Ear Infections

Question 1

Streptococcus pneumoniae

Answer 1

Ear Infx
• Gr+ coccus, pairs or short chains, ‘lancet-shaped’
• ‘pneumococcus’
o normal microbiota oro-nasopharynx
o mucosal opportunist
LAB
• *α-hemolytic
- *bile soluble
- *optochin susceptible 
• *Quellung reaction positive
Dx
• pneumonia, bacteremia, meningitis, sinusitis, conjunctivitis, *otitis media
o *serious dz mostly elderly, young
Virulence
- *polysaccharide capsule
• *IgA1 protease
• *pneumolysin
• *H2O2
• *phosphocholine in CW = C polysaccharide
Prevention
• Pneumovax
• Prevnar 13

Question 2

Haemophilus influenzae

Answer 2

Ear Infx
• Gr- coccobacillus
• human reservoir…normal microbiota URT
• *nontypeable strains = unencapsulated
o normal microbiota URT unencapsulated, usually non-invasive
• facultative anaerobe
DX
o *mucosal infections (E.g. otitis media, sinusitis, conjunctivitis, pneumonia in elderly and indiv. w/ chronic lung disease)
LAB
- *needs X factor and V factor for growth
o *type b (Hib) strains
- Quellung reaction + 
Virulence
- capsule
• *LPS 
• pili
• IgA1 protease
• naturally competent for transformation
• *major virulence factor Hib is capsular type
o *polyribitol phosphate (PRP)

Question 3

Moraxella catarrhalis

Answer 3

Ear Infx
• Gr- diplococcus (paired end to end)
• human reservoir
o normal microbiota oro-nasopharynx children and elderly
o mucosal opportunist
• *aerobic
• *oxidase +
• *fastidious
DX
• infect. esp. *immunocompromised, children, elderly
o Causes sinusitis, otitis media, conjunctivitis, bronchitis, pneumonia 
Virulence (don't have to know!)
- *LPS
• pili, LOS, DNase, lipase

Question 4

Pseudomonas aeruginosa

Answer 4

Ear Infx
• Gr- rod
• *ubiquitous
• occasional normal microbiota skin, intest. (primarily hospitalized, immunocompromised)
o opportunist- wide range localized and systemic infect.
o *healthcare associated infect.
• *encapsulated
• *motile, flagella
• *aerobe
• *oxidase +
• *nonfermenter (non-lactose fermenter)
• *wide temp. range, 4-42°C
• salt-tolerant
• growth in distilled H20
DIAGNOSIS
o *mucoid colonies (from capsule)
o *+/- odor of grapes 
o *+/- color
   • *pyocyanin (blue) - stimulates IL-8 release → PMN attractant. 
   • *pyoverdin (green, fluorescent [wounds]) - siderophore
- *Quellung test +
Virulence
• pili
- *LPS
• *capsule (alginate!)
- *spreading factors
• *exotoxin A 
• *biofilm formation
• *intrinsic and acquired antibiotic resistance
• siderophores