Bacteria most commonly involved in prosthetic valvular hea disease within 2 months of surgery is: March 2007

Ans. A: Staphylococcus epidermidis Staphylococci account for 20 to 30% of all cases of endocarditis in the elderly. The predominant species, Staphylococcus aureus, often causes nosocomial endocarditis. S. epidermidis is isolated in < 5% of patients with native valve endocarditis, but it is the most common cause of cases that involve prosthetic valves occurring early after surgery in elderly and in younger patients. Gram-negative aerobic bacilli and fungi cause 2 to 3% of all cases of endocarditis. Infections due to Bacteroides species and mixed infections are rare among the elderly.