A comparison of Sensititre™ Anaerobe MIC plate with ATB ANA® test for the routine susceptibility testing of common anaerobe pathogens

The accuracy of the Thermo Scientific™ Sensititre™ Anaerobe MIC plate was assessed against the ATB ANA® test (bioMérieux) on 56 clinically relevant anaerobic strains collected at Geneva University Hospitals. The overall categorical agreement between both methods reached 95%. The Sensititre™ Anaerobe MIC plate had excellent accuracy for most antibiotics tested. When the Sensititre™ Anaerobe MIC plate disagreed with ATB ANA® test, the gradient strip method resolved the antimicrobial susceptibility categories of all the antibiotics tested, except for piperacillin, piperacillin-tazobactam, and penicillin, in favor of the Sensititre™ Anaerobe MIC plate (58% [21 out of 36]). Several very major errors were observed for piperacillin (12.5% [7 out of 56]), piperacillin-tazobactam (12.5% [7 out of 56]), and penicillin (2% [1 out of 56]). The gradient strip method revealed that the categorical differences for piperacillin, piperacillin-tazobactam, and penicillin were at least partly explained by heterogeneity in resistance expression. The Sensititre™ Anaerobe MIC plate offers therefore a useful alternative to the ATB ANA® test for the routine antimicrobial susceptibility testing of anaerobes in clinical microbiology laboratories.