NS305 Unit 2 Listeria Profile Example

The Organism That Grows in the Cold: A Unit 2 Pathogen Profile of Listeria monocytogenes From Floor Drain to Sandwich Line

[Student Name]

Purdue University Global

NS305: Food Safety

Unit 2 Pathogen Profile

[Instructor Name]

[Date]

The sandwich line described in the final section is composite; the surveillance data, outbreak investigation, burden estimate, review and Food Code provisions cited are real.

Identity

Listeria monocytogenes is a gram-positive, rod-shaped bacterium that lives in soil, water, decaying plants and the intestines of healthy animals. It tolerates salt, survives drying better than many enteric bacteria and, most importantly for food service, multiplies slowly at refrigerator temperatures. Cooking kills it readily. The danger therefore sits in foods that are eaten without further cooking and stored cold for days, where the organism has time to grow while every other control appears to be working (Swaminathan & Gerner-Smidt, 2007).

The organism also persists in places that are hard to clean. Floor drains, the undersides of slicers, cracked cutting boards and the condensation inside walk-in coolers can harbor it for months, and food that touches those surfaces after cooking picks it up again. That combination, cold tolerance plus a home in the processing environment, is why Listeria is a problem of handling after cooking rather than of cooking itself.

Vehicles

The foods linked to listeriosis share three features: they are ready to eat, they are kept refrigerated and they have a long shelf life. Deli meats and hot dogs eaten without reheating, soft cheeses, especially those made from unpasteurized milk, refrigerated smoked seafood and refrigerated pâtés appear repeatedly in outbreak reports (Swaminathan & Gerner-Smidt, 2007). Surveillance in the United States drew particular attention to soft Mexican-style cheese, because pregnancy-associated cases among Hispanic women more than doubled between 2004-2006 and 2007-2009 (Silk et al., 2012).

Produce belongs on the list as well. In 2011, whole cantaloupe from a single Colorado farm caused 147 illnesses in 28 states, and 33 of those patients died; investigators traced contamination to unsanitary conditions in the farm's packing facility (McCollum et al., 2013). The cantaloupe outbreak showed that a food no one thought of as risky could carry the organism if the surfaces it touched after harvest were contaminated.

Two Illnesses Under One Name

Listeria causes two distinct illnesses. The first is a febrile gastroenteritis that follows a large dose, appears within a day or two and usually passes without treatment. Most people who have it never learn its cause. The second is invasive listeriosis, in which the bacteria enter the bloodstream and spread to the brain, the membranes around it or, in pregnancy, the placenta and fetus. Invasive disease can begin weeks after the contaminated meal.

Invasive listeriosis is rare and severe. Surveillance from 2004 to 2009 identified 762 cases in the reporting sites, and 18 percent of all cases were fatal (Silk et al., 2012). Worldwide, listeriosis was estimated to have caused 23,150 illnesses and 5,463 deaths in 2010, with about one fifth of cases perinatal (de Noordhout et al., 2014). By numbers of illness Listeria is a minor pathogen; by deaths per case it is among the most serious.

Who Is at Risk

Three groups carry most of the burden. Adults aged 65 and older had incidence four to five times the overall rate, pregnant women and their newborns accounted for 17 percent of cases, and people with weakened immunity from cancer treatment, transplant drugs or other conditions are at raised risk (Silk et al., 2012). In pregnancy the mother may feel only a mild flu-like illness while the infection causes miscarriage, stillbirth or serious illness in the newborn.

Because the people most harmed by Listeria are concentrated in hospitals, nursing homes and prenatal clinics, a food service that feeds those groups carries a risk far above what its menu alone would suggest.

Why Cases Resist Tracing

Investigators face three obstacles. The first is time: a patient asked about meals eaten four weeks earlier rarely remembers them accurately. The second is dispersion: a contaminated product shipped widely produces scattered single cases across many states rather than a cluster in one town. The third is the patients themselves, who are often too ill, too old or, in perinatal cases, too young to give a history. Molecular subtyping has improved the picture by linking cases that share a strain, which is how the cantaloupe outbreak's five subtypes were tied to one farm (McCollum et al., 2013). Even so, most cases are never connected to a specific food.

Where the Organism Is Weak

Listeria's strengths are narrow, and so are its weaknesses. Ordinary cooking destroys it, which is why deli meats reheated until steaming hot are a standard recommendation for pregnant women and older adults, and why pasteurization removes it from milk before cheese is made. It grows slowly, so time matters as much as temperature: a package held at 41°F for three days carries far less risk than the same package held for three weeks. It also depends on moisture and on surfaces where cleaning is skipped. A profile that lists only the organism's strengths leaves a manager with nothing to do; one that names its weaknesses points directly at the controls. Heat, time limits and cleaning are the three weaknesses a food service can use, and the next section turns each into a written practice.

Three Holds on a Sandwich Line

A composite hospital café that slices deli turkey and ham for sandwiches illustrates how the profile turns into practice. The café serves visitors, staff and, through its grab-and-go case, some patients' family members who are pregnant. Three controls, each drawn from the Food Code, address the organism's three advantages (U.S. Food and Drug Administration [FDA], 2022).

1. Cold holding at 41°F or below. Listeria grows at refrigerator temperatures, but it grows more slowly at 41°F than at 45°F, so the café checks product temperature, not only air temperature, twice a shift.

2. Date marking. Ready-to-eat foods held longer than 24 hours carry a discard date no more than seven days after opening, counting the day of preparation as the first. The seven-day limit caps the time the organism has to multiply.

3. Cleaning the slicer and the cold environment. The slicer is broken down, washed, rinsed and sanitized at least every four hours of continuous use, and the cooler's drain and gaskets are on the weekly cleaning list. These steps target the organism's habit of living on equipment.

Each hold fails if the others fail. A slicer cleaned perfectly still passes on contamination from a package of ham opened twelve days ago, and correctly dated ham still picks up the organism from a slicer that has run all day. The café's training therefore presents the three as one system, and its manager checks all three on the same walk-through.

Limits of This Profile

This profile is drawn from surveillance in high-income countries, where most invasive cases are reported; the global estimate notes that whole regions had no incidence data (de Noordhout et al., 2014). The controls proposed are standard Food Code provisions rather than a tested program for this café. They reduce risk; they cannot eliminate an organism that lives in the environment the café shares with every other kitchen.

References

de Noordhout, C. M., Devleesschauwer, B., Angulo, F. J., Verbeke, G., Haagsma, J., Kirk, M., Havelaar, A., & Speybroeck, N. (2014). The global burden of listeriosis: A systematic review and meta-analysis. The Lancet Infectious Diseases, 14(11), 1073-1082. https://doi.org/10.1016/S1473-3099(14)70870-9

McCollum, J. T., Cronquist, A. B., Silk, B. J., Jackson, K. A., O'Connor, K. A., Cosgrove, S., Gossack, J. P., Parachini, S. S., Jain, N. S., Ettestad, P., Ibraheem, M., Cantu, V., Joshi, M., DuVernoy, T., Fogg, N. W., Gorny, J. R., Mogen, K. M., Spires, C., Teitell, P., . . . Mahon, B. E. (2013). Multistate outbreak of listeriosis associated with cantaloupe. New England Journal of Medicine, 369(10), 944-953. https://doi.org/10.1056/NEJMoa1215837

Silk, B. J., Date, K. A., Jackson, K. A., Pouillot, R., Holt, K. G., Graves, L. M., Ong, K. L., Hurd, S., Meyer, R., Marcus, R., Shiferaw, B., Norton, D. M., Medus, C., Zansky, S. M., Cronquist, A. B., Henao, O. L., Jones, T. F., Vugia, D. J., Farley, M. M., & Mahon, B. E. (2012). Invasive listeriosis in the Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009: Further targeted prevention needed for higher-risk groups. Clinical Infectious Diseases, 54(Suppl. 5), S396-S404. https://doi.org/10.1093/cid/cis268

Swaminathan, B., & Gerner-Smidt, P. (2007). The epidemiology of human listeriosis. Microbes and Infection, 9(10), 1236-1243. https://doi.org/10.1016/j.micinf.2007.05.011

U.S. Food and Drug Administration. (2022). Food Code 2022. U.S. Department of Health and Human Services. https://www.fda.gov/food/fda-food-code/food-code-2022