Widal, a serological test, is used to detect the presence of which of the following pathogenic microorganisms?

AIIMS Patna NO - 2020

Microbiology

Easy

Appeared in: AIIMS Patna NO - 2020

Explanation

The Widal test is a serological assay specifically designed to aid in the diagnosis of typhoid fever (enteric fever).
It functions by detecting agglutinating antibodies in the patient's blood serum against the O (somatic) and H (flagellar) antigens of the bacterium Salmonella typhi.
While blood culture is the gold standard, the Widal test is widely used, especially in resource-limited settings. A four-fold or greater rise in antibody titer between acute and convalescent samples is considered diagnostic of an active infection.

Option A: Infections caused by E. coli, such as gastroenteritis or UTIs, are not diagnosed using the Widal test. The standard method is bacterial culture from a stool or urine sample.
Option B: The Widal test has no role in diagnosing tuberculosis. TB is diagnosed using methods like the Mantoux tuberculin skin test, Interferon-Gamma Release Assays (IGRAs), sputum smear microscopy for acid-fast bacilli (AFB), and chest radiography.
Option C: This bacterium causes infections like meningitis and pneumonia. The diagnosis is confirmed by isolating the organism from a normally sterile site, such as blood or cerebrospinal fluid (CSF), through bacterial culture.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Diagnostic application of the Widal test for enteric fever as background academic context rather than a clinical decision trigger.
Nurses are responsible for collecting blood samples for the Widal test. It is crucial to label samples correctly and, if possible, collect paired sera (acute and convalescent phase) to demonstrate a rising titer, which provides a more definitive diagnosis.
Patient education is key. Nurses should explain that typhoid fever is spread through contaminated food and water and teach preventive measures like hand hygiene and consuming safe food and water.
Understanding the limitations of the Widal test (e.g., false positives from prior vaccination or other infections) is vital. Nurses must correlate lab results with the patient's clinical presentation and history.

How to Approach the Question

First, identify the key term in the question: 'Widal test'.
This is a factual recall question that tests your knowledge of specific microbiological diagnostic tests.
Access your memory about the diseases for which common serological tests are used. The Widal test is classically associated with one specific febrile illness.
Evaluate the options provided. Salmonella typhi is the causative agent of typhoid fever.
Connect the test (Widal) with the disease (typhoid fever) and the causative organism (Salmonella typhi).
Eliminate the other options, as they are diagnosed using different methods (e.g., culture for E. coli, Mantoux test for TB).

Concept Tested & Keywords

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