Pathogens and Infectious Diseases Quiz

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Questions and Answers

What does a website ending in .gov or .mil indicate?

  • The website is personal.
  • The website is official and secure. (correct)
  • The website is commercial.
  • The website is a nonprofit organization.

What factor makes humans a desirable host for microorganisms?

  • Humans are generally isolated from other organisms.
  • The human body provides a nutrient-rich and warm environment. (correct)
  • Humans have minimal interaction with microbes.
  • Humans possess a unique immune system.

How does the normal flora typically behave in relation to pathogens?

  • Normal flora are identical to pathogens.
  • Normal flora are always pathogenic.
  • Normal flora only cause trouble when the immune system is compromised. (correct)
  • Normal flora always causes disease.

What characteristic distinguishes dedicated pathogens from the normal flora?

<p>Pathogens do not depend on the host's health status to cause disease. (B)</p> Signup and view all the answers

What is an example of when normal flora can cause harm?

<p>When they enter a sterile part of the body. (D)</p> Signup and view all the answers

How many bacterial, fungal, and protozoan cells are approximately present in the human body compared to human cells?

<p>Around 10 times more than human cells. (B)</p> Signup and view all the answers

What is the primary feature of microorganisms that can cause disease in humans?

<p>They have evolved mechanisms to survive and reproduce in the host. (D)</p> Signup and view all the answers

Why do we typically view pathogens as hostile invaders?

<p>Because they can cause illness or death. (C)</p> Signup and view all the answers

What is required for the replication and expression of genetic information in DNA and RNA?

<p>Structure of nucleic acids (A)</p> Signup and view all the answers

What distinguishes prions from typical infectious agents?

<p>Aberrant protein structure replication (D)</p> Signup and view all the answers

Which of the following diseases is most well-known to be caused by prions?

<p>Bovine spongiform encephalopathy (C)</p> Signup and view all the answers

What is the primary infectious property of prion proteins?

<p>Causing normal proteins to misfold (B)</p> Signup and view all the answers

Why are proteins usually able to find their correct folded conformation?

<p>The mechanisms are not fully understood (B)</p> Signup and view all the answers

What factor primarily determines whether a misfolded protein will behave like a prion?

<p>Folding structure constraints (A)</p> Signup and view all the answers

Which of the following entities can cause infectious diseases?

<p>All classes of pathogens (C)</p> Signup and view all the answers

How do most pathogenic bacteria promote their replication and spread in the host?

<p>Through virulence genes (A)</p> Signup and view all the answers

What is a common characteristic of pathogens like protozoa and fungi during infection?

<p>They switch between multiple forms (C)</p> Signup and view all the answers

What limitation do viruses face in replicating their proteins?

<p>Dependence on host machinery (C)</p> Signup and view all the answers

What are virulence genes primarily responsible for in pathogenic bacteria?

<p>Enabling the organism to cause disease (D)</p> Signup and view all the answers

What role do mobile bacteriophages play in pathogenicity?

<p>They carry virulence genes to other bacteria (A)</p> Signup and view all the answers

Which component of cholera toxin is responsible for transferring the A subunit into host cells?

<p>The B subunit (C)</p> Signup and view all the answers

What distinguishes Bacillus anthracis, the causative agent of anthrax, from other pathogens?

<p>It propagates using dormant spores (A)</p> Signup and view all the answers

What is the function of the A subunit of edema toxin in anthrax infections?

<p>Converting ATP into cyclic AMP (C)</p> Signup and view all the answers

What is the primary challenge in treating fungal and protozoan infections compared to bacterial infections?

<p>They have life cycles with multiple forms (A)</p> Signup and view all the answers

Virulence factors are best described as what type of proteins?

<p>Toxic proteins that interact with host cells (B)</p> Signup and view all the answers

What mechanism is commonly used by bacteria to inject toxic proteins into host cells?

<p>Type III secretion system (B)</p> Signup and view all the answers

How do most antibiotics preferentially treat bacterial infections?

<p>By targeting bacteria-specific processes (B)</p> Signup and view all the answers

What common feature do toxins produced by both cholera and anthrax share?

<p>They can cause ion imbalances in host cells (A)</p> Signup and view all the answers

Which of the following is a major difference between prokaryotic and eukaryotic cells relevant to antibiotic treatment?

<p>Prokaryotic cells possess unique pathways absent in eukaryotes (C)</p> Signup and view all the answers

Which toxin component of anthrax directly binds to host cell receptors to facilitate entry?

<p>B subunit of both toxins (C)</p> Signup and view all the answers

What can trigger the transfer of virulence genes to an avirulent bacterium?

<p>Infection by mobile bacteriophages (D)</p> Signup and view all the answers

Why are antifungal and antiparasitic drugs often more toxic than antibiotics?

<p>They target eukaryotic organisms similar to humans (A)</p> Signup and view all the answers

Which of the following mechanisms is NOT necessary for a successful pathogen to survive and multiply in a host?

<p>Produce large amounts of energy independently (B)</p> Signup and view all the answers

What is one potential reason microorganisms evolve to cause disease?

<p>To enhance their efficiency of spread (C)</p> Signup and view all the answers

Which of the following best describes obligate pathogens?

<p>Pathogens that can replicate only inside human cells (C)</p> Signup and view all the answers

What is a hallmark of bacterial infection as a result of the host's immune response?

<p>Increased production of pus (B)</p> Signup and view all the answers

Which of the following pathogens is considered an opportunistic pathogen?

<p>Pseudomonas aeruginosa (A)</p> Signup and view all the answers

What distinguishes facultative pathogens from obligate pathogens?

<p>Facultative pathogens can replicate outside a host. (C)</p> Signup and view all the answers

Which infectious agent is characterized by being made only of protein and lacks a genome?

<p>Prion (A)</p> Signup and view all the answers

How do fever and inflammation serve as defenses against infection?

<p>By inhibiting pathogen growth (B)</p> Signup and view all the answers

Which of the following terms refers to bacteria that have the potential to cause disease only in specific circumstances?

<p>Opportunistic pathogens (D)</p> Signup and view all the answers

What is characteristic of the pathogen Shigella flexneri?

<p>It only infects humans and primates. (B)</p> Signup and view all the answers

Which aspect of pathogens contributes significantly to their ability to cause disease?

<p>Their ability to induce immune responses (A)</p> Signup and view all the answers

What is the primary method by which viruses replicate within their host cells?

<p>Using host's transcription and translation machinery (D)</p> Signup and view all the answers

Which of the following varieties of pathogens would most likely have variable mechanisms of causing disease?

<p>Bacteria (B)</p> Signup and view all the answers

What defines a fastidious pathogen?

<p>Pathogens that only thrive in specific conditions. (C)</p> Signup and view all the answers

Why is understanding both pathogen and host biology important in studying infectious diseases?

<p>Hosts and pathogens interact and influence disease progression. (D)</p> Signup and view all the answers

What is dimorphism in pathogenic fungi?

<p>The ability to exist in either yeast or mold form (C)</p> Signup and view all the answers

Which organism is known for transitioning from a mold to a yeast form upon inhalation?

<p>Histoplasma capsulatum (C)</p> Signup and view all the answers

What is the main way through which malaria parasites are transmitted to humans?

<p>Bite of female Anopheles mosquitoes (C)</p> Signup and view all the answers

How are gametes formed in Plasmodium falciparum infected individuals?

<p>In the bloodstream of infected humans (C)</p> Signup and view all the answers

What is a consequence of the sickle cell mutation in relation to malaria?

<p>Resistance to malaria among carriers (B)</p> Signup and view all the answers

What distinguishes viruses from bacteria and fungi?

<p>Viruses lack a cellular structure (D)</p> Signup and view all the answers

What is the function of viral capsid proteins?

<p>To protect viral genetic material (D)</p> Signup and view all the answers

What is the process by which enveloped viruses exit host cells?

<p>By budding from the host cell (C)</p> Signup and view all the answers

What is a critical challenge in developing antiviral drugs?

<p>Viruses utilize host cell machinery for replication (C)</p> Signup and view all the answers

Which of the following diseases has been effectively eradicated through vaccination?

<p>Smallpox (D)</p> Signup and view all the answers

How many distinct forms does Plasmodium falciparum have?

<p>Eight (B)</p> Signup and view all the answers

Which of the following statements about viral genomes is true?

<p>They can consist of either DNA or RNA. (D)</p> Signup and view all the answers

What feature is common to both eukaryotic parasites and fungi?

<p>They possess a cellular structure. (A)</p> Signup and view all the answers

What is the possible outcome of viruses causing chronic infections?

<p>They can lead to cancer development. (D)</p> Signup and view all the answers

Flashcards

How to identify an official government website

Websites belonging to the US federal government often end with '.gov' or '.mil'.

What does 'https://' signify?

The 'https://' prefix in a website address indicates a secure connection, ensuring the safety of your data while browsing.

Why do pathogens exist?

A pathogen, like any other organism, strives to survive and reproduce. Their existence relies on exploiting a host organism for survival.

Why is a human body suitable for microorganisms?

A human body offers a hospitable environment for microorganisms due to its abundance of nutrients, warmth, moisture, and stable temperature.

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What is normal flora?

Microorganisms that reside in specific areas of the body, like the skin and gut, are known as the normal flora.

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What is the relationship with viruses in the human body?

Viruses are constantly present in our system, but most rarely cause noticeable symptoms.

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How do pathogens differ from normal flora?

Pathogens are usually distinct from the normal flora, causing harm even without a weakened immune system or compromised environment.

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How can normal flora become pathogenic?

A weakened immune system, injury, or access to sterile body parts allows normal flora to become problematic and cause illness.

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Virulence Genes

Genes that contribute to the ability of an organism to cause disease.

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Virulence Factors

Proteins encoded by virulence genes that contribute to the ability of an organism to cause disease.

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Pathogenicity Islands

Clusters of virulence genes found on the bacterial chromosome.

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Virulence Plasmids

Extrachromosomal DNA molecules that carry virulence genes.

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Mobile Bacteriophages

A type of bacteriophage that can carry virulence genes.

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Pathogenicity

The ability of a pathogen to cause disease.

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Pathogen Evolution

The acquisition of virulence genes by a previously avirulent bacterium.

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Cholera Toxin

The toxin produced by Vibrio cholerae that causes diarrhea.

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B Subunit

The subunit of cholera toxin that binds to the host cell membrane.

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A Subunit

The subunit of cholera toxin that enters the host cell and disrupts cellular function.

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Adenylyl Cyclase

The enzyme that catalyzes the transfer of an ADP-ribose moiety from NAD to the G protein Gs.

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Anthrax Toxin

The toxin produced by Bacillus anthracis.

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Edema Toxin B Subunit

The subunit of anthrax toxin that binds to the host cell membrane.

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Edema Toxin A Subunit

The subunit of anthrax toxin that directly converts ATP into cAMP.

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Type III Secretion System

A specialized protein secretion system used by bacteria to deliver toxins into host cells.

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Pathogen adaptations

Pathogens have evolved special mechanisms to cross cellular and biochemical barriers, evade the host's immune system, and multiply within the host.

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Five steps of successful pathogen infection

A pathogen must successfully colonize the host, find nutrients, evade the host's immune system, replicate, and spread to new hosts.

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Pathogenesis

The ability of a pathogen to cause disease.

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Opportunistic pathogen

A pathogen that causes disease only when the host is injured or immunocompromised.

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Obligate pathogen

A type of pathogen that can only replicate inside the cells of a host.

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Facultative pathogen

A type of pathogen that can replicate in an environmental reservoir but also cause disease in a host.

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Fastidious pathogen

A pathogen that only infects a specific species or group of species.

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Generalist pathogen

A pathogen that can infect a wide range of species.

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What are viruses?

A virus is a small, infectious agent that can only replicate inside the cells of a host. It consists of genetic material (DNA or RNA) wrapped in a protein coat and sometimes a membrane.

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What are bacteria?

Bacteria are single-celled, usually free-living organisms that can often perform most of their basic metabolic functions independently, relying on the host mainly for nutrition.

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What are eucaryotic pathogens?

Eucaryotic organisms can be single-celled (like fungi and protozoa) or multicellular (like parasitic worms) and can cause disease.

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What are prions?

Prions are unusual infectious particles made only of protein. They lack genetic material but can replicate and cause disease.

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Host immune response and disease symptoms

Many of the symptoms we associate with infectious diseases are the result of the host's immune system trying to fight off the pathogen.

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Host-pathogen interactions

Understanding infectious diseases requires understanding both the pathogen and the host's response.

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Exploiting host cell biology

Pathogens often exploit features of host cell biology for their own survival and multiplication.

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Dimorphism

The ability of a fungus to grow in either yeast or mold form.

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Histoplasmosis

A type of infection caused by the Histoplasma capsulatum fungus, which grows as a mold in soil but switches to a yeast form in the lungs.

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Protozoan life cycle

The process by which parasites, such as Plasmodium, cycle through different stages of development within different host organisms.

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Malaria

A common protozoal disease caused by Plasmodium parasites transmitted through mosquito bites.

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Plasmodium falciparum

The most studied species of Plasmodium that causes malaria, existing in multiple forms and requiring both human and mosquito hosts for its life cycle.

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Sickle Cell Anemia

A genetic disorder caused by a mutation in the hemoglobin β chain, making red blood cells sickle-shaped. It offers resistance to malaria.

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Adaptation

A trait that helps an organism survive and reproduce in a particular environment, often arising due to mutations.

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Bacteria, Fungi, and Eukaryotic parasites

Microscopic organisms that are composed of cells and possess their own machinery for essential processes like DNA replication, transcription, and translation.

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Viruses

Simple infectious agents that consist of nucleic acid encased in a protein coat, relying on host cells for replication.

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Viral Genome

The genetic material of a virus, composed of either DNA or RNA, which can be single-stranded or double-stranded.

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Viral capsid

The protein coat surrounding the viral genome, sometimes further enclosed by a lipid envelope.

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Viral replication

The process by which viruses replicate within host cells, involving disassembly, genome replication, protein synthesis, and assembly.

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Viral lysis

The release of progeny viruses from a host cell, often leading to cell death.

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Viral budding

The ability of some viruses to leave a host cell without lysing it, allowing for chronic infections and potential cancer development.

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Viral proteins

Proteins encoded by viral genomes, often categorized by their role in replicating the genome, packaging it, and modifying host cell functions.

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How do prion diseases occur?

Prion diseases are caused by prions, which are misfolded proteins that can cause other proteins to misfold. These misfolded proteins can aggregate and cause cellular damage, leading to neurodegenerative diseases.

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What is Bovine Spongiform Encephalopathy (BSE)?

One of the most well-known prion diseases is bovine spongiform encephalopathy (BSE), also known as mad cow disease. This disease can spread to humans who consume infected beef.

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How do prions replicate?

The infectious prion protein is made by the host, and its amino acid sequence is identical to a normal host protein. The difference lies in its folded three-dimensional structure. The misfolded prion protein can cause the normal protein to adopt its misfolded prion conformation, becoming infectious.

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What are pathogens?

Pathogens are defined as disease-causing microorganisms or agents. They include bacteria, fungi, protozoa, worms, viruses, and even prions.

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How do pathogenic bacteria differ from non-pathogenic bacteria?

Unlike viruses, bacteria have their own metabolism and can produce proteins independently. However, some pathogenic bacteria contain virulence genes that help them interact with and exploit the host.

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Do all pathogens have the same life cycle?

Parasitic fungi, protozoa, and other eukaryotic parasites often have complex life cycles involving different forms. They can switch between these forms to survive in a host and cause disease.

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How do viruses replicate?

Viruses rely on host cells for replication. They can't make their own proteins or replicate their genome independently. They hijack the host's machinery to produce their proteins and replicate themselves.

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What makes prions unique?

Prions are the smallest and simplest infectious agents. They are misfolded proteins that can cause other proteins to misfold and become infectious. They contain no nucleic acid.

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Study Notes

Pathogens and Infectious Diseases

  • Pathogens, like parasites, are simply trying to survive and reproduce, often at the expense of a host organism.
  • Humans are a desirable host environment due to warmth, moisture, and nutrient availability.
  • Microorganisms have evolved to thrive within the human body.

Normal Flora vs. Pathogens

  • The human body is a complex ecosystem with 1013 human cells and 1014 microbial cells (bacteria, fungi, protozoa).
  • Normal flora are microbes typically residing in specific areas (skin, mouth, intestines, vagina). Majority are harmless.
  • Pathogens differ; they can cause illness or death even in a healthy host. They possess adaptations for overcoming host defenses.
  • Normal flora only cause trouble if the immune system is compromised or they enter sterile areas of the body.

Key Characteristics of Successful Pathogens

  • Colonization: Establishing a foothold in the host.
  • Finding a compatible niche for growth and nutrition.
  • Evasion of the host's immune system (innate and adaptive).
  • Replication utilizing host resources.
  • Spread to a new host.

Pathogen Diversity and Disease

  • Pathogens exhibit diversity in structure, size, and genetic content (DNA vs. RNA, enveloped vs. non-enveloped).
  • Each pathogen causes disease through specific mechanisms.
  • Pathogenic responses can sometimes enhance pathogen spread (e.g., herpes lesions aiding sexual transmission or diarrhea aiding caretaker infection.)
  • Sometimes disease induction by a pathogen has no apparent advantage—symptoms are host immune system responses.

Major Types of Pathogens

  • Viruses: Nucleic acid (DNA or RNA) wrapped in protein, utilizing host cells for replication. Range from common cold to severe illnesses like AIDS and smallpox.
  • Bacteria: Larger, more complex, mostly free-living cells that rely on the host for nutrition, but can have specific adaptations to cause disease.
    • Obligate pathogens: require host cells to replicate.
    • Facultative pathogens: use external reservoirs like water or soil, only causing disease upon contact with a host.
    • Opportunistic pathogens: normally harmless, but can become pathogenic in compromised hosts.
  • Eukaryotic Parasites (Fungi, Protozoa, Worms):
    • Fungal pathogens: can switch between yeast and mold forms during infection; example: Histoplasma capsulatum.
    • Protozoan parasites: have complex life cycles, frequently requiring more than one host; example: Malaria (Plasmodium).
  • Prions: Infectious proteins that cause neurodegenerative diseases like mad cow disease (BSE). They misfold normal proteins, initiating a chain reaction.

Virulence Genes and Factors

  • Virulence genes, clustered in pathogenicity islands or plasmids, encode virulence factors (toxic proteins) that interact with host cells.
  • Example: Cholera toxin from Vibrio cholerae: disrupts ion balance in gut cells causing diarrhea
  • Example: Anthrax toxins from Bacillus anthracis: disrupt cellular signaling pathways.

Mechanisms of Pathogen Transmission

  • Pathogens use diverse mechanisms for spreading—some pathogens spread from one infected host to another (direct or indirect); others rely on environmental reservoirs and host contact.
  • Some pathogens are transmitted through vectors.

Preventing and Treating Infectious Diseases

  • Antibiotics target bacterial macromolecular synthesis, avoiding damage to human cells.
  • Antifungals and antiparasitics are often less effective and more toxic than antibiotics, due to similarities between pathogens and human cells.
  • Vaccination is a highly effective prophylactic measure to prevent viral infections, as exemplified historically by smallpox eradication.

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