STREPQUICK

Effective Date: 
Fri, 10/17/2014
Reviewed: 
Tue, 01/10/2017
Policy: 

Hardy Diagnostics StrepQuick™ test kit is intended to aid in the identification of gram-positive, catalase-negative cocci based on pyroglutamate aminopeptidase (PYR), leucine aminopeptidase (LAP), and esculin hydrolysis (ESC) activity. This test kit simplifies identification of Enterococcus spp. and group B streptococci (Streptococcus agalactiae).

 

Materials

Standard microbiological supplies and equipment such as loops, other culture media, swabs, applicator sticks, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

 

Quality Control

Streptococcus agalactiae ATCC® 12386 and Enterococcus faecalis
ATCC® 29212 should be tested each day of use for expected reactions.

 

Procedure: 

Specimen Collection:

This product is not intended for primary isolation of patient specimens. It should be used only with cultures of isolated organism. This product is used in conjunction with other biochemical or serological tests to identify cultures of isolated organism.

Method of Use:

Note: Perform Gram stain and catalase test prior to inoculating StrepQuick™. Test organisms should be gram-positive cocci that are aerobic or facultatively anaerobic and catalase-negative.

1) Moisten each test circle slightly with a single drop of distilled or deionized water. Do not saturate.

2) Using a sterile plastic loop, pick 2-3 well isolated, 18-24 hour colonies and rub into a small area of the PYR reaction circle so that there is a visible paste.

3) Repeat step 2 for the LAP and ESC test circles.

Note: Take care not to carry over substrate from one circle to the next.

4) After the test organism has been inoculated onto the test circles, allow it to react for ten minutes.

5) After the 10 minute incubation period add one drop of chromogenic developer to the PYR and LAP circles.

6) Immediately after addition of the chromogenic developer, observe for the development of a bright pink or cherry red color in the PYR and LAP circles. The reaction should be read only in the area of the card where the organism was inoculated. A diffuse, light pink color covering the entire test area is not considered positive and should be disregarded. Any color development in the PYR and LAP circles appearing after 1 minute should be disregarded. Color development of orange, yellow or salmon in the PYR circle should be interpreted as a negative reaction.

7) Observe for a light gray to gray color to form in the ESC circle. Any darkening at all should be considered positive. Allow 10-15 minutes for full color development.

Interpretation

 

TEST Positive Reaction Negative Reaction
PYR Red or bright pink color Yellow, salmon, orange or no color
LAP Red or bright pink color No color
Esculin Gray to light gray color Other than grey

 

Consult "Expected reactions of select organisms" table in the package insert to identify organism tested.

Key Points: 

Limitations

 

It is recommended that biochemical and/or serological tests be performed on colonies from pure culture for complete identification. Consult listed references for more information.

A Gram stain and catalase test should be performed to confirm the presence of gram-positive, catalase-negative cocci.

Only pure cultures or isolated colonies of gram-positive, catalase-negative cocci should be tested; mixed cultures may give false-positive reactions.

Staphylococcus, Aerococcus, most Corynebacterium haemolyticum, as well as some Enterobacteriaceae and other gram-negative bacilli, are PYR positive.(1,9)

For PYR and LAP tests, after addition of the developer, color development after 1 minute should be disregarded.(5)

For PYR and LAP test, after the addition of the developer, the development of a diffuse, light pink color covering the entire test area is not considered positive and should be disregarded.

False-negative results can occur for any of the reactions if inadequate inoculum is used.(5)

Bile tolerance is not included in the esculin hydrolysis test, so results obtained with StrepQuick™ may not correlate with results obtained from Bile Esculin media.

 

References

 

1. Murray, P.R., et al. 2011. Manual of Clinical Microbiology, 10th ed. American Society for Microbiology, Washington, D.C.

2. Forbes, B.A., et al. 2007. Bailey and Scott's Diagnostic Microbiology, 12th ed. C.V. Mosby Company, St. Louis, MO.

3. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

4. Koneman, E.W., et al. 2006. Color Atlas and Textbook of Diagnostic Microbiology, 6th ed. J.B. Lippincott Company, Philadelphia, PA.

5. MacFaddin, Jean F. 2000. Biochemical Tests for Identification of Medical Bacteria, 3rd ed. Lippincott Williams & Wilkins, Philadelphia, PA.

6. Facklam, R., et al. 1995. Evaluation of three disk tests for identification of enterococci, leuconostocs, and pediococci. J. Clin. Microbiol.; 33:885-887.

7. Bosley, G.S., et al. 1983. Rapid identification of enterococci. J. Clin. Microbiol.; 18:1275-1277.

8. Anderson, N.L., et al. 2005. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

9. Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology. Williams & Wilkins, Baltimore, MD.

10. Ruoff, K.L., D.R. Kuritzkes, J.S. Wolfson and M.J. Ferraro. 1988. J. Clin. Microbiol.; 26:2064-2068.