A standardized inoculum made from a pure culture of aerobic actinomycete is prepared and inoculated into wells of a microtiter plate containing different concentrations of 13 antimicrobial agents. These include trimethoprim/ sulfamethoxazole, linezolid, ciprofloxacin, imipenem, moxifloxacin, cefepime, augmentin, amikacin, ceftriaxone, doxycycline, minocycline, tobramycin, and clarithromycin.
Growth at specified breakpoints is indicative of resistance.(Wallace RJ Jr, Steele LC: Susceptibility testing of Nocardia species for the clinical laboratory. Diagn Microbiol Infect Dis 1988;9:155-66; Clinical Laboratory Standards Institute: Susceptibility Testing of Mycobacteria, Nocardiae, and Other Aerobic Actinomycetes. CLSI document M24-A, CLSI, Wayne, PA, 2003)