Many coliform rapid detection systems, which indicate post-pasteurization contamination in milk, have been developed recently. In the present study, one of these, the Sensi-Media method, was evaluated for the detection of coliforms in milk According to the manufacturer's instructions, 1ml of sample was inoculated into a readyto-use test tube (SensiMediaTM, MicroBio Corporation) containing EC Broth with sodium deoxycholic acid. Color change resulting from CO2 production by bacteria was monitored in a detection zone separated from the liquid medium by a gas-permeable membrane. The elapsed time until color changes was called detection time. Enterobacteriaceae containing coliforms and some non-fermentative Gram-negative bacteria in milk were detectable by the SensiMedia method. A significant correlation was observed between detection time and colony counts, and correlation coefhcients for each type of bacteria were 0.98 to 0.99.1 cfu/ml of bacteria such as Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Salmonella Typhimurium or Hafnia alvei were detected in about 15 hours at 37°C. Citrobacter freundii and Serratia liquefaciens were detected within 21 hours. These detection times were similar or shorter than the incubation time of the plate count method using Desoxycholate agar. Six strains of Gram-positive bacteria were all negative. By preliminary incubation of a 11 milk carton at 37°C for 6 hours, lessthan 10-2 cfu/ml of Enterobacteriaceae contaminants were cultured to more than 100 cfu/ ml, showing that the SensiMedia method could detect low levels of contamination rapidly (total 23 hours). These results indicate that the SensiMedia method is useful for the detection of postpasteurization contaminants in milk.
An outbreak of food-borne infection with enterotoxigenic Escherichia coli (ETEC) O6: H16 producing heat-labile enterotoxin and heat-stable enterotoxin occurred in Miyazaki Prefecture, Japan, in September 1999. During this outbreak, 211 out of 1, 439 people examined (14.7%) were affected. The major clinical symptoms were diarrhea and abdominal pain. However, data from epidemiological surveillance of infectious diseases in Miyazaki Prefecture showed that ten sporadic diarrhea cases caused by ETEC O6: H16 occurred diffusely in the prefecture for some weeks before and after this outbreak. In order to clarify the relationship between the outbreak and the sporadic cases, the isolates from each case were analyzed genetically by pulsed-field gel electrophoresis method (PFGE). As a result, the PFGE patterns of these isolates, except for one sample from a sporadic case, were observed to be the same, after cleavage of DNA with restriction enzymes Xbal, Notl and ApaI. These results suggest that the outbreak and the sporadic cases may have represented a diffuse outbreak initiated by contaminated foods appearing on the market in Miyazaki Prefecture.