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PubMed This is a summary of 9 peer-reviewed journal articles Updated
Infectious Disease

How Salmonella Spreads and Infects Your Body

At a Glance

Salmonella is a bacterial infection most commonly spread through contaminated food like poultry and eggs, or by handling pets like reptiles and baby chicks. Once swallowed, the bacteria invade the intestinal lining, triggering inflammation and fluid buildup that causes severe, watery diarrhea.

To understand how Salmonella causes illness, it helps to look at its journey from the environment into your body. This bacteria is highly adapted to hitching rides on common items we interact with every day, particularly food and pets [1].

Back to Home

How It Reaches You: The Main Pathways

While Salmonella is famously associated with food, it can enter your system through several different routes.

The Food Connection

Poultry and eggs are the most frequent sources of infection.

  • The “Inside” Route: In some cases, a hen can pass the bacteria into an egg before the shell even forms. This is called vertical transmission [2]. This is why even a clean-looking, uncracked egg can sometimes carry the bacteria.
  • The “Outside” Route: Bacteria can also get onto the shell from the environment or manure after the egg is laid [3].
  • The Role of Recalls: When a company or the government discovers Salmonella in a batch of food—such as in a recent egg recall—they issue a voluntary recall. This is a proactive safety step to pull potentially contaminated items off grocery shelves before they can make more people sick.

The Pet Connection

You don’t have to eat contaminated food to get Salmonella. Many animals carry the bacteria naturally in their intestines without ever appearing sick [4].

  • Reptiles and Amphibians: Turtles, lizards, and snakes are very common carriers [5]. The bacteria can be on their skin, scales, or in their tanks.
  • Backyard Poultry: Baby chicks and ducklings are also frequent sources of exposure, especially for children [5].

The Biological Pathway

Once Salmonella is swallowed, it travels to your small intestine. To cause an infection, it must attach to your intestinal wall and enter your cells. It does this using a specialized biological tool called a Type III Secretion System (T3SS) [6].

Think of the T3SS as a microscopic delivery mechanism. When the bacteria land on the lining of your gut, they use this system to transfer proteins directly into your intestinal cells [6]. These proteins gently prompt the cell to change its shape and absorb the bacteria inside [7].

Why You Feel Sick

Once the bacteria have entered your cells, your immune system spots the invasion and reacts.

  • Inflammation: Your body sends white blood cells to the area, causing inflammation (swelling and irritation) of the intestinal lining [6].
  • Fluid Secretion: To try and wash away the bacteria, your body begins to pump large amounts of fluid into your intestines [8].
  • The Result: This sudden rush of fluid is what leads to the cramping and watery diarrhea characteristic of the infection [8]. For most healthy people, this “flushing” process eventually clears the bacteria out, allowing the body to heal on its own [9].

Common questions in this guide

How can you get Salmonella from an uncracked egg?
A hen can pass Salmonella bacteria into the egg before the shell is even formed, a process called vertical transmission. This means an egg can look perfectly clean and uncracked on the outside but still carry the bacteria inside.
Can I get Salmonella from my pets?
Yes, many animals carry Salmonella naturally in their intestines without looking sick. Reptiles, amphibians, and backyard poultry like baby chicks are common carriers, and you can get infected by touching them or their living habitats.
Why does Salmonella cause watery diarrhea?
When Salmonella invades your intestinal cells, your immune system reacts by causing inflammation and pumping large amounts of fluid into your gut to wash the bacteria away. This sudden rush of fluid is what causes the watery diarrhea associated with the infection.
What happens when Salmonella enters the digestive system?
Once swallowed, the bacteria attach to the intestinal wall and use a biological mechanism to inject proteins into your cells. These proteins prompt your intestinal cells to absorb the bacteria, allowing them to hide inside and multiply.
Can a Salmonella infection cause temporary food sensitivities?
The severe inflammation and irritation in your intestinal lining caused by the infection can sometimes lead to temporary digestive issues, such as short-term lactose intolerance, while your gut is healing.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.In my case, was the infection more likely caused by contaminated food or environmental exposure?
  2. 2.How does the way Salmonella invades my gut affect which symptoms I am feeling right now?
  3. 3.Is the inflammation in my intestines likely to cause any temporary food sensitivities, like lactose intolerance, after I recover?
  4. 4.If I have pets like reptiles or birds, what specific precautions should I take to prevent me or my family from getting reinfected?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

Related questions

Can You Get Salmonella From Clean, Uncracked Eggs?Can I Catch Salmonella From My Pet Turtle or Chickens?

References

References (9)
  1. 1

    The human health burden of non-typhoidal Salmonella enterica and Vibrio parahaemolyticus foodborne gastroenteritis in Shanghai, east China.

    Chen Y, Liu H, Chen M, et al.

    PloS one 2020; (15(11)):e0242156 doi:10.1371/journal.pone.0242156.

    PMID: 33186379
  2. 2

    Effects of a mannan-rich yeast cell wall-derived preparation on cecal concentrations and tissue prevalence of Salmonella Enteritidis in layer chickens.

    Girgis G, Powell M, Youssef M, et al.

    PloS one 2020; (15(4)):e0232088 doi:10.1371/journal.pone.0232088.

    PMID: 32324793
  3. 3

    The Occurrence of Antimicrobial-Resistant Salmonella enterica in Hatcheries and Dissemination in an Integrated Broiler Chicken Operation in Korea.

    Shang K, Wei B, Cha SY, et al.

    Animals : an open access journal from MDPI 2021; (11(1)) doi:10.3390/ani11010154.

    PMID: 33440890
  4. 4

    Salmonella prevalence and serovar distribution in reptiles: a systematic review and meta-analysis.

    Muslin C, Salas-Brito P, Coello D, et al.

    Gut pathogens 2025; (17(1)):52 doi:10.1186/s13099-025-00699-z.

    PMID: 40635028
  5. 5

    Salmonella spp. in Pet Reptiles in Portugal: Prevalence and Chlorhexidine Gluconate Antimicrobial Efficacy.

    Cota JB, Carvalho AC, Dias I, et al.

    Antibiotics (Basel, Switzerland) 2021; (10(3)) doi:10.3390/antibiotics10030324.

    PMID: 33808891
  6. 6

    Salmonella Typhimurium and inflammation: a pathogen-centric affair.

    Galán JE

    Nature reviews. Microbiology 2021; (19(11)):716-725 doi:10.1038/s41579-021-00561-4.

    PMID: 34012042
  7. 7

    Natural compound sanguinarine chloride targets the type III secretion system of Salmonella enterica Serovar Typhimurium.

    Zhang Y, Liu Y, Wang T, et al.

    Biochemistry and biophysics reports 2018; (14()):149-154 doi:10.1016/j.bbrep.2018.04.011.

    PMID: 29761161
  8. 8

    Ex vivo perfusion of the isolated rat small intestine as a novel model of Salmonella enteritis.

    Boyle EC, Dombrowsky H, Sarau J, et al.

    American journal of physiology. Gastrointestinal and liver physiology 2016; (310(2)):G55-63 doi:10.1152/ajpgi.00444.2014.

    PMID: 26564721
  9. 9

    Non-typhoidal Salmonella infections in children: Review of literature and recommendations for management.

    Wen SC, Best E, Nourse C

    Journal of paediatrics and child health 2017; (53(10)):936-941 doi:10.1111/jpc.13585.

    PMID: 28556448

This page provides educational information on how Salmonella spreads and affects the body. It is not a substitute for professional medical advice, diagnosis, or treatment from your healthcare provider.

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