Comparison of antimicrobial susceptibilities of Pseudomonas aeruginosa isolates, with and without plaques, from two hospitals.

Disc-agar diffusion plates, used for antimicrobial susceptibility testing, of 368 Pseudomonas aeruginosa isolates with and without plaques were compared. Seventeen percent of all isolates from the Veterans Administration Medical Center and eleven percent from Oklahoma Memorial Hospital produced plaques. When percentages of susceptibility for plaque and non-plaque containing isolates were compared, there were some statistically significant differences which are discussed in the text.