Unknown project (microbiology)
BIOL 2420 Identification of Staphylococcus species
Lab Objectives
Learn how to collect clinical specimens
Watch videos in lab exercise
Learn major characteristics of Staph species
What are characteristics of a pathogenic species?
To learn how biochemical tests can help determine species
Identification of Staphylococcus
Family Micrococcaceae
Gram +, cocci, facultative anaerobe
Microbiota of the skin and nasal cavity
5 potentially pathogenic species
Produce a variety of virulence factors: toxins, coagulase, and hydrolytic enzymes
S aureus
S epidermidis
S haemolyticus
Goal is to distinguish between them
Through a series of tests
Selective and differential media
Gram staining
Catalase tests, Dnase, hemolysis, coagulase, antibiotic testing
S hominis
S saprophyticus
Faculty.ccbcm.edu
Identification of Staphylococcus
Mannitol Salt Agar (MSA)
Halotolerance
Fermentation of mannitol
Indicator: phenol red
pH indicator that turns yellow in the presence of acid
No fermenationn: pink
Fermentation: yellow
Identification of Staphylococcus
Columbia nalidixic acid agar (CNA)
Inhibition of G- growth
Naladixic acid (antibiotic)
Hemolysis
All Staphylococcus are either beta- or gamma-hemolytic
Beta-hemolysis – complete lysis of the red blood cell
Due to the alpha toxin
Gamma-hemolysis – no lysis
Novobiocin sensitivity (>17mm)
Sensitive: S. aureus or S. epidermidis
Resistant: S. saprophyticus
Identification of Staphylococcus
Perform a Gram stain
What should the result be?
To help ensure that only Staphylococcus were grown…
Mannitol Salt Agar (MSA)
Only haloduric will thrive
Perform a catalase test
All Staphylococci are positive
Make sure yours falls into this category
Catalase test
Enzyme that breaks down hydrogen peroxide to water and bubbles (oxygen)
Identification of Staphylococcus
SM110
Nutrients and vitamins enhance pigmentation of pathogenic Staphylococcus
Light yellow-orange to golden color
Non-pathogenic Staphylococcus will be white/beige
High Salt
Identification of Staphylococcus
Dnase (deoxyribonuclease)
Exoenzyme that breaks down DNA into smaller molecules
Methyl Green Dnase agar
DNA binds to the methyl green
Hydrolyzed DNA releases from the methyl green to remove any green color
Identification of Staphylococcus
Coagulase test
Exoenzyme – causes clotting of the plasma
Virulence factor for staphylococci
Allows the bacteria to hide from the immune system
Protective against phagocytosis
Good indicator of pathogenic potential