export_upper respiratory pathogens i Flashcards
Components of the URT
Conjunctiva
Nasolacrimal ducts
Middle ear
Nose
Pharynx
Sinuses/nasal cavity
Larynx
Epiglottis
Where does bacteria end up in the URT
Trachea or terminal airway
Where do viruses end up in the URT
Terminal airway and alveoli
Potentially suspended in air
Sterile URT tissues
Mastoid air cells
Middle ear
Sinuses
Trachea
Bronchi and bronchioles
Alveoli
Describe the sterility of the conjunctiva
It’s supposed to be sterile, but because of its location it is exposed to many organisms
Colonization is really uncommon, so it’s still considered sterile
Normal flora of the nose
Staphylococcus epidermis
Staphylococcus aureus
Corynebacterium spp.
Clinical relevance of Staph. aureus
About 20% of people have this in the normal population
People in hospitals have a higher percentage
Staph. epidermis features
Gram positive cocci clusters
Facultative anaerobes
Staph. aureus features
Gram positive cocci clusters
Facultative anaerobes
Corynebacterium spp. features
Gram positive rod
Pleomorphic
Non-spore forming
Nasopharynx normal flora
Streptococcus
Moraxella catarrhalis
Bacteroides
Bacteria in the Strep. viridans group
S. mutans
S. mitis
S. milleri
S. salivarius
Strep. viridans features
Gram positive cocci chains
Moraxella catarrhalis features
Gram negative diploid-coccobacillus
Aerobic
Bacteroides features
Strict anaerobe
Only if someone’s anatomy allows for oxygen-free pockets
URT pathogens with seasonal association
Strep. pneumoniae
Haemophilus influenzae
Neisseria meningitides
Moraxella catarrhalis
What differentiates Strep. from Staph.?
Strep. is catalase negative
Strep. A
S. pyogenes
Beta-hemolytic
Strep. B
S. agalactiae
Beta-hemolytic
Strep. D
S. bovis
Not hemolytic
Enterococcus facaelis also included in this group, though it is no longer considered a Strep.
Which Strep. group is alpha-hemolytic?
S. pneumoniae
Streptococcal pharyngitis
Streptococcus pyogenes
Differentiated by beta-hemolysis
S. pyogenes components
M protein
Capsule
M protein
Essential for virulence
Antiphagocytic
80 serotypes, not cross protective
Capsule
Inhibits phagocytosis
Also a virulence factor, but not found in all strains
Streptococcal pyrogenic exotoxins
Found in S. pyogenes
Super Ags
SPE-A, B, C, etc. (9 total)
SPE effects on body
Fever
Rash
T-cell proliferation
B-cell suppression
SPE diseases
Scarlet fever
Toxic shock
Necrotizing fasciitis
Which SPE disease is associated with strep throat?
Scarlet fever
Blood agar
Used to culture bacteria
RBCs are placed in the agar, hardens into a plate
Typically use sheep RBCs
Clearing on the plate = hemolysis
Difficulty with rheumatic fever
Auto-Abs to Strep. pyogenes
Organisms are gone, can’t treat with antibiotics
Once affected by this, susceptibility lasts for a lifetime; next time you get infection, the auto-Abs are produced
Strep. pyogenes affect on the kidneys
Acute glomerulonephritis
Ag-Ab complexes lodged in glomeruli
Results in edema, HTN, hematuria, proteinuria, decreased serum complement levels
Diptheria
Deadly, toxin mediated disease
Mild sore throat, slight fever, high fatigue, malaise
Dramatic neck swelling
Whitish gray membrane
Diphtheria organism
Corynebacterium diphtheriae
Corynebacterium diphtheriae features
Gram positive, variable shape
Sessile, non-spore forming
Diphtheria exotoxin
Lysogenized by bacteriophage
Pathogenesis of diphtheria
Not invasive, toxins are absorbed into bloodstream
Gray-white membrane: clotted blood, epithelial cells, leukocyte infiltrate
How is the diphtheria toxin released?
Inactive form
A and B subunit
Diphtheria subunits
A - inactivates EF-2 to stop protein synthesis
B - binding to host
Where are the B subunit receptors in the body?
Heart
Kidneys
Nerve cells
