Transcript Foundations in Microbiology

Protozoa, Slime Molds & Helminths
Chapter 5 & 23
Talaro
Protozoa
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65,000 species
Heterotrophic
Eukaryotic
Most are unicellular, colonies are rare
Most have locomotive structures
– flagella, cilia, or pseudopods
• Vary in shape
• Typically inhabit water or soil
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Protozoa
• Trophozoite
– Motile feeding stage
• Cyst
– A dormant resistant stage
• Asexual and sexual reproduction
– Most propagate by simple asexual
cell division of the trophozoite
– Many undergo formation of a cyst
– Others have a complex life cycle that
includes asexual & sexual phases
• Majority are NOT pathogens
• Some are animal parasites & can
be spread by insect vectors
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Zoonosis
An infectious disease
in animals that can be
transmitted to people.
The natural reservoir
for the infectious
agent is an animal.
The apical complex
include structures that
allow the parasite to enter
other cells.
Anterior vesicles that
secrete digestive
enzymes.
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Flagellated Protozoa
• Motility by flagella alone or
by both flagella & amoeboid
motion
• Several parasites
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Giardia
Trichomonas
Trypanosoma
Leishmania
attachment
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Trichomonas
• Small, pear-shaped cells
• 4 anterior flagella & an undulating
membrane
• Exists only in trophozoite form
• 3 species infect humans
– T. vaginalis
– T. tenax
– T. hominis
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Trichomonas vaginalis
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Causes an STD called trichomoniasis
Reservoir is human urogenital tract
50% of infected are asymptomatic
Strict parasite, cannot survive long outside of host
Flagyl (Metronidazole)
3 million cases/year
Female symptoms
Interferes with DNA synthesis
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Foul-smelling, green-to-yellow discharge
Vulvitis
Cervicitis
Urinary frequency & pain
• Male symptoms
– Urethritis, thin, milky discharge, occasionally prostate
infection
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Giardia lamblia
• Unique symmetrical heart
shaped cells
• Cysts are small, compact,
and multinucleate
• Cysts can survive for 2
months in environment
• Cysts enter duodenum,
geminate, & travel to
jejunum to feed & multiply
• Spread through
contaiminated water & food
– Fecal oral contamination
• Giardiasis
– Diarrhea, abdominal pain
• Diagnosis is difficult
because organism is shed in
feces intermittently
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Hemoflagellates
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Live in blood & tissues of human host
Obligate parasites
Incite life-threatening and debilitating zoonoses
Spread by blood-sucking insects that serve as
intermediate hosts
• Acquired in specific tropical regions
• Have complicated life cycles & undergo morphological
changes
• Trypanosoma T. brucei (causes sleeping sickness)
- T. cruzi (causes Chagas disease)
• Leishmania
(causes Leishmaniasis)
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large fully
formed stage
no flagella
Infective
anterior flagellum
undulating membrane
Diagnostic
Trypanosoma10cruzi
Trypanosoma brucei
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Causes African Sleeping Sickness
Spread by tsetse flies
Harbored by reservoir mammals
Biting of fly inoculates skin with
trypanosome, which multiplies in
blood & damages spleen, lymph
nodes & brain
• Chronic disease symptoms are
sleep disturbances, tremors,
paralysis & coma
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Trypanosoma cruzi
• Chagas disease
• Kissing bug is the vector
– Reduviid / Assassin Bugs
re·du·vi·id (family Reduvidae, subfamily
Triatominae (Triatomine Bugs))
• Infection occurs when bug feces are
inoculated into a cutaneous portal
• Local lesion, fever, & swelling of
lymph nodes, spleen, & liver
• Heart muscle & large intestine harbor
masses of amastigotes
– Divide by binary fission
• Chronic inflammation occurs in the
organs
– Especially heart & brain
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Chagas Disease
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Leishmania
• Leishmaniasis is a
zoonosis transmitted
among mammalian hosts
by female sand flies that
require a blood meal to
produce eggs
• Infected macrophages
carry the pathogen into the
skin & bloodstream, giving
rise to fever, enlarged
Viscera or the internal organs,
organs & anemia
particularly the liver, spleen,
• Kala azar is the most
bone marrow & lymph nodes
severe & fatal form
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Amoeboid Protozoa
• Amoeba
– Pseudopods
• Radiolarian
– Shelled ameba
• Entamoeba histolytica
– Incites dysentery, abdominal pain, fever, diarrhea &
weight loss
– Carried by 10% of world population
– Asymptomatic in 90% of patients
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Entamoeba histolytica
• Alternates between a large trophozoite, motile by
means of pseudopods & a smaller nonmotile cyst
• Humans are the primary hosts
• Ingested
• Cysts are swallowed & enter the small intestine;
alkaline pH & digestive juices stimulate cyst to
release 4 trophozoites
• Trophozoites attach, multiply, actively move about &
feed
• Ameba may secrete enzymes that dissolve tissues &
penetrate deeper layers of the mucosa
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Amebic Dysentery
Entamoeba histolytica
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Entamoeba histolytica
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Ciliated Protozoa
• Trophozoites have cilia
• Majority are
nonpathogens
• Balantidium coli
– An occupant of the
intestines of domestic
animals such as pigs &
cattle
– Acquired by ingesting
cyst-containing food or
water
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Balantidium coli
• Trophozoite erodes
intestine & elicits
intestinal symptoms
• Healthy humans are
resistant
• Rarely penetrates
intestine or enters blood
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Apicomplexan Protozoa
• Non-motile in mature stage
– Male gametes are motile
• Alternate between sexual & asexual phases & between
different animal hosts
• All members are parasitic
• Most form specialized infective bodies that are
transmitted by arthropod vectors, food, water, or other
means
– Plasmodium
– Toxoplasma
– Cryptosporidium
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Plasmodium
• Causes malaria
• Female Anopheles mosquito
is the vector
• Obligate intracellular
sporozoan
• 4 species: P. malariae, P.
vivax, P. falciparum & P.
ovale
• 300-500 million new
cases each year
• 2 million deaths each
year
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Plasmodium
• Infective forms for humans (sporozoites) enter blood
with mosquito saliva, penetrate liver cells, multiply, and
form hundreds of merozoites, which multiply in & lyse
RBCs.
• Symptoms include episodes of chills-fever-sweating,
anemia, and organ enlargement.
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Toxoplasma gondii
• Causes toxoplasmosis
• Obligate parasite with
extensive distribution
• Lives naturally in cats that
harbor oocysts in the GI
tract
• Acquired by ingesting raw
meats or substances
contaminated by cat feces
• Most cases of
toxoplasmosis go unnoticed
except in the fetus & AIDS
patients which can suffer
brain & heart damage
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Cryptosporidium
• An intestinal pathogen
• Infects a variety of animals
• Exists in tissue & oocyst
phases
• 1990s – 370,000 cases in
Milwaukee, WI due to
contaminated water
• Causes enteric symptoms
• AIDS patients may suffer
chronic persistent diarrhea
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Slime Molds
• Two classifications - cellular and plasmodial
• Motile
• Not pathogens
• Ingest food by endocytosis
• Form spores on erect fruiting bodies
• Cellular slime molds only undergo asexual reproduction
• Plasmodial slime molds undergo both sexual and asexual reproduction
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Cellular Slime Molds - Asexual
• Unusual life cycle - both amebal and fungal-like characteristics
• Favorable conditions allow amebal growth
• Unfavorable conditions cause some cells to generate cAMP
• Cells migrate toward cAMP and aggregate – form a pseudoplasmodium
• ‘Slug’ moves toward light - differentiates
• Spores generate in cap
• Released to germinate as amoebal form under favorable conditions
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Cellular Slime Mold
Amebas disseminated
as spores
migrates
Amebas congregate
toward cAMP
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Plasmodial (acellular) Slime Molds
• Large cell with many nuclei - PLASMODIUM
• Moves as giant amoeba engulfing organic matter and bacteria
• Distributes nutrients through cytoplasmic streaming
• Form stalks and reproductive structures under starvation conditions
• Sporangium with spores
• Nuclei undergo meiosis, spores released under favorable conditions
• Fuse to form diploid cells, cells fuse to make plasmodium
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Plasmodial Slime Molds
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Parasitic Helminths
• Multicellular parasitic animals
• Adult worms mate & produce fertilized eggs that hatch into larvae that
mature in several stages to adults
• The sexes may separate or hermaphroditic
• Adults live in the definitive host
• Eggs & larvae may develop in the same host, external environment or
an intermediate host
A transport host experiences no parasitic development
Have mouthparts for attachment to or digestion of host tissues
Most have well-developed sex organs that produce eggs and sperm
50 species parasitize humans
Acquired though ingestion of larvae or eggs in food; from soil or
water; some are carried by insect vectors
• Afflict billions of humans
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Major Groups of Helminths
1. Roundworms (nematodes) - cylindrical, a
complete digestive tract, a protective surface
cuticle, spines & hooks on mouth; excretory &
nervous systems poorly developed
2. Flatworms – flat, no definite body cavity;
digestive tract a blind pouch; simple excretory &
nervous systems
• Cestodes (tapeworms)
• Trematodes or flukes, are flattened , nonsegmented
worms with sucking mouthparts
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Roundworms
• Filamentous with protective cuticles, circular muscles, a
complete digestive tract, & separate sexes
• Ascaris lumbricoides
• Trichuris trichiura
• Enterobius vermicularis –pinworm
• Hookworms
• Strongyloides stercoralis
• Trichinella spiralis – raw pork…
• Filarial worms
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Ascaris lumbricoides
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A large (up to 30 mm long) intestinal roundworm
1 billion cases worldwide
Most cases in the US occur in the southeastern states
Indigenous to humans
Ascaris spends its larval & adult stages in humans &
releases embryonic eggs in feces, which are spread to
other humans
• Ingested eggs hatch into larvae & burrow through the
intestine into circulation & travel to the lungs &
pharynx & are swallowed
• Adult worms complete cycle in intestines
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Ascaris
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Hookworms
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Ascaris lumbricoides
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Ascaris lumbricoides
• Worms retain motility, do not attach
• Severe inflammatory reactions mark the
migratory route
• Allergic reactions can occur
• Heavy worm loads can retard physical &
mental development
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Tapeworms
• Flatworms
• Long, very thin, ribbonlike bodies composed of sacs
(proglottids) & a scolex (head) that grips the intestine
• Each proglottid is an independent unit adapted to
absorbing food & making & releasing eggs
• Taenia saginata
• Taenia solium
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Taenia saginata
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Beef tapeworm
Very large, up to 2,000 proglottids
Humans are the definitive host
Animals are infected by grazing on land contaminated
with human feces
• Infection occurs from eating raw beef in which the
larval form has encysted
• Larva attaches to the small intestine & becomes an
adult
• Causes few symptoms – sometimes weight loss
despite good appetite
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Taenia solium
• Pork tapeworm
• Infects humans through ingesting cysts or eggs
• Eggs hatch in intestine, releasing tapeworm
larva that migrate to all tissues & encyst
• Most damaging if they lodge in heart muscle,
eye, or brain
• May cause seizures, psychiatric disturbances
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Taenia
solium
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