Pathogens

  • Hand dryers might be better for the environment; worse for limiting disease spread

    Posted: January 9th, 2012 - 11:53am by Ben Chapman

    starbucks.jpg
    Author: 
    Ben Chapman

    I like to write at Starbucks. There's something about the background activity and lattes, mixed with Neil Young on my iPod, that helps me focus. I hit up a somewhat new outlet in Raleigh today and needed a restroom break. After washing my hands I looked around the bathroom for paper towels and all I could find was an air dryer (right, exactly as shown). I wanted paper towels, because using them matters; drying friction helps remove pathogens.

    I don't like blow dryers because the literature shows they accumulate microorganisms from toilet aerosols, and can cause contamination of hands as they are dried by the dryer (Coates et al., 1987; Knights, et al., 1993; Redway,et al., 1994). In 2010, Anna Snelling and colleagues at the University of Bradford (UK) also showed that drying with a blow dryer can recontaminate hands and rubbing with paper towel was the most effective method to reduce pathogens.

    Handwashing and food service food safety guru Pete Snyder at the St. Paul-based Hospitality Institute of Technology and Management summarized key aspects of handwashing and drying . Pete says that after hands are washed and rinsed, they must be thoroughly dried and cites data that shows 1-2 log reduction of pathogens from drying. Water and soap loosen the attachment of pathogen to hands. A rinse step dilutes what has been loosened but drying (and the friction associated) is the next step that matters - and the bugs have to go somewhere; I'd rather that be a paper towel instead of being blown all over my pants.

    Pete also notes that it is also apparent that many individuals do not dry their hands thoroughly when using a blow dryer; hence, moisture, which is conducive to microbial growth, remains on hands, or people dry their hands on their clothing.

    Starbucks, proper handwashing requires guest access to the proper tools – and that means vigorously running water, soap and paper towel.

    Coates, D., D. N. Hutchinson, and F. J. Bolton. 1987. Survival of thermophilic campylobacter on fingertips and their elimination by washing and disinfection. Epidem. Inf. 99:265-274.

    Knights, B., C. Evans, S. Barrass, and B. McHardy. 1993. Hand drying - A survey of efficiency and hygiene. The Applied Ecology Research Group, University of Westminster. London, UK.

    Redway, K., B. Knights, Z. Bozoky, A. Theobald, and S.Hardcastle. 1994. Hand drying: A study of bacterial types associated with different hand drying methods and with hot air dryers. Applied Ecology Research Group, University of Westminster. London, UK. 14. Brodie, J. 1965. Hand hygiene. Scot. Med. J. 10:1:115-125.
     

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  • Iguana for you? The biological risks of eating reptiles

    Posted: February 9th, 2010 - 9:48pm by Doug Powell

    A study published last year in the International Journal of Food Microbiology shows that people can catch certain diseases (trichinosis, pentastomiasis, gnathostomiasis and sparganosis) by eating the meat of reptiles such as crocodiles, turtles, lizards or snakes (or iguanas, right).

    Simone Magnino, lead author of the study and a researcher for the World Health Organization (WHO), told the Spanish Foundation for Science and Technology that,

    "The clearest microbiological risk comes from the possible presence of pathogenic bacteria, especially Salmonella, and also Shigella, Escherichia coli, Yersinia enterolitica, Campylobacter, Clostridium and Staphylococcus aureus, which can cause illnesses of varying degrees of severity."

    This expert says the data about risks to public health are still inconclusive, since there is no comparative information about consuming this meat and the prevalence of pathogens. Also, there are few published research articles about cases of illness associated with consuming reptile meat.

    The experts advise people to freeze the meat, just as they would with other foods from animal sources, since this deactivates parasites. Industrial processing and proper cooking (not leaving the meat raw) can also kill off pathogens.


    Citation: Simone Magnino, Pierre Colin, Eduardo Dei-Cas, Mogens Madsen, Jim McLauchlin, Karsten Nöckler, Miguel Prieto Maradona, Eirini Tsigarida, Emmanuel Vanopdenbosch and Carlos Van Peteghem. "Biological risks associated with consumption of reptile products." International Journal of Food Microbiology 134 (2009) 163, September 2009.
     

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  • New Zealand fruit and vegetable safety - good, but we'll make sure we do better

    Posted: December 20th, 2009 - 8:06pm by Doug Powell

    Every time there is a food safety outbreak with fresh fruits and vegetables, some journalist or lobby group will call up and say something like, “we want to do some sampling for E. coli or Salmonella and fresh produce.”

    And every time, Chapman or I will walk the person through the limitations with testing, especially in fresh produce.

    New studies by the New Zealand Food Safety Authority (NZFSA) highlight the limitations. In one, two out of 900 samples tested positive for Salmonella in lettuce, both from lettuces from the same grower.

    In a related study, none of the chemical residues detected were of health concern, although NZFSA principal advisor for chemicals Dr Paul Dansted says he is disappointed with results from this year’s Food Residue Surveillance Programme (FRSP), which targets food likely to show up problems. This year’s focus was on spinach, celery, ginger and garlic.

    “A significant number of samples had levels over the maximum residue limit (MRL) which is used for monitoring purposes, but it’s important to stress that dietary intake assessments on the non-compliant food showed none posed a health or food safety concern.”

    Eight out of 27 celery samples and four out of 24 spinach samples had residues that were over the limit. There were none over the limit in 50 samples of garlic, but ginger had 11 samples out of 39 over the limit.

    “Celery and spinach can be more vulnerable to persistence of chemical residues,” Dr Dansted says. “Because of their shape, residues that wash off in the rain can collect in the base of the plant. We expected to find some problems, but this is not good enough. We will take regulatory action to ensure better compliance in future.”

    Properly structured sampling programs are essential to validate that food safety programs are working. But testing is not enough.
     

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  • UK petting zoo E. coli O157 outbreak: 36 confirmed sick; 12 in hospital all under age of 10; four in serious condition; this won't turn out well

    Posted: September 13th, 2009 - 11:22am by Doug Powell

    It’s like people in the U.K. had never heard of E. coli O157. Despite outbreak after outbreak – often involving children at nurseries -- public inquiries and a single food safety agency, the Brits just seem oblivious when it comes to dangerous pathogens that send kids to the hospital.

    This morning, the     London Times reported that

    “Thousands of children across the South of England may be at risk from the E. coli bug in what looks to be the largest UK outbreak linked to transmission from farm animals."

    Godstone Farm in Surrey, a popular family attraction where children are encouraged to stroke and touch animals, is closed while the Health Protection Agency (HPA) conducts tests to find out the cause of the outbreak which has left 12 children in hospital, four of them in a serious condition.

    About 1,000 children, mainly from South London, Surrey, Kent and Sussex, visit the farm every day during the school holidays and at weekends. It is feared that 30,000 children could be at risk of infection.

    It has emerged health officials knew about the outbreak among people who visited the farm days before it was closed to the public.

    The Health Protection Agency became aware of the outbreak in late August after cases were traced to the farm.

    One parent has expressed her anger, saying the decision for the farm to remain open was an "absolute disgrace".

    But farm manager Richard Oatway said the farm had acted responsibly and was co-operating with the investigation.

    Richard, please share with us your knowledge of natural reservoirs of E. coli O157, and the steps you’ve taken to control such dangerous pathogens from infecting children who visit your farm. Handwashing isn’t enough.
     

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  • Fit, food and fresh produce

    Posted: August 21st, 2009 - 2:29pm by Doug Powell

    Food is 21st century snake oil. In an era of unprecedented affluence, consumers now choose among a cacophony of low fat, enhanced nutrient staples reflecting a range of political statements and perceived lifestyle preferences, far beyond dolphin free tuna.

    On May 17, 2001, Procter & Gamble announced that it was discontinuing its Fit Fruit & Vegetable Wash in the United States, Canada and Mexico effective September 28, 2001. The company said the market was too small for continued investment.

    But FIT is still out there. And someone e-mailed me about it the other day.

    I’m not up on the current version of Fit being marketed, but in fall 2000, I contacted P&G to ask for the data substantiating the claim that Fit would eliminate 99.9 per cent of bacteria on fresh produce,

    After a bunch of calls to various PR types I got hooked up with some scientists at P&G in Cincinnati, who verbally told me that sample cucumbers, tomatoes and the like were grown on the same farm in California, sprayed with chemicals that would be used in conventional production, and then harvested immediately and washed with Fit or water. The Fit removed 99.9 per cent more, or so the company claimed, because no data was ever forthcoming.

    One problem. Many of the chemicals used have harvest after dates, such as the one tomato chemical that must be applied at least 20 days before harvest. Residue data on produce in Canadian stores reveals extremely low levels, in the parts per million or billion. So that 99.9% reduction is really buying consumers an extra couple of zeros in the residue quantity, all well below health limits.

    No idea what the new Fit is promoting. But pathogens and chemicals in fresh produce need to be controlled on the farm, and in transportation and distribution. 
     

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  • Top 10 reasons telling people to 'just cook it' sucks as a food safety strategy

    Posted: August 5th, 2009 - 3:20pm by Doug Powell

    About 18 months after the 1993 Jack-in-the-Box E. coli O157:H7 outbreak, I, the erstwhile graduate student, gave a talk to a bunch of food safety types from government and industry. I showed a clip from ABC’s 20/20 television program about a family fighting for regulatory change, and many in the audience laughed at the family when their kitchen was shown. Audience members commented that the consumers were sloppy in their cooking and of course they got sick, and if only they would cook hamburger properly E. coli O157:H7 wouldn’t happen.

    I thought the response of the audience was sort of appalling.

    In mid-1994, Michael Taylor was appointed chief of USDA's Food Safety and Inspection Service.  On Sept. 29, 1994, USDA said it would now regard E. coli O157:H7 in raw ground beef as an “adulterant,” a substance that should not be present in the product. By mid-October, 1994, Taylor announced plans to launch a nationwide sampling of ground beef to assess how much E. coli O157:H7 was in the marketplace. The 5,000 samples would be taken during the year from supermarkets and meat processing plants “to set an example and stimulate companies to put in preventive measures.” Positive samples would prompt product recalls of the entire affected lot, effectively removing it from any possibility of sale.

    That's the long-winded version for what a USDA official said in a 1994 television interview: we'll stop blaming consumers  when they get sick from the food and water they consume.

    But the just-cook-it crowd persisted. And still does today.

    A couple of weeks ago, while announcing a ground beef recall in Colorado, the U.S. Department of Agriculture’s Food Safety Inspection Service stated in a release,

    FSIS would like to remind consumers of the importance of following food safety guidelines when handling and preparing raw meat. Ground beef should be cooked to a safe minimum internal temperature of 160° Fahrenheit.

    I would like to remind FSIS that it ain’t so easy to handle contaminated ground beef and not spread it around a home or food service kitchen.

    Jim Marsden, a former vp at the American Meat Institute and now a professor at Kansas State University, wrote in his meatingplace.com blog last week, the top-10 reasons “just cook it” does not, and will not, work.

    1. E. coli O157:H7 is a unique pathogen. The levels of this organism necessary to cause infection are very low.

    2. The severity of the disease E. coli O157:H7 can cause, especially in children is devastating.

    3. In many cases, parents order hamburgers for their children and rely on restaurants to cook them properly.  In restaurants, parents really have no control over whether the hamburgers they order are sufficiently cooked to eliminate possible contamination from E. coli O157:H7.

    4. If consumers unknowingly bring this pathogen into their kitchens, it is almost impossible to avoid cross contamination. Even the smallest amount of contamination on a food that is not cooked can cause illness. Many of the reported cases of E. coli O157:H7 have involved ground beef that was clearly cooked at times and temperatures sufficient to inactivate E. coli O157:H7.  Some other vector, i.e. cross contamination was probably involved.

    5. Even if consumers attempt to use thermometers to measure cooking temperature, it is difficult to properly measure the internal temperature of hamburger patties. They would have to use an accurate thermometer and place the probe exactly into the center of the patty. In addition, the inactivation of E. coli O157:H7 is dependent on cooking time and temperature. For example, if they cook to 155 degrees F, they should hold that temperature for 16 seconds. It is not realistic to expect that consumers, many of which are children will scientifically measure the internal temperature of hamburgers.

    6. The way ground beef is packaged, it is virtually impossible to remove it from packages or chubs and make patties without spreading contamination if it is present.

    7. Sometimes ground beef appears to be cooked when it really isn’t. There is a phenomenon called “premature browning” that can make ground beef appear to be fully cooked when in fact it is undercooked.

    8. E. coli O157:H7 may be present in beef products other than ground beef. For example, in non-intact beef products, including tenderized steaks that are not always cooked to temperatures required for inactivation.

    9. There have been many cases and outbreaks of E. coli O157:H7 associated with foods that are not cooked (i.e. fresh cut produce).

    10. As Senator Patrick Leahy said after the 1993 Jack-in-the-Box outbreak – “The death penalty is too strong a punishment for undercooking a hamburger”.  He was right –consumers will make mistakes. There needs to be a margin of safety so that undercooking does not result in disease or death.

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  • Eating beach sand can be messy - at both ends

    Posted: July 20th, 2009 - 2:09pm by Doug Powell

    When it gets hot in Kansas, we go to Florida.

    We're leaving in a week, with a little work along the way before we settle into our rental on sexy Venice Beach, Florida. It’s the antithesis of places like South Beach, Miami, where celebrities flock and appearances rule. Venice – founded as a retirement community by the Brotherhood of Locomotive Engineers in the 1920s – is about as quiet as it gets.

    With good beaches.

    This year we’ll have 7-month-old Sorenne, and she’s starting to crawl (see below). If she can do this on hardwood, sand will be a breeze.

    So we have to aware of sand in the mouth.

    Besides the yuck factor, researchers at the University of North Carolina have found that digging in sand on beaches near water with high levels of fecal bacteria could be a risk factor for developing the drips.

    For the study, reported in The American Journal of Epidemiology, researchers got contact information for more than 25,000 people visiting seven beaches within seven miles of sewage treatment plants.

    About 10 days later, the researchers called and asked how they had spent their day at the beach and whether they had experienced problems like vomiting or diarrhea since then.

    Those who dug in the sand, the study found, were significantly more likely to report having been sick — with those who had allowed themselves to be buried in the sand most affected. Children seemed to be at extra risk.

    The best advice: wash your damn hands, especially before eating.

    This isn’t the first time sand has been implicated in human illness.

    In May, 2008, children's playgrounds on Sydney's northern beaches were closed after a rare form of salmonella normally linked to tropical fish made dozens of toddlers seriously ill.
     

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  • Pathogens in produce: a brief review

    Posted: May 28th, 2008 - 8:48pm by Doug Powell

    Following this morning's report of a new European study demonstrating the potential for internalization of Salmonella in produce, Ben Chapman pulled together the following notes on the topic.

    Irrigation water containing raw sewage or improperly treated effluents from sewage treatment plants may contain hepatitis A, Norwalk viruses, or enteroviruses in addition to bacterial pathogens such as E.coli O157:H7, Salmonella spp. and Shigella spp. (Beuchat, 1998).

    Produce can also be contaminated with pathogens due to internalization of pathogens both through the root system and flesh or stem scars. Evidence of infiltration of bacteria into vegetables is reported in several articles (Bartz 1982; Bartz and Showalter 1981; Burnett et al., 2000; Seo and Frank 1999; Zhuang et al., 1995). Clear evidence exists to conclude that pathogens can be incorporated into fresh produce. So far, this evidence is based on laboratory experiments, not actual real world situations. Past research suggests that pathogens can enter lettuce plants through its roots and end up in the edible leaves. Small gaps in growing roots through which plant pathogens infect tissue may also allow E. coli entry (Solomon et al, 2002b; Warriner et al., 2003a, Warriner et al., 2003b).

    The uptake of Salmonella spp. by roots of hydroponically grown tomato plants has been shown. Within one day of exposure to a high concentration mixture of Salmonella spp. pathogen cells were found in the hypocotyls, cotyledons, stems and leaves of young plants; though whether fruit is affected is not known at this time (Guo et al., 2002).

    Solomon and colleagues (2002a) discovered that the transmission of E.coli O157:H7 to lettuce was possible through both spray and drip irrigation. They also found that the pathogen persisted on the plants for 20 days following application and submerging the lettuce in a solution of 200ppm chlorine did not eliminate all viable E.coli O157:H7 cells. This suggests that irrigation water of unknown microbial quality should be avoided in lettuce production (Solomon et al., 2002a).  In a follow-up experiment, Solomon and colleagues (2002b) explored the transmission of E. coli O157:H7 from manure-contaminated soil and irrigation water to lettuce plants. The researchers recovered viable cells from the inner tissues of the lettuce plants and found that the cells migrated to internal locations in plant tissue and were thus protected from the action of sanitizing agents These experiments demonstrated that E. coli O157:H7 can enter the lettuce plant through the root system and migrate throughout the edible portion of the plant (Solomon et al., 2002b).

    The risk of contamination of produce due to Salmonella spp. was found to be increased when soil and water were present, and that soil and water actually act as reservoirs of the pathogen. Xuan and colleagues (2002) found that soil and water were factors in the infiltration of salmonella into the tissues of tomato. This supports the theory that preharvest contact with contaminated soil or water increased the contamination potential by certain pathogens and can lead to problems in pathogen removal and the efficacy of sanitizers.

    Flesh scarring can provide a suitable environment for pathogen growth, and decreases the value of employing sanitizers, either in the packing shed or by consumers (Xuan et al., 2002).

    The uptake of Salmonella spp. by roots of hydroponically grown tomato plants has also been shown. Within one day of exposure to a high concentration mixture of Salmonella spp. pathogen cells were found in the hypocotyls, cotyledons, stems and leaves of young plants; though whether fruit is affected is not known at this time (Guo et al., 2002).

    In a 2006 review, Vectors and conditions for preharvest contamination of fruits and vegetables with  pathogens capable of causing enteric diseases,  Larry Beuchat of the Center for Food Safety and Department of Food Science and Technology at the University of Georgia, concluded:

    "Manure, manure compost, sewage, sludge, irrigation water, and runoff water represent
    avenues for introduction of pathogenic bacteria, parasites, and viruses to soil in which
    fruits and vegetables intended to be eaten raw are grown. Pathogens vary in their
    ability to survive in soil amendments and in soil. Inactivation rates and persistence in
    soil are also influenced by soil type, rainfall, temperature, and agronomic practices.
    Some pathogens can survive in soil for periods of time exceeding those needed to grow
    plants from seeds or seedlings to the point of harvest. Pathogens originating from
    preharvest environments may contaminate the surface of produce and evidence is
    mounting that contamination of internal tissues can also occur. Prevention of
    preharvest contamination of fruits and vegetables is an essential part of a systems
    approach focused on applying interventions designed to achieve delivery of
    microbiologically safe produce to the consumer."

    References

    Bartz, J.A. 1982. Infiltration of tomatoes immersed at different temperatures to different depths in suspensions of Erwinia carotovora subsp. carotovora. Plant Disease. 66:302-305.

    Bartz, J.A., and R.K. Showalter. 1981. Infiltration of tomatoes by aqueous bacterial suspensions. Phytopathology. 71: 515-518.

    Beuchat, 2006. Vectors and conditions for preharvest contamination of fruits and vegetables with  pathogens capable of causing enteric diseases. British Food Journal 108 (1): 38-53.

    Beuchat, L.R. 1998. Surface decontamination of fruits and vegetables eaten raw: a review. WHO/FSF/FOS/Publication 98.2. World Health Organization. Geneva. 49pp.

    Burnett, S.L., Chen. J. and Beuchat, L.R. 2000. Attachment of Escherichia coli O157:H7 to the surfaces and internal structures of apples as detected by confocal scanning laser microscopy. Applied and Environmental Microbiology. 66: 4679-4687.

    Guo, X., van Iersel, M. W., Chen, J., Brackett, R. E. and Beuchat, L. R. 2002. Evidence of association of salmonellae with tomato plants grown hydroponically in inoculated nutrient solution. Applied  Environmental Microbiology. 68: 3639-3643.

    Hedberg, C.W., Angulo, F.J., White, K.E., Langkop, C.W., Schell, W.L., Stobierski M.G., Schuchat, A., Besser, J.M., Dietrich, S., Helsel, L., Griffin, P.M., McFarland J.W. and Osterholm M.T. 1999. Outbreaks of salmonellosis associated with eating uncooked tomatoes: implications for public health. Epidemiology and Infection 122: 385-93.

    Seo, K. H., and J. F. Frank. 1999. Attachment of Escherichia coli O157:H7 to lettuce leaf surface and bacterial viability in response to chlorine treatment as demonstrated by using confocal scanning laser microscopy. Journal of Food Protection.  62: 3-9.

    Solomon, E. B., Yaron, S., and Matthews, K.R. 2002b. Transmission of Escherichia coli O157:H7 from contaminated manure and irrigation water to lettuce plant tissue and its subsequent internalization. Applied Environmental Microbiology. 68: 397-400.

    Solomon, E.B., ,Potenski, C.J. and Matthews, K.R. 2002a. Effect of irrigation method on transmission to and persistence of Escherichia coli O157:H7 on lettuce. Journal of Food Protection. 65: 673–676.

    Warriner K., Ibrahim F., Dickinson M,. Wright C. and Waites W.M. 2003a. Internalization of human pathogens within growing salad vegetables. Biotechnology & Genetic Engineering Reviews.  20: 117-134.

    Warriner K., Ibrahim F., Dickinson M,. Wright C. and Waites W.M. 2003b. Interaction of Escherichia coli with growing salad spinach plants. Journal of Food Protection. 66: 1790-1797.

    Xuan, G., Jinru, C., Brackett, R.E., Beuchat, L.R. 2002. Survival of salmonella on tomatoes stored at high relative humidity, in soil, and on tomatoes in contact with soil. Journal of Food Protection. 65: 274-279.

    Zhuang, R.-Y., Beuchat, L.R. and Angulo. F.J. 1995. Fate of Salmonella montevideo on and in raw tomatoes as affected by temperature and treatment with chlorine. Applied Environmental Microbiolology. 61: 2127-2131.
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