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.

INSECTICIDE RESIDUES437 producers being careful in selecting and buting feeds that are free of chlorinated insecticide residues, for use in their poultry operations. SUMMARY 1. Supplying the equivalent of 0.1 to 0.15 p.p.m. of lindane, dieldrin, heptachlor and DDT in the feed to laying hens in capsule form for 14 days resulted in some residues in chicken tissues which disappeared rapidly.2. Supplying the equivalent of 10 to 15 p.p.m. of the same insecticides in the feed for 5 days resulted in significant residues in eggs and abdominal fat which were extremely persistent.3. Care in feeding residue free feeds to laying flocks is extremely important.

Results of 1986 and 1995/6 statewide random surveys were compared to assess changes in the risk perceptions and food‐handling practices of Oregon food preparers. The 1986 survey revealed that perishable foods (baked potatoes, hard‐boiled eggs, sliced turkey and cream pie) were often held at room temperature for longer than 2–3 h. Those who perceived greater food safety risks were significantly less likely to report temperature abuse of cream pie (P < 0·02) and baked potatoes (P < 0·001). Respondents reported serving raw and/or rare animal products (fish, milk, hamburger and pork) in both surveys. More food preparers perceived that serving undercooked foods was a ‘high’ risk in 1995/6 than in 1986. More (88%) also perceived that serving raw hamburger was a ‘high’ risk in 1995/6 than in 1986 (52%), possibly because of media coverage linking under‐cooked hamburgers to the E. coli 0157:H7 outbreak in the Pacific Northwest. Those who perceived a ‘high’ risk were less likely to serve raw fish (P < 0·038) and raw milk (P < 0·002). Significantly more females perceived raw milk to be a ‘high’ risk (P < 0·003). The risks of consuming both raw fish and raw milk were more likely to be underestimated, however. Food safety education is therefore needed to help food preparers to identify ‘high’ risk foods and to motivate them to minimize risks.

Requirements in terms of water activity (a,) for the growth, sporulation, and germination of Clostridium perfringens were determined. Strain A48 was used in all phases, and in addition either NCTC 8239 or NCTC 8797 was used for growth, sporulation, and germination studies. The desired a, of the test media was obtained by the addition of one of three solutes: glycerol, sucrose, or sodium chloride. The freezing point depression method was used to determine the a,. The basal medium for growth and germination was Fluid Thioglycollate Medium. It had an a, of 0.995 and produced maximum growth and fastest growth rate among the six levels of a, tested. The lowest a, supporting growth and germination of C. perfringens was between 0.97 and 0.95 in the test media made with sucrose or sodium chloride and 0.93 or below in the test media adjusted with glycerol. Spore production by C. perfringens in Ellner's or modified medium required a higher a, than growth. An understanding of the influence of the available water in foods on the growth, sporulation, and germination of Clostridium perfringens may aid in control of this microorganism as a cause of foodborne illness. The available water activity (a,) in a food is affected by all of the constituents which have an affinity for water. These will include those which can be metabolized by the organism as well as those which cannot. In addition, food processing may alter the available water. Gough and Alford (5) tested the effects of NaCl, NaNO3, and NaNO2 on growth, survival, and heat resistance of several strains of C. perfringens. Growth occurred in concentrations of these salts which were higher than those used in the normal curing of meat. A NaCl concentration of 6% (w/v) in Fluid Thioglycollate Medium was required to inhibit growth significantly. The