*Purpose: Although post-transplant pneumocystis pneumonia (PCP) outbreaks have been reported from Asia, Australia and Europe, there are limited data from North America. We investigated transmissibility of Pneumocystis jirovecii among solid organ transplant (SOT) recipients and non-SOT patients.

*Methods: We investigated a PCP outbreak involving SOT recipients in a North American center from 2014-2016. We also conducted a case-control study to determine the increased risk SOT recipients. Controls were SOT patients without PCP and were matched for type of allograft and time of PCP occurrence (±6 months).We simultaneously evaluated the course of illness and outcome of PCP in non-SOT patients who were diagnosed with PCP in the same interval. Multilocus Sequence Typing (MLST) was performed on all PCP isolates from SOT and non-SOT patients.

*Results: A total of 15 SOT recipients (8 kidney, 4 heart, 2 liver and 1 kidney-pancreas recipients) developed PCP. No patient developed PCP prophylaxis breakthrough.8 renal and 1 liver transplant recipients (60%) developed late-onset PCP beyond completing 12-month prophylaxis. In the case-control study, 15 cases and 60 controls were included. Cases were more likely to have had allograft rejection (adjusted OR: 17.8, 95% CI: 1.87-169.4) or cytomegalovirus (CMV) infection (adjusted OR: 28.5,95% CI:3.0-272.1) within the 6 months prior to PCP diagnosis. We controlled the outbreak with implementation of life-long PCP prophylaxis in renal transplant recipients while other SOT patients continued routine 12-months prophylaxis. No SOT recipient was diagnosed with PCP in the subsequent 24 months.During the same time interval, 10 non-SOT patients (7 acquired immune deficiency syndrome [AIDS], 2 hematologic malignancy and 1 allogeneic hematopoietic stem cell transplant) were also diagnosed with PCP. MLST demonstrated only one genotype of P. jirovecii causing nosocomial PCP outbreak in SOT recipients. The genotype of P. jirovecii in non-SOT patients was different from SOT recipients. Despite treatment and adjunctive glucocorticoid therapy, 8/15 SOT recipients developed allograft failure while no patient with AIDS developed organ failure (p=0.0225).

*Conclusions: We report a nosocomial PCP outbreak with a distinct P. jirovecii genotype circulatingamong different SOT recipients over 2 years suggesting a common transmission pathway. Life-long prophylaxis of SOT patients at increased risk or targeted prophylaxis for at least 6 months after allograft rejection or CMV infection may decrease the risk.

« Back to 2019 American Transplant Congress