In 2013 and 2014, four Pneumocystis jirovecii pneumonia (PJP) outbreaks occurred among renal transplant recipient cohorts in three academic hospitals in Quebec, Canada. We investigated the outbreaks seeking to: 1) Determine risk factors associated with development of PJP, and 2) elucidate the likely mode of transmission.
Methods: A case-control study was conducted. Cases were defined as patients who had undergone kidney transplantation in one of the three centers and who were diagnosed with proven PJP during outbreak periods. Controls were randomly selected among all patients followed through outpatient transplant clinics during the outbreak periods. Bronchoalveolar lavage samples from 16 cases were available and used for PJ genotyping by multilocus sequence typing. Air samples were collected for detection of PJ DNA (mitochondrial large subunit RNA gene) using real-time polymerase chain reaction.
A total of 22 cases and 88 control patients were identified. Genotyping confirmed isolate clonality within each outbreak. The cases occurred a median of 112 months after transplantation. None of the cases was receiving targeted PJP prophylaxis at time of diagnosis. Independent risk factors for developing PJP included administration of anti-thymocyte antibodies after the transplant (adjusted odds ratio [aOR] 4.73, 95% confidence interval [95% CI] 1.12-19.89), glomerular filtration rate <30 mL/min (aOR 4.65, 95% CI 1.22-17.78), and absolute lymphocyte counts below 1,000 (aOR 5.53, 95% CI 1.40-21.94). Analysis of contacts in the outpatient clinic showed an increased tendency for cases to have attended the outpatient clinic the same day as a future (within two months) case of PJP (OR 1.56, 95% CI 0.59-4.13). Air sampling carried out in one center also showed the presence of PJ DNA in outpatient transplant clinic samples.
Conclusion: The development of PJP is associated with host risk factors that translate to increased immunosuppression. Collectively, the molecular and epidemiological data support person-to-person transmission of the disease, possibly via airborne particles. This study underlines the need for prophylaxis in certain contexts and the importance of avoiding close contact between patients with PJP and other susceptible hosts.
P. Dufresne, None
A. Carignan, None