Section 2 GRAM POSITIVE COCCI Flashcards
What are the leading cause of infections?
Staphylococci
Where are Staphylococci found?
Part of normal flora
What do the Staphylococci on the skin do?
- Function as competitors to prevent pathogens from colonizing skin
- Produce antimicrobial substances that are active against other G+
Is the normal flora in the GI in higher number in the upper or lower intestine?
In higher numbers in lower intestine, due to flushing of gastric juices through
upper intestine
Which exotoxin is the most potent membrane damaging toxin?
Alpha (α) toxin
Which toxin is a sphingomyelinase which damages membranes rich in lipids?
Beta (β) toxin
Which toxin lyses erythrocytes (RBCs)
Gamma toxin (γ)
Which exotoxin destroys leukocytes (WBCs)
Leukocidins
*Causes release and rupture of lysosomes (contain hydrolytic enzymes) resulting in further tissue damage
What is a Toxic Shock Syndrome Toxin (TSST) and what does it do?
A superantigen causing massive release of cytokines which cause a drop in blood pressure and kidney failure
- Powerful exotoxin that stimulates tumor necrosis factor (TNF) leading to necrosis
- Also stimulates interleukin leading to fever, rash
- Originally associated with tampon use, also affects men and non-menstruating women
What is the name for Exotoxins that destroy material the binds together the layers of skin?
Exfoliatin
Which toxin is being described?
“Unlike most exotoxins S. aureus enterotoxin is heat-stable, cooking food will not destroy it
-If present in food when consumed causes nausea and vomiting”
Enterotoxin
Which extracellular enzyme breaks down proteoglycans in connective tissue?
Hyaluronidase
What is the extracellular enzyme that converts hydrogen peroxide to oxygen and water?
Catalase
Which extracellular enzyme reacts with prothrombin in blood resulting in
staphylothrombin causing blood to clot?
Coagulase
Which extracellular enzyme lyses clots?
Fibrinolysin
What are the characteristics of Staphylococcus aureus?
*Mannitol fermentation = Golden pigment
(only staph aureus can ferment mannitol)
*Coagulase positive
What are some of the pathogenesis of Staphylococcus aureus?
Osteomyelitis (bone infection) Toxic shock syndrome Wound infections Enteritis Catheter and shunt infections Furuncles and carbuncles Impetigo Folliculitis Scalded skin syndrome
What type of Staphylococcus aureus occurs following a long course of antibiotics or following surgery?
MRSA (methicillin resistant S. aureus
Are staph epidermidis and staph saprolyticus coagulase positive or negative?
Negative
Which type of staphylococcus is a leading cause of UTI’s?
Staph saprolyticus
What are the differences/similarities in Staphylococcus sp. and Streptococcus sp. as far as lab diagnosis?
Both are Gram positive cocci
- Catalase test
- Staphylococcus sp. is positive
- Streptococcus sp. is negative
Are Streptococci gram positive or negative?
What is streptococci’s shape?
Are they motile or non-motile
Are they endospore or non-endospore forming?
Gram positive
Spherical shape - cocci
Non-motile
Non-endospore forming
What are used to type Streptococci?
Hemolysins
Which hemolysin (used to classify streptococci) is a partial hemolysis with greenish cast around colonies?
α-hemolysis
Which hemolysin (used to classify streptococci) is a complete lysis of blood cells creating clear area around colonies?
β-hemolysis
Which hemolysin (used to classify streptococci) has no lysis of blood cells?
γ-hemolysis
Which serological testing proposed by Rebecca Lancefield for establishing classification of streptococci includes Enterococcus faecalis, abscess, UTI, endocarditis?
Group D
Which serological testing proposed by Rebecca Lancefield for establishing classification of streptococci are found colonizing the female genital tract and can cause infection in newborn, neonatal sepsis, and meningitis?
Group B
