Otitis Media Flashcards
What is an infection ofthe external ear called? Middle ear? Inner ear?
otitis externa
otitis media
labrinthitis
Mastoiditis is when an ear infection spreads to the mastoid, mmost commonly with which type of ear infection?
otitis media
What are the two types of otitis media?
acute otitis media
otitis media with effusion
What causes the two types of otitis media?
acute = bacterial or viral infection directly in the middle ear
otitis media with effusion = a buildpu of fulid in the eustachiam tube without direct infection of the middle ear (can be from URI infection, cigarette smoke, or allergies)
Will antibiotics help with otitis media with effusion?
no - there’s no infection in the ear
Why are both acute otitis media and otitis media with effusion equally concerning in kids?
they both cause hearing loss and kids need to hear to learn to speak
Describe the pathogenesis of acute otitis media
- URI or allergic condition causes congestion of mucosa
- narrowin gnad obstruction of eustachian tubes prevents ventilaiton or drainage
- Secretions accumulate
- If pathogen is present in the area it can easily proliferate and cause infection
Why do adenoids increase likelihood of ototis media
if they’re enlarged they can increase eustachian tube blockage
Why do young children have such high prevalence of otitis media?
anatomically their tubes are more narrow and horizontal than adults
What gender is more likely to have otitis media?
What ethnicity>
males
native american/alaskan natives
What are the 3 most common bacteria causing acute otitis media?
streptococcus pneumoniae (25-50%)
Haemophilus influenzae (mostly non-typable - 15-30%)
Moraxella catarrhalis (3-20%)
Viral otitis media is slightly less common, but what are the two main viruses that can be responsible?
RSV
rhinovirus
Remind me the shape and characteristics of streptococcus pneumoniae…what reaction is used to determine serotype?
gram positive diplococcus in a lancet shape
quellung reaction to determine serotypes - there are 91
Of the 91 serotypes, how many does the vaccine cover?
23 - covers hte ones most likely to cause meningitis
How is stremtococcus pneumoniae spread and how does it lead to otitis media?
transmitted by contact with secretions
usually starts with asymptomatic colonization of thr nasooropharynx
pt can be a carrier for weeks to months
if it spreads to the middle ear or terminal airways it can lead to rapid inflmammation
What virulence factors does strep pneumo have?
capsule
choline binding proeins
neuraminidases
autolysin A
penumolysin
Iron aquisition PiaA
What do the choline binding proteins do?
they bind carbohydrates present on the surface of epitheliual cells and help with attachment
What does neuraminidase do for strep pneumo?
it cleaves sialic acid in the host mucins, destroying them
What does the Autolysin A do for strep pneumo?
it degrades peptidoglycan and causes lapha hemolysis during growth
What does the pneumonlysin do for strep pneumo?
iafter the autolysin degrades the peptidoglycan of the bacteria, pneumolysin is secreted and released
it’s a toxin that disrupts host cilia
What molecules facilitate iron acquisiion in strep pneumo>
PiaA - acquisition
PiuA - uptake
What are the characteristics of haemophilus influenzae?
small
pleomorphic coccobacillus
gram-negative
nonmotile
can make biofilms
facultative anaerobe
Since haemophilus influenzae is fastidious, what do you need to grow it on?
chocolate agar with additional hematin X and NAD V
How is the haemophilus influenzae that causes otitis media different from the kind thate causes meningitis?
the ear infection ones are nontypeable, meaning they don’t have a capusule while the ones in meningitis do have a capsule
Why are mos thaemphilus influenzae strains resistant to penicillin?
express beta-lactamases
What other mucosal sites of the body can haemophilus influenzae infect?
genital tract and conjuntiva of the eye
Would the HIB vaccine cover for h. flu otitis media?
no, because the kinds that cause otitis media don’t hvae a capsule
however, there is a nontypeable H influenzae protein D-conjugated vaccine available now
What are the characteristics of moraxella catarrhalis?
gram negative
aerobic
diplococcus
oxidase positive
nonmotile
fasticious - need to grow on chocolate agar
pili
WHat is the main concern with moraxella catarrhalis resistance/
95% of M catarrhalis produces beta lactamases
What additional test can you do on the culture to determine it it is moraxella catarrhalis?
the hocky puck test - the colony will slide across the agar easily
What are the two major diagnostic approaches for diagnosin otitis media? Do you typically do cultures/
penumatic otoscopy first to look at TM
tympanometry to detect fluid in the middle ear
typically don’t do gram stain, but if recurrent, then you can do tympanocentesis to drain fluid and get a sample for a stain
What antibiotics should you use to treat acute otitis media?
in a patient under 2 years old, start empiric treatment with amoxicillin which will cover for strep pneumoa nd haemophilu sinfluenzae
if they don’t improve in 2 days, switch to amoxicillin with clavulanate (ampicillin)
If the patient has a penicillin allergy, what antibiotic should you prescribe for acute otitis media?
azithromycin
What are some ways to reduce resistance by increases compliance?
reduce the number of doses per day and prescribe shorter treatment courses
OF the moraxella catarrhalis, haemophilus influenzae and streptococcus pneumoniae, which onces would adding clavulanate be effective against?
Moraxella and Haemophilus - their primary resistance is thorugh beta lactamases, which clavulanate inhibitis
Streptococcus not so much - it’s main resistance is thoruhg alteration of the penicillin binding proteins, so clavulanate won’t do anything
What do eustachian tubes do? WHat generally happens to the tube with time?
it’s a tube that’s placed through the TM - it will drain any fluid that’s behind the ear
the tubes tend to tall out on their own and the incision heals spontaneously
What are the three main complications of otitis media?
- conductive hearing loss resulting in delayed speech due to performation of tympanic membrane and erosion of ossicles
- cholesteatoma - cyst of epithelial cells
- spread of infection to matoid, inner ear, temporal bone, meninges, and brain
WHat are the symptoms of otitis externa?
unilateral inflammation of the ear canal
you get pain, itching, and purulent ear drainage
What are the risk factors for otitis externa? What season is it most common in?
trauma to the external ear like with a Q tip
foreign bodies
excssive moisture - so after swimming
middle ear infections that can spread outward
most common in summer because of the swimming issue
What host defense mechanism is usually protective against otitis externa?
the cerumen in the ear contains lysozyme and is slightly acidic, so it deters microbial growth
What bacteria causes acute localized otitis externa
what bacteria causes acute diffuse otitis externa
localized = staphylococcus
diffuse = pseudomonas
What is the huge concern with pseudomonas otitis externa?
it can turn to a malignant form
invasion of the adjacent bone and cartilage, leading to cranial nerve palsy and sometimes death
more ocmmon in elderly, immune compromise and poorly controlled diabetes
What two fungi can cause otitis externa?
aspergillus and candida
What are th characteristics of stphaylococcos aureus?
clustered, gram positive cocci
What are the virulence factors of straphylococcus?
capsule
protein A
coagulase
hemolysin and leukotoxin
What does the capsule and protein A do for staphylococcus?
they bind the Fc portion of IgG to interfere with phagocytosis
What does coagulase do for staphylococcus?
is binds to prothrombin, initiating the polymerization of fibrin
this causes clotting and retards the migration of phacotyes to the site of ifnection
What do hemolysin and leukotoxin do for staphylococcus?
they damage the host clel membrane
How do you manage otitis externa?
cleansin with topic solutions that have low pH to deter growth
do NOT flush unless tympanic membrane is intact
treat with NSAIDs and acetaminophen
topical antibiotics are usually sufficient - typically neomycin + polymyxin + hydrocortisone
