clinical diagnostic tests

Dr. James D. Oliver jdoliver at EMAIL.UNCC.EDU
Wed Dec 9 10:10:40 EST 1998

>The second test you refer to must be Hugh and Leifson's formulation of a medium

>called OF Basal Medium.  This medium is also a basal medium to which one can

>add many different carbohydrates. The medium is green and set at a pH of around

>6.8-7.2. If the organism ferments a carbohydrate, the medium will turn yellow

>from acid production. I believe oxidative utilization of the carbohydrate will

>produce a blue color in the medium. It is used for carbohydrate utilization

>tests of "non-fermentors" such as Psuedomonas.


This is not a fully accurate answer.  OF is usually used with two tubes per test strain.  One tube is overlaid with sterile mineral oil after inoculation, the other is left open.  Growth and sugar utilization (whichever is included in the basal medium) in the open tube only indicates oxidative (respiratory) metabolism.  Growth and acid production in both indicates fermentation. Growth only in the closed tube (not usually seen) would indicate a strict anaerobe.  Positive reactions are yellow, from the original green. Blue means an alkaline reaction, such as splitting of the amino acids in the medium, as opposed to use of the sugar.


James D. Oliver

Professor of Microbiology and Director,

Interdisciplinary Biotechnology Program

University of North Carolina at Charlotte

9201 University City Blvd.

Charlotte, NC  28223-0001

Tel.  (704) 547-4049

Fax   (704) 547-3457



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