A 2-year-old boy is brought to the physician by his mother because of fever and pain in the left ear for the past 3 days. The mother states that he has been rubbing his left ear repeatedly since he woke up this morning. The patient has had 2 previous episodes of acute otitis media. Temperature is 38.1 C (100.6 F). Otoscopic examination shows a perforated right tympanic membrane with erythema and purulent exudate. Cultures from the exudate yield small, oxidase-positive, gram-negative coccobacilli that grow on factor X- and factor V-supplemented media, consistent with Haemophilus influenzae. The patient's immunizations are up to date. Which of the following best explains this patient's susceptibility to the pathogen causing his current infection?

Question

A 2-year-old boy is brought to the physician by his mother because of fever and pain in the left ear for the past 3 days. The mother states that he has been rubbing his left ear repeatedly since he woke up this morning. The patient has had 2 previous episodes of acute otitis media.  Temperature is 38.1 C (100.6 F).  Otoscopic examination shows a perforated right tympanic membrane with erythema and purulent exudate.  Cultures from the exudate yield small, oxidase-positive, gram-negative coccobacilli that grow on factor X- and factor V-supplemented media, consistent with Haemophilus influenzae.  The patient's immunizations are up to date.  Which of the following best explains this patient's susceptibility to the pathogen causing his current infection?

Quizplus · Accepted Answer

Eductional Objective: Nontypeable strains of Haemophilus influenzae are part of the normal upper respiratory tract flora and are a common cause of acute otitis media, sinusitis, and bronchitis.  Because nontypeable strains do not form a polysaccharide capsule, immunity is not conferred by vaccination with the H influenzae type b vaccine.

A 2-Year-Old Boy Is Brought to the Physician by His