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 VITEK2 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 VITEK2 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 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 VITEK2 system. E. cloacae isolates accounted for the majority of the discrepancies.