Module 7 Wk 4 Flashcards
T/F fungi have undefined nuclei?
Flase - They have a defined nuclei
What types of repro does fungi do?
sexual and asexual
Where do you not see sexual reproduction of fungi?
Infection in animals and humans
What is the infectious form of fungi?
Asexual spores
What do we target within fungi cell wall?
Glucan synthesis
Where will you see most fungi infections?
Cutaneous and superficial mucous membranes
What are benificial fungla products?
Antibiotics
What are harmful fugal products?
mycotoxins
Why would you not feed fungal products to pregnant cows especially?
Can cause fungal abortions
When in the lab making a diagnosis what can you do?
- direct microscopy
- Culture
- histology of tissue effected by invasive disease
How do yeast reproduce?
By budding
Where do yeasts grow?
Skin, mucous surfaces and in the body
What kind of infection do yeasts cause?
Superficial
What are moulds?
Multicellular organisms that produce hyphae and mycelium and spores
What are dimorphic fungi?
Organisms that can produce both hyphae and yeast
What can result from yeast daughter cells not detaching themselves?
Pseudohyphae
In catt;e what can the yeast Candida Albicans cause clinically?
- Mycotic abortions
- Ruminal infections
- Mastitis
What would you see Candida albicans cause in pigs?
Dermatitis
What would you see Candida albicans cause in dogs?
- Chronic enteritis and dermatitis
- Vaginitis
What would you see Candida albicans cause in Birds?
- Crop infections
- enteritis
What shap do Malassezias apear like?
bottle shaped
What enchances Malassezia growth?
Lipase
How would you become infected with Cryptococcus?
Inhalation of yeast cells
what are moulds?
Molds are multinucleated, filamentous fungi composed of hyphae
What is the difference between septate and non-septate hyphae?
Septate have walls between cells and non septate dont
What kind of branching do dermatophytes have?
Sepate branching hyphae
What kind of spreading do dermatophytes have?
- Anthropophilic (human to human)
- Geophilic (enviro to animal)
- zoophilic (animal to human)
What do dermatophytes infect?
Skin, hair and nails
What is used in the lab to detect Dermatophytes?
- micoconidia and macroconidia
what are the two genus of dermatophytes?
microsporum and trichophyton
How can you detect ringworm?
- fluresce under uv light
- culture
T/f ringworm in cats and dogs is zoonotic?
True
What genus of dermatophyte causes ring worm?
microsporum
What is the difference between ectothrix and endothrix
Dermatophyte infections in which arthrospores are formed on the outside of the hair shaft are known as ectothrix infections and those in which the spores develop within the hair itself are known as endothrix infections.
Is M.canis ecto or endo?
ectothrix as grows on the hair
What is the name of the micro sporum species that geophillically effects dogs?
M. gypseum
T/F trichophytons are zoophilic?
Trueeee bitch
What shape are the macrocondia in trichophyton?
Club
What is the species of trichophyton that is cattle ringworm which is transmissible to man?
T. verrucosum
Is T. verr ecto or endothrix?
Ectothrix
What is the species of trichophyton that effects horse and dog and which one just effects horse?
- T. mentagrophytes effects both
- T. equinum just horse
Are Aspergillus sepate or non speate hyphae?
sepate branching hyphae
what do aspergillus fumigatus spores infect?
Young non-immune or immunosupressed animals
What does aspergillus disease mainly cause?
resp infection as you inhale spores
Describe the host defences against Aspergillus?
- neutrophils swell and germinate in to hyphae
- Invade into lung
- Into blood vessels (angioinvasive) neutophils will kill them
- They don’t infect no immune as macrophages in lung get rid
what are the two distinct forms of dimorphic fungi?
mould in enviro and yeast in animal tissue
in dimorphic fungi which form is pathogenic?
yeast
How do the spores from the dimorphic fungi enter host?
inhalation
T/F the Histoplasma capsulatum farcinimosum dimorphic fungi is notifible?
Trueeee
what is selective toxicity of antifungal agents and how does it work?
where we destroy the fungus but cause no or minimal damage to the animal
to do this we need to target features of the fungus not found in host
What do allyamines inhibit within fungal
Inhibits Squalene turning into lanosterol
What inhibits lanosterol from being engosterol?
azoles
What kind of damage and wher do amphotercins have effect?
pores in cell membrane and oxidative damage?
What are the 5 classifications of antifungal drugs?
Superficial/Systemic infection
Topical/Systemic administration of drug
Antifungals/ Synthetic agents
Fungicidal/Fungistatic
Chemical Subclass
Whats the difference between fungicidal and fungistatic?
Fungicidal = fungi is killed by drug
Fungistatic - fungis is inhibited by drug
What 3 drug classes target ergosterol in the fungal cell membrane?
- allyamines
-azoles
-amphtericin B
Describe the biosynthessi of ergosterol?
Acetyl CoA - squalene - lanosterol - ergosterol
What is allyamines mechanism of action?
inhibits ergosterol biosynthesis via inhibition of squalene epoxidase (fungicidal)
T/F allyamines can only darget dermatophyte infection only?
True
Is there side effects of using allyamines?
could have very genral and mild GIT and skin ones
What routes is there for allyamines?
Oral and topically
in terms of pharmacokenetics what is importnat about allyamines?
highly lipophilic so persists in skin
What are the two types of azoles?
imidazoles - topical
triazoles - systemic
What are examples of imidazoles?
Clotrimazole; Enilconazole, Miconazole
What is the main use of imidazoles?
For superficail mucous membrane and skin infection
What are Imidazoles meachnism of action?
inbibition of cytP450-dependent 14-sterol de-methylase
Do imidazoles have a broad spectrum?
Yes
what are side effects of imidazoles?
GIT; anorexia; hepatotoxicity; suppression of steroid production (ketoconazole); teratogenic
What are triazoles for?
Used for serious systemic mycoses
what are examples of triazoles?
fluconazole, itraconazole, voriconazole, and posaconazole
What route do triazoles use?
oral
What is intraconazole drug of choice for?
Histoplasmosis (lung infection)
what are the mechanisms of resistance to azole antifungal drugs?
Membrane changes lead to reduced drug up-take
Mutation of the target enzyme
Over production of the target enzyme
Modification of the ergosterol biosynthesis pathway
Drug efflux due to up-regulation ABC transporters, MFS transporters
Biofilm formation
What are two examples of Polyenes?
Amphotericin B, Nystatin
what is the mechanism of action of polyenes?
They bind to ergosterol, distrupting osmotic integrity of the membrane by forming pores where ions leak from cell causing cidal and oxidative damage
describe the pharmacokenetics of polyenes?
poorly water soluble (amphotericin B
is forms a colloid in solution for injection), poor absorption from GIT
What are the meachnisms of resistance to polyenes relate too?
It is linked to reduced ergosterol in fungal cell membrane
What does inhibition of the enzyme that is involved in glycan synthesis cause?
Fungal cell wall falls apart
What are glucan synthesis inhibitors called?
echinocandins
what are examples of echinocandins?
Caspofungin; Anidulafungin, Micafungin
what is the mechanism of action of echinocandins?
block synthesis of Beta (1,3) glucan
what route would you use with echinocadins?
IV
what are the mechanisms of resistance against echinocandins?
Inhibit glucan synthase which synthesizes beta glucan, a structural component of fungal cell walls
Structural integrity lost – cidal in yeast, static in moulds
Many moulds resistant (not Aspergillus) most Candida species susceptible
Candida parapsilosis innately less susceptible – higher breakpoints
Various FKS1 (glucan synthase subunit) mutations identified also FKS2 and 3 genes all of which encode the target enzyme and up-regulation of chitin synthesis - rescue mechanism
what is Flucytosine an example of?
Antimetabolite
what is the mechnanism of action of an antimetabolite?
Incorporation of 5-FU into RNA disrupts protein synthesis (fungicidal) and further conversion of 5-FU to fluorodeoxyuridine monophosphate inhibits thymidylate synthase which interferes with DNA synthesis
what route would you use to give an antimetabolite?
oral
what is the pharmocokenetics of antimetabolite?
excreted unchnaged by the kidney
Describe the Mechanism of resistance to flucytosine
Sensitive – cascade of active enzymes, cytosine permease to take up the drug, cytosine deaminase and phosphorylase to metabolize it to its toxic form – disrupts RNA and DNA synthesis
5-FC converted to 5-FU – Fluorouracil – miscoded RNA or DNA
Loss or reduction in activity in any of the enzymes (but most commonly the phosphorylase) leads to primary emergent resistance
Common during treatment – rarely used as monotherapy, always combined with AmB