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We identified hypervirulent Streptococcus pyogenes in 27 and 420 isolates from patients with invasive and non-invasive diseases, respectively, in Aichi Prefecture, Japan, between 2003 and 2012, in an attempt to understand why the prevalence of streptococcal toxic shock syndrome (STSS) suddenly increased in this location during 2011. Hypervirulent strains belong to the emm1 genotype, with a mutation in the covR/S genes that regulate many other genes, encoding virulence determinants and resulting in the absence of the proteinase streptococcal exotoxin B and the production of virulence factors such as the superantigen streptococcal exotoxin A, the nuclease streptococcal DNase, the cytotoxin NAD-glycohydrolase, and the hemolysin streptolysin O. We found 1 strain from invasive disease and 1 from non-invasive disease with traits similar to those of hypervirulent strains, except that the sda1 gene was absent. We also found 1 non-emm1 strain with phenotypic and genetic traits identical to those of the emm1 hypervirulent strains except that it did not belong to emm1 genotype, from non-invasive diseases cases in 2011. These findings suggested that hypervirulent and hypervirulent-like strains from invasive and non-invasive disease cases could have at least partially contributed to the sudden increase in the number of patients with STSS in Aichi during 2011.

The aim of this study was to examine the link between Campylobacter jejuni isolates obtained from chicken meat (n = 7) and gastroenteritis patients (n = 744). In total, 751 isolates were subjected to Lior serotyping. All the isolates from chicken meats were serotyped as Lior serotype 76 (LIO76). Among 23 of the identified LIO76 strains, 13 strains (6 from chicken meat and 7 from clinical specimens) were indistinguishable by Penner serotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis. These strains were isolated in 2 different Japanese prefectures in 2004-2005, suggesting that chicken meat is an etiological agent of Campylobacter gastroenteritis and that a diffuse outbreak occurred during this time. Therefore, a continuous surveillance program should be established in Japan in order to prevent Campylobacter gastroenteritis, especially large-scale food-borne outbreaks.

We developed an enrichment medium for use with the loop-mediated isothermal amplification (LAMP) assay (enrichment media + LAMP assay) to quickly increase a very small number of Vibrio parahaemolyticus cells to the detection limit of the assay. Thirty-nine different enrichment media were prepared based on evaluating 12 potential ingredients. From our assessment of the 39 media, enrichment medium #36, which contained 2% sodium chloride, 1% proteose peptone no. 2, 0.1% trehalose, 0.5% α-ketoglutaric acid, 0.25% pyruvic acid, and 0.5% yeast extract (pH 8.6), was found to be most effective at enhancing the proliferation of V. parahaemolyticus during incubation for 3 h at 40ºC. We compared the detection limits of the LAMP assay, the enrichment medium #36 + LAMP assay, and the cultivation method using bacterial cell and spiked shrimp sample tests. The detection limits of the LAMP assay, the medium #36 + LAMP assay, and the cultivation method were 10(3), 10(0)-10(-1), and 10(-1) CFU ml(-1), respectively. Enrichment medium #36 promoted a 10(3)- to 10(4)-fold increase in the bacterial population, and the detection limit of the enrichment media + LAMP assay was the same as that of the cultivation method.

Out of 68 Escherichia coli O157 field isolates tested in vitro for Shiga toxin (Stx) 2 production, 12 (17.6%) produced no or a limited amount of Stx2 (Stx 2 non- or low-producing strain; TNLP) even though all 68 possessed the stx(2) gene. The remaining 56 were Stx2 high-producing strains. The 12 TNLPs carried the q21 gene allele, which encodes a transcription antiterminator Q protein and is highly homologous to that of phi21 phage. They also carried nucleotide substitutions and insertions in the promoter region of the stx(2) gene compared with that of O157 EDL933, producing a considerable amount of Stx2. In contrast, the Stx2 high-producing strains carried the q933 gene allele, which was first reported on an stx(2) phage (933W), but not the q21 gene allele, and did not have mutations in the promoter region of the stx(2) gene. These 2 genetic characteristics, i.e., replacement of the q gene and mutation in the promoter region of the stx(2) gene, seemed to determine the amount of Stx2 produced by each strain. The TNLPs were more frequently isolated from healthy carriers than from patients (P<0.05), suggesting that TNLPs are less virulent than those with normal Stx2 production.

In order to evaluate reliability of pulsed-field gel electrophoresis (PFGE) analysis performed at different prefectural public health institutes (PHIs) for use in the PulseNet Japan surveillance system to detect enterohemorrhagic Escherichia coli O157, we compared the results of PFGE-typing of 14 selected strains of O157 performed at 8 selected PHIs to evaluate the reliability of different experimental protocols used in these PHIs. PFGE was performed for 14 strains for which there were 14 PFGE types in 3 PHIs, and 13 PFGE types in 5 PHIs by using their own protocols and/or those of the National Institute of Infectious Diseases (NIID). PFGE fingerprints from 5 out of the 8 PHIs were successfully genotyped for all of the 14 strains. A PFGE fingerprint from one PHI was successfully genotyped when the NIID pulsing protocol was used, but was not genotyped when the PHI's own protocols were used. PFGE fingerprints from 2 PHIs failed to be genotyped for one each of the strains. The cause of this genotyping failure was considered to be inappropriate PFGE pulsing protocols or inadequate digestion of chromosomal DNA. These results suggest that PFGE protocols should be standardized for the establishment of PulseNet Japan.