Objective:To analyze the characteristics of respiratory pathogen spectrum in adult patients with acute exacerbation of bronchiectasis and its correlation with the severity of disease.Methods:A total of 108 patients with stable bronchiectasis from January 2014 to May 2018 in the Third People′s Hospital of Haikou City were enrolled. Sputum bacteria were cultured and common respiratory viruses in sputum and nasal swabs were detected by fluorescence quantitative polymerase chain reaction(PCR). All bronchiectasis patients were followed up for 1 year. Sputum bacteria culture and PCR virus detection were performed again in patients with acute exacerbation, and the differences of respiratory pathogen spectrum in patients with different severity of acute exacerbation were compared.Results:During the follow-up period, there were 53 cases of acute exacerbation events and a total of 91 case-times (up to 5 times per patient). The positive rates of sputum virus and nasal swab virus in patients with acute exacerbation were significantly higher than those in patients with stable period [39.6% (36/91) vs. 15.1% (8/53) , 45.1% (41/91) vs. 9.4% (5/53) ], and there were significant differences ( χ2=8.460, 13.621, P<0.05). However, the total positive rate of sputum bacterial culture in acute exacerbation and stable period had no significant difference ( P>0.05). The positive rate of Pseudomonas aeruginosa [0, 34.6% (9/26) ,52.4% (22/42) ] and rhinovirus [8.7% (2/23) ,3.8% (1/26) ,23.8% (10/42) ] in sputum among mild patients (16 cases, 23 case-times), moderate patients (16 cases, 26 case-times) and severe patients (21 cases, 42 case-times) in acute exacerbation stage were significant differences ( P<0.05). The levels of C-reactive protein (CRP) and interleukin (IL)-8 in patients in mixed infection of bacteria and viruses group in acute exacerbation stage were significantly higher than those in negative group, bacteria group and viruses group [CRP: (45.6 ± 23.0) mg/L vs. (11.2 ± 2.7) , (32.3 ± 10.2) , (21.3 ± 8.0) mg/L; IL-8: (9.0 ± 2.5) ng/L vs. (1.5 ± 0.9) , (1.8 ± 1.1) , (2.0 ± 1.3) ng/L], and there were significant differences ( F=23.012, 9.926, P<0.05). The hospitalization rate of patients in mixed infection of bacteria and viruses group was significantly higher than that in negative group, bacteria group and viruses group [29.6% (8/27) vs. 0, 16.7% (4/24) , 1/18] , and there were significant differences ( χ2=7.691, P<0.05). Conclusions:The positive rate of respiratory viruses in acute exacerbation of bronchiectasis in adults is significantly higher than that in stable stage. Pseudomonas aeruginosa and rhinovirus are the main infections in moderate and severe patients, Haemophilus parainfluenzae and influenza A virus are the main infections in mild patients, and the patients with mixed infection of bacteria and viruses have severe systemic inflammatory reaction and high hospitalization rate.