Citrobacter freundii possessing the common O antigen of Escherichia coli O157 was isolated from 5 (16.7%) of 30 raw fishes, 6 (4.1%) of 148 vegetables, 3 (3.4%) of 89 pieces of raw meat and 1 (0.9%) of 111 other foods during a survey of Shiga toxin-producing E. coli O157. Of 15 C. freundii strains, 13 (including one H2S-negative strain) were atypical because of positivity for both malonate and dulcitol. The results of cross-agglutination and agglutininabsorption tests indicated that the O antigen of C. freundii (both typical and atypical) was almost serologically identical to that of E. coli O157. In addition to a Salmonella O301 strain, isolated C. freundii strains hybridized to the rfbE (encoded E. coli O157 antigen) probe at low hybridization temperature, but did not hybridize at high hybridization temperature.
The effects of the fermented soybean product “Natto” on the composition and metabolic activity were studied in seven healthy volunteers (22-49 years of age) who ingested 50g of Natto/day for 14 days. During Natto consumption, the counts of Bacillus subtilis (B. natto;p<0.001) and Bifidobacterium (p<0.05) were significantly increased, except for the numbers of Bifidobacterium in two volunteers, whereas the counts and the frequency of occurrence of lecithinase-positive clostridia (p<0.05), including Clostridium perfringens were significantly decreased, when compared to the values before the consumption. The decreased tendency in the counts of Enterobacteriaceae and the increased tendency in the detection rate of B. subtilis were observed during the consumption, compared to the values before the consumption. No detectable changes occurred in the counts of other organisms throughout the experimental periods. The amounts of fecal acetic acid (p<0.05) during the consumption, and total organic acids and succinic acid (p<0.05) on day 14 of the consumption were significantly increased when compared to the values before and after the consumption. Fecal concentrations of phenol, ethylphenol, and skatol (p<0.05) were significantly decreased during the consumption. Fecal ammonia and cresol (p<0.05) were significantly decreased on day 14 of the consumption. Fecal pH values (p<0.05) were significantly decreased on day 14 of the consumption. The odor of the feces was slightly reduced during the consumption.
A fungal strain (NCI 3170) isolated from spoiled strawberry jam imported from Australia was morphologically identified as Eurotium halophilicum. This fungus grew well and produced lots of ascomata, and was white to pale yellow on M50YG agar and PDA with 15% NaCl. The anamorph of this fungus was not produced on 16 media for isolation and enumeration of common and xerophilic fungi. As results of the thermal death time tube method for heat resistance, most ascospores of this fungus, which were suspended in phosphate buffer saline (pH 7.4), survived at 60°C for 3hr, at 65°C for 20min, at 70°C for 2 min, and survivors were 4.5% at 65°C for 30 min, 2.4% at 70°C for 10 min, and 1.1% at 80°C for 2 min, respectively. Eurotium halophilicum NCI 3170 and two Japanese isolates from processed food were morphologically compared.
In September 1998, an outbreak of food poisoning caused by Salmonella Enteritidis was reported in Shiga Prefecture. Bacteriological and epidemiological studies identified frozen cream puffs as a source of this food poisoning. These frozen cream puffs contaminated by Salmonella Enteritidis had been produced by a manufacturer in Shiga Prefecture. Between the beginning of September and the beginning of October, these frozen cream puffs had been sold in 19 stores (17 of 19 stores were in Shiga Prefecture). Between the beginning of September and the beginning of November, many sporadic cases of Salmonella Enteritidis infection were reported that were suspected to be associated with this food poisoning as a result of drug susceptibility, plasmid profile, phage type and pulsed-field gel electrophoresis.
Kefir, which is a fermented milk product that was recently introduced in Japan is becaming available for widespread consumption. Because there is the effect of controlling the growth of food poisoning bacteria in acid milk, it is expected that the growth of E. coli O157: H7 in kefir can be similarly controlled. When E. coli ATCC or E. coli O157: H7 was cultivated in a pH-neutral condition, the growth of the bacterium was not influenced at all regardless of the presence of kefir. On the other hand, when E. coil ATCC or E. coli O157: H7 was cultivated in pH-acid condition, the growth of these was markedly inhibited. The growth of E. coli ATCC of 109 cfu/ml or E. coli O157: H7 of 107 cfu/ml to which kefir of pH 4 was added was especially completely inhibited in a short time. These results suggested that an antibacterial substance to the growth of E. coli ATCC or E. coli O157: H7 was existed in kefir.
The purpose of this study was to evaluate the isolated media of Salmonella and to determine the usefulness of practices used for isolation of Salmonella from food and feed. ES Salmonella medium was based on the use of X-GAL enzyme, and compared to other isolated media for detection of Salmonella. A total of 47 Salmonella and various gramnegative and gram-positive bacteria were used for evaluation of the media with testing by the method of Miles and Misra. Salmonella Enteritidis was put in liquid eggs, broilers and human feces to compare detection of Salmonella Enteritidis, and the contamination of Salmonella was examined for isolation from those by the selective medium. ES Salmonella medium was as effective or better than other commercial selective media such as DHL, MLCB, BG and SMID media for isolation of Salmonella. ES Salmonella medium was therefore considered effective for isolation of Salmonella from food and feed, but not from the samples of human feces.
During the period from January to June in 1998, a total of 180 raw meat samples comprising 100 chicken and 80 pork samples purchased from a supermarket in Hyogo Prefecture were examined for the presence of Staphylococcus aureus. It was found that 70 (70%) chicken and 29 (36.3%) pork samples were contaminated with S. aureus. Pulsed-field gel electrophoresis was applied for epidemiological analysis of the isolates. Seventy chicken isolates produced 15 (A-O) different patterns. Various genotypes of S. aureus were found in the chicken. Twenty-nine pork isolates produced 3 (A, P, Q) patterns. Interestingly, S. aureus showing the same pattern A was detected most frequently in both the chicken (n=18) and the pork (n= 24). In addition, pattern A was isolated repeatedly from the chicken and pork throughout the investigation. Eight (11.4%) of 70 chicken isolates produced enterotoxins A (n=5), B (n=1) and C (n=2). Four (13.8%) of 29 pork isolates produced only enterotoxin B. Sixty-three (90%) of 70 chicken isolates and 27 (93.1%) of 29 pork isolates were typable with eight coagulase-typing antisera. The most predominant coagulase types in chicken and pork isolates were types II (n=25) and V (n=21), and type V (n=21), respectively.