In this study the importance of Providencia species as a cause of travellers' diarrhoea was examined using a selective medium developed by the authors. Providencia species could easily be distinguished from other enteric pathogens by the colour of the colonies obtained. Nine strains of Providencia alcalifaciens, nine of Providencia rettgeri and five of Providencia stuartii were isolated from 130 specimens, representing a surprisingly high incidence of infection compared with other pathogens isolated on SS agar and TCBS agar. Patients infected with P. rettgeri complained of abdominal pain, as for other Providencia species, but also of vomiting, which is rather characteristic of P. rettgeri infection. To analyse the pathogenicity of these isolates, their invasiveness was examined using Caco-2 cells. Most of the P. rettgeri strains invaded Caco-2 cells. Random amplified polymorphic DNA (RAPD) fingerprinting showed the same profile for two P. rettgeri isolates from individuals travelling in the same tour group. The results show that Providencia species, especially P. rettgeri, might cause diarrhoea, and that these species are important pathogens.

To test the ability of high-throughput DNA sequencing to detect bacterial pathogens, we used it on DNA from a patient's feces during and after diarrheal illness. Sequences showing best matches for Campylobacter jejuni were detected only in the illness sample. Various bacteria may be detectable with this metagenomic approach.

In 1996, Japan had several large outbreaks of enterohaemorrhagic Escherichia coli (EHEC) O157:H7 infection. We surveyed physicians who examined and treated these patients, and found that most of the patients (95.9%) received antimicrobial agents as treatments, in particular, fosfomycin comprised 84.0% of the prescribed treatment. Since the administration of antimicrobial agents for EHEC infection is under discussion, we also analyzed the effects of 7 antimicrobial agents including fosfomycin on the production and release of Vero toxins (VTs) by EHEC. The addition of fosfomycin into EHEC culture in CAYE broth at 5 h after the start of incubation caused a marked increase of VT1 release and production, as revealed by an immunological toxin assay (RPLA). However, a cytotoxicity assay of Vero cells showed a small increase of biological activity in the specimens treated with fosfomycin because the Vero cell assay reflects total cytotoxicity of VT1 and VT2. These results indicate that further study is necessary before concluding whether antimicrobial agents actually worsen an EHEC infection.

No abstract

Hemolysin produced by Vibrio hollisae (Vh-rTDH), which is related to the thermostable direct hemolysin (Vp-TDH) of Vibrio parahaemolyticus, was studied. Vh-rTDH was purified by successive column chromatographies on diethylaminoethyl-cellulose and an immunoaffinity column coupled with anti Vp-TDH immunoglobulin. The purified toxin was homogeneous, as demonstrated by conventional and sodium dodecyl sulfate--polyacrylamide gel electrophoresis (PAGE). The molecular weight of Vh-rTDH was slightly smaller than that of Vp-TDH, as determined by sodium dodecyl sulfate--slab gel electrophoresis. Conventional PAGE also showed a difference between Vh-rTDH and Vp-TDH. Vp-TDH and Vh-rTDH showed different lytic activities on erythrocytes from various animals, in particular chicken, sheep, and calf. The hemolytic activity of Vh-rTDH was heat labile when heated at 70 degrees C for 10 min, unlike Vp-TDH. Immunological cross-reactivity between Vh-rTDH and Vp-TDH was demonstrated by both the Ouchterlony test and neutralization test.