L18- Fungi – Host-Pathogen Interactions

These flashcards cover key concepts related to fungi, host-pathogen interactions, and the implications for public health as discussed in the lecture.

How many deaths are attributable to fungal pathogens each year?

Approximately 68 million deaths globally, with a significant proportion linked to non-communicable diseases and injuries.

What led to the emergence of fungi as major public health concerns?

Improved treatment of cancer and organ failure, climate change, shifting human interactions with environments, and aging populations.

What are the optimal growth temperatures for many fungi?

20-30°C, while the core mammalian body temperature is 37°C.

What does 'Titanisation' refer to in Cryptococcus pathogenicity?

The transition of Cryptococcus from yeast to Titan cells which avoid phagocytosis.

What is the mortality rate associated with cryptococcosis?

Approximately 112,000 deaths from cryptococcosis each year.

What are 'micro' or 'drop' cells in Cryptococcus?

Small cells, 2-4 μm in size, that include a thickened cell wall.

How does Cryptococcus neoformans evade the host immune system?

By inducing resistance to phagocytosis through Titanisation and capsule molecules that drive an anti-inflammatory immune response.

What is nutritional immunity?

The sequestration of essential transition metals by the host to limit nutritional access to pathogens.

How does Candida albicans affect macrophages?

It targets macrophages and can switch to pseudohyphal growth inside them, leading to cell lysis.

What is the significance of the glyoxylate cycle in Candida?

It allows Candida to convert fats to glucose, providing a survival advantage in nutrient-poor environments.

What environmental factors contribute to the emergence of Candida auris?

Environmental hardiness, temperature variation, and simultaneous presence across multiple continents indicating a break in endothermy.

What characterizes the hypervirulent Cryptococcus gattii outbreak on Vancouver Island?

Increased capacity to replicate inside macrophages and unusual morphological adaptations.

What is the resistance of Cryptococcus strains to environmental predation associated with?

Quantitative Trait Locus (QTL) mapping of strains identifying allele variants conferring resistance.

What distinguishes paracytosis in Cryptococcosis pathology?

Protease-dependent passage through tight junctions of endothelial cells in the brain.

How does nutritional immunity impact the virulence of fungi like Rhizopus?

Host iron metabolism defects correlate with increased Rhizopus growth and virulence.

What can be inferred about people's susceptibility to fungal infections?

Some individuals may be more prone to fungal infections due to genetic variations and immune responses.

What role does macrophage interaction play in fungal pathogenesis?

Macrophages provide a poor nutritional environment which fungi like Candida exploit for their growth.

What factors contribute to the high mortality of invasive candidiasis?

Fast progression of the disease and high fatality rates (40-60%).

What are the primary mechanisms for dissemination of Cryptococcus into the brain?

Paracytosis, transcytosis, and 'hitchhiking' or 'Trojan horse' mechanisms.

What is a significant challenge in understanding host-pathogen interactions with fungi?

The rudimentary understanding of immune responses to fungal pathogens.

Why is Candida auris considered a worrying new fungal pathogen?

Its rapid spread, high mortality rate, and resistance to many frontline antifungals.

What is meant by 'accidental pathogen hypothesis' as applied to fungi?

The idea that interactions with environmental predators shape the evolution of virulence traits in fungal pathogens.

Which fungal pathogen caused mucormycosis and is associated with high mortality?

Mucorales fungi, with mortality rates greater than 50%.

Which pathway allows Candida to thrive in macrophages despite nutritional poverty?

The glyoxylate cycle, enabling conversion of fats to glucose.

What type of immune response does Cryptococcus induce through its evasion strategies?

An anti-inflammatory immune response, rather than a pro-inflammatory TH1 response.

Which Cryptococcus species is notably recognized for its virulence in immunocompetent individuals?

Cryptococcus gattii.

What phenomenon is observed in the shape and structure of mitochondria in hypervirulent strains of Cryptococcus?

Unusual tubular morphology, which differs from the wild type.

What environmental adaptations might contribute to the virulence of emerging fungal pathogens?

Pre-adaptation to life in hosts and avoidance of environmental predation.

What mechanisms do Cryptococcus use to evade phagocytic immune cells?

Titanisation, immune evasion mechanisms, and morphologic adaptations.

What public health risks do fungal pathogens pose in the context of climate change?

The changing environment can lead to increased virulence and spread of previously non-pathogenic fungi.

How does the immune response to fungal pathogens exemplify a link between innate and adaptive immunity?

Host recognition of fungal PAMPs and subsequent immune activation illustrates this connection.