Prunuske -- Otitis Media Flashcards Preview

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Flashcards in Prunuske -- Otitis Media Deck (22):
1

Otitis externa

external otic canal infection

2

Otitis media

middle ear canal infection

3

Labrinthitis

inner ear infection

4

Mastoiditis

mastoid bone infection

5

Otitis media with effusion

build up of fluid in Eustachian tube 

6

Acute otitis media

bacterial or viral

  pain, red ear drum, pus, and fever

~70% of children experience at least 1 episode of otitis media during childhood probably b/c tubes are more narrow and horizontal and 1/3 have had 3 or more episodes

More common in males and Native American/Alaskan Natives

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Common etiologic agents of acute otitis media

Streptococcus pneumoniae: 25-50%
Haemophilus influenzae (mostly non-typable): 15-30%
Moraxella catarrhalis: 3-20%
Viral (especially RSV, rhinovirus): 5-22%
No pathogen identified: 16-25%

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Streptococcus pneumoniae

Gram positive, diplococcus

Resistance due to changes in the penicillin binding protein

Capsule- blocks phagocytosis by interfering with the
deposition of complement  on surface of organism

Choline-binding proteins- bind carbohydrates present
on surface of epithelial cells 

Neuraminidases- cleave sialic acid in host mucins 

Autolysin A (LytA)- degrades peptidoglycan and causes
α-hemolysis during growth

Pneumolysin- pore forming toxin is released disrupts cilia 

  • Transmitted by contact with secretions
  • Asymptomatic colonization of naso oropharynx
  • Can be a carrier for weeks to months especially in winter
  • If spreads to middle ear or terminal airways leads to rapid inflammation

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These illnesses are common, often occur together, and caused by similar agents...

Bacterial conjunctivitis, otitis media, and sinusitis 

10

Recurrent otitis media is associated with...

conductive hearing loss as well as meningitis and mastoiditis

11

Acute otitis media is treated with ________ but patients need to be monitored for treatment failure as there is an increasing number of drug resistant strains and physicians need to minimize selection for these strains by practicing appropriate writing of prescriptions.

amoxicillin

beta-lactam; binds PBP to block transpeptidation step 

12

Match the bacteria/virus with the description...

Red eye, mild cold, clear drainage

Adenovirus

13

Match the bacteria/virus with the description...

Visual field deficit most common in
HIV infected individuals

Cytomegalovirus

14

Match the bacteria/virus with the description...

Releases pneumolysin pore forming toxin

Streptococcus pneumoniae

15

Match the bacteria/virus with the description...

Green-yellow discharge from the eyes

Neisseria gonorrhea

16

Haemophilus influenzae

Small, pleomorphic, gram-negative, coccobacillus, nonmotile, biofilms, facultative anaerobe

  • Humans are only known host
  • Fastidious require additional blood factors for growth hematin (X) and NAD (V) both present in chocolate agar
  • Nontypeable- nonencapsulated (NTHi) colonize nasopharynx in 80% of people and if spreads to the eustachian tubes causes otitis media. (vaccine available)
  • Many express β-lactamases
  • Other mucosal sites of infection include
    genital tract and conjunctivitis

17

Moraxella catarrhalis

Gram-negative, aerobic, diplococcus, oxidase-positive, nonmotile, fastidious-chocolate agar, pili

  • Colonization of upper respiratory track in infants
  • 95% of M. catarrhalis produce β-lactamases
  • Hockey puck test- easily slide across agar and be stacked

18

Recommended treatment for Acute Otitis Media

  • 6-24 months start empiric treatment:  Amoxicillin provides coverage against Streptococcus pneumoniae, Haemophilus influenzae with limited side effects (?).
  • If no improvement within 48 hours switch to Amoxicillin- Clavulanate 

19

For which organisms would you expect clavulanate to potentially expand coverage?

clavulanate is a beta-lactamase inhibitor

clavulanate is commonly used with beta-lactam drugs such as amoxicillin 

In this case it would improve coverage for organisms that have resistance through beta-lactamases... such as 

Moraxella catarrhalis
Haemophilus influenzae 

20

Otitis externa- common etiologies

Acute localized ?

Acute diffuse ?

Malignant ?

Fungal ?

  • Acute localized-  most often Staphylococcus; pustule or furuncle associated with hair follicles
  • Acute diffuse- Pseudomonas aeroginosa itches, red canal, and painful
  • Malignant- Pseudomonas aeroginosa, invasion of adjacent bone and cartilage which can progress to cranial nerve palsy and death.  More common in elderly, poorly controlled diabetes, and immunocompromised.
  • Fungal- Aspergillus and Candida

21

Staphylococcus aureus

general info and virulance factors

 clustered, Gram positive cocci 

Virulence factors

  • Capsule and Protein A binds Fc portion of IgG to interfere with phagocytosis
  • Coagulase binds prothrombin initiating the polymerization of fibrin and clotting- retard migration of phagocytes to site of infection
  • Membrane damaging toxins hemolysin and leukotoxin

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