Agar disk elution method for susceptibility testing of Mycobacterium marinum and Mycobacterium fortuitum complex to sulfonamides and antibiotics
Stone, M.S.; Wallace, R.J.; Swenson, J.M.; Thornsberry, C.; Christensen, L.A.
Antimicrobial Agents and Chemotherapy 24(4): 486-493
1983
ISSN/ISBN: 0066-4804 PMID: 6651277 Document Number: 197308
An agar disc elution method using round well plates, supplemented Mueller-Hinton agar and commercial drug discs is described for susceptibility testing of M. marinum, and the rapidly growing mycobacteria to antibiotics and sulfonamides. By this method, 14 of 14 strains of M. marinum were susceptible to rifampin, doxycycline, minocycline and trimethoprim-sulfamethoxazole. Identical results were obtained with Middlebrook 7H10 agar and drugs prepared from standard powders. With 58 isolates of M. fortuitum and M. chelonei, this method had a 92% correlation with broth minimal inhibitory concentration determinations for cefoxitin and > 98% for doxycycline, kanamycin, amikacin and the sulfonamides. Of isolates of M. chelonei susceptible to amikacin on supplemented Mueller-Hinton agar, 69% were resistant on 7H10 agar; 15 of 16 M. chelonei isolates susceptible to erythromycin in broth were resistant by disc elution when an endpoint of no growth was used with either agar. The agar disc elution method offers a practical method for testing of most antibacterial agents against these mycobacterial species.