Disease causing microorganisms new Flashcards
Are microbes the enemy?
Microbes are not the enemy – less than 1% of them can directly make us ill.
What microbes are healthy?
Human microbiota
Gut microbiota
Probiotics
Prebiotics
What is the human microbiota?
Collective microorganisms that live
on/in the human body
What is the Gut Microbiota?
The collection of microorganisms (bacteria, archaea) which live and thrive in the digestive systems of humans.
think back to ‘gut flora’ – Fecal
transplant (most common phyla in healthy stools –
Bacteroidetes and Firmicutes)
What are Probiotics ?
live bacteria and yeasts promoted as having
various health benefits. They’re usually added to yoghurts or taken as food supplements
What are prebiotics?
The collective name for food components
that can promote the growth of beneficial bacteria.
How can someone be infected without disease?
Cytomegolovirus (CMV) seroprevalence in the adult population of Germany.
People will catch this in early life and will have it for their entire life.
Define pathogen.
A pathogen is an organism that causes a disease to develop in a host. There are many different kinds of pathogens in all shapes and sizes. They include viruses and bacteria as well as many eukaryotes.
Every living organism is affected by pathogens. Bacteria can be targeted by viruses called phages, which some scientists believe may have led to the development of complex life.
When is something an infection?
When pathogenic microbes enter the body and reproduce this is an infection
When is something considered to be a disease?
When the infection causes damage to an organisms function or systems then
this is referred to as disease
What can primary infection lead to?
Primary infection can predispose and lead to chronic or secondary disease.
What has been found to link with EBV?
Risk of multiple sclerosis
What does the Germ theory of disease state?
This theory states that microorganisms can cause disease (pathogens or germs)
what is a microorganism according to the germ theory?
a tiny unseen organism, not visible without magnification,which invade humans and animals which become hosts. They grow and reproduce and cause disease
What is a germ according to the germ theory?
Germ referring to any type of mircroorganism.
What are diseases caused by germs termed as according to the germ theory?
Diseases caused by germs are termed an infectious disease
What were Koch’s experiments?
Kochs Experiments:
Method:
1. Isolate germ
2. Grow it in culture
3. Inject it (into animal for instance)
4. Look for the disease
Types of
Microorganisms?
- Viruses
- Bacteria
- Fungi
- Protozoa
- Algae (blue/green)
- Worms
- Insects (ticks, lice, etc.)
- Prions (a specific type of misfolded
protein)
In what environment are TB symptoms more likely to show?
Lots of vitamin d is associated with suppressing TB infection. TB symptoms are more likely to show in less sunny environments.
What are some symptoms of salmonella?
- Diarrhoea, fever, vomiting, abdominal cramps 12 to 72 hours after infection, dehydration, self limiting gastrointestinal disease.
- In severe cases, Salmonella can move from intestines to bloodstream (aka typhoid fever)
structure of salmonella?
rod-shaped and have flagella so can move
Is salmonella gram positive or gram negative?
gram negative
What type of microbe is salmonella?
bacteria
What were Koch’s Postulates - Identification
of Pathogen causing disease [FULL]
Four generalized principles demonstrating microorganisms cause disease
1. The microorganism must be found in abundance in all organisms
suffering from the disease but should not be found in healthy organisms.
2. The microorganism must be isolated from a diseased organism and
grown in pure culture.
3. The cultured microorganism should cause disease when introduced into
a healthy organism.
4. The microorganism must be re-isolated from the inoculated, diseased
experimental host and identified as being identical to the original specific
causative agent.
Define Kochs postulates in identifying disease causing pathogens?
They were Four generalized principles demonstrating microorganisms cause disease
What is Kochs first principle/postulate?
- The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms.
What is Kochs second principle/postulate?
- The microorganism must be isolated from a diseased organism and
grown in pure culture.
What is Kochs third principle/postulate?
- The cultured microorganism should cause disease when introduced into
a healthy organism.
What is Kochs fourth principle/postulate?
- The microorganism must be re-isolated from the inoculated, diseased
experimental host and identified as being identical to the original specific
causative agent.
WHat has Kochs experimental methods help discover?
Identified specific causative agents of
tuberculosis, cholera, anthrax
What is the threat/danger level of e.coli?
Most E. coli strains are harmless, and some are naturally found in the intestines and microbiome of humans, playing an important role in keeping the intestines healthy.
Structure of e.coli?
rod shaped.
Is e.coli gram positive or gram negative?
Gram negative
Where is e.coli commonly found?
Intestine
Define serotype
A group of microorganisms which have a particular variation which makes them distinguishable from other groups of the same species.
Symptoms of e.coli?
Some serotypes can cause food poisoning
When can e.coli mutliply rapidly and then become dangerous?
In people who are Immunocompromised, malnourished, secondary infections, opportunistic growth.
Define immunocompromised.
weak/underperforming immune system
Define opportunistic growth/opportunistic infections.
Infections that arise due to an abnormally weak immune system because the immune system cannot kill the bacteria quick enough.
Define secondary infection.
An infection which occurs during or following a first infection
What can cause a weak immune system?
Immunocompromised, malnourished, secondary infections, opportunistic growth
What type of microbe is e.coli?
bacteria
How does e.coli help the health of the gut?
- protects us from other harmful microbes.
- forms a biofilm
define self limiting disease.
A disease which runs its course and resolves on its own with or without specific medical intervention.
eg: common cold
What is a disease caused by staphylococci?
Staphylococcal enteritis
Structure of staphylococci?
small, round cocci shape (cocci shape = spherical/roud shape).
What is staphylococci a major cause of?
food poisoning
Symptoms of staphylococci?
Rapid onset (1-8 h), nausea, explosive vomiting, abdominal cramps, headache, diarrhoea
What is the onset of symptoms of staphylococci?
Rapid onset (1-8 h), nausea, explosive vomiting, abdominal cramps, headache, diarrhoea
How long do symptoms of staphylococci last?
Symptoms last for approximately 1 day to 48 h
Describe Staphylococcal enterotoxin
heat stable toxin, resistant to digestive protease
WHat are some treatments of staphylococci?
management of symptoms (electrolyte replacement) avoid foods high in fibre / difficult to digest
What type of microbe is staphylococci?
bacteria
WHat disease is caused by Campylobacter?
Campylobacteriosis
How does Campylobacter enter the body?
faecal-oral route, ingestion of contaminated food / water, raw / undercooked meat
What are some symtptoms of campylobacter?
usually self-limiting, causes diarrhoea, fever, stomach cramps.
Is campylobacter self limiting?
Yes
Treatments for campylobacteriosis/campylobacter?
Its self limiting, so will resolve on its own, most will not need antibiotics.
Management
Drink lots of fluids
Antibiotics for children and for immunocompromised or at risk of systemic infection
What illness does clostridium botulinum cause?
botulism
structure of clostridium botulinum?
rod-shaped spore forming bacteria
How common clostridium botulinum?
rare but serious and potentially fatal
How does clostridium botulinum work?
Blocks neuromuscular junctions → causes paralysis
Where are Clostridium botulinum found?
bacterial spores found in contaminated soil and water and dust.
Can also contaminate dust.
When does the botulinum toxin get produced by Clostridium botulinum?
botulinum toxin produced when exposed to low oxygen levels
What prevents the growth of Clostridium?
A healthy intestinal microbiota will often impede the growth of Clostridium
Who is most at risk of clostridium botulinum ?
Risk for small children
What type of microbe is Clostridium botulinum?
bacteria
what type of microbe is vibrio cholerae?
bacteria.
WHat disease does vibrio cholerae cause?
Cholera
Whats the structure of Vibrio cholerae?
comma-shaped bacteria, gram-negative
is vibrio cholerae gram positive or negative?
gram negative.
How is vibrio cholera spread?
Spread by water and food contaminated with human faeces containing the bacteria
Symptoms of vibrio cholerae?
intense watery diarrhoea for few days, vomiting.
thirst.
leg cramps.
restlessness or irritability.
Most common symptoms of vibrio cholerae?
intense watery diarrhoea for few days
What are some symptoms of Clostridium botulinum?
Difficulty swallowing.
Muscle weakness.
Double vision.
Drooping eyelids.
Blurry vision.
Slurred speech.
Difficulty breathing.
Difficulty moving the eyes.
WHat happens if Vibrio cholerae is uncontrolled?
severe dehydration and electrolyte imbalance
How many deaths are caused by vibrio cholerae per year?
Causes approximately 60,000 to 200,000 deaths / year, developing world (Haiti following
earthquake)
What was Helicobacter pylori. previosuly known as?
previously Campylobacter pylori
How is Helicobacter pylori. spread/transmitted?
Person-to-person transmission by oral-oral or faecal-oral route is most likely
What disease can Helicobacter pylori. cause?
Commonly found in chronic gastritis, gastric and duodenal ulcers, stomach cancer
What percentage of the world is infected with H. Pylori?
Evidence suggetss that approximately 50% of the worlds population is infected with Helicobacter pylori.
Less than 20% of these infected individuals are symptomatic, so wont be aware they are infected with it.
WHat percentage of the population infected with H. Pylori are symptomatic?
Less than 20% of these infected individuals are symptomatic, so wont be aware they are infected with it.
WHat are some symptoms caused by Helicobacter pylori?
Stomach pains, nausea, bloating, belching, vomiting, black stools in rare cases
What are individuals infected with helicobacter pylori at a higher risk of getting?
higher risk of peptic ulcers and stomach cancer
What might helicobacter pylori play a role in?
New evidence suggests it may play a role in immune modulation of stomach
environment
What are some common diseases caused by viruses in our society?
- Influenza: Orthomyxoviridae (influenza virus)
- Measles: Paramyxoviridae family of viruses
- Common cold: Rhinoviruses, Coronaviruses
- Hepatitis: Picornavirus, Hepadnavirus, Hepacivirus, Deltavirus, Hepevirus
- Herpes: Herpes simplex virus 1 and 2 (HSV-1 and HSV-2)
- AIDS: Human immunodeficiency virus
- SARS-CoV-2: Covid-19
Are fungi single celled or multi cellular?
Most fungi are multicellular organisms, However some can be singled celled
organisms such as yeast.
How does fungi obtain its nutrients?
Fungi obtains its nutrients from other complex organic substances.
Most fungus secrete enzymes that break down organic matter and then
absorb the nutrients from it.
What are some common fungal diseases?
▪ Athlete’s foot (Tinea pedis)
▪ Nail infections (Tinea unguium)
▪ Thrush (Candida albicans)
▪ Ringworm (Tinea corporis)
▪ Intertrigo (yeast infection of the skin)
What conditions does genus Trichophyton cause?
Athlete’s foot, ringworm of the foot, tinea pedis
An Opportunistic fungus
What environment does genus Trichophyton thrive in?
Moist and warm environments
How does genus Trichophyton spread?
Contamination: direct and indirect contact, swimming pools, changing rooms,
shower, infected shoes, towels, clothes
Who is at higher risk of genus Trichophyton contamination?
Diabetes and immunocompromised individuals higher risk
How to prevent infection of genus Trichophyton?
Prevention: keep areas clean and completely dry
what fungi causes Dermatophytosis ?
genus Microsporum and Trichophyton
How does someone get Dermatophytosis?
Touching / scratching infected areas (feet) then other parts of the body
How many men are infected with Dermatophytosis compared to women?
Men infected 2 – 4 times more often than women: hygiene(?), sweating
How many adults are infected with Dermatophytosis?
Estimated 1 in 5 adults are affected
What is dermatophytosis?
Fungal skin infection
What types of skin infection can Dermatophytosis cause?
- Tinea Corporis: ringworm of the body – torso or limbs affected
- Tinea Cruris: ringworm of the groin (jock itch or crotch itch) – groin
- Tinea capitis: ringworm of the hair – scalp
Where is candida albicans found?
Common component of humans’ skin, oral and intestinal microbiota
What disease can candida albicans cause if uncontrolled?
Uncontrolled → Candidiasis (thrush)
Example of candidiasis?
Vaginal candidiasis: itching, burning, whitish to grey discharge
When does candida albicans multiply rapidly?
When the host has a weakened immune system. THis makes the fungi and opportunistic fungus.
Who is at particularly high risk of candida albicans?
Opportunistic fungus: weakened immune system
Elderly, HIV/AIDS, poor nutrition, immunosuppressant therapy, diabetes,
prolonged corticosteroid therapy, following antibiotic therapy
What is prion short for?
Short for “proteinaceous infectious particle”
What is a prion?
Infectious agent composed of protein in a misfolded form
How does a prion work?
Induces pre-existing normal forms of a protein to convert to the rogue form. This has a chain reaction, causing many proteins to turn rogue.
How is a prion treated?
Currently untreatable and universally fatal
Can a prion be treated?
No.
Currently untreatable and universally fatal
What are the effects of protein accumulation in the brain?
Protein accumulation in the brain, causes memory impairment, personality
changes, and difficulties with movement.
What happens in bovine spongiform encephalopathy (BSE)?
Spongiform change in the obex (barrier) of the
brain from a clinically affected BSE challenged
deer. Empty vacuoles in both neuronal perikarya (cell bodies) (black arrows), occasionally containing membranous debris, and also the neuropil (network of axons and glial branchings) (red arrows). Haematoxylin & eosin.
What is BSE also known as?
MAD COW DISEASE
mid 1990s
How many cases of Creutzfeldt–Jakob Disease (CJD) per 1 million population per year?
Incidence of approximately 1 case per million population per year
What are the symptoms of CJD?
Psychiatric / behavioural / dementia-like symptoms
Types of prion disease?
- Gerstmann–Sträussler–Scheinker syndrome
- Fatal Familial Insomnia
- Kuru: possibly transmitted through cannibalism in Papua New Guinea
How do u get cjd?
Likely to be caused by eating meat from a cow which had BSE.
WHat species can get bse?
Only cows can get bse
WHat species can get cjd?
Only humans can get CJD.
What protozoan causes amoebiasis, AKA entamoebiasis?
Amoebic dysentery (Entamoeba histolytica)
How is someone infected with Amoebic dysentery (Entamoeba histolytica)?
Contaminated food and water with faeces of infected individuals
Do people have symptoms when infected with Amoebic dysentery (Entamoeba histolytica)?
Many infected individuals are completely asymptomatic
Symptoms of Amoebic dysentery (Entamoeba histolytica)?
Frequent symptoms: abdominal pain, mild diarrhoea, bloody diarrhoea, severe colitis (tissue death and perforation)
How does Amoebic dysentery (Entamoeba histolytica) cause amoebic liver abscesses?
If parasite reaches bloodstream, lodges in liver (amoebic liver abscesses)
How many deaths does Amoebic dysentery (Entamoeba histolytica) cause per year (primary and secondary causes?
Estimated 50,000 to 200,000 deaths / year (primary and secondary causes)
What disease is caused by Giardia lamblia, Giardia intestinalis,
duodenalis?
Giardiasis (beaver fever)
How is someoen contaminated with Giardia lamblia, Giardia intestinalis, duodenalis?
✓ Zoonotic parasitic (direct contact infected animals)
✓ Also contaminated drinking & untreated water, oral-oral, faecal-oral routes
Symptoms of Giardia lamblia, Giardia intestinalis, duodenalis?
Frequent symptoms: weakness, loss of appetite, watery stools, stomach cramps,
vomiting, bloating, sulphurous burping (hydrogen sulfide (H2S) sulfur-containing
proteins)
is Giardia lamblia, Giardia intestinalis, duodenalis self limiting?
Often self-limiting
How is Giardia lamblia, Giardia intestinalis, duodenalis treated?
with Antibiotics
What is the prevalence of Giardia lamblia, Giardia intestinalis, duodenalis in the US?
estimated prevalence of 3–7% in US population
What is an infection?
‘The invasion and growth of a disease-causing
organism in the host’
What must happen in order for an infection to occur?
- For infection to occur the microbes
must enter the body. - Once inside the body they must survive and reproduce!
How can microbes enter the body?
- Respiratory tract
- digestive tract
- Urinal tract
- genital tracts
- Cuts or breaks in the skin
Define Infectivity
the ability of a pathogen to establish an infection
Define Virulence
the severity or harmfulness of a disease or poison
What does infection depend upon?
- Number of infective entities
- Environmental conditions
- Person’s health (their
immunity)
Define antigen.
Any substance that causes your immune system to respond (make an antibody).
Define toxin
a poison of plant or animal origin, especially from microorganisms. Acting as an antigen in the body (living or dead).
Describe endotoxins
They are part of the bacterias cell wall
They are released from a bacteria once the cell wall is compromised and the bacteria dies.
This triggers the immune system
Endotoxins can also be released during spore formation
Describe exotoxins.
- Released by bacteria into the environment
- Polypeptide proteins
- Deliberately released
- Mostly released by gram +ve bacteria.
How does the body fight infection /
foreign invaders?
- Immune system
- Immunity
- Lines of defense
Define the immune system
“The system in the body responsible
for maintaining homeostasis by
recognizing harmful from non-harmful
organisms and producing an
appropriate response”
Define immunity
“The ability of the body to fight
infection and/or foreign invaders by
producing antibodies or killing
infected cells”
What are the three lines of defense?
- Physical and chemical barriers
- Nonspecific ‘innate’ Immune Response
- Specific ‘adaptive’ Immune Response
What are the Physical and chemical barriers (skin)?
Physical – skin - hard to penetrate, indigestible keratin
Chemical – tears, sweat, saliva, mucous
What is the Nonspecific ‘innate’ Immune Response?
– Inflammatory response – caused by release of histamine
- Results in attraction of key immune cells to the site
- Includes; neutrophils, macrophages and Natural killer cells
Phagocytosis –Engulfing (Macrophages)
Release of Oxidants (Neutrophils)
Cytotoxic Killing (Natural Killer cells)
How fast is the innate immune response?
quick
Describe Phagocytosis by neutrophil.
- Phagocytes (such as macrophages or neutrophils) are attracted to molecules produced by pathogens ie bacteria.
- Receptors on phagocyte membranes attaches to pathogen opsonins
- Phagocyte engulfs pathogens
- Pathogens are now in a special vacuole called a phagosome
- Lysosomes move toward phagosome and fuse with it, forming a phagolysosome.
- Lysosomes secrete enzymes which break down the pathogen and destroy it.
WHat is Specific ‘Adaptive’ Immune
Response - Delayed?
An antigen evokes the immune system to respond through an immune
reaction involving:
* Antibody production – B cells
* Cytokine and killing – T cells
What is the role of b cells in specific immune response?
B cell activated by antigen
Proliferates (divides) and differentiates
Makes antigen-specific antibodies.
Define active immunity.
- the body is “actively” producing antibodies to fight infection
define passive immunity.
- Antibodies given to a person from a donor (sort term response)
Examples of passive immunity?
Naturally acquired and artificially acquired
What are examples of naturally acquired passive immunity?
- Maternal antibodies are passed through the placenta to the foetus during
pregnancy - Breastfeeding mothers pass antibodies to their children through the milk
What are some examples of artificially acquired passive immunity?
- Human or animal blood plasma or serum
- Human immunoglobulin from immunized or from donors recovering from the
disease - Monoclonal antibody therapy
Describe humoral response
B lymphocytes have receptors for the detection of its specific antigen;
activation stimulates production of plasma cells, and memory cells;
memory cells remain in the circulation ready to divide if the same antigen is encountered again.
When the antigen is encountered again, many copies of the antibody are produced, which bind to the antigen.
Antibodies are proteins which are specific to a certain antigen with which they bind to form an antigen - antibody complex.
An antigen-antibody complex renders the antigen inactive which increases the rate of engulfment by phagocytes.
Describe Cell-mediated immune response?
T cells recognize infected cells by interacting with antigens present on their molecules, but before a T cell can do so, it must be activated via interaction with an antigen presenting cell.
Once a cytotoxic T cell (TC cells) is activated, it will clone itself, producing many TC cells with the correct receptors. Some of these cells are active and will help destroy infected cells, while others are inactive memory cells that will create more active TC cells if the infection returns.
Helper T cells (TH cells) also aid in the cell-mediated immune response by releasing signalling molecules known as cytokines which can recruit natural killer cells and phagocytes to destroy infected cells and further activate TC cells. TH cells do not directly destroy pathogens.
