A-289 The Accuracy Evaluation of Commercialized Antimicrobial Susceptibility Testing Reagents for Carbapenems on Enterobacteriaceae

Background With the misuse of antibiotics, Enterobacteriaceae bacteria have become increasingly resistant to numerous antibiotics, especially carbapenem, as one of the last defense lines in the treatment of multidrug-resistant infections. In response to the demand for carbapenem resistance detection, a variety of commercialized antimicrobial susceptibility testing (AST) reagents emerged in the market, including disc diffusion, broth microdilution, and automated system-based assays. However, considering different mechanisms, there exist certain limitations in the detection accuracy of different products. Therefore, it is important to evaluate the detection accuracy of related commercialized reagents. Methods A total of 60 cases of Enterobacteriaceae bacteria were collected and evaluated by the automatic microorganism ID/AST analyzer (AutoMic-i600, Autobio) and disc diffusion (imipenem, meropenem and ertapenem, Oxoid), while broth microdilution as the reference method. The supporting reagent of automated system-based assays was Enterobacteriaceae AST kit (Autobio). MH agar media were used during experiments. Results Compared with reference method, the essential agreement (EA) and the category agreement (CA) of imipenem, meropenem and ertapenem using AutoMic-i600 can achieve higher than 90%, and the very major error (VME) was less than 3%, without major error (ME). The disc diffusion showed similar CA with the system for ertapenem, but with lower CA and higher ME for imipenem and meropenem (Table 1). Conclusion It presented that different AST reagents vary in the detection accuracy of carbapenem on Enterobacteriaceae. Although the broth microdilution is the gold standard, it is complex and requires more experimental cost and time. The disc diffusion is preferred method by many clinical laboratories due to its economy and convenience. Besides, the automated system-based assays are more recommended in terms of simpler operation and wider detection range, which showed a slightly superior compliance rate than the disc diffusion. Based on the clinical requirements and actual resources, laboratories can choose the appropriate assay. If possible, the combined use of multiple methods can be considered, for example, the automated system-based testing can be used for initial screening, while suspicious results can be further confirmed by broth microdilution to enhance the accuracy of carbapenem-resistant Enterobacteriaceae detection.