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Applied and Environmental Microbiology, November 2008, p. 6814-6817, Vol. 74, No. 21
0099-2240/08/$08.00+0 doi:10.1128/AEM.01106-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Distribution of Different Species of the Bacteroides fragilis Group in Individuals with Japanese Cedar Pollinosis
Toshitaka Odamaki,1*
Jin-Zhong Xiao,1
Mitsuo Sakamoto,2
Shizuki Kondo,1
Tomoko Yaeshima,1
Keiji Iwatsuki,1
Hideo Togashi,3
Tadao Enomoto,4 and
Yoshimi Benno2
Food Science and Technology Institute, Morinaga Milk Industry Co., Ltd., Kanagawa, Japan,1
Microbe Division/Japan Collection of Microorganisms, RIKEN BioResource Center, Saitama, Japan,2
Togashi Clinic, Kanagawa, Japan,3
Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Tottori University, Tottori, Japan4
Received 16 May 2008/
Accepted 5 September 2008

ABSTRACT
We investigated associations of species of the
Bacteroides fragilis group with Japanese cedar pollinosis (JCPsis). Cell numbers
of
Bacteroides fragilis and
Bacteroides intestinalis were significantly
higher in JCPsis subjects than in non-JCPsis subjects before
the pollen season. They correlated positively with both symptom
scores and JCPsis-specific immunoglobulin E levels.

INTRODUCTION
Japanese cedar pollinosis (JCPsis), an immunoglobulin E (IgE)-mediated
type I allergy caused by exposure to Japanese cedar (
Cryptomeria japonica) pollen (JCP), represents a public health issue affecting
over 16% of the Japanese population (
4). In clinical studies
evaluating the effects of a probiotic strain,
Bifidobacterium longum BB536, on JCPsis, we found that administration of
B. longum BB536 significantly alleviated some subjective symptoms
and affected blood markers in individuals with JCPsis (
20-
22).
Furthermore, we observed fluctuations in the
Bacteroides fragilis group among individuals with JCPsis in the pollen season, with
administration of
B. longum BB536 suppressing these fluctuations
(
12,
13). The genus
Bacteroides is known as one of the predominant
intestinal bacteria in humans. The
Bacteroides fragilis group
has been suggested to be associated with allergic disease in
several clinical studies (
5,
8,
16). However, the taxonomy of
the genus
Bacteroides has undergone significant changes in the
past few years (
15), owing to the redefinition of the genus
Bacteroides and the application of molecular biological techniques
leading to the identification of several novel species (
1-
3,
6,
9). Little has been determined regarding the distributions
of these bacteria in human fecal microbiota.
In the present study, we designed 14 specific primer pairs to detect species in the Bacteroides fragilis group that have been isolated from and identified in human feces and investigated distributions of each species for individuals with JCPsis and those without JCPsis by real-time PCR, to evaluate possible associations with JCPsis.

Clinical study.
Samples came from a clinical study reported by Xiao et al. (
21)
evaluating the effects of
B. longum BB536 on clinical symptoms
of JCPsis and blood parameters. Briefly, a total of 44 adults
with JCPsis were randomized to ingest either
B. longum BB536
powder (BB536 group; 13 men and 9 women; mean age, 36.0 ±7.3
years) or placebo powder (placebo group; 13 men and 9 women;
mean age, 36.5 ±8.1 years), in a randomized, double-blinded
design during the pollen season (20 January to 21 April). Fourteen
healthy adults who were JCP specific, IgE negative, and without
prior history of spring allergic rhinitis (healthy group, 11
men and 3 women; mean age, 33.4 ± 7.6 years) were administered
placebo powder during the same intervention period in an identical
manner to JCPsis subjects. Participants were instructed to collect
specimens in a plastic tube, cool the bag immediately to <10°C,
and deliver the sample within 12 h. Collected specimens were
stored at –80°C until analysis.

Design and specificity of primer pairs.
DNA extraction from fecal samples was performed as described
previously (
13). Fourteen 16S rRNA gene-targeted species-specific
primers (Table
1) were designed and checked for specificity
according to previous reports (
10,
14). The amplification program
consisted of 94°C for 10 s, followed by 35 cycles of 94°C
for 5 s and 60°C for 30 s. Melting curves were obtained
by heating from 60°C to 95°C in increments of 0.2°C/s,
with continuous fluorescence collection. DNA extracts from the
type strains listed in Table
1 were used as standards for the
determination of the cell number of each species. The specificity
of each primer pair was then tested using DNA extracts from
all strains listed in Table
1, with the addition of
Parabacteroides distasonis JCM 5825
T,
Parabacteroides merdae JCM 9497
T,
Prevotella intermedia JCM 12248
T, and
Porphyromonas gingivalis JCM 8525,
12257
T. Each specific primer yielded positive PCR results for
the corresponding target bacterium and negative PCR results
for nontarget microorganisms.

Distribution of each species of the Bacteroides fragilis group in fecal samples.
Analyses were conducted on fecal samples collected from individuals
that completed the study before (20 January, before the sample
intake) and after (21 April) the pollen season. We observed
some different distributions of the
Bacteroides fragilis group
for the JCPsis group compared with the healthy group before
the pollen season (Table
2). In particular, cell numbers of
Bacteroides fragilis and
Bacteroides intestinalis were significantly
higher in the JCPsis group than in the non-JCPsis group (Table
2).
Compared to the pre-pollen season, totals of nine, six, and
two species of the
Bacteroides fragilis group were increased
significantly after the pollen season in the placebo, BB536
and healthy groups, respectively (Table
3). Among these, when
taking notice of those species that increased among the JCPsis
subjects, it was found that
Bacteroides caccae, Bacteroides vulgatus, Bacteroides fragilis, and
Bacteroides intestinalis were significantly increased only in the placebo group.
View this table:
[in this window]
[in a new window]
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TABLE 3. Cell numbers for species of the Bacteroides fragilis group in fecal samples before and after pollen season
|
Comparing cell numbers after pollen season, significant intergroup
differences were found for
Bacteroides fragilis and
Bacteroides intestinalis between the placebo and healthy groups and significant
intergroup differences were found for
Bacteroides fragilis between
the placebo and BB536 groups.

Correlation analyses.
Significant positive correlations with clinical symptom scores
and JCP-specific IgE levels were observed for cell numbers of
Bacteroides fragilis and
Bacteroides intestinalis either before
or after the pollen season (Table
4). Conversely, significant
negative correlations with JCP-specific IgE level were observed
for cell numbers of
Bacteroides uniformis and
Bacteroides caccae before the pollen season.
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[in this window]
[in a new window]
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TABLE 4. Correlations between cell number of Bacteroides species and composite symptom score and JCPsis-specific IgE
|

Conclusions.
We observed that cell numbers of
Bacteroides fragilis and
Bacteroides intestinalis were significantly higher in the JCPsis group than
in the healthy group before and after the pollen season. Furthermore,
significant positive correlations were found between the cell
numbers of these two species with composite symptom scores and
JCP-specific IgE. Our data suggest that prevalence of
Bacteroides fragilis and
Bacteroides intestinalis might represent risk factors
for JCPsis. In addition, no significant change was observed
in cell numbers of
Bacteroides fragilis or
Bacteroides intestinalis in the BB536 group, suggesting that intake of
B. longum BB536
may play a role in stabilizing the microbiota, which might in
turn exert suppressive effects on sensitization to pollen and/or
symptom development.
Increased prevalence of the Bacteroides fragilis group has been observed in individuals with allergic diseases or under stress conditions (5, 7, 8, 16, 17). In vitro studies have demonstrated that Bacteroides fragilis perturbed host immunity (11, 12, 18, 19). These lines of evidence implied an exacerbating effect of the Bacteroides fragilis group on allergic disorders. To the best of our knowledge, this is the first report to outline a possible association between the species of the Bacteroides fragilis group and allergic diseases, although we cannot deny that there might be some biases in the cell numbers of each species since they have only been determined by the quantitative PCR method. Nevertheless, the results from the intra/intergroup differences should have not been influenced greatly. Further studies are needed to confirm these results, especially for Bacteroides intestinalis since the prevalence was relatively low.

ACKNOWLEDGMENTS
We thank Hidenori Hayashi of the Maebashi Institute of Technology
for guidance with novel species of the
Bacteroides fragilis group.

FOOTNOTES
* Corresponding author. Mailing address: Food Science and Technology Institute, Morinaga Milk Industry Co., Ltd., Zama, Kanagawa 228-8583, Japan. Phone: 81-46-252-3047. Fax: 81-46-252-3055. E-mail:
t-odamak{at}morinagamilk.co.jp 
Published ahead of print on 12 September 2008. 

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Applied and Environmental Microbiology, November 2008, p. 6814-6817, Vol. 74, No. 21
0099-2240/08/$08.00+0 doi:10.1128/AEM.01106-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.