The major goal of Opportunistic Infections: Treatment and Prophylaxis is to guide cli- cians who provide care for patients suffering from an underlying immunodeficiency that may significantly weaken their immune defenses and will complicate the effective treatment of opportunistic infections. In spite of a wealth of isolated data, no single text exists in which all the essential information about various infectious opportunistic infections. Although I make no claim to completeness, it is my hope that the present book will fulfill that need. To achieve this goal, I have endeavored to integrate both results from large-scale clinical trials and trials involving small numbers of patients, as well as reports of single cases—mindful that such an approach has its limitations. Opportunistic Infections: Treatment and Prophylaxis is organized into four major parts: bacterial, viral, parasitic, and fungal diseases affecting the immunocompromised population. Each part surveys individual infections caused not only by well-known etiologic agents, but also by new and emerging species often taxonomically closely related to a major disea- producing microorganism and until recently not considered to be human pathogens (Candida spp. and nontuberculous mycobacteria, for example). For the sake of uniformity, within each part, the species have been arranged according to their taxonomic characteristics.