A statistical analysis on the relationship of organism and site of infection to antimicrobial susceptibilities.

Disc agar diffusion tests were performed on 1340 clinical isolates (six common pathogens) to determine if the site of infection influenced antimicrobial susceptibility results for a given organism. There were several mathematically significant differences among sites and organisms, however the most important included cefoperazone (wound), piperacillin (sputum and urine) and tobramycin (sputum) against P. aeruginosa. Of these, only piperacillin was significantly less susceptible against P. aeruginosa lower respiratory tract isolates at our hospital. The impact of this on treatment (empiric) efficacy is unknown.