introduction to parasitology and amoebas Flashcards
overview of microbes
- Bacteria
● Unicellular
● Prokaryotes
● Lack a nuclear membrane and a true nucleus, mitochondria, an endoplasmic reticulum, and Golgi bodies
● DNA is suspended in the cytoplasm - Fungi
● Heterotrophic
● Eukaryotes
● Most are multicellular, and many can reproduce sexually and asexually
● Molds
● Yeast - Virus
● Acellular
● Consist of DNA or RNA and rarely both
● Require host cells for replication and metabolism - Parasites
● Some are unicellular (protozoa) and some are multicellular (metazoa)
● Eukaryote
Study of parasites, organisms that live on and obtain their nutrients from another organism
parasitology
*Area of biology with the phenomenon of dependence of one living organism on another
[part of biology that studies how one organism depends on another.]
a type of symbiotic relationship where the parasite benefits while the host suffers because the parasite competes for nutrients.
Parasitism
Symbiotic relationship – living together
briefly explain the 2 phases of the parasitic life cycle
Endoparasite – inside the host:
Example: Protozoa (single-celled parasites)
They invade the body, often in the intestines, blood, or tissues.
Ectoparasite – outside:
Example: Arthropods (like fleas, ticks, and lice)
Example: Human head lice – live on the scalp and cause infestation.
How Parasites Infect Humans
Parasite Contact – The parasite comes into contact with humans (e.g., through food, water, or insect bites).
Infective Stage – The parasite enters the body and finds a place to live.
Multiplication – The parasite grows and competes for nutrients inside or on the body.
Diagnostic Stage – The parasite leaves the body (e.g., through feces, urine, or skin).
Environment Stage – The parasite enters the soil, water, or another host (like an insect or animal).
💡 Example:
A person drinks contaminated water → Parasite enters intestines → Multiplies and causes illness → Leaves the body in feces → Enters the environment → Can infect another person.
Parasite Nomenclature and Classification
Scientific Name Format:
Naming Structure:
Scientific Name Format:
Typewritten → Italicized
Handwritten → Underlined
In Research Papers → Can be abbreviated after the first mention (e.g., E. histolytica)
Naming Structure:
Genus (First Part)
First letter capitalized
Example: Entamoeba
Species (Second Part)
Always lowercase
Example: histolytica
briefly explain the 3 major groups of clinically significant parasites
(index card)
- protozoa
- metazoa
-arthropods
amoeba morphology and life cycle
index card
Life Cycle Process:
Ingestion of Cyst – Humans consume contaminated food or water.
Excystation – Cyst → Trophozoite (occurs in the small intestine).
Trophozoites Multiply – Reproduce by asexual binary fission.
Encystation – Trophozoite → Cyst (occurs in the large intestine due to harsh conditions).
Cysts Exit via Feces – Cysts survive in the environment and infect new hosts.
Why Trophozoites Turn into Cysts?
Overpopulation of amoebas.
Changes in pH, food supply, or oxygen levels.
Harsh conditions force transformation into protective cysts.
Transmission & Infection of Amoeba
Cysts are the main infectious stage.
Spread through contaminated food, water, or surfaces.
Trophozoites do not usually transmit because they are easily destroyed
[Trophozoites (active form of amoebas) die quickly outside the host because they are delicate.
Cysts, on the other hand, have a protective wall, so they can survive outside for a long time.]
Prevention & Treatment of Amoeba
Drink clean, filtered water and eat hygienic food.
Proper sanitation and handwashing = prevent infections.
Meds: metronidazole to treat infections.
what are the forms found in the specimen used in lab diagnosis of amoebas
✔ Specimen Used: Stool Sample
✔ Forms Found:
Trophozoites (Active Stage): Found in soft, loose, or liquid stool
Cysts (Dormant Stage): Found in formed stool
what are the microscopic identification and techniques used in lab diagnosis of amoebas
✔ Microscopic Identification:
Size Determination → Measured using an ocular micrometer
Nuclear Characteristics → Number, shape, and positioning of nuclei
Cytoplasmic Inclusions → Observing structures inside the cytoplasm
Motility → Only trophozoites show movement
✔ Microscopic Techniques:
Saline Wet Preparation → Helps observe trophozoite motility
Iodine Wet Preparation → Enhances visibility of internal structures
Permanent Stain → Confirms diagnosis, but may cause shrinkage
Asymptomatic Infections vs Symptomatic Infections
🔹 Asymptomatic Infections → Many infected people show no symptoms
🔹 Symptomatic Infections → Often present as diarrhea without a clear cause
- it spreads through
✔ Contaminated food or water
✔ Poor sanitation & crowded environments increase risk
✔ Common in underdeveloped countries & travelers
Pathogenic vs. Nonpathogenic Amoebas
✔ Nonpathogenic Amoebas → Suggest contaminated food/water intake
✔ Pathogenic Amoebas → Can cause diseases (Only E. histolytica is a universal pathogen)
Extraintestinal Infections (Beyond the intestines)
mouth
eye
brain
what are the 2 classifications of Amoeba
1.Intestinal Amoebas
- Affect the Digestive System
- Extraintestinal Amoebas
- Infect Other Parts of the Body
who named Entamoeba histolytica
Fritz Schaudinn
“Histo-“ (tissue) + “-lytica” (destruction) = “tissue-destroying”
Why Does E. histolytica Ingest RBCs?
E. histolytica is pathogenic (causes disease) and feeds on red blood cells (RBCs).
This helps it survive and multiply inside the human intestine.
difference between Entamoeba histolytica Trophozoites and Entamoeba hartmanni Trophozoites
Size → E. histolytica is bigger, E. hartmanni is smaller.
Motility → E. histolytica moves fast and directional, E. hartmanni moves slow and random.
Inclusions → E. histolytica can have ingested RBCs, while E. hartmanni may have ingested bacteria but never RBCs.
Pathogenicity → E. histolytica causes disease, E. hartmanni is harmless.
difference between Entamoeba histolytica Cyst and Entamoeba hartmanni Cyst
Size is the most reliable feature → E. histolytica cysts are larger than E. hartmanni cysts.
E. histolytica cysts are pathogenic, while E. hartmanni cysts are harmless.
E. hartmanni cysts often have round-ended chromatoid bars and diffuse glycogen mass.
[E. histolytica → Cigar-shaped, longer, with sharper ends.
E. hartmanni → Rounded ends, shorter, less distinct.]
What Do Pseudopods Look Like in
- Entamoeba histolytica
- Entamoeba hartmanni
In Entamoeba histolytica:
Long, slender, and finger-like pseudopods
Unidirectional movement (moves in one main direction)
In Entamoeba hartmanni:
Shorter, less defined pseudopods
Nonprogressive movement (does not move in one clear direction)
Why Does Entamoeba Ingest Bacteria?
Food Source – Bacteria provide nutrients that E. coli needs to survive and grow.
Saprophytic Lifestyle – Unlike E. histolytica, which eats red blood cells, E. coli only consumes debris and bacteria, making it harmless to humans.
Digestive Process – E. coli engulfs bacteria using its pseudopodia (extensions of its body) and digests them inside vacuoles (small sacs in its cytoplasm).
distinctive features of each
Entamoeba histolytica
Ingests RBCs, causes dysentery, 4 nuclei cyst, cigar-shaped chromatoid bars
Entamoeba hartmanni
Smaller than E. histolytica, non-pathogenic, rounded chromatoid bars
Entamoeba coli
Up to 8 nuclei in cyst, splintered chromatoid bars, sluggish movement
Entamoeba polecki
1 nucleus in cyst, angular chromatoid bars, often found in pigs
Endolimax nana
Blot-like karyosome, 4 nuclei cyst, no chromatoid bars, smallest amoeba
Iodamoeba butschlii
Large glycogen mass in cyst, 1 nucleus, vacuolated cytoplasm
Entamoeba gingivalis
No cyst stage, ingests WBCs, found in mouth (associated with poor oral hygiene)
Naegleria fowleri
Brain-eating amoeba, flagellated stage, causes fatal meningoencephalitis
Acanthamoeba
Eye & brain infections, double-walled cyst, spiny pseudopods
life cycle of parasites
Ingestion of Cyst: Infection begins when a person swallows an infective cyst.
Excystation in the Small Intestine:
The cyst opens, releasing eight motile trophozoites due to nuclear division.
Colonization in the Large Intestine:
Trophozoites settle in the lumen of the large intestine, multiply by binary fission, and feed on host cells.
Possible Organ Migration:
Some trophozoites move to other organs, like the liver, where they may cause abscesses.
If trophozoites do not return to the intestine, their life cycle ends, and diagnosis must rely on serologic (blood) tests.
Formation and Excretion of Cysts:
Encystation (Cyst Formation):
Trophozoites transform into cysts inside the intestine.
A mature cyst has four nuclei and is ready to be excreted.
Cysts in the Environment:
Infective cysts are excreted in feces and survive for up to a month in contaminated environments.
They are resistant to harsh conditions.
Trophozoites vs. Cysts in Stool Samples:
Trophozoites appear in liquid or semi-formed stools (when digestion is fast).
Cysts appear in normal stools (when digestion is regular).
life cycle of Entamoeba gingivalis
Habitat & Spread:
E. gingivalis is commonly found around the gum line, in tartar, and in gingival pockets, especially in unhealthy mouths.
It can also inhabit the tonsillar crypts and bronchial mucus.
E. gingivalis may be found in the sputum and lung abscesses, making it important to differentiate from E. histolytica, which can also be present in these samples.
Surprisingly, it can be present even in individuals with good oral hygiene.
Life Cycle & Reproduction:
E. gingivalis is a scavenger, feeding on dead and disintegrated cells.
It multiplies through binary fission (simple cell division).
No cyst stage exists, meaning it cannot survive outside the host for long.
Survival & Transmission:
E. gingivalis cannot survive stomach acid, so it does not spread through ingestion like other amoebas.
It has been recovered from vaginal and cervical samples of women using intrauterine devices (IUDs).
The parasite often disappears after IUD removal, suggesting a temporary colonization.
life cycle of Naegleria fowleri
Life Cycle & Transformation:
The ameboid trophozoites reproduce by binary fission (simple cell division).
In water, they can temporarily transform into flagellate trophozoites, but these do not divide.
The cyst stage is only found in the environment, allowing survival in harsh conditions.
The full life cycle (trophozoites ↔ flagellates ↔ cysts) only occurs outside the human body.
Infection & Transmission:
Main source: Contaminated water, especially warm freshwater lakes, hot springs, and poorly maintained pools.
Enters the body through the nasal mucosa when swimming or diving.
Travels to the brain, causing rapid tissue destruction and a fatal condition called primary amebic meningoencephalitis (PAM).
Rarely, infection may occur by inhaling dust contaminated with N. fowleri.
Forms of Naegleria fowleri and Acanthamoeba
Forms of Naegleria fowleri:
Ameboid trophozoites (only form found in humans, responsible for infection).
Flagellate trophozoites (temporary form in water, does not reproduce).
Cysts (exist only in the environment, not in the human body).
Forms of Acanthamoeba:
1. Trophozoites (active form, responsible for infection).
2. Cysts (dormant form, survives in harsh conditions).
Can switch between these two forms in the external environment.
how is Acanthamoeba different from Naegleria fowleri
🚫 Acanthamoeba is not linked to swimming in dirty water like N. fowleri.
🐌 It causes slower infections, while N. fowleri acts fast and is often deadly.
🦠 There are 10 types of Acanthamoeba that can infect humans, but Acanthamoeba castellanii is the most common cause of brain and eye infections.
life cycle of Acanthamoeba
Respiratory or Skin Entry (CNS Infection Route):
Inhalation of dust or aspiration of contaminated material brings Acanthamoeba into the body.
It can also enter through skin ulcers or wounds.
Once inside, the parasite spreads via the bloodstream (hematogenous spread) to the brain, leading to severe CNS infections.
Direct Eye Entry (Eye Infection Route):
Contact lens users who use nonsterile, homemade saline solutions are at high risk.
The parasite directly invades the cornea, causing Acanthamoeba keratitis, a painful and vision-threatening infection.
Eye trauma can also allow the parasite to enter.
briefly explain the cyst and trophozoites feeding stage
Trophozoites:
The trophozoite is the active, feeding stage of a protozoan.
It is the “live” stage where the organism is actively eating, growing, and reproducing inside its host (like your intestines).
This stage is usually when the protozoa cause symptoms or infection because they are actively multiplying and feeding on nutrients.]
Cysts:
The cyst is the dormant, protective stage.
When conditions are not favorable (like when the environment becomes dry or when the host’s immune system attacks), the protozoa turn into cysts.
Cysts can survive outside the host in harsh conditions and are resistant to things like dehydration.
When the cysts enter a new host or favorable environment, they turn back into trophozoites to begin feeding and growing again.
In simple terms, the trophozoite is the “active, hungry” form, and the cyst is the “resting, protective” form of the protozoan.
E. hartmanni
MOT
INFECTIVE STAGE
DIAGNOSTIC STAGE
ASSOCIATED DISEASE
TREATMENT
PREVENTION AND CONTROL
not:
Fecal oral route
Ingestion of contaminated food or water
Contact with contaminated surface
Infective stage: mature cysts
Diagnostic stage: both trophozoites and cysts
Associated disease:
Normal asymptomatic
Treatment: nil
Prevention and control:
Good sanitation
Personal hygiene practices
Protection of food from vectors
Same w E. nana
Same w I. Butschlii (mot - contaminated hog feces)
Life cycle of E. hartmanni
Host ingest mature cysts through contaminated food, water or direct contact
(Those schists are highly resistant and can survive in the environment for days to weeks)
Upon reaching the small intestine, excysstation occurs, release trophozoites
Migrate to colon
Feeds on intestinal contents without causing tissue damage
When conditions become unfavorable, trophozoites undergo encystation = form protective cysts in the large intestine
Both cyst and trophozoites are secreted in the feces, with cyst remaining viable in moist environment = allow transmission to new hosts
E. coli life cycle
Index card
E. coli
INFECTIVE STAGE
DIAGNOSTIC STAGE
nil
it is a bacterium that multiplies directly by splitting in two, without needing special forms to infect or be detected like parasites do.
Life cycle of E. Polecki
Ppt
E. polecki
EPIDEMIOLOGY
MOT
INFECTIVE STAGE
DIAGNOSTIC STAGE
ASSOCIATED DISEASE
TREATMENT
PREVENTION AND CONTROL
Southeast Asia and New Guinea
Human to human
Pigs to human
Mature cysts through
trophozoites and cysts
(Lad diagnosis: stool analysis)
Normally asymptomatic
Only documented discomfort associated: diarrhea
Combi of metronidazole (flagyl) + diloxandie furoate (furamide)
Good sanitation
Personal hygiene
Protect food from food vectors
E. gingivalis life cycle
Transes
E. gingivalis
MOT
INFECTIVE AND DIAGNOSTIC STAGE
LAB DIAGNOSIS
ASSOCIATED DISEASE
TREATMENT
PREVENTION AND CONTROL
Mouth to mouth
Droplet contamination
Trophozoites
Microscopic examination
- mouth scraping from gingival area
- tonsillar cryots and pulmonary abscess
- vaginal and cervica, material
Mouth and genital tract: no symptoms
Recovered from patients suffering pyorrhea alveolar is
Improve oral hygiene
Prompt removal of IUDs in infected patients
Naegleria Fowleri
MOT
INFECTIV STAGE
DIAGNOSTIC STAFE
LAB DOAGNOSIS
ASSOCIATED DISEASE
TREATMENT
Sniffing contaminated water
Contaminated dust
Trophozoites stage
Trophozoites found in CSF
Microscopic examination of CSF
Other specimens: nasal and tissue discharge
Cultured agar plate
PAM, primary a,epic meningoencephalitis
- smell and taste alterations
-vomit
- blocked nose
Kernig’s sign
- inability to fully straighten the leg when the hip is flexed at 90mdegrees
Death occurs 3 to 6 days
Amphotericin B
Amphotericin B with rifampin or miconazole
