Microbiology: Procedures that lead to microbe identification

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Microbiology: Procedures that lead to microbe identification by Mind Map: Microbiology: Procedures that lead to microbe identification

1. What are we looking for?

1.1. The microbe (Microscope)

1.2. Components of the microbe

1.3. Patient antibodies to the microbe

2. What are we testing?

2.1. Patient Sample

2.1.1. Blood

2.1.2. Urine

2.1.3. Tissue

2.1.4. CSF

2.1.5. And so and so forth...

3. How do we look?

3.1. Culture

3.1.1. Blood Agar Beta-Hemolysis (total lysis) Alpha-Hemolysis (incomplete lysis) Gamma-Hemolysis (no lysis)

3.1.2. Special Specific Agar Chocolate Agar (lysed RBC) Standard Version used for Haemophilus spp and Neisseria spp Thayer-Martin or New York City agars are Chocolate Agar with antibiotics to prevent the growth of competing normal flora Regan-Lowe (Charcoal Blood) Agar Used for the culture of Bordetella pertussis (causes whooping cough) Thiosulfate-citrate-bile salts-sucrose (TCBS) Agar Alkaline media for Vibrio cholerae (Buffered) charcoal-yeast extract (BCYE) Agar Used to grow Legionella Lowenstein-Jensen (L-J) Agar Used to grow mycobacterium

3.2. Microscopy

3.2.1. Gram Stain Positive Negative

3.2.2. Acid-fast Stain Positive Mycobacterium, Nocardia (partial staining), and oocytes of Cryposporidium, Cyclospora and Ispora Negative

3.2.3. Wet Mounts Used for urine sample - assess motility and shape

3.2.4. Dark Field Microscopy Useful for spirochetes (eg syphilis) too thin to be seen by Gram stain or wet-mount light microscopy

3.2.5. Fluorescent Microscopy Auramine-Rhodamine Dyes Bind non-specifically to waxy cell wall of Mycobacterium and Nocardia Antibody Staining Fluorophore attached to antibody binds (directly or indirectly) to antigen.

3.2.6. Electron Microscopy

3.3. Detection of microbial products

3.3.1. Antigen detection Enzyme-linked Immunoassay (ELISA) Fluorescent Microscopy

3.3.2. Enzyme or Toxin Activity Nagler Test Test for Clostridium perfringens alpha-toxin (a lecithinase) One Major Carbohydrate Substrate Growth in broths with only one carbohydrate MacConkey Agar Specific substrates Used in automated identification systems Rapid enzyme tests Catalase Oxidase (Cytochrome C oxidase) Nitrate reductase (Urine dipstick tests) Growth under specific conditions Used to identify certain metabolic features (Eg aerobe or anaerobe)

3.3.3. Nucleic Acid Detection Application of gene probes to microbes

3.4. Detection of immune response to microbe

3.4.1. Detection of patient antibodies - Ab levels are quanified IgM usually shows recent infection IgG usually shows older infection or exposure

3.4.2. A positive skin test Eg Mantoux test for TB