Evaluation of Etest for testing antimicrobial susceptibilities of Neisseria gonorrhoeae isolates with different growth media.

The MICs for 101 isolates of Neisseria gonorrhoeae obtained by Etest (AB-Biodisk, Solna, Sweden) and the agar dilution method on GC medium base supplemented with 1% Kellog's defined supplement (GCMB) were compared. The overall percent agreement (within 1 log2 dilution) between methods was greater than 97.9. The Pearson's correlation coefficients for penicillin, tetracycline, erythromycin, and ceftriaxone for the two methods were 0.98, 0.97, 0.93, and 0.93 (P = 0.001), respectively, for comparisons on GCMB. The overall percent agreement was lower when hemoglobin-supplemented GCMB was used. Etest is an attractive alternative to the agar dilution method for gonococcal antimicrobial susceptibility testing and should be further analyzed in multicenter studies.