Which microorganism causes scarlet fever?

RUHS, Jaipur, PB B.Sc Nursing Entrance-2019

Applied Microbiology & Infection control

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2019

Explanation

Scarlet fever is caused by Streptococcus pyogenes, also known as Group A Streptococcus (GAS).
The characteristic rash and symptoms are due to the production of a streptococcal pyrogenic exotoxin (erythrogenic toxin) by the infecting bacterial strain.
This bacterium is also the leading cause of bacterial pharyngitis (strep throat), and scarlet fever is essentially strep throat accompanied by this toxin-mediated rash.
Key diagnostic signs include a sandpaper-like rash, strawberry tongue, and Pastia's lines in skin folds.

Option B: Streptococcus equisimilis belongs to Lancefield groups C or G. While it can cause pharyngitis and cellulitis, it is a rare cause of scarlet fever.
Option C: Enterococcus faecalis is a Group D streptococcus (now classified in its own genus, Enterococcus). It does not cause scarlet fever.
Option D: Enterococcus durans is also a Group D enterococcus and is considered part of the normal intestinal flora. It is rarely associated with human disease.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Causative agent of scarlet fever as background academic context rather than a clinical decision trigger.
Recognizing scarlet fever is crucial for nurses as prompt antibiotic treatment is necessary to prevent severe complications like acute rheumatic fever and glomerulonephritis.
Patient education is a key nursing role, involving teaching about the importance of completing the full course of antibiotics, managing symptoms like fever and sore throat, and preventing transmission through good hand hygiene and avoiding sharing utensils.
Nurses should monitor for signs of complications, such as joint pain/swelling (rheumatic fever) or decreased urine output and edema (glomerulonephritis), even after the initial infection has resolved.

How to Approach the Question

First, identify the core of the question, which is to link a specific disease (scarlet fever) with its causative microorganism.
This is a factual recall question. Access your knowledge base about common infectious diseases and their bacterial causes.
Systematically evaluate each option. Recall or look up the primary diseases associated with each bacterium.
Differentiate between the Streptococcus and Enterococcus genera. Recognize that scarlet fever is a well-known streptococcal disease.
Specifically, associate scarlet fever with Group A Streptococcus, which is Streptococcus pyogenes.
Eliminate the other options by identifying the typical infections they cause (e.g., Enterococcus and UTIs).

Concept Tested & Keywords

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E6 Medicine Davidson Principles Practice 24e p. 272-274

E6 Medicine Harrison 22e Part 1 p. 1250-1252

E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed p. 368-370