Q-SLIDE™ GRAM

Cat. no. Z302 Q-Slide™ Gram 5 slides/box

INTENDED USE

Hardy Diagnostics Q-Slide™ Gram control slides are used to qualify reagents and the method used in gram stain procedures.

SUMMARY

The gram stain is critical to the identification of organisms in clinical and industrial specimens. Q-Slide™ Gram control slides are used to ensure the quality of reagents used as well as the efficacy of staining procedures. Methanol fixed smears of Staphylococcus aureus and Escherichia coli serve as the positive and negative controls. The remainder of the slide is marked with a grid to allow for the simultaneous staining of up to four unknown specimens in parallel with the positive and negative control.

The gram stain differentiates bacteria on the basis of their cell wall structure. Gram-positive organisms have a very thick peptidoglycan layer in their cell wall compared to that of gram-negative organisms. Crystal violet stain complexes with the mordant, Gram's iodine and becomes integrated within the peptidoglycan layer. When the smear is decolorized, the crystal violet/iodine complex is washed out of the gram-negative cell wall, but the complex remains integrated within the thicker peptidoglycan layer of the gram-positive organisms. Counterstain is used to give a visible color to the gram-negative cells that were decolorized. Safranin is the most common counterstain used, but carbolfuchsin can be used for faintly staining organisms.

STORAGE AND SHELF LIFE

Upon receipt store at 15-30ºC. in the original container. Do not use if there are any signs of deterioration. Protect from moisture and dust.

PRECAUTIONS

PROCEDURE

SLIDE PREPARATION

Heat Fixing

Methanol Fixing

STAIN PROCEDURE

MICROSCOPIC EVALUATION

* Excessive rinsing in these steps could result in the loss of dye in the gram-positive cell walls.

** Alternatively, basic fuchsin can be used as the counterstain for weakly staining gram-negative organisms.

INTERPRETATION OF RESULTS

If the gram stain procedure has been performed properly and the reagents are fresh, the Staphylococcus aureus (ATCC ® 25923) in the positive control well should appear as a purple to lavender (gram-positive) cocci. The negative control, Escherichia coli (ATCC ® 25922) should appear as a pink to red (gram-negative) rod.

LIMITATIONS OF THE PROCEDURE

Cultures should be 18-24 hours old for gram staining procedures.

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological equipment such as microscopes, inoculating loops, incinerators, gram stain reagents, methanol, etc., are not provided.

QUALITY CONTROL

Appearance of the positive and negative wells when stained according to standard gram stain procedures:

Test Organisms Reaction
Positive well:
Staphylococcus aureus
ATCC ® 25923
Gram-positive (blue/purple) cocci in pairs or clusters
Negative well:
Escherichia coli
ATCC ® 25922
Gram-negative (pink/red) bacilli

PHYSICAL APPEARANCE

Q-Slide™ Gram control slide should have a methanol fixed smear of Staphylococcus aureus in the positive control well and Escherichia coli in the negative control well.

Q-Slide™ Gram

Q-Slide™ Gram (Cat. no. Z302). Showing the two known QC circles and four test specimen squares.

REFERENCES

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

2. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

ATCC is a registered trademark of the American Type Culture Collection.

040416gr