Chapter 126. Infections in Transplant Recipients (Part 2) In many transplantation centers, transmission of infections that may be latent or clinically inapparent in the donor organ has resulted in the development of specific donor-screening protocols. In addition to ordering serologic studies focused on viruses such as herpes-group viruses [herpes simplex virus types 1 and 2 (HSV-1, HSV-2), varicella-zoster virus (VZV), cytomegalovirus (CMV), human herpesvirus (HHV) type 6, Epstein-Barr virus (EBV), and Kaposi's sarcoma– associated herpesvirus (KSHV)] as well as hepatitis B and C viruses, human immunodeficiency virus (HIV), human T cell lymphotropic virus type I, and West Nile virus, donors should be screened for parasites such as Toxoplasma gondii and Trypanosoma cruzi (the latter particularly in Latin America). Clinicians caring for prospective organ donors should also consider assessing stool for parasites, should examine chest radiographs for evidence of granulomatous disease, and should perform purified protein derivative (PPD) skin testing or obtain blood for immune cell–based assays that detect active or latent Mycobacterium tuberculosis infection. An investigation of the donor's dietary habits (e.g., consumption of raw meat or fish or of unpasteurized dairy products), occupations or avocations (e.g., gardening or spelunking), and travel history (e.g., travel to areas with endemic fungi) is also mandatory. It is expected that the recipient will have been likewise assessed. Because of immune dysfunction resulting from chemotherapy or underlying chronic disease, however, direct testing of the recipient may prove less reliable. This chapter considers aspects of infection unique to various transplantation settings. Infections in Hematopoietic Stem Cell Transplant (HSCT) Recipients Transplantation of hematopoietic stem cells from bone marrow or from peripheral or cord blood for cancer, immunodeficiency, or autoimmune disease results in a transient state of complete immunologic incompetence. Immediately after transplantation, both phagocytes and adaptive immune cells (T and B cells) are absent, and the host is extremely susceptible to infection. The reconstitution that follows transplantation has been likened to maturation of the immune system in neonates. The analogy does not entirely predict infections seen in HSCT recipients, however, because the new cells mature in an old host who has several latent infections already. Nevertheless, most infections occur in a predictable time frame after transplantation (Table 126-2). Table 126- 2 Common Sources of Infections after Hematopoietic Stem Cell Transplantation Period after Transplantation Infection Site Early (<1 Month) Middle (1– 4 Months) Late (>6 Months) Disseminated Aerobic gram-negative, gram-positive bacteria Nocardia Candida, Aspergillus Encapsulated bacteria (Streptococcus pneumoniae , Haemophilus influenzae, Neisseria meningitidis) Skin and mucous membranes HSV HHV-6 VZV Lungs Candida , Aspergillus HSV CMV, seasonal respiratory viruses Pneumocystis Toxoplasma Pneumocystis Gastrointestinal tract CMV Kidney BK virus, adenovirus BK virus Brain HHV-6 Toxoplasma Toxoplasma JC virus Bone marrow HHV-6 Note: CMV, cytomegalovirus; HHV- 6, human herpesvirus type 6; HSV, herpes simplex virus; VZV, varicella-zoster virus. . Chapter 126. Infections in Transplant Recipients (Part 2) In many transplantation centers, transmission of infections that may be latent or clinically inapparent in the donor. cells mature in an old host who has several latent infections already. Nevertheless, most infections occur in a predictable time frame after transplantation (Table 126- 2). Table 126- 2 Common. to infection. The reconstitution that follows transplantation has been likened to maturation of the immune system in neonates. The analogy does not entirely predict infections seen in HSCT recipients,