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What’s listeria? A microbiologist explains the bacterium behind deadly food poisoning outbreak

Bacteria do, and can, result in food. Everyone eats intentionally or unintentionally millions to billions of live microbes each day.

The majority are completely harmless, however, many could cause serious illnesses in humans. Due to these potential pathogens, there exists a long set of foods in order to avoid, including uncooked eggs, raw fish and unwashed fruit and veggies, particularly for women that are pregnant. The foods themselves aren’t bad, however the same can’t be said for several bacterial passengers, such as for example Listeria monocytogenes, or listeria for short.

This specific pathogen has found methods to indiscriminately enter our foods. While deli and dairy foods like cold cuts, cheese, milk and eggs are generally culprits for causing listeriosis the overall name for listeria-caused infections more fresh vegetables and fruits are also implicated.

All of the foods in charge of U.S. listeria outbreaks previously decade shows precisely how easily these bacteria bypass. Listeria has resulted in in hard-boiled eggs, enoki mushrooms, cooked chicken and, in 2021, packaged saladtwice.

Even the frozen aisle isn’t spared from listeria contamination. Contaminated ice cream in Florida was behind this year’s listeria outbreak, with 25 reported cases spanning 11 states since January 2021, in accordance with an early on August 2022 report from the Centers for Disease Control and Prevention. Those that fell ill ranged in age from significantly less than 1 to 92 yrs . old, and 24 of the cases have involved hospitalizations.

How do this type of tiny organism bypass extensive disinfection efforts and wreak such havoc? As a microbiologist who has been dealing with listeria and attempting to solve these mysteries, Let me share some close-guarded strategies concerning this unique little pathogen and its own strategies of survival outside and inside our anatomies.

Farm to table

To avoid consumer contact with listeria, the meals industries follow stringent disinfection and surveillance guidelines from the meals and Drug Administration and the U.S. Department of Agriculture. Any detection of listeria triggers a recall of potentially contaminated foods.

Since 2017, there were over 270 listeria-related food recalls. They are incredibly costly and will sometimes result in fears in consumers and also nationwide disruptions in food services. However, the recalls represent mostly of the tools that the meals industry must protect consumers from foodborne infections.

Not absolutely all listeria strains are manufactured equal. Genetic variations in listeria create a huge difference in if the pathogen eventually ends up being involved with multistate outbreaks or just hitching a ride harmlessly through our digestive system. Essentially, in line with the different methods used, listeria could be subtyped into different lineages, with some connected with outbreaks more often than others.

Researchers are investigating methods to tell these listeria strains apart, distinguishing the less harmful ones from the ones that are particularly dangerous, or hypervirulent. Having the ability to accurately identify them might help policymakers assess risks and make economically feasible decisions to boost food safety.

Listeria can be an intracellular pathogen. In the body, it could grow in the cell and spread to neighboring cells.

Listeria is tough

Listeria can reside in anyplace where food is grown, packaged, stored, transported, prepared or served. Our research team has even found listeria in organic lettuce harvested from the backyard garden.

Listeria may survive and grow in temperatures as cold as 24 degrees Fahrenheit (-4.4 Celsius) since it has adapted to winter and developed tricks for overcoming cold stress. Taking into consideration the average refrigerator maintains a temperature selection of 35 F to 38 F (1.7 C to 3.3 C), even though the meals is stored properly at refrigeration temperatures, a harmless few listeria can grow to dangerous degrees of contamination as time passes.

Listeria can be versatile in adapting to and surviving all sorts of disinfection processes. When it grows on surfaces, listeria protects itself with a biofilm structure, some sort of coating that forms a physical and chemical barrier and prevents disinfectants from achieving the bacteria within.

Surviving the harsh conditions outside the body is only the initial area of the story. Before even starting to cause infections, listeria must reach the intestines without getting caught and destroyed by your body’s defenses.

Traveling and surviving passage by way of a human digestive system isn’t easy for bacteria. Saliva enzymes can degrade bacterial cell walls. So can stomach acids and bile salts. Antibodies inside our digestive system can recognize and target bacteria for degradation. Moreover, resident gut microbes are strong competitors for the limited quantity of space and nutrients inside our intestines.

After digestion, your body’s intestinal movement sends traffic a proven way out from the body. To be able to hang in there and cause infections, bacteria need to attach themselves and hold on against the bowel motion while competing for nutrients. Successful pathogens can establish these survival and attachment tasks while undermining our immune defenses.

Listeria that have the ability to hang in there inside our intestines can trigger an immune response. In healthy people, that may manifest as minor diarrhea or vomiting that goes away completely without medical assistance.

However, people that have compromised immune systems or immune systems temporarily weakened due to medication or pregnancy could be more vunerable to severe infections. In the lack of an effective disease fighting capability, listeria can invade other tissues and organs by creating a competent niche for growth.

Listeria in stealth mode

Listeria is what we microbiologists call an intracellular pathogen. Within an infected individual, listeria can grow in the cell and spread to neighboring cells. Hiding within our cells in this manner, listeria avoids detection by antibodies or other immune defenses that can detect and destroy threats which exist beyond our cells.

Once in stealth mode, listeria can transfer to and infect different organs. Wherever it goes, inflammation follows because the body’s disease fighting capability tries to follow the bacteria. The inflammation eventually results in collateral damage in nearby tissues.

Actually, deaths from listeria infections tend to be linked to the more invasive types of the disease where the microbes have breached the intestinal barriers and moved to other areas of the body. Life-threatening illnesses that may derive from listeria include meningitis inflammation round the brain and spinal-cord that may occur when these microbes infect the mind or endocarditis, infection of the heart’s inner lining. And in pregnant individuals, if the pathogen reaches the placenta, it could spread to the fetus and cause stillbirth or miscarriage.

Therefore, invasive listeria cases frequently have an alarmingly high hospitalization rate greater than 90% and a fatality rate that may reach 30%.

The scary statistics argue for a proactive and effective infection control to safeguard vulnerable populations, such as for example elderly or pregnant individuals, from listeria exposure.

Think, cook and eat

When you have risk factors and desire to take extra precautions, maybe turn that unpasteurized cider right into a hot, mulled cider to kill the bacteria with boiling and simmering. Eat soft cheeses on foods that get cooked, such as for example pizzas or grilled sandwiches, rather than eating them cold, straight from the refrigerator. Essentially, use heat to create out the delicious flavors and eliminate potential listeria contamination in your meal.

Ultimately, it’s extremely difficult to call home in a totally sterile environment, consuming food without all living microorganisms. So enjoy your favorites, but stay up-to-date with ongoing recalls and follow the expiration guidelines, specifically for ready-to-eat food.

Yvonne Sun, Assistant Professor of Microbiology, University of Dayton

This short article is republished from The Conversation under an innovative Commons license. Browse the initial article.

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