Food safety knowledge and behavior of expanded food and nutrition education program participants in Arizona.

Consumer education is one of the focus points to reduce foodborne illness within the food safety continuum "from farm to table." A survey was conducted to determine the food safety knowledge and practices of the U.S. Department of Agriculture's Expanded Food and Nutrition Education Program participants in Maricopa and Pima counties of Arizona. Two hundred sixty-eight surveys were completed between 1 January and 31 December 1998. Survey participants consisted of 222 (85%) females and 39 (15%) males with an average age and education level of 31.5 and 11.7 years, respectively. The racial characteristics of this group included 53% whites, 32% Hispanics, 22% African-Americans, and 7% other. A majority of the survey participants (67%) were either unsure or felt it was appropriate to let food cool to room temperature prior to refrigeration. In addition 56% were in disagreement with or unsure about the need to cool foods in shallow containers. Fifty-two percent of respondents reported having no previous formal food safety education; for those who had, work was the most common source. Television news was the primary source of current food safety information for 50% of respondents. The most commonly consumed high-risk (i.e., raw or undercooked animal food or food purchased from unlicensed vendor) food was unpasteurized dairy products. Women scored significantly better than men on food safety knowledge and practice test parameters. Participants over age 50 had significantly higher food safety practice scores than the youngest age group. The food safety knowledge score of whites was significantly higher than that of Hispanics. It was determined for all participants that the food safety knowledge score had a small, positive effect on food safety practice score.

Multiplex polymerase chain reaction assay for genotyping Clostridium perfringens.

OBJECTIVE: To develop a multiplex polymerase chain reaction (PCR) assay to detect the genes for the major toxins of Clostridium perfringens (cpa [alpha toxin], cpb [beta toxin], etx [epsilon toxin], iA [iota toxin], and cpe [enterotoxin]). SAMPLE POPULATION: Cultures of C perfringens obtained from collections and diagnosticians throughout North America. PROCEDURE: PCR primers were derived from published sequences of the genes for the major toxins (the "typing" toxins and enterotoxin). The concentration of each primer was titrated in a PCR assay to allow concurrent amplification of multiple target sequences, and other parameters of the assay were optimized (including concentrations of other reagents and times and temperatures for denaturation of template, annealing of primers, and primer extension). Specificity of the assay was measured by comparing genotype with phenotype (where it was known). RESULTS: The genotype, determined by multiplex PCR assay, agreed with phenotype in 99% (86/87) of strains where phenotype had been determined. Applied to 361 isolates from domestic animals and human beings, 95% (n = 344) were type A, and 12.8% (n = 44) of these contained cpe. The remaining 5% (n = 17) of the isolates were type B (n = 1), type C (n = 11), type D (n = 2), or type E (n = 4). CONCLUSION AND CLINICAL RELEVANCE: Previous studies have documented usefulness of PCR in genotyping C perfringens. The multiplex assay is as effective, but simpler, and may be a useful alternative to standard in vivo typing methods. Results of genotyping of field isolates suggested the need for further epidemiologic study of clostridial enteritis, particularly as this pertains to predominant etiologic toxin types, and documented the presence of the reportedly rare genotypes B and E.

Human disease associated with Clostridium perfringens enterotoxin.

Clostridium perfringens continues to be a common cause of food-borne disease. Characteristics of this organism that contribute to its ability to cause food-borne illness include the formation of heat-resistant spores that survive normal cooking/heating temperatures, a rapid growth rate in warm food, and the production of enterotoxin (CPE) in the human gut. Time and temperature abuse associated with food preparation contributes to the majority of outbreaks of C. perfringens food-borne disease. CPE-induced diarrhea has been reported in the absence of a defined food vehicle. These cases have been typically associated with the elderly and following a course of antibiotic therapy. The incidence of CPE-induced diarrhea may be expected to increase with the growing population of immunocompromised (disease-, treatment-, or age-induced) individuals. Clostridium perfringens has been implicated as a possible contributor to the development of SIDS in susceptible individuals. Specifically, it has been hypothesized that CPE acts as a triggering agent, initiating the events associated with the development of SIDS. Continued refinement of both immunoassays and molecular methods for toxin and gene detection, respectively, will facilitate their eventual availability as commercial kits, providing rapid and simplified methods for the detection of C. perfringens isolates that produce or have the capacity to produce CPE as well as other toxins associated with this organism.

Immunochemical detection methods for Salmonella spp., Escherichia coli O157:H7, and Listeria monocytogenes in foods.

Immunochemical assays should prove to be a significant improvement over standard culture methods for the detection of foodborne pathogens. These techniques take advantage of the specificity and sensitivity of the antibody/antigen reaction for analyte detection. ELISA is the most useful form of immunochemical method for the detection of foodborne pathogens in the food-processing setting, based on their simplicity and ability to analyze large numbers of samples at a time. Concerns with immunochemical techniques include problems with cross-reactivity and difficulties obtaining species specific assays. Also, most immunochemical methods continue to require an enrichment technique; however, subsequent identification is quite rapid when compared with standard culture methods, therefore allowing for the quicker release of negative products.

Psychrotrophic Bacillus spp. in Fluid Milk Products: A Review.

Psychrotrophic bacteria have been recognized as a recurring problem in the refrigerated storage and distribution of fluid milk and cream and other perishable dairy products for several decades. Much emphasis has been focused on postpasteurization contaminants that are psychrotrophic, (e.g., Pseudomonas , Flavobacterium , and Alcaligenes spp.). Common sources of these gram-negative, non-sporeforming organisms are equipment surfaces and water supplies. Although these organisms are generally heat sensitive, many of their associated proteinases and lipases can withstand moderate to severe heat treatments and cause product deterioration. With the advance of improved control of postpasteurization contamination by nonheat-resistant psychrotrophs, more recent attention has been directed at psychrotrophic sporeformers and their potential impact on milk quality and shelf life properties. Heat-resistant psychrotrophs include members from the genera Clostridium , Arthrobacter , Microbacterium , Streptococcus , Corynebacterium , and Bacillus . However, the predominant microorganisms which comprise this category are Bacillus species. These bacteria can be introduced into milk supplies from water, udder and teat surfaces, or from soil and milkstone deposits on farm bulk tanks, pumps, pipelines, gaskets, and processing equipment. There is speculation that they can also be postpasteurization contaminants. When in the spore state, these microorganisms easily survive the typical range of pasteurization conditions with subsequent germination and outgrowth of vegetative cells. These organisms produce degradative enzymes (e.g., proteinases, lipases, and phospholipases) similar to those of non-sporeforming psychrotrophs. Enzymatic activity results in the development of objectionable flavor and quality defects in dairy products. The unique combination of both heat-resistant and psychrotrophic properties with the same microorganism represents substantial potential for causing spoilage of perishable milk products. Recent trends of higher pasteurization temperatures and extended refrigerated storage time of both raw and pasteurized milk and cream products exacerbates the significance of this group of microorganisms for the dairy foods industry.

Mathematical description of anaerobic treatment of wastewater in upflow reactors.

A quantitative description has been presented of anaerobic treatment in an upflow reactor of dilute wastewater containing lower fatty acids as the main pollutant. It contains as its principal elements mathematical descriptions of the dynamic behavior and the distribution of both the fluid and the anaerobic sludge in the reactor, and a quantification of the kinetics of the anaerobic conversion of the organic waste and of the formation of bacterial products and methane. These elements have been taken together in mass (organic carbon) balances for the substrate, the methane, and the bacterial products, over the two most important reactor parts: the sludge bed and the sludge blanket. In the second part of this article, the description has been used for prediction and determination of the optimum reactor dimensions and process conditions. These optimum values can be used for the design of new reactors and for the establishment of the best suited process operation, which is important for obtaining the best purification results and process reliability at minimum investment and operation costs.

Distribution and behavior of sludge in upflow reactors for anaerobic treatment of wastewater.

A model has been developed and experimentally checked for the physical behavior of sludge in the blanket in upflow reactors. The model is based on the mass balance for the sludge in the blanket, and can be used to predict the distribution of sludge in an upflow reactor in relation with the gas production, sludge settling characteristics, and the linear fluid velocity in the reactor. The quantitative values of the transport factors that are a measure of the efficiency of the transport of sludge by the fluid streams occurring in the reactor were determined experimentally in reactors of 30- and 200-m(3) volumes. As this was done for wastewater containing lower fatty acids as the main organic pollutants and for sludge with good settling characteristics, the predictive value of the model is limited. It may be used for the second (methane forming) step of anaerobic treatment of wastewater.

Fluid flow pattern in upflow reactors for anaerobic treatment of beet sugar factory wastewater.

Residence-time-distribution experiments for the fluid in a 30-m(3) pilot plant and a 200-m(3) prototype upflow reactor were performed by means of continuous injection of an LiCl solution as a tracer in the influent of the reactor and measurement of the response of this stimulus on several location in the reactor and in the effluent. In a similar way as described in an article published earlier, models have been developed by use of the measured data of the fluid flow pattern which consisted of region of ideal mixing, plug flow, dead space, and short circuiting. It appeared that the fluid flow patterns in the two reactors were to a large extent analogous. For the pilot plant, three-mixer models appeared to be appropriate while for the prototype reactor two-mixer models have been found. This differences was a result of the difference in the heights of the sludge beds in the reactors: 2-3 m in the pilot plant and only 0.4 m in the prototype reactor, a result of too small an amount of sludge. Another differences was that, due to large amount of mud in the prototype reactor, a region of dead space occurred in the models for the fluid flow pattern in this reactor. The dimension of the prototype reactor have been chosen according to several recommendations obtained from work with the pilot plant (e.g., scale-up should be done by increasing the cross section of the reactor; one influent point should be applied per 5 m(2) bottom surface). The results presented here clearly show the value of these recommendations.