Haruhiko Taguchi

toxB Gene on pO157 of Enterohemorrhagic Escherichia coli O157:H7 Is Required for Full Epithelial Cell Adherence Phenotype

ABSTRACT Adherence of enterohemorrhagic Escherichiacoli (EHEC) to the intestinal epithelium is critical for initiation of a bacterial infection. An in vitro infection study previously indicated that EHEC bacteria initially adhere diffusely and then proliferate to develop MC, a process that is mediated by various secreted proteins, such as EspA, EspB, EspD, Tir, and intimin, as well as other putative adherence factors. In the present study, we investigated the role of a large 93-kb plasmid (pO157) in the adherence of O157:H7 (O157Sakai) and found the toxB gene to be involved in the full adherence phenotype. A pO157-cured strain of O157Sakai (O157Cu) developed microcolonies on Caco-2 cells; however, the number of microcolonies was lower than that of O157Sakai, as were the production and secretion levels of EspA, EspB, and Tir. Introduction of a mini-pO157 plasmid (pIC37) composed of thetoxB and ori regions restored full adherence capacity to O157Cu, including production and secretion of the proteins. In contrast, introduction of a pO157 mutant possessingtoxB::Km into O157Cu could not restore the full adherence phenotype. Expression of truncated versions of His-tagged ToxB also promoted EspB production and/or secretion by O157Cu. These results suggest that ToxB contributes to the adherence of EHEC to epithelial cells through promotion of the production and/or secretion of type III secreted proteins.

Flow cytometric analysis of the heat shock protein 60 expressed on the cell surface of Helicobacter pylori

The expression of a 60-kDa heat shock protein (HSP60) on the cell surface of Helicobacter pylori was analysed by flow cytometry with polyclonal antibody directed to HSP60. All 13 strains of H. pylori examined expressed HSP60 on the cell surface, although the intensity of expression was different among the strains and depended on culture conditions. There was a correlation between the intensity of HSP60 expressed on the cell surface and the rate of adherence to human gastric carcinoma cells (MKN45) by H. pylori, but not with urease activity and production of vacuolating toxin. By flow cytometric analysis with monoclonal antibody (MAb) 3C8 against HSP60, the reactive epitope in the HSP60 of H. pylori was detected on the surface of MKN45 cells. Furthermore, it was shown that gastric epithelial cells were positively stained with MAb 3C8 in one of two biopsy specimens examined. These results suggest that there is a common epitope showing homology between H. pylori HSP60 and human gastric epithelial cells.

Heat-shock protein 60 homologue of Helicobacter pylori is associated with adhesion of H. pylori to human gastric epithelial cells.

A previous study reported a relationship between the expression of heat-shock protein 60 (HSP60) by Helicobacter pylori and its adhesion to human gastric carcinoma (MKN45) cells. To examine whether the HSP60 homologue of H. pylori is associated with the adhesion of H. pylori to human gastric epithelial cells, an inhibition assay of adhesion of H. pylori to MKN45 cells was performed by flow cytometric analysis with monoclonal antibody (MAb) designated as H20 recognising HSP60 of H. pylori. The rate of adhesion of H. pylori pretreated with MAbH20 to MKN45 cells was lower than that of untreated H. pylori. Primary human gastric epithelial cells from a patient with gastric cancer were also prepared for comparison in the inhibition assay with MAbH20. H. pylori adhered to the primary human gastric epithelial cells, and this adhesion was significantly inhibited by MAbH20. These results suggest that the H. pylori HSP60 homologue recognised by MAbH20 might be associated with the adhesion of H. pylori to primary human gastric epithelial cells as well as to cultured gastric cancer cells.

Molecular and Microbiological Characterization of Clostridium difficile Isolates from Single, Relapse, and Reinfection Cases

ABSTRACT In this study, we investigated the correlation between the microbiological characteristics of Clostridium difficile clinical isolates and the recurrence of C. difficile-associated disease (CDAD). Twenty C. difficile isolates recovered from 20 single infection cases and 53 isolates from 20 recurrent cases were analyzed by pulsed-field gel electrophoresis (PFGE) and PCR ribotyping, and the cytotoxicity, antimicrobial susceptibility, and sporulation/germination rates of the isolates were examined. Recurrent cases were divided into relapse or reinfection cases by the results of C. difficile DNA typing. Among the 20 recurrent cases, 16 cases (80%) were identified to be relapse cases caused by the initial strain and the remaining 4 cases (20%) were identified to be reinfection cases caused by different strains. All 73 isolates were susceptible to both vancomycin and metronidazole, but resistance against clindamycin, ceftriaxone, erythromycin, and ciprofloxacin was found in 87.7%, 93.2%, 87.7%, and 100% of the isolates, respectively. No correlations between DNA typing group, cytotoxicity, and sporulation rate of isolates and infection status, i.e., single, relapse, or reinfection, were observed. However, the isolates recovered from relapse cases showed a significantly higher germination rate when incubated in medium lacking the germination stimulant sodium taurocholate. These results indicate that the germination ability of C. difficile may be a potential risk factor for the recurrence of CDAD.

Immune Response against a Cross-Reactive Epitope on the Heat Shock Protein 60 Homologue of Helicobacter pylori

ABSTRACT We previously established a monoclonal antibody (MAb), designated H9, which reacts with the heat shock protein 60 (HSP60) homologue ofHelicobacter pylori as well as with other bacterial and human HSP60s. To determine the importance of a cross-reactive epitope on H. pylori HSP60 in H. pyloriimmunopathogenesis, we performed (i) mapping of an epitope on H. pylori HSP60 recognized by the H9 MAb, (ii) analysis of immunoglobulin G responses of patients with or without H. pylori infection to its epitope region, and (iii) studies of the protective effect of immunization with its epitope region onH. pylori infection in mice. The epitope recognized by the H9 MAb was mapped to the sequence of amino acids 189 to 203 (VEGMQFDRGYLSPYF) on the H. pylori HSP60 molecule. It was confirmed that the synthesized peptide designated pH9 was recognized by the H9 MAb. Enzyme-linked immunosorbent assay analysis showed that patients with H. pylori infection (n = 349) had significantly lower titers of pH9 antibody than did uninfected patients (n = 200) (P < 0.001), but this was not the case with purified H. pylori HSP60 recombinant Escherichia coli GroEL, or recombinant human HSP60. In C57BL/6 mice immunized with the pH9 peptide with Freunds complete adjuvant (FCA), the number of H. pylori organisms colonizing the stomach was significantly lower than that in mice immunized with pCont plus FCA (P < 0.0001) or FCA only (P < 0.005). The results suggest that the immune response to the cross-reactive epitope (pH9 region) on H. pylori HSP60 is unique and might be associated with protection against H. pylori infection.

Antifungal drug susceptibility of Cryptococcus neoformans from clinical sources in Nairobi, Kenya.

The serotypes and mating types of 80 clinical isolates of Cryptococcus neoformans from Kenya were studied and subjected to broth microdilution susceptibility testing to amphotericin B (AMP), flucytosin, fluconazole (FLC), itraconazole (ITC) and miconazole (MCZ). The isolates included C. neoformans var. grubii– 75 of 80 (serotype A; 93.7%), C. neoformans var. neoformans– three of 80 (3.8%) and C. neoformans var. gattii– two (serotype B; 2.5%). Mating experiment confirmed all the isolates to be α‐mating type. Seventy‐eight (97.5%) of the isolates had minimum inhibitory concentration (MIC) of ≤0.5 μg ml−1 to AMP and at 1 μg ml−1, 100% of the isolates were inhibited. Flucytosin resistance was observed in 21% with MIC in which 90% of the isolates were inhibited (MIC90) of 64 μg ml−1. Only 23.8% of the strains were susceptible to FLC with 65% susceptible dose‐dependent (SDD) and 11.2% resistant. Itraconazole susceptibility was 61.3% while the rest were either SDD or resistant. The MIC90 for ITC and MCZ were 0.5 and 2 μg ml−1 respectively.

Experimental infection of germ-free mice with hyper-toxigenic enterohaemorrhagic Escherichia coli O157:H7, strain 6.

A mouse enterohaemorrhagic Escherichia coli (EHEC) infection model was developed with a combination of germ-free (GF) mice and hyper-toxigenic EHEC (HT-EHEC) O157:H7 strain 6. The HT-EHEC strain 6 produced both Shiga-like toxin (SLT)-1 1.0 microg/mI and SLT-2 8.2 microg/ml in vitro. Eight-week-old germ-free mice were inoculated intragastrically with 5.0 x 10(7) cfu of HT-EHEC strain 6. All GF mice challenged with the HT-EHEC developed ruffled fur and convulsion of limbs or hindleg weakness within 3 days after the challenge, culminating in death within 5 days. The HT-EHEC colonised well at a level of 10(8) - 10(9) cfu/g of faeces 5 days after the challenge. Both SLT-1 and SLT-2 were demonstrated in the faeces of the mice for 5 days after challenge. Histological examination of the colons of the infected mice showed congestion of the lamina propria mucosa, mild inflammatory cell infiltration and goblet cell depletion. In proximal tubules of the renal cortex, epithelial swelling with scattered necrotic cells was recognised. Endothelial swelling and mononuclear cell infiltration were also observed in the glomeruli. The brain showed acute neuronal necrosis in the cerebrum and slight loss of Purkinje cells in the cerebellum. Passive immunisation with anti-SLT antisera prolonged the life of the mice without anyneural symptoms. Microscopically, all tissue specimens from the passively immunised mice were not remarkable. These results indicate that the infection of GF mice with HT-EHEC is a useful animal model to study the pathogenicity of SLT-producing E. coliand the toxins.

Establishment and characterisation of a monoclonal antibody to inhibit adhesion of Helicobacter pylori to gastric epithelial cells

Monoclonal antibodies (MAbs) that inhibit adhesion of Helicobacter pylori to human gastric cancer (MKN45) cells were established to clarify the mechanism of adhesion of H. pylori. Of 53 hybridoma clones screened by the primary inhibition assay for adhesion, MAb A20 of IgM class was selected on the basis of both its reactivity to whole cells of H. pylori by ELISA and its inhibitory effect on adhesion of H. pylori. The adhesion of H. pylori strain TK1029 to MKN45 cells was inhibited by MAb A20, depending on the concentration of the MAb. The MAb recognised the surface antigen, lipopolysaccharide (LPS) of H. pylori, suggesting that LPS is associated with adhesion of H. pylori to human gastric epithelial cells.

A virulence factor of Helicobacter pylori : Role of heat shock protein in mucosal inflammation after H. pylori infection

Among the various virulence factors of Helicobacter pylori the role of its heat shock protein 60 (HSP60, HspB) in mucosal inflammation after H. pylori infection was examined. In flow cytometric analysis, the expression of HSP60 on the cell surface was different, depending on the H. pylori strain used. The HSP60 epitope was also detected on the surface of both human gastric cancer cells (MKN45, KATOIII, and MKN28) and human gastric biopsy specimens. The intensity of the expression of HSP60 on the cell surface correlated significantly with the adhesion of H. pylori to MKN45 cells, but not with urease activity and production of vacuolating cytotoxin. A monoclonal antibody to H. pylori HSP60 inhibited the adhesion of H. pylori to MKN45 cells. These results suggest that HSP60 of H. pylori might act as an important virulence factor after H. pylori infection.

Induction of secretion of interleukin-8 from human gastric epithelial cells by heat-shock protein 60 homologue of Helicobacter pylori

Escherichia coli cells expressing fusion proteins consisting of beta-galactosidase and bacterial heat-shock protein (HSP) 60 of E. coli, Yersinia enterocolitica or Helicobacter pylori were constructed, and designated as HY1, HY2 or HY3, respectively. Fusion proteins prepared from HY2 and HY3 induced secretion of interleukin-8 (IL-8) from human gastric epithelial KATOIII cell cultures. On the other hand, the parent strain (E. coli pop2136), PEX (pop2136 transformed by vector) and fusion protein prepared from HY1 did not induce IL-8 secretion from KATOIII cells. Other human gastric (MKN45) and non-gastric cell lines (Int 407 and A549) did not secrete IL-8 following treatment with these proteins. These results indicate that H. pylori HSP60 induces IL-8 secretion from human gastric cells and the levels of IL-8 differ among the various gastric cell lines, suggesting that HSP60 might be an important virulence factor associated with chronic gastric inflammation following H. pylori infection in man.