Module 7 - Fungi and Protozoa

What are fungi?

eukaryotes, they have membrane bound organelles

What are the two cell forms of fungi?

single celled (yeast) or multicellular (molds, mushrooms)

Macroscopic

mushrooms, puffballs, gill fungi

Microscopic

molds and yeasts (the ones that cause diseases)

Fungal forms

yeast cells, hyphae, dimorphic, pleomorphic

Yeast cells

round/oval shaped, asexual reproduction

Hyphae

long, threadlike cells found in filamentous fungi = molds

Dimorphic

some can take either form

Pleomorphic

can take on many forms

Thermally dimorphic

mold when growing saprophytically, yeast when in animal tissue

Fungal structure

grow in loose associations or colonies, consist of mycelium, septa, spores

Mycelium

woven intertwining mass of hyphae; make up body or colony of a mold

Septa

cross walls that divide hyphae into segments

Spores

fungal reproductive bodies

Fungi cell envelope

have cell walls containing chitin, a polysaccharide

Fungal nutrition

heterotrophic: saprobes or parasites

Asexual fungal reproduction

cloning: haploid stage, growth of existing hyphae, fragmentation (separated pieces of mycelium forms new colony), spore formation

Sexual fungal reproduction

breif diploid stage: spore formation

Fungal observations

• spores & spore forming structures

• hyphal type

• colony texture, pigmentation

• physiology, genetic makeup

Mycoses

fungal infection

Primary mycoses

fungal infection that sickens healthy people

Opportunistic mycoses

fugal infections that sicken those who are weakened, especially systemic infections

Disease mechanisms of fungi

• allergic responses

• mycotoxins

• mycoces: superficial, subcutaneous, and systemic

Mycotoxins

some cause disease others death, an example is aflatoxins

Aflatoxins

poisonous carcinogens, 2 mold species, found in improperly stored staple commodities, substantial problem in Africa

Superficial mycoces

colonize hair, skin, and nails only infect surface layers

Candida albicans

• normal gut flora, nosocomial

• pleomorphic- outside (yeast), inside (mold)

• candidiasis: thrush, vaginal yeast infection, diaper rash, blood infection in hospitals (catheters, antibiotics, weakened immunity)

Trichophyton spp.

• contact with spores: direct or indirect

• mold which is keratinophilic: feeds on keratin in hair, nails, and skin

• causes dermatophytosis: 3 types

Dermatophytosis

athlete’s foot, ringworm, jock itch

Athlete’s foot

tinea pedis, locker room floors, shower

Ringworm

tinea corpis, sharing of clothing/sheets, barefoot in locker rooms, beach

Jock itch

tinea cruris, often spread from athlete’s foot

Subcutaneous mycoces

colonize deeper layers of skin, usually from implantation into skin through trauma

Sporothrix schenckii

• contact with spores: must enter skin

• thermally dimorphic

• sporotrichosis, rose gardener’s disease

Fonseacaea pedrosoi

• implantation of spores: thorns or splinters

• mold

• chromoblastomycosis: slow growing, warty, cauliflower-like nodules

Systemic mycoces

infection by inhaling spores, fungal growth in internal organs and can cause skin lesions, some primary other opportunistic

Hitsoplasma capsulatum

• breathe in spores: bird & bat poop

• thermally dimorphic

• histoplasmosis: cough, flu-like symptoms, skin/mouth lesions if disseminated

Coccidioides immitis

• soil: disrupted by rain, construction, dust storms

• thermally dimorphic

• coccidioidomycosis or valley fever: subcutaneous lesions, bronchitis or pneumonia, fatigue

Cryptococcus neoformans

• soil contaminated with pigeon/bird droppings

• encapsulated yeast

• cryptococcosis: wound or cutaneous, pulmonary, meningitis

Kingdom Protista

there are 2 sub-groups, algae and protozoa

Protist

unicellular or colonial organism lacking true tissue

Protozoa

single celled; eukaryotic

no cell wall, can have cyst wall

most live in water & soil

Nutritional habitat of protozoa

heterotrophic and require food in complex organic form

free living species: saprobes & grazers

parasitic species: host fluids & tissues

The life cycles of protozoa

trophozoite and cyst, vary from simple to complex

Trophozoite

motile & feeding stage, requires food and moisture

Cyst

dormant, resting stage, hardy

When are cysts formed?

when conditions become unfavorable, like outside of the body

What are cysts important for?

spread of disease, fecal-oral spread

How does protozoa reproduction happen?

reproduction can be asexual, sexual, and both

Pseudopods

false feet, also feeding structures

Flagella

whip like structure, vary in number

Cillia

hair like structures over entire cell surface, used for moving, feeding, and attachment

Amoeba

• pseudopods

• asexual reproduction

• most uninucleate

• most form cysts

• most free-living

Ciliates

• sexual & asexual reproduction

• macro & micro nuclei

• most form cysts

• most are free-living

Flagellates

• flagella or flagella & amoeboid motion

• sexual reproduction

• uninucleated

• form cysts

• most free-living

Sporzoa

• complex life cycles with asexual & sexual stages

• macro & micronuclei

• produce infective spores (haploid)

• all parasitic

Protozoa ID

based on appearance, uses smears of blood & feces

Entamoeba histolytica

• fecal-oral (contaminated produce, water)

• produces cyst

• amoebic dysentery: violent bloody diarrhea - dehydration, fever

• increased sanitation: toilets & hand washing, water filtration: drinking, food prep, ice cubes, vegetable freshening

Naegleria fowleri

• found in warm waters

  • enters nose - nasal tissue - brain

  • bacteria-eating free-living amoeba

• forms cysts

• naegleriasis: primary amoebic meningo-encephalitis

• chlorination helps, keep water out of nose, boil Neti-Pot water

Acanthamoeba ssp.

• soft contact lenses contacting any life cycle stage

  • contaminated lens solution, swimming & bathing, soil

• produces cysts

• Acanthameoba keratitis: cornea infection - blindness

• wear contacts < 12 hr/day, disinfect lenses, replace contact regularly, wash hands before handling contacts, remove contacts before any water activity

Balantidium coli

• zoonotic: fecal-oral from pig (contaminated water)

• produces cyst

• balantidiasis: large intestinal infection - chronic diarrhea, dysentery

• good hygiene, eat only cooked foods, wash fruits & veg

Reservoir host

primary host harboring a pathogen, normally asymptomatic, serves as a source of infection

Biologic vector

any living agent that carriers & transmits an infectious pathogen to another living organism

Trypanosomes

long crescent-shaped cells, single flagellum, in blood during infection, sucking vectors

Trypansoma cruzi

• vector: kissing bugs

  • reservoirs: armadillos, oppossums, raccoons, cats

• no cyst stage

• chagas disease

• avoid sleeping in mud, thatch, or adobe houses; use a bug net, insecticide, insect repellent

Giardia lamblia

• fecal-oral, contaminated water & food

  • reservoirs- dogs, cats, beavers

• cyst producers

• Giardiasis: small intestine dysentery

  • symptoms: none - abdominal discomfort, chronic disease

  • diarrhea is “greasy, voluminous, & malodorous”

  • trophozoite damages microvilli: irritation - mucus (feeding)

• good hygiene, avoid drinking unfiltered stream water, wash fruits & veg, don’t let your dog lick your face

Chagas disease

early: fever, swollen lymph nodes

late: enlarged esophagus & colon or heart failure

Why is diarrhea greasy with giardiasis?

low fatty and carbohydrate digestions, can interfere with vitamin/nutrient absorption (vitamin A vision, vitamin D rickets)

Trichomonas vaginalis

• sexually transmitted

• no cyst stage

• trichomoiasis (trich)

  • women: genital itching, painful urination, premature delivery

  • men: usually asymptomatic

• few sexual partners, condoms

Milaria history

known since antiquity, commonly known in swamps, causative agent search focused on swamp water or air

Milaria

genus Plasmodium, intracellular (RBCs), vector: mosquitoes, most serious species: Plasmodium falciparum

Plasmodium falciparum

• anopheles mosquitos

• falciparum malaria: infected cells lead to microinfarctions (tiny areas of dead tissue) in brain and liver

• most limited to Africa

• control mosquitos and control getting bitten

Symptoms and pathology of falciparum malaria

• fever - death

• paroxysms

• anemia due to loss of red blood cells

• recurrence of paroxysms at periodic intervals

Paroxysms

host inflammatory response in severe chills & fever

Cryptosporidium spp.

• fecal-oral (water)

  • reservoirs: cattle, domestic pets

• produces cysts

• cryptosporidiosis: profuse, watery diarrhea

• wash hands, wash fruits & veg, don’t swallow water: lakes, streams, public pools, minimize contact with young animals

Toxoplasma gondii

• transmission variable

• toxoplasmosis: flu like - latent - brain lesions death

  • congenital toxoplasmosis: hydrocephalus

Life cycle

lives within cats gut - fecal cyst - cyst within tissue of birds/mice - cats eat them

Humans infections with toxoplasma

• breathe in or ingest cat poop

• eat undercooked beef or pork

• get blood transfusion from infected donor

Behaviors associated with toxoplasmosis

with higher brain cyst load, increased risk taking, car accidents, schizophrenia, sexual attraction to smell of cat urine