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STAPHYLASE TEST KIT DR0595

The generally accepted identifying characteristic of Staphylococcus aureus is the ability to produce free and bound coagulase (or clumping factor). The presence of clumping factor may be detected in a number of ways. The Oxoid Staphylase Test detects the presence of clumping factor through clumping of fibrogensensitized sheep red blood cells^1,2. The specificity of the reaction is ensured by a simultaneous test with a control reagent (unsensitized sheep red blood cells), when of course no clumping reaction should be observed.

Reagents
DR0596 Staphylase Test Reagent
Consists of rabbit fibrogen-sensitized sheep red blood cells.
DR0597 Staphylase Control Reagent
Consists of unsensitized sheep red blood cells.
Disposable Reaction Cards.
Each kit contains sufficient reagent for 100 tests.

Precautions
For in vitro use only
Do not freeze the reagents.

Preservatives
Both reagents contain 0.1% sodium azide as preservative.

Storage
The reagents must be stored at 2-8°C where they will retain their reactivity until the date shown on the bottle.

Preparation of Cultures
Bacterial cultures for identification can be grown on either selective media (e.g. Mannitol salt agar, Baird-Parker medium) or non-selective media (e.g. Blood
agar).
If necessary, carry out Gram stain and catalase tests on the colonies to confirm the presence of Gram-positive, catalase-positive cocci.

Test Method
1. Shake the Test and Control reagents vigorously to obtain a homogenous suspension. Any reagent cells that may be trapped in the dropping pipette must be mixed into the suspension.
2. Using a loop, smear 1 to 3 of the suspect colonies on a test circle and a control circle on the Reaction Card.
3. Add 1 drop of the Test Reagent to the test circle and 1 drop of Control Reagent to the control circle.
4. Mix the contents of the test circle using a loop. Flame the loop, then mix the contents of the control circle. Observe for agglutination while mixing.
5. Dispose of the Reaction Card safely into disinfectant.

Test Results
A positive result is obtained if clumping of the test cell suspensions occurs during mixing. This indicates the presence of Staphylococcus aureus.
Results cannot be interpreted if there is any clumping of the control cell suspension. In these cases, culture purity and identity should be checked.

Limitations of the Test
Occasional false positive results may be found with strains of Staphylococcus sciuri. Other rarely isolated staphylococci may also give positive Staphylase results. I suspected, the isolate should be identified by biochemical tests.
The use of high-salt media may result in a weaker reaction than usual. Also the colonies taken from these types of media may be more difficult to emulsify with
the reagents and may therefore give rise to a slightly stringy reaction.
Strains of Staphylococcus aureus which do not possess a clumping factor will not give a positive reaction in this test. Such strains are found to be more common in veterinary medicine.

Performance Characteristics
The Staphylase Test was evaluated in an independent laboratory³. A total of 2090 routine clinical isolates were tested. Each isolate was tested by the Staphylase Test, the tube coagulase test and certain of the isolates subjected to further test, including biochemical tests.

^a This strain was tube coagulase negative, slide coagulase positive, and biochemically identified as Staphylococcus aureus
^b One of these strains was tube coagulase negative, slide coagulase negative, DN-ase negative, and biochemically identified as Staphylococcus sciuri. The other strain was tube coagulase negative and slide coagulase negative. Further investigation of this strain was not possible.
The Staphylase Test therefore gave correct results with 1662 of the 1662 strains of Staphylococcus aureus, a sensitivity of 100%.
For 428 non- Staphylococcus aureus strains, the Staphlase Test gave 426 correct negative results, a specificity of 99.5%.

References
1. Flandrois J.P. and Carret G. (1981) Zbl. Bakt. Hyg.orig. A251, 171-176.
2. Duthie E.S. (1955) J. Gen. Microbiol. 13, 383-393.
3. Data on file at Oxoid Ltd