It is known that vegetables can serve as vehicles of food-borne illness when they are grown from seeds contaminated with pathogens. In this study, we investigated the fate of enterohemorrhagic Escherichia coli O157: H7 in experimentally contaminated radish and komatsuna seeds, after long-term storage at 4°C. The bacteria survived for 36 weeks in radish seeds initially contaminated at 103 cfu/ml, and 20 weeks survival . observed at as low as 102 cfu/ml. On komatsuna seeds, the bacterial count decreased more rapidly . Using scanning immunoelectron microscopy, the bacteria were detected on the surface of sprouts grown from contaminated seeds, and the bacteria were also present inside the stomata . However, heat treatmentat 100°C for 5 sec effectively eliminated the bacteria from the sprouts . These results underscore the possible health risk from contaminated vegetable seeds even after long-term storage at a low temperature, and also the importance of heat treating of harvested vegetables.
Salmonella contamination of raw meat from domestic chickens in Tama, Tokyo between 1992 and 1999, investigated. Salmonella was detected in 197 (25.2%) of 783 samples, raning from 9.4% to 40.8% per year. On serological typing test, 202 strains isolated were classified into 20 serovars including a strain of untypable O7 and O8. The most predominant serovar was Salmonella serovar Infantis (S. Infantis) (45.0%), following S. Hadar (6.9%), S. Typhimurium (4.5%), S. Schwarzengrund and S. Vichow (2.0%). Especially, the increases in S. Infantis in the past 3 years is notable, accounting for 77 strains (84.6%). On drug-resistance test using 9 drugs (CP, TC, SM, KM, ABPC, ST, NA, FOM and NFLX), 90% of strains tested were resistant to some of the drugs. S. Infantis isolated was resistant to all, and the main resistance patterns were TC/SM/KM/ST (28 strains), TC/SM/KM (26 strains), and TC/SM (20 strains). Almost all strains of S. Hadar and S. Typhimurium also were resistant to 2 to 5 drugs.