Background. Pneumocystis jirovecii pneumonia (PJP) is an important infection-related complication, whose mode of transmission remains uncertain.
Methods. We investigated a nosocomial cluster of 14 PJP cases (11 confirmed and 3 probable) in kidney transplant recipients using epidemiological and genotyping methods.
Results. Poisson regression calculated an incidence density ratio of 42.8 (95% confidence interval [CI], 14.1–129.3) versus background 0.64 cases of 1000 patient-years (P<0.001). All patients presented with respiratory failure, 10 required ventilation, two died, and six transplants failed, costing $31,854 (±SD $26,048) per patient. Four-locus multilocus sequence typing analysis using DNA extracts from 11 confirmed cases identified two closely related genotypes, with 9 of 11 sharing an identical composite multilocus sequence typing genotype. Contact tracing found colocalization of cases within clinic waiting areas, suggesting person-to-person transmission. Minimal and maximal PJP incubation periods were 124±83 to 172±71 days, respectively. Oropharyngeal washes from outpatient staff and ambient air samples were negative for P. jirovecii DNA. Cohort analysis (14 cases vs. 324 unaffected clinic control patients) identified independent risk factors including previous cytomegalovirus infection (odds ratio [OR], 65.9; 95% CI, 7.9–550; P<0.001), underlying pulmonary disease (OR, 10.1; 95% CI, 2.3–45.0; P=0.002), and transplant dysfunction (OR=1.61 per 10 mL/min/1.73 m2, 95% CI, 1.15–2.25, P=0.006). The outbreak was controlled by reintroduction of trimethoprim/sulfamethoxazole prophylaxis to all potentially exposed clinic patients and its extension to 12 months in recent recipients.
Conclusions. Nosocomial PJP clusters are likely due to interhuman transmission by airborne droplets to susceptible hosts. Prompt recognition and a strategy of early preemptive blanket PJP prophylaxis to all exposed transplant clinic recipients from the third confirmed case are recommended to limit outbreak escalation.
1 Department of Renal Medicine, Westmead Hospital, Westmead, NSW, Sydney, Australia.
2 Centre for Infectious Diseases and Microbiology, Westmead Hospital, Westmead, NSW, Sydney, Australia.
3 The Molecular Mycology Research Laboratory, Westmead Millennium Institute, Westmead Hospital, Westmead, NSW, Sydney, Australia.
4 Sydney Medical School-Westmead, Westmead Hospital, The University of Sydney, Sydney, Australia.
The authors declare no funding or conflicts of interest.
5 Address correspondence to: Dr. Brian J. Nankivell, M.D., B.S., M.Sc., Ph.D., F.R.A.C.P., Department of Renal Medicine, Westmead Hospital, Westmead, 2145, NSW, Sydney, Australia.
L.P. participated in clinical data collection, contact tracing, manuscript preparation, and editing. S.C. participated in case verification, data collection, manuscript preparation, and editing. K.K. participated in clinical data collection, contact tracing, manuscript preparation, and editing. C.H. participated in laboratory diagnosis and manuscript preparation. C.F. participated in genotyping and manuscript preparation. W.M. participated genotyping and analysis, manuscript preparation, and editing. G.W. participated economic evaluation, manuscript preparation, and editing. B.J.N. participated in data collection and analysis, manuscript preparation, and editing.
Supplemental digital content (SDC) is available for this article. Direct URL, citations appear in the printed text, and links to the digital files are, provided in the HTML text of this article on the journal's Web site, (www.transplantjournal.com). A combined file of all SDC is available as SDC 1 (http://links.lww.com/TP/A551).
Received 19 July 2011. Revision requested 10 August 2011.
Accepted 16 September 2011.