Protozoan microorganisms Flashcards
Parasites
1) Prokaryotic cells
Bacteria/Archea
2) Eukaryotic cells
Fungi (yeasts/moulds)
Parasites (protozoa/helminth, ectoparasites)
3) Acellular structures
(not made of cells)
Viruses
Prions
Define Parasite;
living eukaryote organism, which takes its nourishment and other needs from a host. Depends on the host for nutrition
ENDOparasites
nside of the host’s body - Permanently
Some anaerobes, some aerobes
Protozoa and helminths
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 - Protozoa
Monocellular
Mostly asexual reproduction (most by binary fission), and sexual reproduction
some are non-motile, those motile use either flagella or cilia
Endoparasites (Protozoa vs helminths) - Helminths
Pluricellular, Parasitic worms (usually visible)
Sexual reproduction
Sexual reproduction
What are the general characteristics of protozoa?
Ranging in size - 2-100 μM
All protozoa are chemoheterotrophs
preformed organic substances
Similar requirements of the mammalian cells
Require HIGH moisture
Diverse oxygen requirements
Establish parasitic relationships with many hosts
Life Cycle Stages
Some protozoa (e.g. Giardia intestinalis, an intestinal protozoal parasite) exist in two morphological forms/stages:
1) Trophozoite
2) Cyst
1) Trophozoite
Motile, vegetative (active) form
Actively feed and multiply
Pathogenic form
2) Cyst
External, non-parasitic form
Possess a protective membrane or thickened wall (survival outside the host)
Means of transfer between hosts
Transmission of intestinal protozoa
Transmission of intestinal protozoa that live in a human’s intestine to another human typically occurs through a fecal-oral route
Contaminated food
Contaminated water
Domestic pets
Sewage/waste water
What is the process of intestinal protozoa?
- contamination of foods, water, hands with infective cysts
- cysts ingested
[cysts > trophozoites = Giardia mature and x in gut]
- infective cysts passed in stool / trophozoites are passed in stool but they do not survive in the environment
Medically relevant protozoa – motality classification
protozoan infections can be inapparent/mild in normal individuals, yet life-threatening in immunosuppressed patients (e.g. AIDS).
Classified by their motile form = portozoa
Amoebae - amoeboid movement (temporary extensions of the plasma membrane)
Flagellates - use flagella
Ciliates - use cilia
Sporozoa - Non motile, spore-producing protozoa
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
Flagellates
Possess one or more flagella for locomotion and sensation
they incl.
Intestinal and genito-urinary flagellates (e.g. Giardia and Trichomonas)
Blood and tissue flagellates (Trypanosoma and Leishmania)
Transmission of blood borne protozoa- Leishmania
Leishmania spp. parasitise - in mononuclear phagocytic cells
Leishmania protozoa - usually spread through the bite of infected sand flies
Transmission of blood borne protozoa- step by step:
1) sandfly take a blood meal
2) Human - promastifotes are phacoytized by macrophages other types of monocular phygocytic cells
3) Promastigotes transform into amastigotes
4) Amastigotes multiply in cells of various and infect other cells
5) Sandfly takes a blood meal
6) Ingestion of parasitised cell
7) Amastigotes transform into promastigote stage in gut
8) Divide in gut and migrate to proboscis
Leishmaniasis
Cutaneous leishmaniasis - affects the skin (skin ulcers)
Mucosal leishmaniasis - affects the mucous membranes of the nose and mouth, causing sores and destroying tissues
Visceral leishmaniasis - affects the internal organs, particularly the bone marrow, lymph nodes, liver, and spleen
Trichomoniasis
Lower genital tract infections
Caused by infection of Trichomonas vaginalis
Common sexually transmitted disease (STD)
Chlamydia, Gonorrhoea (bacteria)
Genital herpes, AIDS (viruses, i.e. HSV and HIV)
Various human papilloma virus infections
Ciliates
Complex protozoa that move by cilia (hair-like organelles) distributed in rows or patches
flagella in which cell? (hair like tail - swim)
Spermatozoa
Sperm cell
Types of nuclei - ciliates:
Human apthogen - Balantidium coli
Transmitted through infected pigs
Also oral-fecal transmission
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)
Sporozoa - 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
Plasmodium species - malaria
Plasmodium
= agent for malaria
the major and most deadly protozoa-causing
[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 of Plasmodium:
Spread to humans by the bite of female mosquitoes of the genus Anopheles
Blood transfusions
Mother to fetus
Malaria
Around 250 million new cases and 1 – 2.5 million deaths each year
Endemic (disease constantly present at a constant level)
Acute febrile illness
Symptoms after 10-14 days from mosquito’s bite
Serious complications may occur
cerebral malaria
severe anaemia
Malaria and Life Cycle of Plasmodium
1) Mosquito Anopheles bite
2) Sporozoites
3) Infected hepotocyte
Hepatic schizont
Ruptured schizont {all in liver}
4) Merozoites
early/ late trophozoite, blood stage
5) Gametocyte
What is the vector of the protozoa that causes Malaria?
Female Mosquitos Anopheles
Control of malaria - prevention, vaccine?
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%)
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
How many weeks do you have to take malaria tablets after leaving country?
4 weeks
50% Diethyltoluamide (DEET),
Personal protection against bites (Insect repellents, covering clothes, nets)
Antiprotozoal drugs
- Unicellular eukaryotes = less easily treated than bacterial infections
- most antiprotozoan drugs is not completely elucidated
- antiprotozoal drugs cause serious toxic effects in the host (e.g. Mefloquine)
- most are unsafe for pregnant women
What are the Principles of microorganisms identification?
- Study growth of biochemical characteristics of isolated microorganisms - PURE cultues for bacteria, fungal cells, virus cultivation
- Immunologic tests - detected antibodies or microbial antigens/proteins = detect presence microbial protein/antigen in a sample using antibodies directed against the protein
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
