Comparison of the results of sputum culture and bronchoscopic lavage fluid culture:an analysis report of large sample size data from the Clinical Microbiology Laboratory

Background: Sputum specimens were the most common for Clinical Microbiology Laboratory in China. For the results of sputum culture, it was difficult for clinicians to evaluate the significance, and even more difficult for laboratory physicians. At present, most Clinical Microbiology Laboratories in China executed quality assessment of sputum specimens. But how to evaluate the results of sputum culture was still very confusing. To solve this problem, we conducted a series of retrospective studies.Methods Based on the culture results of bronchoscopic lavage fluid (BALF), the differences of sputum culture results before (2013-2015) and after (2016-2018) quality control of sputum samples in our hospital were compared.Results Pseudomonas aeruginosa , Acinetobacter baumannii , Klebsiella pneumoniae and Staphylococcus aureus were the four most common pathogens in sputum and BALF culture, both in 2013-2015 years and 2016-2018 years. Antimicrobial susceptibility test from 2013-2015 and 2016-2018 both showed for P. aeruginosa and K. pneumoniae , the susceptibility rates of BALF isolates to all commonly used antibiotics were higher than those from sputum. For A. baumannii and S. aureus , the sensitivity rates of BALF isolates to most antibiotics were higher than those from sputum. After quality control of sputum samples, there was still a difference between the results of sputum culture and those of BALF.Conclusions Even though the quality control of sputum specimens had been carried out, the results of culture and antimicrobial resistance of pathogens from qualified sputum samples were still different from those of BALF.