Abstract

Carbapenemase-producing Enterobacterales (CPE) are not always resistant to carbapenem antimicrobial susceptibility testing (AST) and can be difficult to detect. With the newly created VITEK2 AST-XN17 card, the types of antibiotics measured in AST can be increased. In this study, we evaluated the detectability of CPE using the results of AST with multiple antimicrobial agents with additional measurements of the AST-XN17 card. In addition, we evaluated the CPE detectability of comments on CPE using the VITEK2 Advance Expert System (AES). In total, 169 Enterobacterales samples, including 76 non-CPE and 93 CPE, collected from multiple medical institutions in the Kinki region of Japan, were used in this investigation. AST with VITEK2 was performed by adding the AST-XN17 card in addition to the AST-N268 or AST-N404 card. Measurement results were identified using cutoff values, primarily Clinical and Laboratory Standards Institute breakpoints, and the CPE detection capability of each antibiotic was evaluated in several terms, including sensitivity and specificity. The drugs highly sensitive to CPE detection were faropenem (FRPM) > 2 µg/mL at 100% and meropenem > 0.25 µg/mL at 98.9%; the highest specificity to CPE detection was for avibactam/ceftazidime (AVI/CAZ) > 8 µg/mL at 100%. The sensitivity and specificity of each card in the AES output were 86.2% and 94.7% for AST-N404 and AST-XN17 and 91.5% and 90.8% for AST-N268 and AST-XN17, respectively. AST using the VITEK2 AST-XN17 card is a useful test method of screening for CPE.

Highlights

  • Carbapenems are a commonly used primary therapeutic option for serious infections caused by gram-negative bacilli

  • Among carbapenemase-producing Enterobacterales (CPE), there are so-called stealth-type strains in which the minimum inhibitory concentrations (MIC) of carbapenem are not determined to be resistant beyond the breakpoint upon antimicrobial susceptibility testing (AST) [7]

  • The present study aimed to evaluate the detectability of CPE based on the results of AST with multiple antimicrobial agents in conjunction with additional measurements of the ASTXN17 card

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Summary

Introduction

Carbapenems are a commonly used primary therapeutic option for serious infections caused by gram-negative bacilli. They are often considered agents of last resort. Among CPE, there are so-called stealth-type strains in which the minimum inhibitory concentrations (MIC) of carbapenem are not determined to be resistant beyond the breakpoint upon antimicrobial susceptibility testing (AST) [7]. A newly developed VITEK2 AST-XN17 card (bioMérieux, Marcy-l'Étoile, France) was used. The present study aimed to evaluate the detectability of CPE based on the results of AST with multiple antimicrobial agents in conjunction with additional measurements of the ASTXN17 card

Materials and methods
Results
Discussion
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