J Clin Pathol Qual Control.  1999 Dec;21(2):287-294.

Calculation of Minimal Inhibitory Concentrations of Carbapenem from Zone Diameters of Disk Diffusion Test of Carbapenem-Resistant Nonfermentative Gram-Negative Bacilli

• Uh Y
• Jang IH
• Hwang GY
• Kim KS
• Yoon KJ

Abstract

BACKGROUND: The disk diffusion susceptibility test, when performed by the standard method, yields highly accurate and reproducible results for the most clinical isolates. The report of MICs, however, is important in severe infections and in cases of multiple drug resistance. The aim of this study was to obtain the best regression function model between zone diameters and MICs of carbapenem on imipenem-resistant nonfermentative Gram-negative bacteria for quantitative reports of carbapenem susceptibility.
METHODS
A total of 138 nonfermentative Gram-negative bacteria consisting of 112 imipenem-resistant isolates and 26 imipenem-susceptible isolates were tested by agar dilution and disk diffusion method with imipenem and meropenem. And best linear regression function model between zone diameters and MICs of carbapenem were obtained by statisical analysis of SPSS software.
RESULTS
Linear regression function of imipenem and meropenem were Y1 =e((5,2090-0,1741*x1))and Y2 =e((5,0038-0,1850*x2)) (Y1 = MIC of meropenem, X2 = zone diameter of imipenem; R2 of imipenem=0.9458; Y2 = MIC of meropenem, X2 = zone diameter of meropenem; R2 of meropenem = 0.9054), respectively.
CONCLUSIONS
This method, which was designed to calculate MICs from disk diffusion zone diameters of imipenem and meropenem, may be very useful to make a decision in antimicrobial therapy of patients infected by carbapenem-resistant nonfermentative Gram-negative bacteria.

MeSH Terms

Agar
Diffusion*
Drug Resistance, Multiple
Gram-Negative Bacteria
Humans
Imipenem
Linear Models
Agar
Imipenem