What is the causative organism of Q fever?

DSSSB 13 August 2024

Microbiology

Easy

Appeared in: DSSSB 13 August 2024

Explanation

Coxiella burnetii is the specific bacterium responsible for causing the zoonotic disease known as Q fever.
This organism is an obligate intracellular pathogen, meaning it can only replicate inside the cells of its host.
The primary mode of transmission to humans is through the inhalation of contaminated aerosols from infected livestock, such as sheep, goats, and cattle, particularly from birth products.
Due to its high infectivity and aerosol transmission, it is also considered a potential agent of bioterrorism.

Option A: Treponema pallidum is a spirochete bacterium that causes syphilis, a sexually transmitted infection with distinct stages (primary, secondary, latent, tertiary).
Option C: Clostridium tetani is an anaerobic, spore-forming bacterium found in soil that produces a potent neurotoxin causing tetanus (lockjaw), characterized by severe muscle spasms.
Option D: The genus Corynebacterium includes many species, but the most clinically significant is Corynebacterium diphtheriae, which causes diphtheria, an acute upper respiratory illness characterized by a pseudomembrane formation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of infectious diseases, specifically Q fever as background academic context rather than a clinical decision trigger.
A key nursing intervention is obtaining a thorough patient history, including occupational and environmental exposures. Asking about contact with livestock (especially sheep, goats, cattle), farming, or work in a veterinary or abattoir setting is crucial for diagnosing Q fever.
Nurses should be aware of the two forms of Q fever. Acute illness may mimic the flu or pneumonia. Chronic Q fever is a serious complication that can lead to fatal endocarditis, often in patients with pre-existing heart valve defects or who are immunocompromised.
What if? If a patient with a history of valve replacement surgery presents with a prolonged fever of unknown origin and negative blood cultures, the nurse should recognize this as a high-risk scenario for culture-negative endocarditis, with chronic Q fever being a primary differential diagnosis to investigate.

How to Approach the Question

Identify the core of the question: it asks for the specific causative agent of the disease 'Q fever'.
Recognize this as a factual recall question from microbiology.
Systematically review the options, recalling the disease associated with each pathogen.
Recall or deduce that Coxiella burnetii is the classic cause of Q fever.
Eliminate the other options by confirming they cause different diseases: Treponema pallidum (Syphilis), Clostridium tetani (Tetanus), and Corynebacterium (Diphtheria). This process validates the correct choice.

Concept Tested & Keywords

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 1919-1921