MP NHM CHO-2024 (Shif…: Shiga toxin is produced by \ \ \ \ \ \ .

MP NHM CHO-2024 (Shift-2)

Applied Microbiology & Infection control

Easy

Appeared in: MP NHM CHO-2024 (Shift-2)

Explanation

Certain strains of Escherichia coli, known as Shiga toxin-producing E. coli (STEC), are responsible for producing Shiga toxin.
STEC produces two major types of Shiga toxins, Stx1 and Stx2, which are structurally and functionally similar to the toxin from Shigella dysenteriae.
The toxin inhibits protein synthesis in host cells, leading to cell death, which manifests as hemorrhagic colitis (bloody diarrhea).
A severe complication of STEC infection is Hemolytic Uremic Syndrome (HUS), characterized by acute kidney failure, thrombocytopenia, and hemolytic anemia.

Option A: Salmonella typhi does not produce Shiga toxin. It is the causative agent of typhoid fever.
Option B: Streptococcus pyogenes produces exotoxins like streptolysins and erythrogenic toxins, not Shiga toxin.
Option D: Staphylococcus aureus produces a range of toxins including enterotoxins (food poisoning) and TSST-1 (Toxic Shock Syndrome), but not Shiga toxin.

Visual 1: Diagram: Mechanism of Shiga Toxin - An illustration showing the A and B subunits of the toxin binding to a host cell, entering it, and inhibiting protein synthesis at the ribosome.
Visual 2: Infographic: Comparison of Bacterial Enterotoxins - A chart comparing the source, mechanism, and clinical effects of toxins from E. coli (STEC), Salmonella, Staphylococcus aureus, and Vibrio cholerae.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Bacterial Pathogenesis and Toxin Production as background academic context rather than a clinical decision trigger.
Nurses must recognize that bloody diarrhea can be a sign of a serious STEC infection and requires prompt evaluation.
A critical nursing intervention is to monitor for signs of Hemolytic Uremic Syndrome (HUS), including decreased urine output, edema, pallor, and petechiae. Monitoring renal function (BUN, creatinine) and complete blood count (platelets, hemoglobin) is essential.
It is crucial to know that antibiotics are generally contraindicated for STEC infections, as they can cause bacterial lysis and increase the release of Shiga toxin, potentially worsening the risk of developing HUS.

How to Approach the Question

First, identify the core of the question, which is to link a specific bacterial toxin ('Shiga toxin') to its source.
This is a factual recall question from microbiology. Access your knowledge about common pathogenic bacteria and the diseases/toxins they produce.
Systematically evaluate each option. Think: 'What is Salmonella typhi known for?' (Typhoid fever). 'What about Streptococcus pyogenes?' (Strep throat, scarlet fever).
Recall or deduce that 'Shiga toxin' is famously associated with certain strains of E. coli (STEC), particularly the O157:H7 strain, known for causing severe foodborne illness.
Confirm that E. coli is the best fit among the given choices, eliminating the other bacteria based on the distinct toxins they produce.

Concept Tested & Keywords

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E6 Microbiology Applied AnjuDhir 3e Part 1 p. 54-70