A previously healthy 2-year-old boy is brought to the emergency department because of a 2-day history of fever and pain in the left lower extremity. His mother says that he has refused to walk for the past two days and has had a poor appetite. He returned from a weekend camping trip about a month ago. Further medical history reveals that his parents refused to have the vaccination. He is at the 80th percentile for height and 70th percentile for weight. He appears ill. His temperature is 39.3°C (102.7°F), pulse is 115/min, respirations are 19/min, and blood pressure is 95/50 mm Hg. Synovial fluid aspiration shows shows cloudy synovial fluid. Gram stain of the aspirate reveals pleomorphic, gram-negative coccobacilli. Cultures performed on a blood agar plate supplemented with a disk containing hematin and nicotinamide adenine dinucleotide (NAD⁺) grow colonies only near the disk. The organism responsible for this patient's condition most likely produces which of the following virulence factors?

Question

Quizplus · Accepted Answer

Eductional Objective: Haemophilus influenzae is a gram-negative coccobacillus that requires both X factor (hematin) and V factor (NAD⁺) to grow. H influenzae type b has an antiphagocytic polysaccharide capsule, which allows it to spread hematogenously and cause invasive disease such as septic arthritis and meningitis.

A Previously Healthy 2-Year-Old Boy Is Brought to the Emergency