DETERMINATION OF ANTI-MICROBIAL SUSCEPTIBILITY OF PSEUDOMONAS-AERUGINOSA BY DISK DIFFUSION AND MICRODILUTION METHODS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 41  (6) , 906-909
Abstract
Disk diffusion susceptibility tests were performed on 180 recent clinical isolates of P. aeruginosa. Minimal inhibitory concentration values were determined at the same time by a broth microdilution method. All isolates were sensitive to colistin (< 4 .mu.g/ml), but resistant to ampicillin (.gtoreq. 16 .mu.g/ml), cephalothin (.gtoreq. 64 .mu.g/ml) and nitrofurantoin (> 64 .mu.g/ml). More than 90% of the isolates were sensitive to gentamicin (median, .ltoreq. 0.25 .mu.g/ml), tobramycin (median, .ltoreq. 0.25 .mu.g/ml) and amikacin (median, .ltoreq. 1.0 .mu.g/ml) and more than 70% were sensitive to carbenicillin (median, 64 .mu.g/ml). When the resistant and intermediate categories were combined, over 90% of the isolates were resistant to tetracycline (median 16 .mu.g/ml), chloramphenicol (median, > 32 .mu.g/ml), kanamycin (median, 16 .mu.g/ml) and trimethoprim-sulfonamide combination (median, 4 .mu.g/ml; 76 .mu.g/ml). Differences between the disk diffusion and microdilution methods in distinguishing resistant isolates of P. aeruginosa from sensitive isolates were minor. Complete agreement between the 2 methods was obtained in 87.0% of the observations.