W21 Protozoan microorganisms Flashcards
What is a parasite?
Parasite - living eukaryote organism, which takes its nourishment and other needs from a host. Depends on the host for nutrition.
e.g. protozoa/helminth/ectoparasites
What are Endoparasites?
- Inside of the host’s body - Permanently
- Some anaerobes, some aerobes
-Protozoa and helminths
What are Ectoparasites?
- ON the outer surface of the host’s body – temporary or permanent
- Aerobes
- Some ectoparasites serve as vectors of pathogens
-ticks, fleas, lice, and mites
Endoparasites:
What are protozoa?
- Monocellular
- Pluricellular, Parasitic worms (usually visible)
- Mostly asexual reproduction (most by binary fission), and sexual reproduction
- Some are non-motile, those motile use either flagella or cilia
Endoparasites:
What are Helminths:
- Pluricellular, Parasitic worms (usually visible)
- Sexual reproduction
- Move through muscular contractions
What are some characteristics of protozoa?
- Ranging in size - 2-100 μM
- Require high moisture environments
- Diverse oxygen requirements
- All protozoa are chemoheterotrophs
-preformed organic substances
-Similar requirements of the mammalian cells - Establish parasitic relationships with many hosts
What are the 2 morphological forms/stages of of some protozoa? (for info)
- Trophozoite
* Motile, vegetative (active) form
* Actively feed and multiply
* Pathogenic form - Cyst
* External, non-parasitic form
* Possess a protective membrane or thickened wall
(survival outside the host)
* Means of transfer between hosts
How are intestinal protozoa transmitted? (4)
Through the fecal-oral route
Such as by:
* Contaminated food
* Contaminated water
* Domestic pets
* Sewage/waste water
e.g. Inadequate sanitation and poor hygiene practices
What are the Medically relevant protozoa? (4)
– motility classification
- Many protozoan infections can be inapparent/mild in normal individuals, yet life-threatening in immunosuppressed patients (e.g. AIDS).
- Many move to various sites within the body
- Classified by their motile form
- Amoebae - amoeboid movement (temporary extensions of the plasma membrane)
- Flagellates - use flagella
- Ciliates - use cilia
- Sporozoa - Non motile, spore-producing protozoa
What are amebae?
- Move by extending pseudopods (Arm-like projection of the cell membrane)
- Engulf food with pseudopods and phagocytize
-Entamoeba histolytica - feeds on red blood cells
What are flagellates?
What do they include? (2) (different types)
- Possess one or more flagella for locomotion and sensation
- Intestinal and genito-urinary flagellates (e.g. Giardia and Trichomonas)
- Blood and tissue flagellates (Trypanosoma and Leishmania)
Transmission of blood borne protozoa- Leishmania
- In humans, Leishmania spp. parasitise in mononuclear phagocytic cells (macrophages, monocytes)
- Leishmania protozoa are usually spread through the bite of infected sand flies
What are the types of Leishmaniasis?
Leishmaniasis produces a spectrum of diseases
1. Cutaneous leishmaniasis - affects the skin (skin ulcers)
2. Mucosal leishmaniasis - affects the mucous membranes of the nose and mouth, causing sores and destroying tissues
3. Visceral leishmaniasis - affects the internal organs,particularly the bone marrow, lymph nodes, liver, and spleen
What is Trichomoniasis? (for info)
What are some examples of STI’s?
- Lower genital tract infections
- Caused by infection of Trichomonas vaginalis
- Common sexually transmitted disease (STD)
Other STDs examples:
- Chlamydia, Gonorrhoea (bacteria)
- Genital herpes, AIDS (viruses, i.e. HSV and HIV)
* Various human papilloma virus infections
What are Cilliates?
- Complex protozoa that move by cilia (hair-like organelles) distributed in rows or patches
- Only known human pathogen is Balantidium coli – causing in severe intestinal infection – dysentery in some cases
- Unusually, they have two different types of nuclei
Transmitted through infected pigs
Also oral-fecal transmission
What are sporozoa?
- Do not have any locomotory extensions
- Complex life cycles
Alternating sexual and asexual reproduction, also involving spores
Usually, they have more than one host (definitive and intermediate hosts) - Intracellular parasites
Cryptosporidium - diarrheal disease cryptosporidiosis
Cyclospora - intestinal illness
Toxoplasma – usually mild flu-like illnesses (humans are the intermediate host, cats
are the definitive hosts). In pregnancy, Toxoplasmosis can cause miscarriages.
Plasmodium species - Malaria
What are plasmodium?
How are they transmitted? (3)
- Agent responsible for malaria – the major and most deadly protozoa-causing
disease - Obligate intracellular parasite – sporozoan
- 4 species responsible – P. malariae, P. vivax, P. falciparum and P. ovale
- P. falciparum causes the most severe disease and is the most common
Transmission
* Spread to humans by the bite of female mosquitoes of the genus Anopheles
* Blood transfusions
* Mother to fetus
What is malaria?
- Around 250 million new cases and
1 – 2.5 million deaths each year - Endemic (disease constantly present at
a constant level) in tropics – subtropic
countries with a temperate climate - Serious complications may occur
cerebral malaria
severe anaemia - Acute febrile illness
Symptoms after 10-14 days from mosquito’s bite
How is malaria controlled?
- One vaccine (RTS,S) available showing modest efficacy, preventing about 30% of severe malaria cases
- Drugs to prevent malaria (prophylaxis, reducing the risk of malaria of 90%) before travel into an endemic area until 4 weeks after leaving the area
Atovaquone plus proguanil – started 1-2 days before the travel
Doxycycline (Vibramycin-D) – started 1-2 days before the travel
Mefloquine (Lariam) – started 2-3 week before the travel
Chloroquine and proguanil – started 1 week before the travel - Personal protection against bites (Insect repellents, covering clothes, nets)
50% Diethyltoluamide (DEET), - Environmental mosquito control (destruction of larvae by environmental management)Control of malaria
Antiprotozoal drugs
- Protozoal diseases are no longer confined to specific
geographic locales - Unicellular eukaryotes, less easily treated than bacterial infections
- The mechanism of drug action for most antiprotozoan drugs is not completely elucidated
- Many of the antiprotozoal drugs cause serious toxic effects in the host (e.g. Mefloquine)
- Most antiprotozoal agents have not proven to be safe for pregnant patients.
What are some principles of microorganisms identification
(methods)
- Microscopic examination to identify the morphology of microbes in specimens,
- Study of the growth and biochemical characteristics of isolated microorganisms (pure cultures for bacteria and fungal cells, virus cultivation, specific biochemical tests based on the properties of the microbe)
- Immunologic tests that detect antibodies or microbial antigens/proteins (e.g. ELISA
tests, Later Flow Tests)
To detect the presence of a microbial protein/antigen in a sample using antibodies directed against the protein (highly specific) linked to enzymes, or vice versa - Molecular methods (detecting the specific genome of a certain microorganism)
Polymerase Chain Reaction (PCR) based techniques allow amplification of a known gene of interest (based on unique sequence of nucleotide)
nucleic acid sequencing
