Endocarditis due to Pseudomonas aeruginosa in a heroin addict. Successful treatment with trimethoprim-Sulfamethoxazole mixture plus colistin.

Endocarditis of the tricuspid valve due to Pseudomonas aeruginosa in a heroin addict failed to respond to therapy with gentamicin, carbenicillin, and amikacin. Clinical and bacteriologic cure was achieved with oral administration of a trimethoprim-sulfamethoxazole mixture plus parenteral therapy with colistin. In vitro synergism was demonstrated for the three drugs at concentrations achievable in the serum. Therapy for endocarditis due to Pseudomonas continues to be a major problem; however, the successful treatment of this patient warrants consideration for instituting therapy with a trimethoprim-sulfamethoxazole misture plus colistin in individuals with this infection who fail to respond to standard therapeutic regimens for severe infections with Pseudomonas.