otitis media/ externa (wk 5) Flashcards
stages of acute otitis media
stage of hyperemia
stage of exudation
stage of suppuration
stage of coalescence
stage of complication
suppurative complications of acute otitis media
acute mastroidits
meningitis
brain abscesses
otitis media with effusion
chronic suppurative otitis media
causes of otitis media
socioeconomic status, education, smoking, no breastfeed, hyrgeine, virual URTI, males, family history etc
Eustachian tube in infant vs adult
more otitis media in infant because tube is shorter and more horizontal
common otopathogens for otitis media
streptococcus pneumoniae
haemophilus infleunzae
mortadella catarrhalis
psuedomonas aeruginosa
H inflenza factors?
chocolate agar
X factor (hemin)
v factor (NAD+)
h influenza virulence factors
Adhesins
Polysaccharide capsule
Lipid A chains/lipooligosaccharides Fimbriae
IgA protease
Biofilms
moraxella catarrhalis
Gram –ve, diplococcus, aerobic bacteria
Common for URT, middle ear, eye infections
Commonly resistant to beta lactam drugs
Part of normal microbiota of ~3% of people. (children more)
moraxella catarrhalis
Antiobiotic resistance (b-lactamase resistance)
Outer Membrane Proteins
- uspA1-A2, Pili
Iron-Regulated Proteins
- Transferrin-Binding proteins
- Lactoferrin-binding proteins
Lipid A chains/lipooligosaccharides
streptococcus pneumonia virulence factors
Polysaccharide capsule
Fimbriae
Surface proteins that inhibit activation of complement
what causes otitis externa
pseudomonas aeruginosa and staphylococcus aureus
pseudomonas aeruginosa
an opportunistic pathogen that becomes an infectious agent following the burning away of skin; can also cause otitis externa
pseudomonas aeruginosa virulence factors
Fimbriae and adhesins to improve attachment
Formation of biofilms
Produce enzymes like elastase, which breaks down elastic fibres, degrades complement system, cleaves IgG and IgA antibodies
Pyocyanin with triggers free radical accumulation (this is what causes tissue damage)
pseudomonas aeruginosa where is it found?
soil
P. aeruginosa is found mostly in soil; not a component of regular microbiota
Cannot penetrate epidermal layer independently – good news!
Common nosocomial infection agent (10% of hospital infections)
staphylococcus aureus
Salt tolerant, facultative anaerobe, resistant to dessication, UV radiation and heat
Along with Staphylococcus epidermidis, make up ~90% of microbiota of skin.
Common cause of otitis externa
what are the enzymes in staphylococcus aureus that are virulence factors
coagulase, hylauronidase, staphylokinase, lipase, beta lactamase
what does the virulence factor hylauronidase and collagenase in staphylococcus aureus do>
breaks down junctions and enters into epithelial cells
what does the virulence factor coagulase and kinase in staphylococcus aureus do>
coagulase forms clots and staphylokinase then dissolve the clot and releases bacteria
clot forms to avoid detection from immune system then spread systemically
what does the virulence factor beta lactamase in staphylococcus aureus do>
breaks down beta lactamase i.e. penicillin
what are the structural defesnes in staphylococcus aureus that are virulence factors
capsule/ slime layer glycocalx
binding IgG antibody stem regions
what does the virulence factor of binding IgG antibody stem regions in staphylococcus aureus do>
inhibits antibody binding to FC receptor of phagocytes
prevent opsonization
what does the virulence factor of capsule/ slime layer glycocalx in staphylococcus aureus do>
blocks phagocytosis
what are the toxins that are virulence factors in staphylococcus aureus?
Cytolytic toxins to disrupt membranes of a large number of cell types
Leukocydin – kills leukocytes (another means of avoiding phagocytosis)
Epidermal Cell Differentiation Inhibitors – produces large holes in the lining of blood vessels
Exfoliative toxins (Toxic Shock Syndrome Toxin)
what are other diseases outside of otitis externa that are causes by staphylococcus aureus
skin disease: folliculitis, sty, furuncle, carbuncle, staphylococcal scalded skin syndrome, impetigo
reproductive: stpahylococcal toxic shock syndrome
cardivovascualr/ systemic: endocarditis, bacteremia
respiratory: penumonia
GI: food poison
