Characteristics of bacterial etiology in lower respiratory tract infection: a surveillance report from a Chinese large teaching hospital from 2015 to 2019

Background: Lower respiratory tract infection (LRI) is a very common clinical disease. The etiological diagnosis of LRI often depends on the result of sputum culture. Sputum is the most common specimen type of LRI in China, but its cultivation result is easily confused by the bacteria colonized in the oral cavity and pharynx. It is very difficult to evaluate the clinical significance of sputum culture results both for clinicians and microbiologists. Fortunately, bronchoscope alveolus lavage fluid(BALF)is a good specimen, whose culture results can accurately reflect the situation of LRI. By analyzing the culture results and antimicrobial agents sensitivity data of BALF accumulated in this area, we can provide reference for clinicians to experience in the treatment of lower respiratory tract infection.Methods: The accumulated data of BALF culture and antimicrobial susceptibility test in our hospital from January 2015 to October 2019 were reviewed and analyzed.Results: The positive rate of BALF culture in our hospital was 18.3% (3467/18935) in 2015-2019. The most common pathogens were Klebsiella pneumoniae (18.1%, 627/3467), Pseudomonas aeruginosa (16.9%, 587/3467) and Acinetobacter baumannii (14.0%, 485/3467). For the eight most common pathogens (K. pneumoniae, P. aeruginosa, A. baumannii, Staphylococcus aureus, Haemophilus influenzae, Stenotrophomonas maltophilia, Escherichia coli and S. pneumoniae), 40-70 years old was the highest age of distribution, but for E. coli and S. pneumoniae, 0-5 years old was also the higher age of distribution. The antibiotic resistance rate of K. pneumoniae to imipenem and meropenem was 30.6% and 30.8%, respectively. The sensitivity of P. aeruginosa to antibiotics other than minocycline and ticarcillin clavulanic acid was all more than 60%. However, the resistance rate of A. baumannii to antibiotics other than tegacyclin and minocycline was all more than 80%.Conclusions: 40-70 years old was the high incidence age of lower respiratory tract bacterial infection. K. pneumoniae resistant to carbapenems (CR-K. pneumoniae) and A. baumannii were a great challenge to clinical treatment and bacterial resistance control.