P072

The European Committee on Antimicrobial Susceptibility Testing (EUCAST) has released a broth microdilution (BMD) Minimum Inhibitory Concentration (MIC) method to be used as a reference against which to calibrate drug susceptibility testing (DST) methods for Mycobacterium tuberculosis complex organisms (MTBC). The BACTEC™ MGIT™ (Mycobacterial Growth Indicator Tube) Automated Mycobacterial Detection System is the gold standard for liquid culture DST of MTBC. In this study the MIC results obtained using the EUCAST BMD reference method were compared to results obtained on the MGIT system for other antituberculosis antibiotics such as bedaquiline (BDQ), levofloxacin (LVX), moxifloxacin (D- cycloserine (DCS) and linezolid (LZD). Sets of MTBC strains known to be resistant and susceptible to each antibiotic by genotypic and/or phenotypic testing were used for this comparison. Essential agreement percentages (EA) between techniques were 100.0, 90.9 and 100.0% for LVX, DCS and LZD respectively, indicating that the two methods provide equivalent results for these antibiotics. However, for BDQ and MFX the EA were of 23.1 and 80.1% respectively. After using correction factors of ~3 and one two-fold dilutions for BDQ and MFX, the EA increased to 92.3% and 100.0% respectively. In conclusion, the MICs obtained by EUCAST BMD and MGIT system were equivalent for all the antibiotics tested after applying a correction factor if needed. The results described here underscore the importance of understanding the performance of the DST technique per antibiotic tested and how it correlates to a reference method.