BOSTON—National guidelines from the American Society of Transplantation recommend antibiotic prophylaxis against Pneumocystis jiroveci pneumonia for at least six months after renal transplantation. Findings from a new study, however, suggest that just one month may be adequate.

“Patients after renal transplant are taking a lot of drugs, and I am sure they would rather take less drugs; eliminating one drug may perhaps improve their ability to take all their other medications that they have to take to prevent rejection of their kidney,” said study investigator Daniel Kaul, MD, Assistant Professor of Internal Medicine in the Division of Infectious Diseases at the University of Michigan in Ann Arbor. In addition, a shorter course of prophylaxis would yield cost savings, lower the risk of the development of drug-resistant bacteria, and reduce the risk of toxicities such as low blood counts and hyperkalemia, Dr. Kaul noted.

PCP occurs in up to 41% of renal transplant recipients who do not receive prophylaxis. At his institution, renal transplant recipients only receive four weeks of post-transplant trimethoprim/sulfamethoxazole (TMP/SMX) even though national guidelines call for six months. Dr. Kaul and his colleagues examined rates of P. jiroveci pneumonia in 1,352 renal transplant and renal-pancreas transplant patients receiving four weeks of prophylaxis with TMP/SMX. This antibiotic combination also provides limited protection against Nocardia, so the researchers also looked at nocardiosis rates.

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The team identified two pneumocystis pneumonia cases within 12 months post-transplantation and two additional cases more than 12 months post-transplantation, for an attack rate of 0.3%. Two cases of nocardiosis were identified within 12 months of transplantation and two more cases more than 12 months after transplantation. All cases of pneumocystis pneumonia and nocardiosis involved patients who received induction therapy (seven of the eight patients received thymoglobulin). Approximately one half of all renal transplant recipients received induction therapy.

None of the patients with pneumocystis pneumonia was treated for rejection within six months of contracting the disease. Three of the four patients with pneumocystis pneumonia had recent cytomegalovirus (CMV) infection. All patients with pneumocystis pneumonia and three of the four patients with nocardiosis survived.

The investigators concluded that, given their very low rate of both pneumocystis pneumonia and nocardiosis, a TMP/SMX course longer than one month may not be warranted. Possible explanations for the low rate of infection compared with historical data include activity of mycophenolate against P. jiroveci, prolonged effect of one month of prophylaxis on P. jiroveci carriage, or other unidentified local or geographic factors.

“We are not advocating avoiding pneumocystis prophylaxis in general, but physicians may have particular patients who have difficulty tolerating prophylaxis,” Dr. Kaul told Renal & Urology News. “So, it may be reasonable in those situations to discontinue prophylaxis [after one month].”

He acknowledged that the study has limitations. For example, local factors at their institution could have influenced study findings. “But I think our study does challenge the current dogma that extended courses are required,” he said. “Other centers may want to look at their particular practices.”