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Tianyan Song

Publications and source records attributed to Tianyan Song.

9 recordsLinked to original sources
PubMed2006

A Vibrio cholerae protease needed for killing of Caenorhabditis elegans has a role in protection from natural predator grazing.

Vibrio cholerae is the causal bacterium of the diarrheal disease cholera, and its growth and survival are thought to be curtailed by bacteriovorous predators, e.g., ciliates and flagellates. We explored Caenorhabditis elegans as a test organism after finding that V. cholerae can cause lethal infection of this nematode. By reverse genetics we identified an extracellular protease, the previously uncharacterized PrtV protein, as being necessary for killing. The killing effect is associated with the colonization of bacteria within the Caenorhabditis elegans intestine. We also show that PrtV is essential for V. cholerae in the bacterial survival from grazing by the flagellate Cafeteria roenbergensis and the ciliate Tetrahymena pyriformis. The PrtV protein appears to have an indirect role in the interaction of V. cholerae with mammalian host cells as judged from tests with tight monolayers of human intestinal epithelial cells. Our results demonstrate a key role for PrtV in V. cholerae interaction with grazing predators, and we establish Caenorhabditis elegans as a convenient organism for identification of V. cholerae factors involved in host interactions and environmental persistence.

Animals↗
PubMed2005

Pathogenicity of Shigella in healthy carriers: a study in Vientiane, Lao People's Democratic Republic.

Shigella spp. isolated from diarrheal patients and non-diarrheal carriers were examined by PCR for the presence of two pathogenic genes, chromosomal ipaH and invasive plasmid encoded ial. Shigella spp. were detected in 7 of 72 diarrheal cases examined (9.7%), and 9 of 145 non-diarrheal cases (6.2%). All isolates from diarrheal cases harbored both ipaH and ial, while all isolates from non-diarrheal cases were positive for ipaH but not ial. These results suggested that Shigella spp. in healthy carriers were basically non-pathogenic.

Adolescent↗
PubMed2004

Purification and characterization of a novel metalloprotease isolated from Aeromonas caviae.

A novel protease produced by Aeromonas caviae was purified and characterized. The molecular weight of the protease (AP19) was estimated as 19 kDa on SDS-polyacrylamide gel electrophoresis. The protease activity was not inhibited completely by heating at 100 degrees C for 15 min. The proteolytic activities were inhibited by metalloprotease inhibitor. The N-terminal amino acid sequence of AP19 was VTASVSFSGRCTN. AP19 did not activate Aeromonas proaerolysin, and did not show fluid accumulation in the rabbit intestinal loop test. A high concentration of the protease showed cytotoxic activity against Vero cells.

Aeromonas↗
PubMed2004

Aerolysin is activated by metalloprotease in Aeromonas veronii biovar sobria.

Aeromonas veronii is an opportunistic human pathogen that causes diarrhoea and extraintestinal infections, such as wound infection and septicaemia. An A. veronii protease (AVP) from a biovar sobria strain, AeG1, was partially purified and characterized. Mature AVP hydrolysed casein but not elastin, and protease activity was inhibited by metalloprotease inhibitors. Nucleotide sequence analysis showed that AVP belongs to the thermolysin family of proteases. An AVP-deficient mutant was constructed to investigate the role of AVP in aerolysin activation. Western blot analysis using anti-aerolysin antisera revealed that proaerolysin (52 kDa) in the AVP-deficient mutant was not completely activated to mature aerolysin (47 kDa) as seen in the wild-type strain. The AVP-deficient mutant showed lower cytotoxic and haemolytic activities than wild type. AVP and proaerolysin had no haemolytic activity; however, activity appeared after incubating both proteins. Taken together, these results suggested that AVP plays an indirect role in virulence through activating aerolysin, which is an essential step for cytotoxic activity.

Aeromonas↗
PubMed2004

Distribution of putative adhesins in different seropathotypes of Shiga toxin-producing Escherichia coli.

The distribution of eight putative adhesins that are not encoded in the locus for enterocyte effacement (LEE) in 139 Shiga toxin-producing Escherichia coli (STEC) of different serotypes was investigated by PCR. Five of the adhesins (Iha, Efa1, LPF(O157/OI-141), LPF(O157/OI-154), and LPF(O113)) are encoded in regions corresponding to genomic O islands of E. coli EDL933, while the other three adhesins have been reported to be encoded in the STEC megaplasmid of various serotypes (ToxB [O157:H7], Saa [O113:H21], and Sfp [O157:NM]). STEC strains were isolated from humans (n = 54), animals (n = 52), and food (n = 33). They were classified into five seropathotypes (A through E) based on the reported occurrence of STEC serotypes in human disease, in outbreaks, and in the hemolytic-uremic syndrome (M. A. Karmali, M. Mascarenhas, S. Shen, K. Ziebell, S. Johnson, R. Reid-Smith, J. Isaac-Renton, C. Clark, K. Rahn, and J. B. Kaper, J. Clin. Microbiol. 41:4930-4940, 2003). The most prevalent adhesin was that encoded by the iha gene (91%; 127 of 139 strains), which was distributed in all seropathotypes. toxB and efa1 were present mainly in strains of seropathotypes A and B, which were LEE positive. saa was present only in strains of seropathotypes C, D, and E, which were LEE negative. Two fimbrial genes, lpfA(O157/OI-141) and lpfA(O157/OI-154), were strongly associated with seropathotype A. The fimbrial gene lpfA(O113) was present in all seropathotypes except for seropathotype A, while sfpA was not present in any of the strains studied. The distribution of STEC adhesins depends mainly on serotypes and not on the source of isolation. Seropathotype A, which is associated with severe disease and frequently is involved in outbreaks, possesses a unique adhesin profile which is not present in the other seropathotypes. The wide distribution of iha in STEC strains suggested that it could be a candidate for vaccine development.

Adhesins, Escherichia coli↗
PubMed2002

Enteroaggregative Escherichia coli: incidence in Japan and usefulness of the clump-formation test.

The usefulness of the clump-formation test described by Albert et al. for identifying enteroaggregative Escherichia coli (EAggEC) and the incidence of EAggEC in Japan were studied. One hundred and seventy strains of E. coli agglutinated with enteropathogenic E. coli diagnostic antisera were collected from a variety of districts in Japan. All isolates were from diarrheal stools. EAggEC was identified on the basis of the presence of the aggR gene accompanied by aggregative adhesion to HEp-2 cells. After 24 strains carrying eaeA, elt, est, stx-1, stx-2, or ipaH genes were eliminated, the remaining 145 strains were examined for adhesion to Hep-2 cells, the presence of the aggRgene, and clump formation on the surface of Muller-Hinton broth. aggR was detected in 10 strains, and 9 of them displayed aggregative adhesion to HEp-2 cells. Seven strains produced marked clumps and 22 showed moderate clump formation. The sensitivity and specificity of the clump-formation test for detecting EAggEC were each about 90%, and they varied slightly depending on the stringency of evaluation for the degree of clump formation. From these results, we conclude that the incidence of EAggEC cannot be ignored as a possible cause of diarrheal disease in Japan, and we strongly recommend the clump-formation test for detecting EAggEC.

Bacterial Adhesion↗