Podcast
Questions and Answers
Which of the following parasites is always found in a cyst stage once it enters a human?
Which of the following parasites is always found in a cyst stage once it enters a human?
Which of the following parasites is typically found in warm freshwater environments?
Which of the following parasites is typically found in warm freshwater environments?
What is the most common way for Naegleria fowleri to enter a human host?
What is the most common way for Naegleria fowleri to enter a human host?
Which of the following parasites is known to cause granulomatous amebic meningoencephalitis?
Which of the following parasites is known to cause granulomatous amebic meningoencephalitis?
Signup and view all the answers
Which of the following parasites is associated with contact lens wearers?
Which of the following parasites is associated with contact lens wearers?
Signup and view all the answers
Which of the following statements about Acanthamoeba spp. is TRUE?
Which of the following statements about Acanthamoeba spp. is TRUE?
Signup and view all the answers
What is a distinguishing characteristic of Balamuthia?
What is a distinguishing characteristic of Balamuthia?
Signup and view all the answers
Which of the following parasites can exist as both ameboid and flagellated forms?
Which of the following parasites can exist as both ameboid and flagellated forms?
Signup and view all the answers
Which of these protozoa are NOT classified as amebas?
Which of these protozoa are NOT classified as amebas?
Signup and view all the answers
Which of the following statements about Entamoeba histolytica is TRUE? (Select all that apply.)
Which of the following statements about Entamoeba histolytica is TRUE? (Select all that apply.)
Signup and view all the answers
What is the average size of a mature Balantidium coli cyst?
What is the average size of a mature Balantidium coli cyst?
Signup and view all the answers
Which of these statements about Balantidium coli is FALSE?
Which of these statements about Balantidium coli is FALSE?
Signup and view all the answers
What is the most common mode of transmission for Balantidium coli?
What is the most common mode of transmission for Balantidium coli?
Signup and view all the answers
What is a key difference between the trophozoite and cyst stages of Balantidium coli?
What is a key difference between the trophozoite and cyst stages of Balantidium coli?
Signup and view all the answers
Which of these features is NOT a characteristic of a Balantidium coli trophozoite?
Which of these features is NOT a characteristic of a Balantidium coli trophozoite?
Signup and view all the answers
Which of the following diseases is caused by Balantidium coli?
Which of the following diseases is caused by Balantidium coli?
Signup and view all the answers
Which of the following amoebas is considered pathogenic and can cause severe disease?
Which of the following amoebas is considered pathogenic and can cause severe disease?
Signup and view all the answers
What is the primary mode of transmission for intestinal protozoa, including amebas?
What is the primary mode of transmission for intestinal protozoa, including amebas?
Signup and view all the answers
What distinguishes the trophozoite stage of an ameba from the cyst stage?
What distinguishes the trophozoite stage of an ameba from the cyst stage?
Signup and view all the answers
What is the primary factor that triggers encystation in amebas?
What is the primary factor that triggers encystation in amebas?
Signup and view all the answers
Which of the following characteristics is NOT used to distinguish between different amebas in stool samples?
Which of the following characteristics is NOT used to distinguish between different amebas in stool samples?
Signup and view all the answers
Which amoeba is commonly found in the oral cavity and is associated with periodontal disease?
Which amoeba is commonly found in the oral cavity and is associated with periodontal disease?
Signup and view all the answers
What is the primary method of replication in the trophozoite stage of an ameba?
What is the primary method of replication in the trophozoite stage of an ameba?
Signup and view all the answers
What are chromatoid bodies and how are they formed in amebas during encystation?
What are chromatoid bodies and how are they formed in amebas during encystation?
Signup and view all the answers
Which of the following is a characteristic that differentiates Entamoeba histolytica from Entamoeba dispar?
Which of the following is a characteristic that differentiates Entamoeba histolytica from Entamoeba dispar?
Signup and view all the answers
A person presents with unexplained diarrhea and a stool sample reveals the presence of trophozoites with a single nucleus, a prominent central karyosome, and ingested red blood cells. Which amoeba is most likely the culprit?
A person presents with unexplained diarrhea and a stool sample reveals the presence of trophozoites with a single nucleus, a prominent central karyosome, and ingested red blood cells. Which amoeba is most likely the culprit?
Signup and view all the answers
Study Notes
Amebae
- Amebae are single-celled eukaryotic organisms.
- They are classified within the subphylum Sarcodina, class Lobosea.
- Intestinal species and extraintestinal species are further subdivisions.
Classification
- Subphylum: Sarcodina
- Class: Lobosea
- Intestinal Species: Entamoeba histolytica, Entamoeba hartmanni, Entamoeba coli, Entamoeba polecki, Endolimax nana, Iodamoeba bütschlii
- Extraintestinal Species: Entamoeba gingivalis, Naegleria fowleri, Acanthamoeba species
Intestinal/Lumen-Dwelling Protozoa
- Numerous protozoa inhabit the human gastrointestinal tract.
- Most protozoa are non-pathogenic, causing mild disease in commensals
- Pathogenic protozoa cause severe disease.
- Transmission often occurs via the fecal-oral route, ingesting contaminated food or water containing cysts.
Intestinal Protozoa: Life Cycle
- Mature cysts are ingested.
- Excystation occurs in the lower ileum.
- Trophozoites multiply via binary fission.
- Encystation occurs under unfavorable conditions.
- Cysts are excreted in feces.
Encystation
- Occurs when the environment is unfavorable for trophozoite reproduction (overpopulation, pH change, lack of nutrients, lack of oxygen).
- Trophozoites become spherical, 12-15 μm in diameter.
- Ribosomes aggregate to form elongated chromatoid bodies.
- Maturation involves two rounds of nuclear division; chromatoid bodies disappear.
- Excreted cysts are infective and viable for weeks to months depending on conditions.
Trophozoite Stage
- Trophozoites are actively growing, reproducing forms of the parasite.
- They are motile and fragile.
- Multiplication occurs via asexual binary fission.
- Trophozoites can be differentiated from cysts by microscopic analysis.
Intestinal Protozoa: Symptoms/Diagnosis
- Most ameba infections are asymptomatic.
- Common symptom is unexplained diarrhea.
- Diagnosis involves finding trophozoites and/or cysts in stool samples.
- Identifying characteristics include organism size, number and location of nuclei, cytoplasmic inclusions, and motility.
- Permanent stains facilitate visualization of microscopic structures.
Entamoeba histolytica
- A species which can become pathogenic leading to illness
- Transmission via ingestion of contaminated cysts in food or water.
- It leads to lethal systemic diseases.
- Trophozoites exhibit active metabolism.
- Reproduction and nutrient uptake occur in the trophozoite stage.
- Humans are the only definitive host.
- Characterized by amorphous shape.
- Trophozoite size ranges from 8-65 μm (average 12-25 μm).
- Cysts range from 12-18 μm.
- They move rapidly via pseudopodia.
Entamoeba histolytica: Modes of Transmission
- Hand-to-mouth infection (ingestion of cyst stage)
- Food/water contamination
- Unprotected sex
- Vectors (flies and cockroaches)
Entamoeba histolytica: General Characteristics (Cont'd)
- Nucleus has a small, central karyosome.
- Peripheral chromatin is fine and evenly distributed around nucleus.
- Nucleus is invisible to the naked eye until stained.
- The presence of red blood cells in the cytoplasm is a distinguishing feature.
Entamoeba histolytica Pathology:
- Infection can result in intestinal inflammation, ulcers, or abscesses.
- Extraintestinal lesions can occur in the liver (hepatic amebiasis), lungs (pulmonary amebiasis), or brain (cerebral amebiasis).
Amebiasis
- An estimated 50 million cases worldwide per year.
- Up to 100,000 deaths yearly.
- Third leading cause of parasitic deaths.
- Associated with long-term (> 1 month) residence in endemic regions.
Amebiasis (Cont'd)
- On average, one in 10 people infected with Entamoeba histolytica becomes ill (causes intestinal amebiasis)
- Asymptomatic cases arise from low parasite virulence, low host inoculation.
- Symptoms such as diarrhea, stomach pain, cramping, and colitis are common.
- Severe cases can involve amebic dysentery (bloody stools, stomach pain, fever)
- In rare cases, invasion of the bloodstream can result in liver abscesses (extraintestinal amebiasis).
- Diagnosis is typically serological unless trophozoites re-enter bloodstream.
Amebiasis (Cont'd)
- Infection can spread to other body parts (lungs or brain) in less frequent cases.
Amebiasis: Presentation and Diagnosis
- Symptoms typically appear 1-4 weeks post infection.
- Diagnosis is challenging due to similar morphology of other cells/parasites.
- Diagnosis is often misdiagnosed.
- Analysis of stool samples (and possible blood if intestinal penetration), staining, and wet mounts can assist in diagnosis..
Entamoeba coli
- A commensal, non-pathogenic ameba.
- Larger than Entamoeba histolytica (20-30 µm diameter); larger cysts (10-33µm).
- Primarily feeds on bacteria and other available cellular material.
- Does not invade tissues.
- Distinguished by granular instead of fine endoplasm.
Naegleria fowleri
- Found in warm freshwater environments.
- The life cycle includes cysts, trophozoites and flagellated forms.
- People can be infected through water-related activities and the parasite enters through the nose.
- The parasite migrates to the brain along the olfactory nerves, resulting in primary amebic meningoencephalitis.
Acanthamoeba spp.
- At least 5 species identified, are free-living in soil and freshwater.
- Trophozoites are ameboid forms.
- Known to cause keratitis in contact lens users.
Balantidium coli
- The largest protozoan; 28–152 µm, but average 35-50
- Exists in trophozoite and cyst forms.
- Trophozoite has cilia, and is ovoid to sac-shaped.
- Tapers at the anterior end and contains two nuclei.
- Cysts are 52-55 µm, spherical or oval in shape.
- Contain 1-2 vacuoles; mature cysts lose cilia.
- Transmission through contaminated food, water, or via fecal-oral/person-person routes
- Common symptoms are mild colitis, diarrhea (possible pus, mucus, blood), and abscesses. Can invade other organs including the liver, lungs or urogenital tract.
Pneumocystis carinii
-
Cysts range from 3.5 to 7 µm with 4 to 8 nuclei (1-2 µm in size); varies on size.
-
Trophozoites are 1-5 µm in size.
-
Life cycle not fully understood.
-
Believed to infect alveolar spaces in the lungs.
-
Mature cyst ruptures releasing trophozoites.
-
May infect other locations such as spleen, lymph nodes, and bone marrow.
-
Commonly transmitted through person-to-person contact via exhaled droplets; can also be transmitted through the placenta resulting in still births.
-
Most at risk are immunocompromised persons (e.g., AIDS) or young children.
-
Respiratory symptoms (pneumonia) such as a non-productive cough, fever, rapid breathing, and cyanosis (bluish tint) are potential indicators.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz explores the classification of amebae, focusing specifically on the subphylum Sarcodina and class Lobosea. It covers both intestinal and extraintestinal species, their life cycle, and the implications of pathogenic protozoa. Test your knowledge on these fascinating single-celled organisms!
