Validation of a Novel Medium for Drug Susceptibility Testing of Mycobacterium Tuberculosis against First- and Second-Line Drugs: AYC.2.2 Agar and AYC.2.1 Broth

Background: The aim of this study was the validation of AYC.2.2 agar and AYC.2.1 broth for the breakpoint values of first- and second-line drugs for Mycobacterium tuberculosis. Method: A total of 12 isolates including 5 reference strains and 7 well-defined clinical isolates were tested for their antituberculosis susceptibilities. Inhibitory effects of first- and second-line antituberculous drugs including isoniazid, rifampicin, streptomycin, ethambutol, amikacin, capreomycin, kanamycin, para-aminosalicylic acid, ethionamide, rifabutin, ofloxacin, levofloxacin, and moxifloxacin were tested. Results: According to the minimal inhibitory concentration values obtained in 7H10 agar, 7H9-S broth, AYC.2.2 agar, and AYC.2.1 broth, category agreement is 100%, and very major discrepancy (MAD), MAD, and minor discrepancy ratios were determined as 0 for all drugs. Conclusion: It was concluded that breakpoint values by CLSI recommendation for 7H10 agar can be also used for AYC.2.2 agar and AYC.2.1 broth. In addition, further multicenter studies are needed to use the new medium in routine mycobacteriology laboratories.