Neurosensory System Microbiology of the Ear

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Neurosensory SystemMicrobiology of the Ear

• Dr. Jeffrey Felton
• MS 1

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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.

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External Ear

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

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Diseases of the External Ear
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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
  Pseudomonas
• Clinical Signs and Symptoms
• Fullness, itching, pain, hearing loss due to
  occlusion of lumen
• Erythema, green-tinted serous discharge

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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
  treatment
• Control
• Clean ear
• Appropriate antibiotics
• Eliminate predisposing factors
• Keep ear dry

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Diseases of the External EarLess Common
Infections

• 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
  done.

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Diseases of the External EarLess Common
Infections

• 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.

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Diseases of the External EarGram () Bacteria

• Diseases due to S. aureus
• Furuncle and carbuncle (acute localized otitis
  externa)
• 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
  strep
• Ecthyma, w. S. aureus as a secondary invador
• Impetigo contagiosum
• Cellulitis

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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
  Mucor.
• 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

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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

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Diseases of the External EarFungi Yeasts

• Saphrophytic fungi
• Chronic (recurrent) otomyocosis
• Etiology is Aspergillus, Mucor, yeastlike fungi,
  dermatophytes, miscellaneous fungi and
  actinomycetes
• 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

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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
  corticosteriods
• 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

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Diseases of the External EarViruses

• Infections that affect skin or mucous membranes
  include
• Herpes simplex
• Herpes zoster
• Verrucae, papovavirus group
• Molluscum contagiosum, poxvirus group

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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

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Diseases of the External EarHypersensitivity
reactions

• 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
  agents
• Atopic dermatitis may also occur

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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.

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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
  window.

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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

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Diseases of the Middle Ear
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Middle Ear Normal Flora

• None!
• Bacteria and viruses enter through internal
  auditory tube, lymphatic or blood vessles

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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

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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

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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
  swelling
• 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.

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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

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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

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Diseases of the Middle Ear

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

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Diseases of the Middle Ear

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

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Diseases of the Middle Ear

• Prevention
• Immunization against certain predisposing viral
  infections
• 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.
  pneumoniae

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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.
  trachomatis
• 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
  testing

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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,
  adeniodectomy

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Tympanostomy Tubes
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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
  treatment
• Associated with central or anterior perforation
  and mastoid infection
• Epidermal lining of the external auditory canal
  may invade and grow through the aperture

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Diseases of the Middle Ear

• Chronic OM have anatomical changes in the
  middle ear that persist beyond the diagnosis and
  treatment
• 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
  bacteria
• Requires surgery for repair

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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
  pneumoniae

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