Journal of Clinical Microbiology, July 2001, p. 2751-2752, Vol. 39, No. 7
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.7.2751-2752.2001
LETTERS TO THE EDITOR
Misidentifying Helicobacter cinaedi
 |
LETTER |
In their paper Vandamme et al. (1) report on the
problems associated with the proper identification of helicobacters,
citing as an example Helicobacter cinaedi. This species is
very heterogeneous, and they propose that several groups of
helicobacters formerly thought to represent separate species, such as
Helicobacter westmeadii and Helicobacter sp.
Mainz, should be classified as H. cinaedi. In the course of
our own work on helicobacters, we recently realized another possible
source for misidentification of H. cinaedi. By genetic
analysis of several type strains of helicobacters, we found a
discrepancy between the type strain of H. cinaedi from the
Culture Collection of the University of Göteborg (CCUG) (CCUG 18818T) and the one from the American Type Culture
Collection (ATCC) (ATCC 35683T). The analysis consisted of
sequencing of the 16S rRNA gene (rrs) (lengths sequenced
were 1,330 bp and 1,681 bp with intervening sequence [IVS]) as well
as sequencing of 480 bp of the gene for the 
-subunit of the RNA
polymerase (rpoB). The strains analyzed and the results of
sequence comparisons are listed in Table
1. We found a discrepancy between the
H. cinaedi type strains from ATCC and CCUG of 4% for the
rrs sequences and 25% for the rpoB sequences.
Interestingly, the ATCC type strain showed sequence identity with the
H. fennelliae type strains from the National Collection of
Type Cultures, the Laboratory for Microbiology at the University of
Ghent (LMG), and CCUG, also containing an IVS of about 350 bp in the
rrs gene (Table 1 and GenBank accession no. M88154).
In order to exclude our own laboratory artifacts due to a mix-up of
long-term stored strains, the two type strains for H. cinaedi were ordered separately again from ATCC and CCUG and the genetic analysis was repeated. The same sequences were obtained from
the new batches and from the long-term stock cultures of the H. cinaedi type strains. The sequences determined for the comparison
are available under GenBank accession no. AF348752 to AF348752.
Our results show that, besides biological problems in identifying and
characterizing H. cinaedi isolates, the reference strain to
which results are compared might also add to confusion. Based on our
data, one could argue that the ATCC type strain of H. cinaedi is most probably a H. fennelliae isolate, but
in order to clear the situation, each culture collection should trace
the origin of its corresponding type strain and probably carry out
additional tests. In this context, we would like to stress the fact
that the quality of the strains and services provided by the major culture collections is undoubtedly of a very high standard.
| |
FOOTNOTES |
*
Phone: 41-31-631485
Fax: 41-31-6312634
E-mail: peter.kuhnert{at}vbi.unibe.ch
| |
REFERENCE |
| 1.
|
Vandamme, P.,
C. S. Harrington,
K. Jalava, and S. L. W. On.
2000.
Misidentifying helicobacters: the Helicobacter cinaedi example.
J. Clin. Microbiol.
38:2261-2266[Abstract/Free Full Text].
|
| | | | |
Peter Kuhnert*
|
| | | | |
André P. Burnens
Institute of Veterinary Bacteriology
Länggass-Str. 122
CH-3012 Bern, Switzerland
|
| |
AUTHORS' REPLY |
Dr. Kuhnert and Dr. Burnens highlight another potential source of
error in the identification of H. cinaedi and of bacteria in
general. Since the identification process involves matching data sets
obtained from an unknown strain with those of previously described taxa, any mislabeling of the latter can result in unknown strains being misidentified. The experiences of Dr. Kuhnert and Dr.
Burnens suggest that the type strain of H. cinaedi currently held at the ATCC may be a strain of H. fennelliae. We urge
the authors to contact the ATCC directly to bring this to the attention of the authorities at that institution.
In this context, mislabeled strains are not the only source of
potential error in identification studies. Incorrectly labeled sequences held in public databases can also result in
misidentifications. The mislabeling of a 16S rRNA gene
sequence (GenBank accession number M88137) originally attributed
to "Flexispira (Helicobacter) rappini" but subsequently corrected by Dr. F. E. Dewhirst has been presumed to explain the identification of a strain of
this taxon which bears a poor resemblance to other "F.
rappini" strains (1). Furthermore, poorly
classified strains can also serve to confuse other workers
(1), and we recommend caution where strains are
identified as species not validated by publication in the
International Journal of Systematic and Evolutionary
Microbiology. For these reasons, the practice of
polyphasic strategies to classify and identify new bacterial taxa
is recommended (2), since this allows the most accurate
assignment of taxonomic relationships. Furthermore, any incongruent
data on a strain can be checked and potential errors determined before
the information is made public.
The identification of Helicobacter,
Campylobacter, Arcobacter, and species of
related genera is known to be a difficult task. We hope that with
the publicizing of the detrimental influence of mislabeling and
misclassification on the identification process, such sources of error
will greatly diminish.
| |
FOOTNOTES |
*
Phone: (45) 35 30 02 59 Fax: (45) 35 30 01 20 E-mail: sto{at}svs.dk
**
Phone: (32) 9 264 5113 Fax: (32) 9 264 5092 E-mail: Peter.Vandamme{at}rug.ac.be
| |
REFERENCES |
| 1.
| On, S. L. W. Taxonomy of
Campylobacter, Arcobacter,
Helicobacter and related bacteria: current status, future
prospects, and immediate concerns. J. Appl. Microbiol., in press.
|
| 2.
|
Vandamme, P.,
B. Pot,
M. Gillis,
P. De Vos,
K. Kersters, and J. Swings.
1996.
Polyphasic taxonomy, a concensus approach to bacterial systematics.
Microbiol. Rev.
60:407-438[Abstract/Free Full Text].
|
| | | | |
Stephen L. W. On*
Danish Veterinary
Laboratory
Bülowsvej 27
DK-1790 Copenhagen V, Denmark
|
| | | | |
Peter A. R. Vandamme**
Laboratorium voor Microbiologie
Universiteit
Gent
Ledeganckstraat 35
B-9000 Gent, Belgium
|
Journal of Clinical Microbiology, July 2001, p. 2751-2752, Vol. 39, No. 7
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.7.2751-2752.2001
Previous Article | Next Article 
