Search

Reduction of enteric pathogens in animal manures before field application is essential for mitigating the risk of foodbome illness associated with produce. Aerobic composting of manures has been advocated as an effective treatment for reducing pathogen populations, and heat is a major factor contributing to pathogen inactivation. This study was initiated to determine the potential contribution of both thermal and nonthermal (pH, volatile acids, and ammonia) factors to pathogen inactivation during aerobic composting in bioreactors for mixtures containing manure from various sources (dairy, chicken, and swine). The test mixtures were formulated with an initial moisture content of 60% and a C:N ratio of 20:1, using straw and cottonseed meal as amendments. Mixtures were then inoculated with Salmonella and Listeria monocytogenes labeled with green fluorescent protein at initial populations of ca. 107 CFU/g. Three replicate trials of each treatment were conducted. Temperatures within the bioreactors were recorded at 30-min intervals, and duplicate samples were withdrawn daily from two sampling locations within the bioreactor. Significant regression models were derived relating decreases in pathogen populations to the degree of heat generated in the mixture (cumulative heat) and the pH of the mixture on the day before the pathogen losses were calculated (P < 0.0002). Although pathogens in swine manure compost mixtures were inactivated by the third day of composting, very little heat was generated in these mixtures, which were characterized by significantly higher levels of volatile acids compared with the other two compost mixtures. Therefore, volatile acids could help achieve pathogen inactivation when temperatures are too low such as when heat is lost too quickly at the surface of static compost piles or during winter composting. [ABSTRACT FROM AUTHOR]

Campylobacter is an important human pathogen, and consumption of undercooked poultry has been linked to significant human illnesses. To reduce human illness, intervention strategies targeting Campylobacter reduction in poultry are in development. For more than a decade, there has been an ongoing national and international controversy about whether Campylobacter can pass from one generation of poultry to the next via the fertile egg. We recognize that there are numerous sources of Campylobacter entry into flocks of commercial poultry (including egg transmission), yet the environment is often cited as the only source. There has been an abundance of published research globally that refutes this contention, and this article lists and discusses many of them. along with other studies that support environment as the sole or primary source. One must remember that egg passage can mean more than vertical, transovarian transmission. Fecal bacteria, including Campylobacter, can contaminate the shell, shell membranes, and albumen of freshly laid fertile eggs. This contamination is drawn through the shell by temperature differential, aided by the presence of moisture (the "sweating" of the egg); then, when the chick emerges from the egg, it can ingest bacteria such as Campylobacter, become colonized, and spread this contamination to flock mates in the grow house. Improvements in cultural laboratory methods continue to advance our knowledge of the ecology of Campylobacter, and in the not-so-distant future, egg passage will not be a subject continuously debated but will be embraced, thus allowing the development and implementation of more effective intervention strategies. [ABSTRACT FROM AUTHOR]

A cross-sectional study was performed to estimate the prevalence of Salmonella on retail market chicken carcasses in Colombia. A total of 1,003 broiler chicken carcasses from 23 departments (one city per department) were collected via a stratified sampling method. Carcass rinses were tested for the presence of Salmonella by conventional culture methods. Salmonella strains were isolated from 27% of the carcasses sampled. Logistic regression analysis was used to determine potential risk factors for Salmonella contamination associated with the chicken production system (conventional versus free-range), storage condition (chilled versus frozen), retail store type (supermarket, independent, and wet market), poultry company (integrated company versus nonintegrated company), and socioeconomic stratum. Chickens from a nonintegrated poultry company were associated with a significantly (P < 0.05) greater risk of Salmonella contamination (odds ratio, 2.0) than were chickens from an integrated company. Chilled chickens had a significantly (P < 0.05) higher risk of Salmonella contamination (odds ratio, 4.3) than did frozen chicken carcasses. [ABSTRACT FROM AUTHOR]

Sampling protocols for detecting Salmonella on poultry differ among various countries. In the United States, the U.S. Department of Agriculture Food Safety and Inspection Service dictates that whole broiler carcasses should be rinsed with 400 ml of 1% buffered peptone water, whereas in the European Union 25-g samples composed of neck skin from three carcasses are evaluated. The purpose of this study was to evaluate a whole carcass rinse (WCR) and a neck skin excision (NS) procedure for Salmonella and Escherichia coli isolation from the same broiler carcass. Carcasses were obtained from three broiler processing plants. The skin around the neck area was aseptically removed and bagged separately from the carcass, and microbiological analysis was performed. The corresponding carcass was bagged and a WCR sample was evaluated. No significant difference (α ≥ 0.05) in Salmonella prevalence was found between the samples processed by the two methods, but both procedures produced many false-negative Salmonella results. Prechill, 37% (66 carcasses), 28% (50 carcasses), and 51% (91 carcasses) of the 180 carcasses examined were positive for Salmonella by WCR, NS, and both procedures combined, respectively. Postchill, 3% (5 carcasses), 7% (12 carcasses), and 10% (17 carcasses) of the 177 carcasses examined were positive for Salmonella by the WCR, NS, and combination of both procedures, respectively. Prechill, E. coli plus coliform counts were 3.0 and 2.6 log CFU/ml by the WCR and NS methods, respectively. Postchill, E. coli plus coliform counts were 1.7 and 1.4 log CFU/ml by the WCR and NS methods, respectively. [ABSTRACT FROM AUTHOR]

An estimated 2,500 cases of listeriosis occur annually in the United States. Listeriosis is particularly severe among pregnant women and immunocompromised individuals. Little is known regarding the effect of the food matrix on the ability of L. monocytogenes to survive in the gastrointestinal tract and cause systemic infection. Mice were inoculated with various doses of L. monocytogenes in skim milk, Half & Half, or whipping cream to determine whether differences in milk fat content influence the ability of L. monocytogenes to survive passage through the gut and infect the liver or spleen. The number of fecal samples positive for L. monocytogenes increased with increasing doses of L. monocytogenes for all three vehicles. The number of L. monocytogenes cells isolated from liver or spleen of mice dosed with L. monocytogenes was not significantly different among treatment vehicles. Dose-response models revealed that as the dosage of L. monocytogenes was increased in different milk vehicles, the number of L. monocytogenes cells in liver or spleen also increased. Although fat content of food had no dose-dependent effect on L. monocytogenes infection in the murine gastrointestinal tract, we cannot discount the possibility that it may be a factor in L. monocytogenes infections of humans because of differences in the physiology of gastrointestinal tracts of mice and humans. [ABSTRACT FROM AUTHOR]

Data regarding Salmonella on raw poultry are very limited in China. The objective of this study was to determine the prevalence of Salmonel la on raw poultry at the retail level in six provinces and two national cities in China. Whole chicken carcasses (n = 1,152) were collected from three types of retail markets (large, small, and wet). All samples were analyzed for the presence of Salmonel la by using the U.S. Department of Agriculture, Food Safety Inspection Service method. Of 1,152 chicken samples, overall Salmonel la prevalence was 52.2%. The highest prevalence was observed in Guangxi Province (65.3%), next in Guangdong Province (64.6%), and then in Beijing (63.9%), Shaanxi Province (50.7%), Henan Province (47.9%), Shanghai (44.4%), and Fujian Province (42.4%), and lowest prevalence was observed in Sichuan Province (38.9%). Salmonel la prevalence was significantly different among the six provinces and two national cities. Salmonella prevalence was highest in the wet markets (54.4%) compared with the large markets (50.3%) and the small markets (52.1%), but differences were not significant (P > 0.05). Good manufacturing practices, good agricultural practices, and hazard analysis critical control point systems for Salmonel la control in poultry production at the farm, processing, and retail level should be implemented. [ABSTRACT FROM AUTHOR]

An antibacterial treatment consisting of 2% hydrogen peroxide at 50 degrees C for 60 s was evaluated for its effects on the sensory quality of fresh-cut iceberg lettuce. Treated lettuce was packaged in polyethylene film by a protocol used in the fresh-cut produce industry and then stored along with untreated controls for 3, 10, and 15 days at 5 degrees C. Gas chromatographic analysis confirmed that the desired initial volume (approximately 6 liters) and oxygen gas content (approximately 10%) were maintained during storage. Consumers from the local community who were the primary shoppers for their households and who purchased and ate lettuce regularly evaluated the appearance, color, aroma, flavor, and texture of the lettuce and their overall liking of the lettuce. Forty consumers were recruited to evaluate processing replication 1 on 26 April, and another 40 were chosen to evaluate processing replication 2 on 3 May. Because replication differences were observed in instrumental color measurements and in mean sensory ratings, replications were not pooled for the two test dates. Lettuce purchased for processing replication 2 was considerably greener than that used in replication 1. Overall, the antibacterial treatment was more effective than the control treatment in maintaining sensory quality over 15 days of storage, provided that the lettuce was initially intensely green. Three-fourths of the participants indicated that they would be willing to buy precut packaged lettuce that had already been treated at the packinghouse or processing plant with an antibacterial solution, and of these participants, 62.5% indicated that they would be willing to pay 5 to 10 cents more per bag.

An outbreak of Escherichia coli O157:H7 infection associated with the consumption of coleslaw in several units of a restaurant chain prompted a study to determine the fate of the pathogen in two commercial coleslaw preparations (pH 4.3 and 4.5) held at 4, 11, and 21 degrees C for 3 days. At an initial population of 5.3 log10 CFU/g of coleslaw, E. coli O157:H7 did not grow in either coleslaw stored at the three temperatures. Rather, the population of E. coli O157:H7 decreased by 0.1 to 0.5 log10 CFU/g within 3 days. The greatest reduction (0.4 and 0.5 log10 CFU/g) in population occurred at 21 degrees C, whereas only slight decreases (0.1 to 0.2 log10 CFU/g) occurred at 4 and 11 degrees C. A pH of 4.3 to 4.5 of coleslaw had little effect on reducing E. coli O157:H7 populations. Results suggest that the tolerance of E. coli O157:H7 to acid pH, not temperature abuse, is a major factor influencing the pathogen's fate in restaurant-prepared coleslaw.

An antibacterial treatment consisting of 1.5% lactic acid plus 1.5% hydrogen peroxide at 40 degrees C for 15 min was effective in reducing foodborne bacterial pathogens on raw apples. However, the effects of this treatment on an apple's sensory characteristics and the extent of consumers' willingness to use the treatment at home were not known. This study was undertaken to determine the sensory acceptability and chemical characteristics (pH, soluble solids, and total acidity) of apples subjected to the sanitizing treatment and to obtain information on consumers' purchase behavior, apple handling and consumption practices, and willingness to use an antibacterial treatment. Untrained consumers (n = 80) evaluated the appearance, color, aroma, flavor, texture, and overall appeal of untreated (control) and treated Red Delicious apples that had been stored at 5 degrees C for 0, 6, and 10 days. Panelists used a nine-point hedonic scale (1 = "dislike extremely"; 5 = "neither like nor dislike"; 9 = "like extremely") to evaluate sensory acceptability. Treatment and storage had no significant effect on the appearance, color, or aroma of the samples. Flavor ratings ranged from 6.2 ("like slightly") to 7.0 ("like moderately"). There was no significant difference among any of the control and treated apples stored for 0 days or among those stored for 6 days. Although apples stored for 10 days received the lowest ratings (6.2 to 6.3), they still had an acceptable flavor (6, "like slightly"), and panelists could not perceive differences between the control samples and the treated samples on day 10. The same trends were noted in texture ratings and in overall liking ratings. Treatment and storage had a minimal effect on pH (range, 3.96 to 4.02), soluble solids (range, 11.8 to 12.9 degrees Brix), and total acidity (range, 0.20 to 0.23% malic acid), which are important for apple flavor. Many consumers (87%) were concerned about fruit safety, and 53.2% were willing to try an antibacterial treatment at home. However, 74% would not be willing to use it if a 15-min heating-and-soaking step were required. Implementation of the treatment may be more feasible in the packinghouse than in the home.

Recent outbreaks of salmonellosis associated with orange juice have raised interest concerning the survival and growth of Salmonella in juice supplemented with calcium. A study was done to determine the influence of various calcium supplements on the survival of salmonellae in orange juice held at 4 degrees C for up to 32 days. Isolates of Salmonellal Muenchen (inoculum 1), Salmonella isolates from humans and animals (inoculum 2), and Salmonella isolates from produce outbreaks (inoculum 3) were inoculated into pasteurized orange juices with pH values ranging from 3.96 to 4.19 and containing 350 mg of calcium per 240-ml serving (1.46 mg of calcium/ml). Populations of Salmonella declined rapidly in juice containing calcium lactate (CaL), with counts decreasing from 4.86 log10 CFU/ml to < 1 log10 CFU/ml within 16 days, regardless of the Salmonella serotypes present in inoculum. Counts decreased from 4.89 log10 CFU/ml to < 1 log10 CFU/ml in orange juice supplemented with CaL and tricalcium phosphate (TCP) within 30 days. These reductions were significantly (P < or = 0.05) higher than those of the control (no calcium added), in which Salmonella populations decreased 3.19 +/- 0.20 log10 CFU/ml over 32 days. Populations in orange juice containing TCP or calcium citrate (CC) declined 1.34 +/- 0.20 log10 CFU/ml and 1.96 +/- 0.20 log10 CFU/ml, respectively, over 32 days. These counts were significantly higher than respective control counts in juice stored for 32 days. Populations of Salmonella of inoculum 3 inoculated into juice containing calcium citrate malate (CCM) were significantly higher than in the control. Higher numbers of cells in inoculum 3 also survived compared to numbers of cells of inocula 1 or 2 in juice supplemented with CCM. This study reveals that the form of calcium used to supplement orange juice influences the ability of salmonellae to survive.

Universal preenrichment broth (UPB) was developed to enable enrichment of injured foodborne pathogens of different genera simultaneously in lieu of having to undergo separate simultaneous enrichment cultures for subsequent detection or isolation of each pathogen. Enrichment conditions in UPB for growth of injured pathogens to populations that will enable pathogen detection by rapid immuno-based or polymerase chain reaction (PCR)-based assays have not been defined. Hence, studies were done to determine recovery and growth rates of heat-injured Escherichia coli O157:H7, Salmonella enterica ser. Typhimurium, Salmonella enterica ser. Enteritidis. and Listeria monocytogenes in UPB. Bacterial cells were heat injured in tryptic phosphate broth at 57.2 degrees C and inoculated at populations of ca. 0.17 to 63 injured cells per ml with raw ground beef, fresh chicken, lettuce, and environmental sponge samples. Enrichment cultures were sampled at 1, 2, 3, 4, 5, 6, and 24 h at 37 degrees C postinoculation, and pathogens were enumerated on appropriate selective media. Results revealed that recovery and growth of pathogens during the first 6 h of enrichment were not sufficient to ensure adequate numbers of bacteria (> 10(3) CFU/ ml) for detection by most immunoassays or PCR assays. Cells often required 3 to 4 h for recovery before growth was initiated. Salmonella Typhimurium, Salmonella Enteritidis, E. coli O157:H7, or L. monocytogenes cell populations in enrichment cultures with ground beef or lettuce at 6 h were 0.5 to 2.9 log10 CFU/ml. At 24 h of incubation, cell counts of enrichment samples for the three pathogens from all food and environmental sponge samples ranged from 4.0 to 8.3 log10 CFU/ml. Enrichment in UPB at 37 degrees C of foods or environmental sponge samples containing heat-injured cells of Salmonella Typhimurium, Salmonella Enteritidis, E. coli O157:H7, or L. monocytogenes reliably provides at 24 h of incubation-but not at 6 h-sufficient cell populations for detection by rapid immunoassay or PCR assay procedures that can detect at least 4 log10 CFU/ml. These results raise questions regarding the sensitivity of rapid detection methods that employ an abbreviated enrichment protocol of 6 h or less.

Six human isolates of Escherichia coli O157:H7 and E. coli (ATCC 11229) were used to determine the concentrations of free chlorine and exposure times required for inactivation. Free chlorine concentrations of 0.25, 0.5, 1.0, and 2.0 ppm at 23 degrees C were evaluated, with sampling times at 0, 0.5, 1.0, and 2.0 min. Results revealed that five of six E. coli O157:H7 isolates and the E. coli control strain were highly susceptible to chlorine, with >7 log10 CFU/ml reduction of each of these strains by 0.25 ppm free chlorine within 1 min. However, comparatively, one of the seven strains was unusually tolerant to chlorine at 23 degrees C for 1 min, with a 4-, 5.5-, 5.8-, and >5.8-log CFU/ml reduction at free chlorine concentrations (ppm) of 0.25, 0.5, 1.0, and 2.0. respectively. Based on these studies most isolates of E. coli O157:H7 have no unusual tolerance to chlorine; however, one strain was exceptional in being recovered after 1-min of exposure of 10(7) CFU/ml to 2.0 ppm of free chlorine. This isolate may be a useful reference strain for future studies on chlorine tolerance of E. coli O157:H7.

Studies were done to determine the survival of salmonellae in orange juice as affected by fortification with calcium. Four brands of commercially pasteurized orange juice fortified with calcium (350 mg/240-ml serving) and nonfortified juice were inoculated separately with three types of inocula: strains of Salmonella Muenchen (inoculum 1), serotypes of human and animal origin (inoculum 2), and isolates from raw produce- and juice-associated outbreaks (inoculum 3). Juice inoculated with populations of 6.6 to 7.0 log10 CFU of Salmonella per ml was held at 4 degrees C for up to 32 days. The number of cells of inoculum 1 that survived in juice fortified with calcium lactate/tricalcium phosphate (CaL/TCP) was significantly lower (P < or = 0.05) (2.80 log10 CFU/ml) than in nonfortified juice (3.50 log10 CFU/ml) after 32 days' storage. Death of salmonellae in inocula 1 and 2 was less in juice fortified with TCP (3.21 and 3.33 log10 CFU/ml, respectively) than in the nonfortified juice (3.75 and 4.15 log10 CFU/ml, respectively). During the 32-day storage period, populations in inocula 1 and 3 showed significantly less inactivation (2.62 and 3.12 log10 CFU/ml, respectively) in juice fortified with calcium citrate (CC) than in nonfortified juice (3.14 and 3.60 log10 CFU/ml, respectively). There were no significant differences in the survival of Salmonella in juice fortified with calcium citrate malate (CCM) and nonfortified juice. Polymerase chain reaction (PCR) typing of randomly selected Salmonella colonies revealed that Salmonella Heidelberg in inoculum 2 and Salmonella Baildon and Salmonella Poona in inoculum 3 were the most prevalent at the end of the 32-day storage period at 4 degrees C, suggesting that serotypes selected for use in inocula differed in tolerance to acidic environments. This study reveals that the form of calcium used to fortify orange juice may affect the survival of Salmonella.

Calves inoculated with Escherichia coli O157:H7 and fed either a high-roughage or high-concentrate diet were evaluated for rumen proliferation and fecal shedding of E. coli O157:H7. Calves fed the high-roughage diet had lower mean rumen volatile fatty acid concentrations and higher rumen pH values than did calves fed the high-concentrate diet. Despite these differences in rumen conditions, the calves fed the high-roughage diet did not have greater rumen populations of E. coli O157: H7 and did not exhibit increased or longer fecal shedding compared with the calves fed the high-concentrate diet. Two calves shedding the highest mean concentrations of E. coli O157:H7 were both fed the high-concentrate diet. There was a significant (P < 0.05) positive correlation between fecal shedding and rumen volatile fatty acid concentration in calves fed a high-concentrate diet. The effects of diet on E. coli O157:H7 proliferation and acid resistance were investigated using an in vitro rumen fermentation system. Rumen fluid collected from steers fed a high-roughage diet, but not from steers fed a high-concentrate diet, supported the proliferation of E. coli O157:H7. Rumen fluid from steers fed a high-concentrate diet rapidly induced acid resistance in E. coli O157:H7. The impact of diet on fecal shedding of E. coli O157:H7 is still unclear and may depend on dietary effects on fermentation in the colon and on diet-induced changes in the resident microflora. However, rapid development of acid tolerance by E. coli O157:H7 in the rumens of calves fed high-concentrate diets, allowing larger populations to survive passage through the acidic abomasum to proliferate in the colon, may be one factor that influences fecal shedding in cattle on feed.

Outbreaks of shigellosis associated with chopped parsley used as a garnish for foods occurred in four states in the United States and in two Canadian provinces in 1998. This prompted a study to determine survival and growth characteristics of Shigella sonnei inoculated onto raw parsley. Two inoculum levels (approximately 10(3) and 10(6) CFU/g) were applied to parsley leaves, portions of which were then chopped. Inoculated whole and chopped parsley leaves were held at 4 degrees C or 21 degrees C for up to 14 days. Initial populations of the organism on chopped parsley receiving high or low levels of inoculum increased by approximately 3 log10 CFU/g, within 1 day at 21 degrees C. Populations of S. sonnei on inoculated chopped or whole parsley leaves held at 4 degrees C decreased by 2.5 to 3.0 log10 CFU/g during a 14-day storage period. The pathogen multiplied, without a lag phase, on inoculated (2.72 log10 CFU/g) chopped parsley held at 21 degrees C, exceeding 6 log10 CFU/g within 24 h. Treatment of inoculated whole parsley leaves with vinegar containing 5.2% (vol/vol) acetic acid or 200 ppm free chlorine for 5 min at 21 degrees C reduced the population of S. sonnei by more than 6 log10 CFU/g, whereas treatment with vinegar containing 7.6% acetic acid or 250 ppm free chlorine reduced initial populations of 7.07 and 7.26 log10 CFU/g, respectively, to undetectable levels (<0.6 log10 CFU/g). These studies revealed that S. sonnei can grow rapidly on chopped parsley held at ambient temperature and remain viable for at least 14 days at 4 degrees C. Treatment of contaminated parsley with vinegar or chlorinated water offers a simple method to reduce markedly or eliminate the pathogen in food-service or home settings.

An outbreak of Campylobacter enteritis was associated with a restaurant in Louisiana during the summer of 1995. Thirty cases were identified, and four required hospitalization. Campylobacter jejuni was isolated from the patients, and epidemiologic studies revealed illness associated with eating garlic butter served at the restaurant. Three batches of garlic butter prepared by the restaurant associated with the outbreak and a C. jejuni isolate obtained from a patient involved in the outbreak were used for studies to determine the fate of C. jejuni in garlic butter. Studies also were done to determine the efficacy of the heat treatment used by the restaurant to prepare garlic bread to kill C. jejuni. Garlic butter was inoculated with approximately 10(4) and 10(6) CFU/g of C. jejuni and held at 5 or 21 degrees C. Results revealed that the survival of C. jejuni differed greatly, depending on the presence or absence of garlic. At 5 degrees C, C. jejuni populations decreased to an undetectable level (<10 CFU/g) within 3 h for two batches and within 24 h for another batch. In contrast, C. jejuni could survive at 5 degrees C for 13 days in butter with no garlic. At 21 degrees C, C. jejuni populations decreased to an undetectable level within 5 h for two batches and to 50 CFU/g in 5 h for another batch. In contrast, C. jejuni was detected at 500 CFU/g at 28 h after inoculation but was undetectable at 3 days in butter with no garlic held at 21 degrees C. The heating procedure (135 degrees C, 4 min) used to make garlic bread by the implicated restaurant was determined not to be sufficient for killing C. jejuni, with the internal temperature of the buttered bread after heating ranging from 19 to 22 degrees C. This study revealed that C. jejuni can survive for many days in refrigerated butter, but large populations (10(3) to 10(5) CFU/g) are killed within a few hours in butter that contains garlic. Furthermore, the heat treatment used by the restaurant to melt garlic butter in making garlic bread was not adequate to kill C. jejuni.

One milliliter of culture containing a five-strain mixture of Escherichia coli O157:H7 (approximately 10(10) CFU) was inoculated on a 100-cm2 area marked on unscarred cutting boards. Following inoculation, the boards were air-dried under a laminar flow hood for 1 h, immersed in 2 liters of electrolyzed oxidizing water or sterile deionized water at 23 degrees C or 35 degrees C for 10 or 20 min; 45 degrees C for 5 or 10 min; or 55 degrees C for 5 min. After each temperature-time combination, the surviving population of the pathogen on cutting boards and in soaking water was determined. Soaking of inoculated cutting boards in electrolyzed oxidizing water reduced E. coli O157:H7 populations by > or = 5.0 log CFU/100 cm2 on cutting boards. However, immersion of cutting boards in deionized water decreased the pathogen count only by 1.0 to 1.5 log CFU/100 cm2. Treatment of cutting boards inoculated with Listeria monocytogenes in electrolyzed oxidizing water at selected temperature-time combinations (23 degrees C for 20 min, 35 degrees C for 10 min, and 45 degrees C for 10 min) substantially reduced the populations of L. monocytogenes in comparison to the counts recovered from the boards immersed in deionized water. E. coli O157:H7 and L. monocytogenes were not detected in electrolyzed oxidizing water after soaking treatment, whereas the pathogens survived in the deionized water used for soaking the cutting boards. This study revealed that immersion of kitchen cutting boards in electrolyzed oxidizing water could be used as an effective method for inactivating foodborne pathogens on smooth, plastic cutting boards.

The fate of foodborne pathogens Escherichia coli O157:H7 and Salmonella Enteritidis on coin surfaces was determined at room temperature (25 degrees C). A five-strain mixture of E. coli O157:H7 or Salmonella Enteritidis of approximately 5 x 10(4) CFU was applied to the surfaces of sterile U.S. coins (pennies, nickels, dimes, and quarters) and to the surfaces of two control substrata (Teflon and glass coverslips). During storage at room temperature, E. coli O157:H7 survived for 7, 9, and 11 days on the surfaces of pennies, nickels, and dimes and quarters, respectively. However, the pathogen died off within 4 to 7 days on both the Teflon and glass surfaces. Salmonella Enteritidis survived for 1, 2, 4, and 9 days on the surfaces of pennies, nickels, quarters, and dimes, respectively. Unlike E. coli O157:H7, survival of Salmonella Enteritidis was greatest on both Teflon and glass coverslips, with more than 100 cells per substratum detected at the 17th day of storage. Results indicate that coins could serve as potential vehicles for transmitting both E. coli O157:H7 and Salmonella Enteritidis.

The antibacterial activity of lactoferricin B on enterohemorrhagic Escherichia coli O157:H7 in 1% peptone medium and ground beef was studied at 4 and 10 degrees C. In 1% peptone medium, 50 and 100 microg of lactoferricin B per ml reduced E. coli O157:H7 populations by approximately 0.7 and 2.0 log CFU/ml, respectively. Studies comparing the antibacterial effect of lactoferricin B on E. coli O157:H7 in 1% peptone at pH 5.5 and 7.2 did not reveal any significant difference (P > 0.5) at the two pH values. Lactoferricin B (100 microg/g) reduced E. coli O157:H7 population in ground beef by about 0.8 log CFU/g (P < 0.05). No significant difference (P > 0.5) was observed in the total plate count between treatment and control ground beef samples stored at 4 and 10 degrees C. The antibacterial effect of lactoferricin B on E. coli O157:H7 observed in this study is not of sufficient magnitude to merit its use in ground beef for controlling the pathogen.

Nine weaned calves aged from 8 to 12 weeks were fitted with rumen cannulas and were inoculated by cannula with 10(10) CFU of a five-strain mixture of nalidixic acid-resistant Escherichia coli O157:H7. Six calves were fasted for 48 h on days 15 and 16 and days 22 and 23 after inoculation. Samples of rumen contents and feces were obtained daily to enumerate E. coli O157:H7 populations and to determine rumen volatile fatty acid (VFA) concentrations and rumen pH. Fasting resulted in a marked decrease in rumen VFA concentrations from a mean of 135 mmol/liter before the fast to a mean of 35 mmol/liter during the second day of the fast. However, there was no correlation between daily VFA concentration and daily rumen or fecal numbers of E. coli O157:H7 in any of the calves. Fasting generally had no significant effect on the rumen or fecal numbers of E. coli O157:H7. The exception was a single fasted calf that experienced a 3-log(10) CFU/g increase in fecal shedding during and after the first fast. Despite the consistent changes in VFA concentrations in fasted calves, the fluctuations in rumen numbers of E. coli O157:H7 in the rumen of fasted calves were minimal. At the end of the experiment, E. coli O157:H7 was detected in either the rumen or omasum in two of three control calves at necropsy and in either the rumen or reticulum in five of six fasted calves. E. coli O157:H7 was detected in the colon in two of three control calves and in six of six fasted calves at necropsy. These results suggest that in cattle already shedding E. coli O157:H7, feed withdrawal and the associated changes in rumen pH and VFA concentrations have little effect on fecal shedding and rumen proliferation of E. coli O157:H7.

The production of toxin by a 10-strain mixture of proteolytic Clostridium botulinum in fresh produce packaged in polyethylene films with different oxygen permeability was determined. Broccoli florets, shredded carrots, and green beans inoculated with approximately 10(2) C. botulinum spores per g were placed in bags (1.4 kg per bag) composed of four films with different oxygen transmission rates (OTRs). Broccoli was packaged in bags with OTRs of 3 (7,000 cm3/m2/24 h) and 4 (16,000 cm3/m2/24 h), and green beans were packaged in bags with OTRs of 2 (6,000 cm3/m2/24 h) and 4. Broccoli and green beans in bags were compressed and heat-sealed. Shredded carrots were packaged in bags with OTRs of 1 (3,000 cm3/m2/24 h) and 3 and vacuum-sealed. Produce was stored at 4, 13, and 21 degrees C for up to 27 (broccoli) or 28 (carrots and green bean) days and analyzed periodically. At each sampling time, gas composition within the bags, pH of the produce microbial population (total aerobic and anaerobic microorganisms, lactic acid bacteria, psychrotrophic bacteria, yeasts, and molds), and the presence or absence of botulinal toxin were determined. Packaging material affected the quality of vegetables, especially broccoli stored at 4 and 13 degrees C. For example, broccoli was scored as "good" after 22 days at 4 degrees C when it was packaged in film with higher gas permeability (OTR of 4), whereas broccoli appeared to be in "poor" condition when packaged in film with lower gas permeability (OTR of 3). With the exception of lactic acid bacteria, packaging material did not noticeably influence the growth of microorganisms. Lactic acid bacteria grew better in broccoli packaged in bags with an OTR of 3 than in those with an OTR of 4 at all temperatures. Botulinal toxin was detected in broccoli packaged in bags with an OTR of 3 and stored at 13 degrees C for 21 days and in those with an OTR of 4 and 3 and stored at 21 degrees C for 10 days. All toxic samples were visibly spoiled. Toxin was not detected in produce packaged under any other test conditions.

Antibiotic resistance was determined for 118 E. coli O157:H7 and 7 O157:NM isolates from animals, foods, and humans. Among the 125 isolates, 30 (24%) were resistant to at least one antibiotic and 24 (19%) were resistant to three or more antibiotics. Cattle isolates had the highest rate (34%) of antibiotic resistance. The seven resistant food isolates were all from ground beef. The most frequent resistance type overall was streptomycin-sulfisoxazole-tetracycline, which accounted for over 70% of the resistant strains. Two E. coli O157:NM isolates from cattle were resistant to six antibiotics: ampicillin, kanamycin, sulfisoxazole, streptomycin, tetracycline, and ticarcillin. Streptomycin was the most common antibiotic to which E. coli O157:H7 and O157:NM were resistant (29 out of 30 isolates), followed by tetracycline (26 isolates). This study suggests that E. coli O157:H7 and O157:NM have developed resistance to antibiotics. Research is needed to define mechanisms of antibiotic resistance in E. coli O157:H7 and to minimize the development of resistance.

The production of toxin by a 10-strain mixture of proteolytic Clostridium botulinum in fresh produce packaged in polyethylene films having high (7,000 cc/m2/24 h; HOTR) and low (3,000 cc/m2/24 h; LOTR) relative oxygen permeability was determined. Shredded cabbage and lettuce inoculated with approximately 10(2) spores/g were placed in bags composed of the two films (1.4 kg/bag), and the bags were then vacuum sealed. Produce was stored at 4, 13, and 21 degrees C for up to 21 (cabbage) or 28 (lettuce) days and analyzed periodically. At each sampling time, the gas composition within the bags, pH of the produce, and microbial populations (total aerobic and anaerobic microorganisms, lactic acid bacteria, psychrotrophic bacteria, and yeasts and molds) were determined. In addition, the presence of botulinal toxin was determined using the standard U.S. Food and Drug Administration mouse bioassay protocol. Bags made of HOTR film prolonged sensory quality of cabbage and lettuce, especially at 13 and 4 degrees C. Packaging material had an effect on the growth of various groups of microorganisms; however, there was not a general trend. For example, lettuce packaged in HOTR bags had higher aerobic microbial populations than that packed in LOTR, but no significant difference (P < or = 0.05) was observed with cabbage. Growth of psychrotrophic bacteria was greater in vegetables packaged in HOTR film while growth of yeasts and molds was not affected by either packaging film. Most differences in microbial populations in produce packaged in LOTR and HOTR films were less than 1 log10 CFU/g. Botulinal toxin was not detected in cabbage or lettuce packaged in either film or stored under any test condition.

Foods can become contaminated with pathogenic microorganisms from hands, the cutting board, and knives during preparation in the kitchen. A laboratory model was developed to determine occurrence of cross-contamination and efficacy of decontamination procedures in kitchen food-handling practices. Enterobacter aerogenes B199A, an indicator bacterium with attachment characteristics similar to that of Salmonella spp., was used. Chicken meat with skin inoculated with 10(6) CFU of E. aerogenes B199A/g was cut into small pieces on a sterile cutting board. The extent of cross-contamination occurring from meat to the cutting board and from the cutting board to vegetables (lettuce and cucumbers) subsequently cut on the board was determined. Swab samples from the cutting board, hand washings, and lettuce and cucumber samples revealed that approximately 10(5) CFU of E. aerogenes/cm2 were transferred to the board and hands and approximately 10(3) to 10(4) CFU of E. aerogenes/g to the lettuce and cucumbers. The surfaces of the cutting board and hands were treated with antibacterial agents after cutting the meat, and counts of E. aerogenes on the cutting board and vegetables (lettuce and cucumbers) were determined. Results revealed that use of the disinfectant reduced the population of E. aerogenes to almost nondetectable levels on the cutting boards. The average counts after treatment were < 20 CFU/g of vegetable and ranged from < 20 to 200 CFU per cm2 or g on the cutting board and subsequently on the vegetables. These results indicate that bacteria with attachment characteristics similar to Salmonella spp. can be readily transferred to cutting boards during food preparation and then cross-contaminate fresh vegetables if the boards are not cleaned. Application of a kitchen disinfectant can greatly reduce bacterial contamination on cutting boards.

The effect of temperature (4 to 42 degrees C), NaCl concentration (0.5 to 7.5%), NaNO2 concentration (0 to 400 micrograms/ml), water activity (aw level of 0.6 to 0.995), pH (3.5 to 7.3) and urea (8 mM) on the survival and growth of Helicobacter pylori in a nutrient-rich laboratory culture medium was investigated. Under microaerobic conditions (5% O2, 10% CO2, and 85% N2), the organism grew well in brain heart infusion broth supplemented with 7% horse serum and antibiotics (BHI-HS-TVA) in a temperature range of 30 to 37 degrees C with agitation. H. pylori (initial population of ca. 5 x 10(3) CFU/ml) survived for 14 days at 4 degrees C, for 2 days at 25 degrees C, and for less than 1 day at 40 and 42 degrees C. The optimal NaCl concentration for growth of H. pylori was 0.5 to 1.0%; 2.0% NaCl inhibited growth. Up to 400 micrograms of NaNO2 per ml did not prevent growth. The minimum aw (adjusted with glycerol) and pH (acidified with HCl) for growth of H. pylori was 0.98 and 4.5, respectively. The addition of urea to broth greatly enhanced the growth of H. pylori at both pH 4.5 and 5.5. Although H. pylori did not grow at pH 3.5, the presence of urea in broth enhanced its survival. Considering the apparent fastidious conditions for growth of H. pylori in BHI-HS-TVA broth, H. pylori is unlikely to grow well, if at all, in most foods. The bacterium may, however, survive for extended periods of time in low acid-high moisture environments under refrigerated storage.

Several recent Escherichia coli O157:H7 outbreaks associated with both drinking and recreational water raise concerns about waterborne illness caused by this pathogen. The survival characteristics of a mixture of five nalidixic acid-resistant E. coli O157:H7 strains (10(3) CFU/ml) in filtered and autoclaved municipal water, in reservoir water, and in water from two recreational lakes were determined for a period of 91 days at 8, 15 or 25 degrees C. Greatest survival was in filtered autoclaved municipal water and least in lake water. Regardless of the water source, survival was greatest at 8 degrees C and least at 25 degrees C. E. coli O157:H7 populations decreased by 1 to 2 log10 by 91 days at 8 degrees C, whereas the pathogen was not detectable (> or 3 = log10 decrease) within 49 to 84 days at 25 degrees C in three of the four water sources. SDS-PAGE of surface antigens of surviving cells revealed that there was no major alteration in lipopolysaccharide pattern, but outer membrane protein composition did change. These studies indicate that E. coli O157:H7 is a hardy pathogen that can survive for long periods of time in water, especially at cold temperatures. However, direct viable counts of E. coli O157:H7 determined by acridine orange staining remained essentially the same for 12 weeks at 25 degrees C, whereas viable counts on tryptic soy agar plates decreased to undetectable levels within 12 weeks. Results suggest that E. coli O157:H7 can enter a viable but nonculturable (VBNC) state in water.

Rates of thermal inactivation of five strains of Escherichia coli O157:H7 isolated from ground beef implicated in outbreaks of hemorrhagic colitis and five strains isolated from bovine feces were determined. Ground beef (22% fat, 10 g), inoculated with individual test strains at populations ranging from 6.85 to 7.40 log10 CFU g-1 of beef, was formed into patties (0.3 cm thick and 8.0 cm in diameter) and sealed in polyethylene bags. For each strain and treatment temperature (54.4, 58.9, 62.8, 65.6, or 68.3 degrees C), 6 bags were simultaneously immersed into a recirculating water bath. Viable cells in patties heated for various lengths of time were enumerated by plating diluted samples on sorbitol MacConkey agar supplemented with 4-methylumbelliferyl-beta-D-glucuronide (MSMA) and modified eosin methylene blue (MEMB) agar. Regardless of strain or treatment temperature, higher numbers of E. coli O157:H7 cells were generally recovered on MEMB agar than on MSMA, indicating the inferiority of MSMA as a recovery medium for quantitative determination of E. coli O157:H7 cells in heat-processed ground beef. Significantly (P < or = 0.05) higher D values when enumeration was done using MEMB agar compared with MSMA. Mean D values for combined strain data at 54.4, 58.9, 62.8, and 65.6 degrees C from cultures on MEMB agar were 123.90, 6.47, 0.62, and 0.20 min, respectively, whereas D values of 25.5, 5.21, and 0.18 min were obtained at the same temperatures from cultures on MSMA. Results suggest that cooking ground beef patties to an internal temperature of 68.3 degrees C for 40 s will inactivate at least 99.99% of E. coli O157:H7 cells; z values of 4.0 and 5.1 degrees C were calculated from mean D values obtained from MEMB agar and MSMA, respectively, as recovery media. Differences in D values existed among strains but rates of thermal inactivation do not appear to be correlated with the sources of the isolates.

Refrigerated ready-to-eat foods are becoming increasingly popular but are often vulnerable to contamination and subsequent growth by psychrotrophic foodborne pathogens. Consequently, there is a need for additional methods to assure the safety of these foods. Beef slices prepared from roasted whole sirloin tips were used in the study. Nine plant extracts were evaluated for ability to inhibit the growth of two psychrotrophic pathogens (Aeromonas hydrophila and Listeria monocytogenes) in refrigerated cooked beef. Results indicated that only eugenol (clove extract) and pimento extract significantly inhibited the growth of A. hydrophila and L. monocytogenes. However, L. monocytogenes was not as sensitive as was A. hydrophila to both treatments, especially to pimento extracts. These results suggest that plant extracts might be useful as an antimicrobial in cooked ready-to-eat meat.

In late 1995, fecal coliforms were detected in iced tea obtained from several restaurants in the U.S. On the basis of fecal coliform results, the news media inaccurately and sensationally accused the tea industry of marketing tea containing feces. We analyzed 11 iced-tea samples obtained from fast-food restaurants and 25 dry leaf-tea samples purchased from retail grocers for the presence of coliforms and fecal coliforms. All samples of iced tea contained coliforms and fecal coliforms; most probable numbers of coliforms in iced tea ranged from 210 to > 1,100/ml, whereas those of fecal coliforms were 15 to >1,100/ml. Twenty-three of twenty-five leaf-tea samples contained coliforms and fecal coliforms; ranges for positive samples were 3 to 1,100/g and 3 to 460/g, respectively. Two Klebsiella species and three Enterobacter species were isolated from iced tea. Only Klebsiella pneumoniae (93.8% of isolates) and Enterobacter cloacae (6.2%) were isolated from leaf tea. Escherichia coli was not isolated from any of the iced-tea or leaf-tea samples analyzed. The D 55°c values of two isolates of K. pneumoniae and three isolates of E. cloacae from leaf tea, when heated in steeped tea, ranged from 3.75 to 5.08 min. Initial populations of up to 5.70 log CFU/ml were reduced to <10 CFU/ml within 5 min at 65°C. While 23 of 25 (92%) of the leaf-tea samples analyzed contained fecal coliforms, as defined by standard methodology, there is no evidence that leaf tea represents a health hazard. The expected presence in leaf tea of Klebsiella and Enterobacter species, which test positive for the fecal coliform group, should not automatically be construed as indicators of fecal contamination nor as an imminent threat to human health. The presence of coliforms and fecal coliforms in iced tea indicates post-steeping contamination caused by poor sanitation practices in restaurants at which the iced tea was purchased.

The recovery of heat-injured Listeria monocytogenes Scott A in Fraser broth (FB) supplemented with sodium thioglycolate, sodium pyruvate, L-(+)-cysteine hydrochloride, catalase or Oxyrase? was studied. After 3 h of incubation at 30°C, recovery was enhanced by all oxygen scavengers except sodium pyruvate. Oxyrase? (0.005 U ml -1 ) promoted the highest recovery (34%) compared to recovery in control broth (19%). All oxygen scavengers enhanced the recovery of injured L. monocytogenes in FB within 6 h of incubation. After 6 h at 30°C, 49 and 55% of injured cells underwent resuscitation in FB containing 2.5 mg of sodium pyruvate ml -1 and 400 μg of catalase ml -1 , respectively, compared to 24% resuscitation in FB not supplemented with oxygen scavengers. The percentage recovery was increased as the incubation time was extended to 6 and 24 h. Nearly all injured cells were recovered within 24 h of incubation, regardless of supplementation of FB with oxygen scavengers. Fraser broth containing 2.5 mg of sodium pyruvate ml -1 , 400 μg of catalase ml -1 or 0.01 U of Oxyrase? ml -1 were tested to determine the optimal incubation time and temperature for recovering heat-injured L. monocytogenes . Percentage recovery of injured cells increased with an increase in temperature from 25 to 30°C and from 30 to 35°C. The highest percentage of injured cells recovered was observed in FB containing 400 μg of catalase ml -1 (67%) and 0.01 U of Oxyrase? ml -1 (68%) within 6 h of incubation at 35°C. Catalase (400 μg ml -1 ) and Oxyrase? (0.01 U ml -1 ) in FB resulted in significantly higher recovery of injured cells from heated whole milk; however, recovery of injured cells from heated skim milk was not significantly higher. Enrichment in FB containing catalase or Oxyrase? has potential for recovering heat-injured L. monocytogenes cells within 6 h compared to 24 h required in conventional methods.

The efficacy of warm (20°C) and hot (55°C) acetic, citric and lactic acid sprays on survival of Escherichia coli O157:H7 on raw beef was determined. Fresh, raw beef sirloin tips were sliced into ca. 1-cm slices with a sanitized slicer. Discs (5-cm diameter, ca. 25-g) were then taken from internal areas of each slice and inoculated with a 5-strain mixture of E. coli O157:H7 such that final populations on beef samples were 10 3 or 10 6 CFU/g. After standing for 15 min, each inoculated disc was sprayed with 1 mi of 0, 0.5, 1.0 and 1.5% of each acid at 20 or 55°C using an atomizer. Acid-treated meat samples were allowed to dry for 15 min and held at 5°C for up to 13 days in sterile plastic pouches. Escherichia coli O157:H7 was acid tolerant, and acids did not differ appreciably in their lack of antimicrobial activity on E. coli O157:H7. For example, reductions in populations differed by <0.3 log l0 CFU/g immediately after treatment and < 0.5 log l0 CFU/g after 13 days incubation, compared to untreated Controls. None of the acid treatments appreciably reduced E. coli O157:H7 on beef samples nor were any of the acid treatments judged effective for practical uses.

Nine cooperating laboratories, distributed throughout the United States, determined the interlaboratory reproducibility of a sensitive, selective method for isolation of Campylobacter jejuni and Campylobacter coli from foods, and determined the prevalence and distribution of the organism in retail meats. A double-blind inoculated/recovery experiment demonstrated the ability to detect two cells of C. jejuni and C. coli per g of meat at a rate of 96% among the cooperating laboratories. However, a 7.5% false-positive rate for the presumptive detection of the organism was also reported. Samples of ground beef, beef flank steak, lamb stew meat, broiler chicken, pork sausage (without antimicrobials), and pork chops were selected to assess the presence of campylobacters. Each cooperator purchased five of each of the above samples from the refrigerated case of two retail outlets at quarterly intervals throughout the year. A total of 2,160 retail samples were analyzed for the presence of C. jejuni and C. coli . Results indicated that about 30% of the 360 chickens sampled yielded the organism. Analysis of 1,800 red meat products yielded campylobacters at a rate of about 5.1%. Pork samples yielded C. coli and other meats yielded C. jejuni . Higher numbers of isolations from the red meats were made during June and September (8.6%) as compared with December and March (4.2%). These results provide a baseline, for the prevalence of campylobacters in these selected foods, and also support epidemiologic data associating mishandled foods of animal origin as a potential vehicle in human gastroenteritis.

Bisulfite reacted with aflatoxin B 1 and G 1 resulting in their loss of fluorescence. The reaction was first order with rate depending on bisulfite (or the bisulfite and sulfite) concentration(s). Aflatoxin G 1 reacted more rapidly with bisulfite than did aflatoxin B 1 . In the presence of 0.035 M potassium acid phthalate-NaOH buffer (pH 5.5) plus 1.3% (vol/vol) methanol at 25 C, the reaction rate constant for degradation of aflatoxin G 1 was 2.23 × 10 -2 h - and that for aflatoxin B 1 was 1.87 × 10 -2 h - when 50 ml of reaction mixture contained 1.60 g of K 2 SO 3 . Besides bisulfite concentrations, temperature influenced reaction rates. The Q 10 for the bisulfite-aflatoxin reaction was approximately 2 while activation energies for degrading aflatoxin B 1 and aflatoxin G 1 were 13.1 and 12.6 kcal/mole, respectively. Data suggest that treating foods with 50 to 500 ppm SO 2 probably would not effectively degrade appreciable amounts of aflatoxin. Treating foods with 2000 ppm SO 2 or more and increasing the temperature might reduce aflatoxin to an acceptable level.

The objective of this study was to determine what effect temperature and pH have on the ability of Campylobacter fetus subsp. jejuni to grow and survive. None of three strains of C. fetus subsp. jejuni could grow at 30 C and below or at 47 C and above. The optimum temperature for growth was in the range of 42 to 45 C. Only one of three strains, FRI-CF8, could grow at pH 4.9 and none could grow at pH 4.7. The optimum pH for growth was in the range of 6.5 to 7.5; however, all strains grew well at pH 5.5 to 8.0. Rate of cell death at pH 3.0 to 4.5 was temperature-dependent. At comparable pH, cells of C. fetus subsp. jejuni died most rapidly at 42 C, less rapidly at 25 C and at the slowest rate at 4 C. For example, at pH 4.5, a 3 log 10 decrease of cells occurred within 8 h when incubated at 42 C but took 4 days when incubated at 4 C. At 25 C and pH 4.5, cells were inactivated at an intermediate rate. Rates of thermal inactivation of five strains of C. fetus subsp. jejuni were determined at 48, 50, 53, and 55 C in a skim milk heating menstruum. At 48 C, D-values ranged from 7.2 to 12.8 min while at 55 C they ranged from 0.74 to 1.00 min. The times and temperatures used to pasteurize milk should be sufficient to free milk of even unusually large numbers of viable cells of C. fetus subsp. jejuni.

Mycelia of Aspergillus parasiticus NRRL 2999 degraded aflatoxins B 1 and G 1. Initially 9-day-old mycelia appeared to effectively degrade both aflatoxins; however, later experiments indicated that rates at which 9-day-old mycelia degraded aflatoxins B 1 and G 1 varied even though the mycelia were produced and evaluated under similar conditions. A comparison of the ratio of rates at which mycelia of different ages degraded aflatoxin B 1 and G 1 suggests that more than one mechanism may be involved in degradation of aflatoxin by the mold. Mycelia produced when incubation was quiescent or with agitation degraded aflatoxins B 1 and G 1 . Fragmenting of mycelia greatly increased their ability to degrade aflatoxin, thus suggesting that the degrading factor(s) is/are intracellular constituent(s) of the mycelium.

Citric acid retarded degradation of aflatoxins B 1 and G 1 by bisulfite. Replacement of potassium acid phthalate-NaOH with citric acid-NaOH in the mixture of buffer (50 ml, 0.035 M)-methanol (0.65 ml)-0.8 g of K 2 SO 3 , pH 5.5, at 25 C resulted in a decrease from 9.76 × 10 -3 h - to 2.47 × 10 -3 h - and from 1.19 × 10 -2 h - to 4.32 × 10 -3 h - in rate of degradation of aflatoxin B 1 and G 1 , respectively. Methanol also retarded degradation of aflatoxin by bisulfite. Increasing the methanol concentration from 1.3 to 10.0% (v/v) in 50 ml of 0.035 M KHP-NaOH buffer, pH 5.5, plus 0.40 g of K 2 SO 3 , resulted in a decrease in rate constants from 4.26 × 10 -3 h - to 2.16 × 10 -3 h - for aflatoxin B 1 and from 5.54 × 10 -3 h - to 2.98 × 10 -3 h - for aflatoxin G 1 , Presence of citric acid and various concentrations of methanol also reduced rates at which free bisulfite concentrations changed. From these observations, known effects of methanol and probable effects of citric acid on bisulfite oxidation, we suggest that degradation of aflatoxin by bisulfite is dependent on bisulfite oxidation. 14 C-labelled aflatoxin B 1 was treated with K 2 SO 3 at pH 5.5 and allowed to react for 96 h. Most of the degradation product(s) were in the water soluble phase, indicating that a structural modification of aflatoxin occurred.

Aflatoxin is partially or completely degraded by irradiation, heat, or treatment with strong acids or bases, oxidizing agents or bisulfite. Hydrogen peroxide plus riboflavin denature aflatoxin in milk. Mycelia of Aspergillus parasiticus can degrade aflatoxin, possibly via fungal peroxidase. Such degradation is affected by strain of A. parasiticus , amount of mycelium, temperature, pH and concentration of aflatoxin. Adsorbants, including bentonite and activated charcoal, can physically remove aflatoxin and patulin from liquid foods. Patulin is stable at low pH values but not in the presence of large amounts of vitamin C or bisulfite. Patulin can be degraded by actively fermenting yeasts and rubratoxin can be degraded by the mycelium of Penicillium rubrum .

For over 60 years subspecies of Campylobacter fetus (formerly Vibrio fetus ) have been recognized as agents responsible for a variety of veterinary diseases. Such diseases range from abortion in cattle and sheep to hepatitis in poultry to dysentery in cattle. In rare instances, they have also been known to cause disease in humans. However, within the last 3 years, with the advent of microbiological methods that can selectively isolate campylobacters from human fecal specimens, C. fetus subsp. jejuni has become a disease-agent of serious concern. Clinical laboratories from throughout the world are now reporting that C. fetus subsp. jejuni is one of the most common bacterial causes of acute gastroenteritis in both children and adults. Its frequency of isolation is comparable to and in many studies exceeds that at which Salmonella is isolated from diarrheal stools of hospitalized patients. Although the source of the organism could not be identified for many of these cases, food and water have been implicated as being important vehicles for transmitting campylobacters to susceptible individuals.

Staphylococcus aureus and Salmonella typhimurium were tested for their ability to survive and to multiply in meat salads prepared with different concentrations of mayonnaise and held at 4, 22, and 32 C. When mayonnaise was added to meat salads in amounts recommended by recipes from a reputable cookbook, it inactivated a substantial portion of the initial population of both S. aureus (30-60%) and S. typhimurium (20-25%). Salads that were refrigerated at 4 C for 24 h evidenced very little growth of either organism whether mayonnaise was present or not. Storing salads at 22 or 32 C for 5 h resulted in <1.0 log 10 increase of either organism with the greatest increase occurring in salads containing no mayonnaise. Mayonnaise retarded but did not prevent the growth of S. aureus or S. typhimurium in salads stored at 22 or 32 C for 24 h. Increasing the concentration of mayonnaise in salads increased the degree to which growth of these organisms was delayed. Contrary to popular belief, the presence of mayonnaise in meat salads tends to retard rather than enhance growth of food-borne pathogens. However, addition of mayonnaise should not be considered a substitute for refrigeration for preserving meat salads from the growth of food-borne pathogens.