SARA_GRAM_STAIN_PPT...........................

gramstain.gram possitive gram negative

1. Gram Staining By Dr.Sara (PG 1’st Year) SIMS

2. Interpretation of Result (Contd..)

3. Interpretation of Result (Contd..)

4. Gram Positive Bacteria Stain dark purple with crystal violet (or methyl violet) and are not decolorized by acetone or ethanol. Examples include species of: Staphylococcus Streptococcus Clostridium Corynebacterium Actinomyces

5. Gram Negative Bacteria Stain red because after being stained with crystal violet (or methyl violet) they are decolorized by acetone or ethanol and take up the red counterstain (e.g. neutral red, safranin, or dilute carbol fuchsin). Examples include species of: Neisseria Klebsiella Haemophilus Brucella Salmonella Yersinia Shigella Coliforms Vibrio

6. Modifications of Gram’s Stain

7. Quality Control Check

8. Gram Variability Gram Positive organism may lose their ability to retain crystal Violet and stain gram negatively for the following reason :- Cell wall damage due to antibiotic therapy or excessive heat-fixation of the smear, over-decolorization of the smear. Use of an iodine solution which is too old, i.e., yellow instead of brown in colour (always store in a brown glass or other light opaque container). Smear has been prepared from an old culture. Gram negative organisms may not be fully decolorized and appear as Gram positive when a smear

9. Bacterial L forms L-forms of bacteria are artificial cell wall-less organisms (means they are different from Mycoplasma) first found by the Lister institute in 1935. Can be produced from normal bacteria by damaging the cell wall (by Penicillin, salt solutions, antisera etc.). L-form cells are difficult to cultivate and usually require a medium with a right osmotic strength. They can reconvert to wild type. Rarely they can develop to stable L-forms. May cause chronic infections which are relatively resistant to antibiotic treatment and difficulty to detectable using routing serological diagnosis methods, because the target sites of some antibiotics (penicillin) and somatic antigens (O antigen) are absent.

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