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Journal of Clinical Microbiology, July 2008, p. 2469-2470, Vol. 46, No. 7
0095-1137/08/$08.00+0     doi:10.1128/JCM.00510-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

LETTER TO THE EDITOR

Nocardia cyriacigeorgica—an Established Rather than an Emerging Pathogen

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In their recent report, Schlaberg et al. declare Nocardia cyriacigeorgica to be an "emerging pathogen" (3). However, no evidence is provided to support this claim. They refer to the review by Millar and Moore (2) for a definition of "an emerging pathogenic entity" but do not specify into which of the categories of emerging and reemerging pathogens distinguished by these authors they would place N. cyriacigeorgica. The only possibly applicable category would seem to be that of "an increase in reporting of novel pathogens as a result of improved identification and diagnosis such as those based on molecular techniques." The key word here, however, is "novel," and in a recent report also cited by Schlaberg et al., organisms previously described as members of Nocardia asteroides drug pattern VI were demonstrated by DNA-DNA hybridization to belong to the species N. cyriacigeorgica (1). In that publication, it was explicitly stated that N. cyriacigeorgica "is not a ‘new’ organism or an ‘emerging’ pathogen; rather, it is a newly named but long-recognized agent of human disease." In the initial report describing six different "drug patterns" of N. asteroides (plus an additional "miscellaneous" group which included the N. asteroides type strain [ATCC 19247^T]) (4), N. asteroides drug pattern type VI was recognized as the most common of the clinical nocardial isolates studied. Therefore, N. cyriacigeorgica is not "novel" and we are not aware of any data suggesting that its incidence is increasing.

Schlaberg et al. introduce additional confusion by referring to the "N. asteroides drug pattern VI type strain ATCC 14759^T." This strain should be referred to as a "reference strain," not a type strain. Type strains can only be designated for species named and described according to the accepted nomenclatural rules, and "N. asteroides drug pattern type VI" is not such a name. The type strain for the species to which the organism "N. asteroides drug pattern type VI" belongs is N. cyriacigeorgica DSM 44484^T.

Our concerns may seem trivial to many. But the taxonomy of the genus Nocardia (and indeed of numerous other bacterial genera) is becoming increasingly complex as more and more species are delineated, often by dividing a previously recognized species into two or more species. Increasing diligence is thus required to assure that whatever clinically or otherwise useful information has been accumulated continues to be associated with the appropriate taxonomic entity.

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1. Conville, P. S., and F. G. Witebsky. 2007. Organisms designated as Nocardia asteroides drug pattern type VI are members of the species Nocardia cyriacigeorgica. J. Clin. Microbiol. 45:2257-2259.[Abstract/Free Full Text]
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2. Millar, B. C., and J. E. Moore. 2006. Emerging pathogens in infectious diseases: definitions, causes and trends. Rev. Med. Microbiol. 17:101-106.
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3. Schlaberg, R., R. C. Huard, and P. Della-Latta. 2008. Nocardia cyriacigeorgica, an emerging pathogen in the United States. J. Clin. Microbiol. 46:265-273.[Abstract/Free Full Text]
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4. Wallace, R. J., Jr., L. C. Steele, G. Sumter, and J. M. Smith. 1988. Antimicrobial susceptibility patterns of Nocardia asteroides. Antimicrob. Agents Chemother. 32:1776-1779.[Abstract/Free Full Text]

						Frank G. Witebsky Patricia S. Conville* Microbiology Service Department of Laboratory Medicine Warren G. Magnuson Clinical Center National Institutes of Health Department of Health and Human Services Bethesda, MD 20892-1508 Richard J. Wallace Jr. Barbara A. Brown-Elliott University of Texas Health Center Department of Microbiology Tyler, Texas
						* Phone: (301) 402-1891 Fax: (301) 402-1886 E-mail: pconville{at}nih.gov

Authors' Reply

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We are grateful for the opportunity to respond to the letter by Witebsky et al. commenting on our recent publication (1). They note that in our paper we refer to strain ATCC 14759 as the "type" strain for the N. asteroides complex drug pattern type VI (hereafter referred to as pattern VI) classification, when in fact it is simply a reference strain for isolates with a pattern VI antimicrobial susceptibility pattern. It is true that the pattern VI strain has not been recognized as a "type" strain by the international bodies which establish such rules (4). Nor is it denoted as a "type" strain in the ATCC catalogue (www.atcc.org), although as of this writing it remains listed as "Nocardia asteroides." The difference between a "type" strain and a reference strain is most definitely an important distinction. As people come to accept the assimilation of the pattern VI designation into N. cyriacigeorgica, we hope this error will have little impact in the long run.

Witebsky et al. have also taken exception to our characterization of N. cyriacigeorgica as an emerging pathogen. We chose to refer to this pathogen as emerging by following suggestions cited in a recent review by Millar and Moore in which many categories of emerging pathogens are described (2). An important take-home message of Millar and Moore's review is that the term "emerging pathogen" has evolved and expanded beyond its original limited definition. Indeed, we prefer a broader interpretation of "emerging pathogen" to also include those agents that (i) are known to exist elsewhere in the world but which are causing disease in a new locale (i.e., the United States in this case) and (ii) may have been a cause of disease for some time but that we are only now beginning to recognize and distinguish. We agree with Witebsky et al. that N. cyriacigeorgica is not a novel pathogen, as it has been described as a cause of disease in many other countries. However, we do consider it an emerging pathogen in the United States for the following further reasons. First, N. cyriacigeorgica has yet to be definitively proven to encompass all pattern VI strains. Indeed, to the best of our knowledge, a comparative evaluation of the two by a combined molecular and phenotypic approach has not been done using a critical sample size of strains. Second, N. cyriacigeorgica remains to become established and distinguished from N. asteroides within the collective consciousness of the North American medical establishment. By these criteria, we therefore feel that we are justified in characterizing N. cyriacigeorgica, for the time being, as emergent in the United States.

Lastly, we are in agreement that a correct taxonomical delineation of N. cyriacigeorgica/pattern VI strains is an important intellectual and epidemiological endeavor with real clinical implications, especially given that a correct nocardial species level identification can help guide the choice of treatment and predict patient outcome. Rather than introducing further confusion, our combined publications (1, 3) go far to clarify the taxonomy of N. cyriacigeorgica and finger a species that is (probably) a major cause of serious nocardiosis in the United States.

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1. Conville, P. S., and F. G. Witebsky. 2007. Organisms designated as Nocardia asteroides drug pattern type VI are members of the species Nocardia cyriacigeorgica. J. Clin. Microbiol. 45:2257-2259.[Abstract/Free Full Text]
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2. Millar, B. C., and J. E. Moore. 2006. Emerging pathogens in infectious diseases: definitions, causes and trends. Rev. Med. Microbiol. 17:101-106.
3
3. Schlaberg, R., R. C. Huard, and P. Della-Latta. 2008. Nocardia cyriacigeorgica, an emerging pathogen in the United States. J. Clin. Microbiol. 46:265-273.[Abstract/Free Full Text]
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4. Tindall, B. J., P. Kämpfer, J. P. Euzéby, and A. Oren. 2006. Valid publication of names of prokaryotes according to the rules of nomenclature: past history and current practice. Int. J. Syst. Evol. Microbiol. 56:2715-2720.[Abstract/Free Full Text]

						Richard C. Huard Clinical Microbiology Service New York-Presbyterian Hospital Columbia University Medical Center New York, NY 10032 Robert Schlaberg Department of Pathology New York-Presbyterian Hospital Columbia University Medical Center New York, NY 10032 Phyllis Della-Latta* Clinical Microbiology Service New York-Presbyterian Hospital Columbia University Medical Center CHC 3-325 622 W. 168th St. New York, NY 10032
						* Phone: (212) 305-2929 Fax: (212) 305-8971 E-mail: pd23{at}columbia.edu

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Journal of Clinical Microbiology, July 2008, p. 2469-2470, Vol. 46, No. 7
0095-1137/08/$08.00+0     doi:10.1128/JCM.00510-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Witebsky, F. G. Articles by Della-Latta, P. Search for Related Content PubMed PubMed Citation Articles by Witebsky, F. G. Articles by Della-Latta, P.