Cefoperazone: regression analysis, disk content, and disk susceptibility testing considerations
Wright, D.N.; Welch, D.F.; Saxon, B.A.; Clark, S.J.; Matsen, J.M.
Antimicrobial Agents and Chemotherapy 22(3): 493-498
1982
ISSN/ISBN: 0066-4804 PMID: 6215895 Document Number: 187972
Cefoperazone agar dilution minimal inhibitory concentration (MIC) susceptibility results were compared with zones of inhibition produced by disc diffusion susceptibility testing. Discs containing 30, 50, 75 and 100 .mu.g of cefoperazone were tested for purposes of regression line comparisons and error rate-bounded analysis. Results suggest that if the MIC equivalent of susceptibility is 32 .mu.g/ml, either a 50-.mu.g disc with zone sizes of susceptibility (S) .gtoreq. 15 mm and resistance (R) .ltoreq. 12 mm or a 75-.mu.g disc with zone sizes of S .gtoreq. 17 mm and R .ltoreq. 14 mm may be appropriate. If the MIC equivalent of susceptibility is 64 .mu.g/ml, this would dictate use of a 75-.mu.g disc with zone sizes of S .gtoreq. 17 mm and R .ltoreq. 12 mm. Discs containing either .ltoreq. 30 or .gtoreq. 100 .mu.g of cefoperazone did not adequately discriminate among susceptible and resistant bacterial strains at either the 32- or 64-.mu.g/ml MIC equivalent.