Table 6.

Percent agreement by interpretive category among four laboratories for microdilution testing of M. abscessus,M. chelonae, and the M. fortuitum groupa

Drug% Agreement (category) forb:
M. abscessusM. chelonaeM. fortuitum group
1801180218071814183118661351135213531359
Amikacin97.2 (S/I)82.3 (S/I)100 (S/I) 97.2 (R)55.6 (S/I)88.9 (S/I)100 (S)100 (S)100 (S)100 (S)
Cefoxitinc 91.7 (S/I)77.8 (S/I)100 (S/I)100 (R)100 (R)100 (R)77.8 (S/I)58.3 (S/I)100 (S/I)100 (S/I)
Ciprofloxacin100 (R)100 (R)100 (R) 94.4 (R)83.3 (R)97.2 (R)100 (S)100 (S)100 (S)100 (S/I)
Clarithromycin100 (S/I)100 (R)100 (S)100 (S)100 (S)100 (R)61.1 (R)58.3 (R)100 (S)100 (S)
Doxycycline100 (R)100 (R)100 (R)100 (S/I)100 (R)100 (R)97.2 (R)100 (R)100 (S)100 (S)
Imipenem55.5 (S/I)66.7 (R) 50d 80.5 (R)72.2 (R)77.8 (R)91.7 (S/I)63.9 (S/I)58.3 (S/I)100 (S/I)
Sulfamethoxazole86.1 (R)100 (R)100 (R) 91.7 (R)97.2 (R)97.2 (R)100 (S)88.9 (S)97.2 (S)91.7 (S)
Tobramycin 50d 100 (S/I)100 (S/I)
  • a Interpretive category suggested in the American Society for Microbiology Clinical Procedures Handbook (3).

  • b S, susceptible; I, intermediate; R, resistant.

  • c Percent agreement based on new recommended breakpoints (≤16 μg/ml, susceptible; 32 to 64 μg/ml, intermediate; ≥128 μg/ml, resistant) is 100% for all isolates except 1802 (97.2%) and 1352 (86.1%).

  • d Intermediate, 50%; resistant, 50%.