No abstract

There has been extensive media coverage of the Pacific Northwest outbreak of foodborne illness caused by Escherichia coli O157:H7 in 1993 and continuing smaller incidences of both E. coli and salmonella transmission by food. An increase in consumer awareness and knowledge of microbial food safety was expected as a result. A telephone survey of Oregon food preparers (using a random-digit-dialing household sample) in December 1995 and January 1996 revealed that knowledge about foodborne illness was greater than in previous studies. Of the 100 respondents, 88% named appropriate foods as being at high risk for food poisoning. Salmonella contamination was recognized as a problem in food by 99%, E. coli by 100%, but campylobacter by only 7%. Major foods which have been associated with salmonella were named correctly by 90% and with E. coli by 87%. Although raw or rare meats or fish were rarely eaten or ordered by respondents, hamburgers were frequently requested to be cooked to “medium” doneness. Many said they would thoroughly cook food contaminated with bacteria to make it safe to eat (56% for salmonella and 59% for E. coli) but 40% responded that the foods either couldn't be made safe to eat or that they didn't know of a way. Respondents in general could not identify specific groups of people especially at risk for foodborne illness. Educational efforts should focus on risk groups and ways that consumers can prevent foodborne illness.

Sprouts from nine producers were sampled from retail outlets and the microbial flora identified. Total aerobic plate counts were 108 cells/g; psychrotrophic counts were 107 cells/g; lactobacilli and fecal streptococci counts were low. Total coliforms and confirmed Klebsiella counts were each 106 cells/g. Fecal coliforms appeared to be part of the normal flora of sprouts (1,100 to 240,000 MPN per 100g). These were primarily K. pneumoniae. Sixty‐four percent of selected K. pneumoniae isolates were fecal coliform positive. The presence of K. pneumoniae in large numbers is a potential public health problem for people with decreased resistance.

A modified sporulation medium for Clostridium perfringens was formulated in which a larger number of spores were produced than in SEC broth and in which spores of greater heat resistance were produced than in Ellner's medium when it was also used as the suspending medium. This modified medium consisted of 1.5%, peptone; 3.0% Trypticase; 0.4% starch; 0.5% NaCl; and 0.02% MgSO4. The addition of 0.1% sodium thioglycolate and 0.0001% thiamine hydrochloride was optional. The optimal temperature for sporulation of five strains was 37 C in comparison with 5, 22, and 46 C. Sporulation had occurred by 6 hr and was essentially complete after 20 hr at 37 C. Noyes veal broth without glucose also supported the formation of heat-resistant spores but in smaller numbers than did the modified medium. Very low numbers of spores, or none, were produced under the same conditions in pea or tuna slurries.

Idaho Russet Burbank potatoes were surface or stab inoculated with 10 to 105 spores of Clostridium botulinum type A strain, overwrapped in aluminum foil, baked at 204 C for 50 min or 96 C for 3 h and then held at 22 or 30 C. The shortest incubations resulting in the first botulinogenic potatoes were inversely related to spore doses and ranged from 3 to 7 days; potatoes inoculated with 10 spores were toxic after 5 to 7 days. Total toxin in individual potatoes incubated 3 to 5 days were 5 × 103 to 5 × 105 mouse mean lethal doses. Toxin was not found at distances greater than 1.6 cm from the spore inoculation site. Results indicate that left-over, foil-wrapped, baked potatoes are a perishable food that must be refrigerated.