There was no significant difference in white blood cell counts among the three groups (P>0.05); there were significant differences in the incidence of bilateral or large pleural effusion, atelectasis, or large-scale lung consolidation, and interleukin-4 (IL-4) levels (P<0.05). There were no significant differences in the incidence of bilateral lung lesions , left lung lesions, right lung lesions, and the levels of tumor necrosis factor-α (TNF-α), interferon-γ (INF-γ), and IL-8 among the three groups (P>0.05); IL-4 in the lavage fluid was positively correlated with the DNA level of Mycoplasma pneumoniae (P<0.05), and there was no correlation between TNF-α, INF-γ, IL-8 and the DNA level of Mycoplasma pneumoniae in the alveolar lavage fluid (P>0.05).

Conclusions The amount of bacteria in the alveolar lavage fluid of refractory Mycoplasma pneumoniae pneumonia in children is correlated with Th1/Th2 cellular immune response. The higher the amount of Mycoplasma pneumoniae DNA, the more severe the internal and external lung damage and inflammation, and the imbalance of Th1/Th2 immune response.