Gianella, Sara

Kovacs, Joseph A.

Mueller, Nicolas J.

Oka, Shinichi

Sassi, Monica

Yazaki, Hirohisa

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Reply to Hauser et alTO THE EDITOR—We appreciate the letterby Hauser and colleagues [1] describingan outbreak of Pneumocystis pneumoniain Frankfurt [2]. The outbreak appears tobe caused by the same strain of Pneumo-cystis, which we have called the EuropeanRenal Transplant (ERT) strain, that we166 • CID 2013:56 (1 January) • CORRESPONDENCEhad previously shown was responsible foroutbreaks in Munich and Zurich [3–5].This observation reﬂects the importanceof strain typing, but also highlights theneed for well-conducted epidemiologicinvestigations to better understand thesource and mode of Pneumocystis infec-tion transmission in these populations.It is now clear from multiple reportsthat outbreaks of Pneumocystis pneumoniacan be caused by a single strain of the or-ganism, and that close contact among sus-ceptible individuals may be responsible forthe transmission of the organism andmain-tenance of the outbreak (reviewed in [6]).The Lyon outbreak appeared to involve 1of the most prevalent strains (based ontyping by single-strand conformationalpolymorphism analysis) [7], and thus mayhave simply reﬂected exposure to that strain.However, the available data argue againstthat explanation in these 3 related out-breaks, when it is taken into account thatnone of the 11 isolates (6 from Munich, 3from Zurich, and 2 from Frankfurt) obtain-ed contemporaneously from non-outbreakpatients were the ERT strain [1, 3].Only 4 isolates were sequenced, andthus it is possible that other Pneumocystisstrains were responsible for the additional26 cases identiﬁed in the Frankfurt out-break [2]. Nonetheless, it is striking that 3outbreaks of PCP in 3 cities approximate-ly 300 to 400 km apart were associatedwith a single strain of Pneumocystis. Weagree that typing of additional contempo-raneous isolates from endemic cases aswell as from individuals with subclinicalPneumocystis infection would be neededto clarify the epidemiology. However,since these outbreaks occurred approxi-mately 5–7 years ago, it would be verydifﬁcult to obtain such samples or retro-spectively perform a detailed epidemio-logic investigation to try to identifysources of infection that may have linkedthe outbreaks. Based on these observa-tions, it is critical that future outbreaks bediligently investigated so that we maybetter understand the sources of infectionand the mode of transmission, and todetermine if the ERT strain or otherstrains are associated with multiple out-breaks. We currently do not have thetools to readily identify and study viru-lence factors due to an inability to culturethe organism and a lack of a genome se-quence for P. jirovecii. However, oncethese tools become available, they need tobe applied to better understand thebiology of this infection. Until then, wefeel that strain typing plays an importantrole in elucidating the transmission dy-namics of Pneumocystis infection.NotesFinancial support. This researchwas suppor-ted in part by the Intramural Research Program ofthe National Institutes of Health Clinical Center.Potential conﬂicts of interest. All authors:No reported conﬂicts.All authors have submitted the ICMJE Formfor Disclosure of Potential Conﬂicts of Interest.Conﬂicts that the editors consider relevant to thecontent of the manuscript have been disclosed.Monica Sassi,1 Nicolas J. Mueller,2Hirohisa Yazaki,3 Shinichi Oka,3,4Sara Gianella,2 and Joseph A. Kovacs11Critical Care Medicine Department, NationalInstitutes of Health Clinical Center, Bethesda,Maryland; 2Division of Infectious Diseases andHospital Epidemiology, University Hospital Zurich,Switzerland; 3AIDS Clinical Center, National Centerfor Global Health and Medicine, Tokyo, Japan; and4Division IX, Center for AIDS Research, KumamotoUniversity, JapanReferences1. Hauser PM, Rabodonirina M, Nevez G.Pneumocystis jirovecii genotypes involved inPCP outbreaks among renal transplant recip-ients [published online ahead of print 18September 2012]. Clin Infect Dis 2012;56:165–6.2. Pliquett RU, Asbe-Vollkopf A, Hauser PM,et al. A Pneumocystis jirovecii pneumoniaoutbreak in a single kidney-transplant center:role of cytomegalovirus co-infection.Eur J Clin Microbiol Infect Dis 2012; 31:2429–37.3. Sassi M, Ripamonti C, Mueller NJ, et al. Out-breaks of Pneumocystis pneumonia in 2 renaltransplant centers linked to a single strain ofPneumocystis: implications for transmissionand virulence. Clin Infect Dis 2012; 54:1437–44.4. Gianella S, Haeberli L, Joos B, et al. Molecu-lar evidence of interhuman transmission inan outbreak of Pneumocystis jiroveciipneumonia among renal transplant recipi-ents. Transpl Infect Dis 2010; 12:1–10.5. Schmoldt S, Schuhegger R, Wendler T, et al.Molecular evidence of nosocomial Pneumo-cystis jirovecii transmission among 16 patientsafter kidney transplantation. J Clin Microbiol2008; 46:966–71.6. de Boer MGJ, de Fijter JW, Kroon FP. Out-breaks and clustering of Pneumocystispneumonia in kidney transplant recipients:a systematic review. Med Mycol 2011; 49:673–80.7. Rabodonirina M, Vanhems P, Couray-TargeS, et al. Molecular evidence of interhumantransmission of Pneumocystis pneumoniaamong renal transplant recipients hospital-ized with HIV-infected patients. Emerg InfectDis 2004; 10:1766–73.Correspondence: Joseph A. Kovacs, MD, Bldg 10, Rm 2C145,MSC 1662, Bethesda, Maryland 20892-1662 (jkovacs@mail.nih.gov).Clinical Infectious Diseases 2013;56(1):166–7Published by Oxford University Press on behalf of the InfectiousDiseases Society of America 2012.DOI: 10.1093/cid/cis814CORRESPONDENCE • CID 2013:56 (1 January) • 167

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