Solid Organ Transplantation

Pathogenesis: After solid organ transplantation, pts do not go through a stage of neutropenia like that seen after HSCT; thus the infections in these two groups of pts differ. However, solid organ transplant recipients are immunosuppressed for longer periods with agents that chronically impair T-cell immunity. Moreover, the persistent HLA mismatch between recipient immune cells (e.g., effector T cells) and the donor organ (allograft) places the organ at permanently increased risk of infection.
Etiology: As in HSCT, the infection risk depends on the interval since transplantation.
- - Early infections (<1 month): Infections are most commonly caused by extracellular organisms, which originate in surgical wound or anastomotic sites.
- - Middle-period infections (1-6 months): The consequences of suppressing cell-mediated immunity become apparent, and infections result from acquisition—or reactivation—of viruses, mycobacteria, endemic fungi, and parasites.
  - CMV can cause severe systemic disease or infection of transplanted organs; the latter increases the risk of organ rejection, prompting increased immunosuppression that, in turn, increases CMV replication.
  - Diagnosis, treatment, and prophylaxis of CMV infection are the keys to interrupting this cycle.
- - Late infections (>6 months): Infections in this period are similar to those in pts with chronically impaired T-cell immunity (e.g., Listeria, Nocardia, Rhodococcus, mycobacteria, various fungi, other intracellular organisms).
  - EBV lymphoproliferative disease occurs most commonly in pts who receive a heart or lung transplant (as well as the most intense immunosuppressive regimens); in these cases, immunosuppression should be decreased or discontinued, if possible, and consideration should be given to treatment with anti-B cell antibodies.
  - Prophylaxis against Pneumocystis pneumonia for at least 1 year is generally recommended for all solid organ transplant recipients.
  - The incidence of tuberculosis within the first 12 months after solid organ transplantation is greater than that after HSCT and reflects the prevalence of tuberculosis in the local population.
Specific issues: While the above information is generally valid for all organ transplants, there are some organ-specific considerations.
- - Kidney transplantation: TMP-SMX prophylaxis for the first 4-6 months decreases the incidence of early and middle-period infections, particularly UTIs related to anatomic alterations resulting from surgery. CMV is the predominant pathogen in the middle period; disease is evident in 50% of renal transplant pts presenting with fever 1-4 months after transplantation, prompting many centers to use valganciclovir prophylaxis for high-risk pts. BK viruria and viremia, often diagnosed as a late-onset disease, are associated with ureteral strictures, nephropathy, and vasculopathy and require a reduction of immunosuppression to lower rates of graft loss.
- - Heart transplantation: Mediastinitis, generally caused by typical skin flora and rarely caused by Mycoplasma hominis, is an early complication of heart transplantation. The overall incidence of toxoplasmosis (a middle-period infection) is so high in the setting of heart transplantation that serologic screening and some prophylaxis (e.g., TMP-SMX) are always warranted.
- - Lung transplantation: Pts receiving a lung transplant are predisposed to pneumonia and mediastinitis in the early period. The high incidence of CMV disease (75-100% if either the donor or the recipient is seropositive) indicates the importance of antiviral prophylaxis; late disease may occur once prophylaxis is discontinued, although the pt is generally better able to handle it because of reduced immunosuppression.
- - Liver transplantation: Bacterial abscesses and peritonitis are common early complications and often result from biliary leaks. Pts receiving a liver transplant have a high incidence of fungal infections correlated with preoperative glucocorticoid use, long-term antimicrobial use, and a high degree of immunosuppression. Recurrent (reactivated) hepatitis B and C infections are problematic; while hepatitis B immunoglobulin administration and prophylaxis with antiviral agents active against hepatitis B virus have been successful in preventing reinfection with hepatitis B virus, reinfection with hepatitis C virus occurs in all pts.

section name header

Information ⬇

Outline ⬆