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Questions and Answers
How many bacteria are in the human body?
How many bacteria are in the human body?
90 trillion
What is the study of interactions between species and their environments called?
What is the study of interactions between species and their environments called?
Ecology
Which of the following is an example of commensalism?
Which of the following is an example of commensalism?
Which of the following is an example of mutualism?
Which of the following is an example of mutualism?
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The bacteria Pseudomonas aeruginosa can always cause disease.
The bacteria Pseudomonas aeruginosa can always cause disease.
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A quorum refers to a population of bacteria that is large enough to overcome the body's defenses.
A quorum refers to a population of bacteria that is large enough to overcome the body's defenses.
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Prions are self-replicating proteins.
Prions are self-replicating proteins.
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All bacteria are susceptible to antibiotics.
All bacteria are susceptible to antibiotics.
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Who discovered penicillin?
Who discovered penicillin?
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What is the name of the bacteria that causes mad cow disease?
What is the name of the bacteria that causes mad cow disease?
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What is the ability of a pathogen to cause damage or death called?
What is the ability of a pathogen to cause damage or death called?
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The virulence of a pathogen can change over time.
The virulence of a pathogen can change over time.
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What is the name of the disease used as an example of a pathogen's changing virulence?
What is the name of the disease used as an example of a pathogen's changing virulence?
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Natural selection favors pathogens that are highly virulent.
Natural selection favors pathogens that are highly virulent.
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What are the two factors that pathogens must balance to be successful?
What are the two factors that pathogens must balance to be successful?
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Which of the following are ways pathogens can emerge?
Which of the following are ways pathogens can emerge?
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What is the order of the steps in the emergence of a pathogen?
What is the order of the steps in the emergence of a pathogen?
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What is the main purpose of vaccinations?
What is the main purpose of vaccinations?
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What is the type of immunity that occurs after recovering from an infectious disease called?
What is the type of immunity that occurs after recovering from an infectious disease called?
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Which of the following is an example of passive immunity?
Which of the following is an example of passive immunity?
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What are the three key factors in controlling disease?
What are the three key factors in controlling disease?
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A weakened population is more vulnerable to disease outbreaks.
A weakened population is more vulnerable to disease outbreaks.
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Good hygiene practices can help to prevent disease spread, even during outbreaks.
Good hygiene practices can help to prevent disease spread, even during outbreaks.
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Access to clean water and proper sanitation is essential for preventing disease outbreaks.
Access to clean water and proper sanitation is essential for preventing disease outbreaks.
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Study Notes
Biological Determinants of Infectious Disease & Immunity
- This course covers the biological factors related to infectious diseases and immunity.
Outline of Topics
-
Part A: Focus on Microbes
- Microbes and Microbiome (10.1)
- Antibiotic Resistance (10.2 & 14.5)
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Part B: Microbes & Humans
- Virulence & Illness (10.3)
- Pathogens (10.4)
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Part C: Control
- Controlling Disease (10.5, 14.4 & 14.6)
Microbiome
- Your body is comprised of approximately 100 trillion cells, with only 10 trillion being your own cells. The remaining 90 trillion are bacteria and other single-celled organisms.
- A study found 182 different species of bacteria on a single forearm.
- Ecology is the study of interactions among species in their environments.
Microbiome - Types of Interactions
- Commensalism: One species benefits, while the other is neither helped nor harmed. (e.g., mites in eyebrows)
- Mutualism: Both species benefit. (e.g., bacteria in the digestive tract; some bacteria protect against pathogens and produce vitamins, while others help with digestion)
Microbiome - Changes in Interactions
- Interactions between microbes and the host can change if conditions alter.
- For instance, Pseudomonas aeruginosa can be harmless on healthy individuals but can cause necrosis (tissue death) when a population density (quorum) is reached.
- Some species always cause disease.
Infectious Disease Agents - Bacteria
- We are surrounded by various types of microorganisms
- Some microbes are prokaryotic (lacking membrane-bound organelles).
- Prokaryotic organisms can be beneficial (e.g., digestion) or harmful (e.g., cholera, tuberculosis).
Infectious Disease Agents - Parasites
- Some microorganisms are protozoans (single-celled eukaryotic organisms).
- Examples include giardiasis, amoebic dysentery, and malaria.
- Multicellular organisms like fungi can also cause disease, such as yeast infections and athlete's foot.
Infectious Disease Agents - Viruses
- Viruses and prions are pathogens but not alive.
- Viruses need a host cell to replicate.
- Examples include HIV (responsible for AIDS) with protein shells and genetic material inside.
Infectious Disease Agents - Prions
- Prions are self-replicating proteins.
- Some prions found in the brain can transform into pathogens that cause diseases like mad cow disease (Creutzfeldt-Jakob disease).
- Infectious prions cause normal prion proteins to fold in a harmful way.
Antibiotics Resistance
- Penicillin was discovered in 1928 and widespread use began in 1943.
- Bacteria are increasingly resistant to antibiotics.
- Resistance populations form when a few bacteria survive antibiotic exposure and then reproduce.
- Mechanisms that lead to antibiotic resistance include
- Blockage of the antibiotic
- Degradation of the antibiotic
- Alteration of the antibiotic
- Removal of the antibiotic
- Horizontal gene transfer mechanisms also contribute to the spread of resistance:
- Transformation
- Transduction
- Conjugation
Antibiotics Resistance - Ecological Considerations
- Many antibiotics are found naturally in bacteria, molds, and other species.
Antibiotics Resistance - Mechanisms of Disease
- Resistant organisms can either have resistance genes or acquired mutations
Antibiotics Resistance - Other Considerations
- Even though bacterial resistance can be advantageous, it comes at a cost because cells need energy to maintain resistance. This energy is diverted from other functions, like growth and reproduction (e.g., why not all bacteria are resistant).
Virulence & Illness
- Pathogens vary in their virulence (ability to cause damage or death).
- Some pathogens can change their virulence after initial infection.
- Example: Myxoma virus initially killed 99% of infected rabbits but now only kills ~50% of infected rabbits.
Virulence & Illness - Evolution of Disease
- Natural selection favors pathogens that reproduce successfully, but also need to balance this with ease of transmission to new hosts.
- Pathogens that reproduce easily without the ability to spread will not be as successful.
Pathogens - Emerging
- Species can evolve into new strains that cause disease.
- Humans can contract diseases from other species.
- Microbes living in soil or water can cause disease in humans.
Pathogens - Emergence - Stages
- Exposure
- Infection
- Transmission
- Epidemic
Resistance - Pathogens - Control - Chain of Infection
- Susceptible hosts: Can include individuals of different ages, individuals with illnesses, or individuals with limited resistance.
- Transmission: Direct contact, bites/stings, droplets, air.
- Reservoir: Humans, animals, surfaces.
- Points of exit & entry: Eyes, mucous membranes, respiratory tracts (includes air and droplet mechanisms), urinary tract, blood.
- Controlling diseases: Vaccines, hygiene, and clean water systems are all important in disease control.
Controlling Disease - Vaccines
- Vaccinations have effectively controlled some diseases (mumps, measles, polio and chicken pox).
- Pathogens that mutate rapidly are hard to control with vaccines; the immune response cannot keep up.
Controlling Disease - Natural Immunity
- Immunity that results from recovering from an earlier infection.
Controlling Disease - Passive Immunity
- Transferring antibodies from one individual to another (example: antibodies from mother to baby after childbirth; or breast feeding).
Controlling Disease - Additional Considerations
- Wellness: A weakened population is more susceptible to disease outbreaks.
- Hygiene: Practicing good personal hygiene is critical for disease prevention.
- Clean water and sewers: Human waste must be properly disposed of to prevent contamination of water sources and disease outbreaks in the population. An example of a disease that can be prevented by hygienic practices and clean water is cholera.
Scientist Spotlight: Anthony Fauci
- Fauci led the fight against HIV/AIDS.
- Actively sought to involve activists in disease research and new models for testing treatments.
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Description
This quiz explores the biological determinants of infectious diseases and immunity, focusing on microbes and their interactions with humans. Topics include microbiomes, antibiotic resistance, virulence, pathogens, and disease control strategies. Test your knowledge and understanding of these vital concepts!
