Error rates associated with the use of recently proposed breakpoints for testing Pseudomonas aeruginosa versus gentamicin, tobramycin, and amikacin by the standardized disk agar diffusion test
- 1 November 1983
- journal article
- Published by American Society for Microbiology in Antimicrobial Agents and Chemotherapy
- Vol. 24 (5), 764-770
- https://doi.org/10.1128/aac.24.5.764
Abstract
Two hundred fifteen Pseudomonas aeruginosa isolates were tested in parallel by the disk agar diffusion test, using a standardized agar preparation, and by a microbroth test, using dilutions differing by small arithmetic increments. For gentamicin, recently proposed breakpoints of resistance (R) less than or equal to 12 mm and susceptibility (S) greater than or equal to 16 mm produced error rates of 20 and 6.8%, respectively. Limiting the error rate for susceptible interpretations to less than or equal to 2% produced a widening of the intermediate zone to include 67.4% of the isolates tested. For tobramycin, the recently proposed breakpoints of R less than or equal to 12 mm and S greater than or equal to 15 mm were associated with error rates of 66.7 and 1.4%, respectively. Breakpoints of R less than or equal to 12 mm and S greater than or equal to 13 mm were demonstrated to be equally effective when the error rate for susceptible interpretations was limited to less than or equal to 2% by error rate-bound analysis. For amikacin, proposed breakpoints of R less than or equal to 14 mm and S greater than or equal to 17 mm were associated with error rates of 27.3 and 3.2%, respectively. Limiting the error rates for susceptible interpretations to less than or equal to 2% required breakpoints of R less than or equal to 14 mm and S greater than or equal to 18 mm. The ability to establish effective susceptibility breakpoints for tobramycin and amikacin appeared not to be related to the disk agar diffusion test process itself but rather to the high degree of susceptibility of the P. aeruginosa population. These findings severely limit the usefulness of the disk agar diffusion procedure for testing P. aeruginosa versus the aminoglycosides. For this purpose, we recommend dilution tests which employ small arithmetic increment schemes.Keywords
This publication has 17 references indexed in Scilit:
- Effect of ionized calcium and soluble magnesium on the predictability of the performance of Mueller-Hinton agar susceptibility testing of Pseudomonas aeruginosa with gentamicinAntimicrobial Agents and Chemotherapy, 1981
- Interpretation of agar diffusion testsJournal of Antimicrobial Chemotherapy, 1980
- Cation Components of Mueller-Hinton Agar Affecting Testing of Pseudomonas aeruginosa Susceptibility to GentamicinAntimicrobial Agents and Chemotherapy, 1980
- Effect of Different Lots of Mueller-Hinton Agar on the Interpretation of the Gentamicin Susceptibility of Pseudomonas aeruginosaAntimicrobial Agents and Chemotherapy, 1978
- Effect of Cation Content of Agar on the Activity of Gentamicin, Tobramycin, and Amikacin against Pseudomonas aeruginosaThe Journal of Infectious Diseases, 1978
- Emergence in a Burn Center of Populations of Bacteria Resistant to Gentamicin, Tobramycin, and Amikacin: Evidence for the Need for Changes in Zone Diameter Interpretative StandardsAntimicrobial Agents and Chemotherapy, 1977
- Susceptibility Tests of Anaerobic Bacteria: Statistical and Clinical ConsiderationsThe Journal of Infectious Diseases, 1974
- Antibiotic Susceptibility Testing of Pseudomonas aeruginosa: Selection of a Control Strain and Criteria for Magnesium and Calcium Content in MediaThe Journal of Infectious Diseases, 1974
- Performance of Mueller-Hinton Agars Prepared by Three Different ManufacturersAmerican Journal of Clinical Pathology, 1974
- Effect of medium composition on the apparent sensitivity of Pseudomonas aeruginosa to gentamicinJournal of Clinical Pathology, 1969