[Evaluation of Screening Performance and Detection Time of Carbapenemase-Producing Enterobacterales Using RAISUS S4 in a Antimicrobial Sensitivity Test].

Rapid detection of carbapenemase-producing Enterobacterales (CPE) is important in infection control, since it transmits plasmids carrying resistance genes. Here, we evaluated the rapid detection of CPE using the fully automated antimicrobial susceptability testing system "RAISUS S4". Sixty-two CPE strains including carbapenem-resistant Enterobacterales and 100 carbapenemase-non-producing Enterobacterales strains were used. RAISUS S4 was performed using both 18 hr and rapid methods. The sensitivity of CPE detection and decision time were evaluated using Meropenem results. The results showed that the sensitivity for CPE detection was 100% for both methods, with specificity of 97% for the 18 hr method and 95% for the rapid method. The mean CPE detection time for the 18 hr method was 7.2 hrs and 8.8 hrs for the rapid method. The mean MIC determination time of the 18 hr method for all 162 strains was 17.2 hrs and 8.8 hrs for the rapid method. In addition, we analyzed the absorbance values of the 18 hr method. Checking the growth curve at a drug concentration of 0.125 µg/ml and determining it to be positive when its absorbance reached 0.8 Abs, CPE could be detected in an average of 5.8 hrs with in sensitivity of 100% and specificity of 92%. The 18 hr method of RAISUS S4 allowed rapid detection of CPE, and the rapid method allowed earlier MIC determination, including sensitive isolates. These results suggest that RAISUS S4 can detect CPE rapidly without missing CPE by routine test even in Japan where the frequency of CPE isolation is low.