Characteristics of respiratory tract flora and changes of serum MD-2 level and EOS% in patients with acute attack ofbronchial asthma Wang Fei, Qian Meng, Quyang Yi, Xue Xiaojie. Department of Respuratory Medicune, Central Hospital ofEdong Medical Group/Affiliated Hospital of Hubei Institute of Technology,Hubei Province, Huangshi 435000 , ChinaCorresponding author: Oian Meng, E-mail: 924132025@ gg. comFunding program ; The Third Batch of Joint Fund Projects of Hubei Provincial Health Commission ( W12019H470)

Abstract：

Objective To analyze the changes of serum myeloid differentiation protein-2(MD-2), eosinophil percentage(EOS%) and their relationship with the characteristics of respiratory tract flora in patients with acute attack of bronchial asthma(AEBA).Methods From August 2020 to February 2022, 94 patients with AEBA admitted to the Department of Respiratory Medicine of the Central Hospital of Eastern Hubei Medical Group/Affiliated Hospital of Hubei Institute of Technology were selected as the observation group, and 94 patients with physical examination in the same period were selected as the health control group. The distribution characteristics of bacteria were determined by sputum culture. Compare the clinical data of patients with gram-negative and gram-positive bacterial infections, compare the levels of serum MD-2 and EOS% in the two groups and AEBA patients with different degrees of illness, analyze the correlation between serum MD-2 and EOS% and the degree of illness by Spearman method, analyze the risk factors of different types of bacterial infections by logistic regression, and evaluate the value of serum MD-2 and EOS% to identify the types of bacterial infections by using the working characteristic curve(ROC) of subjects. Results Among the AEBA patients, 63 were infected with gram-negative bacteria, 26 with gram-positive bacteria, and 5 with gram-negative bacteria and gram-positive bacteria. The proportion of patients with gram-negative bacterial infection and the levels of serum MD-2, EOS% and procalcitonin(PCT) were higher than those with gram-positive bacterial infection, and the score of control was lower than those with gram-positive bacterial infection [χ²(t)/P=1.996/0.046, 4.329/<0.001, 3.663/<0.001, 16.714/<0.001, 3.371/<0.001]. The serum MD-2 and EOS% in the observation group were higher than those in the healthy control group(t/P=21.161/<0.001, 19.288/<0.001). The more severe the condition of AEBA patients, the higher the level of serum MD-2 and EOS%(F/P=21.601/<0.001, 23.783/<0.001). Serum MD-2 and EOS% were positively correlated with the severity of AEBA patients(r/P=0.842/<0.001, 0.846/<0.001). The increase of serum MD-2 and EOS% was a risk factor for postoperative infection of gram-negative bacteria in AEBA patients [OR(95% CI)=2.973(1.268-5.443), 3.411(1.752-6.097)]. The ROC curve analysis showed that the area under the curve(AUC) of serum MD-2, EOS% and their combination to identify the type of bacterial infection in AEBA patients were 0.778, 0.772 and 0.877, respectively. The combined detection of the two indicators was greater than the identification efficiency of individual indicators(Z/P=2.118/0.034, 2.366/0.018). Conclusion The levels of serum MD-2 and EOS% in AEBA patients increased abnormally, and the more severe the disease was, the more obvious the changes were. At the same time, the type of bacterial infection could be identified.

Bronchial asthma,acute exacerbation;                    Microbiota profile;                    Myeloid differentiation protein-2;                    Eosinophil percentage;                    Respiratory tract infection;