Lecture 15 Flashcards
Parasites and Fungus
what is parasitism
living organism taking nourishment from host
lives on or in the host
ectoparasite
live on outer surface
endoparasite
lives inside the body
obligate parasite
requires host for all phases of life cycle
facultative parasite
can be free living, but can live in a host
accidental parasite
parasite finds the wrong host
erratic parasite
parasite that finds the wrong organ
definitive host
harbors the adult stage, or where there is sexual reproduction
intermediate host
has the larval stage or asexual reproduction
paratenic host
some other host, temporary
reservoir host
host is generally not greatly harmed by the parasite
protozoa
single cells with an organized structure
eat solids
need aquatic/moist environment
complicated life cycle
fecal-oral route of transmission
classified on locomotion: amoebae, flagellates, apicomplexa
protozoa schizogony
multiple rounds of mitosis without cytokinesis - creates a schizont
then cytokinesis occurs, releasing merozoites (daughter cells)
protozoa - amoebae
moves with pseudopodia
active growing phase - trophozoites
environmentally protected form - cysts
entamoeba histolytica
wide range of disease: diarrhea, dysentery, liver abscess, asymptomatic
fecal-oral transmission
entamoeba gingivalis
oral commensal
environmental amoebae
surface water
corneal infections with contact lens
cribriform plate
CNS infections
protozoa - flagellates
move with flagella
active growing phase - trophozoites
environmentally protected form - cysts
have a rigid outer wall - provides shape
giardia lamblia
wide range of disease: chronic diarrhea or asymptomatic
fecal-oral transmission
trichomonas vaginalis
vaginitis
sexual transmission
protozoa - apicomplexa
mature forms are non-motile
obligate intracellular parasites
complex life cycles
have a complex at the apical end
plasmodium spp
mosquito transmitted
malaria
life threatening
toxoplasma gondii
mostly asymptomatic
can cause fetal malformations
can transmit from cat stool
crytosporidium spp
watery diarrhea, can be chronic
fecal-oral or water borne
helminths
worms
multicellular, macroscopic
flatworms
flat on cross section
cestodes (Tapeworms)
trematodes (Flukes)
roundworms
round on cross section
Nematodes
Hookworms
Pinworms
cestodes - tapeworms
adult form: ribbon-like and segmented
abdominal discomfort
larval form: penetrates gut and lodges
intermediate hosts are humans
nematodes - tapeworms
have a complete digestive tract and separate sexes
very diverse group
A. Lumbricoides
abdominal pain/discomfort
transmits fecal-oral with ova in stool
T. Spiralis
massive inflammation early
muscle damage later
transmits by eating undercooked meat
ectoparasites
colonizes
insects - fleas, lice, bedbugs
arachnida - ticks, mites
nuisance, itchy
vectors for disease
tick
borrelia burgdorferi
lyme disease
fleas
yersinia pestis
bubonic plague
humans eating fungus
bread, beer
Saccharomyces cerevisiae
soy sauce
Aspergillus oryzae
mushrooms and cheese
fungus eating humans
can infect humans - mycosis or mycoses
superficial - skin, nails… Thrush, Ringworm
subcutaneous - traumatic implantation… tissue destruction and sinus
systemic mycoses - immunodeficiency, acquired through respiratory tract
fungus
have a cell wall comprised of polysaccharides including chitin and chitosan
haploid cells mate to make diploid cells, undergo meiosis which produces four haploid spores
yeast
single cells, elongate to form chain
pseudohyphae
reproduce by budding
blastospores
molds
multicellular
tubular hyphae with or without separations
create specialized sporing structures
dimorphic yeast
at lower/room temperature replicate as molds
at higher/body temperature replicate as yeasts
includes some pathogenic fungi with limited geographic distribution
spores can be infectious
candida albicans
opportunistic pathogen
lack exotoxins or endotoxins
slow and chronic infections
thrush and yeast infections
systemic candidasis virulent attributes
adhere to tissues and prostheses
change surface antigens
invade tissue with hyphae
produce enzymes that degrade host cells
candida infections
thrush - oral, vaginal, perianal, esophageal
pseudomembraneous candidasis
white membrane with raw, red base underneath
erthematous candidasis
immunosuppression, antibiotic use or dentures
angular stomatitis
lesions at angles of the mouth
erythema, soreness and fissuring
S. Aureus
skin infections
candida infection
diaper rash or nails
candida systemic infections
urinary tract - catheters
endocarditis - artificial heart valves of IV drug use
septicemia - with immunosuppression - throughout solid organs
antifungals
major target is the fungal cell membrane
ergosterol vs cholesterol
nystatin and amphotericin B
binds to ergosterol and creates a pore
azoles
antifungal ex: fluconazole, clotrimazole, miconazole
inhibit synthesis by inhibiting enzyme required for ergosterol synthesis
micafungin, anidulafungin
antifungals
inhibit glucan synthesis or specific gylcan in fungal cell wall
keratolytic fungi
attack keratin - nail, hair, skin
produce keratinase
many different species
dermophytes and dermatophytosis
fungal penetration balances squamous cell turnover long lasting
requires some minor trauma to establish
driven by moisture and occlusion
jock itch, athletes’ foot, ringworm
tinea cruris, tinea pedis, tinea corporis
