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PubMed This is a summary of 11 peer-reviewed journal articles Updated

Testing and Diagnosis: How Doctors Identify Salmonella

At a Glance

Salmonella is primarily diagnosed using a stool test, such as a rapid PCR test or a traditional stool culture. While PCR tests provide quick results, a stool culture allows doctors to determine which specific antibiotics will effectively treat the bacterial infection.

If you have symptoms like severe diarrhea or fever after a potential exposure, your doctor will use laboratory tests to confirm if Salmonella is the cause. These tests help determine the exact type of bacteria and whether the infection is localized in your gut or has spread elsewhere [1].

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Stool Tests: The Primary Tool

Most diagnoses are made by testing a stool sample. There are two main ways labs look for the bacteria:

Rapid PCR (Molecular) Testing

Many clinics now use Culture-Independent Diagnostic Tests (CIDTs), such as PCR.

  • How it works: This test looks for the genetic “fingerprints” (DNA) of the bacteria [2].
  • The benefit: It is very fast, often providing results within hours rather than days [3].
  • The limitation: While it tells you if the bacteria are present, it cannot tell if the bacteria are alive or which specific antibiotics will be most effective against them [2].

Stool Culture

This is the traditional “gold standard” for diagnosis.

  • How it works: The lab attempts to grow (culture) the live bacteria from your sample over 2 to 3 days [4].
  • The benefit: Once the bacteria are grown, the lab can perform antimicrobial susceptibility testing. This determines exactly which antibiotics will kill that specific strain—information that is vital if your case is severe [5][6].

When is a Blood Culture Necessary?

For most healthy people, Salmonella stays in the intestines. However, if your doctor suspects the bacteria have entered your bloodstream (a condition called bacteremia), they will order a blood culture [7]. This is typically reserved for:

  • Patients with a very high, persistent fever [8].
  • Infants, the elderly, or those with weakened immune systems [9].
  • Cases where symptoms are severe and not improving with standard hydration [10].

Understanding Your Lab Report

When you receive your results, you may see several different terms:

  • Detected / Positive: This means the test found evidence of Salmonella in your system [2].
  • Serotype: This is the specific “name” of the strain (for example, Salmonella Enteritidis). Public health officials use this name to link different cases to the same food source or outbreak [4].
  • Susceptibility (S, I, R): If a culture was performed, the report will list antibiotics as Susceptible (the drug should work), Intermediate, or Resistant (the drug will not work) [6].

A Note on Typhoid vs. Non-Typhoidal

Your doctor is likely testing for non-typhoidal Salmonella (NTS), which causes common food poisoning [8]. If you have recently traveled to certain parts of the world, they may also screen for Typhoidal Salmonella (S. Typhi). Unlike the common “stomach flu” version, typhoidal strains cause a severe, whole-body illness called Typhoid Fever and are much more likely to show up in a blood culture than a stool test [8][11].

Common questions in this guide

How do doctors test for a Salmonella infection?
Doctors usually test for Salmonella by analyzing a stool sample. They may run a rapid PCR test to quickly find the bacteria's genetic material, or a stool culture to grow the bacteria and see which antibiotics will work best.
What is the difference between a rapid PCR test and a stool culture?
A PCR test rapidly detects the DNA of the bacteria, often providing results within hours. In contrast, a stool culture takes a few days to grow live bacteria but allows the lab to determine which antibiotics will effectively kill that specific strain.
Why would my doctor order a blood culture for Salmonella?
While Salmonella usually stays in your intestines, it can sometimes spread to your bloodstream. Your doctor will likely order a blood culture if you have a high, persistent fever, a weakened immune system, or severe symptoms that aren't improving with standard hydration.
What does the 'serotype' mean on my Salmonella lab report?
A serotype is the specific name of the Salmonella strain causing your infection, such as Salmonella Enteritidis. Public health officials use this information to track outbreaks and link different cases back to the same contaminated food source.
What does 'susceptibility' mean on my lab results?
If a stool culture was performed, the lab will test different antibiotics against your specific bacteria. 'Susceptible' means the drug should effectively treat the infection, while 'Resistant' means that particular drug will not work.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my lab report show a specific 'serotype' of Salmonella?
  2. 2.Why did you choose a PCR test instead of a stool culture, and should I still have a culture done?
  3. 3.My results show the bacteria is 'resistant' to certain antibiotics—does this change my treatment plan?
  4. 4.Based on my current symptoms, is it necessary to check my blood for signs of infection?
  5. 5.Do these results need to be reported to the local health department?

Questions For You

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Related questions

What Is the Difference Between NTS and Typhoid Fever?

References

References (11)
  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

    A case of a renal abscess caused by Salmonella bareilly in a previously healthy boy.

    Nakamura T, Ido M, Ogawa M, et al.

    BMC infectious diseases 2022; (22(1)):241 doi:10.1186/s12879-022-07229-1.

    PMID: 35272623
  3. 3

    Rapid and Sensitive Detection of Salmonella in Chickens Using Loop-Mediated Isothermal Amplification Combined with a Lateral Flow Dipstick.

    Liu Z, Zhang Q, Yang NN, et al.

    Journal of microbiology and biotechnology 2019; (29(3)):454-464 doi:10.4014/jmb.1712.12010.

    PMID: 30939631
  4. 4

    Salmonella Serovar Wiki: a curated web portal providing a comprehensive summary of Salmonella serovars for academia, industry, and public health.

    Yang L, Yates CR, Phaophu P, et al.

    mSphere 2025; (10(11)):e0045525 doi:10.1128/msphere.00455-25.

    PMID: 41114580
  5. 5

    Update on Shigella and Nontyphoidal Salmonella Antimicrobial Drug Resistance: Implications on Empirical Treatment of Acute Infectious Diarrhea in Cambodia.

    Poramathikul K, Wojnarski M, Sok S, et al.

    Antimicrobial agents and chemotherapy 2021; (65(11)):e0067121 doi:10.1128/AAC.00671-21.

    PMID: 34398671
  6. 6

    Nontyphoidal Salmonella bacteremia in antiretroviral therapy-naïve HIV-infected individuals at three public hospitals in Eastern Ethiopia: prevalence, antimicrobial susceptibility patterns, and associated factors.

    Mitiku H, Weldegebreal F, Marami D, Teklemariam Z

    HIV/AIDS (Auckland, N.Z.) 2019; (11()):23-29 doi:10.2147/HIV.S193166.

    PMID: 30858731
  7. 7

    Multi-drug resistant non-typhoidal Salmonella associated with invasive disease in western Kenya.

    Akullian A, Montgomery JM, John-Stewart G, et al.

    PLoS neglected tropical diseases 2018; (12(1)):e0006156 doi:10.1371/journal.pntd.0006156.

    PMID: 29329299
  8. 8

    Invasive Non-typhoidal Salmonella (iNTS) Infections.

    Fierer J

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2022; (75(4)):732-738 doi:10.1093/cid/ciac035.

    PMID: 35041743
  9. 9

    Malaria Parasite-Mediated Alteration of Macrophage Function and Increased Iron Availability Predispose to Disseminated Nontyphoidal Salmonella Infection.

    Lokken KL, Stull-Lane AR, Poels K, Tsolis RM

    Infection and immunity 2018; (86(9)) doi:10.1128/IAI.00301-18.

    PMID: 29986892
  10. 10

    Highly antimicrobial-resistant Nontyphoidal Salmonella from retail meats and clinical impact in children, Taiwan.

    Chang YJ, Chen MC, Feng Y, et al.

    Pediatrics and neonatology 2020; (61(4)):432-438 doi:10.1016/j.pedneo.2020.03.017.

    PMID: 32340872
  11. 11

    Mechanisms to Evade the Phagocyte Respiratory Burst Arose by Convergent Evolution in Typhoidal Salmonella Serovars.

    Hiyoshi H, Wangdi T, Lock G, et al.

    Cell reports 2018; (22(7)):1787-1797 doi:10.1016/j.celrep.2018.01.016.

    PMID: 29444431

This page explains testing and diagnostic terms for Salmonella for educational purposes. Always consult your healthcare provider or infectious disease specialist to properly interpret your specific lab results.

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