Japanese Journal of Food Microbiology
Online ISSN : 1882-5982
Print ISSN : 1340-8267
ISSN-L : 1340-8267
Volume 28 , Issue 2
Showing 1-17 articles out of 17 articles from the selected issue
Review
Symposium: A Present Status of Food Complaint and a Future View of Its Microbial Testing
Symposium: Food Pathogens to Be Paid Attention Now
Originals
  • Takashi KUDA, Akira MATSUDA, Hiroki YASUNAKA, Toshihiro YANO
    2011 Volume 28 Issue 2 Pages 114-122
    Published: June 30, 2011
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    To add unique flavors and favorable characteristics to alcohol drinks, we screened Saccharomyces cerevisiae strains from 14 municipal flowers, beach flowers and algal beach casts in Ishikawa, Japan. Among the 796 isolates, 63 strains from four municipal flowers and 6 strains from the algal beach casts produced 10% (v/v) ethanol in peptone-yeast extract broth containing 20% (w/v) glucose. From these strains, selected 24 strains were identified by characteristics of carbohydrate utilization and ITS gene sequencing. All of the strains were identified as S. cerevisiae. In the one-step small moromi model (2 g of Aspergillus oryzae malted rice (koji) and 4 g of α-processed rice were diluted to 17.5 ml with spring water) test at 15°C for 14 days, the isolates could produce sufficient amounts of ethanol (15-16%, v/v). In comparison with general sake-yeast Kyokai-No.7, the isolates had an increased acid value and lower pH. Malic acid content, which is regarded as a contributor of crispy and refreshing flavors in sake brewing, was increased significantly by an isolate from algae (Misaki-1). The algal strain differed from the flower-yeasts in carbohydrate utilization and 2,3,5-triphenyl tetrazolium chloride (TTC)-reducing activity. These results suggest that the S. cerevisiae strains isolated and selected in this study, particularly the algal-yeast Misaki-1, can be excellent starters for the brewing of sake and the other alcoholic drinks.
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  • Tomoe ISHIHARA, Ichiro FURUKAWA, Toshiro KUROKI, Tsutomu KAMIYAMA
    2011 Volume 28 Issue 2 Pages 123-127
    Published: June 30, 2011
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    We assessed the prevalence of isolates possessing extended-spectrum beta-lactamases (ESBLs) in community-acquired infections in Kanagawa Prefecture, Japan and the contamination rate in retail chicken meat. ESBL-producing Escherichia coli and Proteus mirabilis strains were isolated from 5.6% of patients (13/196) and 50.0% of chicken meat (17/34). ESBL-producing E. coli was isolated from 13 chicken meat samples and ESBL-producing P. mirabilis was isolated from 8 samples. Four samples were contaminated with both bacteria. PCR analysis revealed that all ESBL-producing E. coli from patients possessed CTX-M-type ESBLs. Seven of 13 E. coli strains had CTX-M-type, 5 had SHV and 3 had TEM, and 1 of 8 P. mirabilis strains had CTX-M-type ESBLs, 1 had TEM, 1 had SHV, 1 had TEM and SHV. Another 4 strains were not identified. Results suggest that contamination of chicken meat with ESBL-producing Enterobacteriaceae would cause the dissemination of ESBL-producing strains at the community level.
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  • Tetsuya AKIBA, Miyuki NAGANO, Tatsuya TANAKA, Kohji MORI, Yukinao HAYA ...
    2011 Volume 28 Issue 2 Pages 128-132
    Published: June 30, 2011
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Foodborne outbreaks caused by norovirus (NV) are increasing in Japan, however there is few cases that NV was detected from the suspicious causative food. Therefore, NV detection from various kinds of food including oysters have been investigated by many researchers. A bacterial cultivation process (A3T method) has been introduced into the standard protocol for NV detection. The A3T method is for removing contaminants derived from oysters. To simplify the process of the A3T method, we used a frozen bacterial culture in 15% glycerin. Next, we examined NV contamination in 102 commercialized oysters for both raw consumption and cooking by using a modified A3T method using 10% and 20% homogenates of oysters. NV RNAs were detected in 19 of 102 oyster samples by the modified A3T method, while no samples were detected by the standard method using a 10% homogenate. NV RNAs were also detected in 26 samples by the modified method using a 20% homogenate, whereas 3 NV positive samples failed to be detected when using a 10% homogenate. Results revealed that the modified A3T method using frozen bacterial culture is a practically useful method for detecting NV in oysters. Furthermore, the NV detection rate can be enhanced by using 20% homogenates of oysters. Moreover, the results suggest that NV contamination in oysters is more prevalent in our country than previously reported.
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  • Masashi KANKI, Kazuko SETO, Tetsuya HARADA, Yuko KUMEDA
    2011 Volume 28 Issue 2 Pages 133-138
    Published: June 30, 2011
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    We compared modified Escherichia coli broth containing novobiocin (mEC+n), modified Tryptic Soy Broth containing novobiocin (mTSB+n), Universal Preenrichment Broth (UPB) and mEC to analyze the enrichment of enterohemorrhagic E. coli (EHEC) serogroups O157, O26, O111 and O103 inoculated into goats' cheese and Gorgonzola cheese samples by the detection with loop-mediated isothermal amplification (LAMP), plating and immunomagnetic separation (IMS) assays. Cheese samples in mEC were incubated at 35°C according to Japanese standard method and those in the other broths were incubated at 42°C. There were significant differences in the detection of low amount of the refrigerate-injured EHEC strains in goats' cheese (1.3-2.6 CFU/25g) between enrichment in UPB and that in mEC (p=0.0016). There were significant declines in the ability to detect low amount of EHEC from Gorgonzola cheese (1.2-2.3 CFU/25g) in mEC compared with in mTSB+n and UPB (p<0.0010). With regard to high inoculation amount (12-23 CFU/25g), there was a significant difference in the detection of refrigerated-injured cells from Gorgonzola cheese samples between enrichment in UPB and that in mEC+n and mEC (p<0.0063). We consider that enrichment of injured EHEC strains in mEC particularly showed low performance because cultivation temperature was 35°C. Enrichment in UPB never showed decline in the detection ability. Non-selective enrichment broth is understandably necessary when a low number of cells or injury to cells is predicted. We expect that UPB can be a leading option among non-selective broths.
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Short Paper
  • Masashi FUJII, Junko YAMAMOTO, Hiroyuki MUKAI, Masahiro FUJITA, Hiroyu ...
    2011 Volume 28 Issue 2 Pages 139-142
    Published: June 30, 2011
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    We have studied the two assay methods of the 1Step Real-Time RT-PCR and conventional Real-Time RT-PCR (2Step) using ABI PRISM 7000 Sequence Detection System (ABI PRISM 7000) and Thermal Cycler Dice Real Time System (Thermal Cycler Dice) for the detection of Norovirus (NV) genogroups I (G1) and II (GII). Thermal Cycler Dice showed the same performance with the sensitivity and the quantitation compared with ABI PRISM 7000 that the official assay presented for the detection of NV. Both of the 1Step and 2Step Real-Time RT-PCR enabled to get the rapid results about 90 minutes. Excepting the probes with MGB, the primers and probes used in this study were identical with those used in the official assay. Results of field samples using both of the instruments and both of the assays were the same. Hence, these assays are very useful laboratory techniques for the detection of NV from field samples.
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