TeachableMedicalNews article 01212020

Teachable moment in classrooms:

  1. cellular basis of life chapter – function of lysosomes
  2. digestive system chapter – HCl in gastric juice kill bacteria
  3. immune system chapter – cytotoxic T cells destroy infected cells
  4. immune system chapter – antibody production by plasma cells
  5. microbiology; human pathogenic bacteria

 The news item:  Hospitalization of over 100 people from Salmonella infection was in the news recently. The outbreak in the article started from handling contaminated pig ears sold as dog treat:

Salmonella outbreak tied to pig-ear dog treats appears over after sickening 154 people

Food safety regulators drop warnings against the dog treats, save for the recalled products, after four-year outbreak ends

The article mentions the symptoms of Salmonella infection, and the best defense against contracting it is washing hands frequently.

So, Why Do I Care??  Salmonella bacterium is frequent contamination of uncooked food items; Salmonella outbreaks sicken over a million people each year in the US, causes over 400 deaths, and costs hundreds of millions of dollars in direct medical cost.

Plain English, Please!!! First, let’s talk about the Salmonella bacterium. Salmonella is a type of bacterium that lives in the cells of large intestines of people and many animals. This location is the reason why Salmonella infections spread mostly through contamination of food by fecal material, or through human fecal material from unwashed hands.  Salmonella carefully avoids from entering the lysosome of the host cells, so the lysosomes cannot rid the cells of the invaders; they are kept from invading the rest of our body by our immune system.

Second, let’s talk about the normal destruction of Salmonella. Some Salmonella bacteria survive the deadly acidic stomach juice, and arrive into the large intestine.  Salmonella bacterium in the large intestine are constantly being destroyed by cytotoxic T lymphocytes (T cells) that crawl to the site of infection, identify the infected intestinal cells, and kill the cells.  If the bacteria get into our blood stream, then antibodies from plasma cells of our immune system will destroy the bacteria. The results of all this is that the Salmonella bacterium maintain low numbers in the intestine, but doesn’t cause symptoms of the disease, salmonellosis.

Third, let’s talk about the reason Salmonella causes deaths.  So, if our immune system is so great in keeping Salmonella at bay, why would anybody get hurt by this bacterium?  The strength of our personal immune system varies greatly between individuals. Just like other physiological measures, such as our height, weight, or the color of our eyes.  Some of us have slowly acting cytotoxic T cells, and few antibodies; those individuals may not be able contain newly consumed Salmonella. Young children and the elderly have weakened immune systems. Common cancer treatments, such as chemotherapy and radiation, also weakens the immune system.  Organ transplant recipients take drugs that weaken their immune system.  All those individuals are at risk of letting Salmonella spread throughout the body, causing the intestinal symptoms, and even death.

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