Prosthetic valve endocarditis by opportunistic pathogens.

The incidence of endocarditis produced by the so-called "opportunists" as a complication of prosthetic valve surgery is progressively increasing in frequency and gradually transforming the clinical picture habitually associated with this disease. We report six cases of endocarditis produced by opportunistic microorganisms (two cases by Candida, and the remaining by Serratia, Actinobacillus, Acinetobacter calcoaceticus, and Bacteroides fragilis, and by Corynebacterium diphtheriae) in four male and two female patients, making special comment on our findings, diagnostic criteria, and treatment. The patients' ages ranged from 9 to 54 years, and all six patients had long-term complications, with symptoms appearing between 45 days and four years after prosthetic valve surgery. The progressive increase of this new type of prosthesis infection is favored by the indiscriminate use of certain drugs and especially by the prophylactic use of antibiotics.