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Neurosensory System Microbiology of the Ear


External Ear. Review of Structure. Auricle ... Acute diffuse external otitis (swimmer's ear) ... Important to differentiate from middle ear infection. ... – PowerPoint PPT presentation

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Title: Neurosensory System Microbiology of the Ear

Neurosensory SystemMicrobiology of the Ear
  • Dr. Jeffrey Felton
  • MS 1

External Ear
  • Review of Structure
  • Auricle cartilage covered with skin
  • External Auditory Canal extension of skin
    surface with epidermis and dermis, including the
    outer surface of the tympanic membrane
  • Cartilaginous canal outer part
  • Epidermis has papillae, hair follicles, sebaceous
    sweat glands opening into hair follicles
  • Cerumen produced by glands makes a fairly
    impervious lipid and acid cloak for the skin. It
    has antibacterial and antifungal action.
  • Dermis and subcutaneous layer are well developed.
  • Osseus canal inner part, skin is very thin.

External Ear
  • Normal Flora
  • Same as oily areas of the skin
  • Staphylococcus epidermidis, others
  • Micrococcus
  • Corynebacterium
  • Propionbacterium

Diseases of the External Ear
Diseases of the Other EarOtitis Externa
  • Diseases due to gram (-) bacteria
  • Acute diffuse external otitis (swimmers ear)
  • Etiology almost always due to gram (-)
    organisms, especially P. aeruginosa, P. vulgaris
    and fungi as secondary invaders.
  • Predisposing Factors
  • Elevated environmental humidity
  • High temperature
  • Maceration of skin folllowing prolonged exposure
    to moisture
  • Local Trauma
  • Introduction of exogenous bacteria, especially
  • Clinical Signs and Symptoms
  • Fullness, itching, pain, hearing loss due to
    occlusion of lumen
  • Erythema, green-tinted serous discharge

Diseases of the Other EarAcute Otitis Externa
  • Laboratory diagnosis
  • Cultures and determination of antibiotic
    sensitivities are seldom necessary in infections
    of the external canal, except in rapidly
    progressive cases that are refractory to
  • Control
  • Clean ear
  • Appropriate antibiotics
  • Eliminate predisposing factors
  • Keep ear dry

Diseases of the External EarLess Common
  • Bullous (hemorrhagic) external otitis
  • Clinical signs include hemorrhagic bullae on
    osseus canal walls, rupture of bullae causes
    bloody discharge
  • Etiology is P. aeruginosa
  • Important to differentiate from middle ear
    infection. In this case, there is no previous
    respiratory infection.
  • Granular external otitis
  • May develop from untreated diffuse otitis externa
  • Skin in meatus is raw, coated with scanty creamy
    pus and granulations on osseous meatus.
  • Etiology is Proteus and P. aeruginosa
  • Cultures and antibiotic sensitivities are usually

Diseases of the External EarLess Common
  • Necrotizing (malignant) external otitis
  • This is very serious!
  • Etiology is usually due to P. aeruginosa alone,
    occasionally mixed
  • Predisposing factors include diabetes, when
    diffuse external otitis fails to heal
  • Necrosis with granulation tissue on floor of
    external auditory canal at junction of osseous
    and cartilagenous canals. It may spread through
    the clefts, expose bone and cartilege and spread
    into deep tissues, and even cause osteomyelitis
    and meningitis.

Diseases of the External EarGram () Bacteria
  • Diseases due to S. aureus
  • Furuncle and carbuncle (acute localized otitis
  • Abscesses
  • Infectious eczematoid dermatitis, consequence of
    perforated OM.
  • Diseases due to Group A B-hemolytic strep
  • Ersipelas
  • Diseases due to S. aureus or Group A B-hemolytic
  • Ecthyma, w. S. aureus as a secondary invador
  • Impetigo contagiosum
  • Cellulitis

Diseases of the External EarFungi Yeasts
  • Known as otomyocosis or mycotic otitis externa
  • Saphrophytic fungi
  • Acute otomyocosis
  • Etiology is A. niger and other fungi such as
  • Predisposing factors include hot weather, use of
    ear drops containing antibiotics and/or steriods
    over a period of weeks (steriods are bad news,
    fungi grow well)
  • Signs and symptoms
  • Itching fullness early on
  • Lumen filled with waxey debris, and a velvety
    gray pseudomembrane lines the skin of the meatus
    and the tympanic membrane
  • Wet mount will show fungi, neutrophils, and
    epithelial cells

Diseases of the External EarFungi Yeasts
  • Saphrophytic fungi
  • Acute otomyocosis
  • Prognosis if severe, may cause cellulitis and
    secondary bacterial infection, and the secondary
    bacterial infection is the greatest danger
  • Control
  • Eliminating predisposing factors
  • Remove debris as much as possible
  • Use antifungal agents

Diseases of the External EarFungi Yeasts
  • Saphrophytic fungi
  • Chronic (recurrent) otomyocosis
  • Etiology is Aspergillus, Mucor, yeastlike fungi,
    dermatophytes, miscellaneous fungi and
  • Signs symptoms at first asymptomatic, then
    itching, then mild pain, a slight seropurulent
    discharge and mild deafness
  • Predisposing factots include chronic bacteril
    infection, foreign body or necrotic tumor,
    secondary to urulent discharge of the middle ear
  • Otoscope may reveal filamentous fungi and spores
  • Control of underlying problem, plus therapy for
    fungi and removal of debris

Diseases of the External EarFungi Yeasts
  • Pathogenic Fungi
  • Most are typical parasites, the dermatophytes and
    M. furfur
  • Candida otomyocosis
  • Predisposing factors include moisture and
    maceration, underlying immulogical incompetence
    and longstanding oral and topical antibiotics and
  • Signs and symptoms include chronic erythema, mild
    edema, focal suppuration, widespread whitish
    hyperkeratosis and hyperplasia over osseous canal
    or mastoid cavity
  • Control by removing predisposing factors and use
    antifungal agents

Diseases of the External EarViruses
  • Infections that affect skin or mucous membranes
  • Herpes simplex
  • Herpes zoster
  • Verrucae, papovavirus group
  • Molluscum contagiosum, poxvirus group

Diseases of the External EarArthropod Parasites
  • Typical skin problems
  • May get wheals, vesicles, bullae, papules,
    nodules, ulcerations, hemorrhage into the skin,
    granulomas, due to the bite or presence of such
    arthropod parasites as mosquitos, chiggers,
    ticks, ect
  • Scabies in infants and young children

Diseases of the External EarHypersensitivity
  • Eczematoid external otitis delayed type
    hypersensitivity, due to hair sprays, shampoos,
    dyes, local medications, plastics, rubber
  • Photoallergic dermatitis also delayed type, due
    to deoderant soaps, compounds in sun screening
  • Atopic dermatitis may also occur

Diseases of the External EarLaboratory Diagnosis
  • Cultures and smears are not taken if the nature
    of the problem is obvious from clinical signs
  • To take a specimen, if there is a history of
    long-standing bacterial or fungal infection, or
    if the patient is not responsible for therapy,
    use a small, sterile, cotton-tipped applicator,
    and if possible, streak it onto the appropriate
    culture medium. In addition, gram stain should
    be made of purulent material to immediately
    indicate the likely pathogen.

Diseases of the Middle Ear
  • Review of structures
  • Middle ear
  • Air-filled cavity in bone, communicating with
    nasopharynx by means of the auditory tube, which
    serves to ventilate and drain the middle ear
  • Lined with thin epithelium
  • Contains malleus, incus, stapes which transmit
    vibrations from the tympanic membrane to the oval

Diseases of the Middle Ear
  • Eustachian tube
  • Eustachian tube is osseous and open near the
    middle ear it is cartilaginous and flexible near
    the nasopharnyx and the walls are in apposition
    except when yawning
  • The nasopharyngeal opening of the Eustachian tube
    is surrounded by lymphoid tissue
  • In adults, this tube enters the nasopharnyx with
    up to a 45 degree angle from horizontal
  • In children, the tube angle is around 10 degrees
    from the horizontal, and stiffness of the tube is
    less than in older children and adults
  • Dysfunction of the tube may be due to anatomical
    or physiological factors apparently leading to
    pathogenesis of otitis media

Diseases of the Middle Ear
Middle Ear Normal Flora
  • None!
  • Bacteria and viruses enter through internal
    auditory tube, lymphatic or blood vessles

Diseases of the Middle Ear
  • Acute suppurative otitis media
  • Predisposing factors
  • Upper RTI, with highest incidence between
    December-March in northern temperate climates
  • Age of the child, common in children between 6
    and 24 months
  • Previous history of otitis media
  • Allergy
  • Anatomical or functional deviation of middle ear
    or eustachian tube
  • Child in day care or sibling with recurrent OM
  • Lack of breast feeding
  • Develops musculature
  • Enhances drainage
  • Ancestry
  • Native americans
  • Inuit

Diseases of the Middle Ear
  • Etiology
  • 35 S. pneumoniae (Pneumococus) is the most
    common, with 8 capsular serotypes causing the
    majority of cases
  • 25 H. influenzae next most common, 90 are
    untypable and 10 are type B
  • 4-13 Moraxella catarrhalis
  • 2-4 Group A Strep
  • 1 S. aureus

Diseases of the Middle Ear
  • Pathogenesis
  • Viral URTI starting 5-10 days before onset,
    causing partial to complete mechanical
    obstruction of the Eustachian tube because of
  • Absorption of gasses from the air in the middle
    ear leads to negative middle ear pressure,
    resulting in aspiration of organisms from nasal
    end of Eustachian tube into middle ear cavity
  • Infection, inflammation, swelling and lack of
    drainage results in middle ear effusion that is
    purulent due to neutrophil migration
  • Pressure increases, causing tympanic membrane to
    bulge out, and maybe even perforate
  • Very occasionally, abnormal patency of the
    Eustachian tube can be a problem because
    organisms can be forced into the middle ear by
    sneezing or blowing the nose.

Diseases of the Middle Ear
  • Signs Symptoms
  • Abrupt onset of fullness, pain, and moderate
    fever, but not in all cases
  • Usually unilateral
  • Reddening and bulging of the tympanic membrane
  • Moderate leukocytosis
  • Spontanious perforation may occur in first 24-48
    hours, with otorrhea

Diseases of the Middle Ear
  • Diagnosis
  • Signs symptoms
  • Ordinary middle ear fluid is not aspirated for
    culture unless there is unsatisfactory clinical
    response or an unusual pathogen is suspected.
  • Test for presence of fluid or pressure in the
    middle ear
  • Pneumatic otoscope
  • Tympanometry
  • Acoustic reflectometry

Diseases of the Middle Ear
  • Treatment
  • Appropriate antibiotics, plus acetaminophen for
    pain and fever
  • Use of decongestants and antihistamines
  • May need to perform myringotomy to relieve pain
    and pressure, if so, perform cultures and
    antibiotic senstivities from pus on sterile knife

Diseases of the Middle Ear
  • Sequelae
  • Continuing fluid in middle ear for weeks or
    months after resolution of acute infection is not
  • In preantibiotic era, acute otitis media would
    have lead to mastoiditis or labyrinthitis by
  • Now, meningitis may occur but this is unusual

Diseases of the Middle Ear
  • Prevention
  • Immunization against certain predisposing viral
  • Management of allergies
  • Breastfeeding, limitation of bottle-feeding in
    supine position
  • Continuous antibiotic prophylaxis in high risk
    groups during winter and spring
  • Immunization against bacterial pathogens, such as
    H. influenzae type B and certain serotypes of S.

Diseases of the Middle Ear
  • Acute suppurative otitis media in the newborn
  • Etiology usually the same as in slightly older
    children, S. pneumoniae and H. influenzae. If
    neonate septicemic, then S. aureus, or C.
  • Predisposing factors include prematurity, infants
    on respirators, septic infants born to mothers
    with prematurely ruptured membranes
  • Laboratory diagnosis culture is essential for
    identification and antibiotic susceptibility

Diseases of the Middle Ear
  • Chronic Otitis Media with Effusion
  • Etiology, perhaps allergy, viral infection,
    previous acute suppurative otitis media. In one
    third of cases, bacteria are present in the fluid
    (same as acute OM)
  • Predisposing factors include complete obstruction
    of the Eustachian tube
  • Usually there is a mild-to-moderate conductive
    hearing loss which is resolved with resolution of
    the middle ear effusion.
  • Treatement includes management of underlying
    allergies, infection or obstruction, watchful
    waiting, myringotomy, tympanostomy tubes,

Tympanostomy Tubes
Diseases of the Middle Ear
  • Recurrent OM -- defined as more than three
    episodes in six months
  • Etiology is the same as acute OM, except that S.
    aureus may occur here, especially when rupture of
    the tympanic membrane occurs
  • Chronic OM have anatomical changes in the
    middle ear that persist beyond the diagnosis and
  • Associated with central or anterior perforation
    and mastoid infection
  • Epidermal lining of the external auditory canal
    may invade and grow through the aperture

Diseases of the Middle Ear
  • Chronic OM have anatomical changes in the
    middle ear that persist beyond the diagnosis and
  • Signs symptoms include a pus, yellow to gray,
    and often extrusion of cheesy or greasy
    cholesteatomatous material (see pictures below).
  • Often associated with gram (-) bacteria, but may
    get periodic superinfection with pyogenic
  • Requires surgery for repair

Diseases of the Tympanic Membrane
  • Bullous myringitis inflammation of the lateral
    surface of the tympanic membrane
  • Characterized by the presence of a number of
    large blebs containing blood and/or serous fluid
  • May be caused by various viruses or by Mycoplasma

Note this picture is actually a Hemorrhagic
residue occluding EAC 24h post-referred
cerumenectomy by curettage
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