Mycology revision Flashcards by Tassabeeh Abdalaziz

Fungi with Intrinsic resistance to Amphotericin B?

Chromoblastomycosis
Aspergillus terreus
Candida lusitani
Scedosporium spp
Some Fusarium spp

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Fungi which are intrinsically resistant to Fluconazole

Candida krusei
Candida glabrata (some isolates) Candida norvegensis
Candida inconspicua
Trichosporon asahii

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Fungi which are intrinsically resistant to Echinocandins

Cryptococcus neoformans
Trichosporon asahii

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which Aspergillus is resistant to Amphotericin B ?

Aspergillus terreus

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Mechanism of Amphotericin B ?

binds to ergosterol and disrupts cell membrane causing the formation of channels through which ions can leak leading to cell death.
-Oxidative damage to the cell membrane also occurs.

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What are the main criteria of Candida tropicalis ?

It is the most virulent after C albicans
-It is a common coloniser of humans, especially in the tropics.
It can develop fluconazole resistance quickly.
Broad spectrum azole (voriconazole), candins or amB can be used to treat this Candida.
It may produce coloured colonies (red/pink/orange).
It produces pseudohyphae.

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What are the virulance factors of Candida glabrata ??

1-Can produces a biofilm of protein and carbohydrates, which contributes to resistance.

2-Adhesins

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What are the main criteria of candida glabrata?

2nd commonest type of Candida pathoge
It is a human commensal
Phylogenetically closed to saccharomyces and then C albicans.
-Virulance: biofilm & adhesins
-Intrinsically less susceptible to fluconazole (SDD)
-AmpB has delayed killing against this sp.
-It does not produce any hyphae and produces small roundish yeast cells.

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T/F : Candida glabrata is intrinsically R to Fluconazole?

It is intrinsically less susceptible to fluconazole (but not R like C krusei)

Fluconazole can be reported as susceptible dose-dependent (SDD).

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T/F:
AmpB has delayed killing against Candida glabrata and krusei?

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What is the new name of Candida glabrata?

Nakaseomyces glabratus

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What is the new name of candida Krusei?

Pichia kudriavzevii

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What are the main criteria of Candida krusei?

It is common in haemato-oncology patients
It is intrinsically resistant to fluconazole, but not voriconazole.
AmpB has delayed killing against this sp.
It is also common in eastern European countries.
-It is used in chocolate production
It produces a rough/matte spreading colony on SAB (unlike other Candida that produces dome-shaped colonies)
on microscope: “long grain rice” appearance

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What is the new name of Candida auris?

Candidozyma auris

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What are teh general criteria of
Candida lusitaniae?

Emerging opportunistic pathogen
It produces biofilm and adhesins.
It produces pseudohyphae.
It is often resistant or has high MIC to amphotericin B.

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What is the new name of candida lusitaniae ?

Clavispora lusitaniae

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What are the risk factors of candida parapsilosis infection?

1-Neonates
2-Critical care settings
3-Prostheses & Indwelling catheters
4-parenteral feeding (important)

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Common criteria of candida parapsilosis?

-It is a common human commensal
-Oval, round, or cylindrical shape yeast
-Can produces biofilm
-It forms pseudohyphae

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Common features of candida dubliniensis?

-Closely related to C albicans and often misidentified.
-Unlike C. albicans, isolates of C. dubliniensis grow poorly or not at all at 42°C

-Has been linked to oral candidiasis in AIDS patients, but it is not diagnostic of AIDS.

-It can develop fluconazole resistance in vitro.

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What are the Candida spp virulence factors?

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1-Extra cellular matrix
2-Ability to convert to hyphal forms
3-Acid proteases

Risk factors for VVC

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Recent antibiotic use
Diabetes mellitus Immunosuppression
Obesity
Pregnancy
Oral contraceptive use.

Treatment optios for Symptomatic candidurea with Fluconazole R isolates?

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Cystitis: Amphotericin B deoxycholate ± flucytosine for 7 days

Management of fungal prostate abscess ?

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Drainage

#Antifungals for 4 weeks (preferably fluconazole, alternative Amphotericin B or echinocandins)

Antifungals achieving therapeutic renal concentrations include

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1-Amphotericin B deoxycholate
2-Fluconazole
3-Flucytosine

T/F: Voriconazole, posaconazole, and isavuconazole do not achieve adequate urinary concentrations??

Antifungal prophylaxis in patient with upper GI perforation?

#Fluconazole loading dose 12 mg/kg on day 1 followed by 6 mg/kg once daily #If Fluconazole cannot be given/local flora has high-level Fluconazole Resistant: -Caspofungin 70 mg loading dose followed by 50 mg OD or -Anidulafungin 200 mg loading dose followed by 100 mg OD or -Micafungin 100 mg OD

What are the 6 genetic clades of Candida auris?

Clade I (Southern Asia) Clade II (East Asia) Clade III (South Africa) Clade IV (South America) Clade V (Iran) Clade VI (Singapore)

Candida auris can be mis-identified as ..??

Candida haemulonii

What antibiotic class that predispose to candida auris infection?

Tetracycline minocycline tigecycline

Why it is unlikely for c auris to colonise the oral and esophageal mucosa?

Due to the salivary antimicrobial peptide histatin 5

Virulance factors of C auris?

1-Can tolerant high temperatures (42C) &high salt concentrations 2-biofilms formation 3-Saps and lipases - degrade host tissues 4-Morphological transformation 5-Antifungal resistence

What is the meaning of candida auris Saps?

Secreted Aspartic Proteinases

What are the mechanisms of R to Azole antifungals in C auris?

1-Mutation in ERG11 (ERG11 encodes for the lanosterol demethylase – the target of azole class) 2-MFS efflux pump 3-Upregulated ABC efflux pump

What are the mechanisms of R to echinocandin antifungals in C auris?

Mutation in Fks1 (FKS1 encodes the catalytic subunit of 1,3-beta-D-glucan synthase that is critical for cell wall synthesis)

What are the mechanisms of R to Polyenes antifungals in C auris?

Single-nucleotide polymorphisms in multiple loci

What are the 3 Serology test for fungal infections ?

Beta-D-Glucan Galactomannan, mannan Candida albicans germ tube antigen (CAGTA)

What is the B D glucan?

It is 1,3-β-d-glucan (BDG) a polysaccharide a constituent of the cell wall in most fungi

B D Glucan can be used in diagnosing ... ???

Candida, Aspergillus, Fusarium and, Pneumocystis jiroveci.

B D Glucan cannot be used in diagnosing which fungal diseases?

Cryptococcus & Blastomyces dermatitidis - produces low-level BDG or Mucorales (Absidia, Mucor and Rhizopus) do not produces BDG

What is the adult cut off of B D glucan level?

Positive test ≥ 80 pg/mL Indeterminate test 60 to 79 pg/mL Negative test <60 pg/mL

T/F: B D Glucan can be used for monitoring of fungal diseases?

Persist for a long time – cannot useful to monitor treatment.

What is the PPV and NPV of B D Glucan?

It has poor PPV and good NPV (90-95%) good for excluding infection

T/F: B D Glucan result can be affected by Antifungals??

Not affected by antifungal – can be used even on patients on antifungal.

What is the Galactomannan?

polysaccharide antigen that exists primarily in the cell walls of Aspergillus species

T/F: sensitivity of Mannan antigen depend on candida spp?

T It is the highest for C. albicans, followed by C. glabrata and C. tropicalis. It is poor for C parapsilosis and C krusei

what is the Mannan Antigen test?

Mannan (Mn), a carbohydrate, is a major component of the C. albicans cell wall

What are the indications for Candida auris screening?

1-High-risk patients on admission 2-Close contacts of colonised/ infected patients

Environmental cleaning principle for candida auris?

1-Sporicidal disinfectants 2-Hydrogen peroxide, peracetic acid, or chlorine-based 3-Avoid quaternary ammonium compounds

Mycology revision Flashcards

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