Biomedical subjects

Akihito Wada

Publications and source records attributed to Akihito Wada.

10 recordsLinked to original sources

PubMed2006

Gordonia araii sp. nov. and Gordonia effusa sp. nov., isolated from patients in Japan.

Two bacterial strains, IFM 10211(T) and IFM 10200(T), were isolated from the sputum of two Japanese patients, and were subjected to a polyphasic taxonomic study. The two strains were found to have morphological, physiological and chemotaxonomic properties that were consistent with their assignment to the genus Gordonia, except for a few chemotaxonomic characteristics. Almost complete 16S rRNA gene sequences of the two strains were determined; the data showed that they are related distantly to Gordonia amarae, Gordonia hirsuta, Gordonia hydrophobica and Gordonia sihwensis, showing 16S rRNA gene sequence similarities to the type strains of these species of 96.2-97.9 %. DNA-DNA relatedness data coupled with the combination of genotypic and phenotypic data indicated that the two strains are representatives of two novel, separate species. The names proposed to accommodate these two strains are Gordonia araii sp. nov. (type strain IFM 10211(T)=DSM 44811(T)=NBRC 100433(T)=JCM 12131(T)) and Gordonia effusa sp. nov. (type strain IFM 10200(T)=DSM 44810(T)=NBRC 100432(T)=JCM 12130(T)).

Aged↗

PubMed2006

Surveillance of group B streptococcal toxic shock-like syndrome in nonpregnant adults and characterization of the strains in Japan.

Nine group B streptococci (GBS) strains were isolated from five toxic shock-like syndrome cases of nonpregnant adults in Japan from 2001 to 2005. All of them were identified as Streptococcus agalactiae. The serotypes of these strains were Ib, III, V, and VII. Pulsed-field gel electrophoresis revealed that the patterns of the strains isolated from the different patients were variable. Antimicrobial susceptibility tests showed that all of the strains were susceptible to penicillin G, ampicillin, cefotaxime, clindamycin, and telithromycin. One strain showed intermediate resistance to erythromycin.

Aged↗

PubMed2006

Characteristics of Streptococcus suis isolated from patients in Japan.

Seven cases of Streptococcus suis infection in Japan during 1994 and 2006 were summarized. All cases had porcine exposure and five of them had hand skin injury during the exposure. Five cases presented symptoms of meningitis, three presented symptoms of sepsis, and one resulted in sudden death. All of the isolated S. suis belonged to Lancefield's group D and to serotype 2. They were susceptible to penicillin G, ampicillin, cefotaxime, and ciprofloxacin. However, six of them were resistant to both erythromycin and clindamycin, and four were also resistant to minocycline. Multilocus sequence typing of six isolates showed that they belonged to sequence type (ST) 1, and their pulsed-field gel electrophoresis (PFGE) patterns were similar. The remaining isolate was ST28 and its PFGE pattern was distinct from those of the others.

Animals↗

PubMed2004

Legioliulin, a new isocoumarin compound responsible for blue-white autofluorescence in Legionella (Fluoribacter) dumoffii under long-wavelength UV light.

Legionella dumoffii is one of the causative agents of Legionnaires' disease. There are 50 species in the genus Legionella, of which 10 species including L. dumoffii are known to exhibit uncharacterized blue-white autofluorescence. We constructed an L. dumoffii strain that exhibited a high intensity blue-white fluorescence, isolated a fluorescent pigment from the strain, and determined its molecular formula to be C(19)H(14)O(3) by high-resolution mass spectrometry. An NMR analysis revealed that this was a new isocoumarin compound, which was named legioliulin.

Coumarins↗

PubMed2004

tcaA inactivation increases glycopeptide resistance in Staphylococcus aureus.

The experimental deletion of the tcaRAB region has been shown to increase teicoplanin resistance in Staphylococcus aureus. By sequential genetic complementation of a tcaRAB mutant, we identified tcaA as the key gene within tcaRAB that is responsible for changes in glycopeptide resistance levels. Northern blot analysis of the tcaRAB region showed that the tcaA gene is expressed only weakly over the growth cycle and is strongly inducible by teicoplanin. Among some clinical isolates tested, glycopeptide-intermediate-resistant (GISA) strains Michigan and SA137/93G were found to have truncated tcaA genes. While the former carries a nucleotide insertion that creates a premature stop codon, the latter was found to harbor an IS256 insertion. Complementation of these two GISA strains with a functional tcaA allele reduced their levels of teicoplanin and vancomycin resistance five- to eightfold and twofold, respectively. The data presented here indicate that inactivation of tcaA contributes to and plays a relevant role in glycopeptide resistance in S. aureus clinical isolates.

Anti-Bacterial Agents↗

PubMed2004

TcaR, a putative MarR-like regulator of sarS expression.

TcaR, which shares sequence homology with MarR-like transcriptional regulators, has been identified as a novel Staphylococcus aureus regulator affecting the expression of the global regulatory element SarS (SarH1), as well as that of the cell surface-associated protein SasF (N315-SA2439). Microarray analysis, confirmatory Northern blots, and genetic complementation experiments showed that TcaR upregulates sarS and thus spa transcription. In addition, it attenuates whole-length transcription of sasF, thereby producing a truncated transcript lacking the 3' terminus, which codes for the cell wall anchor motif. Hence, in strains containing an intact tcaR gene, TcaR is likely to decrease the amount of the surface-associated protein SasF and to increase that of the surface-associated protein A. The widely used laboratory strains derived from NCTC8325 were found to be natural, truncated mutants of tcaR, harboring an inactive TcaR and therefore expressing very low levels of sarS. The data presented here identified TcaR as a further activator of sarS, and a modulator of sasF expression that has to be taken into account in studies of virulence gene expression in S. aureus.

Amino Acid Sequence↗

PubMed2003

MsrR, a putative cell envelope-associated element involved in Staphylococcus aureus sarA attenuation.

A novel membrane-associated protein, MsrR, was identified in Staphylococcus aureus which affects resistance to methicillin and teicoplanin, as well as the synthesis of virulence factors. MsrR belongs to the LytR-CpsA-Psr family of cell envelope-related transcriptional attenuators and was shown to be inducible by cell wall-active agents, such as beta-lactams, glycopeptides, and lysostaphin. The expression of msrR peaked in the early exponential growth phase and decreased sharply thereafter. msrR mutants showed increased sarA transcription and an earlier and higher expression of RNAIII, resulting in altered expression of virulence factors such as alpha-toxin and protein A. These observations suggest that MsrR is a new component involved in sarA attenuation and the regulatory network controlling virulence gene expression in S. aureus.

Anti-Bacterial Agents↗

PubMed2002

Cross-reactivity and sensitivity of two Legionella urinary antigen kits, Biotest EIA and Binax NOW, to extracted antigens from various serogroups of L. pneumophila and other Legionella species.

Legionella antigen detection kits for diagnosing legionellosis from urine have become widely used, but basic information about reactivity of the kits to non-serogroup (SG) 1 L. pneumophila and other Legionella species remains incomplete. We evaluated Biotest EIA and the most recently developed Binax NOW by using in-vitro extracted antigens of 22 L. pneumophila SG 1 to 15 strains and of 27 other Legionella species. Both kits showed excellent sensitivity to L pneumophila SG 1 antigens, but reacted to different sets of non-SG I L. pneumophila with different sensitivity. No cross-reactivity was observed to Legionella species other than L. pneumophila.

Antigens, Bacterial↗

PubMed2002

Dissemination of the phage-associated novel superantigen gene speL in recent invasive and noninvasive Streptococcus pyogenes M3/T3 isolates in Japan.

In Japan, more than 10% of streptococcal toxic shock-like syndrome (TSLS) cases have been caused by Streptococcus pyogenes M3/T3 isolates since the first reported TSLS case in 1992. Most M3/T3 isolates from TSLS or severe invasive infection cases during 1992 to 2001 and those from noninvasive cases during this period are indistinguishable in pulsed-field gel electropherograms. The longest fragments of these recent isolates were 300 kb in size, whereas those of isolates recovered during or before 1973 were 260 kb in size. These 260- and 300-kb fragments hybridized to each other, suggesting the acquisition of an about 40-kb fragment by the recent isolates. The whole part of the acquired fragment was cloned from the first Japanese TSLS isolate, NIH1, and its nucleotide sequence was determined. The 41,796-bp fragment is temperate phage phiNIH1.1, containing a new superantigen gene speL near its right attachment site. The C-terminal part of the deduced amino acid sequence of speL has 48 and 46% similarity with well-characterized erythrogenic toxin SpeC and the most potent superantigen, SmeZ-2, respectively. None of 10 T3 isolates recovered during or before 1973 has speL, whereas all of 18 M3/T3 isolates recovered during or after 1992 and, surprisingly, Streptococcus equi subsp. equi ATCC 9527 do have this gene. Though plaques could not be obtained from phiNIH1.1, its DNA became detectable from the phage particle fraction upon mitomycin C induction, showing that this phage is not defective. A horizontal transfer of the phage carrying speL may explain the observed change in M3/T3 S. pyogenes isolates in Japan.

Amino Acid Sequence↗

PubMed2000

Genotypic variations of Shiga toxin-converting phages from enterohaemorrhagic Escherichia coli O157: H7 isolates.

Pulsed-field gel electrophoresis (PFGE) analysis revealed that enterohaemorrhagic Escherichia coli (EHEC) O157:H7 strains had considerable variations in their genomes. This study investigated whether or not the molecular profile of Shiga toxin (Stx) 1- and Stx2-converting phages isolated from EHEC O157:H7 strains, derived from various sources in the USA and Japan, corresponded to the variations of host strains' genotypes as determined by PFGE. A total of 51 Stx-converting phages including 12 Stx1-converting phages and 37 Stx2-converting phages was isolated from seven USA isolates and 20 Japanese isolates. The average Dice coefficient values showed 44% similarity between phage DNAs in Stx2-converting phages digested with SmaI and 55% in Stx1-converting phages digested with HindIII, indicating considerable variation among phage DNA. In particular, restriction fragment length polymorphism (RFLP) patterns of Stx2-converting phage DNA varied according to the PFGE type of their host strain, which suggests that the phage genomes have altered their genotypic characteristics with those of host genomes. However, there are several exceptions: the RFLP patterns of some Stx2-converting phages were quite similar irrespective of the different genotypes of the host strains, indicating that horizontal transfer of Stx2-converting phage may also occur under some circumstances.

Bacterial Toxins↗