The accuracy of antimicrobial disk sensitivity testing in urinary tract infections

Fifty bacterial strains shown resistant to ampicillin, cephalothin or tetracycline by Kirby-Bauer disk diffusion susceptibility testing were isolated from patients with urinary infections. Inhibitory activity in urine of volunteers given these antimicrobial agents and tube dilution sensitivity testing indicated that agar disk diffusion gradients do not provide sufficiently high antimicrobial concentrations to predict accurately clinical efficacy.