Phenotypic Methods- Dr Becker Flashcards
What are phenotypic characteristics?
Observable characteristics of microorganisms
True or False: A virus can be seen on light microscope
False
Disadvantages of microscope identification
- Mild/ chronic infection may not be detected
- Not all specimens can be used (Ex: fecal sample)
Advantages of microscope identification
- Determines cell/tissue morphology
- Cellular ass. of pathogens
- Impression of disease stage and severity
- Rapid and immediate analysis
Concentration technique
Used for parasite diagnosis
Ex: Feces, Vomit, Sputum
Flotation, Sedimentation, and Baermann test for larval identification
Baermann test
Conc. Technique
Uses a funnel to test larval identification
Warm water stimulates larvae
Method to extract nematode larvae from poop
Ex: lungworm larvae
McMaster egg counting slide
Determines egg types and level of infection (eggs per gram of feces)
Simple stain
uses 1 dye
Disadvantage: may not stain all components, difficult interpretation
Differential stain
uses more than 1 dye
more precise
Disadvantage: multistep, more time + reagents
Positive simple stain vs negative simple stain
Positive: stains cell
Negative: background is stained, cell structure is clear
H & E stain
detection of viral inclusion bodies
aggregates of proteins, represents site of viral replication
Hematoxylin
Basic stain, stains acidic components like nuclei
appears purple
Eosin
Acidic stain, stains basic components like cytoplasm and muscle and red blood cells
appears pink
Romanowsky stain
Diff quick stain
Histological staining for rapid staining
Modified Wright-Giemsa stain, studies pathogenic bacteria to cells
Gram stain
Differentiates gram + and gram - bacteria, targets peptidoglycans
Gram + is purple
Gram - is pink
Acid fast stain
Stains organisms w impenetrable cell wall
Ex: Mycobacterium, Cryptosporidium
Capsule Stain
negative staining technique
uses nigrosine or congo red
Stained cells but unstained capsule
Ex: Bacillus anthracis, Klebsiella, Clostridium
Flagella Stain
flagella are thickened with mordant
Endospore stain
spores are dyed by heating malachite green
Fungal and parasite stains
- Lactophenol Cotton Blue Stain
- Gomori Methenamine Silver
- Periodic acid Schiff
- Wheatleys Trichome stain
Lactophenol Cotton Blue stain
cotton blue stains chitin in cell wall of fungi
fungal stain
Drawbacks of culture methods
Time consuming
Expensive
Unculturable bacteria
What does culturing allow?
Identification
Assessment of AMR
Ability of microbe to cause disease
In depth studies of microbial characteristics and genetics
Fastidious bacteria
requires specific nutrients and culture conditions
Culture broth
Nutrient broth
Enrichment broth: increases number of specific bacteria, enhances growth
Bacterial colony
Visable mass of bacteria originating from single mother cell
Basic nutrient media
Ex:
Trypticase Soy Agar (TSA)
Luria Bertani agar
Mueller-Hinton agar
Enriched nutrient media
Ex:
Blood agar
Brain heart infusion agar
Chocolate agar
Lysed blood agar
Selective nutrient media for Gram +
Phenylethyl alcohol agar (PEA)
Selective for fungi
Sabouraud Dextrose Agar (SDA)
Selective for gram neg organisms
Eosin Methylene Blue Agar (EMB)
Types of differential media
Blood agar- hemolysis
MacConkey Agar
Mannitol Salt Agar
CLED agar for urinary bacteriology
MacConkey Agar
differential media
Selective for gram negative
Lactose fermentation- if lactic acid forms plate will show PINK colonies
Mannitol Salt Agar
differential media
Selects for gram +
If mannitol is fermented it will show YELLOW colonies of growth
CLED agar
Differential media
Tests for urinary bacteria
Lactose fermentation shows YELLOW color change
Which stain, stains the chitin in the cell wall of fungi?
Lactophenol cotton blue
Trytophanase
Enzyme production
Ability to convert tryptophane to INDOLE
What stain is used to detect viral inclusion bodies?
H & E stain
