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Questions and Answers

What defines mutualism in the context of symbiotic relationships?

  • One organism benefits while the other is completely harmed.
  • Both organisms are unaffected by the interaction.
  • One organism is harmed while the other benefits.
  • Both members benefit from the interaction. (correct)

    • Which characteristic is NOT true of resident flora?

  • They are easily removed by antibiotic treatment. (correct)
  • They establish residency after birth.
  • They can be found in mucous membranes.
  • They remain in the body throughout a person’s life.

    • What is the role of a pathogen in a parasitic relationship?

  • To provide nutrients to the host organism.
  • To assist in the growth of beneficial bacteria.
  • To create a mutual benefit for both organisms.
  • To cause disease and harm the host organism. (correct)

    • Which of the following describes amensalism?

    <p>One organism benefits while the other is harmed or suppressed.</p> Signup and view all the answers

    Which of the following statements is accurate regarding bacteria?

    <p>Bacteria lack nuclei and can take various shapes.</p> Signup and view all the answers

    What is the primary role of reservoirs in the continuation of an infection?

    <p>They provide a permanent environment for pathogens.</p> Signup and view all the answers

    Which of the following is an example of indirect contact transmission?

    <p>Sharing a drinking cup.</p> Signup and view all the answers

    In vector transmission, which type specifically serves as a host for part of the pathogen's life cycle?

    <p>Biological vectors.</p> Signup and view all the answers

    Which type of transmission involves pathogens being released via respiratory droplets?

    <p>Contact transmission.</p> Signup and view all the answers

    What is a common characteristic of zoonoses?

    <p>They occur primarily in animals but can infect humans.</p> Signup and view all the answers

    What is one requirement for a disease to be classified by incidence?

    <p>It tracks new cases over a specific period of time.</p> Signup and view all the answers

    Which of the following pathogens is most likely to be transmitted via foodborne transmission?

    <p>Cholera.</p> Signup and view all the answers

    What is a method of autoinoculation?

    <p>Infection by introducing a pathogen from one part of the body to another.</p> Signup and view all the answers

    Which type of transmission requires a medium for the transfer of pathogens?

    <p>Vehicle transmission.</p> Signup and view all the answers

    Which bodily fluids are particularly highlighted for care when handling in healthcare settings?

    <p>Bodily fluids such as blood, urine, and saliva.</p> Signup and view all the answers

    Which statement correctly describes prions?

    <p>They are infectious proteins that can misfold.</p> Signup and view all the answers

    What feature is common to all bacteria?

    <p>They are prokaryotic and single-celled.</p> Signup and view all the answers

    Which of the following infections occurs when multiple pathogens are present at the same location?

    <p>Mixed infection</p> Signup and view all the answers

    What role do mycorrhizae play in relation to plants?

    <p>They form symbiotic relationships with plant roots.</p> Signup and view all the answers

    Which of the following correctly differentiates endotoxins from exotoxins?

    <p>Endotoxins have a lipid composition; exotoxins are composed of proteins.</p> Signup and view all the answers

    Which infection pattern is characterized by symptoms that appear quickly and also resolve quickly?

    <p>Acute infection</p> Signup and view all the answers

    In the context of infectious disease terminology, what does 'septicemia' refer to?

    <p>Bacterial infection spreading through blood.</p> Signup and view all the answers

    What is the main function of a vaccine?

    <p>To stimulate the immune system against pathogens.</p> Signup and view all the answers

    What does the term 'fomite' refer to?

    <p>An inanimate object that can transmit pathogens.</p> Signup and view all the answers

    Which stage of infection is crucial for a microorganism to establish itself in the host?

    <p>Adhesion</p> Signup and view all the answers

    Which of the following terms refers to persistent, mild symptoms that do not cause apparent illness?

    <p>Subclinical infection</p> Signup and view all the answers

    What is a characteristic treatment approach for endemic diseases?

    <p>Monitoring and preventive measures within the community.</p> Signup and view all the answers

    How can pathogens evade host immune defenses?

    <p>By altering their antigens through mutation.</p> Signup and view all the answers

    What is the primary focus of epidemiology?

    <p>Studying the distribution and causes of disease in populations</p> Signup and view all the answers

    Which of the following best describes a prokaryotic cell?

    <p>Lacks a membrane-bound nucleus and organelles</p> Signup and view all the answers

    What is a characteristic of prions?

    <p>Are misfolded proteins that can cause disease</p> Signup and view all the answers

    Which of the following statements about opportunistic infections is true?

    <p>They can arise when normal flora is disrupted</p> Signup and view all the answers

    Which route is NOT a common portal of entry for pathogens?

    <p>Bone marrow</p> Signup and view all the answers

    How does the respiratory tract serve as a portal of entry for pathogens?

    <p>Through exposure to air droplets and aerosols</p> Signup and view all the answers

    What type of pathogen are viroids classified as?

    <p>Non-cellular plant pathogens</p> Signup and view all the answers

    What is the role of microbial ecology?

    <p>Studying interactions among various microbes</p> Signup and view all the answers

    Which of the following diseases is caused by a prion?

    <p>Mad cow disease</p> Signup and view all the answers

    Which of these is an example of an exogenous source of infection?

    <p>Pathogens contracted from contaminated food</p> Signup and view all the answers

    What is the significance of the flora in the human body?

    <p>They can protect against infections and maintain a balance</p> Signup and view all the answers

    Which of the following is NOT a treatment application of applied microbiology?

    <p>Chemical synthesis of drugs</p> Signup and view all the answers

    What methods can pathogenic microorganisms use to exit the host?

    <p>Leaving via respiratory droplets or bodily fluids</p> Signup and view all the answers

    What characterizes the normal flora in healthy individuals?

    <p>They help prevent infections by competing with pathogens</p> Signup and view all the answers

    Study Notes

    Symbiosis

    • Describes a close relationship between two different types of organisms in a community.
    • Mutualism: Both members benefit from the interaction.
      • E.g., E. coli in our gut releases vitamins we can't digest.
    • Commensalism: One organism benefits, and the other is neither harmed nor helped.
    • Parasitism: One organism benefits while the other is harmed slightly or may be killed.
      • Pathogen: A parasite that causes disease.
    • Amensalism: One organism can hamper or prevent the growth/survival of another without being affected by the other organism.

    Normal Flora

    • Newborns' first contact with microbes is through the birth canal.
    • Followed by breathing and feeding.
    • Throughout life, microbes establish residency in mucous membranes open to the environment.
    • Resident flora: Remain part of the normal flora throughout a person's life.
    • Transient flora:
      • Found in the same locations as resident microbes.
      • Only remain for a few hours, days, or months before they vanish.
      • E.g., Bacillus laterosporus intermittently present in intestines (helps suppress fungi such as Candida).

    Microbes

    • Microbe: Small organisms visible only under a microscope.
      • The study of microbes is "microbiology."
    • Bacteria:
      • Lack nuclei and membrane-bound organelles.
      • Different shapes: rods, spheres, spirals.
      • Found nearly everywhere on Earth.
    • Viruses:
      • Noncellular, submicroscopic particles.
      • Consist of nucleic acid surrounded by a protein coat.
    • Prions (proteinaceous infectious particles):
      • Not cellular, not viral, lack nucleic acids.
      • Proteins that misfold and become infectious agents.
      • When they become abnormally folded, they become infectious particles.
      • Diseases are called transmissible spongiform encephalopathies (e.g., mad cow disease, kuru).
    • Viroids:
      • Do not have a protein coat.
      • Are plant pathogens.
    • Fungi:
      • Study of fungi = Mycology.
      • Few fungi are pathogenic and virulent.
      • Immune system usually fights fungal invasion.
      • Have important symbiotic relationships with other organisms.
      • Play a major role in decomposition.
        • Mycorrhizae: Fungi on roots of plants.
      • Fungal colonies are vegetative.
      • Free-living and heterotrophic.
      • Appear as yeast, molds, fleshy fungi.
      • Have a cell wall composed of strong flexible polysaccharide called chitin.

    Contamination and Infection

    • Contamination: Presence of microbes in or on the body.
    • Infection: The presence and growth of a microorganism in the body (with the exception of organisms of normal flora).
      • The microorganism must gain entry into the host and its tissues.
      • An infection does not necessarily cause disease.

    Etiology of Infectious Disease

    • The study of the cause of disease when an infectious agent causes pathological changes and interferes with normal body functions.

    Patterns of Infection

    • Local infections: Organism enters the body and remains confined to a specific tissue.
    • Focal infections: Pathogen spreads from a local infection to other tissues.
    • Systemic infections: Infection spreads to several sites and tissue fluids, usually by the way of the circulatory system.
      • Septicemia, bacteremia, toxemia, viremia
    • Mixed infection: Several infectious agents concurrently establish themselves at the same site.
    • Acute infection: Appear rapidly, with severe symptoms, then vanish rapidly.
    • Chronic infection: Usually less severe symptoms, but they persist for long periods of time.
    • Primary infection: Initial infection.
    • Secondary infection: Follows primary infection, typically caused by a different microbe than what caused the primary infection.
    • Subclinical infection:
      • Does not cause any apparent symptoms.
      • Can be carried over long periods of time.

    Stages of Infection

    • Contamination: Presence of microbes in or on the body.
    • Infection: The presence and growth of a microorganism in the body (with the exception of organisms of normal flora).
      • The microorganism must gain entry into the host and its tissues.
      • An infection does not necessarily cause disease.
    • Adhesion:
      • The first and most crucial step of infection.
      • Without adhesion, the organism will be removed by ciliary motion, sneezing, coughing, swallowing, urine flow, tears, intestinal peristalsis.
      • Bacteria must bind to host cells by pili, fimbriae, or specific membrane receptor sites.
      • Adhesion can be specific or nonspecific.
        • Electrostatic attraction, atomic & molecular vibrations.
    • Colonization and Invasion:
      • Human pathogens usually colonize tissues that are in contact with the external environment.
        • Urogenital tract, Digestive tract, Respiratory tract, Conjunctiva.
      • Invasion: May be aided by the production of extracellular substances that disrupt host cell membranes.
        • Break down primary and secondary barriers of the host.
        • Are called invasins - facilitate the growth and spread of the pathogen.

    Evasion of Host Defense

    • Presence of capsules:
    • Production of proteins that bind to host cell antibodies:
    • Mutation of the organism to alter its antigenicity:
    • Microbial strategies to thwart host phagocytes:
      • Avoid contact with phagocytes.
      • Inhibition of phagocytic engulfment.
      • Survival inside the phagocytes.
      • Production of products that kill or damage phagocytes before or after ingestion.

    Toxins

    • Toxigenic: Organism that produces toxins.
      • Underlying mechanism by which microorganisms produce disease.
    • Endotoxins: Toxins within the bacterial cell wall.
    • Exotoxins: Toxins secreted by bacteria.
    • Typical toxin chemical make-up: Either lipopolysaccharides or proteins.

    Endemic, Epidemic, and Pandemic

    • Endemic: Repeatedly present in a given population or geographical area.
    • Epidemic: Occurs with greater frequency than usual in a population of a given area.
    • Pandemic: Is a worldwide epidemic.
    • Fomite: Any inanimate object or surface that can become contaminated with infectious microorganisms and act as a vehicle to transfer them to another person.

    Vaccine

    • Vaccine: The most effective method of preventing infectious diseases.
      • Provides immunity or protection against a specific infectious disease.
      • Works by stimulating the immune system to recognize and fight the pathogen.
    • Health Canada provides information on vaccine-preventable diseases:
    • CDC's Global Immunization Division (GID):
      • Public health mission to vaccinate against deadly diseases.
      • Prevent epidemics and pandemics.
      • Eradicated smallpox and polio.

    Epidemiology

    • The study of the distribution and cause of disease in populations.
    • Serves as the foundation and logic of interventions needed in the interest of public health and preventive medicine.
    • Focuses on: How many people are affected, where, the outcome of the disease (recovery, death, disability, and so on).
    • Major importance to public health departments.
    • Public Health Agency of Canada: https://www.canada.ca/en/public-health.html
    • CDC: The central source of epidemiological information in the United States.
    • Morbidity and Mortality Weekly Report:
      • Contains data on morbidity, incidence of specific notifiable diseases, mortality.

    Microorganism Classification

    • Prokaryotes:
      • No membrane-bound organelles, such as a nucleus (pro, before; karyon, nucleus).
      • Archaea, bacteria.
    • Eukaryotes:
      • With membrane-bound cell organelles.
      • Algae, fungi, protozoans.
    • Shared Properties:
      • Methods of reproduction: cell division, binary fission, mitosis, or meiosis.
      • Presence of DNA and RNA for protein synthesis.
      • Plasma membranes.
    • Viruses:
      • Noncellular, submicroscopic particles.
      • Consist of nucleic acid surrounded by a protein coat.
    • Prions (proteinaceous infectious particles):
      • Not cellular, not viral, lack nucleic acids.
      • Proteins that misfold and become infectious agents.
      • When they become abnormally folded, they become infectious particles.
      • Diseases are called transmissible spongiform encephalopathies (e.g., mad cow disease, kuru).
    • Viroids:
      • Do not have a protein coat.
      • Are plant pathogens.
    • Microbial ecology:
      • Often deals with biofilms.
      • Interactions:
        • Mutualism
        • Commensalism
        • Synergism
        • Parasitism
    • Normal flora versus pathogens:
    • Foodborne diseases: Organism/toxin contamination.
    • Waterborne diseases: Organism contamination.
    • Airborne diseases: Aerosols.

    Application of Microbiology

    • Applied Microbiology:
      • Food production: Yogurt, bread.
      • Alcoholic beverages: Wine, beer.
      • Treatment of water supplies: Indicator organisms.
      • Pharmaceutical agents: Penicillin.
      • Agriculture: Soil microbes, nitrogen cycle.
      • Bioremediation: Petroleum-digesting bacteria.
      • Energy: Fuel cells, ethanol, methane.
      • Forensics: Medicine, criminal justice, epidemiology, bioterrorism.

    Normal Flora

    • Normal flora: The microorganisms that normally live in or on the body.
      • Usually protective but can become opportunistic pathogens if the balance is disrupted.

    Opportunistic Infection

    • Opportunistic pathogens: Microbes of the normal flora that become pathogenic when the balance is disrupted.
      • Compromised immune system: AIDS, malnutrition, stress, age, chemo/radiation therapy.
      • Changes in the normal flora: Normal flora is usually protective, competition is reduced, and the organism enters areas of the body where it is not normally present.

    Aspects of Infection

    • Portal of entry: Sites where pathogens enter the body.
      • Exogenous: From outside the body.
      • Endogenous: Organism is already in the body (e.g., normal flora).
    • Virulence: The degree of pathogenicity.
      • Pathogenicity: The ability of a microbe to cause disease.
    • Portal of exit: Sites where pathogens leave the body to spread to others.

    Portals of Entry

    • Skin: Thick layer of keratinized dead cells. Pathogens can enter through natural openings or damaged skin (abrasions, cuts, punctures, scrapes).
    • Mucous membranes:
      • Gastrointestinal tract: Enteric bacteria (e.g., Salmonella, Shigella, Vibrio, E.coli), viruses (e.g., poliovirus, hepatitis A), protozoans (e.g., Entamoeba histolytica, Giardia lamblia), and helminths (e.g., trematodes, cestodes, nematodes).
      • Respiratory tract: Most frequently used portal of entry. Pathogens enter through air, dust particles, moisture, and droplets from infected people.
      • Urogenital tract: Transmitted by sexual contact. Girls and women who are not sexually active are susceptible to lower urinary tract infections.
      • Conjunctiva: Usually a good barrier against infectious agents. Some bacteria can easily attach to this membrane
    • Placenta: Usually an effective barrier against microorganisms. Some microbes can cross the placenta and infect the embryo or fetus.

    Epidemiology and Public Health

    • Prevalence: The total number of existing cases in the entire population.
    • Incidence: The number of new cases over a certain period of time compared with the general healthy population.
    • Reservoirs: Sites where pathogens are maintained and are a source of infection.
      • Nonliving reservoirs: Soil, water, food.
      • Animal reservoirs: Zoonoses (diseases that occur primarily in animals and can be transmitted to humans).
      • Human carriers: Infected but don't have symptoms.
    • Modes of transmission:
      • Contact transmission:
        • Direct: Person-to-person by touching, kissing, intercourse.
        • Indirect: Contact with a fomite (nonliving object).
        • Droplet Transmission: Respiratory droplets released by exhaling, laughing, coughing, or sneezing.
      • Vehicle transmission:
        • Airborne: Droplet nuclei (droplets of mucous), dust.
        • Bodily fluid: Especially important for healthcare workers.
        • Waterborne: Untreated or poorly treated water.
        • Foodborne: Incompletely cooked or poorly processed foods.
      • Vector transmission:
        • Biological vectors: Transmit pathogen and serve as a host (e.g., mosquitoes, ticks, lice, fleas).
        • Mechanical vectors: Passively carry agents to a new host (e.g., flies).

    Healthcare-Associated Infections (HAIs)

    • Infections acquired in healthcare facilities.
    • Types:
      • Contact transmission (e.g., Staphylococcus aureus, Clostridium difficile, MRSA).
      • Airborne transmission (e.g., Mycobacterium tuberculosis, Aspergillus fumigatus).
      • Droplet transmission (e.g., Streptococcus pneumoniae, Haemophilus influenzae).
      • Vehicle transmission (e.g., Acinetobacter baumannii, Pseudomonas aeruginosa).
    • Modes of transmission:
      • Often spread through direct contact or airborne droplets.
    • Implications:
      • Can be serious and even life-threatening, leading to increased hospital stays, costs, and mortality.
    • Control and prevention:
      • Hand hygiene, isolation procedures, environmental cleaning, proper use of personal protective equipment.
    • Example infections:
      • Urinary tract infections, pneumonia, surgical wound infections.

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