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Gram Stains
- 1. Gram stains Just a few to remember
- 2. Gram Stain Stain Procedure: – – – – Crystal violet – primary stain for 1 min/rinse Gram’s iodine – mordant for 1 min/rinse Acetone/Alcohol – decolorizer for 5 seconds Safranin – counterstain for 1 min/rinse – Gram negative (red) and Gram positive (blue) – Assess Gram reaction and morphology How to judge quality of a gram stain- are the polys blue? If so, slide is under-decolorized. – Are the polys washed out? If so, the slide is over-decolorized – Poor quality stains must be repeated
- 4. Staphylococcus Gram positive cocci in clusters Cells are very round and deeply stained 1-2 µm in size
- 5. Beta hemolytic Streptococcus • Gram positive cocci in long chains • Organisms are oval with variable staining with size range of 1 – 1.5µm
- 6. Streptococcus pneumoniae • Gram positive cocci in pairs • Cocci are lancet or bullet shaped /@ 1µm size • Sometimes can visualize a capsule (clearing around the cells)
- 7. Viridans Streptococcus • Gram positive cocci in short chains and pairs – cocci around 1 – 1.5 µm in size • Chains are not as long as Beta hemolytic Streptococcus
- 8. Enterococcus species • Gram positive cocci in short chains and pairs with size of @ 1.5 µm • Difficult to impossible to differentiate from viridans Streptococcus
- 9. Yeast – Candida species • Large Gram positive globules (@ 8 um) with buds • Sometimes hyphae can be seen
- 10. Cryptococcus neoformans Due to the capsule of C. neoformans the stain appears somewhat like a blob Size range from 8 – 12 µm • India ink can be used to visualize the capsule
- 11. Aspergillus species Gram stain Mycelial Fungi do not stain well with the gram stain
- 12. Bacillus species Gram positive rods – large , box car shaped, sometimes spores are visible – 1.2 X 4µ in size Sometimes they over-decolorize and appear Gram negative Over-decolorized – clear areas are spores
- 13. Listeria monocytogenes Gram positive rodshort rods, deeply stained – size 1.2 X 2.5µm
- 14. Diphtheroids (Corynebacteria)gram positive pleomorphic rods in Chinese letter forms 1.4 X 3 µm
- 15. Nocardia species Delicate Gram positive branching rods - faintly staining Nocardia stain red with modified acid fast stains
- 17. Lactobacillus species Gram positive thin and long rods that appear sometimes in chains
- 18. Clostridium species Gram positive rods with spores @1.2 X 4 µm - the spores can be located throughout the organism
- 19. Mycobacterium species do not stain well with gram stain due to the lipid in the cell wall Kinyoun stain – AFB positive
- 21. Enteric Gram negative rods Plump rectangular in shape @ 1.4 X 2.5 - 3µm
- 22. Pseudomonas thinner than the enteric rods @ 1 x 3 µm
- 23. Haemophilus influenza pleomorphic small faintly staining gram negative rods
- 24. Vibrio species curved or comma shaped gram negative rods
- 25. Fusobacterium delicate fusiforme shaped faintly staining gram negative rods
- 26. Campylobacter sea gull shaped faintly staining gram negative rods
- 27. Yersinia pestis Safety pin bipolar staining ---
- 28. Neisseria species Gram Negative Diplococci Kidney bean shaped in pairs
- 29. Fastidious Gram negative rods such as the HACEK group, Brucella, Bordetella Small cocco – bacilli rods
- 30. Legionella does not stain well with Gram stain Does stain with Carbol Fuchsin used as a counterstain – pleomorphic Gram negative rod
- 31. Human cells PMNs Epithelial cells Mononuclear cells Mononuclear cells