A 14-year-old boy comes to the office due to right ear pain, pruritus, and discharge over the past week. He has had no cold symptoms, hearing loss, dizziness, or tinnitus. The patient returned yesterday from a 2-week vacation at a lake house, where he swam and fished daily. Temperature is 37.1 C (98.8 F), blood pressure is 110/70 mm Hg, and pulse is 75/min. Manipulation of the right ear during otoscopy elicits pain. There is prominent swelling and erythema of the ear canal with purulent and crusty debris. The tympanic membrane appears normal and has normal mobility. The left ear is normal. Nasal and oropharyngeal mucosa are also normal, and no rashes or skin lesions are noted. Which of the following is the most likely causative organism of this patient's current condition?

Question

A 14-year-old boy comes to the office due to right ear pain, pruritus, and discharge over the past week.  He has had no cold symptoms, hearing loss, dizziness, or tinnitus.  The patient returned yesterday from a 2-week vacation at a lake house, where he swam and fished daily.  Temperature is 37.1 C (98.8 F), blood pressure is 110/70 mm Hg, and pulse is 75/min.  Manipulation of the right ear during otoscopy elicits pain.  There is prominent swelling and erythema of the ear canal with purulent and crusty debris.  The tympanic membrane appears normal and has normal mobility.  The left ear is normal.  Nasal and oropharyngeal mucosa are also normal, and no rashes or skin lesions are noted.  Which of the following is the most likely causative organism of this patient's current condition?

Quizplus · Accepted Answer

11ec25c8_d250_cc01_bc81_25854c32abe2_MD0003_00 This patient has otitis externa ("swimmer's ear"), characterized by otic pain, erythema, edema, and purulent discharge. Otitis externa can occur in adults but is more common in children and adolescents. Otitis externa occurs frequently after swimming in outdoor water sources due to alteration of the ear canal pH, maceration of the skin, and introduction of bacteria into the ear canal. Cerumen is acidic and has antibacterial properties; loss of cerumen due to swimming or excessive ear cleaning increases the risk of otitis externa. Factors that disrupt the skin barrier (eg, eczema, psoriasis, trauma) or retain foreign material and water in the canal (eg, headphones, hearing aids) also increase the risk. The most common pathogenic organism in otitis externa is Pseudomonas aeruginosa, which can grow in water. Empiric treatment regimens for P aeruginosa should include drugs with antipseudomonal activity (eg, fluoroquinolone drops). Staphylococcus aureus is also common and is typically covered by antipseudomonal antibiotics. (Choices A and B) Fungal otitis (otomycosis), which may be caused by Aspergillus fumigatus or Candida albicans, is uncommon but may occur following eradication of a bacterial otitis or in association with a foreign body (eg, hearing aid). In general, otomycosis is less inflammatory than bacterial otitis and has a more insidious onset with a protracted, frequently recurrent course. It often has a characteristic appearance of white fungal debris with fruiting bodies or spores. (Choice C) Haemophilus influenzae type b (Hib), an encapsulated organism, causes serious invasive infections (eg, epiglottitis, meningitis, sepsis) but is rare in places with robust immunization programs. (Choices D, F, and H) Nontypeable (unencapsulated) H influenzae is not affected by the Hib vaccine and typically causes less invasive infections. It is a common cause of acute otitis media, along with Moraxella catarrhalis and Streptococcus pneumoniae. Acute otitis media is unlikely given this patient's normal tympanic membrane. (Choice E) Mucor species are responsible for invasive fungal sinusitis infections. These often fatal infections occur in immunocompromised individuals and can rapidly progress to involve the orbit or the brain. Black eschar from necrotic mucosa can often be seen on the nasal turbinates. Educational objective: Otitis externa ("swimmer's ear") is characterized by pain, erythema, edema, and discharge; it frequently occurs after swimming. Loss of cerumen, trauma, and foreign materials in the ear canal can increase the risk. The most common pathogen is Pseudomonas aeruginosa. References: Clinical practice guideline: acute otitis externa (http://www.ncbi.nlm.nih.gov/pubmed/24491310)

A 14-Year-Old Boy Comes to the Office Due to Right