Which particular protozoan causes amoebic dysentery?

Appeared in: MNS 2015

Explanation

Entamoeba histolytica is the specific protozoan parasite responsible for causing amoebic dysentery (amoebiasis).
Infection occurs via the fecal-oral route through the ingestion of cysts from contaminated food or water.
In the large intestine, the cysts transform into invasive trophozoites that penetrate the intestinal wall, causing ulcers and bloody diarrhea.
The name 'histolytica' itself means 'tissue-lysing', referring to its ability to destroy host tissues.

Option A: Plasmodium is a protozoan, but it is the causative agent of malaria, not amoebic dysentery.
Option C: Cl. botulism refers to Clostridium botulinum, which is a bacterium, not a protozoan. It causes botulism, a paralytic illness.
Option D: This option is incorrect because a correct answer, Entamoeba histolytica, is provided as one of the choices.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Causative agent of amoebic dysentery as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in preventing the spread of amoebiasis through patient education on hand hygiene and safe food/water practices.
Accurate identification of the causative agent of dysentery is vital, as amoebic dysentery requires specific anti-protozoal medication (like metronidazole), which differs from the antibiotics used for bacterial dysentery (e.g., Shigellosis).
In a hospital setting, implementing contact precautions for patients with amoebic dysentery is essential to prevent nosocomial transmission.

How to Approach the Question

First, identify the key concepts in the question: 'protozoan' and 'amoebic dysentery'. The term 'amoebic' is a strong clue pointing towards an amoeba-like organism.
Next, evaluate each option based on these keywords.
Option A, Plasmodium, is a well-known protozoan but is famous for causing malaria, not dysentery. Eliminate this.
Option B, Entamoeba histolytica, is a protozoan with 'amoeba' in its name. This strongly aligns with 'amoebic dysentery'. Keep this as a likely answer.
Option C, Cl. botulism, refers to a bacterium (Clostridium), not a protozoan. This fails the first keyword test. Eliminate this.
Since Option B is a perfect match, Option D ('None of these') is incorrect. Conclude that Entamoeba histolytica is the correct answer.

Concept Tested & Keywords

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E6 Microbiology Essentials Sastry 4e Part 2 p. 16-18

E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 309-311

E6 Microbiology Applied AnjuDhir 3e Part 2 p. 14-16

Practise the full MNS 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.