BioSci Exam 3: Mycology and parasitology (quiz 5)

fungi structure

organelles like animal cells

not motile

cell wall is chitin and B-glucan

cell membrane with sterols (ergosterol)

fungi drug targets

chitin and b-glucan in cell wall

(not susceptible to antibiotics targeting peptidoglycan)

ergosterol in cell membrane

cell wall in fungi vs animal cells

ergosterol instead of cholesterol

*drug target

types of fungi

yeast, mold, dimorphic

yeasts vs. molds

yeast: single cells that reproduce by sexual budding

mold: multicellular, long filaments (hyphae) forming a mat (mycelium)

dimorphic fungi

form both yeasts and molds

thermally dimorphic

ambient - mild

human body temp - yeast

fungi metabolism

obligate aerobes (some facultative anaerobes & fermenters to make ethanol - no obligate anaerobes)

all required organic sources of carbon (like decaying matter)

where can you find fungi?

environment - usually soil

many worldwide (some specific)

Candida albicans is an exception - in normal human flora

fungi replication

asexual: genetically identical offspring from one arent - budding or binary fission

sexual: mating - sexual spores makes gametangia (n) that duplicates to zygote (2n) which differentiates to zygospore

budding

asexual replication in mosts yeast, some molds

weird version of mitosis

daughter cells unequal in size

where is Candida albicans found?

normal human flora - skin, mouth, small intestine, vagina

Unchecked growth - yeast infection (vaginitis, thrush)

dermatophyte growth of candida albicans

inhibited due to fatty acids in skin

if skin is damaged fungi invades tissue and establish itself

respiratory tract fungi

mucous membranes trap inhaled fungal spores and cells that phagocytose fungi

granola formation can wall of fungi so it doesn't spread fruther

mycotoxicosis

where toxins of fungo are ingested

amanita mushrooms

produce toxins that cause hepatotoxicity (mycotoxicosis)

calviceps purpurea

produces alkaloids (LSD) when on grains which cause ergotism - pronounced vascular and neurologic effects

aspergillus flavus

makes aflatoxins that cause liver damage and tumors (hepatic carcinoma) because it causes p53 mutations

allergies to fungi

spores from aspergillum lead to asthmatic reactions

systemic reactions to drugs made from penicillin mold

diagnosing fungal infections

direct microscopic examination

fungal cultures (inhibit bacterial growth so you can see fungus)

PCR tests

serologic tests to detect antibody in systemic mycoses

antigen latex agglutination test for cryptococcal capsular antigens (CRAG test)

complement fixation tests

CRAG test

antigen latex agglutination tests for cryptococcal capsular antigens

microscopic diagnosis of fungi

visualization of spores or hyphae with special stains (like India ink)

10% potassium hydroxide to dissolve tissue but keep alkali-resistant fungi intact (candida)

anti fungal drug targets

cell wall chitin or b-glucan synthesis

cell membrane ergosterol synthesis

disrupting cell membrane

mitotic spindles

DNA synthesis

Nikkomycin

newer anti fungal targeting cell wall chitin synthesis

echinocandins

anti fungal targeting b-glucan synthesis

azoles and terbinafine

anti fungal targeting cell membrane ergosterol synthesis

oral azaleas can decrease gonadal steroid production

terbinafine is toxic so topical use mostly (same with nystatin)

amphotericin B and nystatin

disrupts fungal cell membrane

causes renal toxicity

griseofulvin

anti fungal drug targeting griseofulvin

causes liver toxicity

flucytosine

anti fungal targeting DNA synthesis

anti fungal toxicity

toxic to our cells because of similars

which antifungals are well tolerated?

fungal cell wall b-glucan inhibitions (echinocandins) because there is no similarity to our cells

candida albicans

opportunistic pathogen that is part of normal flora

oval yeasts that can form hyphae

no vaccine

Candida albicans: virulence factors

resistant to anti fungal azoles

Candida albicans: transmission & causes

transmission: yeast already on skin, GI, and vagina; can enter blood via IVDU and IV catheters from skin; enter urinary tract via urinary catheter

causes vaginitis, thrush, diaper rash, intertrigo

Chronic mucocutaneous candidiasis (immunocompromised)

disseminated infections (lead to endocarditis, candidemia, endophthalmitiis)

Candida albicans skin invasion

warm, moist areas

itchy, painful, erythematous (beefy red) and weeping

finger nail thickening and loss (frequent dish washing)

candida auris

opportunistic pathogen in normal flora that can cause outbreaks in healthcare facility - nosocomial spread

killed with alcohol based sanitizers and bleach

no vaccine

causes infection in immunocompromised; bloodstream infections 50%; high mortality

candida auris: virulence factors

multidrug resistent to fluconazole, other azaleas, amphotericin B and some echinocandins

pan-resistant strains

what causes dermatophytoses?

dermatophyte fungi (trichophyton, epidermophytan and microsporum genera)

note: can see hyphae with 10% KOH under microscopy

what causes tinea versicolor?

malassezia

dermatophytoses tranmission

direct contact - causes "tineas"

microsporum can spread from cats and dogs

infect only superficial keratinized structures usually in warm, humid areas

no vaccine

cryptococcus neofromans

opportunistic pathogen

oval, budding yeast surrounded by wide polysaccharide capsule

cryptococcus neofromans: modes of transmission

inhalation

yeast found in soil contaminated by bird feces inhaled into lungs (bird is carrier, not infected)

causes meningitis, brain infections, pneumonia

aspergillus fumigatus

opportunistic

widely distributed; decaying vegetation

only exists as molds (conidia)

aspergillus fumigatus tranmission

inhalation of airborne conidia - infect skin, eyes, ears, sinuses, other organs

no vax

causes fungus ball and allergic bronchopolmonary asperigillosis; brain abscesses in immunocompromised

most common cause of fungal sinusitis?

aspergillus fumigatus

coccidioides

coccidioides immitis and c. posadasii

in soil and endemic in southwest US and latin America

very light arthrospores carried by wind

transmitted when inhaled, infect lungs causing infection

histoplasmosis capsulatum

opportunistic

dimorphic fungi (mold in soil; yeast in tissue)

endemic in central and eastern US

inhalation of spores; in soil contaminated by bird feces

bats can infect and excrete into guano

histoplasmosis capsulatum: virulence factors

survive phagolysosome by producing alkaline substances like bicarbonate ammonia to inactivate enzymes

histoplasmosis

causes lung infection and dissemination infections

erythema nodosum: sign that cell-mediated immunity is active and infection can be controlled

mostly asymptomatic

blastomyces dermatitidis

soil, endemic mainly in north america

dimorphic fungi

inhalation of conidia spores -> transmission

causes blastomycosis

pneumocystitis jiroveci

opportunistic pathogen

fungus classification but antifungals don't work (use TMP-SMX or anitparasitics); has aspects of protozoans - cyst appearance in tissue; cholesterol in cell membrane

inhalation transmission

no vaccine

pneumocystitis jiroveci virulence factors

major surface glycoprotein - significant antigenic variation due to gene rearrangement

causes pneumonia deadly in immunocompromised (especially AIDS)

fungal infection dissemination in general

severe - can be fatal

protista cell structure

flexible cell membrane

cyst part of life cycle can have cell wall

organelles - specialized for anaerobic respiration

cytosine - cell mouth

some don't have Golgi

contractile vacuole

in protista

maintain osmotic gradient in water

protista motility

motile or not

flagella (kinetochore), cilia, pseudopodia

types of protista

single celled protozoa

multicellular metazoan - helminths or worms

single celled protozoa

sarcodina: amebas

sporozoa: sporozoans like malaria-causing plasmodium

mastigophoran: flagellates like giardia

ciliata: ciliates like paramecium

multicellular metazoan

platylheminths: flatworms

cestoda: tapeworms

trematoda: flukes

nemathelminths: roundworms and nematodes

free living vs parasitic protista

free living live in more unstable environments

parasitic form is in stable environment

free living protista

encyst to avoid environment fluctuations

secrete thick, tough wall around themselves

quiescent state

carried by environment

lose flagella, cilia, contractile vacuole, food vacuole

excyst during favorable conditions - like in body

protista metabolism

obligate aerobes or anaerobes

protista life stages

trophozoite (larva/adult) and cyst (egg) stages

trophozoite

larva/adult stage

motile, feeding, reproducing form surrounded by flexible membrane; larval form differentiate into adult form and produces egg or cyst

cyst form

non-motile, non-metabolizing, non-reproducing

survive well,

transmission

differentiate into larval form or trophozoite

types of protista hosts

definitive - sexual cycle occurs or adult is present

intermediate - asexual cycle occurs or larva is present

transmission prevention between hosts

prevent intermediate hosts from ingesting eggs that were passed by definitive host

or

prevent reproduction of parasite in definitive host to prevent disease

parasite transmission

ingestion of contaminated food.water containing cysts

ingestion of cysts on unwashed fingers

via insect vectors such as ticks, flies or mosquitos

penetration of skin with larvae

sexually transmitted

do I need to know which species for each of these?

diagnosis of parasitic infection

microscopy (giemsa stain to look at parasite; blood smear to see infected cells)

stool test for egg or larvae presents using microscopy

can see large parasites on CT scans

PCR or ELISA for parasite antigens or immunofluorescence

eosinophilia and elevated IgE

parasite prevention

insect repellents, protective clothing, modify environment, cooking properly, water treatment and filtration, good hand hygiene

chemoprophylaxis to prevent disease with anti-malarial drugs

parasite treatment

anti parasitic, antihelminthic, antimalarial or antiprotozoal drugs that target components of cellular metabolism or transport or block DNA or protein synthesis

paralyze metazoans and ectoparasites by messing with nerve and muscle function

surgical excision of large parasites

entamoeba histolytic

+virulence, transmission

trophozoite (1 nucleus; can ingest RBC) and cyst (4 nuclei)

tropical areas

fecal-oral route

no animal reservoir

virulence: trophozoites secrete enzymes causing local necrosis of colonic epithelium

granulomatous lesions: ameba (look like adenocarcinomas)

giardia lamblia

trophozoite & cyst stages

fecal-oral transmission

anal-oral transmission

human and mammal reservoirs

cryptosporidium hominis

sporozoites, trophozoites, merits, merozoites, microgametocytes, macrogametocytes, microgamete

fecal-oral tranmission

cattle reservoir

trichomonas vaginalis

motile trophozoite (NO cyst form)

sexual contact transmission

only sexually transmitted parasite discussed

trichomonas vaginalis

green discharge

malaria is caused by

Plasmodium: p. falciparum, p. vivid, p. ovale, p. malariae

plasmodium transmission

mosquito vector

definition host: anopheles mosquito (feeds at night)

humans are intermediate hosts

transmission across pallets, blood transfusions and IVDU

merozoites

part of Malaria life cycle

schizonts in exo-erythrocytic life cycle produce merozoites that lyse hepatocytes

erythrocytic cycle inside RBCs: merozoites -> ring shaped tophozoites

what causes malaria symptoms?

periodic release of merozoites from RBCs causing hemolytic anemia

(spleen enlargement and can get hepatomegaly also)

malaria virulence factors

p. falciparum has chloroquine resistance

babes microti

sporozoan

trophozoite stage (no cysts)

transmitted via tick vector

mammal reservoirs

humans are dead-end hosts

life cycle: sporogonic and erythrocytic

toxoplasmosis gondii: life cycle

sporozoan with 2 life cycle stages: motile trophozoite and nonmotile cyst

definitive host: domestic cat, other felines

humans/mammals are intermediate hosts

toxoplasmosis gondii - how to kill

cysts can be killed by iodine or boiling and removed by filtration (chlorination does not kill it)

toxoplasmosis gondii: modes of transmission

ingestion of cysts

transplacental transmission of trophozoites from infected mother to fetus

definitive host: cat

cat ingests cyst containing bradyzoites from raw meat (mice)

bradyzoites infect mucosal cells in small intestine -> male and female gametocytes which fuse to form oocysts and are excreted in cat feces

humans and mammals intermediate hosts (ingest undercooked meat; liter box cleaning .... more info on this - check LOs

more on toxo

brain eating amoebas

acanthamoeba castellani; naegleria fowleri

free living in warm freshwater lakes and soil

trophozoite and cyst stages (cysts not killed by chlorine)

brain eating amoebas: acanthamoeba castellani; naegleria fowleri - transmission

acanthamoeba enters skin or eyes due to trauma

naegleria enters body through mucous membranes while swimming - penetrates nasal mucosa and cribriform plate to enter brain (often children)

causes meningoencephalitis

taenia

helminths

t. solium -> taeniasis and cysticercosis

t. saginata -> taeniasis

flat or tapeworms - rounded head, flat segmented body

eggs excreted in feces and ingested by intermediate hosts (t. saginata cattle; t. sodium pigs)

taenia virulence factors

scolex attaches to intestinal wall with suckers hooks or sucking grooves

taenia hosts

humans are definitive hosts that ingest larvae/cysticerci in undercooked meat

cysticerci attach to small intestine wall via scolex -> adult worms

eggs passed into feces - accidentally eaten by pigs or cows

eggs in intestine burrow into blood vessels and skeletal muscle

schistosom

helminth

blood flukes - s. mansion, japonica, haematobium

separate sexes live attached to each other - female goes into male schist/groove

schistosom - transmission

penetration of skin by free swimming cercariae

intermediate host - snail (asexual cycle)

eggs excreted by definitive host hatch in fresh water

cercariae released by snails in fresh water penetrate human skin (definitive host of sexual cycle)

schistosom virulence factors

surface gets coated with host antigen so immune system cannot recognize them as foreign

pinworms: enterobius vermicularis

nematodes or round worms with complete digestive tract (females are large; male has coiled tail)

2 larval forms: rhabditiform are noninfectious and feeding while filariform are infectious

pinworms tranmission & virulence

ingestion of eggs

body covered in noncellular highly resistant coating or cuticle

lice

arthropod insects with chitinous exoskeleton

pedicures humans - elongated; infect hair

phthirus pubis - crab looking; causes crabs

nits: eggs

lice transmission

via fomites or direct contact

head lice: hats, combs, towels

body lice: clothing or personal contact - leave clothing when they need blood meals

pubic: sexual contact

lice virulence

resistance to permethrin is increasing

bedbugs

arthropod insects

cimix lectularius

transmitted via contact with bedding