We studied on bacterial contamination of liquid eggs, intact eggs and manufacturing processes at liquid egg plant in 1990 and 1992, and inquired into the circumstances of GPcenters and liquid egg plants in Saitama Prefecture. Cracked eggs and dirty eggs were much more contaminated by bacteria than normal eggs. Good results were obtained on the liquid egg plant No. 1 in 1990, but many kind of Salomonella spp. were isolated from intact eggs, the manufacturing processes and liquid egg products in 1992. Almost all GPcenters washed eggs by a one-way style and almost all liquid egg plants sterilized the eggs with sodium hypochlorite before breaking them. Some liquid egg plants pasteurized liquid eggs by heating at 60°C for 3-5 min. To prevent the distribution of contaminated liquid eggs, not only hygienic management of the manufacturing processes but also heat pasteurization of liquid egg products is recommended.
A direct polymerase chain reaction method to EC cultured broth (named EC-PCR) for screening detection of enteropathogenic E. coli (ETEC, VTEC and EIEC) in foods and feces is described. Eleven E. coli strains belonging to three groups (4ETEC: 06, 025, 0128, 0148; 4VTEC: 026, 0111, 0145, 0157; and 3EIEC: 028ac, 0124, 0164) were used for this study. Four pairs of oligonucleotide primers homologous to LT, ST, VT and EIEC genes were used in combination. The culture condition at 37-43°C for 16-20 h in EC broth was most suitable for the EC-PCR method, and no cross readings were observed with other bacteria, substances in meats or feces. After a 20-h enrichment step, it was possible to detect fewer than 10 to 102 bacteria per g of the aritificially inoculated meat. E. coli was easily detected because of low contamination with other bacteria which disturb the detection of E. coli. However, in feces, it ranged from 103 to 104 cfu per g. The large number of bacteria with feces are the main limiting factor of the EC-PCR detection assay. All E. coli strains examined were detected from all the enrichment cultures on both the EC-PCR and the culture methods. In two sporadic cases and two food poisoning cases, the enteropathogenicity of E. coli isolates from patients was rapidly judged by the EC-PCR method. These findings were consistent with those of the culture method. Thus, the findings suggest that the EC-PCR method is a suitable, sensitive and rapid method for detection of the potentially enteropathogenic E. coli.
The genes (cry I, III, IV genes) encoding crystal protein body (CPB) producing Bacillus thuringiensis were analyzed by polymerase chain reaction (PCR) with synthetic oligonucleotide primers (Lep1A, Lep1B, Co12A, Co12B, Dip1 A and Dip1B). These primer pairs could amplify the 490, 797, 1060-bp region in cry genes. All CPB-producing B. thuringiensis strains tested yield an amplified DNA fragment, while non-CPB producing B. thuringiensis and B. cereus strains did not. The PCR provides a rapid and simple means to detect CPB-producing B. thuringiensis.
The commercial ELISA kit (Locate) was compared with a conventional culture method for the detection of Salmonella in foods. The sensitivity of the ELISA kit was detection of 106 cells/ml of S. Enteritidis, S. Tyhimurium and S. Infantis in pure culture. All of the 23 serovars of Salmonella tested gave correctly positive results, while the 7 strains of C. frendii gave correctly negative results. Raw meat and liquid egg which had been inoculated with low levels of different serovars of Salmonella gave positive results by the kit and culture method. In 50 samples of raw chicken, the correlation between the ELISA kit and culture method was very high, 98.0%. An ELISA false negative result was obtained in one sample. Salmonella recovered from the enrichment broth was not reactive with the ELISA, because the organism was covered with mucoid substance. The ELISA kit was found to be a rapid screening method for the detection of Salmonella in food.