Abstract: [Abstract] Background and study objective: The aetiology of acute exacerbations of chronic obstructive pulmonary disease (COPD) is heterogeneous and still under discussion. Serological studies have suggested that Mycoplasma pneumoniae(Mp) may play a role in acute exacerbations of COPD（AECOPD）. We want to explore the correlation between the Mp infection and AECOPD hospitalizations ratio. Methods : The presence of these Mp in Serological samples was investigated in patients with AECOPD and other kinds of respiratory infection patients using passive agglutination. The present study was retrospective study and a total of 418 serological samples from 298 AECOPD inpatients (study group) and 120 other kinds of respiratory infection patients (control group) were included. According to the lung functions of the AECOPD patients the study group were divided into four subgroup. By the results of the Mp investigation the study group was divided into Mp positive group and Mp negative group. Results: Mp seroprevalences of the study group (22.82%) were higher than in the control group (12.5%) with statistical significance (P<0.01). The seroprevalences of the sub-study group were 19.28%, 25.81％,23.63％,23.52％ respectively but without statistical significance(P>0.05).We also found that the seroprevalences was different as the time go on and also there was no correlation between AECOPD hospitalization and Mp Seroprevalences（r=0.305，P > 0.05）. There were no significant differences between these two groups divided by the Mp value in a broad spectrum of patient- and exacerbation-related clinical variables. Conclusion : We have shown that microorganisms causing acute exacerbations of COPD are not only typical bacteria but also atypical pathogens with unpredictable high rates. The seroprevalences was related with outbreak time not the severity of the disease. Pay more attention to the Mp maybe get better prognosis for most patients.

Key words: Mycoplasma pneumoniae, chronic obstructive pulmonary disease, acute exacerbation