Pneumocystis pneumonia (PCP) is an opportunistic infection occurring in renal transplant patients. Over a 14-month period an increase in PCP cases was identified among our renal transplant cohort.

The outbreak population was studied to identify potential risk factors for the development of PCP.

A retrospective analysis of hospital records was carried out, with each case being matched with two case-linked controls. Information was collected on patient demographics, laboratory tests, and hospital visits pre and post development of infection.

No patients were receiving PCP prophylaxis at the time of infection and mean time from transplantation to developing PCP was 4.7 years (range: 0.51–14.5). The PCP group had a significantly lower mean estimated glomerular filtration rate than the control group (29.3 mL/min/1.73 m² vs 70 mL/min⁻¹ (P = 0.0007)). Three patients were treated for active cytomegalovirus (CMV) infection prior to PCP diagnosis and two had active CMV at the time of diagnosis compared to none in the control group (P = 0.001). Those who developed PCP were more likely to have shared a hospital visit with another patient who went on to develop PCP; 37% of clinic visits vs 19% (P = 0.014).

This study highlights the ongoing risk of opportunistic infection several years after transplantation and adds weight to potential person-to-person Pneumocystis jirovecii transmission. Risk factors have been identified which may highlight those most at risk, enabling targeted rather than blanket long-term PCP prophylaxis.