Antimicrobial susceptibility testing of pathogenic Escherichia coli using non-standard conditions.

Results of non-standardized disc agar diffusion and broth microdilution antimicrobial susceptibility tests on blood culture isolates of Escherichia coli were compared with those of standardized tests. Test incubation at 40 degrees C, versus 35 degrees C, did not significantly affect results for either method. However, anaerobic incubation significantly altered results for several antimicrobials in both testing methods. The implications of these alterations will be discussed in the text.