How should mucoid strains of Pseudomonas aeruginosa from cystic fibrosis patients be tested?

Answer:

Either one of the NCCLS reference methods, disk diffusion or broth microdilution or agar dilution can be used. This is addressed in the newest NCCLS Table 2B. The specific comment that appears in both the disk diffusion (M2) and MIC (M7) tables states that "The susceptibility of Pseudomonas aeruginosa isolated from patients with cystic fibrosis can be reliably determined by the reference agar dilution or broth microdilution (or disk diffusion) methods, but may require extended incubation up to 24h". This recommendation resulted from work performed by Dr. Lisa Saiman at the cystic fibrosis research laboratory at Columbia Presbyterian Hospital in New York and colleagues including Dr. Ron Jones at the University of Iowa and Dr. Jane Burns at Children's Hospital in Seattle.

References:

National Committee for Clinical Laboratory Standards. (2001). Performance standards for antimicrobial susceptibility testing; Eleventh informational supplement, M100-S11. NCCLS, Wayne, PA.

-Table 2b: footnote 2 (M2-disk diffusion tables); footnote 2 (M7-MIC tables)

Burns, JL, L Saiman, S Whittier, D Larone, J Krzewinski, Z Liu, SA Marshall, and RN Jones. 2000. Comparison of agar diffusion methodologies for antimicrobial susceptibility testing of Pseudomonas aeruginosa isolates from cystic fibrosis patients. J Clin Microbiol. 38:1818-1822.

Saiman, L, JL Burns, S Whittier, J Krzewinski, SA Marshall and RN Jones. 1999. Evaluation of reference dilution test methods for antimicrobial susceptibility testing of Pseudomonas aeruginosa strains isolated from patients with cystic fibrosis. J Clin Microbiol. 37:2987-2991.