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Journal of Clinical Microbiology, October 1998, p. 3111-3111, Vol. 36, No. 10
0095-1137/98/$00.00+0
LETTERS TO THE EDITOR
Potential Coinfections Complicate Typing of Pneumocystis
carinii f. sp. hominis
 |
LETTER |
Lee et al. reported on the nucleotide sequence variation of the
two internal transcribed spacers (ITSs), ITS1 and ITS2, of the rRNA
operon of Pneumocystis carinii f. sp. hominis
(3). Thanks to their work, the number of polymorphic
nucleotide positions recognized has increased and the number of
recognized alleles has passed from 2 to 15 for ITS1 and from 3 to 14 for ITS2. Also, the number of different combinations of the alleles of
the two loci, each defining a P. carinii f. sp.
hominis type, has increased from 4 to 59. This great
diversity of types will undoubtedly be useful for epidemiological
studies. Accordingly, Lee et al. concluded that nucleotide sequence
determination of PCR products from these regions is the method of
choice for typing P. carinii f. sp. hominis isolates.
However, typing of P. carinii f. sp. hominis is
complicated by the fact that coinfections of single patients are likely
to occur (for a review, see reference 1). To approach this problem, Lee
et al. used as a screening step five oligonucleotides hybridizing specifically to only two alleles of ITS1 and three alleles of ITS2. A
coinfection was assumed if, for one locus, the PCR product from a
specimen hybridized to more than one oligonucleotide. However, (i) this
method does not allow the differentiation of polymorphisms located
outside the annealing site of the oligonucleotide. Also, (ii) an
oligonucleotide may fail to hybridize to alleles with unrecognized
polymorphisms at the annealing site. According to the data of Lee et
al., the first possibility probably occurred for both ITSs and the
second possibility occurred for only ITS2. Thus, the presence of more
than one allele, revealing possible coinfection events, may be missed
by their screening step.
Given these considerations, we feel that only efficient detection of
potential coinfections, either by direct subcloning of the PCR product
from the ITSs followed by sequencing of numerous clones or by a
multiple-target approach using single-strand conformation polymorphism
(2), will help the progress of P. carinii f.
sp. hominis epidemiology.
| |
REFERENCES |
| 1.
| Hauser, P. M., D. S. Blanc, J. Bille, and P. Francioli. Typing methods to approach Pneumocystis
carinii genetic heterogeneity. FEMS Immunol. Med. Microbiol., in
press.
|
| 2.
|
Hauser, P. M.,
P. Francioli,
J. Bille,
A. Telenti, and D. S. Blanc.
1997.
Typing of Pneumocystis carinii f. .sp. hominis by single-straing conformation polymorphism of four genomic regions.
J. Clin. Microbiol.
35:3086-3091[Abstract].
|
| 3.
|
Lee, C.-H.,
J. Helweg-Larsen,
X. Tang,
S. Jin,
B. Li,
M. S. Bartlett,
J.-J. Lu,
B. Lundgren,
J. D. Lundgren,
M. Olsson,
S. B. Lucas,
P. Roux,
A. Cargnel,
C. Atzori,
O. Matos, and J. W. Smith.
1998.
Update on Pneumocystis carinii f. sp. hominis typing based on nucleotide sequence variations in internal transcribed spacer regions of rRNA genes.
J. Clin. Microbiol.
36:734-741[Abstract/Free Full Text].
|
| | | | |
P. M. Hauser
D. S. Blanc
A. Telenti
A. Nahimana
J. Bille
P. Francioli
Centre Hospitalier Universitaire Vaudois Division Autonome de
Médecine Préventive Hospitalière av. du Bugnon
44 1011 Lausanne, Switzerland
|
| |
AUTHOR'S REPLY |
We agree with the comments of Hauser et al. stating that additional
methods are required to detect all coinfections with Pneumocystis carinii f. sp. hominis in the same patient. Although
the use of the five type-specific oligonucleotide probes that we have
developed previously may not be sufficient to detect all coinfections,
it has enabled us to detect multiple types of P. carinii f.
sp. hominis in many specimens. Using this approach, we have
identified approximately 60 types of P. carinii f. sp.
hominis. This new sequence information will enable the
development of additional type-specific probes and other typing methods
for P. carinii f. sp. hominis.
| | | | |
Chao-Hung Lee
Marilyn S. Bartlett
James W. Smith
Department of Pathology and Laboratory Medicine Indiana University
School of Medicine Indianapolis, Indiana 46202
|
Journal of Clinical Microbiology, October 1998, p. 3111-3111, Vol. 36, No. 10
0095-1137/98/$00.00+0
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