EVALUATION OF THE E-TEST FOR SUSCEPTIBILITY TESTING OF THE BACTEROIDES-FRAGILIS GROUP

The susceptibilities of 100 clinical isolates belonging to the Bactero ides fragilis group to 9 antibiotics, i.e. ampicillin, piperacillin, c eftriaxone, cefotaxime, cefoxitin, imipenem, erythromycin, clindamycin , and metronidazole, were tested using a standard agar dilution method and the E-test. Overall, 81% of the E-test MICs were within one log(2 ) dilution step of the agar dilution MICs and 95% were within two log, dilution steps. The E-test showed significantly lower MIC Values than the agar dilution method for ampicillin, cefotaxime, and imipenem, an d significantly higher MIC values for piperacillin, ceftriaxone, eryth romycin, clindamycin, and metronidazole. However, this only resulted i n minor discrepancies that did not change the susceptibility status. T he E-test is easy to perform and read, and the MIC values correlated w ell with the MICs obtained by the agar dilution method when testing su sceptibility of the Bacteroides fragilis group.