Legionella pneumophila: Characteristics and Pathogenesis

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Why is Legionella pneumophila able to proliferate within environmental water sources and cause outbreaks in hospitals?

Legionella produces a potent exotoxin that inhibits the action of disinfectants in water systems.
Legionella exhibits rapid mutation rates, quickly developing resistance to common water treatment methods.
Legionella forms biofilms on pipes, providing a protective environment against disinfectants.
Legionella replicates within free-living amoebas, which colonize and persist in these water systems. (correct)

A patient presents with severe pneumonia, mental confusion, non-bloody diarrhea, proteinuria, and microscopic hematuria. Sputum Gram stain reveals many neutrophils, but no visible bacteria. Which laboratory finding would most strongly suggest Legionella pneumonia over other bacterial pneumonias?

Hyponatremia (reduced serum sodium). (correct)
Presence of acid-fast bacilli in sputum.
Elevated white blood cell count with a left shift.
Elevated levels of C-reactive protein (CRP).

Why are older men who smoke and consume substantial amounts of alcohol at higher risk of contracting Legionnaires' disease?

Smoking and alcohol alter the pH of the respiratory tract, creating a more favorable environment for Legionella.
Smoking and alcohol consumption directly promote the growth and virulence of Legionella pneumophila in the lungs.
These behaviors increase the likelihood of exposure to contaminated water sources, thus raising infection risk.
These habits cause immunosuppression and damage the respiratory tract, impairing the ability to clear the bacteria. (correct)

How does the pathogenesis of Pontiac fever differ from that of Legionnaires' disease?

Pontiac fever is characterized by a strong inflammatory response to bacterial components, but without bacterial proliferation in the lungs, unlike Legionnaires' disease. (A) Signup and view all the answers

What is the significance of Legionella's ability to grow on charcoal yeast extract agar supplemented with L-cysteine and iron?

L-cysteine and iron are essential nutrients that Legionella requires for growth, as it cannot synthesize them independently. (D) Signup and view all the answers

How does the intracellular lifestyle of Legionella pneumophila contribute to its virulence and ability to cause disease?

Intracellular replication allows Legionella to evade detection by the host's immune system and resist antibiotic treatments. (C) Signup and view all the answers

Why is the detection of Legionella pneumophila antigens in urine a clinically useful diagnostic method?

This method is rapid, non-invasive, and can detect Legionella even after antibiotic treatment has been initiated. (C) Signup and view all the answers

What is the rationale behind using azithromycin or erythromycin to treat Legionella pneumonia, considering its intracellular lifestyle?

Azithromycin and erythromycin accumulate within host cells, achieving high intracellular concentrations necessary to eradicate Legionella. (D) Signup and view all the answers

How might climate change potentially influence the epidemiology and geographic distribution of Legionella outbreaks?

Increased frequency of extreme weather events, such as floods, could disrupt water treatment systems, leading to wider dissemination of Legionella. (D) Signup and view all the answers

If a hospital implements a new water management system to control Legionella, which monitoring strategy would be most effective in assessing the system's long-term efficacy?

Periodic culturing of water samples from distal outlets and cooling towers for Legionella, combined with clinical surveillance for Legionnaires' disease. (B) Signup and view all the answers

Flashcards

Legionella pneumophila

Gram-negative rods that stain faintly with Gram stain. They are facultative intracellular bacteria that multiply in free-living amoeba and require L-cysteine and iron for growth on special media like charcoal yeast agar.

Legionella's primary reservoirs

Environmental water sources such as air conditioners and water cooling towers. Outbreaks can occur in hospitals from water taps, sinks, and showers.

Legionella Transmission

Inhalation of aerosolized bacteria within amoebas or by swimming in contaminated water. There is no person-to-person spread.

Typical Legionella candidate

An older man who smokes and consumes substantial amounts of alcohol. Patients with AIDS, cancer or transplants or patients being treated with corticosteroids are also susceptible.