Module 5 Flashcards
1
Q
Infections and infectious diseases?
A
Infections and infectious diseases are caused by infectious agents or microbes
Infection: The invasion of infectious agents into an organism, their multiplication, and the reaction of host tissues to the infectious agents.
Infectious disease: Diseases that are caused by pathogenic microbes that can be spread from the environment to a person, or from person to person.
2
Q
What are microbes?
A
Microbes are the most abundant and diverse forms of life on earth, yet they can be grouped into specific types based on key features
- 4 main groups of microbes: bacteria, viruses, fungi and parasites
3
Q
Bacteria?
A
- Microscopic unicellular organisms
- Prokaryotes (unicellular, lack membrane bound organelles or structure)-> genetic information is carried by a double-stranded circular DNA
Have cell walls outside their plasma membranes
- Prokaryotes (unicellular, lack membrane bound organelles or structure)-> genetic information is carried by a double-stranded circular DNA
4
Q
Viruses?
A
- Obligate microbes: they must invade a host cell and depend on the host’s machinery to replicate itself
- DNA or RNA based genomes
- Encapsulated by a protein coat
- They infect all forms of life: bacteria, plants and animals
- Certain viral proteins serve to infect specific host cell types
5
Q
Fungi?
A
- Unicellular or multicellular eukaryotes
- Thick cell walls made of complex carbohydrates structures
Cause superficial infections of the skin or nails, or invade tissues and organs
- Thick cell walls made of complex carbohydrates structures
6
Q
Parasites?
A
- Eukaryotes that cause disease in their host
- Single-celled protozoa that can replicate within cells, helminths parasitic worms and even insects or arachnids
Ectoparasites, live outside the host and may serve as vectors for other diseases -> like the malaria parasite
- Single-celled protozoa that can replicate within cells, helminths parasitic worms and even insects or arachnids
7
Q
true or false: all microbes are harmful?
A
FALSE: - The microbiome is a collection of microbes that live symbiotically in and on a human (bacteria, viruses, fungi and parasites)
- This collection is found on the skin and on mucous membranes (membranes that line various cavities in the body and surfaces of internal organs)
- They are crucial to human health -> when in balance they perform various functions (help digest food, prevent inflammation, protect against infection from external pathogens and produce vitamins that are not synthesized by humans)
8
Q
Why do microbes that form the normal flora have the potential to become pathogenic?
A
This occurs when there is an imbalance between the ‘good’ and the ‘harmful’ microbes in the body -> these microbes are termed opportunistic or potential pathogens
9
Q
Innate immune system?
A
- An instant, non specific, first line of defense invading pathogens
- It responds immediately to prevent the spread and movement of pathogens in the body
- Includes different immune cells and barriers that activate in response to pathogens -> found throughout the body
- Physical barriers including the skin and mucous membranes prevent intruders from entering the body
- Chemical barriers like the enzymes in the saliva and tears also deter foreign invaders
Immune cells may cause inflammation in an infection in an infected region of the body, or even engulf viruses or bacteria to prevent infection at an early stage
10
Q
Adaptive immune system?
A
- Response takes several days to activate after the first contact with a pathogen
- Every response is specific to each invader
- The system constantly is searching for non self molecules -> antigens
- The response is strong -> pus, swelling, redness and pain
- After the infection is cleared -> the immune system commits the antigen to memory -> prepares the body to quickly fight off any future infections with the same microbe
11
Q
How does SARS-CoV-2 evade the immune system and cause an infection?
A
- Entry: enters through the oral or nasal passages into the lungs
- Invasion and colonization: it attaches itself to a human cell -> using its spike proteins to bind to ACE2, a receptor on the surface of the lung to get inside these cells
- Evasion of the immune response: it is able to delay the adaptive immune response
- Infection: to cause an infection, it must reproduce or replicate and spread to other organisms. It hijacks the machinery of the cell to replicate itself and spread to other cells
12
Q
True or false: Each pathogen has different tactics to evade the immune system
A
True
13
Q
Ways for an infection to be established in an organism?
A
- There must be an adequate reservoir (sites where the infectious pathogens can persist for long periods of time -> the can be biological (humans, chickens, bats, hamsters) or environmental (soil, swaps, lakes)) of the pathogen
- Mode of transmission for it to spread (ex: direct contact (organisms or surfaces), droplets (coughing or sneezing), air (spores), vectors (mosquitoes), vehicles (water or food))
Opportunistic conditions (conditions that encourage the development of the infectious disease -> promote microbes of the normal flora to become pathogenic and other to evade the immune system -> ex: stress, malnutrition, surgery, old age) for it to establish itself in a new host
- Mode of transmission for it to spread (ex: direct contact (organisms or surfaces), droplets (coughing or sneezing), air (spores), vectors (mosquitoes), vehicles (water or food))
14
Q
How can transmission be slowed or prevented?
A
- Eliminate reservoirs: ex, eliminating mosquitoes that spread malaria
- Enhanced barriers: face masks, hand washing, social distancing
Develop target medicines
- Enhanced barriers: face masks, hand washing, social distancing
15
Q
True or false: mosquito nets are used for fishing in some countries?
A
True: . Unfortunately, many of the people in need of these devices also struggle with food insecurity, and often use the netting for fishing, instead of their intended purpose. This alternative use has had a devastating effect on local tropical coastal ecosystems, while keeping malaria rates high
16
Q
Chickenpox:
A
- Highly contagious disease
- Caused by a virus
- Symptoms: blister-like rash that lasts about a week, fever, fatigue and headache
The prevalence of the disease got reduced by 199-folds after the vaccine was discovered
17
Q
Who can’t get vaccinated?
A
infants, the elderly, pregnant women, or immunocompromised individuals
18
Q
What is herd immunity?
A
which occurs when a significant proportion of the population is vaccinated and immune to the disease, can indirectly prevent those at risk from contracting the disease.
-> anti-vaxxer and vaccine refusal weakens the chances of acquiring herd immunity
19
Q
How did Indigenous people lose parts of their oral histories?
A
When Europeans began to colonize and settle in North America, a number of infectious diseases were also introduced into the native population. Without previous exposure to, and therefore no immunity against, diseases like smallpox, tuberculosis, and measles, Indigenous Peoples were decimated by waves of devastating epidemics
20
Q
Smallpox
A
- Infectious disease with a 30% mortality rate, caused by a virus
- Transmitted through saliva and open sores of the infected as well as surfaces exposed to the virus
Jeffrey Amherst: used blankets contaminated with smallpox as a weapon against indigenous people -> one of the first documented uses of biological warfare
- Transmitted through saliva and open sores of the infected as well as surfaces exposed to the virus
21
Q
Strep Throat
A
- Bacterial infection, easily treatable with a less than a week’s supply of antibiotics
- Many indigenous people die from a strep throat due to the healthcare system failing to meet their needs with inadequate resources
22
Q
Tuberculosis
A
- Infectious disease caused by bacteria
- Came with the European settlers -> TB epidemic
Despite a significant drop in T B cases now due to effective treatment with antibiotics, TB persists in Indigenous communities.
- Came with the European settlers -> TB epidemic
23
Q
What are the two characteristics of antibiotics?
A
How they target and what they target
24
Q
How do antibiotics target bacteria differently?
A
- Bacteriostatic drugs: inhibit bacterial growth, with the help of the host’s immune system. Therefore, bacteriostatic drugs would never be used for life threatening infections
- Bactericidal drugs kill susceptible bacteria, without any help from the host’s immune system.
25
What do different antibiotics target?
- Broad-spectrum antibiotics kills a wide range of bacteria
- Narrow-spectrum antibiotics is active against a small group of organisms (places less selective pressures on the bacteria that form part of our normal flora)
26
What if it is a serious infection? What antibiotic type should be used?
It takes time to determine the bacteria to be able to use the narrow-spectrum antibiotic, so if it is a serious infection, then we will start with the broad spectrum antibiotic
27
What do antibiotic act on?
These bacterial targets are structurally different, or nonexistent in eukaryotic cells, making antibiotics relatively nontoxic to humans.
28
Cell wall synthesis inhibitors:
prevent proper bacterial cell wall formation -> the cell dies from osmotic rupture. These may have specificity to Gram positive or Gram negative bacteria due to differences in their cell wall structures and enzymes (ex: penicillin: antibiotic that permanently binds to enzyme that crosslinks the peptidoglycans in the cell wall -> no crosslink
29
Metabolic pathways disruptors:
One common target in this class is folate synthesis. This process is not present in humans, who acquire folate through diet. A common tactic in metabolic pathway disruption is to use two antibiotics in conjunction, that block separate enzymes in the same pathway. (ex: Cotrimoxazole which is a combination of two antibiotics. Each individual antibiotic blocks separate stages of the bacterial folate synthesis pathway. On their own, they are bacteriostatic, however when they are used together, they are bactericidal. )
30
Protein synthesis inhibitors:
inhibits the translation of mRNA into its corresponding amino acid sequence, by targeting different sites on the ribosome. (eukaryotic ribosomes are different from prokaryotic ribosomes) (ex: doxycycline: is used for prevention of Lyme disease after a tick bite)
31
Cell membrane disruptors:
The human and bacterial plasma membranes are very similar. For this reason, very few antibiotics in this class are regularly used. Daptomycin is one such antibiotic. It creates leaks in the plasma membrane, halting important bacterial processes, such as protein synthesis and mitochondrial function. Drugs in this class have more severe side effects than other antibiotics. -> Despite its side effects, with the emergence of multi-drug resistant bacteria for which there are few remaining antibiotics, daptomycin is starting to be used more often. With limited dosing, most of the serious side effects can be mitigated.
32
Nucleic acid synthesis inhibitors:
DNA gyrase is the enzyme that supercoils the bacteria's single circular DNA -> these antibiotics make the bacteria unable to supercoil and store their DNA -> DNA degradation and cell death
33
Strategies of antibiotic resistance?
- Alter Targets: A mutation modifies the structure of a drug target, or another enzyme takes over the target’s function, such that the drug is no longer effective.
- Restrict Target Access: The drug is not able to enter the cell, or the antibiotic is pumped out immediately upon entering.
Develop Drug-Specific Enzymes: Bacteria develop an enzyme to destroy or modify the antibiotic so it no longer works
34
Steps of antibiotic resistant:
1- Infection: A host is infected with pathogenic bacteria, some of which are drug-resistant
2- Treatment: Antibiotics kill the pathogenic bacteria, except those that are drug-resistant.
3- Proliferation: The drug-resistant bacteria proliferate in the host, unaffected by the treatment.
4- Gene transfer: Bacteria may also transfer their drug-resistance to drug-susceptible bacteria. (passed on to progeny + horizontal gene transfer)
35
Types of horizontal gene transfer?
Horizontal gene transfer: where resistance genes are spread to other bacterial cells (most often of the same species). 3 Types of horizontal gene transfer:
- Transformation: extracellular DNA taken up by bacterium and incorporated into its genome
- Conjugation: direct cell-to-cell contact through plasmid gene transfer to a recipient cell
- Transduction: transfer of gene through the infection with a bacteriophage (bacterial virus)
36
Antibiotic resistance comes at a price to bacteria?
- There is a metabolic cost to maintain the resistance (making new proteins, altering protein structure…) requires energy expenditure
- Selective pressure: If the drug is no longer present -> the bacterium loses the resistance to waste less energy and resources -> grow more quickly (the antibiotic resistant strain will die off, once there the antibiotic stimulus disappears)
37
What are surveillance cultures?
Bacterial cultures (growing samples on a petri dish) done on patients who are admitted to hospital wards with high-risk populations, as an infection control preventative measure.
38
True or false: Hospital settings provide ideal opportunistic conditions for these antibiotic-resistant bacteria to spread, as patients are in close proximity and often have compromised immune system.
True
39
Types of antibiotic resistant bacteria in hospitals:
- MRSA: S. aureus is one of the most common causes of skin and soft tissue infections and can be treated with a variety of antibiotics. However, with methicillin-resistant S. aureus (M R S A) treatment options are much more limited
- CPO: Carbapenem-resistant organisms (C P O), although still relatively uncommon, are usually resistant to multiple classes of antibiotics and can be very difficult to treat. Some are even resistant to all classes of antibiotics.
40
What happens if a patient has an antibiotic resistant infection?
they are placed on contact precautions (Contact precautions: Infection prevention and control interventions intended to prevent transmission of infectious agents, such as using personal protective equipment, putting the patient in a one-bedroom, and restricting access to certain personnel, such as family, friends, and certain hospital staff)
41
What is the bacteria that quickly developed resistance through beta lactamase, an enzyme that destroys penicillin?
S. aureus
42
Methicillin
- Chemically modified version of penicillin resistant to the action of beta lactamase -> used to treat S. aureus infections
But some bacteria also developed resistance to it by altering the drug's target: penicillin-binding protein -> so that methicillin can no longer inhibit the cell wall synthesis
43
Vancomycin
Vancomycin is the default antibiotic used for treating MRSA:
- The widespread use of vancomycin led to two things:
- Vancomycin-resistant Enterococci (V R E): extremely common
- Vancomycin-resistant S. aureus (V R S A): very rare for now
Vancomycin-resistant strains leave few antibiotic choices remaining for treatment
44
Multidrug resistance
: bacteria that have acquired mechanisms of resistance for multiple antibiotic classes
45
What is the consequence of antibiotic resistance?
Antibiotic-resistant infections often result in multiple changes to antibiotic therapy, which increases costs, risks of adverse events, and length of treatment, as well as acts as a mechanism of selective pressure that helps to further drive this antibiotic resistance
46
What proves the selective pressure of resistance is caused by the use of million of antibiotics?
The prevalence of M R S A was less than 5% in most hospitals worldwide in the early 1970s, but a decade later had increased to as much as 40% in many hospitals in the United States and Europe.
47
2 most famous kinds of antibiotic resistance:
- Beta lactamases: is related to soooo many different bacterias
Carbapenem resistance: Carbapenems are broad-spectrum antibiotics used to treat multidrug resistant bacteria. Strains that are carbapenem-resistant have few, and in some cases, no antibiotics left to treat them
48
What is the sector that uses the most antibiotic?
Agriculture
49
Who is responsible for the overuse of antibiotic?
- Hospitals: Non-prescription antibiotic use and unregulated antibiotic sale is very common in low and middle income countries.
Agriculture and aquaculture: Animals are frequently treated with antibiotics to maintain growth and prevent disease in dense living conditions. Disease prevention in agriculture and aquaculture are major contributing factors for antibiotic overuse.
50
True or false: Resistant infections are likely going to increase more
- They are costly: they last for longer amounts of time and the treatment require more expensive drugs and create more adverse events for those who recover
51
How might we slow and prevent the development of antibiotic resistance?
* Continuous monitoring of antibiotic use and resistance.
* Continue researching and developing new antibiotics.
* Educate health care professionals on appropriate antibiotic use and prescription
52
Surveillance
Continuous monitoring of antibiotic use and resistance.
53
Stewardship:
Appropriate and careful use of microbiotics across all industries and sectors.
54
Research and Innovation
Continuous research and development in the field of antibiotic discovery.
55
Infection Prevention and Control:
Strict adherence to best practices in hygiene, sanitation, and infection control.
56
What did some countries do to reduce antibiotic resistance?
* The E U banned the use of antibiotics in food production in 2006.
* Medical schools and associations have limited antibiotic prescriptions through clear guidelines for prescribing and educating physicians in appropriate antibiotic use.
* Guidelines prohibit physicians from taking gifts from pharmaceutical companies, while also limiting drug advertisements to patients.
* Statistics are kept on the number of prescriptions made for different antibiotic classes. * Antibiotic-resistant organisms are screened for in hospitals and long-term care settings, while isolating those that test positive to prevent the spread to others.
57
True or false: Medical ethics are also much less stringent than in Canada, the United States, and the European Union. This is due to a multitude of factors, including a lack of accurate testing, funding, and political and healthcare sector leadership.
There are also a lack of regulations concerning both antibiotic use, and the quality of the antibiotics being sold, which may be lower quality and allow more resistance to occur.
True
58
True or false: Broad-spectrum antibiotics cause more antibiotic resistance than narrow-spectrum antibiotics
True
59
True or false: The pharmaceutical industry has not been encouraged to put a significant effort into discovering new antibiotics in recent decades, and when they have, many attempts have been unsuccessful. With the rise of antibiotic resistance, new classes will be necessary to fight these microbes, and they will need to be better managed
True
