Is the Gram stain 100 accurate?
Is the Gram stain 100 accurate?
Gram’s stain examination is recommended for all patients suspected of having meningitis as it is fast, inexpensive, and fairly reliable. Various reports of Gram’s stain sensitivity suggest a range from 50% to 90%. The specificity approaches 100% (Durand et al., 1993; van de Beek et al., 2004).
What is the most important step of Gram staining?
The thickness of the smear used in the Gram stain will affect the result of the stain. The step that is most crucial in effecting the outcome of the stain is the decolorizing step.
How do you read a Gram stain report?
A Gram stain is colored purple. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative.
How is Gram positive bacteria treated?
Most infections due to Gram-positive organisms can be treated with quite a small number of antibiotics. Penicillin, cloxacillin, and erythromycin should be enough to cover 90 per cent of Gram-positive infections.
Why do gram-positive and negative stain differently?
Gram-positive and Gram-negative bacteria stain differently because of fundamental differences in the structure of their cell walls. The bacterial cell wall serves to give the organism its size and shape as well as to prevent osmotic lysis. The material in the bacterial cell wall which confers rigidity is peptidoglycan.
What can cause a Gram positive bacteria to show up as a gram negative lab?
The Conditions When Gram Positive Bacteria Can Appear Gram Negative. When over-decolourized by either prolonged exposure to decolourizer or using acetone alone. When cell wall gets damaged by exposure to lysozyme or cell wall acting antibiotics such as Penicillin.
What does a control Gram stain look like?
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.