CatScreen™ is a rapid test for the detection of butyrate esterase for the presumptive ID of Moraxella (Branhamella) catarrhalis.


Hardy Diagnostics CatScreen™ is a rapid test for the detection of the enzyme butyrate esterase in bacteria isolated on culture media for the presumptive identification of Moraxella (Branhamella) catarrhalis.


The CatScreen™ is used to confirm the identification of Moraxella (Branhamella) catarrhalis when used in conjunction with chromogenic substrate tests or carbohydrate fermentations, oxidase reaction, gram stain and morphology. For presumptive identification of M. catarrhalis, the CatScreen™ may be used along with the oxidase reaction, gram stain and colony morphology.The value of tributyrin hydrolysis for differentiating M. catarrhalis from Neisseria spp. was first reported by Berger in 1962. Subsequently, several authors have reported the usefulness of butyrate esterase in differentiating the two organisms using various substrates. Butyrate hydrolysis is listed in standard reference texts as a key test in differentiating M. catarrhalis from Neisseria spp.Disks impregnated with bromo-chloro-indolyl butyrate serve as the substrate for the detection of butyrate esterase. Hydrolysis of the substrate by the butyrate esterase yields a chromogenic compound which appears blue to blue-violet in color.


The CatScreen™ Kit contains 25 disks impregnated with 0.35% bromo-chloro-indolyl butyrate in a volatile organic solvent, followed by desiccation.


Specimen Collection: This product is not intended for primary isolation of patient specimens. This product is used in conjunction with other biochemical tests to identify cultures of isolated organisms.The appropriate organism for performing the butyrate test is an oxidase-positive, gram-negative diplococcus exhibiting typical morphology of Moraxella (Branhamella) catarrhalis.


1. Remove disk from vial and place on a clean glass slide or petri dish lid.

2. Add one drop of distilled or deionized water to moisten the disk.

3. Obtain a heavy, visible inoculum with a sterile wooden applicator stick or loop from a 24-72 hour old culture and rub it onto the disk.

4. Incubate at room temperature (15-30 degrees C.) for up to 5 minutes.


A positive test resulting in a blue to blue-violet color within 5 minutes indicates the hydrolysis of bromo-chloro-indolyl butyrate by butyrate esterase. A negative test is indicated by no color change.

Incubation for slightly longer periods may yield false-positive results. Do not read after 5 minutes.  

Cat. no. HDZ110

Size: 25 tests


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