Accuracy of the E test for determining antimicrobial susceptibilities of staphylococci, enterococci, Campylobacter jejuni, and gram-negative bacteria resistant to antimicrobial agents.
We compared the results of the E test MIC method with the results of agar dilution susceptibility testing for 18 antimicrobial agents against 324 strains of gram-positive and gram-negative bacteria, including 99 strains of staphylococci, 101 strains of antimicrobial-resistant gram-negative bacteria, 40 strains of enterococci, and 84 isolates of Campylobacter jejuni. Overall agreement of MICs (+/- 1 log2 dilution) was 97.3% for staphylococci, 94.6% for gram-negative bacilli, and 100.0% for enterococci. The MIC results for C. jejuni showed an overall agreement of only 82.9%. This was due primarily to a number of offscale values that limited the number of comparisons with clindamycin, trimethoprim-sulfamethoxazole, and tetracycline. Interpretative criteria for the results of the two test methods, however, were similar. Overall, the E test produced MIC results comparable to those of agar dilution when multiresistant organisms were tested. However, it was necessary to add 2% NaCl to the agar when testing oxacillin against staphylococci for both the E test and agar dilution to obtain results comparable to those of the broth microdilution method.
Huang
M B
MB
Nosocomial Pathogens Laboratory Branch, National Center for Infectious Diseases, Centers for Disease Control, Atlanta, Georgia 30333.
Baker
C N
CN
Banerjee
S
S
Tenover
F C
FC
D001419:Bacteria / Q000187:drug effects*; D016123:Campylobacter jejuni / Q000187:drug effects; D004352:Drug Resistance, Microbial; D016983:Enterococcus / Q000187:drug effects; D005069:Evaluation Studies as Topic; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000706:statistics & numerical data; D013210:Staphylococcus / Q000187:drug effects