Skin Flashcards
Stain, shape, motility, metabolism of Staph
gram positive
cocci
nonmotile
facultative anaerobes
Where are staphlococci found in humans?
surface tissue, GI tract, especially anterior nares
What is the fxn of coagulase?
converts fibrinogen to fibrin
How do you differentiate Staph from Strep?
Staph are catalase positive
What is unique to Staph aureus
protein A
What does Protein A do?
binds Fc portion of IgG and the IgG can no longer contribute to opsonization and phagocytosis
How do the different diseases of S aureus come about?
different strains have different toxins
What are the toxins made by S aureus?
Hemolysins Leukotoxins Enterotoxins (superantigens) TSST Exfoliative toxins
What type of hemolysin are those of S aureus?
Beta hemolytic
What are the superantigens made by Staph aureus?
enterotoxins and TSST
What are exfoliative toxins?
Proteases that lyse intercellular connections between cells in the epidermis
How are Staphylococcus transmitted?
mostly by hand contact
Where are the primary sites of infection for Staphylococcus aureus
skin
What kinds of infection can Staphylococcus aureus cause?
folliculitis boil (subcutaneous) impetigo scalded skin syndrome pneumonia osteomyelitis arthritis
How do you treat S. aureus infections?
drain the wound
remove foreign objects
antibiotics
Where do S saprophyticus infections usually occur?
urinary tract
Stain, shape, metabolism of Streptococci
gram positive
cocci
facultative anaerobe (ferment carbs–lactic acid made)
How are Streptococci classified?
Lancefield typing based on cell wall carbohydrate antigen
Hemolytic abilities on blood agar (alpha is partial or green, beta is complete clearing, gamma is no clearing)
Biochemical properties
What is S agalactiae known for?
neonatal disease
What is S pyogenes known for?
pharyngitis, rheumatic fever, glomerulonephritis, tissue infections
What is S pneumoniae known for?
otitis media, pneumonia, sepsis, meningitis
What is S bovis known for?
bacteremia linked to GI cancer
What do Streptococcus pyogenes have?
Lanceefield Group A carb M proteins M-like surface proteins Lipotenichoic acid and F protein that help with adhering Hyaluronic acid capsule C5a peptidase
pathogenesis of strep pyogenes
avoids opsonization and phagocytosis (hyaluronic acid capsule
adheres to host cells (lipoteichoic acid, M proteins, F protein)
Invasion of host cells (M and F proteins)
Toxins and enzymes (exotoxins are superantigens)
What kinds of hemolysins does S pyogenes make?
Streptolysin S, Streptolysin O
Where is S pyogenes found?
transiently in oropharynx of healthy kids and adults
How can you tell that someone is protected from S pyogenes?
has antibodies to M protein
How is S pyogenes spread?
droplet transmission
What kind of clinical diseases do you see w Strep pyogenes?
pharyngitis Scarlet fever (pharyngitis and erythematous rash) impetigo/pyoderma erysipelas (skin and subcu) toxic shock endocarditis necrotizing fasciitis
Group A late sequalae
rheumatic fever-after respiratory infections(strep antigens cross react)
glomerulonephritis-after pharyngela or cutaneous infections
What confirms rheumatic fever or glomeurolonephritis?
antibodies to streptolysin O
Pathogenesis of strep agalactiae
Capsule
Where does strep agalactiae colonize?
lower GI tract and genitourinary tract-can be given to neonates
What kinds of diseases do strep agalactiae cause?
neonatal meningitis, pneumonia, sepsis
Sepsis in pregnant women
in older adults (bacteremia, pneumonia, bone and joints, skin and soft tissue)
Stain, shape, hemolysis of Strep penumonia
gram positive
coccus
alpha hemolytic
How do you ID strep pneumonia?
alpha hemolytic
polysaccharide capsule
phosphorylcholine and species specific teichoic acid cell wall
C polkysaccharide-binds C reactive protein
F antigen–reacts with Forssman surface antigen on human cells
Pathogenesis of strep pneumonia
mostly as a result of host response, not toxins
binds to oropharynx
releases toxic cell wall components (teichoic acids, peptidoglycan)
How does S penumonia infection come about?
S pneumonia transiently colonzes normal people
Can be aspirated in lower airway
linked to breakdown of natural defenses (epiglottal reflex, cough reflex)
Clinical diseases of strep pneumonia
pneumococcal pneumonia (blood in sputum, cough, chest pain, fever) Sinusitis and otitis media Meningitis Bacteremia Endocarditis
Prevention of streptococcus pneumonia
adults and children greater than 2=vaccine with 23 capsular polysaccharides
chemical test for s pneumoniae
optochin sensitive
chemical test for s pyogenes
bacitracin sensitive
Panton valentine leukocidin is associated with___
staph aureus, present in many MRSA infections
