A Rapid and Easy Method of MALDI Biotyper Antibiotic Susceptibility Test Rapid Assay To Provide Early Meropenem Susceptibility Profile in Enterobacterales

Antimicrobial susceptibility testing (AST) that can provide faster results is necessary. The MALDI Biotyper antibiotic susceptibility test rapid assay (MBT-ASTRA) can provide early AST results but still needs to be simplified in order to facilitate its execution by microbiology laboratories. The aim of this study was to evaluate an adaptation of MBT-ASTRA. Isolates of Enterobacterales were tested for meropenem susceptibility by MBT-ASTRA using a solution prepared from meropenem disks and performing a manual spectrum analysis. The relative growth (RG) was calculated for each isolate, and a cutoff value was established to determine the susceptibility profile of the isolates. Results of the adapted method were compared with the standard susceptibility method (broth microdilution). An adapted method of MBT-ASTRA was developed. The RG cutoff values for meropenem were ≤0.1510 for susceptibility and >0.6272 for resistance, presenting 95.65% categorical agreement, with 2.9% (2/69) minor discrepancy and 3.23% (1/31) very major discrepancy. MBT-ASTRA can be used to provide rapid AST results with a simpler and more accessible protocol, especially regarding spectrum analysis. IMPORTANCE The simplification of the MBT-ASTRA technique, especially in spectrum analysis, can considerably allow more laboratories to rapidly determine antimicrobial susceptibility profiles.