WEEK 1: Ear infections Flashcards
State the parts that make up the external ear.
Outer ear comprises pinna & external auditory meatus (ear canal).
Name the structure that contributes to Otitis externa.
How does it contribute to that? (4 ways)
Ear canal structure contributes to otitis externa
- Cul-de-sac: The ear canal is like a tunnel, with a cul-de-sac-like structure, approximately 2.5cm in length. This shape makes it prone to the accumulation of debris, secretions, and foreign bodies. These materials can get trapped in the canal, leading to irritation and infection.
- Hairs: Hairs present in the ear canal can trap debris, further contributing to the accumulation of material that can harbor bacteria and fungi.
- Structure: The outer ear canal is divided into two parts - the lateral 1/3 overlies cartilage, while the remaining part has a base of bone covered by thin skin. This composition makes the canal susceptible to trauma, as well as providing a suitable environment for microbial growth.
- Prone to moisture: excellent environ. for bacterial & fungal growth
Describe the defense mechanisms of the external ear.
Skin of cartilagenous section contains:
-Sebaceous (lipid-producing) & apocrine (ceruminous) glands
-Hair follicles
(these serve as mechanical barrier against pathogens)
Describe the composition of ear wax (cerumen).
Describe how the ear wax protects the external ear.
Cerumen (earwax): secretions by sebaceous & apocrine glands mixed with desquamated epithelial cells
-Lipid-rich & hydrophobic (repels water)
-Acidic (pH6.8) contains lysozyme - inhibits bacterial & fungal growth
Outline Commensal bacteria of outer ear.
Predominantly Gram+ve bacteria account for 90% of normal flora
i.e.
-Coagulase negative Staphylococci (Gram+ cocci):
S. auricularis, S. epidermidis &S. capitis
-Corynebacterium species (Gram+ve rods)
C. auris, Turicella otitidis
-Streptococci & Enterococci species
-Others include Propionibacterium acnes
Define otitis.
State the 3 types of otitis.
Infection & inflammation of the ear
-Otitis externa
-Otitis media
-Otitis interna or labyrinthitis
What is the other name for otitis externa?
Define otitis externa.
Otitis externa: ‘Swimmers ear’
Otitis externa, also known as swimmer’s ear, is an inflammatory condition of the outer ear canal.
Describe the pathogenesis of acute Otitis externa.
When there’s a break in the skin-cerumen barrier, it disrupts the natural defense mechanisms of the ear canal.
Cerumen (earwax) normally acts as a protective barrier, helping to prevent infection by trapping debris and providing an acidic environment that inhibits bacterial growth.
However, when there’s a break in this barrier, inflammation can occur, leading to symptoms such as pruritus (itchiness), which often prompts scratching, and sometimes even obstruction of the ear canal.
Furthermore, alterations in defense mechanisms such as:
*Changes in the quantity of cerumen
*Impairment of epithelial migration (the movement of skin cells)
*An increase in pH can create a moist, alkaline environment within the ear canal. This environment is conducive to bacterial growth, further exacerbating the inflammation and infection.
Describe the pathogenesis of Chronic Otitis externa.
Persistent low grade inflammation for >3mth.
Generally less painful but profound itching & persistent discharge.
Commonly allergic contact dermatitis e.g. metal earrings, cosmetics, shampoos, hearing devices
Incomplete resolution of an acute infection
Outline the risk factors for otitis externa.
- Mechanical removal of ear wax
- Insertion of foreign objects
*Cotton swabs, matches, Fingernails
*(Hearing aids)
*(Ear plugs) - Trauma to ear canal
- Moisture
- High environmental TC
- Chronic dermatologic diseases
*Eczema
*Psoriasis
*Seborrheic dermatitis
*Acne
Describe the epidemiology and demographics of otitis externa.
Highest in childhood, decreasing in age. Most frequently in children & adolescents, much less in >20yr
May also be associated with warmer seasons; warm & humid climates or water-based activities e.g. outdoor water sports &/ or activities
Causative pathogens of acute otitis externa.
What causes Majority (90%) of cases bacterial? (2)
Majority (90%) of cases bacterial:
-Pseudomonas aeroginosa (30-50%)
-Staphylococcus aureus
Others may include Staphylococcus epidermidis, Corynebacterium & Microbacterium species
Define otomycosis.
Otomycosis: fungal infections of outer ear
How many % of outer ear infections are caused by fungi?
Fungi can also cause outer ear infections approximately 10% cases are fungal.
What is the major contributor to outer ear fungal infections?
These fungal infections, often termed otomycosis, can occur due to various factors, but one significant contributor is the prolonged treatment of bacterial otitis externa.
This prolonged antibiotic treatment can disrupt the normal flora of the ear canal, creating an environment conducive to fungal overgrowth.
Mixed bacterial & fungal infections common.
State the 2 main predisposing factors to fungal outer ear infections.
Predisposing factors: diabetes & immunocompromised state
State the Primary causative pathogens for outer ear fungal infections.
Primary causative pathogens:
- Aspergillus (80-90%cases), followed by Candida species
Aspergillus niger infection has distinctive appearance: i.e. small black conidiophores on white hyphae.
Fluffy, whitish discharge but may be black, gray, bluish-green or yellow
Outline other causes of acute otitis externa.
Acute otitis externa may also be due to:
-Allergic contact dermatitis e.g. from earrings, chemicals in cosmetics
-Contact dermatitis due to prescribed or OTC ototopical antimicrobial agents e.g. neomycin, benzocaine
-Existing dermatologic conditions e.g. psoriasis, atopic dermatitis
-Previous radiation therapy may affect the ear skin & blood supply resulting in ischemic changes, altering cerumen production & so predisposing the ear to infections.
Gram-ve aerobic rod, with polar flagella. Commonly found in the environment e.g. soil, water.
It is not a normal commensal of ear canal. Its identification indicates its presence as a pathogen
Intrinsically/naturally antibiotic resistant, complicating optimal antibiotic therapy
Name the pathogen.
Pseudomonas aeruginosa
People with diabetes have a Predisposition to ear infection with Pseudomonas aeruginosa.
Discuss 2 ways how diabetes is a contributing factor.
Predisposition in diabetics & the elderly
Remember: Diabetes predisposes to microangiopathy in many anatomical sites incl. in ear canal
Increased pH in diabetic cerumen(under normal states pH low), reduces colonisation of commensal bacteria, thus predisposing to pathegens
Discuss the Diagnosis of acute otitis externa.
- Swab may be collected & sent to lab for culture & tests for severe & recurrent cases.
- For mild & moderate cases empiric therapy initiated without request for lab tests
*Otitis externa must be distinguished from suppurative otitis media & hearing assessed. As in both cases, there may be extensive discharge, &/or desquamated epithelium in the canal
-Topical ointments ineffective until debris removed
*Preferable not to irrigate a discharging ear incase of a perforated tympanic membrane
Rather
*Swabbing with cotton tipped applicators or suction to be done to observe tympanic membrane (by ENT specialist)
Describe the diagnostic symptoms for acute otitis externa mild , moderate and severe disease.
*Mild disease is characterized by minor discomfort and pruritus (minimal canal oedema)
*Moderate disease is characterized by an intermediate degree of pain and pruritus, canal may be partially occluded
*Severe disease is characterized by;
- Intense pain.
- Canal is completely occluded by oedema.
- Auricular and/or periauricular cellulitis
- Regional lymphadenopathy
- Fever be present
Describe the management of acute otitis externa.
*Meticulous ear cleaning & application of topical antibiotic therapy or ear drops. A ‘wick’ may be placed to facilitate application of topical agent if there is extensive swelling
*Topical agents must contain broad spectrum antibiotic particularly effective against P. aeruginosa & S. aureus:
- Aminoglycosides:
Aminoglycoside antibiotics, such as neomycin, gentamicin, and tobramycin, are effective against a wide range of bacteria, including many Gram-negative and some Gram-positive bacteria.
They work by inhibiting bacterial protein synthesis.
Aminoglycosides are commonly used in topical ear drop formulations for treating outer ear infections, including cellulitis.
- Chloramphenicol: Chloramphenicol is a broad-spectrum antibiotic effective against a variety of bacteria, both Gram-positive and Gram-negative.
It works by inhibiting bacterial protein synthesis. Chloramphenicol is available in various formulations, including topical preparations for ear infections.
- Fluoroquinolones (e.g., ciprofloxacin):
Fluoroquinolone antibiotics, such as ciprofloxacin, are broad-spectrum antibiotics effective against many Gram-negative and some Gram-positive bacteria.
They work by inhibiting bacterial DNA gyrase, an enzyme essential for bacterial DNA replication.
Fluoroquinolones are available in various formulations, including oral, topical, and intravenous, and they are commonly used for treating ear infections, including cellulitis.
- Corticosteroid, glucocorticoid in combination with an antibiotic e.g. ciprofloxacin, is effective treatment for mild & moderate cases
NB. For severe cases & the immunosuppressed: both topical & systemic antibiotics required, regardless of severity.
Define otitis media.
Otitis media is an inflammatory condition that affects the middle ear.
Otitis media is Frequently in children vs. adults.
Children of what age groups are mostly affected.
Describe structural characteristics that make them prone to the infection.
Frequently in children vs. adults
Extremely more common among children 3 months to 3 years.
WHY?
*Structural differences of eustachian tube (ET) i.e. in children, it’s shorter, narrower, more horizontal & muscles opening tube weaker
More prone to nasopharyngeal secretions being trapped in it & it’s closer to the middle ear.
The trapped secretions may contain viruses or bacteria, which multiply causing infection & inflammation.
Viruses & bacteria can move up the shorter eustachian tube causing middle ear infections
