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How Salmonella Bacteria Outsmarts the Human Immune System

Posted in Our Blog on February 26, 2025

Salmonella bacteria are a single-cell organism. You wouldn’t expect something without a brain or central nervous system to outsmart the far superior human body with its specialized immune system.

But…

It does.

Scientists uncovered how this tricky little germ has evolved to evade the human immune system by altering the gut and making itself at home. A little redecorating, ordering some takeout, and nestling in to reproduce.

Well, sort of.

How do Salmonella bacteria achieve this?

Follow along to find out.

Reason for New Salmonella Bacteria Research

A recent study from UC Davis Health called, Salmonella virulence factors induce amino acid malabsorption in the ileum to promote ecosystem invasion of the large intestine was published in the Proceedings of the National Academy of Sciences.

“We knew that Salmonella invades the small intestine, although it is not its primary site of replication. The colon is,” said the lead author of the study Andreas Bäumler, who is a distinguished professor and vice chair of research in the Department of Medical Microbiology and Immunology at UC Davis.

This study explains how this bad bug tricks the gut environment to be more hospitable to its own needs and help it escape the body’s natural defenses to allow it to make its way to the colon.

Short-Chain Fatty Acids Defend Intruders

Your gut is a proverbial war zone. Filled with trillions of bacteria, both good and bad, a battle wages one.

Beneficial bacteria produce short-chain fatty acids to help combat harmful germs. It is these short-chain fatty acids that act like the boots on the ground.

But somehow, Salmonella bacteria manage to grow and spread in the gut.

How?

It’s All About Balance

A careful balance is necessary to keep all of our body systems in line. The best way to shake things up is to disrupt that balance.

And that is exactly what the Salmonella bacteria have been able to do.

These bacteria have found a way to change the gut’s nutrition balance.

It causes inflammation in the gut lining, which in turn affects the normal absorption of amino acids from food. This nutrient imbalance is used to the bacteria’s advantage.

“Our findings show that Salmonella has a clever way of changing the gut’s nutrient environment to its advantage. By making it harder for the body to absorb amino acids in the ileum, Salmonella creates a more favorable environment for itself in the large intestine,” says Bäumler.

But how does these bacteria achieve that lofty goal?

Making Itself at Home

Salmonella bacteria create inflammation in the small intestine. Apparently, in addition to the goal of potentially entering the bloodstream, this helps to impact the absorption of amino acids into the blood.

In fact, two amino acids (lysine and ornithine) were more abundant in the gut following Salmonella bacterial infection. Instead of being absorbed by the body, it was available for the Salmonella bacteria’s use, thus allowing it to survive.

The bacteria also used this as an opportunity to balance the pH to its preferences. A move that allows the pathogen to bypass the growth-inhibiting effects of the short-chain fatty acids.

A Bit About Salmonella?

Salmonella is the bacteria responsible for the illness salmonellosis. The Center for Disease Control and Prevention (CDC) estimates that Salmonella bacteria are responsible for about 1.35 million infections in the United States each year. These lead to around 26,500 hospitalizations and 420 deaths.

Food is the primary source of these illnesses.

Salmonella Symptoms

Salmonella infection symptoms can begin anywhere from six hours to six days after exposure.

Most people experience diarrhea, fever, and stomach cramps that last about a week (four to seven days).

Higher Risk Groups

Certain groups of people have conditions or susceptibilities that make them more likely to become sick if exposed, and experience more severe symptoms if infected.

Those more vulnerable to Salmonella infection include:

  • Children under 5 years of age
  • Infants (children under 12 months of age) that are not breast fed
  • People taking certain medications such as stomach acid reducers

Those more likely to experience sever symptoms include:

  • Infants
  • Older adults (65 years and older)
  • People with a weakened immune system

While most people do not need medical intervention and are not prescribed antibiotic treatment, those in the higher risk group are more likely to receive treatment.

In some cases, complications may arise from infection.

Salmonella Complications

Most of the time Salmonella bacteria are limited to the intestinal tract. However, in some cases, the bacteria can breach the intestinal wall and enter the bloodstream capillaries and veins found there. When this happens, bacteria may infect the urinary tract, blood, bones, joints, and even the nervous system.

Common Salmonella complications include reactive arthritis, irritable bowel syndrome, and bacteremia that can affect other parts of the body.

Reactive Arthritis

Reactive arthritis, a condition affecting the collagen in the joints, eyes, and urethra, is a common complication. This type of infection causes joint pain, irritation of the eyes, and pain during urination. Reactive arthritis symptoms may last for months or even years in some people.

Irritable Bowel Syndrome

Irritable bowel syndrome is another common complication of Salmonella illness. In some cases, it can take quite some time before bowel habits return to normal.

Bacteremia

Bacteremia associated with Salmonella infections can affect many different tissues in the body. Resulting in a variety of infections.

Potential bacteremia infections include:

  • Urinary tract infection – infection of the urinary system
  • Meningitis – infection of the tissue surrounding the brain and spinal cord
  • Endocarditis – infection of the lining of the heart or valves
  • Osteomyelitis – infection of the bones or bone marrow

Where Does the Research Go from Here?

This research not only answers some questions, but poses others. It revealed ways that the gut environment changes during infections. Which could lead to new discoveries for inflammatory bowel disorders like Crohn’s disease and ulcerative colitis.

“This research uses a more holistic approach to studying gut health. It not only gives us a better understanding of how Salmonella works, but also highlights the importance of maintaining a healthy gut microbiota,” said Lauren Radlinski, the study’s first author and postdoctoral fellow in the Bäumler Lab. “Our findings could lead to new treatments that help support the microbiota during infection.”

This study highlighted ways that the pathogen uses to defend against the host. Alternatively, this inside information could be used to reverse that activity. Probiotics or certain dietary changes may boost the body’s natural defense.

“By learning how a pathogen manipulates the host’s system, we can uncover ways to boost the host’s natural defenses,” says Radlinski.

Have You Fallen Sick from a Salmonella Outbreak?

If you have been impacted by a Salmonella outbreak and wish to make a legal claim, The Lange Law Firm, PLLC has a Salmonella lawyer that can help.

The Lange Law Firm, PLLC has successfully represented cases just like yours and won millions of dollars in food poisoning and products liabilities lawsuits.

Reach out by calling (833) 330-3663 or send us an email for a free, no obligation consultation to go over the details of your situation with you.

Don’t wait. Call today to get the justice you deserve.

By: Heather Van Tassell (contributing writer, non-lawyer)