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Volume 9, Number 2—February 2003

Pneumocystis carinii versus Pneumocystis jiroveci: Another Misnomer (Response to Stringer et al.)

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To the Editor: The proposal by Stringer et al. to change the name of Pneumocystis carinii found in humans to Pneumocystis jirovec requires critical consideration (1). First, their rationale for the choice of Jírovec is not compelling. Principle III of the International Code of Botanical Nomenclature (ICBN) states: “the nomenclature of a taxonomic group is based upon priority of publication” (2). Jírovec’s publication in 1952 was not the first to report P. carinii infection in human lungs. In 1942, two Dutch investigators, van der Meer and Brug, described P. carinii as the infecting organism in a 3-month-old infant with congenital heart disease and in 2 of 104 autopsy cases (a 4-month-old infant and a 21-year-old adult) (3). Their description, photomicrographs, and drawings of P. carinii are unequivocal. They also described the typical “honeycomb” patterns in alveoli. In 1951, Dr. Josef Vanek at Karls-Universität in Praha, Czechoslovakia, reported his study of lung sections from 16 children with interstitial pneumonia and demonstrated that the disease was caused by P. carinii (4). Vanek notes in his report, “In man the parasite was for the first time established as a cause of pneumonia in a child by G. Meer and S. L. Brug (1942).” In 1952, Jírovec reported P. carinii as the cause of interstitial plasmacellular pneumonia in neonates (5). A year later, in a coauthored publication, Vanek, Jírovec, and J. Lukes acknowledged and referenced the earlier reports of van der Meer and Brug and Vanek (6). If principle III is to be followed, as well as fairness to the investigators, both van der Meer and Brug and Vanek hold priority over Jírovec, assuming the designation of the species name should be based on the name of the first person to discover P. carinii in humans.

The nomenclature of P. carinii has actually been fraught with errors from the beginning. In the earliest publications, Carlos Chagas and Antonio Carini mistook the organism for stages in the life cycle of trypanosomes. Chagas placed it in a new genus, Schizotrypanum (7,8). In 1912, Delanoë and Delanoë at the Pasteur Institute in Paris published the first description of the organism as a new entity unrelated to trypanosomes (9). They proposed the name “Pneumocystis carinii” as a tribute to Carini. The Delanoë paper has remained unchallenged as the original description of P. carinii. Both Chagas and Carini later acknowledged their errors and the validity of the Delanoës’ conclusion. By current ICBN principles, P. carinii is acceptable nomenclature because the authors of the first publication proposed the name of Carini, rather than their own.

In addition, changing the name to P. jiroveci will create confusion in clinical medicine where the name P. carinii has served physicians and microbiologists well for over half a century. I was moved to write this letter because of a call from a knowledgeable oncologist asking for information on “the new strain of P. carinii that has just been reported from the Centers for Disease Control and Prevention,” referring to the report by Stringer et al (1).

AIDS patients are well informed about P. carinii pneumonia and avidly monitor medical news about their disease. Without doubt, the name change will cause confusion and undue anxiety among the many thousands of HIV-infected patients who attend clinics. Health-care workers will have an added burden of explaining why the name was changed, but the organism and infection are unchanged. Also, versions of the pronunciation of jiroveci (yee row vet zee) by American patients, physicians, and health-care workers will be interesting to hear.

The tone of the article by Stringer et al. implies that the change of P. carinii to P. jiroveci is final, which is not the case. The nomenclature of fungi is governed by ICBN under the auspices of the International Botanical Congress and is not based solely on molecular genetics. Neither P. carinii nor P. jiroveci have been submitted for ICBN scrutiny. In another paper, Stringer et al. outline the mechanics for submission, but indicate that no application has been submitted for their proposal (10). In fact, P. carinii has not been acknowledged as a fungus by ICBN or any other authoritative taxonomic system. Only when nomenclature is registered in ICBN, can a name be referred to as “formally accepted.” In the meantime, the workable terminology proposed earlier by Stringer et al. in 1994 (11) will suffice for clinical use.


Walter T. Hughes*Comments to Author 
Author affiliation: *St. Jude Children’s Research Hospital, Memphis, Tennessee, USA



  1. Stringer  JR, Beard  CB, Miller  RF, Wakefield  AE. A new name (Pneumocystis jiroveci) for Pneumocystis from humans. Emerg Infect Dis. 2002;8:8916.PubMedGoogle Scholar
  2. Editorial Committee, International Botanical Congress. International Code of Botanical Nomenclature (St. Louis Code). Konigstein, Germany: Koeltiz Scientific Books; 2000.
  3. van der Meer  MG, Brug  SL. Infection à Pneumocystis chez l’homme et chez les animaux. Ann Soc Belg Med Trop. 1942;22:3019.
  4. Vanek  J. Atypicka (interstitiálni) pneumonie detí vyvolaná Pneumocystis carinii (atypical interstitial pneumonia of infants produced by Pneumocystis carinii). Casop lék cesk 1951;90:1121–4.
  5. Jírovec  O. Pneumocystis carinii puvodce t. zv intertitialnich plasmocelularnich pneumonii kojencw (Pneumocystis carinii, the cause of interstitial plasmacellular pneumonia in neonates) Csl. Hyg epid mikrob 1952;1:141.
  6. Vanek  J, Jírovec  O, Lukes  J. Interstitial plasma cell pneumonia in infants. Ann Paediatr. 1953;180:121.PubMedGoogle Scholar
  7. Chagas  C. Uber eine neue Trypoanosomiasis des Menschen. Mem Inst Oswaldo Cruz. 1909;3:1218.
  8. Carini  A. Formas des eschizogonia do Trypanosoma lewisi. Soc Med Cir São Paulo. 1910;38:8.
  9. Delanoë  P, Delanoë  M. Sur les rapports des kystes de Carini du poumon des rats avec le Trypanosoma lewisi. Comptes rendus de “l’Academie des sciences. 1912;155:658–61.
  10. Stringer  JR, Cushion  MT, Wakefield  AE. New nomenclature for the genus Pneumocystis. J Eukaryot Microbiol. 2001;Suppl:1849. DOIGoogle Scholar
  11. Stringer J and the Pneumocystis Workshop. Revised nomenclature for Pneumocystis carinii. J Eukaryot Microbiol. 1994;41:1212.


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DOI: 10.3201/eid0902.020602

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Please use the form below to submit correspondence to the authors or contact them at the following address:

Walter T. Hughes, Emeritus Member, Department of Infectious Diseases, St. Jude Children’s Research Hospital, 332 N. Lauderdale St., Memphis, TN 38105-2794, USA; fax: 901-495-5068

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The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.