Rapiblot E. coli O157 is based on the use of anti-E. coli O157 antibody-coated Polymacron, as a high-surface-area immunoadsorbent for rapid capture and subsequent immunoenzyme detection of E. coli O157 antigens extracted from test samples by heating at 100°C for 10 minutes. Atotal of 24 non-E. coli O157 strains and various gram-negative and gram-positive bacteria tested gave negative results. The detection limit of Rapiblot E. coli O157 was 105cfu/ml in assays of E. coli O157 strains in broth suspension prepared by the spread plate method. This highly specific and sensitive selective antibody procedure was 98% effective when tested against IMS using ground beef and radish sprouts. The results obtained by Rapiblot E. coli O157 were the same or better than those of other commercial kits to detect E. coli O157. Rapiblot E. coli O157 was therefore considered effective for the detection of E. coliO157 in food.
The use of DNA-immobilized quartz crystal microbalance (QCM) for rapid detection of Salmonella has been demonstrated. The terminal 5'-phosphate group of a DNA fragment containing Salmonella-specific 464 bp DNA was modified with ethylendiamine. The DNA was denatured by heating and covalently immobilized via glutaraldehyde on a QCM treated with 3-aminopropyltriethoxysilane. The QCM immobilized with a single stranded DNA fragment containing the Salmonella-specific DNA was connected to Sogo Pharmaceutical Fragrance sensor SF-105W. The frequency of the QCM decreased by the addition of complementary single strand DNA. The frequency also decreased after incubation with the PCR reaction mixture from Salmonella-genomic DNA and du primer. However, the frequency did not decrease after incubation with phage DNA, plasmid DNA or PCR reaction mixtures from E. coli and B. cereus. The frequency change of the QCM after incubation with complementary DNA was closely correlated to the amount of DNA in the sample. The correlation coefficient was 0.995. Strand separation of the DNA-DNA hybrid at the surface of QCM was achieved by exposure to 10mM NaOH. This allowed the immobilized 464-mer DNA to be reused. Chicken meat inoculated with Salmonella Typhimurium IFO 12529 at 108 CFU/25g was cultured in EEM broth for 6h and selectively enriched in DMPBN medium for 18h. DNA was prepared from the culture and PCR was performed with the du primer. Using this Salmonella-specific DNA immobilized QCM, a decrease in frequency was detected with the PCR reaction mixture.
In April, 1997, the Ministry of Health and Welfare published the manual “Six Points for Prevention against Food Poisoning at Home” based on a new approach called HACCP. This manual, however, did not explain the various actual methods of washing hand. In order to determine the most effective method of washing hand in domestic kitchens, we investigated the survival rates of Escherichia coli (E. coli) on hands that had been washed several ways. The hands were first smeared with a mixture of beef paste and non-pathogenic E. coli, simulating the preparation of hamburger. The glove juice technique was used to collect the bacteria from the hand surface. As a result, we found a certain effectiveness in the use of medicated liquid soap with detergent activity and in duplicated use of non-medicated liquid soap. We further found that spraying ethanol onto hands after both using liquid soap and drying hands was more effective. The most effective method was rubbing hands with undiluted invert soap (10% w/v) for 30 seconds after washing with liquid soap. The method of washing hand should be chosen depending on how heavily the hands are contaminated with bacteria.