Fungi Flashcards
Saprophytic
- live off environment
- secrete enzymes which break down organic matter and use it for nourishment
Eukaryotic Fungi
- membrane enclosed organelles
Mycoses
Fungal disease
Fungi Characteristics
- thick rigid cell walls— set off INNATE immune system
- potent immunogenicity; source of many allergies
- main defense: neutrophils
- divide via budding
Fungi Cell Structure
- Cell Wall
- CHITIN
- not affected by bacterial antibiotics (no peptidoglycan)
- Membrane
- Ergosterol instead of cholesterol
- Antifungal therapies bind and disrupt fungal walls/membranes
Ergosterol and cholesterol are very similar— can cause toxicity in mammals
Molds Morphology
- cells form hyphae
- grow by elongation
- cytoplasmic extension and branching
- mitosis division without cell division/separation
Yeast Morphology
- unicellular
- reproduce via budding (asymmetric division)
Mycelium
Mass of hyphae
Dimorphic Fungi
Mold and yeast
- yeast in tissue (37C)
- Mold culture (25C)
Conditions/enviroment dictate form
Fungi Lifestyle
- Sexual spores: meiosis— classification
- ascus: primary means of species classification
- haploid fuse to diploid
- Asexual spores: mitosis— identification
- budding: yeast
- spore formation: molds
- different types aid with ID
Asexual Spores
- mitosis
- thick walled
- easily dispersed
Conidia vs Sporangium
Conidia: spores made outside specialized cell
Sporangium: spores made within specialized sac
Fungi Laboratory ID
Dematiaceous vs Hyaline
CANNOT ID BASED ON CLINICAL PRESENTATION
- SABORAUD agar
- low pH inhibits bacteria; can add antibiotics
- Dematiaceous (pigmented) vs Hyaline (colorless)
- ID based on morphology of conidia
- serology and immunoflourescence
- treatment may depend more on the site of infection than on the species
At risk populations for fungal infections
- medical procedures
- medical/immunosuppressive therapies
- disease conditions
- lifestyle
Mycoses
Fungal Disease
- most acquired form the environment
Most are NOT contagious
- exception: dermatology test
- symptoms can overlap with other disease — difficult to diagnoseDifficult to treat fungal infections
Cells are similar to ours — drugs need to be very specific in order not to hurt the humans
Superficial/Cutaneous Mycoses
- outermost layers of skin, hair and nails
- no invasion of deeper tissue
- involve only the skin
Subcutaneous Mycoses
- localized infections of deeper tissue
- no spread to distant sites
Systemic Mycoses
- start as local infection (often in lungs)
- spread elsewhere
Opportunistic Mycoses
- usually respiratory
- important in AIDS, transplants, immunosuppression, and chemotherapy
Pityriasis Versicolor
Superficial mycoses
- scaly patches of discolored skin
- primarily ontorso and upper arms
- diagnose via skin scraping
- KOH/microscopic examination (KOH gets rid of our cells)
- treatment: topical antifungals
Piedra
Superficial Mycoses
- fungal growth on hair shafts
- can be visualized under UV lamp
- environmental
- treatment- shaving hair and topical antifungal
Dermatophytes
CAN BE SPREAD THROUGH CONTACT
- caused by Tinea
- lesion with inflamed rim of active infection, central clearing
- skin infections are prurience (itchy) and scaly)
- depends of geographic location
- source: soil, animals, humans
- distinguished by micro- and macroconidia
- more common in hot humid climate
Tinea
LOVES KERATIN
- causes dermatophytes
- fungal infection of keratinized tissues
- breaks in skin can lead to secondary bacterial infections
- ONLY dangerous if breaks in skin
- any site on body
Tinea corporis Tinea capitis Tinea barbae Tinea pedis Tinea unguium Tinea cruris
Corporis: ring worm Capitis: scalp Barbae: beach Pedis: athlete’s foot Unguium: toenail Cruris: jock itch
Treatment of cutaneous mycoses
Tinea corporis and pedis
Tinea capitis and barbae
Tinea unguium
c&p: topical antifungals
c&b: systemic treatment (oral better)
u: topical or oral treatment depending on the severity
Subcutaneous mycoses
Deeper but local
- fungi introduced by local trauma
- exposure is often occupational
Sporotrichosis (Sporothrix schenkii)
Sporotrichosis
Subcutaneous mycoses
“ROSE GARDENER’S DISEASE”
- puncture becomes granulomatous
- secondary lesions along draining lymphatic
- DIMORPHIC
- yeast: tissue
- mycelia form: culture
- SELF LIMITING
- can be persistent
- can become systemic in immunocompromised
- oral therapySystemic Mycoses
TRUE PATHOGENS: infect healthy people - *endemic to specific areas* - present in soil - exposure often occupational - infection initially in lung; can spread elsewhere - most infections asymptomatic except in immunosuppressed - can present like Tb LITTLE TO NO HUMAN TRANSIMISSION
Systemic Mycoses
Dimorphic
- yeast in tissue
- hyphae in culture
- slow growing in culture
- PCR of Immunocompromised assay for diagnosis
Histoplasma
INTRACELLULAR PARASITE
- spores in soil with bird droppings or bat guano
- initial infection in lungs
- most infected people have no symptoms
- can be chronic or rarely fatal
- ACTURE PULMONARY DISEASE but self-limiting
- can present like Tb
- immunodeficiency/immunocompromised
Histoplasma Diagnosis and Treatment
- from soil
- slow to culture
- Diagnosis: antigen detection in urine or serum
- Treatment: only severe cases require oral anti-fungal
OHIO and MISSISSIPPI RIVER VALLEYS
(Central US)
Blasotomyces
Systemic mycoses BLASTO: BROAD BASED BUDS - approximately 50% show symptoms - initially respiratory then spreads - soil -> lungs - germinate into THICK WALLED YEAST CELLS WITH UNIPOLAR BROAD BASED BUDS
Blastomyces
Diagnosis and Treatment
BLASTO: BROAD BASED BUDS Diagnosis- antigen test of culture Treatment- oral anti-fungal, depending on severity ID- culture and microscopy SOUTHEAST US and NORTH to CANADA
Coccidioides
Systemic mycosis
- spores inside break apart
- enter lungs
- fever with varying degrees of respiratory illness
- GERMINATE- develop into large spherules filled with many spores
- rupture releases endospores which spread in blood
- bone, CNS (meningitis)
Coccidioides
Diagnosis and Treatment
- can infect laboratory personnel
- Diagnosis: culture and serological tests
- Treatment: usually self-limiting
VALLEY FEVER: SOUTHWEST US, central and South America
Paracoccidioides
Systemic mycosis - lungs -> mucus membranes - painful sores - ID via conidia (slow growing) - SHIP STEERING WHEEL: multiple buds - affects males > females (estrogen inhibits?) - Diagnose via microscopic examination CENTRAL and SOUTH AMERICA
Opportunistic Mycoses
- rare in healthy
- nosocomial infection
- only induce disease in immunocompromised
- can affect most organs of the body
Candidiasis
Opportunistic Mycoses
YEAST
- produces budding yeast and elongated yeast (pseudohyphae)
- microbiota keeps in check
- most common nosocomial pathogen
- diagnosis and treatment depends on type of infection
Oral Thrush
Candidiasis
- raised white plaque in mouth
- ulcer spread to throat/esophagus
Vaginal candidiasis
Opportunistic
- itching and burning
- white discharge
Systemic Candidiasis
- can be life threatening
- GI, liver, kidney, and spleen
Crypto coccus
Encapsulated!
- worldwide
- bird droppings
- thick polysaccharide capsule
- infections start in lungs, spread to brain or meninges
- cough, fever, chest pain, weight loss
Diagnosis: culture; latex agglutination test
Treatment: oral anti-fungal depending on severity
Small amount not immunocompromised
Aspergillus
- ubiquitous in environment
- grows only as hyphae!
- 45 DEGREE BRANCHING HYPHAE WITH SEPTA
Aspergillosis
- rarely pathogenic in normal patient: self limiting if not immunocompromised
- mostly pulmonary (inhaled)
- acute infection
- severe, often fatal
- infect lung -> brain, GI +
- less severe pulmonary infection: fungus ball
- mass of hyphae in lung cavities
- aspergilloma
- ID: hyphae mass
- Diagnosis: culture/microscopy
- Treatment: oral for invasive aspergillosis (high mortality)
Pneumocystis
- common in AIDS patients — major mortality for AIDS patients
- most people exposed in childhood and have dormant cystis in lungs, only become problematic when become immunocompromised
- infection = activation of dormant cysts in lungs — alveoli inflame -> blocks gas exchange
- no person->person spread
- NO ERGOSTEROL
- FATAL if left untreated
- Diagnosis: microscopic examination of lung fluid or tissue
- IMPOSSIBILE TO CULTURE IN CLINICAL LABS
- Treatment: oral; limited
