COMPARISON OF E-TEST AND AGAR DILUTION FOR ANTIMICROBIAL SUSCEPTIBILITY TESTING OF STENOTROPHOMONAS-(XANTHOMONAS)-MALTOPHILIA

Currently recommended dilution test methods for the determination of a ntimicrobial susceptibility of Stenotrophomonas (Xanthomonas) maltophi lia are labor-intensive and often impractical in many clinical laborat ories. We compared the E test with the agar dilution method for suscep tibility testing of 176 clinical isolates of S. maltophilia against 16 antimicrobial agents. The MICs obtained by E test correlated well wit h those determined by the agar dilution method, with an overall agreem ent of 94%. Very major and major errors occurred infrequently (0.6 to 2.9%) when testing beta-lactam agents, tobramycin, trimethoprim-sulfam ethoxazole, and fluoroquinolones. The E test was found to be accurate and easy to perform. For most antimicrobial agents tested against S. m altophilia, the E test is an acceptable alternative susceptibility tes t method.