mycology-2011: general features - university of prince...
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*Mycology-2011: General Features
*kingdom FUNgi (~ 400 pathogenic species)
* Eukaryotic, nonphotosynthetic,
* filamentous or unicellular
*Rarely Epidemic (ie. Contagious)
* Exception (Dermatophytes) - zoonotic
* Endemic – Yeast, Dimorphic fungi – saprozoonotic
* Predisposing factors
* environment load, immune status, prolonged Abx
*Asexual reproduction
*spore structures impt. Dx tools
*Unique Cell Envelopes : Ergosterol
* 80-90% CHO (chitin, mannan, -glucans)
* Aerial/Vegetative hyphae – filaments (mold phase)
* Aseptate hyphae – Rhizopus or Mucor spp.
* Pseudohyphae - Candida albicans (yeast)
* Septate hyphae – most ie. Aspergillus spp.
* Conidia – spores (used interchangeably)
* See next slide for overview
* Dimorphic – mold-like and yeast-like phases
*Mycoses (us) and mycotoxicoses
* ‘Philics – Anthropo-, Geo-, Zoo-
* Rhizoid – root like structure (Rhzopus spp.)
* Sporangium – closed sac-like structure (sporangiospores)
* Yeast: Unicellular (budding)
Rhizopus
* Some Terminology
C. albicans
Malassezia
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Dermatophyte macroconidia
Endospores
*Asexual Spore Structures
*Arthroconidia
*Dermatophytes, Coccidioides
*Blastoconida
* Budding (yeast), hyphae
*Chlamydoconidia
*Histoplasma sp., Candida
*Endospores
*Coccidioides (spherule)
*Macro- and Microconidia
*Dermatophytes
*Phialoconidia
*Aspergillus spp.
*Sporangiospores
*aseptate fungi Rhizopus, Mucor
Histoplasma
Tuberculate
chlamydoconidia
Aspergillus
Sporangiospores
arthroconidia
*General Diagnostic Lab Procedures
*Sabourauds Media (culture temp. 22 - 25 oC)
*pH 5.6 inhibits bacteria
*Abx (Chloramphenicol), +/- Cycloheximide
*BA (Brain Heart Infusion Agar or Phytone Yeast Extract)
*Scotch Tape Mount - Lactophenol Cotton Blue (LPCB)
*10 - 20% KOH wet mount, India-ink (Cryptococcus)
*Histological Stains:
*PAS (Periodic Acid Schiff) – stain red
*Methenamine Silver – stain brown or black
*H+Eosin (Histoplasma)
*Pan-fungal PCR (18s – 28 s rDNA) + sequencing
*MALDI-TOF mass spec
India ink
PAS
Methenamine silver
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*Antifungals – Ergosterol Inhibitors
*Polyenes (Fungicidal/static) – binds ergosterol
*Nystatin - mucocutaneous candidiasis (C. albicans)
*Amphotericin B - yeast, dimorphics (nephro/cardiotoxicity)
* dogs/cats, horses – i.v. only
* Imidazoles and Triazoles (Fungistatic/cidal) Topical/p.o.
* Block ergosterol synthesis
* IMIDAZOLES - Ketoconazole (KTZ), Miconazole (MCZ), Clotrimazole (CTZ)
*TRIAZOLES - wider spectrum of activity, fewer side effects
* Enilconazole (ECZ ) – label use in dogs and horses (topical)
* Itraconazole (ITZ) – label use cats, Fluconazole (FCZ)
* Voriconazole (VCZ) – ELDU, $$ but (aspergillosis in companion birds).
*Antifungals
*Allylamine Antifungals - block ergosterol synthesis
* Terbinafine (dogs/cats) – oral (dermatophytes)
* Flucytosine (5-fluorocytosine) typically with AMB or FCZ
* antineoplastic agent (not at antifungal doses)
* Indirectly inhibits DNA, protein synthesis (mRNA alteration)
* Yeasts, Sporothrix schenckii in dogs/cats
* Griseofulvin (Penicillium griseofulvin) – oral (dogs/cats/horses, cattle)
* Inhibits microtubule assembly (mitosis compromised)
* Systemic for Dermatophytes ; Accumulates in keratin, teratogenic
* Iodides (Na or K)
* Txt for Sporothrix schenckii in horses
*Echinocandins - block glucan synthesis – “penicillin of Antifungals”
* Caspofungin (Merck) – ELDU parenteral for Candidemia, invasive aspergillosis (dog/cat)
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Fungal Cell Envelope and Antifungals
Erg Erg
1,3-β glucan synthase
1,6-β glucan
Chitin
Echinocandins (Capsofungin)
‘Azoles (ITZ)
Allylamine (Terbinafine)
1,3-β glucan
Lanosterol
Polyenes (AMB)
Squalene
Mannoproteins
= Ergosterol
I. Opportunistic Mycoses:
- Candidiasis, Aspergillosis, Zygomycosis
II. Cutaneous and Subcutaneous Mycoses:
- Dermatophytes, Malassezia, Sporothrix
III. Systemic Mycoses:
- Cryptococcosis, Histoplasmosis, Blastomycosis and Coccidioidomycosis
IV. Fungal –like pathogens: an Algae, Mycotic Swamp Cancer …
*The Fungal Pathogens
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*Opportunistic Mycoses: Candida albicans
*Candidiasis : Predisposing factors: Prolonged Abx, immunodeficiency
*Mycotic Stomatitis - (Dogs and cats)
*whitish-grey oral plaques (pseudomembranous and ulcerative)
*Crop Mycosis (Sour Crop or Thrush)
*Risk factor Abx in feed
* young poultry, companion birds
* can be significant economically
* pseudomembranous plaques - oral cavity, oesophagus, crop
*Txt Nystatin/VitA in feed, CuSO4 (water)
*Mastitis in dairy cattle
*C. albicans, krusei – unhygenic practices
*Candida spp.: Dx/Txt
*Direct examination impt. material
*KOH wet mount or Gram stain
*Pseudohyphae, yeast (3-10 m)
*BA (Yes but no)
*CHROMagar Candida (BBL ™)
* selective + chromogenic differentiation
*Germ tube (pseudohyphae) test easy
*Commercial ID available (API –Yeast)
*PCR, MALDI-TOF ms
*Nystatin (topical): oral mucosal I.U.(metritis),
*Miconazole cream, topical AMB
*Systemic infections – rare (ITZ)
C. albicans C. krusei
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*Aspergillosis
*A. fumigatus : Inhalation/ingestion of spores (poor hay/silage)
*Brooder pneumonia in chicks (contaminated litter)
*Guttural Pouch Mycosis , pneumonia and keratomycosis in horses
*Unilateral, internal carotid erosion,
*Epistaxis, mucopurulent nasal discharge, dysphagia/laryngeal paralysis, head position
*Nasal Aspergillosis in Dogs
* serosanguinous nasal discharge, epistaxis
*ulceration external nares
* turbinate destruction,
*Trivia: German shepherds A. terreus
*Abortion in cattle, horses – following Aspergillemia
*Pneumonia (high mortality), UTI, enteritis (foals/calves)
*Aspergillus: Dx/Txt
*Direct smear (KOH) - deep scrapings/tissue (stringency)
* Septate, dichotomous branching
* conidial heads only when O2 available
* ie. lungs, nasal sinus, culture plates
*Dogs/Horses – radiology (neoplasia) and/or rhinoscopy
*SAB, Colony characteristics, LPCB
* Intervention
* Sx for Canine/Equine Infections (nasal, guttural pouch)
* ITZ (p.o.), ECZ instilled nasally (dogs and horses)
*Voriconazole – companion birds
*Management (poultry, ruminants, horses)
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*Phylum Zygomycota: Zygomycoses
*Aseptate fungi - Rhizopus, Mucor and Mortierella
* Inhalation/ingestion/cutaneous puncture
* localized granulomatous lesions – systemic
*Angiotrophic – hematogenous dissemination
*Cattle
*Abortion, pneumonia, Less commonly enteritis, rumenitis, lymphadenitis
(mediastinal/mesenteric)
*Mycotic Abortion (Mortierella wolfii – cattle) – 1st Canadian case (CVJ,
51:2010) – unusual abortion – brain – pneumoniae and kidney
*Swine - mediastinal lymphadenitis, enteritis (piglets), gastric ulcers
*Rarely:
*Dogs - enteritis
*Cats – necrotizing pneumonia, enteritis
*Horses, sheep, mink, guinea pigs, mice
*Zygomycetes: Dx/Txt
*Direct examination – aseptate, wide
(5-15 m) hyphae
*Lesion, histological/microscopic
characteristics
*Culture (SAB) easy for most –
establishing cause impt.
*Colony morphology, LPCB
*aseptate, sporangia
*Rhizoids
*Nodal – Rhizopus
*Anodal - Mucor
*Txt – feed quality
Methenamine silver
+ light green counterstain
Mucor