Gram Stain Test
680 Kshs | Home Collection Available
Synonyms
Gram’s method, Gram’s procedure
Purpose
Laboratory professionals use the Gram Stain Test to detect and classify bacteria in samples collected from suspected infection sites such as the throat, lungs, genitals, or skin wounds. It helps differentiate bacteria into two major categories: Gram-positive and Gram-negative, based on their cell wall structure and how they respond to the Gram staining process.
Clinicians use this test to guide early treatment decisions, especially in serious infections that require timely antibiotic intervention. By identifying whether Gram-positive or Gram-negative bacteria cause the infection, clinicians can choose the most effective antibiotic therapy.
Other tests that are commonly performed alongside a Gram stain include Bacterial culture, Complete Blood Count (CBC), Polymerase Chain Reaction (PCR), and Blood culture.
Patient Preparation
Special preparations are not required.
Samples
Collect glass slide smear material from the infected area on a clean glass slide using a sterile swab. Gently roll the swab onto the slide to make a thin smear, and air dry the slide. Maintained at room temperature.
Reference Range
Negative/Normal gram stain.
Results Turnaround
1 – 2days after receipt of samples.
Diseases / Diagnostic indicators
The Gram Stain Test helps detect the presence of bacteria and guides the identification of the infection type based on how the bacteria respond to the stain:
Positive Result:
Gram-positive bacteria appear purple under the microscope.
These are commonly associated with infections like:
- Strep throat (Streptococcus pyogenes)
- Pneumonia (Streptococcus pneumoniae)
- Skin infections (Staphylococcus aureus)
- Gram-negative bacteria appear pink/red
These are often linked to:
- Urinary tract infections (Escherichia coli)
- Gonorrhea (Neisseria gonorrhoeae)
- Meningitis (Neisseria meningitidis)
Negative or Inconclusive Result:
May indicate:
- Poor sample quality or low bacterial load
- No bacterial infection
- Presence of other organisms (e.g., fungi or viruses)
For more on Gram Stain Testing, read this study.