Differentiate aerobic, Gram-negative and Gram-positive rods or coccobacilli with Gram-Sure Disks.

• Ready to use - Reagent-impregnated disk. No further prepartion is necessary.
• Rapid test - Incubate at room temperature for 5-10 minutes.
• Easy to interpret - Gram-negative organisms (blue fluorescence under longwave ultraviolet light) are easy to differentiate from Gram-positive organisms (no fluorescence under longwave ultraviolet light).

The cell walls of Gram-negative organisms contain aminopeptidase, which is detected by hydrolysis of L-alanine-7-amido-4-methylcoumarin from a non-fluorescent substrate to a fluorescent compound. In 1976, Cerney reported using L-alanine-4-nitroanilide to detect cell-wall aminopeptidase, which correlated with Gram negativity¹. In 1990, Manafi and Kneifel evaluated various chromogenic and fluorogenic substrates for the ability to differentiate Gram-positive and Gram-negative bacteria². They recommended using the fluorogenic substrate L-alanine-7-amido-4-methylcoumarin due to its higher test sensitivity and pronounced blue fluorescence indicating a positive reaction.

Gram-Sure disk contains the reactive ingredient L-alanine-7-amido-4-methylcoumarin which exhibits pronounced blue fluorescence and increased test sensitivity. Aerobic, Gram-negative rods and coccobacilli show a bright blue fluorescence, whereas Gram-positive rods and coccobacilli do not display any fluorescence.

This test is used to serve as an adjunct to the traditional Gram stain method and not a replacement.