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

Background Sputum is the most common specimen type of lower respiratory tract 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. Bronchoscope alveolus lavage fluid(BALF)is a good specimen, which can accurately reflect the situation of lower respiratory tract infections (LRIs). 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, 40–70 years old was the highest age of distribution, but for Escherichia coli and Streptococcus 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.