Q76 Match the pathogen with the appropriate disease.
| Pathogen | Disease |
|---|---|
| (P) Streptococcus pyogenes | (i) Scarlet fever |
| (Q) Brucella species | (ii) Pot’s disease |
| (R) Mycobacterium tuberculosis | (iii) Traveler’s diarrhea |
| (S) Escherichia coli | (iv) Undulant fever |
Correct Answer: (A) (i)-(I), (ii)-(iv), (iii)-(II), (iv)-(iii)
Streptococcus pyogenes matches scarlet fever due to its production of pyrogenic exotoxins causing the characteristic rash and pharyngitis. Brucella species causes undulant fever, known for its fluctuating fever pattern from zoonotic transmission. Mycobacterium tuberculosis leads to tuberculosis, a chronic lung infection spread via airborne droplets. Escherichia coli, particularly enterotoxigenic strains, is the primary cause of traveler’s diarrhea in travelers to high-risk areas.
Option Analysis
Each pathogen links to one disease based on established microbiology.
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Streptococcus pyogenes (i) with Scarlet fever (I): This gram-positive bacterium produces erythrogenic toxins like SPE-A, triggering the “sandpaper” rash, strawberry tongue, and sore throat in children. Matches perfectly as no other option fits this toxin-mediated syndrome.
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Brucella species (ii) with Undulant fever (iv): These intracellular coccobacilli cause brucellosis, featuring undulating fevers from animal exposure like unpasteurized milk. Excludes others as it uniquely matches zoonotic fever patterns.
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Mycobacterium tuberculosis (iii) with Tuberculosis (II): This acid-fast bacillus causes TB via lung granulomas and cavitation. Airborne transmission distinguishes it from diarrheal or rash diseases.
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Escherichia coli (iv) with Traveler’s diarrhea (iii): Enterotoxigenic E. coli (ETEC) produces heat-labile/heat-stable toxins leading to watery diarrhea in 30-60% of cases abroad. Not linked to fevers or respiratory issues.
Why Other Options Fail
Options B-D mismatch key pathogen-disease pairs, ignoring clinical hallmarks.
| Option | Mismatch Explanation |
|---|---|
| B: (i)-(I), (ii)-(II), (iii)-(iv), (iv)-(iii) | Brucella with TB ignores zoonosis; TB with traveler’s diarrhea skips lung pathology. |
| C: (i)-(ii), (ii)-(iii), (iii)-(II), (iv)-(iv) | Streptococcus pyogenes with Pott’s disease confuses toxin rash with spinal TB. |
| D: (i)-(I), (ii)-(iii), (iii)-(iv), (iv)-(ii) | E. coli with undulant fever overlooks bacterial toxin diarrhea vs. intracellular fever. |
In pathogen disease matching CSIR NET questions, linking microbes like Streptococcus pyogenes to scarlet fever or Escherichia coli to traveler’s diarrhea tests core microbiology for competitive exams. These pairings hinge on toxin profiles, transmission modes, and symptoms—key for life sciences aspirants tackling bacterial pathogenesis.
Core Pathogen Profiles
Pathogen disease matching CSIR NET relies on distinct traits.
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Streptococcus pyogenes: Group A beta-hemolytic streptococci release pyrogenic exotoxins (SPE-A/B/C) via lysogeny, causing scarlet fever’s erythematous rash and pharyngitis. Incubation: 2-5 days; peaks in children.
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Brucella species (e.g., B. melitensis): Gram-negative coccobacilli invade macrophages, yielding undulant fever (brucellosis) with waves of 40°C fever, sweats, hepatosplenomegaly from unpasteurized dairy.
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Mycobacterium tuberculosis: Slow-growing acid-fast rods form caseous granulomas in lungs, driving tuberculosis (pulmonary cavitary lesions, night sweats). Pott’s disease is its spinal variant.
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Escherichia coli (ETEC): Produces LT/ST enterotoxins activating adenylate/guanylate cyclase, causing traveler’s diarrhea—acute watery stools in 40-60% of visitors to endemic areas.
Exam Strategies
For pathogen disease matching CSIR NET, eliminate via transmission.
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Zoonotic fever? Brucella (not E. coli).
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Toxin rash? S. pyogenes (not TB).
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Airborne chronic cough? M. tuberculosis.
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Travel-related diarrhea? ETEC.
Practice recalls virulence factors: exotoxins for scarlet fever, intracellular survival for brucellosis/TB.
Clinical Relevance
These matchups inform diagnostics—throat swab for GAS, blood culture for Brucella, sputum AFB for TB, stool toxin assay for ETEC. CSIR NET emphasizes such applied microbiology for bioterrorism or epidemiology units.
