Eye and Ear infections

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EYE & EAR CULTURES
ANATOMY OF THE EAR
Tympanic
membrane
Inner ear
Middle ear
Eustachian tube
EAR INFECTIONS &
CULTURES

Otitis media
– Most common infection in young children
– 1/3rd of all pediatric visits due to infection of
middle ear
– Often the result of viral or bacterial infections
of the respiratory tract
– Clearance mechanism of Eustachian tubes
impaired; tubes shorter in children than adults
– Cultures required only infrequently
OTITIS MEDIA
Specimen collection by typanocentesis
 Symptoms
– Fever and irritability (may be only symptom)
– Tugging at affected ear
– Ear pain and red, bulging tympanic membrane
– Drainage of purulent secretions into ear canal

OTITIS MEDIA:
TYMPANIC MEMBRANE
Bulging
tympanic
membrane
OTITIS MEDIA

Causative agents
– *Streptococcus pneumoniae
– *Haemophilus influenzae
– Streptococcus pyogenes
– Moraxella catarrhalis (in children)
– Staphylococcus aureus
– Gram negative bacilli (following antibiotics)
– Group B beta streptococci (newborns)
SWIMMERS EAR –
OTITIS EXTERNA
Maceration of outer ear from swimming, hot and
humid weather, or hot tub use
 Pools with high coliform counts increase risks
 Symptoms
– Irritation and itch
– Swelling and pain

OTITIS EXTERNA
Infection
and
irritation
in the
outer ear
OTITIS EXTERNA
Specimen collection - insertion of sterile swab into
ear
 Causative agents
– Pseudomonas spp. (most common)
– Enterobacteriaceae spp., including E. coli and
Proteus spp.
 Prevent through complete drying of ears using
acidic alcohol (vodka and vinegar?)
 Rx with antibiotic containing otic drops

OBTAINING A SPECIMEN FOR
CULTURING THE OUTER EAR
EAR CULTURES

Set-ups:
– CAP (H. influenzae) “chocolate Agar plates”
– BAP ( Blood Agar Plates)
– MacC or EMB
– CNA?
 nalidixic
acid and colistin in Columbia Blood Agar
– the growth of most gram-negative bacteria, including
Klebsiella, Proteus and Pseudomonas species
– Thioglycollate broth (middle ear sources only)
– Smear
EYE ANATOMY
EYE INFECTIONS &
CULTURES

Conjunctiva and cornea invaded by few organisms
if barrier is intact
– Lysozyme (gram positives)
– Immunoglobulins
– “Filters” (lashes)
– Other anatomic features (density of tissues)
EYE PATHOGENS

Truly invasive organisms
– N. gonorrhoeae and meningitidis
– Streptococcus pneumoniae
– Listeria monocytogenes
– Corynebacterium diptheriae
– Staphylococcus aureus
– Pseudomonas aeruginosa
EYE INFECTIONS
Normal flora
– *Coagulase negative staphylococci
– *Propionibacterium spp.
– Corynebacterium spp.
– Staphylococcus aureus
– Haemophilus influenzae
– Streptococci pneumoniae
 NF usually protects eye from invasion by more
harmful organisms

CONJUNCTIVITIS (“pink eye”)

Causative agents
– Adults
Staphylococcus aureus (warmer climes)
Streptococcus pneumoniae (cooler climes)
– Infants & children
Haemophilus influenzae
Staph. aureus
Streptococcus spp.
Enterobacteriaceae
CONJUNCTIVITIS OR
“PINK EYE”
CONJUNCTIVITIS

Causative agents
– Neonates
Neisseria gonorrhoeae (large volume of
exudate)
Neisseria meningitidis (large volume of
exudate)
Chlamydia trachomatis (requires special
culturing or diagnostic techniques)
– Viruses, fungi, and parasites
– Allergies
CONJUNCTIVITIS

Common means of infection
– Birth canal (eg., Chlamydia trachomatis &
Neisseria gonorrhoeae)
– Hand-eye contact (N. gonorrhoeae, Staph.
aureus, H. influenzae)
– Contaminated cosmetics and medications
(Staph. aureus, gram negative bacilli)
CONJUNCTIVITIS
AGENT EXUDATE
& CELLS
LIDS
SWELL
NODES
INVOLVED
Bacteria Pus,PMNs,
clear
Viruses Monos,
clear
Allergy Eos.,
clear
Moderate No
No
Minimal
No
Yes
Moderate No
to severe
ITCH
Intense
CONJUCTIVITIS

Specimen collection
– Dacron (not cotton) swabs (cotton has oils with
antimicrobial properties)
– Conjunctival scrapings or expressed fluids
– Often collected by opthalmologist
– When possible, inoculate directly onto media
CONJUNCTIVITIS
Set-ups
– CAP (H. influenzae and N. gonorrhoeae)
– BAP
– Smear
 Special techniques required for Chlamydia
trachomatis, viruses, parasites

KERATITIS
Ocular emergency
 Causative agents
– Extremely critical cases due to rapidly acting
(24/48 hrs) enzyme-mediated “corneal melt”
Pseudomonas aeruginosa
Staphylococcus aureus

KERATITIS
 Keratitis
is a condition in which the eye's
cornea is inflamed.
KERATITIS
– Frequently isolated gram negatives
Serratia marcescens - common H2O microbe
Proteus mirabilis
Haemophilus influenzae
Moraxella spp.
– Frequently isolated gram positives
Streptococcus pneumoniae
Viridans streptococci
Coagulase negative staphylococci
– Mycobacterium other than tb. (MOTT)
– Viruses, fungi, parasite
KERATITIS

Common vectors
– Contact lenses!!!
– Latent viruses
– Contaminated soil and water
– Damage out doors from trees and sand
KERATITIS
Specimen collection –same as conjunctivitis
 Set-ups:
– CAP
– BAP
– Thioglycollate broth
– Anaerobic BAP?
– All purpose fungal medium?
– Smear
 Special techniques required for Chlamydia,
viruses, parasites

KERATITIS

Limulus lysate test may be rapidly diagnostic for
infections with g- bacilli
– Hemolymph from horseshoe crab plus microbe
(LPS?)  Clot
– Only useful for detection of gram negatives
– Does not differentiate between gram negatives
Congenital cataracts
 Result
of mother with rubella
Endophthalmitis
Endophthalmitis is an inflammation of the
internal coats of the eye.
 It is a dreaded complication of all intraocular
surgeries, particularly cataract surgery, with
possible loss of vision and the eye itself.


Other causes include penetrating trauma and
retained intraocular foreign bodies
ENDOPHTHALMITIS
Nosocomial sequellae of eye surgery
 Sight threatening
 Samples are aspirates of anterior chamber or
vitreous humor fluids
 Common isolates
– Coagulase negative staphylococci
– Viridans streptococci
– Enterococci
– Gram negative bacilli
– Other organisms associated with conjunctivitis
& keratitis

ENDOPHTHALMITIS
ENDOPHTHALMITIS

Set-ups:
– CAP
– BAP
– Anaerobic BAP
– All purpose fungal medium
– Broth medium
– Smear
– Extra samples held for viral and chlamydial
work-ups
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