Module 7: Fungi and Protozoa

Fungal forms

yeast cells, hyphae, dimorphic, pleomorphic

Yeast cells

round/oval shape, asexual reproduction

Hyphae

long thread-like cells found in filamentous fungi, molds

Thermally dimorphic fungi

looks like mold when growing saprophytically at 25-30C and looks like yeast when growing in animal tissues at 37C+

Fungal structure

grow in loose associations or colonies

Mycelium

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

Septa

cross walls that divide hyphae into segments

Fungal Spores

fungal reproductive bodies

Fungi cell envelope

has cell walls containing chitin, a polysaccharide

Fungal nutrition

heterotrophic; can be saprobes or parasites

Fungi asexual reproduction

known as cloning, haploid stage; can be growth of existing hyphae, fragmentation which is a separated piece of mycelium forming a new colony, or spore formation

Fungi sexual reproduction

a brief diploid stage, spore formation

Fungal Identification and Cultivation

most grow on special media; observe spores and spore forming structures, hyphal type, colony texture, pigmentation, physiology, genetic makeup

Mycoses

fungal infections, can be primary of opportunistic

Primary mycosis

sickens healthy individuals

Opportunistic mycosis

sickens those who are weakened, especially systemic infections

Fungi disease mechanisms

allergic responses, mycotoxins, and mycoses(superficial, subcutaneous, and systemic)

Mycotoxins

some cause disease while others cause death, an example is an aflatoxin

Aflatoxin

a fungal mycotoxin, poisonous carcinogen, produced by 2 mold species, found in improperly stored staple commodities(corn, peanuts, rice, wheat)

Superficial Micro Diseases

colonize hair, skin, nails; infect only certain layers

Candida albicans and Trichophyton species

Candida albicans

Normal gut flora, nosocomial

Pleomorphic; outside body looks like yeast, inside looks like mold

Candidiasis: thrush, vaginal yeast infections, diaper rash, bloodstream infections in hospitals(catheters, antibiotics, weakened immunity)

Trichophyton species

contact with spores, direct or indirect

Mold which is keratinophilic; feeds on the keratin in hair, skin, and nails

Causes dermatophytosis: athlete’s foot, ringworm, jock itch

Athlete’s foot

disease name is tinea pedis, contract from locker room floors and showers

Ringworm

disease name is tinea corporis; contract from sharing clothes/sheets, barefoot in locker room, and the beach

Jock itch

disease name is tinea cruris, often spreads from athlete’s foot

Subcutaneous Micro diseases

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

Sporothrix schenckii and Fonsecaea pedrosoi

Sporothrix schenckii

contact with spores, must enter skin

thermally dimorphic

Sporotrichosis, also known as rose gardener’s disease

Fonsecaea pedrosoi

implantation of spores, thorns or splinters

mold

Chromoblastomycosis: slow growing, warty, cauliflower-like nodules

Systemic Micro diseases

Infection by inhaling spores, fungal growth in internal organs, can cause skin lesions, some are primary while others are opportunistic

Histoplasma capsulatum, Coccidioides immitis, Cryptococcus neoformans

Histoplasma capsulatum

breath in spores, bird and 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

Coccidioidmycosis(valley fever): subcutaneous lesions, bronchitis or pneumonia, fatigue

Cryptococcus neoformans

soil contaminated with pigeon/bird droppings

encapsulated yeast

Cryptococcosis: wound or cutaneous, pulmonary, meningitis

Protists

unicellular or colonial organisms lacking true tissues, eukaryotic, no cell wall, can have cyst wall, most live in water and soil, few are parasites

Nutritional Habits of Protozoa

heterotrophic and require their food in complex organic form, can be free-living or parasitic

Free-living protozoa

saprobes and grazers(on bacteria and algae)

Parasitic protozoa

feed on host fluids, such as plasma and digestive juices, and tissues

Trophozoite

motile and feeding stage, requires food and moisture

Cyst

dormant resting stage, hardy, formed when conditions become unfavorable, important factor in spread of disease

Protozoa life cycle

can vary, simple or complex; some species exist only in trophozoite stage, others alternate between both stages, life cycle dictates the mode of transmission

Protozoan reproduction

can be asexual, sexual, or both

Pseudopods

style of locomotion, also a feeding structure

Flagella

style of locomotion, vary in number from 1 to several

Cilia

style of locomotion, over entire cell surface

Amoeba

pseudopods, asexual reproduction, mostly uninucleate, most form cysts, most are free-living

Ciliates

cilia for moving, feeding, and attachment; sexual and asexual reproduction; macro and micronuclei; most form cysts; most free-living

Flagellates

flagella or flagella and amoeboid motion, sexual reproduction, uninucleate, form cysts, most free-living

Protozoa without motility

complex life cycles with asexual and sexual stages, macro and micronuclei, produce infective spores that are haploid, all within the group Sporozoa, all are parasitic

Protozoan Identification

most can be identified to genus based on appearance; shape and size, locomotor structure, special organelles or cysts, number or nuclei

Smears

traditional way to identify protozoan infection; can be blood or fecal

Amoeboid Protozoa

Entamoeba histolytica, Naegleria fowleri, Acanthamoeba species

Entamoeba histolytica

Fecal-oral; contaminated produce or water

Produces cysts

Amoebic dysentery: violent bloody diarrhea→dehydration and fever

Control of infection: Entamoeba histolytica

increased sanitation(toilets, hand washing) and water filtration(drinking, food prep, ice cubes, vegetable freshening)

Naegleria fowleri

Found in warm waters; enters nose→penetrates nasal tissues→enters brain; bacteria-eating free-living amoeba

Form cysts

Naegleriasis: primary amoebic meningo-encephalitis(PAME); less than 10 deaths/yr globally

Control of infection: Naegleria fowleri

cloronation helps, keep water out of nose, boil Neti-Pot water(they live in hot water heaters, bottled mineral water, municipal water systems)

Acanthamoeba species

Enter eye through soft contact lenses contacting either life cycle; contaminated lens solution, swimming and bathing, soil

Produces cysts

Acanthamoeba keratitis: cornea infection, can lead to blindness if untreated or not treated properly

Control of infection: Acanthamoeba species

wear contact lenses for less than 12 hours a day, disinfect lenses, replace contacts regularly, remove contacts before any water activity, wash hands before handling contacts

Ciliated Protozoa

Balantidium coli

Balantidium coli

Zoonotic: fecal-oral from pig; contaminated water

Produces cysts

Balantidiasis: large intestinal infection; chronic diarrhea, dysentery

Control of infection: Balantidium coli

good hygiene, eat only cooked foods, wash fruits and vegetables

Resevoir host

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

Biological vectors

any living agent that carries and transmits an infectious pathogen to another living organism

Trypanosomes

long crescent-shaped cells with a single flagellum, in blood during infection, transmitted by blood-sucking vectors

Flagellated Protozoa

Trypanosoma cruzi, Giardia lamblia, Trichomonas vaginalis

Trypanosoma cruzi

vector: kissing bugs; reservoirs: armadillos, opossums, raccoons, cats

No cyst stage

Chagas disease: early symptoms are fever, swollen lymph nodes; late symptoms are enlarged esophagus and colon or heart failure

Control of infection: Trypanosoma cruzi

avoid sleeping in a mud, thatch, or adobe house; use bed net; use insecticides, use insect repellent

Giardia lamblia

Fecal-oral, contaminated water or food; reservoirs are dogs, cats, and beavers

Cyst producer

Giardiasis: small intestine dysentery; no symptoms to abdominal discomfort and chronic diarrhea that is greasy, voluminous, and maloderous

Control of infection: Giardia lamblia

good hygiene, avoid drinking unfiltered stream water, was fruits and vegetables, do not let dogs lick your face

Giardiasis process

Trophozoite damages microvilli that lines intestines which causes irritation and leads to production of mucous(trophs feed on this) which lowers fat and carbohydrate absorption; can also interfere with vitamin/nutrient absorption specifically with vitamin A and D

Loss of Vitamin A from Giardiasis effect

can negatively impact vision in children

Loss of Vitamin D from Giardiasis effect

can cause rickets which are weak or soft bones in children

Trichomonas vaginalis

Sexually transmitted

No cyst

Trichomoniasis(Trich): in women symptoms are genital itching, painful urination, and premature delivery if pregnant; asymptomatic in men

Control of infection: Trichomonas vaginalis

few sexual partners, condoms

Non-motile Protozoa

Plasmodium falciparum, Cryptosporidium spp, Toxoplasma gondii

Malaria history

known since antiquity(1550 BCE), commonly found in swamps, causative agent search focused on swamp water or air

Malaria

genus Plasmodium, intracellular in RBCs, vector is mosquitoes, most serious species is Plasmodium falciparum as it causes 75% of mortality and is becoming extremely drug resistant

Plasmodium falciparum

Anapheles mosquito

Falciparum malaria: infected cells lead to microinfarctions(tiny areas of dead tissue) in brain, liver, etc.; mostly limited to Africa

Falciparum malaria symptoms

fever→death, host inflammatory response resulting in severe chills and fever(paroxysms), anemia due to loss of red blood cells, recurrence of paroxysms at periodic intervals

Control of infection: Plasmodium falciparum

control mosquitoes by use of insecticides(develop resistance quickly, most effective on is banned) and draining sources of water; control getting bitten using bed nets with insecticide, covering up, and mosquito spray

Cryptosporidium spp

Fecal-oral through water; reservoirs are cattle and domestic pets

Produces cysts

Cryptosporidiosis: profuse watery diarrhea

Control of infection: Cryptosporidium spp

wash hands; wash fruits and vegetables; don’t swallow water from lakes, streams, or public pools; minimize contact with young animals

Toxoplasma gondii

transmission variable: breath in or ingest cat poop, eat undercooked beef or pork, get blood transfusion from infected donor, from mother to baby

50% of people have brain cysts

Toxoplasmosis: Flu-like→latent→brain lesions that cause death; congenital taxoplasmosis causes hydrocephalus in babies

Effects of increased cyst load from Taxoplasmosis

increase in human behaviors: risk-taking, car accidents, schizophrenia, sexual attraction to smell of cat urine