Final: + Cocci Flashcards
(34 cards)
Staphylococcus characteristics (6)
- Over 30 species
- Found on the skin and mucous membranes of warm-blooded animals, including humans.
- Gram-positive cocci in grape-like clusters
- facultative anaerobes
- catalase positive
- able to withstand high salt concentrations, pH extremes, drying, and high temperatures
Staphylococcus aureus virulence factors (11)
- coagulase
- staphylokinase
- hyaluronidase
- nuclease
- lipase
- penicillinase
- hemolysins
- leukocidin
- enterotoxins
- exfoliative toxin
- toxic shock syndrome toxin
Coagulase in Staphylococcus aureus…
coagulates blood plasma, forming a fibrin layer around the bacteria, which protects it from phagocytosis.
Staphylokinase in Staphylococcus aureus…
activates plasminogen to plasmin, a protease that breaks down fibrin in blood clots, aiding in bacterial spread.
Hyaluronidase in Staphylococcus aureus…
breaks down hyaluronic acid, a substance that holds connective tissue together, enabling bacterial tissue invasion.
Nucleases in Staphylococcus aureus…
digests DNA and RNA, contributing to tissue invasion.
Lipase in Staphylococcus aureus…
allows the bacteria to colonize oily surfaces such as skin.
Penicillinase in Staphylococcus aureus…
destroys penicillins, contributing to antibiotic resistance.
Hemolysins in Staphylococcus aureus…
lyse red blood cells (RBCs), contributing to tissue damage and infection spread.
Leukocidin in Staphylococcus aureus…
lyses white blood cells (WBCs), impairing immune defense.
Enterotoxins in Staphylococcus aureus…
damage intestinal epithelial cells, causing secretory diarrhea and water/electrolyte loss.
Exfoliative toxin in Staphylococcus aureus…
causes the loss of the epidermal layer of the skin, leading to conditions like scalded skin syndrome.
Protein A in Staphylococcus aureus…
binds to antibodies (IgG), impairing immune response by inactivating them.
Toxic shock syndrome toxin in Staphylococcus aureus…
causes toxic shock syndrome, leading to fever, rash, vomiting, liver damage, and renal failure.
Cutaneous infections caused by Staphylococcus aureus: (4)
- furuncles (boils)
- carbuncles (clusters of boils)
- impetigo
- scalded skin syndrome
exfoliative toxin production
Systemic infections caused by Staphylococcus aureus: (6)
- bacteremia
- osteomyelitis
- endocarditis
- pneumonia
- meningitis
- infections of internal organs.
Staphylococcal food poisoning: (3 steps)
- can contaminate foods like custards and processed meats - produces heat-resistant enterotoxins
- leads to vomiting, diarrhea, and cramps within 2-6 hours.
Why is Staph and MRSA resistant:
How to treat Staph/MRSA?
- Staphylococcus aureus is resistant to penicillin (due to penicillinase production)
- S. aureus (MRSA) is Methicillin-resistant
- Vancomycin is often the drug of choice for resistant strains.
Coagulase-negative staphylococci: (2 kinds, what?)
- S. epidermidis
- S. saprophyticus
- opportunistic pathogens that can cause infections, particularly in immunocompromised individuals or following surgical procedures.
Streptococcus characteristics: (4)
- Gram-positive cocci
- Appear in chains
- Catalase-negative
- Classified based on cell wall carbohydrates and hemolysis patterns.
Streptococcus pyogenes characteristics: (2)
- Gram-positive cocci
- Causes pus-producing infections
(such as strep throat and skin infections)
Virulence factors of Streptococcus pyogenes: (8)
- Capsule
- Surface polysaccharides
- M protein
- Hemolysins
- Erythrogenic toxins
- Streptokinase
- Hyaluronidase
- Nucleases.
Capsule in Streptococcus pyogenes…
protects the bacteria from phagocytosis and aids in attachment to host cells.
M protein in Streptococcus pyogenes…
helps the bacteria resist phagocytosis and aids in adherence to host cells.
