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Yoshifumi Takeda

Publications and source records attributed to Yoshifumi Takeda.

At least 19 recordsLinked to original sources
PubMed2007

Global dissemination of Vibrio parahaemolyticus serotype O3:K6 and its serovariants.

Vibrio parahaemolyticus is recognized as a cause of food-borne gastroenteritis, particularly in the Far East, where raw seafood consumption is high. An unusual increase in admissions of V. parahaemolyticus cases was observed at the Infectious Diseases Hospital in Calcutta, a city in the northeastern part of India, beginning February 1996. Analysis of the strains revealed that a unique serotype, O3:K6, not previously isolated during the surveillance in Calcutta accounted for 50 to 80% of the infections in the following months. After this report, O3:K6 isolates identical to those isolated in Calcutta were reported from food-borne outbreaks and from sporadic cases in Bangladesh, Chile, France, Japan, Korea, Laos, Mozambique, Peru, Russia, Spain, Taiwan, Thailand, and the United States. Other serotypes, such as O4:K68, O1:K25, and O1:KUT (untypeable), that had molecular characteristics identical to that of the O3:K6 serotype were subsequently documented. These serotypes appeared to have diverged from the O3:K6 serotype by alteration of the O:K antigens and were defined as "serovariants" of the O3:K6 isolate. O3:K6 and its serovariants have now spread into Asia, America, Africa, and Europe. This review traces the genesis, virulence features, molecular characteristics, serotype variants, environmental occurrence, and global spread of this unique clone of V. parahaemolyticus.

Ecology↗
PubMed2006

Cholera due to altered El Tor strains of Vibrio cholerae O1 in Bangladesh.

We determined the types of cholera toxin (CT) produced by a collection of 185 Vibrio cholerae O1 strains isolated in Bangladesh over the past 45 years. All of the El Tor strains of V. cholerae O1 isolated since 2001 produced CT of the classical biotype, while those isolated before 2001 produced CT of the El Tor biotype.

Amino Acid Sequence↗
PubMed2006

A second generation of double mutant cholera toxin adjuvants: enhanced immunity without intracellular trafficking.

Nasal application of native cholera toxin (nCT) as a mucosal adjuvant has potential toxicity for the CNS through binding to GM1 gangliosides in the olfactory nerves. Although mutants of cholera toxin (mCTs) have been developed that show mucosal adjuvant activity without toxicity, it still remains unclear whether these mCTs will induce CNS damage. To help overcome these concerns, in this study we created new double mutant CTs (dmCTs) that have two amino acid substitutions in the ADP-ribosyltransferase active center (E112K) and COOH-terminal KDEL (E112K/KDEV or E112K/KDGL). Confocal microscopic analysis showed that intracellular localization of dmCTs differed from that of mCTs and nCTs in intestinal epithelial T84 cells. Furthermore, both dmCTs exhibited very low toxicity in the Y1 cell assay and mouse ileal loop tests. When mucosal adjuvanticity was examined, both dmCTs induced enhanced OVA-specific immune responses in both mucosal and systemic lymphoid tissues. Interestingly, although both dmCT E112K/KDEV and dmCT E112K/KDGL showed high Th2-type and significant Th1-type cytokine responses by OVA-specific CD4+ T cells, dmCT E112K/KDEV exhibited significantly lower Th1-type cytokine responses than did nCT and dmCT E112K/KDGL. These results show that newly developed dmCTs retain strong biological adjuvant activity without CNS toxicity.

Adjuvants, Immunologic↗
PubMed2006

Distribution and characterization of integrons in various serogroups of Vibrio cholerae strains isolated from diarrhoeal patients between 1992 and 2000 in Kolkata, India.

A total of 133 clinical strains of Vibrio cholerae comprising 44 strains of O1, 45 strains of O139 and 44 strains of non-O1, non-O139 serogroups isolated from hospitalized patients in Kolkata, India, from 1992 to 2000 was examined for the presence of class 1, 2 and 4 integrons. By PCR and DNA sequencing, seven strains of O1, one strain of O139 and six strains of non-O1, non-O139 serogroups were found to contain class 1 integron-harbouring genes aadA1, aadA2 (encoding resistance to streptomycin and spectinomycin), blaP1 (resistance to beta-lactams), aar-3 (resistance to rifampicin), aacA4 (resistance to kanamycin and gentamicin), and dfrA1 and dfrA15 (resistance to trimethoprim). Most strains produced one or two bands using primers specific for the amplification of the variable region where the antibiotic-resistance genes are located, and their sizes ranged from 700 to 1250 bp. However, one strain of V. cholerae O1 isolated in 1994 gave a 2483 bp fragment, the largest fragment so far found in a class 1 integron of V. cholerae O1. No strain was positive for the intI2 gene. All V. cholerae strains, regardless of serogroup, were positive for the intI4 gene by PCR and using a colony hybridization test. Amplification of the intI4 gene by PCR yielded a 2200 bp fragment (1260 bp larger than the expected size) from three V. cholerae O139 strains isolated in 1999. Sequence analysis of this amplicon revealed an insertion of IS1359 in the middle of the intI4 gene. These data indicate that a class 1 integron is present in some clinical strains of V. cholerae isolated in Kolkata, India, and that a class 4 integron is ubiquitously distributed among V. cholerae strains regardless of serogroup.

Anti-Bacterial Agents↗
PubMed2006

Genetic characteristics of Matlab variants of Vibrio cholerae O1 that are hybrids between classical and El Tor biotypes.

The Matlab variants of Vibrio cholerae O1, defined as hybrids between the classical and El Tor biotypes, were first isolated from hospitalized patients with acute secretory diarrhoea in Matlab, a rural area of Bangladesh. These variants could not be categorized as classical or El Tor biotypes by phenotypic and genotypic tests, and had representative traits of both the biotypes. A number of virulence-associated genes and/or gene clusters were screened by PCR and DNA sequencing. El Tor-specific gene clusters, Vibrio seventh-pandemic islands (VSP)-I and -II and repeat toxin (RTX) were present in the genome of these variants, indicating their El Tor lineage, whereas the nucleotide-sequence-derived CtxB amino acid sequence of these strains grouped them under the classical biotype. Matlab variants possessed all the necessary genes to initiate pandemics. The genetic relatedness of Matlab variants to the V. cholerae strains recently isolated in Mozambique is another important observation of this study, which underscores the epidemiological significance of Matlab variants.

Agglutination Tests↗
PubMed2006

Molecular analysis of the rstR and orfU genes of the CTX prophages integrated in the small chromosomes of environmental Vibrio cholerae non-O1, non-O139 strains.

The ctxAB genes encoding cholera toxin, reside in the genome of a filamentous bacteriophage CTXphi. The presence of CTX prophage in non-epidemic environmental Vibrio cholerae strains is rare. The CTX prophage, the lysogenic form of CTXphi in V. cholerae, is comprised of the 'RS2' and the 'Core'. Analysis of the rstR gene present in the RS2 region of the CTX prophage revealed the presence of new alleles of the prophages in four environmental non-O1, non-O139 strains VCE22 (O36), VCE228 (O27), VCE232 (O4) and VCE233 (O27), and the CTX prophages are located in the small chromosomes. Phylogenetic analysis based on the nucleotide sequences of the rstR and orfU (present in the core) genes of these prophages placed them in a single unique cluster, which is distally located compared with that of epidemic V. cholerae O1 strains. Further analysis indicated that the genome of the prophage present in the strain VCE22 is devoid of the ctxAB genes, called pre-CTX prophage and the strain also possess the toxin-coregulated pilus protein coding gene tcpA of classical type, another important pathogenicity determining locus of the epidemic V. cholerae strains. Comparative analysis of the nucleotide sequences of the rstR and orfU genes indicated that the pre-CTX prophage of VCE22 might be the progenitor of new alleles of the CTX prophages present in these environmental strains.

Bacterial Proteins↗
PubMed2005

Asymmetric total synthesis of fredericamycin A: an intramolecular cycloaddition pathway.

The asymmetric total synthesis of the potent antitumor antibiotic fredericamycin A ((S)-1) was achieved by the intramolecular [4+2] cycloaddition of the silylene-protected styrene derivative (S)-7 followed by the aromatic Pummerer-type reaction of the sulfoxide (S)-5. Although we had already succeeded in the total synthesis of racemic 1 by the same approach, synthesis of its asymmetric version was more complicated than we had expected due to the difficulties involved in constructing the quaternary carbon center and the tendency of this center to undergo facile racemization. Racemization of this center during the installation of the acetylene moiety on the dione (R)-8 was the most serious aspect. Systematic studies of its DE-ring analogue (R)-25 revealed that racemization of the quaternary carbon center proceeded by a retro-aldol-aldol reaction of the initial adduct, (1R)-39 a-Li, and that the degree of racemization was dependent on the reaction temperature. The racemization process could be completely depressed by keeping the reaction temperature at -78 degrees C. The construction of the stereogenic quaternary carbon center was achieved by the lipase-catalyzed desymmetrization of the prochiral 1,3-diol 9 a bearing the DEF-ring moiety. These studies enabled us to attain the asymmetric total synthesis of (S)-1 while completely retaining the chiral integrity created by the enzymatic reactions.

Antibiotics, Antineoplastic↗
PubMed2005

Cytotoxic and cell vacuolating activity of Vibrio fluvialis isolated from paediatric patients with diarrhoea.

Vibrio fluvialis is a halophilic Vibrio species associated with acute diarrhoeal illness in humans. It has the potential to cause outbreaks and has an association with paediatric diarrhoea. In this study, 11 V. fluvialis strains isolated from hospitalized patients with acute diarrhoea at the Infectious Diseases Hospital, Kolkata were extensively characterized. All the strains showed growth in peptone broth containing 7% NaCl. The strains showed variable results in Voges-Proskauer test and to a vibriostatic agent. There was also variation in their antibiograms, and some of the strains were multidrug resistant. Among the 11 strains, two showed only a single band difference in their PFGE profile and the remaining strains showed nine different PFGE patterns. However, unlike PFGE, the strains exhibited close matches and clustering in their ribotype patterns. The haemolytic effect on sheep red blood cells varied with strains. Partial sequence analysis revealed that the V. fluvialis haemolysin gene has 81% homology with that of the El Tor haemolysin of Vibrio cholerae. A striking finding was the capability of all the strains to evoke distinct cytotoxic and vacuolation effects on HeLa cells.

Bacterial Toxins↗
PubMed2005

Nontoxic Shiga toxin derivatives from Escherichia coli possess adjuvant activity for the augmentation of antigen-specific immune responses via dendritic cell activation.

Shiga toxin (Stx) derivatives, such as the Stx1 B subunit (StxB1), which mediates toxin binding to the membrane, and mutant Stx1 (mStx1), which is a nontoxic doubly mutated Stx1 harboring amino acid substitutions in the A subunit, possess adjuvant activity via the activation of dendritic cells (DCs). Our results showed that StxB1 and mStx1, but not native Stx1 (nStx1), resulted in enhanced expression of CD86, CD40, and major histocompatibility complex (MHC) class II molecules and, to some extent, also enhanced the expression of CD80 on bone marrow-derived DCs. StxB1-treated DCs exhibited an increase in tumor necrosis factor alpha and interleukin-12 (IL-12) production, a stimulation of DO11.10 T-cell proliferation, and the production of both Th1 and Th2 cytokines, including gamma interferon (IFN-gamma), IL-4, IL-5, IL-6, and IL-10. When mice were given StxB1 subcutaneously, the levels of CD80, CD86, and CD40, as well as MHC class II expression by splenic DCs, were enhanced. The subcutaneous immunization of mice with ovalbumin (OVA) plus mStx1 or StxB1 induced high titers of OVA-specific immunoglobulin M (IgM), IgG1, and IgG2a in serum. OVA-specific CD4+ T cells isolated from mice immunized with OVA plus mStx1 or StxB1 produced IFN-gamma, IL-4, IL-5, IL-6, and IL-10, indicating that mStx1 and StxB1 elicit both Th1- and Th2-type responses. Importantly, mice immunized subcutaneously with tetanus toxoid plus mStx1 or StxB1 were protected from a lethal challenge with tetanus toxin. These results suggest that nontoxic Stx derivatives, including both StxB1 and mStx1, could be effective adjuvants for the induction of mixed Th-type CD4+ T-cell-mediated antigen-specific antibody responses via the activation of DCs.

Adjuvants, Immunologic↗
PubMed2004

A novel adjuvant for mucosal immunity to HIV-1 gp120 in nonhuman primates.

The development of a safe and effective mucosal adjuvant is a crucial step toward a mucosal HIV/AIDS vaccine. This study seeks to determine the promise of a nontoxic mutant of cholera toxin (mCT; E112K) as a mucosal adjuvant in nonhuman primates. HIV-1 gp120 was nasally administered together with mCT E112K or native CT (nCT) as adjuvant on five to six occasions over a 6- to 8-wk period to groups of four rhesus macaques and alone to two monkeys that acted as controls. Macaques given nasal gp120 with either mCT E112K or nCT showed elevated gp120-specific IgG and IgA Ab responses with virus-neutralizing activity in both their plasma and mucosal external secretions, as well as higher numbers of gp120-specific IgA Ab-forming cells in their mucosal and peripheral lymphoid tissues and of IL-4-producing Th2-type CD4-positive (CD4(+)) T cells than did controls. Even though significant mucosal adjuvanticity was seen with both mCT E112K and nCT, neuronal damage was observed only in the nCT-treated, but not in the control or mCT E112K-treated groups. These results clearly show that mCT E112K is an effective and safe mucosal adjuvant for the development of a nasal HIV/AIDS vaccine.

AIDS Vaccines↗
PubMed2004

Non-toxic Stx derivatives from Escherichia coli possess adjuvant activity for mucosal immunity.

Both B subunit of Shiga toxin 1 (Stx1-B), which mediates the binding of toxin to the membrane, and mutant Stx1 (mStx1), which is a non-toxic double-mutated Stx1 harboring double amino acid substitutions in the A subunit, possess potent mucosal adjuvant activity. Nasal immunization of mice with ovalbumin (OVA) plus the Stx1-B or mStx1 induced OVA-specific serum IgG and mucosal IgA responses. IgG subclass analysis revealed that mStx1 and Stx1-B as mucosal adjuvants supported Ag-specific IgG1 followed by IgG2b Abs. The co-administration of either mStx1 or Stx1-B with OVA enhanced the production of IL-4, IL-5, IL-6 and IL-10 with low IFN-gamma, by OVA-specific CD4+ T cells. To better elucidate the mechanisms underlying mStx1's and Stx1-B's adjuvant activity, we next sought to examine whether or not dendritic cells (DC) residing in the nasopharyngeal-associated lymphoreticular tissue (NALT) were activated by nasal administration of Stx1-B or mStx1. We found that mice nasally administered with Stx1-B or mStx1 showed an up-regulation in the expression of CD80, CD86 and especially CD40 on NALT DCs. Taken together, these results suggest that non-toxic Stx derivatives could be effective mucosal adjuvants for the induction of Th2-type, CD4+ T cell mediated, antigen-specific mucosal IgA and systemic IgG Ab responses, and that they likely owe their adjuvant activity to the up-regulation of co-stimulatory molecules including CD80, CD86 and CD40 on NALT DCs.

Adjuvants, Immunologic↗
PubMed2004

Atomically sharp magnetic domain wall in thin film Fe(110): a first principles noncollinear magnetism study.

Magnetic domain wall structures in an Fe (110) monolayer are determined by the highly precise first principles full-potential linearized augmented plane-wave method including intra-atomic noncollinear magnetism. The self-consistent results demonstrate that the magnetization changes from one orientation to the opposite (180 degrees ) orientation within an 8 A width without any abrupt rotation. This narrow domain wall is found to arise from band effects. Our results are consistent with and support domain walls having a 6 A width recently observed in spin-polarized scanning tunneling microscopy experiments.

Journal Article↗
PubMed2004

Molecular characterisation of rough strains of Vibrio cholerae isolated from diarrhoeal cases in India and their comparison to smooth strains.

Sixteen of the 18 Vibrio cholerae rough strains isolated from hospitalised diarrhoea patients were found to contain O1 serotype-specific (wbe) genes and all currently known virulence genes. Expression of the regulatory element ToxR was evident in these strains. Cholera toxin production ability of the rough strains was found to be higher (c. three- to five-fold) as compared to the smooth counterparts and this was transcriptionally regulated. Strains exhibiting the rough phenotype were more amenable to the uptake of CTXphi, which led us to consider that the rough phenotype could play a role in the generation of genetic diversity among V. cholerae strains.

Bacterial Proteins↗
PubMed2004

Molecular epidemiology of diarrhoeagenic Escherichia coli associated with sporadic cases and outbreaks of diarrhoea between 2000 and 2001 in India.

Diarrhoeal infection caused by Escherichia coli is common in India with occasional outbreaks. However, association of different pathotypes of diarrhoeagenic E. coli (DEC) with the disease and its phenotypic and genotypic characteristics are not fully demonstrated. In this study, E. coli strains from sporadic cases and outbreaks of diarrhoea during 2000-2001 were confirmed as DEC by polymerase chain reaction (PCR) targeting the specific virulence genes. DEC represented by enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC) and enteroaggregative E. coli (EAggEC) were mostly belonged to O serogroups 25, 86a, 114 and 146. The gene astA was frequently detected among ETEC and EAggEC than EPEC. After initial screening of 200 DEC strains with serology and antibiotic susceptibility test, 32 strains representing ETEC, EPEC, and EAggEC isolated from different areas of India were included in the pulsed-field gel electrophoresis (PFGE) analysis. Using the PFGE results, the hierarchical representation of different linkage levels between the DEC strains were determined by unweighed pair-group arithmetic mean (UPGAMA) method. Except for few strains, clonotyping by PFGE revealed no correlation between pathotypes and serogroups as well as the place of isolation of the DEC strains. The prevailing clonal diversity among the different categories of DEC strains suggests that the pathotypes of DEC belonged to diverse clones.

Cluster Analysis↗
PubMed2004

Clonal multidrug-resistant Shigella dysenteriae type 1 strains associated with epidemic and sporadic dysenteries in eastern India.

Multidrug-resistant strains of Shigella dysenteriae type 1 were implicated in three outbreaks and sporadic cases of dysentery in eastern India in 2002 and 2003. After a hiatus of 14 years, this pathogen reemerged with an altered antibiotic resistance pattern. In addition to ampicillin, co-trimoxazole, tetracycline, chloramphenicol, and nalidixic acid, all the recent strains were resistant to norfloxacin, lomefloxacin, pefloxacin, and ofloxacin and showed reduced susceptibility to ciprofloxacin. Pulsed-field gel electrophoresis identified a new clone of S. dysenteriae type 1 that was associated with the recent outbreaks and sporadic cases. Based on the spatial and temporal spread of multidrug-resistant S. dysenteriae type 1, we predict that this clonal type may spread further in this region.

DNA Fingerprinting↗
PubMed2004

Probiotic bifidobacteria protect mice from lethal infection with Shiga toxin-producing Escherichia coli O157:H7.

The anti-infectious activity of probiotic Bifidobacteria against Shiga toxin-producing Escherichia coli (STEC) O157:H7 was examined in a fatal mouse STEC infection model. Stable colonization of the murine intestines was achieved by the oral administration of Bifidobacterium breve strain Yakult (naturally resistant to streptomycin sulfate) as long as the mice were treated with streptomycin in their drinking water (5 mg/ml). The pathogenicity of STEC infection, characterized by marked body weight loss and subsequent death, observed in the infected controls was dramatically inhibited in the B. breve-colonized group. Moreover, Stx production by STEC cells in the intestine was almost completely inhibited in the B. breve-colonized group. A comparison of anti-STEC activity among several Bifidobacterium strains with natural resistance to streptomycin revealed that strains such as Bifidobacterium bifidum ATCC 15696 and Bifidobacterium catenulatum ATCC 27539(T) did not confer an anti-infectious activity, despite achieving high population levels similar to those of effective strains, such as B. breve strain Yakult and Bifidobacterium pseudocatenulatum DSM 20439. The effective strains produced a high concentration of acetic acid (56 mM) and lowered the pH of the intestine (to pH 6.75) compared to the infected control group (acetic acid concentration, 28 mM; pH, 7.15); these effects were thought to be related to the anti-infectious activity of these strains because the combination of a high concentration of acetic acid and a low pH was found to inhibit Stx production during STEC growth in vitro.

Acetic Acid↗
PubMed2004

Development of a PCR-restriction fragment length polymorphism assay for the epidemiological analysis of Shiga toxin-producing Escherichia coli.

Six characteristic regions (I to VI) were identified in Shiga toxin 2 (Stx2) phages (T. Sato, T. Shimizu, M. Watarai, M. Kobayashi, S. Kano, T. Hamabata, Y. Takeda, and S. Yamasaki, Gene 309:35-48, 2003). Region V, which is ca. 10 kb in size and is located in the upstream region of the Stx operons, includes the most distinctive region among six Stx phages whose genome sequences have been determined. In this study, we developed a PCR-restriction fragment length polymorphism (RFLP) assay for the epidemiological analysis of Shiga toxin-producing Escherichia coli (STEC) on the basis of the diversity of region V. When region V was amplified by long and accurate-PCR (LA-PCR) with five control E. coli strains carrying six different Stx phages such as E. coli strains C600 (Stx1 phage), C600 (933W phage), C600 (Stx2 phage-I), C600 (Stx2 phage-II), and O157:H7 Sakai strain RIMD0509952 (VT1-Sakai phage and VT2-Sakai phage), an expected size of the band was obtained. Restriction digest of each PCR product with BglI or EcoRV also gave the expected sizes of banding patterns and discriminated the RFLPs of five control strains. When a total of 204 STEC O157 strains were analyzed by LA-PCR, one to three bands whose sizes ranged from 8.2 to 14 kb were obtained. Two STEC O157 strains, however, did not produce any bands. Subsequent restriction digest of the PCR products with BglI or EcoRV differentiated the RFLPs of 202 STEC O157 strains into 24 groups. The RFLP patterns of pulsed-field gel electrophoresis (PFGE) of representative strains of STEC O157 divided into 24 groups were well correlated with those of PCR-RFLP when STEC O157 strains were isolated in the same time period and in the close geographic area. To evaluate the PCR-RFLP assay developed here, ten strains, each isolated from four different outbreaks in different areas in Japan (Tochigi, Hyogo, Aichi, and Fukuoka prefecture), were examined to determine whether the strains in each group showed the same RFLP patterns in the PCR-RFLP assay. In accordance with the results of PFGE except for strains isolated in an area (Fukuoka), which did not produce any amplicon, ten strains in each group demonstrated the same RFLP pattern. Taken together, these data suggest that the PCR-RFLP based on region V is as useful as PFGE but perhaps more simple and rapid than PFGE for the molecular epidemiological analysis of STEC strains during sporadic and common source outbreaks.

Disease Outbreaks↗