Monthly Archives: April 2014

56 students sick; shouldn’t they be better at food safety? Salmonella outbreak strikes University of Queensland college

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Expect this story to disappear after today. There is no follow-up in Australia. The reporting, three weeks after it happened, is lightening fast in Australian terms.

vomit.clownA Salmonella outbreak at a university college ended in several students being hospitalised earlier this month.

Students at the University of Queensland’s Cromwell College began showing signs of sickness on the night of April 6 and four students were admitted to the Royal Brisbane and Women’s Hospital later that week.

Fifty-six students displayed symptoms and 17 tested positive for Salmonella.

Samantha Cridland, 17, was one of four students admitted to the hospital on April 10.

She said her first thoughts were that another case of gastroenteritis might be floating around the college.

“I started feeling unwell at the start of the week, and everyone had similar symptoms of vomiting, diarrhoea, stomach aches and fevers,” she said.

“I thought it was a gastro bug and I went to the UQ health centre and got tested there.

“I found out later it was definitely Salmonella.”

A Queensland Health spokesperson said the department was investigating the source of the outbreak.

Salmonella internalization in mung bean sprouts and pre- and postharvest intervention methods in a hydroponic system

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Mung bean sprouts, typically consumed raw or minimally cooked, are often contaminated with pathogens. Internalized pathogens pose a high risk because conventional sanitization methods are ineffective for their inactivation. The studies were performed (i) to understand the potential of internalization of Salmonella in mung bean sprouts under conditions where the irrigation water was contaminated and (ii) to determine if pre- and postharvest intervention methods are effective in inactivating the internalized pathogen. Mung bean sprouts were grown hydroponically and Bean_sproutsexposed to green fluorescence protein–tagged Salmonella Typhimurium through maturity. One experimental set received contaminated water daily, while other sets received contaminated water on a single day at different times. For preharvest intervention, irrigation water was exposed to UV, and for postharvest intervention–contaminated sprouts were subjected to a chlorine wash and UV light. Harvested samples were disinfected with ethanol and AgNO3 to differentiate surface-associate pathogens from the internalized ones. The internalized Salmonella Typhimurium in each set was quantified using the plate count method. Internalized Salmonella Typhimurium was detected at levels of 2.0 to 5.1 log CFU/g under all conditions. Continuous exposure to contaminated water during the entire period generated significantly higher levels of Salmonella Typhimurium internalization than sets receiving contaminated water for only a single day (P < 0.05). Preintervention methods lowered the level of internalized Salmonella by 1.84 log CFU/g (P < 0.05), whereas postintervention methods were ineffective in eliminating internalized pathogens. Preintervention did not completely inactivate bacteria in sprouts and demonstrated that the remaining Salmonella Typhimurium in water became more resistant to UV. Because postharvest intervention methods are ineffective, proper procedures for maintaining clean irrigation water must be followed throughout production in a hydroponic system.

Journal of Food Protection®, Number 5, May 2014, pp. 696-863 , pp. 752-757(6)

Ge, Chongtao1; Rymut, Susan1; Lee, Cheonghoon2; Lee, Jiyoung3

Listeria monocytogenes transfer during mechanical dicing of celery and growth during subsequent storage

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The transfer of Listeria monocytogenes to previously uncontaminated product during mechanical dicing of celery and its growth during storage at various temperatures were evaluated. In each of three trials, 275 g of retail celery stalks was immersed in an aqueous five-strain L. monocytogenes cocktail to obtain an average of 5.6 log CFU/g and then was diced using a celery.fresh.cuthand-operated dicer, followed by sequential dicing of 15 identical 250-g batches of uninoculated celery using the same dicer. Each batch of diced celery was examined for numbers of Listeria initially and after 3 and 7 days of storage at 4, 7, and 10°C. Additionally, the percentage by weight of inoculated product transferred to each of 15 batches of uninoculated celery was determined using inoculated red stems of Swiss chard as a surrogate. Listeria transfer to diced celery was also assessed after removing the Swiss chard. L. monocytogenes transferred from the initial batch of inoculated celery to all 15 batches of uninoculated celery during dicing, with populations decreasing from 5.2 to 2.0 log CFU/g on the day of processing. At 10°C, Listeria reached an average population of 3.4 log CFU/g in all batches of uninoculated celery. Fewer batches of celery showed significant growth during storage at 4 and 7°C (P < 0.05). Swiss chard pieces were recovered from all 15 batches of celery, with similar amounts seen in batches 2 to 15 (P > 0.05). L. monocytogenes was also recovered from each batch of uninoculated celery after the removal of Swiss chard, with populations decreasing from 4.7 to 1.7 log CFU/g. Storing the diced celery at 10°C yielded a L. monocytogenes generation time of 0.87 days, with no significant growth observed during storage at 4 or 7°C. Consequently, mitigation strategies during dicing and proper refrigeration are essential to minimizing potential health risks associated with diced celery.

Journal of Food Protection®, Number 5, May 2014, pp. 696-863 , pp. 765-771(7)

Kaminski, Chelsea N.1; Davidson, Gordon R.2; Ryser, Elliot T.3

Efforts to zap bacteria in food are slow to catch hold

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The nuclear energy that Frank Benso uses to kill bacteria in fruit and oysters has won widespread support from public health officials and scientists, who say it could turn the tide against the plague of foodborne illness.

0408_bananafood_mainThe Food and Drug Administration has approved the use of radiation to wipe out pathogens in dozens of food products, and for decades it has been used in other developed countries without reports of human harm.

But it has barely caught on in the United States. The technology — called irradiation — zaps bacteria out of food and is highly effective, but for many consumers it conjures up frightening images of mutant life forms and phosphorescent food.

Benso, who opened Gateway America 18 months ago, also knows his new venture pits him against the nation’s growing buy-local, back-to-nature movement that shuns industrial food processing.

“Those naysayers better throw out their microwaves, because that is irradiation,” Benso said, standing in his 50,000-square-foot irradiation facility.

Dozens of scientific studies have shown that irradiated food is safe for human consumption, and that no radioactive material has leaked outside any U.S. plant, according to the U.S. Nuclear Regulatory Commission. The three forms of energy that can be used — gamma rays, electron beams and X-rays — can virtually eliminate bacteria in minutes. All this has prompted the World Health Organization, the American Medical Association, the U.S. Centers for Disease Control and Prevention, and dozens of other groups to endorse its use.

Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, blames an “anti-science movement” for the public resistance. He is frustrated with the federal government for endorsing irradiation but then not educating the public as it has with childhood immunizations and water fluoridation.

Study: hand hygiene ‘too complex’ for Australian doctors

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Doctors at most public hospitals are failing to follow national hand hygiene guidelines, a new study shows.

This is because the current five-step approach is too complex, says Professor Mary-Louise McLaws, an infectious diseases expert at the University of New South Wales.

handwash_south_park(2) handwash_south_park(2)Her study focused on how regularly health workers wash their hands before seeing a patient, which is the first hand-hygiene opportunity in the five-step plan adopted in Australia in 2009.

The approach should be simplified to focus on washing hands before and after seeing each patient, says Prof McLaws, who has published a report in the Medical Journal of Australia.

Human instinct will take care of other protocols, such as washing after coming into contact with bodily fluids.

“We need to simplify it. Five behaviour changes were thrown at the doctors and nurses all at once.

“The nurses got it. They are exemplary compared with doctors. But they work in teams and support each other.”

Effects of in-plant interventions on reduction of enterohemorrhagic Escherichia coli and background indicator microorganisms on veal calf hides

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Enterohemorrhagic Escherichia coli (EHEC) serotypes in veal have recently been recognized as a problem. Because hides are considered to be the principal source of EHEC and hide interventions have been shown to be very efficacious in the control of EHEC in beef processing plants, various hide-directed intervention strategies have been implemented in several veal processing plants to mitigate contamination. We evaluated the effectiveness of three different hide interventions used at veal processing vealplants: A, a water rinse followed by a manual curry comb of the hide; B, application of 200 ppm of chlorine followed by a hot water rinse; and C, a 5-min treatment with chlorine foam followed by a rinse with 180 to 200 ppm of acidified sodium chlorite. The levels of total aerobic bacteria, Enterobacteriaceae, coliforms, and E. coli, as well as the prevalence of Salmonella, E. coli O157:H7, and non-O157 EHEC, were determined on hides pre- and postintervention. Interventions A, B, and C reduced indicator organisms (P < 0.05) by 0.8 to 3.5 log CFU, 2.1 to 2.7 log CFU, and 1.0 to 1.5 log CFU, respectively. No Salmonella was detected on hides prior to intervention. E. coli O157:H7 prevalence was observed at only one plant, so comparison was not possible. Other non-O157 EHECs (O26, O103, and O111) were observed for all interventions studied. Interventions A and B reduced culture-confirmed non-O157 EHEC by 29 and 21 % , respectively, whereas intervention C did not reduce non-O157 EHEC. Our results show that the most effective veal hide intervention for reducing indicator organisms and EHECs was the application of 200 ppm of chlorine followed by hot water rinse. These data provide options that veal processors can consider in their EHEC control program.

Journal of Food Protection®, Number 5, May 2014, pp. 696-863 , pp. 745-751(7)

Wang, Rong1; Koohmaraie, Mohammad2; Luedtke, Brandon E.3; Wheeler, Tommy L.3; Bosilevac, Joseph M.3

Fecal shedding of non-O157 serogroups of shiga toxin–producing Escherichia coli in feedlot cattle vaccinated with an Escherichia coli O157:H7 SRP vaccine or fed a lactobacillus-based direct-fed microbial

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The objectives of this study were to determine whether fecal shedding of non-O157 Shiga toxin–producing Escherichia coli (STEC) in feedlot cattle was affected by the use of an E. coli O157:H7 vaccine or a direct-fed microbial (DFM) and whether the shedding of a particular non-O157 STEC serogroup within feces was associated with shedding of O157 or other non-O157 STEC serogroups. A total of 17,148 cattle in 40 pens were cow.poop.spinachrandomized to receive one, both, or neither (control) of the two interventions: a vaccine based on the siderophore receptor and porin proteins (E. coli SRP vaccine, two doses) and a DFM product (low-dose Bovamine). Fresh fecal samples (30 samples per pen) were collected weekly from pen floors for four consecutive weeks beginning approximately 56 days after study allocation. DNA extracted from enriched samples was tested for STEC O157 and non-O157 serogroups O26, O45, O103, O111, O121, and O145 and for four major virulence genes (stx 1, stx 2, eae, and ehxA) using an 11-gene multiplex PCR assay. Generalized linear mixed models were used to analyze the effects of treatments and make within-sample comparisons of the presence of O-serogroup–specific genes. Results of cumulative prevalence measures indicated that O157 (14.6%), O26 (10.5%), and O103 (10.3%) were the most prevalent STEC O serogroups. However, the vaccine, DFM, or both had no significant effect (P > 0.05) on fecal prevalence of the six non-O157 STEC serogroups in feedlot cattle. Within-sample comparisons of the presence of STEC serogroup–specific genes indicated that fecal shedding of E. coli O157 in cattle was associated with an increased probability (P < 0.05) of fecal shedding of STEC O26, O45, O103, and O121. Our study revealed that neither the E. coli O157:H7 vaccine, which reduced STEC O157 fecal shedding, nor the DFM significantly affected fecal shedding of non-O157 STEC serogroups, despite the fact that the most prevalent non-O157 STEC serogroups tended to occur concurrently with O157 STEC strains within fecal samples.

Journal of Food Protection®, Number 5, May 2014, pp. 696-863 , pp. 732-737(6)

Cernicchiaro, N.1; Renter, D. G.2; Cull, C. A.1; Paddock, Z. D.1; Shi, X.1; Nagaraja, T. G.1

Why I don’t eat fresh cilantro and parsley: prevalence and diversity of enterotoxigenic Escherichia coli strains in fresh produce

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Analysis of fresh produce showed that enterotoxigenic Escherichia coli (ETEC) strains are most often found in cilantro and parsley, with prevalence rates of approximately 0.3%. Some ETEC strains also carried Shiga cilantro.slugs.powell.10toxigenic E. coli (STEC) genes but had no STEC adherence factors, which are essential to cause severe human illness. Most ETEC strains in produce carried stable toxin and/or labile toxin genes but belonged to unremarkable serotypes that have not been reported to have caused human illnesses.

Journal of Food Protection®, Number 5, May 2014, pp. 696-863 , pp. 820-823(4)

Feng, Peter C. H.; Reddy, Shanker P.

Dubai has an egg problem

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Dubai apparently has an egg problem too, as authorities are urging residents to take extra precautions when ordering high-risk food from restaurants, especially the many egg-based dishes that are not fully cooked.

Raw_eggSultan Al Tahir, head of food inspection section, emphasized that eggs should be stored in refrigerators all along the food chain from the farm until they are cooked.

“In the kitchen, eggs should be broken carefully in a segregated area to prevent contamination of other ready to eat food. Egg products should be cooked well to a minimum temperature of 75 degrees Celsius as per our regulations. Eggs that are stored at ambient temperatures should not be consumed and our inspectors have been instructed to discard eggs that have not been stored or cooked properly,” he said.

Responding to bioterror concerns by increasing milk pasteurization temperature would increase estimated annual deaths from listeriosis

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In a 2005 analysis of a potential bioterror attack on the food supply involving a botulinum toxin release into the milk supply, the authors recommended adopting a toxin inactivation step during milk processing. In response, some dairy processors increased the times and temperatures of pasteurization well above the legal minimum for high temperature, short time pasteurization (72°C for 15 s), with unknown implications for public health.

listeriaThe present study was conducted to determine whether an increase in high temperature, short time pasteurization temperature would affect the growth of Listeria monocytogenes, a potentially lethal foodborne pathogen normally eliminated with proper pasteurization but of concern when milk is contaminated postpasteurization. L. monocytogenes growth during refrigerated storage was higher in milk pasteurized at 82°C than in milk pasteurized at 72°C. Specifically, the time lag before exponential growth was decreased and the maximum population density was increased. The public health impact of this change in pasteurization was evaluated using a quantitative microbial risk assessment of deaths from listeriosis attributable to consumption of pasteurized fluid milk that was contaminated postprocessing. Conservative estimates of the effect of pasteurizing all fluid milk at 82°C rather than 72°C are that annual listeriosis deaths from consumption of this milk would increase from 18 to 670, a 38-fold increase (8.7- to 96-fold increase, 5th and 95th percentiles). These results exemplify a situation in which response to a rare bioterror threat may have the unintended consequence of putting the public at increased risk of a known, yet severe harm and illustrate the need for a paradigm shift toward multioutcome risk benefit analyses when proposing changes to established food safety practices.

Journal of Food Protection®, Number 5, May 2014, pp. 696-863 , pp. 696-712(17)

Stasiewicz, Matthew J.1; Martin, Nicole2; Laue, Shelley2; Gröhn, Yrjo T.3; Boor, Kathryn J.2; Wiedmann, Martin2