Gram Stain Testing
Gram staining is a foundational technique used for the preliminary identification of bacteria by differentiating between Gram-positive and Gram-negative organisms based on their cell wall properties. It provides rapid, visual clues to bacterial identity and guides further microbiological analysis.
How It Works
- Crystal Violet – stains all cells purple.
- Iodine – forms a dye-mordant complex.
- Alcohol/Acetone – decolorizes Gram-negative cells.
- Safranin – counterstains decolorized cells pink/red.
What It Does
The Gram stain classifies bacteria into two major groups:
- Gram-positive: Appear purple or blue under the microscope due to a thick peptidoglycan layer that retains the crystal violet stain.
- Gram-negative: Appear pink or red because their thinner peptidoglycan layer and outer membrane allow the stain to wash out and take up the counterstain (safranin).
Applications
- Preliminary identification of bacteria before culture or molecular diagnostics
- Food spoilage analysis to identify microbial causes of shelf-life issues
- Environmental and hygiene monitoring in food production and healthcare settings
- Quality control in fermentation and dairy processes where specific microbial flora must be maintained
- Clinical microbiology to guide empirical treatment decisions
Why It Matters
- Gram staining provides quick, visual insight into bacterial identity and structure, helping labs prioritize further testing like culture, biochemical assays, or PCR.
Standards & References
- ISO 7218 – General guidance for microbiological examination
- FDA BAM – Gram stain protocols for foodborne pathogens
- CLSI M100 – Clinical interpretation and quality control
Leading food testing laboratory ensuring safety and quality in the food industry.
Contact Us
9341 E.Childs Ave., Planada, CA 95365, USA.
operations@fsa-lab.com
info@fsa-lab.com
support@fsa-lab.com
Office 1 : (209) 877 8728 Office 2 : (209) 877 8729