A comparative study of the VITEK® REVEAL™ versus the VITEK2 system in susceptibility testing of NDM-producing enterobacterales and Acinetobacter baumannii directly from positive blood cultures.

Purpose: To compare the antimicrobial susceptibility testing (AST) results obtained by the VITEK^® REVEAL™ to the VITEK^®2 system in the testing of (1) NDM-producing Enterobacterales (NDME) isolates and (2) NDM-producing Acinetobacter baumannii (NDMAb) isolates.

Methods: The study included 197 NDME isolates and 54 NDMAb isolates that were collected in Israel between 2018 and 2019. For the REVEAL™ testing, isolates were suspended in saline, inoculated into a blood culture FA Plus^® bottles and incubated using the VIRTUO^® system until flagged positive. A sample was then transferred into the REVEAL™ GN01 panel and the results were compared with the VITEK^®2 N308 card as reference. Isolates with major or very-major discrepancies (MD and VMD, respectively) between the systems were tested by the Sensititre™ GNX3F Plates.

Results: For NDME, high rates of VMD were observed in amikacin (3.8%), imipenem (5.7%) and meropenem (8%) while high rates of MD were observed in trimethoprim-sulfamethoxazole (56.3%), amikacin (15.2%), and aztreonam (29%). Enterobacter cloacae isolates accounted for the majority of errors in carbapenem antimicrobials and aztreonam. Compared to the Sensititre results, REVEAL™ testing displayed lower agreement for ciprofloxacin (0/6) and aztreonam (5%) and higher agreement for trimethoprim-sulfamethoxazole (45%) and meropenem (87%). For NDMAb, there were 35% and 76% minor discrepancies in imipenem and meropenem, respectively. The REVEAL™ results matched the Etest^TM method.

Conclusion: Use of the REVEAL™ system can provide rapid AST of positive blood culture. However, testing of NDME isolates revealed several discrepancies compared with the VITEK^TM2 system. E. cloacae isolates accounted for the majority of the discrepancies.