Limitations that the microbiologist should be aware of when utilizing cta carbohydrates for the differentiation of neisseria and moraxellaspecies?
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Answer:
Hardy Diagnostics CTA Media provide a nutritious basal medium composed of casein peptones, cystine, inorganic salts, phenol red, and agar. Necessary nutrients are supplied by the casein peptones and cystine. The inorganic salts serve as a source of essential ions. Phenol red is the pH indicator.
CTA Media supplemented with a 1% concentration of a specific carbohydrate are used to detect fermentation reactions. The 1% concentration is recommended to decrease the possibility of reversal reactions. Reversion occurs when the carbohydrate is depleted, thereby masking the acid by-products with alkaline by-products with peptone degradation. The acid produced by carbohydrate fermentation causes a decrease in pH, causing a color shift in the medium from red-pink to yellow.
The addition of agar to the medium allows for the detection of motility along the stab line of inoculation. Motile organisms extend from the stab line and produce turbidity or cloudiness throughout the medium. Non-motile organisms grow only along the stab line and leave the surrounding medium clear.
CTA Base (Cat. no. Y11) medium is a carbohydrate-free medium that can be used as a holding medium for fastidious microorganisms at 25ºC.