An isolate (T-1) from spoiled canned bamboo (Sasa kurilensis) shoots was morphologically and physiologically identified as Bacillus subtilis. When B. subtilis T-1 was cultivated with sterilized bamboo shoots at 30°C, shoots were degraded during the cultivation concomitant with an increase in the production of mono-and oligo-saccharides from hemicellulose.The cultivated medium contained several hemicellulose-degrading enzymes, e.g., β-xylanase and α-L-arabinofuranosidase. These results indicate that the enzymes from B. subtilis T-1 participate in the degradation of canned bamboo shoots.
A kit to detect Staphylococcus aureus, which often causes food poisoning and some other diseases, has been developed and commercially available. In the present study, the S. aureus rapid detection kit named “ Check Lite BH ” (Kikkoman Corporation) was evaluated andcompared with the conventional method. This kit was designed based on the enzyme-linked immunosorbent assay (ELISA), in which the bioluminescence method is applied. If protein A of S. aureus is detected, it can be judged that the existence of S. aureus was verified. This method began to be sold as a kit product, so we evaluated the application of this kit in a food microbiological test. (1) One hundred forty strains were examined. Ninety-five strains, which were identified to be S. aureus by traditional biochemical tests, were positive for bioluminescence activity by the kit. Thirty-five strains of Staphylococcus spp. except for S. aureus and 10 strains belonging to other genera of bacteria, which were identified by traditional tests, were all negative by this method, and cross reactions were not observed. (2) By “ direct method” (not enrichment), about 104 cfu/ml of S. aureus FRI196E were detectable from cross-contamination samples with other bacteria in about 2 hours. Marked influences due to the contamination of other bacteria were not observed. Moreover there was a significant correlation between relative light units (RLU) and colony forming units (CFU) in the range of 104 to 106 cfu/ml of S. aureus. (3) By the “ enrichment method” (culture for 7 hours), 101 cfu/ml of S. aureus FRI196E that was not detected on Egg-Yolk Mannitol Salt agar plate was detectable from the samples highly contaminated with 105 cfu/ml of other mixed bacteria within a total of 9 hours.
The utilization of constituents of an apple fruit as a growth substrate, the production of polysaccharide-hydrolases, and the degradation of fruit tissue by the enzymes were examined with three strains of Penicillium expansum (O-385-10, MR-213-3, and IFO8800) P. expansum grew well on an agar plate containing xylan or pectin as a carbon source, and abundantly produced conidiospores. On the other hand, the organism showed poor growth on glucose, fructose or sucrose, and the production of spores was repressed by these saccharides. Cellulose and starch did not support the growth of the organisms. Crude enzymes (xylanase and pectinase) were prepared from the culture broths of the organism grown in the xylan and pectin liquid media, respectively. When the small cubes of an apple fruit were incubated with the crude enzymes, these enzymes released a large amount of reducing sugars from the cubes. It was observed that the xylanase degraded cell walls of the fruit and the pectinase separated cells from the fruit cubes .
A method for the detection and enumeration of enterohemorhagic Escherichia coli (EHEC) O157 in various samples has been reported consisting of incubation on EC medium with novobiocin at 42°C for 18hr, and is recognized by the Japanese Ministry of Welfare as the official method on July 18, 1996 Some strains of EHEC can't be grown in this official method. The present study has shown that all of EHEC in TS broth with novobiocin grew better at 44.0°C than at 44.5°C and 42°C, and its strains were enough to be incubated the short time (3-6 hr) for the increase. In the immunomagnetic separation method, which is indispensable for the improvement of the detection rate, the stable high recovery percentage was obtained at ten minites of reaction. This combination method was shown to allow for very rapid and accurate deter-mination.
To investigate the effects of weather conditions on outbreaks of Salmonella food poisoning, the relationships of five weather indices, i.e., daily maximum, minimum and mean temperatures and minimum and mean humidity with daily outbreaks of Salmonella (S.Enteritidis) food poisoning by causes (incriminated food), i.e., eggs, non-eggs, and unidentified, were examined by multiple logistic regression analysis, for the years of 1989-95 in Japan, using outbreak of food poisoning as a dependent variable and five weather indices asindependent variables. During this period, the type of Salmonella detected in food poisoning cases was reported to be mainly Salmonella . Enteritidis, whereas Salmonella Typhimurium had been frequently found in the preceding years. The following results were obtained: (1) Salmonella food poisoning caused by eggs had positive relationships to the minimum temperature on the day of its outbreak and of one day before, and to the mean temperatures of two and three days before; (2) poisoning due to non-egg foods had positive relationships to the minimum temperatures of the outbreak day and of one, two, and three days before; (3) poisoning due to unidentified cause had positive relationships to the mean temperatures of the outbreak day and of one day before, and to the minimum temperatures of two and three days before. Increase in 1°C of the mean or minimum temperatures resulted in 7.2-12.2% increase in the risk of outbreak. It is thus suggested that high temperatures lead to outbreaks of Salmonella food poisoning regardless of the causative food for the years of 1989-95 in Japan, possibly due to the change in type of Salmonella.
Small round structured virus (SRSV) genes were detected from 14 of 1, 366 fecal samples which were collected from healthy food handlers working at school lunch facilitiesusing reverse transcription-polymerase chain reaction (RT-PCR) during one year between June 1997 and May 1998. The SRSV genes were detected from two persons after twoweeks but not after four weeks; thus, the excretion of SRSV genes was believed to continue for at least two weeks at least. Analysis of the SRSV gene sequences confirmed that these strains belonged to two different types in genogroup II of Norwalk-like viruses.
A PCR method was developed for the simultaneous detection of Escherichia coli O157 and H7 antigens. Two PCR primer pairs for amplification of both E. coli O157 rfbE and H7 fliC genes, which are necessary for the expression of the O157 and H7 antigen respectively, were performed for the detection of E. coli O157: H7. All Shiga toxin-producing E. coli (STEC) O157: H7 and STEC O157: NM strains were positive for both E. coli O157 rfbE and H7 fliC genes. Non-STEC O157 strains were positive only for E. coli O157 rfbE genes and H7 strains except O157 were positive only for H7 fliC genes . Some of the nonmotile strains were positive for H7 fliC genes. No cross-reaction was observed with other E. coli serotypes (except O157 and H7) and other bacterial species, like Salmonella O30 and Citrobacter freundii which react with E. coli O157 antiserum. It is recommended that PCR amplification of both E. coli O157 rfbE and H7 fliC genes is one of the most specific methods for E. coli O157: H7 identification.
ATP levels of bacteria in Tryptic Soy Broth with 0.5 to 8.7% (w/w) NaCl (water activity, aw 0.997-0.945) were studied during 3-day incubation period at 25°C by the luciferin-luciferase bioluminescence reaction method. The amount of intracellular ATP per cell of Staphylococcus epidermidis, Escherichia coli and Vibrio parahaemolyticus ranged from 1.3 to 6.1×10-18 mol/cell in the stationary phase. ATP content of bacterial cells varied greatly with age. The changes in aw had little effect upon the amount of ATP.
The cause of food decomposition is investigated in three cases, and the possibility of its recurrence is studied. The first case involves yellow discoloration of frozen “Mongou Cuttlefish” from Thailand. It was caused by the multiplication of Pseudomonas sp. Lack of proper sanitation in the fishing boat and the inadequate control of temperature between storage and processing caused the proliferation of the bacterium in question and the subsequent yellowish discoloration. The second case involves coagulation of non-dairy coffee cream. It was believed that the cause of the coagulation was Flavobacterium sp. or a closely related bacterium. The contamination by this bacterium was caused by the inadeauate maintenance of a filling machine. The third case, involving brownish discoloration of sliced and packed “Mochi” by heating, was caused by Enterobacteriaceae. It was presumed that a structural defect of the factory facility allowed the introduction of the causal bacteria into the factory, and the product became contaminated. The characteristic common to these three cases was insufficient measures of bacterial prevention. Therefore, adequate prevention is necessary before introducing management using the HACCP paradigm.