Microbes of the Body: Gram-positive Cocci Flashcards
What is the rxn that Catalase catalyzes?
What does a positive catalase test look like? What does it mean?
- The formation of bubbles (O2) is evidence of catalase activity.
- Catalase is invariably present in aerobes and is also present in some facultative organisms.
List the genera below as catalase (+) or catalase (-)
- Streptococcus
- Staphylococcus
- Enterococcus.
List the genera below as catalase (+) or catalase (-)
- Streptococcus
- (-)
- Staphylococcus
- (+)
- Enterococcus.
- (-)
Define the following human blood clotting factors
- fibrinogen
- thrombin
- fibrin
Define the following human blood clotting factors
- fibrinogen
- a small, soluble circulating protein
- thrombin
- an enzyme that is part of the coagulation cascade in human blood
- fibrin
- the resultant insoluble network that can trap blood cells and form blood clots
How does Staphylococcus aureus protect itself from destruction by human immune cells?
- S. aureus can use its coagulase enzyme to mimic human thrombin and catalyze the conversion of fibrinogen to fibrin.
- This forms a clot that protects it from destruction by human immune cells.
How do hemolysins lyse cells?
- Hemolysins are extracellular enzymes that can be detected by their ability to lyse cells.
- These secreted toxins assemble into ring-shaped, hollow structures that insert into cell membranes and form pores that allow the cellular contents to leak out.
Describe the 3 types of hemolytic reactions can be observed on blood agar plates
- Alpha hemolysins
- partially lyse the red blood cells and reduce the hemoglobin to methemoglobin which produces a green zone around the colony.
- Beta hemolysins
- cause complete lysis of the red blood cells and there is a clearing of the hemoglobin around the colony.
- Gamma hemolysis
- a term used to designate no hemolysis or change in the red blood cells.
Is the genera Staphylococcus catalase (-)?
No, it is catalase (+).
Where do most people carry staphylococci?
Skin
Staphylococcus epidermiditis is considered a commensal. What does that term mean?
The little bitch freeloading bacteria benefits from living on our skin and we don’t get shit.
S. aureus sometimes can be pathogenic – for example, when introduced into parts of the body different from the skin, where it normally resides.
- What are common diseases that arise from this?
- S. aureus is associated with a wide variety of disease states, including impetigo, toxic shock syndrome and food poisoning.
What does MRSA stand for?
methicillin-resistant Staphylococcus aureus
Why is MRSA a problem?
- MRSA can be problematic, especially in hospitals, because infections cannot be treated with penicillin, methicillin, or other common drugs.
- MRSA is frequently transferred from non-carriers to carriers in hospitals, and immunocompromised patients are more likely to become ill from MRSA.
- Hospital-acquired infections are called nosocomial infections.
Is coagulase a virulence factor?
Yea, bitch
True or False
- The staphylococci S. aureus, S. epidermidis**, and S. saprophyticus all look different on a microscope slide, based on size.
- The staphylococci S. aureus, S. epidermidis , and S. saprophyticus all form clusters of cells.
True or False
- The staphylococci S. aureus, S. epidermidis**, and S. saprophyticus all look different on a microscope slide, based on size.
- FALSE: They all look identical, hence biochemical ID tests.
- The staphylococci S. aureus, S. epidermidis , and S. saprophyticus all form clusters of cells.
- True
True or False
Summary of characteristics of S. aureus
- Salt tolerant
- Cannot ferment mannitol
- Produces a toxin that performs α-hemolysis on blood agar plates
- Produces coagulase enzyme
True or False
Summary of characteristics of S. aureus
- Salt tolerant
- Cannot ferment mannitol
- False: Ferments mannitol to form acid
- Produces a toxin that performs α-hemolysis on blood agar plates
- False: Produces a toxin that performs β-hemolysis on blood agar plates
- Produces coagulase enzyme
True or False
The exotoxin that is responsible for α-hemolysis in S. aureus is called α-toxin.
False
The exotoxin that is responsible for β-hemolysis in S. aureus is called α-toxin.
Can S. epidermidis ferment mannitol?
nah
Does S. epidermidis produce coagulase?
Nah
Does S. epidermidis produce α-toxin?
Nah
Does the genera Streptococcus have halophiles?
nah
Where does Streptococci normally live in the body?
Streptococci are normal inhabitants of the human pharynx, mouth, and va jay jay.
Does the genus Streptococcus grow on MSA plates?
Nah
What are the pathogenic streptococci of medical importance?
S. pyogenes, S.* *agalactiae, and S. pneumoniae**.
What diseases arise from pathogenic streptococci?
Diseases include
- pneumonia
- scarlet fever
- rheumatic fever
- meningitis
- endocarditis
- pharyngitis
- erysipelas
- glomerulonephritis
What is the common cause of a sore throat?
- Blow Jobs
- Streptococcus pyogenes infection
True or False
- Streptococci cause both α-hemolysis and β-hemolysis on sheep’s blood agar plates
truuuuuuu
What are “viridans streptococci”? Where is this frequently found in the body?
- Streptococci causing alpha hemolysis (resulting in a greenish zone in sheep’s blood agar)
- These are frequently found in patients with dental caries.
- Dental caries is the scientific term for tooth decay or cavities.
What are Streptococcus toxins that are responsible for β-hemolysis called?
- Describe their types
Streptolysins
- Streptolysin O
- oxygen labile (destroyed by oxygen)
- Streptolysin S
- oxygen stable
Are streptolysins virulence factors?
YASSS
True or False
Even though they are strong pathogens, S. pyogenes and S. agalactiae cannot cause β-hemolysis.
False: They both cause β-hemolysis.
True or False
Enterococcus bacteria are catalase negative and usually facultative.
True
Is Enterococcus a halophile?
Yass
Can the genus Enterococcus also tolerate bile salts?
The genus Enterococcus also tolerates bile salts, which is to be expected from bacteria native to mammalian guts.
What is the Enterococcus species most commonly isolated from human infections?
E. faecalis and E. faecium
Enterococci were the first to develop what kind of antibiotic resistance?
Enterococci were the first to develop resistance to vancomycin, the antibiotic that is commonly used to combat penicillin-resistant Gram-positive bacteria.
- Vancomycin-resistant Enterocococcus is called VRE.
- ________(Streptococcus/Staphylococcus) is Gram-positive, catalase-positive cocci usually found singly or in clusters.
- ________(Streptococcus/Staphylococcus) is Gram-positive, catalase-negative cocci often found in chains.
- Staphylococcus is Gram-positive, catalase-positive cocci usually found singly or in clusters.
- Streptococcus is Gram-positive, catalase-negative cocci often found in chains.
