Pathogenic Characteristics of Sputum and Bronchoalveolar Lavage Fluid Samples from Patients with Lower Respiratory Tract Infection

Abstract

Background Lower respiratory tract infections(LRIs)were a very common disease, no matter in community acquired infection or hospital acquired infection. Sputum and bronchoalveolar lavage fluid (BALF) were the most important specimens of LRIs. The choice of antibiotics for the treatment of LRIs usually depended on the results of antimicrobial sensitivity of bacteria isolated from sputum and BALF. However, it was rarely reported to compare the pathogens isolated from sputum and BALF and the difference of antimicrobial sensitivity.Methods A retrospective study was conducted to analyze the differences between sputum and BALF samples in pathogen isolation and antimicrobial sensitivity in our hospital.Results In our hospital during 2013–2015 year, the quality evaluation of sputum samples was not conducted before sputum culture, but in 2016–2018 year, the quality evaluation of sputum samples was conducted firstly and only qualified sputum samples were cultured. The results of pathogen culture showed that Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus and Haemophilus influenzae were the top five pathogens isolated from sputum and BALF. Antimicrobial susceptibility test showed for these five pathogens the susceptibility rates of BALF isolates to most antibiotics were higher than those isolated from sputum. The sensitivity of A. baumannii to common antibiotics was less than 50%. In particular, the detection rate of carbapenem resistant A. baumannii (CR-ABA) in sputum and BALF was higher than 80%. The sensitivity of P. aeruginosa to antibiotics other than ticarcillin/clavulanic acid and minocycline were higher than 50%. The detection rate of carbapenem resistant Klebsiella pneumoniae (CR-KPN) was 10% − 20% in 2013–2015 and 30% − 50% in 2016–2018. The detection rate of MRSA in sputum was higher than 80%, while that in BALF was 65% − 70%. The separation rate of beta-lactamase-negative ampicillin-resistant H. influenzae (BLNAR) was between 0–6%.Conclusions The sensitivity of strains isolated from BALF to commonly used antibiotics was generally higher than that from sputum. MRSA, CR-KPN and A. baumannii were the focus of infection control for LRIs.