The stock strains in our laboratory listed in Table 1 were used. All strains of Vibrio species were cultured aerobically in Nutrient Broth (Becton Dickinson Co., Sparks, MD, USA) containing 1.5% (wt/vol) NaCl. V. cholerae, V. mimicus, V. parahaemolyticus, V. alginolyticus, V. fluvialis, V. furnissii, V. vulnificus, V. metsuchinikovii and V. hollisae were cultured at 37°C for 16 hrs, whereas V. cincinnatiensis, V. harveyi, V. superstes, V. nigripulchritudo and V. neptunius were cultured at 26°C for 24 hrs. Strains of Campylobacter species except for C. rectus, C. concisus and C. curvus were subcultured on sheep blood agar (Nikken Bio Medical Laboratory Inc., Kyoto, Japan) at 37°C for 48 hrs, and a single colony of each strain was inoculated into Preston broth, which contained Bacto peptone (1.0%, wt/vol; Difco Laboratories, Detroit, MI, USA), Lab lemco powder (1.0%, wt/vol; Oxoid Co., Basingstoke, UK), PBS(−) (1.0%, wt/vol; Nissui Pharmaceutical Co., Tokyo, Japan), sodium pyruvate (0.025%, wt/vol; Kanto Chemical Co., Tokyo, Japan), sodium disulfite (0.025%, wt/vol; Kanto Chemical Co.) and iron(III)sulfate n-hydrate (0.025%, wt/vol; Kanto Chemical Co.), and cultured at 37°C for 16 hrs under the micro-aerophilic condition generated with the CampyPak plus micro-aerophilic system (Becton Dickinson Co.). Strains of C. rectus, C. concisus and C. curvus were cultured on sheep blood agar at 37°C for 48 hrs under micro-aerophilic conditions, and suspended in Preston broth. The CFU was counted using 2×YT agar containing 1.5% (wt/vol) NaCl for V. cholerae pure culture, TCBS agar (Oxoid Co.) for V. cholerae spiked in stools, TCBS agar for V. parahaemolyticus, and CCDA agar (Oxoid Co.) containing cefoperazone-amphotericin-teicoplanin (Kanto Chemical Co.) (16) for C. jejuni.
Salmonella enterica ss. enterica serovar typhi, S. enterica ss. enterica serovar typhimurium, Escherichia coli, Citrobacter koseri, C. freundii, C. amalonaticus, Enterobacter cloacae, Cronobacter aerogenes, E. sakazakii, E. cancerogenus, E. amnigenus, Klebsiella pneumoniae, K. oxytoca, Serratia marcescens, Proteus mirabilis, P. vulgaris, P. penneri, Hafnia alvei, Edwardsiella tarda, Providencia alcalifaciens, P. rettgeri, Morganella morganii, Yersinia enterocolitica, Staphylococcus aureus, Bacillus cereus, B. subtilis, Pseudomonas aeruginosa, Aeromonas hydrophila, A. caviae and A. veronii were cultured aerobically in Brain Heart Infusion broth (Beckton Dickinson Co.) at 37°C for 16 hrs. Bifidobacterium adolescentis, B. catenulatum, B. longum, Bacteroides fragilis, B. ovatus, Clostridium perfringens, Ruminococcus productus, R. obeum, Collinsella aerofaciens and Prevotella melaninogenica were cultured anaerobically in Modified GAM broth (Nissui Pharmaceutical Co.) containing 1.0% (wt/vol) glucose at 37°C for 24 hrs. Faecalibacterium prausnitzii and Eggerthella lenta were cultured anaerobically in Modified GAM broth containing 1.0% (wt/vol) glucose at 37°C for 72 and 48 hrs, respectively. Streptococcus bovis, S. mutans, Enterococcus faecalis, E. faecium, Lactobacillus acidophilus, L. casei and Lactococcus lactis were cultured anaerobically in Lactobacilli MRS broth (Becton Dickinson Co.) at 37°C for 24 hrs.