A 3-year-old boy is brought to the clinic due to left ear pain over the past 3 days. Last week, the patient developed a runny nose and cough, which resolved 2 days prior to the development of ear pain. He has no chronic medical conditions. Temperature is 38.4 C (101.1 F). There is purulent drainage from the left ear. Otoscopic examination of the left ear reveals a normal-appearing external canal and an erythematous tympanic membrane with purulent fluid pooling within the distal external canal. Which of the following organisms is the most likely cause of this patient's diagnosis?

Question

A 3-year-old boy is brought to the clinic due to left ear pain over the past 3 days.  Last week, the patient developed a runny nose and cough, which resolved 2 days prior to the development of ear pain.  He has no chronic medical conditions.  Temperature is 38.4 C (101.1 F).  There is purulent drainage from the left ear.  Otoscopic examination of the left ear reveals a normal-appearing external canal and an erythematous tympanic membrane with purulent fluid pooling within the distal external canal.  Which of the following organisms is the most likely cause of this patient's diagnosis?

Quizplus · Accepted Answer

11ec160b_37f2_737d_9249_63f4d3fec140_MD0001_00 This patient with an erythematous tympanic membrane and purulent otorrhea has acute otitis media (AOM) complicated by tympanic membrane perforation, which can be obscured due to drainage. Acute middle ear infections occur most commonly in young children (age 6 months to 2 years) and are often due to Streptococcus pneumoniae. A viral upper respiratory infection (URI) typically precedes the development of AOM because it causes inflammatory edema of the respiratory mucosa that can lead to obstruction of the eustachian tube. The eustachian tube normally opens to equalize middle ear pressure and drain secretions. Therefore, obstruction leads to the accumulation of secretions, providing a rich medium for bacterial growth. Bacterial colonizers of the upper respiratory tract (eg, S pneumoniae, Haemophilus influenzae, Moraxella catarrhalis) then proliferate in the middle ear secretions. This overgrowth of bacteria and consequent immune response result in AOM. Suppurative fluid accumulation increases middle ear pressure and causes the tympanic membrane to become inflamed and bulge outward. If the eustachian tube remains obstructed, this increased pressure can rupture the tympanic membrane. (Choice A) Although Klebsiella pneumoniae can be a colonizer of the mouth and throat, it is unlikely to cause AOM in otherwise healthy children. Instead, it more often causes respiratory diseases in older, immunosuppressed patients (eg, pneumonia in patients with alcohol overuse). (Choice B) Moraxella catarrhalis is also an upper respiratory colonizer that can cause AOM. However, infection with it is less common than with S pneumoniae. (Choice C) Proteus mirabilis classically causes genitourinary infections; its ability to split urea alkalinizes the urine, increasing the formation of kidney stones. (Choice D) Pseudomonas aeruginosa is more commonly implicated in otitis externa than AOM. (Choice E) Staphylococcus aureus is typically found as a colonizer of the skin rather than the respiratory tract. Therefore, it is more often implicated in skin and soft tissue infections, including otitis externa. Educational objective: Acute otitis media usually occurs after a viral upper respiratory infection causes obstruction of the eustachian tube. This obstruction leads to the accumulation of secretions, which encourages bacterial growth. The most common bacterial causes are respiratory colonizers, including Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. __________ References: Acute otitis media. (http://www.ncbi.nlm.nih.gov/pubmed/29262176)

A 3-Year-Old Boy Is Brought to the Clinic Due to Left