Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 18 peer-reviewed journal articles Updated
Infectious Disease

How Shigella Affects Your Body and How It’s Diagnosed

At a Glance

Shigella is a bacterial infection that invades the intestinal lining, causing severe symptoms like bloody diarrhea and cramping. An accurate diagnosis requires a stool culture with antimicrobial susceptibility testing to ensure you receive the right antibiotics for your specific infection.

Understanding how Shigella interacts with your body can help make sense of the intense symptoms you are experiencing. This infection is not just “bad food poisoning”; it is a sophisticated biological process where bacteria actively invade and damage your intestinal lining.

The Biological Invasion

The reason shigellosis causes such severe pain and bloody stool is due to the way the bacteria attack your epithelium (the layer of cells lining your intestines).

  1. Injection: Shigella uses a specialized structure called a Type III Secretion System (T3SS)—often described as a molecular syringe—to inject toxic proteins directly into your intestinal cells [1][2].
  2. Entry and Hijacking: These proteins force your cells to “swallow” the bacteria. Once inside, Shigella escapes into the cell’s fluid and hijacks your cell’s internal machinery to move around [3].
  3. Cell-to-Cell Spread: The bacteria can actually propel themselves from one cell into the next without ever leaving the safety of the cell environment, effectively “tunneling” through your tissue [4].
  4. Inflammation and Fenestration: This process causes massive inflammation and fenestration (the creation of tiny holes or window-like openings) in your intestinal lining [4]. This leads to the leakage of blood and mucus into your stool, a condition known as dysentery [5].

The Progression of Symptoms

Symptoms typically follow a predictable timeline, though individual experiences may vary:

  • Incubation Period: After swallowing the bacteria, there is a quiet period of 1 to 2 days before you feel sick [6].
  • Early Phase: The illness often begins with high fever, abdominal cramps, and watery diarrhea [5]. In young children, high fevers can sometimes trigger seizures, which require immediate medical attention [7].
  • Dysentery Phase: In many cases, the diarrhea progresses to dysentery. This is characterized by frequent, small-volume stools that contain visible blood and mucus [8]. You may also experience tenesmus, a painful and constant feeling that you need to pass stool even when your bowels are empty [5].
  • Recovery: For most healthy adults and children, symptoms resolve within 5 to 7 days, though the bacteria can remain in your system and be spread to others for several weeks if not treated [9][10].

Navigating Your Diagnosis

Getting an accurate diagnosis is critical, as several conditions can mimic shigellosis, including Salmonella, E. coli O157:H7, viruses like Norovirus, or a sudden flare-up of Inflammatory Bowel Disease (IBD) like Ulcerative Colitis [11].

PCR vs. Stool Culture

Modern labs often use two different types of tests:

  • Multiplex GI PCR Panels: These are rapid molecular tests that look for the DNA of Shigella and other pathogens. They are highly sensitive and can provide results in hours [12][13]. However, PCR cannot tell you which antibiotics will kill the bacteria [14].
  • Stool Culture: This is the traditional method where the lab tries to grow the bacteria in a dish. While it takes longer (2–3 days), it is absolutely necessary for Antimicrobial Susceptibility Testing (AST) [15]. The AST tells your doctor exactly which drugs the bacteria are resistant to, ensuring you receive the correct treatment [14][16].

Lab Report Completeness Checklist

When you receive your lab results, ensure they contain the following components to guarantee your care team has all the necessary information:

  1. Pathogen Identification: Does it explicitly name the species (e.g., Shigella sonnei)? [17]
  2. Detection Method: Was it found via PCR, culture, or both? [18]
  3. Antimicrobial Susceptibility Testing (AST): Does the report list specific antibiotics and whether the bacteria are “Sensitive” (S), “Intermediate” (I), or “Resistant” ® to them? [15]
  4. Resistance Markers: (Optional) Does the report mention specific resistance genes? [18]

Common questions in this guide

Why does a Shigella infection cause bloody diarrhea?
Shigella bacteria use specialized proteins to invade and tunnel through the cells lining your intestines. This causes massive inflammation and creates tiny holes in the tissue, allowing blood and mucus to leak into your stool, a condition known as dysentery.
How long does it take to feel sick after being exposed to Shigella?
After swallowing the bacteria, there is typically a quiet incubation period of 1 to 2 days before you start feeling sick. The illness usually begins with a high fever, stomach cramps, and watery diarrhea before progressing to more severe symptoms.
What is the difference between a PCR test and a stool culture for Shigella?
A PCR panel is a rapid test that detects the bacteria's DNA in hours, but it cannot tell you which antibiotics will work. A stool culture takes 2 to 3 days to grow the bacteria, which is absolutely necessary to test which specific antibiotics can successfully treat your infection.
What is the constant urge to go to the bathroom even when empty?
Tenesmus is a constant, painful sensation that you need to have a bowel movement, even when your bladder and bowels are completely empty. It is a very common symptom during the dysentery phase of shigellosis.
What information should my Shigella lab report include?
Make sure your lab report specifically identifies the bacteria strain and includes Antimicrobial Susceptibility Testing (AST). The AST tells your doctor exactly which antibiotics are sensitive or resistant to your infection, ensuring you get the right treatment.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my lab report include a full antimicrobial susceptibility test (AST) or just a PCR detection?
  2. 2.Since PCR panels can detect multiple pathogens, are there any other viruses or bacteria I should be concerned about?
  3. 3.Based on my stool culture, which specific antibiotic will work best against the strain I have?
  4. 4.Is my current abdominal pain 'tenesmus,' and how long should I expect this sensation to last?
  5. 5.Given my symptoms, how can we differentiate this from other conditions like Norovirus, Salmonellosis, or an inflammatory bowel disease flare?

Questions For You

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

References

References (18)
  1. 1

    The type III secretion system apparatus determines the intracellular niche of bacterial pathogens.

    Du J, Reeves AZ, Klein JA, et al.

    Proceedings of the National Academy of Sciences of the United States of America 2016; (113(17)):4794-9 doi:10.1073/pnas.1520699113.

    PMID: 27078095
  2. 2

    The Shigella Type III Secretion System: An Overview from Top to Bottom.

    Muthuramalingam M, Whittier SK, Picking WL, Picking WD

    Microorganisms 2021; (9(2)) doi:10.3390/microorganisms9020451.

    PMID: 33671545
  3. 3

    Integrative structural analysis of the type III secretion system needle complex from Shigella flexneri.

    Flacht L, Lunelli M, Kaszuba K, et al.

    Protein science : a publication of the Protein Society 2023; (32(4)):e4595 doi:10.1002/pro.4595.

    PMID: 36790757
  4. 4

    Mechanisms of bacillary dysentery: lessons learnt from infant rabbits.

    Yum LK, Agaisse H

    Gut microbes 2020; (11(3)):597-602 doi:10.1080/19490976.2019.1667726.

    PMID: 31570038
  5. 5

    How Do the Virulence Factors of Shigella Work Together to Cause Disease?

    Mattock E, Blocker AJ

    Frontiers in cellular and infection microbiology 2017; (7()):64 doi:10.3389/fcimb.2017.00064.

    PMID: 28393050
  6. 6

    Shigellosis.

    Hendrick J, Raqib R, Noor Z, et al.

    Lancet (London, England) 2025; (406(10511)):1508-1519 doi:10.1016/S0140-6736(25)01033-5.

    PMID: 40915309
  7. 7

    Hemolytic Uremic Syndrome With Severe Neurologic Complications in an Adult.

    Nasir A, Patel N, Prabakaran S, et al.

    Federal practitioner : for the health care professionals of the VA, DoD, and PHS 2019; (36(Suppl 4)):S36-S41.

    PMID: 31296982
  8. 8

    A Review on the Antibiotic Resistance of Shigella Strains in Iran.

    Shooraj M, Taheri M, Karimi-Yazdi M

    Infectious disorders drug targets 2024; (24(1)):e110823219657 doi:10.2174/1871526523666230811093114.

    PMID: 37723953
  9. 9

    Macrophages orchestrate elimination of Shigella from the intestinal epithelial cell niche via TLR-induced IL-12 and IFN-γ.

    Eislmayr KD, Langner C, Liu FL, et al.

    bioRxiv : the preprint server for biology 2025; doi:10.1101/2025.01.20.633976.

    PMID: 39896533
  10. 10

    Bacteriophage Therapy Against Shigella spp.: A Precision Antimicrobial Strategy.

    Scarlata GGM, Belančić A, Štimac D, et al.

    Antibiotics (Basel, Switzerland) 2026; (15(3)) doi:10.3390/antibiotics15030317.

    PMID: 41892478
  11. 11

    Bacterial dysentery complicated with Crohn's disease: A case report.

    Wang X, Ming W, Chen H, et al.

    Medicine 2025; (104(33)):e43984 doi:10.1097/MD.0000000000043984.

    PMID: 40826702
  12. 12

    Comparative evaluation of BD MAX™ Enteric Panels and Luminex NxTAG® GPP for the detection of gastrointestinal pathogens in clinical stool samples.

    Guillem J, Albert E, Giménez E, et al.

    Diagnostic microbiology and infectious disease 2026; (114(4)):117267 doi:10.1016/j.diagmicrobio.2026.117267.

    PMID: 41544457
  13. 13

    Point-of-care multiplex-PCR enables germ identification in haemolytic uremic syndrome 94 h earlier than stool culture.

    Llano López LH, Melonari P, Gehring S, et al.

    European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology 2021; (40(3)):643-645 doi:10.1007/s10096-020-04060-x.

    PMID: 33011905
  14. 14

    The role of gastrointestinal PCR in inflammatory bowel disease flares: A double-edged sword or a diagnostic breakthrough?

    Goyal MK, Berinstein E, Dutta P, et al.

    Indian journal of gastroenterology : official journal of the Indian Society of Gastroenterology 2026; (45(1)):5-14 doi:10.1007/s12664-025-01811-6.

    PMID: 40691419
  15. 15

    Trends in shigellosis notifications in England, January 2016 to March 2023.

    Charles H, Sinka K, Simms I, et al.

    Epidemiology and infection 2024; (152()):e115 doi:10.1017/S0950268824001006.

    PMID: 39363593
  16. 16

    "Molecular Characterization of Extended Spectrum Beta-Lactamase Resistance in Pediatric Shigella Isolates in Egypt".

    Badr DF, Zaki MES, Elsayed AG, et al.

    Biochemical genetics 2025; (63(5)):4651-4664 doi:10.1007/s10528-024-10943-x.

    PMID: 39485669
  17. 17

    In-Depth Genome-Based Analysis of Shigella spp. and Escherichia spp.: Resolving Ambiguities and Unveiling Phylogenetic Relationships.

    Dif G, Djemouai N, Bouras N, Zitouni A

    Current microbiology 2025; (82(4)):170 doi:10.1007/s00284-025-04158-5.

    PMID: 40045049
  18. 18

    Culture-positive shigellosis cases are epidemiologically different to culture-negative/PCR-positive cases.

    Quinn E, Najjar Z, Huhtinen E, et al.

    Australian and New Zealand journal of public health 2019; (43(1)):41-45 doi:10.1111/1753-6405.12844.

    PMID: 30516310

This page explains how Shigella affects the body and is diagnosed for educational purposes only. Always consult your healthcare provider to interpret your specific stool test results and determine the appropriate medical treatment.

Get notified when new evidence is published on Shigellosis.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.