Notes on Human Body Flora and Lab Procedures
Human Body Flora Lab Notes
Normal Body Flora
- Diversity:
- Composed of a diverse group of organisms present on the human body.
- Approximately 10^14 bacteria per individual, which is about ten times more than the number of human cells.
- More than 200 species of microorganisms, including:
- Bacteria
- Yeast
- Fungi
- Protozoa
- Transient viruses
- Algae
- Characteristics:
- Normal body flora consists mainly of nonpathogenic microorganisms.
- There exists a balance between normal flora and opportunistic pathogens, which can cause disease under certain conditions.
Phenol Red Mannitol Salts Agar
- Overview:
- Medium that is both differential and selective for Staphylococci.
- Selectivity:
- High salt concentration inhibits growth of non-Staphylococci.
- Differentiation:
- Presence of phenol red and mannitol aids in distinguishing types of Staphylococci.
- Staphylococcus aureus:
- Ferments mannitol, leading to a yellow coloration around colonies.
- Staphylococcus epidermidis:
- Does not ferment mannitol, resulting in red agar remaining around colonies.
Blood Agar
- Overview:
- A differential medium due to the presence of hemoglobin (heme) in the agar.
- Categories of Hemolytic Microorganisms:
- Alpha Hemolysis:
- Oxidizes the pigment portion of red blood cells, forming a green, olive, or brown zone around colonies.
- Occurs due to the effects of peroxide waste on the pigmented portion of heme.
- Beta Hemolysis:
- Lysing of red blood cells leads to a clear zone around colonies (complete hemolysis).
- Often indicates the presence of pathogenic microorganisms.
- Gamma Hemolysis:
- No effect on red blood cells; no detectable change around the colonies.
Hemolysis Types
- Alpha Hemolysis:
- Results in discoloration due to partial oxidation of red blood cells.
- Beta Hemolysis:
- Complete lysis of red blood cells indicates pathogenic potential.
- Gamma Hemolysis:
- No evidence of hemolysis with no observable changes in the agar around the colonies.