Changes and Trends of Drug Resistance of Pathogenic Bacteria in Blood Samples of a Tertiary-Level Teaching Hospital from 2016 to 2020

  Objective  To investigate the distribution of pathogenic bacteria in blood samples and changes in their drug resistance in our hospital from 2016 to 2020, and to provide evidence for the diagnosis and treatment of clinical bloodstream infections.

  Methods  Bruker Corporation’s matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used for bacterial identification, VITEK 2 Compact was used for antimicrobial susceptibility test, some of which was done with the Kirby-Bauer method, and the data was statistically analyzed with WHONET 5.6 software.

  Results  A total of 8931 bacterial strains, including 4502 (50.4%) Gram-positive bacteria and 4429 (49.6%) Gram-negative bacteria, were isolated from the blood samples between 2016 and 2020. Among the isolated bacteria of the order Enterobacterales, Escherichia coli (1773, 19.9%) ranked first, followed by Klebsiella pneumoniae (1067, 11.9%). The non-fermenting bacteria identified were predominantly Acinetobacter baumannii (293, 3.3%) and Pseudomonas aeruginosa (238, 2.7%). The top three Staphylococcus species were Staphylococcus epidermidis (970 strains, 10.9%), Staphylococcus hominis (713, 8.0%) and Staphylococcus aureus (541, 6.1%). Escherichia coli showed high in vitro susceptibility to cefoperazone/sulbactam, amikacin, polymyxin B, tigecycline, and carbapenems, and the sensitivity rate was consistently over 90%. The resistance rate to imipenem showed a trend of slow growth, and the resistance rate of meropenem was 2.2% to 3.4%. Klebsiella pneumoniae showed higher in vitro resistance rate to common antibiotics than that of Escherichia coli, with only the sensitivity rates to tigecycline and polymyxin B being higher than 90%, and the resistance rate to imipenem and meropenem increasing year by year. The resistance rate of Pseudomonas aeruginosa to imipenem decreased since 2017 (from 25.6% to18.6%), and the resistance rate of Acinetobacter baumannii to imipenem and meropenem were 73.7%-91.3% and 73.0%-91.3%. Staphylococcus resistant to vancomycin or linezolid was not found. Enterococci showed rather low resistance to vancomycin and linezolid.

  Conclusion   The distribution of common species of pathogenic bacteria in clinical blood samples in our hospital did not show significant changes, but the problem of multi-drug resistant bacteria is becoming increasingly more serious, especially so for carbapenem-resistant Klebsiella pneumoniae.