Evaluation of E test as a rapid method for determining MICs for nutritionally variant streptococci.
E test was evaluated as an alternative rapid and simple method of MIC estimation for nutritionally variant streptococci. E test with various media was compared with conventional broth and plate dilution techniques supplemented with 0.001% (wt/vol) pyridoxal hydrochloride (vitamin B6). Of the 14 strains tested with E test, isosensitest agar supplemented with 5% defibrinated horse blood and 0.001% pyridoxal HCl, with and without 0.01% cysteine, gave complete agreement within one twofold-dilution titer of the agar reference method and between 93 and 86% agreement within one twofold-dilution titer of the broth reference method. E test MICs with other media were comparable; however, these were considerably more difficult to interpret. Use of Mueller-Hinton and Columbia-based supplemented agar showed hazy growth and double zoning around the endpoint, respectively. The addition of 0.01% (wt/vol) cysteine to media exhibited no significant effect, and incubation in 5% carbon dioxide (CO2) did not affect MICs.
Douglas
C P
CP
Department of Microbiology and Infectious Diseases, Concord Repatriation General Hospital, New South Wales, Australia.
Siarakas
S
S
Gottlieb
T
T
D000362:Agar; D000409:Alanine / Q000378:metabolism; D000818:Animals; D003470:Culture Media; D003545:Cysteine / Q000494:pharmacology; D004697:Endocarditis, Bacterial / Q000382:microbiology; D006736:Horses / Q000097:blood; D006801:Humans; D007201:Indicator Dilution Techniques; D008826:Microbial Sensitivity Tests; D011736:Pyridoxine / Q000378:metabolism / Q000494:pharmacology; D013291:Streptococcus / Q000145:classification / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism
D003470:Culture Media; D013438:Sulfhydryl Compounds; D000362:Agar; D003545:Cysteine; D011736:Pyridoxine; D000409:Alanine