Blood cultures from a 40-year-old man with subacute endocarditis grow a fastidious Gram-negative bacillus only after 6 days of incubation on enriched media. Which organism belongs to the group that causes this pattern of endocarditis?

• A Pasteurella multocida
• B Cardiobacterium hominis alone, excluding the other HACEK members
• C Aggregatibacter actinomycetemcomitans ✓
• D Capnocytophaga canimorsus

Explanation

The HACEK group comprises Haemophilus species, Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae. These fastidious oral flora Gram-negatives cause subacute native valve endocarditis with large vegetations and a tendency to embolise. Pasteurella multocida and Capnocytophaga are zoonotic Gram-negatives associated with animal bites, not classical culture-slow endocarditis. With modern continuous-monitoring systems most HACEK cultures turn positive within five days.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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