Technique CARBOHYDRATE UTILIZATION
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Principle  
Cautions These utilization tests must be ad equately controlled to prevent carry over from the medium on which the inoculum was grown.

Some cultures will first produce acid and then revert to an alkaline medium (see decarboxylases).

Gas production is not a reliable indicator of carbohydrate fermentation as some anaerobes produce gas from proteins.

The basal broth may have to be supplemented with sterile rabbit serum for use with the Neiseeria (for glucose lactose, maltose and sucrose).

Bacillus requires an ammonium salt sugars agar salnt with bromocresol purple as an indicator.

Lactobacilli require an MRS broth supplemented with the carbohydrate and with chlorophenol red as an indicator.
Method Inoculate nutrient broth cultures and examine daily for 7 days for the production of acid or acid and gas. Negative cultures should be examined for up to 30 days..
Results GRO WTH Growth or failure to grow on specified media can depending on the media, indicate
(i) nutrtional needs;
(2) sensitivity or insensitivity to substances in the medium;
(3) ability to use a specified compound as a source of particular elements

Examples of the characters revealed are
(1) growth on blood agar but not on the basal medium indicates a need for enrichment with blood;
(2) failure to grow on MacConkey accompanied by growth on nutrient agar, shows sensitivity to bile salt, growth on media containing 6.5% NaCl shows an unusual degree of salt tolerance;
(3) failure to grow on Koser's citrate medium shows that the organism cannot use citrate as a carbon source under the conditions tested.

Positive control  
Negative control  
Reagents  
Reference