Gram stain is used primarily as a differential stain for bacteria, although it will also stain most fungi (especially yeasts) and some parasites, such as Strongyloides. The Gram stain procedure is commonly performed on: a) direct smears of clinical specimens, and b) smears made from culture growth.
This course will focus on Gram-stained direct smears.
What is a direct smear?
A direct smear is made using the actual clinical specimen, properly applied to a frosted-end glass slide.
What is the value of a direct smear? A direct smear made from a clinical specimen may be used to:
- Judge the quality of the specimen.
- Provide the clinician with same-day information regarding possible pathogenic organisms, pending results of culture and sensitivity.
- Contribute to the selection of culture media, especially in the presence of mixed flora.
- Provide internal quality control when direct smear results are compared to culture results.
