2021 Volume 70 Issue 2 Pages 237-242
Antimicrobial susceptibility tests of positive blood cultures are required for the timely treatment of patients with appropriate antibacterial drugs. Antimicrobial susceptibility tests using a single colony typically take three days to complete. Thus, we compared the antimicrobial susceptibility test results of a rapid method using microcolonies obtained after 2 to 4 hours of subculture with those of the standard method using a single colony. The target species were Escherichia coli and Klebsiella pneumoniae. The concordance rate was calculated for E. coli (225 samples) and K. pneumoniae (79 samples). The MIC 1 agreements of the rapid method and standard method were 97.3–100.0% for E. coli and 96.2–100.0% for K. pneumoniae, the category complete agreements were 81.8–100.0% for E. coli and 78.5–100.0% for K. pneumoniae, the major error rates were 0–0.4% for E. coli and 0–2.5% for K. pneumoniae, and the very major error rates were 0–0.4% for E. coli and 0–1.3% for K. pneumoniae. Thus, these findings suggest that the results of the antimicrobial susceptibility test performed using microcolonies formed in the early stage of subculture are reliable and can be reported quickly.
