1. Eukaryotic microorganisms
Eukaryotic Pathogens
Eukaryotic microorganisms
Plantae
Animalia
Fungi
Monera
Protista
Fungi
cell wall composed of chitin
absorptive nutrition (produce exoenzymes)
many saprophytes but some parasites of plants or mammals
~30% of known fungi cause disease (MYCOSES)
scientists who study fungi = mycologists
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2. Fungal anatomy: Thalli
Eukaryotic Pathogens
Fungal anatomy: Thalli
hyphae
thallus = nonreproductive, vegetative form
can be single cells, globular shaped (as in yeasts)
can be long, branched filaments called HYPHAE (as in molds)
many hyphae intertwined = mycelium (pl. = mycelia)
Dimorphic - organism that makes two kinds of thalli (both yeast and mold forms)
in response to differing environmental conditions
mycelium
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3. Fungal anatomy: Fruiting bodies
Eukaryotic Pathogens
Fungal anatomy: Fruiting bodies
Sporangiospores (sac)
Chlamydospores (walled in)
Conidiospores (no sac)
fruiting body = reproductive structure
Sporangiospores - spores inside a sac on tips or side of hyphae
the sac is called a sporangium
stalk that bears the sporangium is called the sporangiophore
in picture, the yellow-shaded micrograph
Chlamydospores
spores with a thickened cell wall inside hyphae
in picture - the tan cells on white background
Conidiospores - made at tip or sides of hyphae but not in a sac
in picture, blue-green cells
NOTE TO SELF:
-phore = to bear
-angium = vessel
chlamys- = mantle
conidio from Gr. Konis = dust
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4. Important yeasts: Saccharomyces cerevisiae
Eukaryotic Pathogens
Important yeasts: Saccharomyces cerevisiae
Thallus
Fruiting body:
blastoconidia
Remind: Yeasts
thalli usually single globular cell
S. cerevisiae essential to baking industry, alcoholic beverage industry
also frequently used for research
not usually a human pathogen
in picture - fruiting body = blastoconidia a.k.a. bud
type of conidiospore
on agar, makes colony similar to bacterial colony
do not make hyphae
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5. Important yeasts: Candida albicans
Eukaryotic Pathogens
Important yeasts: Candida albicans
“Thrush”
Diaper rash
Important yeasts: Candida albicans
part of normal flora (GI, respiratory tracts, female GU tract)
opportunist: candidiasis
can be local as in thrush (mouth) or skin (diaper rash) or ocular
can be systemic
Table 22.2 in text shows HUGE list of all possible manifestations of candidiasis
buds, as S. cerevisiae
Bauman Fig
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6. Important molds: Rhizopus spp.
Eukaryotic Pathogens
Important molds: Rhizopus spp.
Important molds: Rhizopus spp.
bread mold!
often causes food spoilage
opportunist - can cause “Zygomycosis”
forms sporangiospores (inside a sac)
Leboff & Pierce, Figs. 10-4
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7. Important molds: Aspergillus spp.
Eukaryotic Pathogens
Important molds: Aspergillus spp.
usually colored colony with white edge (color may be yellow, green or brown)
Aspergillosis = several diseases r/t inhaling fungal spores
VERY common in air!!
usually just causes allergies but can cause serious infection in immunocompromised people
respiratory infections
can infect sinuses, conjunctiva, eye socket, brain
systemic rare except in AIDS patients
most disease caused by species A. niger, A. fumigatus & A. flavus
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8. Important molds: Penicillium spp.
Eukaryotic Pathogens
Important molds: Penicillium spp.
conidiophores
giveaway is radial furrows
also distinctively green with white apron
most known for production of penicillin
some species also used for cheese production
P. roquefortii - Roquefort cheese
P. camemberti - Cambert and Brie
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9. Major Groups of “True” Parasites
Eukaryotic Pathogens
Major Groups of “True” Parasites
Protozoans
Single-celled eukaryotes
Malaria, Giardia, Trichomonas vaginalis
Helminths (The Worms)
Multicellular animals
Flukes, Tapeworms, Roundworms
Ectoparasites
Live outside the host
Ticks, Lice, Fleas
Remember that parasitologists only consider eukaryotic parasites in the definition. Bacteria and virus are pathogens, but not considered parasites.
Other specialties in biology sometimes do refer to those groups as parasites.
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10. Protozoan Parasites Single-celled eukaryotes Can invade:
Tissues- Trypanosomes, Toxoplasma, Plasmodium
Intestinal lumen- Entamoeba histolytica, cryptosporidium

11. Protozoans general life cycles
Eukaryotic Pathogens
Protozoans general life cycles
Trophozoite (active, feeding)
Adverse environment
Release of active cellular form
Excystment
Encystment
Cyst formation
Bauman p. 349
all free-living & pathogenic protozoa have motile feeding stage called trophozoite
many have dormant protective state called cyst
protect from harsh environmental conditions
Moisture, nutrients
Cyst (dormant, resting)
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12. Entamoeba histolytica
Eukaryotic Pathogens
Entamoeba histolytica
Cyst
Trophozoite
model amoeba!
no defined shape
move, get food using pseudopodia
~10% population has as harmless member of normal flora!
lots of human reservoirs
most infection r/t ingestion of contaminated water (fecal contamination) that has cysts
multiplies in intestine
three types of amoebiasis (a-me-bi’a-sis)
luminal - localized to intestines, little damage
amoebic dysentery - more common, diarrhea, colitis, ulceration (can be fatal)
invasive extraintestinal amoebiasis - MAJOR problem (can be fatal)
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13. Entamoeba histolytica
Epidemiology: Worldwide distribution- Mexico, India, West and South Africa, South America
10% of the world’s population is infected
Most are asymptomatic (carriers)
50-100,000 deaths per year
Vector: Flys carry cysts from human feces to human food or water or humans self-infect after touching fecally contaminated items, can be sexually transmitted

14. Entamoeba histolytica
Reservoir: Humans are the only hosts
Pathologies:
Mild to severe intestinal discomfort
Dysentary (bloody diarrhea)
Can invade and destroy the liver
Treated with Metronidazole (flagyl)

15. Trypanosoma brucei African sleeping sickness Eukaryotic Pathogens
a flagellate - moves via flagella
insect vector: tsetse flies
several animal reservoirs - domestic animals and wild
can also be transmitted from human to human via tsetse flies
complex life cycle
disease:
wound becomes necrotic
parasites in blood cause fever, headaches, swelling of lymph nodes
if invade CNS cause meningoencephalitis - comes with HA, extreme drowsiness, coma, death
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16. Trypanosoma cruzi Epidemiology:
Eukaryotic Pathogens
Trypanosoma cruzi
Epidemiology:
Mexico to S. America
16-18 million people are infected (45,000 die per year)
Vector: Reduviid bug (aka. kissing bug)
Bugs live in rafters of thatched hut houses
Come down at night and bite while people are asleep
Often bite near corners of mouth (why nicknamed “kissing bug”)
Bug defecates on wound after biting victims
Parasites are in bug feces and enter host through wound when victim scratches at bite
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17. Trypanosoma cruzi (Chagas Disease)
Eukaryotic Pathogens
Trypanosoma cruzi (Chagas Disease)
Reservoir: rodents, armadillos, dogs, cats
Pathologies:
Inflammation at bite
Swelling of the eyes
Fever, malaise
Enlarged Heart
Heart Failure
Hallmark symptom is the swelling of the eye called “kalabar” swelling
Deaths occur primarily as a result of heart failure
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18. Plasmodium spp. malaria schizont Infected RBC Eukaryotic Pathogens
[ in group Apicomplexans
characterized by a complex of organelles at apical end of cell]
complex life cycle
four different species of Plasmodium cause malaria in humans
endemic in more than 100 countries!
vector = mosquito
kills 2-3 million people annually (usually kids)
schizonts - multinucleate cell involved in asexual reproduction
schizont
Infected RBC
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19. MALARIA Kills 1-2 million/year Loss of productivity Vaccines slow
Eukaryotic Pathogens
MALARIA
Kills 1-2 million/year
Loss of productivity
Vaccines slow
Mosquito abatement
Swamps
Vectored by mosquitos which must breed in standing water
Mosquito also considered an intermediate host b/c the parasite matures in the mosquito
“Mal” “aria” means bad air---people knew association with swamps before agent was found
~200million cases per year
4 kinds of plasmodium affect humans
P. falciparum is very deadly, causes blood clots in the brain resulting in coma and death
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20. Plasmodium Life Cycle Eukaryotic Pathogens
Organisms enter from mosquito saliva
Travel to liver and enter cells-multiply
Burst out and move into blood stream-enter RBCs-multiply
As parasites bursts out of RBCs-antigenic and extremely pyrogenic (cause high fever)
Fever so high that non-deadly strain of plasmodium was used to treat syphilis in the early 1900’s (syphilis bacteria is very heat labile)
Parasites enter new RBC’s fever goes away, organisms multiply then burst out of RBC’s causing fever to return
This causes the cycles of high fevers
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21. Co-Incidence Eukaryotic Pathogens
Sickle cell is a genetic disease caused by a single point mutation (base-pair substitution) on the hemoglobin gene which causes a
missense mutation
This genetic condition affords protection from malaria in heterozygotes
Homozygotes for the condition have sickle cell disease and don’t live long
Homozygotes for normal hemoglobin have no protection and often die of malaria
Selection is directed towards heterozygotes- regions with high malaria rates also tend to have high sickle cell rates
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22. Toxoplasma gondii Toxoplasmosis Bow-shaped cells Eukaryotic Pathogens
Life cycle is between felines and their prey and other intermediate hosts (parasite MUST travel through felid intestine to mature)
Intermediate hosts include birds (incl. poultry), rodents, pigs, humans
Typically sub-clinical in intermediate hosts
Primary danger to humans is for pregnant women
Main risk of clinical sx is if infection occurs during first trimester. Fetus is vulnerable and toxo can cross placenta.
Can result in mental retardation and other developmental abnormalities
About 50% of human infections are the result of eating contaminated & undercooked meat (poultry, pork)
The rest are from exposure to cysts in cat litter, sandboxes and from contact with soil (gardening)
No risk from contact with cats directly
Bow-shaped cells
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23. Giardia lamblia a.k.a. Giardia intestinalis
Eukaryotic Pathogens
Giardia lamblia a.k.a. Giardia intestinalis
giardiasis
called “the most photogenic parasite”
water-borne diarrheal disease
Sx: yellow, frothy, sulfur smelling diarrhea
very hardy - can survive for long periods of time outside host
if dog drinks water from stream, can later pass to owner (don’t let your dog lick your face!!)
life cycle similar to Entamoeba
infection (giardiasis) severity ranges - fluid loss can be life threatening
usually treated with drug Metronidazole
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