Microbiology
"RMT in the making! Invisible invaders. Dito natin kikilalanin ang mga micro-organisms!"
1. Gram Staining 🔬
The foundation of bacterial classification!
Gram Stain Steps
- Crystal Violet (Primary stain) - 1 min
- Gram's Iodine (Mordant) - 1 min
- Alcohol/Acetone (Decolorizer) - 10-30 sec
- Safranin (Counterstain) - 30-60 sec
Gram Positive (Purple)
- Thick peptidoglycan layer
- Retains crystal violet
- Ex: Staph, Strep, Clostridium
Gram Negative (Pink)
- Thin peptidoglycan, outer membrane
- Decolorized, takes safranin
- Ex: E. coli, Pseudomonas, Neisseria
2. Medically Important Bacteria 🦠
Gram Positive Cocci
- Staphylococcus aureus: Catalase+, Coagulase+, skin/wound infections
- Strep pyogenes: Group A, pharyngitis, rheumatic fever
- Strep pneumoniae: Lancet-shaped diplococci, pneumonia
Gram Negative Rods (Enterobacteriaceae)
- E. coli: UTI, diarrhea, indole+
- Klebsiella: Pneumonia, capsulated, mucoid
- Salmonella: Typhoid, non-lactose fermenter
Gram Negative Cocci
- Neisseria gonorrhoeae: Gonorrhea, intracellular diplococci
- Neisseria meningitidis: Meningitis, vaccine available
Special Organisms
- Mycobacterium TB: Acid-fast, Ziehl-Neelsen stain
- Pseudomonas: Green pigment, oxidase+, burns/CF
3. Culture Media Types 🧫
Selective Media
- MacConkey Agar: Gram negatives, lactose fermenters (pink)
- Mannitol Salt Agar: Staphylococci (S. aureus = yellow)
- Thayer-Martin: Neisseria species
Differential Media
- Blood Agar: Hemolysis patterns (alpha, beta, gamma)
- EMB Agar: E. coli = green metallic sheen
- XLD Agar: Salmonella/Shigella = red with black center
💡 Board Exam Tips - Microbiology
- ✓ Staphylococcus = Catalase positive, Streptococcus = Catalase negative
- ✓ Beta hemolysis = Complete (clear), Alpha = Partial (green), Gamma = None
- ✓ MacConkey: Pink = Lactose fermenter, Colorless = Non-lactose fermenter
Test Your Knowledge! 🧠
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