Fungi Flashcards
Mycology
Study of fungi
Fungi Kingdom
Eumycota
Fungi are _ organisms
Eukaryotic
Cell membranes are composed of
ergosterol
Cell walls are composed of
Glucans, chitin
Fungus metabolism
Heterotrophic
Bacteria characteristics
Prokaryotes
Cell membrane- proteins, phospholipids
Cell wall- peptidoglycan, LPS
Metabolism- heterotrophic
Human characteristics
Eukaryotes
Cell membrane- cholesterol
Cell wall not present
Metabolism- heterotrophic
Plant characteristics
Eukaryotes
Cell membrane- sterols
Cell wall- cellulose
Metabolism- autotrophic
2 types of fungi
Yeast
Mold (fleshy fungi-mushroom, filamentous molds)
Dimorphic
Can be yeast or mold depending on environmental conditions
Yeast morphology
Unicellular
Non-filamentous (budding, pseudohyphae)
Budding yeast with pseudohyphae are
Candida species (gram +)
Molds morphology
Multi-cellular
Filamentous (hyphae, can be septate or non-septate)
Interwoven hyphae form mycelium
Reproductive structures (basidium-fruiting bodies, conidia-spores)
Stain for fungi
Lactophenol cotton blue stain
Dimorphic fungus morphological
Mold (room temperature in the environment)
Infectious through inhalation of spores
Yeast (body temperature, diagnostic form)
Not infectious
Systemic disease caused by Dimorphics
Blastomycosis- Blastomyces dermatitidis
Coccidioidomycosis-Coccidioides immitis
Histoplasmosis- Histoplasma capsulatum
Tararomyces- Talaromyces (Penicillium) marneffei
Laboratory diagnosis involves
Direct detection
Culture isolation
Identification
Molecular
Serological
Direct detection from Specimen
Gram stain
KOH preparation
Wet mount
Wood’s lamp
India ink stain
Histopathology
Gram staining
Yeast- stain gram +
Molds stain poorly
KOH preparation
Keratinized tissues (skin, hair, nails)
Look for Dermatophytes (skin infections)
Cutaneous yeast
Wood’s lamp
Hair
Dermatophytosis (ringworm)
Wet mount
Oral or vaginal secretions
Budding yeast
Thrush
India ink
Cerebral spinal fluid
Encapsulated yeast
Cryptococcosis (Cryptococcosis neoformans)- encapsulated yeast
Histopathological
Gomori’s methenamin silver (GMS) stain
Mold hyphae
Detect: Aspergillosis (mold infection) , Mucormycosis/Zygomycosis, Invasive Candidiasis
Sabouround dextrose agar
Low pH, nutritionally deficient
2+ days for yeast
7+ days for mold
can take 4+ weeks
Blastoconidium
Produced by yeast cells
“Budding”
Seen in all yeast species
Biochemical testing
Candida albicans (Germ test tube, 2-3 hr incubation, lateral hyphae extension=positive result)
Other yeast ID methods: biochemical tests, MALDI-TOF MS
Mold identification
Macroscopic characteristics (culture growth)
Microscopic (hyphae structures, reproductive structures)
MALDI-TOF fungal ID
Identify unique species protein in yeast
Detection of fungal antibodies
In serum
Not reliable
Not useful in immunocompromised
Detection of fungal antigens
Latex agglutination (cryptococcal antigen in CSF)
Serum glactomannan (aspergillosis)
Culture confirmation
Nucleic acid probes (Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides immitis/posadasii)
Sequence analysis comparison
Positive blood culture bottle
Bio fire BCID2 panel
True fungal pathogens infect
Normal immune system
Opportunistic fungus affects
Immunocompromised
Fungus pathogenesis
Colonize host
Find suitable environment
Avoid host defense
Multiply
Fungal virulence factors
Thermotolerance
Adhesion (cell surface receptors, biofilm formation)
Growth (use host nutrients)
Immune evasion (capsule, intracellular survival in phagocytes)
How do fungi damage host tissues
Extracellular enzymes (keratinases, phospholipids, urease)
Toxic metabolites (toxins)
Immune overreaction (cytokine storm)
Mycetismus
Poisoning by ingestion of mushroom
Mycotocicosis
Intoxication by eating food contaminates with mycotoxin (aflatoxin poisoning, psilocybin intoxication)
Fungal hypersensitivity disease
Inhalation of fungal elements induces immunological response (contact dermatitis, Hypersensitivity pneumonitis, farmers lung, allergic bronchopulmonary)
Mycoses
Infection caused by fungus
Candida auris
Concerns of multi drug resistance
Fungal infections
Slower growing than bacteria
Endogenous or exogenous
Often infect immunocompromised patients
Classification based on appearance and reproductive mechanism
Fungal cells are _
Eukaryotic
Antifungal medications target
Fungal cell wall and membrane (chitin and beta 1,3 glucan-target for diagnostic testing and medications, ergosteral- another drug target)
Yeast
Round or oval
Budding reproduction
Filimentous fungi
Molds
Tubular appearance (hyphae)
Brow through branching and extension
Dimporphic
Yeast in humans
Mold in labs
Yeast
Round smooth colonies
Stain gram +
Risk factors for Candida infection (part of endogenous human flora)
Neutropenia
Antibiotics
Uncrotrolled diabetes
HIV
Mucosal Candidiasis
Orthopharyngeal: thrush, pseudomembrane
Esophageal: difficulty swallowing
Cutaneous: skin fold or moist areas
Vaginitis: burning, itching, cottage-cheese live discharge
Candidiasis localized organ infection
UTI: caused by cantamination from skin
Peritonitis (intraabdominal infection): after abdominal surgery or bowel perforation
CNS infection: following intracranial surgery (such as shunt placement)
Candidemia
candida in the blood
Hepatospenia Candidiasis
liver/spleen
Osteoarticular candidiasis
bone/joint infection
Endophthalmitis candida
inta-ocular infection
Endocarditis Candida
heart valve
Most common species causing Candida infection
Candida albincans (treated with fluconazole)
Diagnosis of Candida
mucocutaneous: based on physical exam
organ or systemic: cultures, Germ tube (used in C albicans cultures postive for yeast), Assay for 1,3 beta D glucan (detected in fungal cell wall)
Diagnosis of Cutaneous, Orthopharyneal
clinical appearance, wet mount
treat with topical agents (nystatin, clotrimazole or for sever infection azoles, echinocandin)
Diagnosis for esophagitis candidiasis
dysphafia or adynophagia
diagnosis with endoscopy
treat with azoles or echinocandin
Urinary tract Candidiasis
assiciated with urinary instrumentation
Remove catheter, may also use azole or amphotericin B
Disseminated Candidiasis/Candidemia
blood cultures
1,3 beta D glucan assay
Endophthalmitis candidiasis diagnosis
dialated retinal exam
Endocarditis candidiasis diagnosis
blood culture and echocardiogram
Cryptococcus infection
most common fungus causing meningitis
inhaled yeast from environment
C. neoformans: bird droppings
C. gatti: trees (eucalyptus) in west coast
Risk factors for Cryptococcus infection
HIV/AIDs
Cryptococcus pathogenesis
yeast cells surrounded by thick polysaccharide *capsule (allows growth, prevents phagocytosis, supress immune response, interference with antigen presentation, adherance)
Melanin (produced and deposited in cell wall- integrity, protection from phagocytosis/oxidation/temperature extremes)
Cryptococcus spectrum of disease
Respiratory tract (asymtomatic to pneumonia)
CNS (meningitis, cryptococcoma)
Disseminated (fungemia)
Diagnosis of Cryptococcus
Pneumonia: look for nodule, Serum cryptococcal antigen detects polysaccharide capsule
CNS: CSF cryptococcal antigen, India ink stain
Disseminated: serum cryptococcal antigen, need LP to evaluate for CNS involvement
Pneumocytosis jjirovecci
protozoa
oppertunistic infection in immunocomprimised
HIV with CD4<200
prolonged steroid use
aquired through inhalation
likely aquired during childhood and reactivated during immunisupression
Pneumocystis jirovecci causes
diffuse bilateral pneumoia
starts with dry couch/difficulty breathing/hypoxia
causes chronic lung damage with cytic changes
Pneumocystitis diagnosis and treatment
Cannot be cultured
identified using GMS stain
elevated 1,3 beta-D-glucan
Treatment: high dose Bactrim
reverse immunocompromising state
Malassezia furfur clinical syndromes
Cutaneous infection: Pityriasis (tinea) versicolor
hypo (patients with dark skin) or hyperpigmented (patients with light skin) scalded macules interfering with melanin production
Malassezia furfur diagnosis
Skin scraping with KOH prep (spaghetti and meatballs yeast)
Skin lesions fluorescence with wood lamp
Culture requires lipids to grow (add olive oil to culture)
Malassezia furfur treatment
Cutaneous: topical agents
Systemic (Fungiemia): catheter removal, systemic treatment
Dermatophytes
Cause human disease (ringworm)
Keratinolytic (break down skin, hair, nails)
Tinea capitis
Infection on head and face
Tinea barbae
Beard and facial hair
Tinea corporis
Body
Tinea pedis
Foot
Tinea cruris
Groin
Tinea unguium
Toenails, fingernails
Dermatophytes diagnosis and treatment
Clinical appearance
Wood lamp flouresence
Skin/nail scraping with KOH
Culture on Sabouraud agar
Treatment: topical agents
Dimorphic
Histoplasma
Blastomyces
Coccidiodes
Sporothrix
Present in soil (inhalation or direct inoculation)
Primary pathogen in immunocompetent
Histoplasmosis capsulatum
Found in chicken and bat droppings
Conidiophores inhaled and transform to yeast cells
Yeast cells are ingested by macrophages leading to an increase in PH residing efficacy of lysosomal enzymes
Proliferate and destroy macrophages
Histoplasmosis diagnosis and treatment
Culture on Sabouraud agar
Narrow based budding yeast
Cytology with yeast forms via GMS Giemsa or PAS stains
Detection of Histoplasma antigen
Blastomycosis pathogenesis
Grows as hyphal form in environment
Canidia released and transform into yeast within respiratory tract
Blastomyces pathogenesis
Resist phagocytosis by modifying cell wall composition (shed WI-which activates immune response)
Proliferation in tissues and invasion into blood stream
Blastomycosis
Pneumonia
Cutaneous (disseminated infection or direct inoculation)
Bone
CNS
Blastomycosis diagnosis
culture on sabouraud agar
Look for broad based budding yeast
Blastomyces antigen detection
Blastomycosis treatment
Mild cases do not require treatment
Coccidioidomycosis
Live in desert soil
produce ammonia to create alkaline environment
Hyphae fragment into conidia, inhaled
Coccidioidomycosis pathogenesis
Develop into spherules which produce endospores
Less susceptibile to phagocytosis due to urease production
Can enter bloodstream
Coccidioidomycosis disease spectrum
Valley fever
May reactive during immunosuppression
Pneumonia
Meningitis
Cutaneous
Coccidioidomycosis diagnosis and treatment
Culture is insensitive
Coccidioides antigen
Cytology with yeast forms
Serology: EIA
Immunocompetent people don’t usually require treatment
Fluconazole for moderate infection
Saporothrix schenckii
Soil and decaying plant matter
Direct inoculation into skin
Associated with rose gardeners
Causes chronic nodular ulcerative lesions and spreads via lymphatics
Sporotrichosis diagnosis and treatment
Culture
Cytology (cigar shaped yeast)
Treatment with potassium iodine
Filamentous Fungi
Aspergillus species
Pathophysiology of Mold infection
Conidia inhaled and invade respiratory
Attach to epithelium
Conidia swell and germinate in alveoli
Hyphae spread through lung parenchyma and blood vessels causing hemorrhage and necrosis
Aspergillus species
Inhaled from environment (decomposing plants, soil, moist environments)
Profound neutropenia and prolonged steroid use is a risk factor
Aspergillis disease
Allergic bronchopulmonary aspergillosis
Pneumonia
Invasive sinusitis
Cerebral aspergillosis
Aspergillis diagnosis and treatment
Imaging test
Galactomannan (Aspergillis antigen) in serum
1,3 beta D glucan
PCR
Histopathology- septate, acute angle branching
Treatment- Voriconazole
Mucormycosis
*Rhizopus, *Mucormycosis, Lichtheimia, Cunninghamella, Absidia, *Rhizomucor
Inhaled from environment
Risks profound neutropenia, diabetics, steroid use
Mucormycosis Diseases
Rhino-orbital cerebral disease (fungal sinusitis)
Pulmonary
Cutaneous necrotizing fasciitis and necrotic lesions
GI (premature neonates)
Mucormycosis Disease and Treatment
High mortality
Clinical presentation
Glactomannan and 1,3 Beta-D-glucan= negative
Culture and histopathology (pauci-septate, ribbon-like, right angle branching)
Treatment: surgical debridement, reversing immunocompromising conditions
What mold has septate hyphae
Aspergillus
