Abstract: Objective The objective of this study was to explore the drug resistance of pathogenic microorganisms in the alveolar lavage lavage fluid of patients with mycoplasma pneumoniae pneumonia, and to clarify the association between chitinase protein 40 (YKL-40) and galectin-3 (Gal-3) and the severity and prognosis of the disease. It provides a scientific basis for rational selection of antibacterial drugs, early assessment of patient's condition risk and development of individualized prognostic intervention strategies. Method A total of 162 patients with mycoplasma pneumoniae pneumonia admitted to Dujiangyan People's Hospital from January 2021 to January 2024 were selected as the observation group, and 162 healthy individuals who underwent physical examinations during the same period were selected as the control group. The observation group was divided into a severe group of 68 cases and a mild group of 94 cases aBased on symptoms, signs, and chest X-ray results. According to the symptoms, signs and chest X-ray results of the patients after treatment, they were divided into a good prognosis group of 111 cases and a poor prognosis group of 51 cases. The drug resistance of pathogenic microorganisms in alveolar lavage fluid of each group was compared respectively. To analyze the correlation between the levels of YKL-40 and Gal-3 in the peripheral blood of patients and the severity of the disease, multivariate logistic regression was used to analyze the influencing factors of poor prognosis of patients, and the receiver operating characteristic (ROC) curves were constructed to evaluate the predictive value of the levels of YKL-40 and Gal-3 in the peripheral blood of patients for the poor prognosis of patients with mycoplasma pneumoniae pneumonia. The patients in the observation group were further divided into a training set (113 cases) and a validation set (49 cases) to predict the area under the curve for the prognosis of Mycoplasma pneumoniae pneumonia patients. Result A total of 180 pathogenic bacteria were cultured from the alveolar lavage fluid of 162 patients with mycoplasma pneumoniae pneumonia, including 135 from the severe group, and 45 in the mild group. A total of 140 strains were detected in the poor prognosis group and 40 strains were detected in the good prognosis group. The resistance rate to levofloxacin was the highest among the four groups of pathogenic bacteria. YKL-40 and Gal-3 levels in peripheral blood were positively correlated with disease severity in patients with mycoplasma pneumonia (r=0.584, 0.722, P<0.05). The levels of YKL-40 and Gal-3 in the poor prognosis group were higher than those in the good prognosis group (P<0.05). The levels of YKL-40 and Gal-3 in peripheral blood were independent risk factors for poor prognosis in patients with mycoplasma pneumonia (P<0.05). The ROC area under the curve of the combined prediction of peripheral blood YKL-40 and Gal-3 levels for poor prognosis of patients with Mycoplasma pneumonia was 0.837 (95%CI: 0.771~0.891, P<0.001), which was higher than that of single detection. The AUC (95%CI) of the training set and the validation set were 0.67 (0.56~0.77) and 0.72 (0.55~0.88) for the prediction of the prognosis of mycoplasma pneumonia patients with the training set and the validation set. The DCA curve shows that the probability threshold of the nomogram model at 20%~50% provided a higher net benefit. Conclusion Patients with Mycoplasma pneumoniae pneumonia exhibit the highest resistance rate to levofloxacin. Levated peripheral blood levels of YKL-40 and Gal-3 are positively correlated with disease severity of mycoplasma pneumoniae pneumonia. High levels of YKL-40 and Gal-3 are independent risk factors for poor prognosis in patients with mycoplasma pneumoniae pneumonia, and the combined detection has a high value in evaluating the poor prognosis of patients.

Key words: pneumoniae/pneumonia, Chitinase protein 40, Blood galectin-3, Degree of severity, Poor prognosis