Into To Parasite & Bacterial Flashcards
A parasite is an organism that is entirely dependent on another organism, referred to as its host, for all or part of its life cycle and metabolic requirements.
Types of Endoparasites with e.g
Obligate Parasites:
Definition: These parasites cannot survive outside their host. They require a host to complete their life cycle.
Example: Plasmodium species (causes malaria).
Facultative Parasites:
Definition: These parasites can live either as free-living organisms or as parasites. They do not necessarily need a host to survive but can become parasitic if they invade a host.
Example: Acanthamoeba (can cause amoebic keratitis and granulomatous amoebic encephalitis).
Accidental Parasites:
Definition: These parasites infect hosts that are not their usual hosts. This can lead to unusual or severe infections because the parasite is not adapted to the accidental host.
Example: Echinococcus granulosus (typically infects canines but can accidentally infect humans, causing hydatid disease).
Aberrant Parasites:
Definition: These parasites infect a host where they cannot complete their development or life cycle. They typically cannot survive or reproduce in these abnormal hosts.
Example: Toxocara species (usually infects dogs and cats, but can cause toxocariasis in humans, where they cannot complete their life cycle).
Symbiosis
Definition: Symbiosis refers to any type of close and long-term biological interaction between two different biological organisms. In this association, both organisms live together.
Types of Symbiosis:
Mutualism: In this relationship, both organisms benefit from each other. It is advantageous for both parties involved.
Example: The relationship between certain gut bacteria and humans, where bacteria help in digestion, and the host provides nutrients and a habitat.
Commensalism: In this interaction, one organism benefits while the other is neither helped nor harmed. It is a neutral relationship for one party.
Example: Remora fish attach to sharks and eat leftover food from the shark’s meals. The remora benefits while the shark is not significantly affected.
Parasitism: In this type of relationship, one organism (the parasite) benefits at the expense of the other (the host). The parasite derives its benefit by exploiting the host.
Example: The Plasmodium parasite, which causes malaria in humans, benefits by feeding on the host’s blood cells, causing harm to the host.
Reservoir host; This is an animal host serving as a source from which other animals can become infected. Epidemiologically, reservoir hosts are important in the control of parasitic diseases.
A vector is an agent, usually an insect, that transmits an infection from one human host to another.
The term mechanical vector is used to describe a vector which assists in the transfer of parasitic forms between hosts but is not essential in the life cycle of a parasite, e.g. a fly that transfers amoebic cysts from infected faeces to food that is eaten by humans
Let’s break down the concepts of the definitive host and intermediate host with simpler explanations and examples:
Definition: The definitive host is the organism where the parasite undergoes sexual reproduction or reaches its fully mature form.
Key Points:
- The parasite’s sexual reproduction happens in this host.
- If it’s unclear where sexual reproduction happens, the definitive host is usually a mammal.
- This host harbors the adult or sexually mature stage of the parasite.
Example:
- Humans and Malaria: For malaria parasites (Plasmodium species), sexual reproduction occurs in the mosquito (Anopheles), but humans are the definitive hosts because the parasite starts its sexual forms in human red blood cells. So, humans are where the parasite’s mature form is found.
Definition: The intermediate host is the organism where the parasite undergoes asexual reproduction or develops in its larval stages. Some parasites need more than one intermediate host to complete their life cycle.
Key Points:
- The parasite’s asexual reproduction or larval development happens in this host.
- This host alternates with the definitive host in the parasite’s life cycle.
- Some parasites require two intermediate hosts for different developmental stages.
Example:
- Pigs and Tapeworms: In the life cycle of the tapeworm Taenia solium, pigs are the intermediate hosts. The larval stages, called cysticerci, develop in pigs. The definitive host is a human, where the adult tapeworm lives in the intestine.
Some parasites have complicated life cycles that involve multiple intermediate hosts. Each host is crucial for the parasite to go through different developmental stages.
Example:
- Liver Fluke: The liver fluke Fasciola hepatica has a life cycle involving two intermediate hosts: a snail and an aquatic plant. The parasite transitions through different stages in each of these hosts before reaching the definitive host, typically a mammal like a sheep or a human.
Illustration:
Think of it like a relay race:
- Definitive Host: The final runner who crosses the finish line (the parasite reaches maturity or reproduces sexually here).
- Intermediate Host: The runners in the middle who pass the baton (the parasite develops or reproduces asexually here).
By understanding this relay race analogy, you can see how the different hosts play specific roles in the life cycle of a parasite.
Let’s simplify the concepts of reservoir host and vector with easy-to-understand explanations and examples.
Definition: A reservoir host is an animal that carries a parasite and serves as a source from which other animals, including humans, can become infected.
Key Points:
- Acts as a long-term host for the parasite.
- Essential in maintaining the parasite’s life cycle in the environment.
- Important for understanding and controlling the spread of parasitic diseases.
Example:
- Rodents and Plague: Rodents can act as reservoir hosts for the bacteria that cause plague. The bacteria live in the rodents without causing them significant harm, but fleas can transmit the bacteria from the rodents to humans, leading to outbreaks.
Definition: A vector is an agent, typically an insect, that transmits an infection from one host to another.
Key Points:
- Responsible for transferring the parasite between hosts.
- Plays a crucial role in spreading diseases.
- The vector itself may or may not be affected by the parasite.
Example:
- Mosquitoes and Malaria: Mosquitoes act as vectors for malaria. They transfer the Plasmodium parasites from one human to another through their bites.
Definition: A mechanical vector is an agent that transfers parasitic forms between hosts but is not necessary for the parasite’s life cycle.
Key Points:
- Simply aids in the physical transfer of the parasite.
- Does not support the parasite’s development or reproduction.
- Acts like a vehicle transporting the parasite from one place to another.
Example:
- Flies and Amoebic Cysts: A fly that lands on infected feces can pick up amoebic cysts and then transfer them to food. If humans eat this contaminated food, they can become infected. The fly does not play a role in the parasite’s life cycle, but it helps in spreading the infection.
Think of it in terms of different roles in spreading a disease:
- Reservoir Host: Like a storage place where the parasite lives and can infect others (e.g., rodents storing plague bacteria).
- Vector: Like a delivery person who picks up the parasite and delivers it to new hosts (e.g., mosquitoes delivering malaria parasites).
- Mechanical Vector: Like a taxi driver who gives a ride to the parasite without changing it (e.g., flies carrying amoebic cysts to food).
By understanding these roles, we can better comprehend how parasites spread and how to control their transmission.
Sure, let’s create some mnemonics to help remember the classification of parasites. We’ll break it down by the major groups and their key members.
Amoebae (Sarcodina):
1. Entamoeba histolytica
2. Acanthamoeba species
3. Naegleria species
Mnemonic: Every Amoeba Navigates.
Flagellates (Mastigophora):
1. Giardia lamblia
2. Trichomonas vaginalis
3. Trypanosoma species
4. Leishmania species
Mnemonic: Girls Talk Too Loudly.
Ciliates:
1. Balantidium coli
Mnemonic: Balanced diet for ciliates.
Coccidia (Sporozoa):
- Blood and tissue coccidia:
1. Plasmodium species
2. Toxoplasma gondii
- Intestinal coccidia:
1. Isospora belli
2. Cryptosporidium parvum
3. Cyclospora cayetanensis
Mnemonic: Professors Teach Interesting Cellular Courses.
Microsporidia:
1. Encephalitozoon species
2. Enterocytozoon species
Mnemonic: Expert Educators.
Trematodes (Flukes):
1. Schistosoma species
2. Paragonimus species
3. Fasciolopsis buski
4. Fasciola hepatica
5. Opisthorchis (Clonorchis) sinensis
6. Opisthorchis viverrini
- Lesser medical importance:
1. Metagonimus yokagawai
2. Heterophyes heterophyes
3. Dicrocoelium dendriticum
Mnemonic: Super Professors Find Fantastic Organisms Often. Lesser known: Minor Helminths Discovered.
Nematodes (Roundworms):
- Intestinal nematodes:
1. Ascaris lumbricoides (large roundworm)
2. Enterobius vermicularis (threadworm)
3. Trichuris trichiura (whipworm)
4. Strongyloides stercoralis
5. Ancylostoma duodenale (hookworm)
6. Necator americanus (hookworm)
- Filarial and other tissue nematodes:
1. Wuchereria bancrofti
2. Brugia species
3. Loa loa
4. Onchocerca volvulus
5. Drancunculus medinensis (Guinea worm)
6. Trichinella species
Mnemonic: Active Explorers Travel Safely Across Nations. Wandering Beyond Limits Often Discovers Treasures.
Cestodes (Tapeworms):
1. Taenia species
2. Echinococcus granulosus (larvae)
3. Diphyllobothrium latum
4. Vampirolepis nana (less important)
Mnemonic: Terrific Examples Demonstrate Versatility.
All Funny Cats Caught Mice. Too Numerous Cats.
Amoebae
Flagellates
Ciliates
Coccidia
Microsporidia
Trematodes
Nematodes
Cestodes
These mnemonics can help you recall the various groups and specific parasites within them. Repetition and visualization (e.g., drawing simple pictures) can also enhance memory retention.
Direct life cycle
When a parasite requires only one species of host in
which to complete its development it is said to have
a direct life cycle. Important parasites in humans that
have a direct life cycle include:
Every Student Gets Top Academic Awards Each Night.
Every - Entamoeba histolytica
Student - Strongyloides stercoralis
Gets - Giardia lamblia
Top - Trichuris trichiura
Academic - Ascaris lumbricoides
Awards - Ancylostoma duodenale
Each - Enterobius vermicularis
Night - Necator americanus
Indirect life cycle
When two or more species of hosts are required, the
life cycle is referred to as indirect. Examples of parasites
that have an indirect life cycle include:
Plasmodium species O. volvulus
Trypanosoma species P. westermani
Leishmania species Schistosoma species
W. bancrofti Taenia species
B. malayi F. buski
L. loa D. latum
Sure, let’s break down the life cycle of parasites and the laboratory diagnosis of parasitic infections/infestations for easier understanding.
-
Cysts Ingested:
- Parasite cysts are ingested by humans through contaminated food, water, or hands that have come into contact with feces.
-
Excystation in the Host:
- Once inside the human host, the cysts excyst (release the active form of the parasite called trophozoites) in the intestine.
-
Multiplication:
- These trophozoites multiply within the host’s intestine.
-
Encystation:
- The trophozoites then encyst again (transform back into cysts) within the intestine.
-
Excretion:
- These new infective cysts are passed out of the body through feces.
- Note: Trophozoites that are passed in feces disintegrate and are not usually infective.
-
Contamination:
- Feces containing the infective cysts contaminate the environment, potentially infecting new hosts and continuing the cycle.
- Stool: The most common specimen for diagnosing intestinal parasites.
- Urine: Used for diagnosing parasites that may infect the urinary tract.
- Skin Snip: A small piece of skin is taken to diagnose certain skin parasites.
- Blood: Used for detecting blood-borne parasites.
- Rectal Swab/Biopsy: For parasites that reside in or affect the rectum.
- Corneal Scraping: For diagnosing eye parasites.
- Others: Various other specimens may be required depending on the suspected parasite.
-
Stool Examination:
- Wet Mount Preparations: Using iodine and saline to detect cysts and trophozoites under a microscope.
-
Antigen Detection in Stool (Copro-antigen):
- ELISA: Enzyme-Linked Immunosorbent Assay, a test that uses antibodies and color change to identify a substance.
- ICT: Immunochromatographic Test, a quick diagnostic test.
-
Entero-test:
- A method to collect duodenal material to test for parasites.
-
Antibody Detection in Serum:
- ELISA: Tests for the presence of specific antibodies in the blood.
- IFA: Immunofluorescence Assay, a test that uses antibodies tagged with a fluorescent dye.
-
Culture:
- Growing the parasite in a controlled environment to identify it.
-
Molecular Methods:
- PCR: Polymerase Chain Reaction, a method to amplify DNA and detect specific genetic material of the parasite.
-
Radiological Findings:
- Barium Meal: A radiographic (X-ray) examination of the gastrointestinal tract.
- X-ray: Imaging to detect changes in organs affected by parasites.
Parasite life cycles involve transmission through ingestion of cysts, excystation, multiplication, encystation, and excretion, leading to environmental contamination and further infection. Diagnosis involves various specimen collections and methods, from microscopic examination to advanced molecular techniques.
Bacteria
Cellular world can be divided into two types, depending on the presence of nuclei inside cells.
Eukaryotic cells have a well-defined nucleus surrounded by a nuclear envelope, whereas
Prokaryotic cells lack this compartment.
Bacteria are prokaryotes
Fungi and parasite are eukaryotes
Differences between prokaryotic & Eukaryotic cells
Ribosome size
Cell wall c
& membrane composition except
Mitotic division
DNA associated with his time
Number of chromosome
Number of cell & cell size
Sure, let’s break down the bacterial classification, focusing on Gram-positive and Gram-negative bacteria, and their shapes, for easier understanding.
Cocci (Spherical-shaped bacteria)
- Clusters:
- Staphylococci: These bacteria typically form grape-like clusters.
- Pairs and Chains:
- Streptococci: Form chains or pairs.
- Enterococcus species: Also form chains or pairs.
Bacilli (Rod-shaped bacteria)
- Listeria monocytogenes: A type of rod-shaped bacteria.
- Bacillus species: Rod-shaped bacteria.
- Corynebacterium species: Rod-shaped bacteria.
- Nocardia species: Filamentous, branching rods that are weakly Gram-positive.
Cocci (Spherical-shaped bacteria)
- Moraxella catarrhalis
- Neisseria gonorrhoeae
- Neisseria meningitidis
Coccobacilli (Short, rod-shaped bacteria)
- Haemophilus influenzae
- Acinetobacter species
Bacilli (Rod-shaped bacteria)
- Enterobacteriaceae Family:
- Escherichia coli (E. coli)
- Enterobacter species
- Citrobacter species
- Klebsiella species
- Proteus species
- Serratia species
- Salmonella
- Shigella
- Pseudomonas aeruginosa
- Burkholderia pseudomallei
- Non-fermentative Gram-negative Bacilli (GNB)
-
Coccus: Spherical-shaped bacteria.
- Examples: Staphylococci, Streptococci
-
Coccobacillus: Short, rod-shaped bacteria.
- Examples: Haemophilus influenzae
-
Vibrio: Comma-shaped bacteria.
- Example: Vibrio cholerae
-
Bacillus: Rod-shaped bacteria.
- Examples: E. coli, Klebsiella
-
Spirillum: Spiral-shaped bacteria.
- Examples: Helicobacter pylori, Campylobacter jejuni
-
Spirochete: Corkscrew-shaped bacteria.
- Example: Treponema pallidum (causes syphilis)
-
Bacterial Shapes:
- Bacteria are classified based on their shape: cocci (spherical), bacilli (rod-shaped), coccobacilli (short rods), vibrio (comma-shaped), spirillum (spiral-shaped), and spirochete (corkscrew-shaped).
-
Gram Staining:
- Bacteria are further classified into Gram-positive and Gram-negative based on the Gram staining technique. This technique differentiates bacteria by the composition of their cell walls.
-
Gram-Positive Bacteria:
- Cocci: These include Staphylococci (in clusters), Streptococci, and Enterococcus species (in pairs and chains).
- Bacilli: These include Listeria monocytogenes, Bacillus species, Corynebacterium species, and Nocardia species.
-
Gram-Negative Bacteria:
- Cocci: Examples are Moraxella catarrhalis, Neisseria gonorrhoeae, and Neisseria meningitidis.
- Coccobacilli: Examples are Haemophilus influenzae and Acinetobacter species.
- Bacilli: Include a broad range of bacteria such as those in the Enterobacteriaceae family (e.g., E. coli, Klebsiella species), Pseudomonas aeruginosa, Burkholderia pseudomallei, and other non-fermentative Gram-negative bacilli.
This logical flow outlines how bacteria are classified by their shape and Gram-staining characteristics, and provides examples of each type.
Gram stain invented by Hans Christian Gram 1884
Divides Eubacteria into two main groups based on stain
Correlates with two types of cell wall architecture
