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Infection and Immunity, June 2001, p. 4192-4192, Vol. 69, No. 6
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.6.4192.2001

LETTERS TO THE EDITOR

Saccharomyces and Enteropathogenic Escherichia coli


    LETTER

Regarding the study by Czerucka et al. (1) on the mechanism of action of "Saccharomyces boulardii," the latter is an invalid taxonomic term (2). Moreover, studies in our laboratory and in other laboratories reviewed in our paper (2) indicate that "S. boulardii" is a synonym for a strain of Saccharomyces cerevisiae. No other strains of S. cerevisiae were studied by Czerucka et al. so it is not clear that the properties demonstrated (1) for "S. boulardii" would not be possessed by other strains of S. cerevisiae.


    REFERENCES

1. Czerucka, D., S. Dahan, B. Mograbi, B. Rossi, and P. Rampal. 2000. Saccharomyces boulardii preserves the barrier function and modulates the signal transduction pathway induced in enteropathogenic Escherichia coli-infected T84 cells. Infect. Immun. 68:5998-6004[Abstract/Free Full Text].
2. McCullough, M. J., K. V. Clemons, J. H. McCusker, and D. A. Stevens. 1998. Species identification and virulence attributes of Saccharomyces boulardii (nom. inval.). J. Clin. Microbiol. 36:2613-2617[Abstract/Free Full Text].
David A. Stevens
Division of Infectious Diseases
Santa Clara Valley Medical Center
Division of Infectious Diseases and Geographic Medicine
Stanford University
751 S. Bascom Avenue
San Jose, California 95128-2699
Phone: (408) 885-4313
Fax: (408) 885-4306
E-mail: stevens{at}leland.stanford.edu.


    AUTHOR'S REPLY

The interesting letter of Dr. Stevens approaches several different aspects of the question of the denomination of the strain Saccharomyces boulardii.

To avoid any confusion, we consider it useful to differentiate these different aspects.

(i) From an identification and differentiation point of view, clearly, conventional biochemical characteristics cannot be used to unambiguously separate strains of Saccharomyces cerevisiae themselves and to distinguish S. cerevisiae from S. boulardii (3). But in a recent study, both multilocus enzyme electrophoresis and restriction polymorphism of mitochondrial DNA were able to clearly distinguish S. boulardii from S. cerevisiae (M. Mallié, P. Van Nguyen, S. Bertout, and J. M. Bastide. Abstr. 14th Congr. Int. Soc. Hum. Anim. Mycol. 2000, abstr. 511.)

(ii) From a classification point of view it can be discussed whether the particular strain S. boulardii has to be included in the species S. cerevisiae or outside it. Some authors, such as Cardinali and Martini (1) and McFarland (4), consider that S. boulardii is just outside the species S. cerevisiae. Others, such as Mallié et al. (Abstr. 14th Congr. Int. Soc. Hum. Anim. Mycol. 2000), consider that according to current scientific taxonomy, S. boulardii should be considered as part of S. cerevisiae; they consider it an original strain and propose the name S. cerevisiae var. boulardii. Clearly, this is still a debated subject and the paper by Dr. McCullough et al. (3) has probably not closed the discussion.

(iii) Finally, Dr. Stevens questions the fact that we study S. boulardii but no strain of S. cerevisiae. It is an interesting academic question, but we confirm that our studies have focused on lyophilized S. boulardii, which is a marketed product of which Laboratoires Biocodex want to extend the scientific knowledge, encouraging research to further elucidate its mode of action.

In fact, there has been at least one study testing different stains of Saccharomyces. Castagliuolo et al. tested both S. boulardii and another strain (S. cerevisiae ATCC 32167) and found that only S. boulardii exhibited antidiarrheal effects in the rat ileal loop model (2).

Does the fact that we have not studied others strains of Saccharomyces invalidate the value of our research and the interest in reporting it?


    REFERENCES

1. Cardinali, G., and A. Martini. 1994. Electrophoretic karyotypes of authentic strains of the sensu stricto group of the genus Saccharomyces. Int. J. Syst. Bacteriol. 44:791-797[Abstract/Free Full Text].
2. Castagliuolo, I., J. T. LaMont, S. T. Nikulasson, and C. Pothoulakis. 1996. Saccharomyces boulardii protease inhibits Clostridium difficile toxin A effects in the rat ileum. Infect. Immun. 64:5225-5232[Abstract].
3. McCullough, M. J., K. V. Clemons, J. H. McCusker, and D. A. Stevens. 1998. Species identification and virulence attributes of Saccharomyces boulardii (nom. inval.). J. Clin. Microbiol. 36:2613-2617.
4. McFarlane, L. V. 1996. Saccharomyces boulardii is not Saccharomyces cerevisiae. Clin. Infect. Dis. 22:200[Medline].
Dorota Czerucka
Laboratoire de Gastroenterologie et Nutrition
Université de Nice-Sophia Antipolis
28 Avenue de Valombrose
06107 Nice Cedex 2, France
Phone: 33 49 81 77 10
Fax: 33 4 93 37 76 95
E-mail: czerucka{at}unice.fr


Infection and Immunity, June 2001, p. 4192-4192, Vol. 69, No. 6
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.6.4192.2001




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