Outbreaks and clustering of Pneumocystis

several continents. The pathogenesis of these outbreaks has not been clarifi ed and different explanations, e.g., changes in the standard immunosuppressive regimen, an environmental source or patient-to-patient transmission have been proposed [2 – 4]. Recent outbreaks occurred in the absence of chemoprophylaxis, while in general the prescription of trimethoprim-sulfamethoxazole (TMP-SMX) to prevent PCP for at least a duration of 3 – 6 months after kidney transplantation now is a widely accepted prac-tice and incorporated in several kidney transplantation guidelines [5,6]. During the fi rst observations of clusters of PCP in kidney transplant units in the 1980s, where transplant recipients were hospitalized together with AIDS patients, the possibility of patient-to-patient transmission and a rela-tion with the developing HIV epidemic in the northern hemisphere in general was proposed [7]. Outbreaks amon