This patient's level of immunosuppression must be increased for this episode of acute rejection, and therefore prophylaxis for Pneumocystis jirovecii infection should be reinitiated. Because of defects in cell-mediated immunity resulting from antirejection drugs, patients who have undergone transplantation are at high risk for P. jirovecii infection and are usually treated with prophylaxis for Pneumocystis infection, especially for the first 6 to 12 months when immunosuppression is given at higher levels. Long-term prophylaxis is not typically required when immunosuppression for the transplant can be minimized. However, these patients are also at increased risk beyond the first year if episodes of rejection require increases in immunosuppression, such as in this patient. It is thus important to reinstitute prophylaxis for Pneumocystis infection under these circumstances, even if increased immunosuppression is temporary. Trimethoprim-sulfamethoxazole is the preferred prophylactic agent in most patients without a contraindication.

Pulmonary aspergillosis is more likely to occur in the neutropenic period after hematopoietic stem cell transplantation or after lung transplantation; it would be uncommon in a patient after other solid organ transplantation, and prophylaxis is not indicated.

Both recipient and donor in this case were seronegative for cytomegalovirus before transplantation and thus cytomegalovirus disease is unlikely, even with increased immunosuppression, and prophylaxis is not necessary.

In contrast to the high risk in patients with advanced AIDS, Mycobacterium avium complex infection is unusual after transplantation, and prophylaxis against this is not indicated.