MIP A56: Medical Mycology Flashcards
What is sick building syndrome?
Presents with fatigue, headache, and difficulty concentrating associated with living/ working in mouldy environments
True or False: Any fungus that can grow at 37 C is a potential pathogen in a immunosuppressed host
True
What are the different groups of fungi based on type of interaction with the host?
Primary (true) pathogens (can cause desease in immunocompetant persons); Opportunistic pathogens (restricted to debilitated or immunosuppressed persons); Commensal (normally benign but can become oppurtunits); Saprobes (limited/ negligible disease causing ability)
What are the two general courses a fungal infection can take?
1) Slowly progressive chronic infections in immunocompetant patients 2) Life-threatening acute infections in compromised patients
What are the two major ways we come into contact with fungi?
Environmental (incidental); or from our normal Flora
What are the routes of fungal entry into the human body?
Inhalation, Skin and mucosal surfaces, penetration of the skin,
True or False: There is no TLR that has affinity for fungal cell wall components.
False- TLRs play an important role in the innate microbial recognition of fungi
Expression of what class of molecules allows fungi to bind to host/cells and tissue?
Adhesins
What are the ways by which fungi can interfere with PAMP-PRR?
Shielding immunostim. PAMPs by the cell wall; MOdulate inflammatory signals; different morphotypes
Besides interfering with the PAMP-PRR system, what are the other ways that fungi evade host recognition?
Persiting in the intracellular environment, Interference with phagocytosis, complement evasions
How do fungi cause damage to the host?
Secretion of damaging enzymes (phospholipases, catalases, keratinases), induction of cytokines–> inflammation; moulds secrete mycotoxins (aflatoxin)
What fungal virulence factors are more common in eukaryotic pathogens but not prokaryotes?
Ability to switch cell type, morphological forms (dimorphism), and cell wall barriers
What fungal virulent attributes allow for invasion/evasion and survival?
Thermotolerance, acquisition of nutrients, adaptation to stress (differential gene expression)
What are superficial mycoses?
Superficial, cosmetic infections of the skin (stratum corneum) or hair shaft
What is the most common superficial mycosis in the US?
Tinea (pityriasis) versicolor (Liver spots) caused by Malassezia spp.
What are the causative organisms that cause cutaneous mycoses?
Dermatophytes and Candida
What are the common cutaneous mycoses?
Athlete’s foot, ringworm, jock itch
What is the name of the category of diseases caused by a fungus?
Mycoses
True or False: Fungal cell walls contain peptidoglycan.
False
Why has the incidence of fungal infections increased?
Increased immunocompromised and elderly population and modern medical techniques
What characteristic separates fungal cells from animal cells?
Fungal cells are non motile
What characteristic separates fungal cells from plant cells?
Fungi are heterophlic
What is chitin?
A structural polymer of N-acetylglucosamine that is part of fungal cell walls
What are the two growth forms fungi can take?
Yeast or mold
What is the difference between dimorphic and polymorphic fungi?
Dimorphic fungi grow as mold or yeasts during specific stages of their life cycles, while polymorphic fungi have multiple growth forms but they do not correlate to a distinct stage of the life cycle
How do yeast forms of fungi reproduce?
Asexual budding or fission
What are hyphae?
Filamentous, cylindrical cells of mold fungi (one cell=hypha)
What is a mycelium?
A mass of hyphae
What is the morphologic appearance of aspergillus fumigatus hyphae?
The hyphae branch at 45 degree angles
What is sporulation?
Propagation of fungi through formation of propagules that disperse in water or air
What is conidiogenesis?
The method of sporulation
True or False: Fungal spores can be either sexual or asexual
True
What does calcofluor stain?
Chitin
What are mycotoxicoses?
Poisoning by food products contaminated by toxins which were produced from the grain substrate by fungi
What is mycetismus?
The ingestion of preformed toxin (neurotoxins) (mushroom poisoning)
What is typically the route of infection for subcutaneous mycoses?
Traumatic implantation of environmental fungi, normally in the lower extremities
What is the most frequent subcutaneous fungal infection worldwide?
Sporotrichosis (sporothrixi schenckii)
What is the morphology of sporotrichosis?
Mold in the environment but yeast at 37 C ; cigar shaped yeast
How is chronic mycotic infection of cutaneous or subcutaneous tissues and adjacent lymphatics characterized?
Granulamatous skin ulcer followed by regional lymphadenopathy
Where does extracutaneous sporotrichosis manifest?
In joints
What is black mold?
Over 100 species of evironmental mold with melanin pigmint in the cell walls
What is chromoblastomycosis?
Cutaneous and subcutaneous mycosis with chronic granulomas especially feet and legs caused by black molds
What are the three clinical presentations of phaeohyphomycosis?
Cutaneous-subcutaneous cyst; Cerebral abscess & other deep seated sites; Fungal sinusitis- allergic
What is penicilliosis and what is its clinical presentation?
A dimorphic fungal AIDS opportunistic infection that presents with pulmonary symptoms is most AIDS pts and skin dissemination of molluscum-like lesions
What is the most common fungal agent for life threatening infections? Which species is most common in almost all disease manifestations?
Candidiasis; albicans
What is the most common opportunistic fungal pathogen?
Candida
What is candida’s morphology?
Polymorphic: yeast, pseudohyphae, and true hyphae
How is Candidiasis likely to manifest in a patient with a CD4+ T cell defect?
Oral candidiasis (thrush)
How is Candidiasis likely to manifest in a patient with neutropenia?
Systemic candidiasis
What does thrush look like?
Creamy, white curd-like plaques on oral mucosal surfaces
What is mucormycosis?
Fungal infection of the sinuses, brain, or lungs primarily associated with immunosuppressed patients
Why is mucomycosis potentially fatal?
The hyphae can colonize vessels leading to the formation of blood clots
What is the most common fungi isolated from contact lens cases?
Fusarium keratitis
