We isolated and investigated Shiga toxin (Stx)-producing Escherichia coli (STEC) from feces of captured wild boars in the Toyama Prefecture. For detection of STEC, which were not grown in STEC-selective medium, we cultured fecal samples in a non-STEC selective medium and screened the samples by stx-PCR. Out of fecal samples obtained from 76 wild boars, stx was detected in 12 samples (15.8%) and STEC strains were isolated from seven stx-positive fecal samples (9.2%). The STEC isolates harbored the following serotype and stx: Og8 : H19 (stx2e), Og148 : H10 (stx2g), Og105 : H7 (stx2f), and Og4 : H27 (stx2g). Except for Og105 : H7, the isolates were LEE (locus for enterocyte effacement)-negative STEC, which did not harbor the eae gene. Also, these isolates were not grown in STEC-selective medium. The wild boars harboring STEC were distributed in particular regions and STEC Og8 : H19 isolated from four wild boars captured from the same region were found to harbor the same DNA pattern by pulse-field gel electrophoresis (PFGE) analysis. Og148 : H10 and Og4 : H27 harbored virulence-associated genes, EAST-1 and heat-stable enterotoxin gene. The findings of our study indicate that wild boars are the carriers of LEE-negative STEC harboring virulence-associated genes that are different from those of the serotype O157 : H7, which was prevalent STEC in humans.

We compared the detection rates for the prevalence of Campylobacter jejuni serotypes in Japanese samples by the conventional serotyping method (the Penner serotyping system) and a novel multiplex PCR genotyping method based on the Penner system. A total of 421 C. jejuni isolates from Tokyo (103 isolates from sporadic diarrheal patients and 318 isolates from food poisoning specimens) were examined. The total detection rates were 37.5% (158/421) by serotyping and 94.8% (399/421) by genotyping. By genotyping, the main serogroups detected were B, (HS: 2) 21.1% (89/421); D, (HS: 4 complex) 15.4% (65/421); G, (HS: 8,17) 9.0% (38/421); R, (HS: 23,36,53) 8.6% (36/421); and A, (HS: 1,44) 7.1% (30/421). Furthermore, 10 major serotypes covered 83.4% of all samples (351/421). However, 11 isolates were untypable by both serotyping and genotyping methods, and 11 other isolates serotyped as Z (HS: 38) were not typed by genotyping. Nevertheless, this novel genotyping method is effective and will contribute to updating and improving epidemiological data on C. jejuni infection and food poisoning.

Effects of corona discharge on growth of Morganella morganii and Photobacterium phosphoreum, well-known histamine-producing bacteria in foods, and on the activity of histidine decarboxylase that catalyzes histamine production were investigated. Effects of corona discharge on histamine itself were also investigated. Corona discharge generated at about 9 kV decreased the number of viable M. morganii and P. phosphoreum cells significantly at a distance of 11—14.5 cm for 18 hr discharge, and inhibited the activity of 0.7 µg purified histidine decarboxylase at a distance of 13 cm for 3 hr discharge. Notably corona discharge reduced the amount of histamine from 556 to 435 ng at a distance of 13 cm for 24 hr discharge. Corona discharge might be a promising method to prevent food poisoning caused by histamine accumulation through preventing the growth of histamine producing bacteria, inhibiting the activity of histamine synthase and reducing the amount of histamine.

Escherichia albertii is a newly emerging food-borne pathogen. However, infection routes to patients remain unclear. In the present study, we aimed to isolate and characterize E. albertii from environmental water in Akita Prefecture of Japan. E. albertii was detected in 16 of 52 samples by real-time polymerase chain reaction analysis, and a total of 13 E. albertii strains were isolated from 9 samples. None of isolates showed the properties of biogroup 1 or 2 described previously on indole production and lysine decarboxylase activity. Susceptibility testing against 11 antimicrobial agents showed that one isolate was resistant only to ampicillin (7.7%). All isolates were positive for eae and cdt as virulence genes, but were negative for stx, including stx2f. Pulsed-field gel electrophoresis analysis showed that E. albertii isolates were genetically heterogeneous, but two isolates from environmental water had the similarity of >80% to some E. albertii strains from humans. These results suggest that E. albertii derived from environmental water has the potential to infect humans.