An outbreak of Pneumocytis jirovecii pneumonia among liver transplant recipients.

BACKGROUND: An outbreak of Pneumocystis pneumonia (PCP) in liver transplant recipients occurred between 2009 and 2011 at the Beaujon University Hospital just after immediate-release tacrolimus was replaced by extended-release tacrolimus. We conducted a retrospective study to analyze the transmission mode of Pneumocystis, the role of the change in the immunosuppressive regimen, and the factors associated with PCP. PATIENTS AND METHODS: To analyze transmission, we built a transmission map. Two control groups were built. First, to assess the role of the change from tacIR to tacER, cases were matched to controls transplanted before 2009 (tacIR control group). Tacrolimus trough concentrations were compared between the 2 groups. Then, to assess factors associated with PCP, each PCP case was matched to 2 control patients: the one transplanted just before and the one just after (PCPAsFact control group). No PCP prophylaxis was given to any patient. RESULTS: Fifteen cases of PCP were recorded. A contact between a case and a patient who developed PCP afterward was identified in 4 occasions. The comparison of tacrolimus trough concentrations did not conclude to a difference in the exposure to the drug. Lymphopenia was the only factor independently associated with the occurrence of PCP (odds ratio 0.78, 95% confidence interval 0.61-0.99, P = .04). CONCLUSION: Our results suggest that patient-to-patient transmission was not the main mode of transmission of PCP. We found no evidence that the switch from tacIR to tacER led to an overexposure to tacrolimus. Our results suggest the possibility of targeted prophylaxis in immunosuppressed liver transplant recipients.