B3.054 Ear Infections Flashcards
how does primary otalgia present in an ear exam?
abnormal
discharge, tinnitus, hearing loss, vertigo
what structures of the ear have no pain fibers?
inner ear structures (cochlea, semicircular canals) cranial enervation
how does secondary otalgia present in an ear exam?
normal
referred pain due to sensation fibers from cranial and cervical nerves
common causes of primary otalgia
otitis media
otitis externa
foreign bodies
barotrauma (diving, air travel)
common causes of secondary otalgia
dental caries, periodontal abcesses pharyngitis, tonsillitis TMJ syndrome cervical spine arthritis idiopathic
less common causes of primary otalgia
malignant (necrotizing) otitis externa
Ramsay Hunt syndrome
viral myringitis
cellulitis/chondritis/pericondritis, polychondritis, trauma, mastoiditis
signs of otitis media
recent URTI
red/cloudy and immobile tympanic membrane
signs of otitis externa
swimmers ear
ear phone use
white discharge
signs of malignant (necrotizing) otitis externa
diabetes, elderly immunocompromised
painful, granulation tissue
signs of Ramsay Hunt syndrome
vesicular rash
vertigo, hearing loss, tinnitus
what is Ramsay Hunt syndrome
reactivated VZV spreading to facial nerves
paralysis and rash affecting ear and mouth
4 primary acute otitis media pathogens
S. pneumo
H. influenzae
M. catarrhalis
S. pyogenes
3 primary acute otitis externa pathogens
s. epidermidis
p. aeruginosa
s. aureus
classify the Haemophilus species
small, gram - rods/coccobacilli
non-motile, non-sporulating
aerobic or facultative anaerobes
colonize mucosal surfaces of humans and animals
Haemophilus nutrition requirements
complex X factor (hematin) V factor (NAD)
discuss the strains of H.influenzae
most commonly associated w human disease
6 capsular antigenic serotypes (a-f)
non-encapsulated (nontypeable) strains rarely cause invasive disease
most virulent strain of H. influenzae
Type b (Hib) >95% of invasive infections
how does Hib colonize the oropharynx?
fimbrae (adhesins) IgA protease (breaks down mucosal IgA)
what is the function of Hib LPS
impairment of ciliary function
damage to respiratory epithelium
how does Hib invade bloodstream?
polyribitol capsule (PRP) anti-PRP antibodies are protective
what other sites can Hib invade? how?
hematogenous spread: joints meninges CNS all using PRP
what is the Hib virulence factor for disseminated disease?
LPS (endotoxin)
discuss the Hib epidemiology
humans only host
transmission via resp droplets
mainly pediatric disease
what is the Hib 2nd gen conjugate vaccine made up of?
purified PRP conjugated to carrier proteins
combo vaccines: DTaP-Hib and Hep B-Hib
what type of cells mediate the immune response to the vaccine?
T cell dependent antigens
protective antibody response in infants >2 months of age
prior protection through maternal antibodies
who can get the Hib vaccine?
infants >6 weeks
not >5 years unless immunocompromised
how to identify Hib through lab tests
gram stain of CSF or synovial fluid antigen (PRP) detection in CSF or urine culture -requires media containing factors V and X -chocolate agar -SBA w/ s. aureus (hemolytic)
what is NTHi?
nontypable H.influenzae
where is NTHi located?
colonize nasopharynx of most individuals during the first few months of life, remain throughout life
localized spread can lead to disease
common illnesses caused by NTHi
otitis media
sinusitis
pneumonia
treatment oh H. influenzae
penicillin resistance common in US (30%)
for invasive: 3rd gen ceph
for otitis media/sinusitis: ampicillin, ceph, fluoroquinolone
characterize pseudomonas
gram -, motive bacilli obligate aerobes ubiquitous in environment opportunistic pathogen common nosocomial
discuss the overarching properties of p. aeruginosa
most common human pathogenic pseudomonad
opportunistic
common nosocomial
what types of infections does p. aeruginosa primarily cause?
skin
pulm
outer ear
eye
what are the virulent properties of the P.aeruginosa capsule
antiphagocytic
contributes to antibiotic resistance
adhesin
polymer of mannuronic and glucuronic acid
what is another name for the p.aeruginosa capsule
alginate
discuss the regulation of capsule production in p.aeruginosa
environmental (osmoregularity, nitrogen) and quorum sensing
produced at high levels in lungs (particularly in CF of immunocompromised patients)
production ceases in vitro
BASICALLY, can sense conditions, when conditions are appropriate, capsules grow
what is the difference between in vitro p.aeruginosa and p.aeruginosa cultures from CF lung?
in vitro: no capsule, smooth and pigmented
flagella+, pili+, alginate-
CF lung: mucoid colonies of highly encapsulated bacilli, shiny
flagella-,pili-,alginate+
what appearance can a capsule give on biofilm?
halo
p.aeruginosa exotoxin A
A-B toxin: A subunit ADP ribosylates elongation factor EF-2
affects protein synthesis
p.aeruginosa Exotoxin S
major virulence factor
injected T3SS effector protein
disrupts signal transduction and blocks phagocytosis
p.aeruginosa exotoxin U
cytotoxic for macrophages
p.aeruginosa elastase
degrades elastin (protein in pulmonary and endothelial tissues) production regulated by quorum sensing
what types of infections does p.aeruginosa cause in healthy people?
folliculitis "hot tub rash" otitis externa "swimmers ear" eye infections (trauma)
describe acute otitis externa
edema and desquamating epithelium, soft cerumen, purulent discharge (has to be removed prior to treatment of the infection)
default treatment of otitis externa
eardrops
-mild: acetic acid + propylene glycol + hydrocortisone
-moderate to severe: ciprofloxacin + hydrocortisone
no neomycin drops if TM is ruptured
otisis externa prevention
alcohol eardrops
what types of infections does p.aeruginosa in immunocompromised people?
bacteremia
burn wound infections
malignant otitis externa
pulmonary infections
when do burn wounds become infected with p.aeruginosa?
> 2 weeks
pathogenesis of malignant otitis externa
spreads from ear to nearby tissues, bone, cranial nerves, brain
95% p.aeruginosa
DOC: IV ciprofloxacin
early diabetics, AIDS, chemo
conditions that are susceptible to pulmonary infections caused by p.aeruginosa
COPD
CF
neutropenia
discuss the presence of p.aeruginosa in CF patients
80-90% of patients are colonized
lungs colonize by age 3
biofilm formation
what does p.aeruginosa cause in CF patients
recurrent episodes of pneumonia with increasing frequency
antibiotics select for highly resistant strains
pathogenesis of pneumonia due to p.aeruginosa
aspiration of upper respiratory tract secretions
can lead to bacteremia, shock, alveolar hemorrhage, and lung necrosis
risk factors for p.aeruginosa pneumonia
neutropenia chronic lung disease CHF mechanical ventilation lung burns most common in ICU and nursing homes
identification of p.aeruginosa on culture
obligate anaerobe catalase + oxidase + green pigmented, often fluorescent (mix of blue pyocyanin and yellow fluorescin) siderophores fruity smell
what is pyocyanin
toxin found in patients’ airway secretions
affects multiple cellular functions
what are the effects of pyocanin
intracellular oxidative stress low ATP (cilia, CFTR) low NADPH (antibacterial) gene expression -down: catalase -up: oxidative stress response, mucins, cytokines, chemokines innate immune mechanisms: neutrophils
treatment of systemic p.aeruginosa
multidrug resistance common
initial empiric combination treatment with antipseudomonal B-lactam + B-lactamase inhibitor + aminoglycosides
monotherapy chosen on basis of local susceptibility patterns
last resort treatment of p.aeruginosa
polymyxin E
solubilizes bacterial membranes
