Unit 7 Objectives NOT DONE

Question 1

What is the microbiota?

Answer 1

The microbiota is the community of microorganisms, including bacteria, fungi, and viruses, that naturally inhabit various sites of the human body

Question 2

What role(s) does/do the microbiota play in the health of an individual?

Answer 2

The microbiota aids in digestion, produces essential nutrients, supports immune function, and protects against pathogenic microbes

Question 3

What is the difference between resident vs. transient microbiota?

Answer 3

Resident microbiota permanently inhabit certain body sites

While transient microbiota are temporary residents that may not establish a lasting presence

Question 4

How does one acquire his/her microbiota?

Answer 4

One acquires microbiota from the environment, birth canal, breastfeeding, and close contact with caregivers and surroundings

Question 5

How can the normal microbiota become opportunistic pathogens?

Answer 5

When the immune system is compromised or if they gain access to parts of the body where they are not normally found

Ex. E. coli ­(esh-ĕ-rik’ē-ă kō’lī) is mutualistic in the colon, but should it enter the urethra, it becomes an opportunist that produces a urinary tract infection and disease.

Changes in the relative abundance of normal microbiota

Stressful conditions. Anything that strains a person’s normal metabolism or emotional state. (hormonal changes, unresolved emotional stress, abrupt changes in diet, exposure to overwhelming numbers of pathogens)

Question 6

Why is adhesion important in infection?

Answer 6

Adhesion is essential in infection because it allows pathogens to attach to host cells, establishing a site for colonization and overcoming initial immune defenses, which is a critical step in beginning an infection

Question 7

How are the following important in infection?

a. Adhesion disk

Answer 7

Found in some protozoa, adhesion disks enable attachment to host cells, securing the pathogen firmly to the host and allowing it to remain in place long enough to initiate infection.

Question 8

How are the following important in infection?

b. Ligands

Answer 8

Ligands are specific molecules, such as lipoproteins or glycoproteins, on pathogens that bind to complementary receptors on host cells, allowing for precise attachment and host specificity.

Question 9

How are the following important in infection?

c. Hooks & suckers

Answer 9

Found in helminths, these structures help anchor the parasite to host tissues, ensuring that the parasite can resist removal from the host’s body and establish infection.

Question 10

How are the following important in infection?

d. Attachment proteins

Answer 10

Present on viruses, attachment proteins bind to host cell receptors, allowing the virus to enter or inject genetic material into the host cell.

Question 11

How are the following important in infection?

e. Adhesins & capsules

Answer 11

Adhesins on bacterial structures like fimbriae, flagella, and glycocalyces facilitate attachment to host cells,

while capsules help evade immune detection and contribute to stable attachment.

Question 12

How are the following important in infection?

f. Glycoprotein receptors

Answer 12

Host cells have glycoprotein receptors, which serve as binding sites for microbial ligands, playing a key role in pathogen recognition and specificity in infection.

Question 13

Biofilms and Infection:

Answer 13

Biofilms, like dental plaque, consist of communities of bacteria and polysaccharides that adhere to surfaces within a host, providing a protective environment for pathogens and enhancing their resistance to immune defenses and antimicrobial treatments.

Question 14

What are virulence factors?

Answer 14

Virulence factors are molecules or structures produced by pathogens that enable them to infect, survive, and cause disease in a host by evading immune responses or damaging host tissues

Question 15

How do each of the following virulence factors help a pathogen cause disease?

a. Adhesion factor

Answer 15

Adhesion factors, such as ligands and adhesins, allow pathogens to attach to host cells, which is essential for colonization and establishment of infection.

Question 16

How do each of the following virulence factors help a pathogen cause disease?

b. Biofilm

Answer 16

Biofilms are communities of microorganisms encased in a protective layer, making them resistant to antibiotics and immune responses, aiding in persistent infections.

Question 17

How do each of the following virulence factors help a pathogen cause disease?

c. Hyaluronidase

Answer 17

This enzyme breaks down hyaluronic acid, which holds cells together, allowing pathogens to invade deeper tissues.

Question 18

How do each of the following virulence factors help a pathogen cause disease?

d. Collagenase

Answer 18

Collagenase degrades collagen, the main structural protein in tissues, enabling pathogens to spread through host tissue barriers.

Question 19

How do each of the following virulence factors help a pathogen cause disease?

e. Coagulase

Answer 19

Coagulase induces blood clotting around pathogens, creating a protective barrier that helps bacteria evade immune cells.

Question 20

How do each of the following virulence factors help a pathogen cause disease?

f. Hemolysins

Answer 20

Hemolysins destroy red blood cells and release nutrients like iron, which bacteria use for growth and survival.

Question 21

How do each of the following virulence factors help a pathogen cause disease?

g. Staphylo- & strepto-kinases

Answer 21

These kinases dissolve blood clots, helping pathogens to spread from clotted areas into surrounding tissues.

Question 22

How do each of the following virulence factors help a pathogen cause disease?

h. Type III secretion systems

Answer 22

These structures inject toxins or other molecules directly into host cells, manipulating cell function and aiding pathogen survival.

Question 23

How do each of the following virulence factors help a pathogen cause disease?

i. Exotoxins

Answer 23

Exotoxins are secreted proteins that damage host cells and tissues directly, often causing specific symptoms like neurotoxic or cytotoxic effects.

Question 24

How do each of the following virulence factors help a pathogen cause disease?

j. Siderophores:

Answer 24

Siderophores are molecules that bind and sequester iron from the host, depriving host cells and aiding bacterial growth.

Question 25

How do each of the following virulence factors help a pathogen cause disease?

k. Endotoxins

Answer 25

Endotoxins, particularly lipid A from Gram-negative bacteria, trigger intense immune responses, causing fever, inflammation, and sometimes septic shock.

Question 26

How do each of the following virulence factors help a pathogen cause disease?

l. Capsules

Answer 26

Capsules provide a protective layer around pathogens, making it harder for immune cells to recognize and phagocytize them.

Question 27

How do each of the following virulence factors help a pathogen cause disease?

m. M protein

Answer 27

Found on Streptococcus, M protein prevents phagocytosis and enhances bacterial survival in the host.

Question 28

How do each of the following virulence factors help a pathogen cause disease?

n. Leukocidin

Answer 28

Leukocidin kills white blood cells, weakening the host immune response and promoting pathogen survival.

Question 29

Compare & contrast endotoxins & exotoxins. What diseases use exotoxins?

Answer 29

Endotoxins:
- Not easily inactivated by heat
- Weak antigenicity
- Released only after cell dies
- Produces fever

Exotoxins:
- Lethal in small doses
- Found in both G+ and G-
- Can make a toxoid vaccine
- Proteinaceous

Diseases that use exotoxins
- Anthrax
- Clostridium botulinum
- Clostridium tetani

Question 30

Differentiate between the innate and adaptive immune response.

Answer 30

The innate immune response is the body’s first line of defense against pathogens, providing a rapid but non-specific response to infections.

• Includes physical barriers like skin and mucous membranes
• Includes internal defenses like inflammation, fever, phagocytic cells, and natural killer (NK) cells.
• Does not adapt or provide long-lasting immunity

The adaptive immune response is specific, slower to activate, and has a memory component.

• Involves lymphocytes that recognize specific antigens on pathogens
• Produce antibodies (B cells), and target infected cells (T cells).
• Once exposed to a pathogen, the adaptive response “remembers” it, allowing for a faster and more effective response upon re-exposure.

Question 31

Given a specifics of a type of immune response, determine whether it is part of the innate or adaptive defense.

Answer 31

To identify if a response is innate or adaptive:

• Innate responses are immediate and non-specific, such as fever, phagocytosis, and inflammation.
• Adaptive responses are specific to particular antigens, such as antibody production by B cells and cytotoxic T cell responses against infected cells.

Question 32

What are 2 examples of phagocytic cells?

Answer 32

1. Neutrophils
2. Macrophages

Question 33

What are examples of lymphocytes?

Answer 33

B cells and T cells

Question 34

Describe the first line of defense. Describe the second line of defense.

Answer 34

The first line of defense consists of physical and chemical barriers that prevent pathogens from entering the body.

• Includes the skin, mucous membranes, and their secretions (such as mucus, tears, and saliva), as well as protective chemicals like lysozyme, which breaks down bacterial cell walls, and acidic environments like stomach acid.

The second line of defense activates when pathogens breach the first line. It is part of the innate immune system

• Includes internal responses like inflammation, fever, and the actions of immune cells such as phagocytes and natural killer (NK) cells, which work to destroy pathogens inside the body.

Question 35

How can you distinguish between the first and second line of defense?

Answer 35

The first line is external, aiming to block pathogens at entry points
-Involves passive barriers

The second line is internal, responding once pathogens are inside the body.
- Involves active immune responses to fight pathogens

Question 36

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

a. Skin

Answer 36

a. Skin: The skin acts as a physical barrier with tightly packed cells and secretes antimicrobial peptides and oils that inhibit pathogen growth.

Question 37

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

b. Mucous membranes

Answer 37

b. Mucous membranes: These line body cavities and trap pathogens in mucus, which is then expelled or destroyed by enzymes like lysozyme.

Question 38

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

c. Eyes & ears

Answer 38

c. Eyes & ears: Tears contain lysozyme that breaks down bacterial cell walls, and earwax traps pathogens while preventing their entry.

Question 39

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

d. Nervous system

Answer 39

d. Nervous system: The blood-brain barrier prevents harmful pathogens and toxins from accessing the central nervous system.

Question 40

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

e. Respiratory system

Answer 40

e. Respiratory system: Cilia in the respiratory tract move trapped pathogens in mucus out of the airways, and sneezing or coughing expels them.

Question 41

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

f. Cardiovascular & lymphatic system

Answer 41

f. Cardiovascular & lymphatic system: Blood flow carries immune cells to infection sites,

and lymph nodes filter pathogens for destruction by immune cells.

Question 42

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

g. Digestive system

Answer 42

g. Digestive system: Stomach acid destroys many pathogens, and the gut microbiota outcompetes harmful microbes for nutrients and space.

Question 43

Each of the following has some role in the innate defense mechanism. How does each body area defend against pathogens?

h. Urogenital system

Answer 43

h. Urogenital system: Urine flow and acidic pH in the urogenital tract flush out pathogens and create an inhospitable environment for microbial growth.

Question 44

Describe the roles of each of the following & how each works against pathogens.

a. Interferon

Answer 44

a. Interferon: Interferons are signaling proteins produced by virus-infected cells that warn neighboring cells and stimulate the production of antiviral proteins to block viral replication.

Question 45

Describe the roles of each of the following & how each works against pathogens.

b. Defensins

Answer 45

b. Defensins: Defensins are antimicrobial peptides that create pores in microbial membranes, leading to cell lysis and death.

Question 46

Describe the roles of each of the following & how each works against pathogens.

c. Cytokines

Answer 46

c. Cytokines: Cytokines are signaling molecules that coordinate immune responses by promoting inflammation, recruiting immune cells, and regulating cell activities.

Question 47

Describe the roles of each of the following & how each works against pathogens.

d. Lysozyme

Answer 47

d. Lysozyme: Lysozyme is an enzyme that breaks down peptidoglycan in bacterial cell walls, leading to bacterial lysis.

Question 48

Describe the roles of each of the following & how each works against pathogens.

e. Toll-like receptors

Answer 48

e. Toll-like receptors: Toll-like receptors (TLRs) are proteins on immune cells that recognize pathogen-associated molecular patterns (PAMPs) and activate immune responses like cytokine release.

Question 49

Describe the roles of each of the following & how each works against pathogens.

f. Normal microbiota

Answer 49

f. Normal microbiota: Normal microbiota outcompete pathogens for nutrients and space, produce antimicrobial substances, and stimulate the immune system.

Question 50

Describe the roles of each of the following & how each works against pathogens.

g. Dendritic cells

Answer 50

g. Dendritic cells: Dendritic cells are antigen-presenting cells that capture pathogens, process their antigens, and present them to T cells to initiate adaptive immunity.

Question 51

Describe phagocytosis.

What are some ways that a pathogen is able to avoid phagocytosis?

Answer 51

Phagocytosis: Phagocytosis is the process by which immune cells engulf and digest pathogens or debris using phagolysosomes

Ways pathogens avoid phagocytosis: Pathogens can avoid phagocytosis by:

• producing capsules that inhibit engulfment
• secreting antiphagocytic chemicals

-or surviving within phagosomes by preventing lysosomal fusion.

Question 52

How do neutrophils kill foreign invaders?

Answer 52

How neutrophils kill foreign invaders: Neutrophils kill pathogens by:

• engulfing them through phagocytosis
• releasing antimicrobial chemicals
• or forming neutrophil extracellular traps (NETs) composed of DNA and proteins to trap and kill microbes.

Question 53

What can a differential white blood cell count tell a physician about a patient’s disease?

Answer 53

A differential white blood cell count can indicate the presence of:

• infection
• inflammation
• or disease

by identifying abnormalities in the number or type of white blood cells, such as:

• an increase in neutrophils for bacterial infections
• or increase in eosinophils for parasitic infections.

Question 54

Describe the complement system. What three ways is complement activated?

Answer 54

The Complement System: is a group of proteins in the blood and tissue fluids that enhance immune responses by:
- promoting inflammation
- opsonizing pathogens for phagocytosis
- and forming the membrane attack complex (MAC) to directly lyse pathogens.

Three ways complement is activated:
1. Classical Pathway: by antibodies bound to antigens, linking complement system to adaptive immune response.

2. Alternative Pathway: directly by microbial surfaces, such as lipopolysaccharides, without the need for antibodies.
3. Lectin Pathway: when mannose-binding lectin (MBL) binds to specific carbohydrates on pathogen surfaces.

Question 55

Describe how pathogens are affected by complement.

Answer 55

Disrupting their ability to infect or survive:

1. Opsonization: Complement proteins, such as C3b, coat the surface of pathogens, making them easier for phagocytes to recognize and engulf.
2. Inflammation: Complement components (e.g., C3a and C5a) act as anaphylatoxins, recruiting immune cells to the infection site and triggering inflammation, which enhances the immune response.
3. Cell Lysis: The formation of the MAC by complement proteins (C5b-C9) creates pores in the pathogen’s cell membrane, leading to osmotic imbalance and lysis of the pathogen.
4. Immune Clearance: Complement-tagged pathogens are removed by immune cells or filtered out of the blood by the liver and spleen.

Question 56

Describe inflammation and its effects upon the body.

What triggers inflammation?

Answer 56

Inflammation is the body’s localized response to infection or injury, marked by redness, heat, swelling, pain, and sometimes loss of function.

1. Triggers: Inflammation is triggered by tissue damage or the presence of pathogens, which activate immune cells and release signaling molecules like cytokines and histamine.

Question 57

What are the signs/symptoms of inflammation & how do they arise?

Answer 57

2. Signs/Symptoms:
   • Redness & heat: Caused by increased blood flow (vasodilation) to the area.
   • Swelling: Due to fluid leaking from blood vessels (increased vascular permeability).
   • Pain: From pressure on nerves and inflammatory mediators like prostaglandins.
   • Loss of function: Results from severe swelling or pain inhibiting movement.

Question 58

What is the purpose of inflammation?

Answer 58

3. Purpose: Inflammation isolates the injury, recruits immune cells, promotes tissue repair, and eliminates pathogens.

Question 59

How and why does the body become feverish?

Answer 59

The body becomes feverish when pyrogens (e.g., bacterial toxins, cytokines like interleukin-1) trigger the hypothalamus to increase the body’s “set point” temperature.

This response enhances immune activity, inhibits pathogen growth, and speeds up tissue repair processes.

Question 60

Explain how aspirin works to reduce fever

Answer 60

Aspirin inhibits the enzyme cyclooxygenase (COX), which is responsible for producing prostaglandins.

By blocking prostaglandin synthesis, aspirin prevents the hypothalamus from increasing the body’s set point, thus reducing fever

Question 61

Be able to interpret a result off of a Kirby-Bauer test.

Answer 61

• Positive result (antibiotic susceptibility):
  • Clear zone of inhibition (no bacterial growth) around the antibiotic disk indicates the bacteria are susceptible to the antibiotic.
  • Measure the diameter of the zone of inhibition in millimeters and compare it to standardized charts for interpretation as “susceptible,” “intermediate,” or “resistant.”
• Negative result (antibiotic resistance):
  • Little to no zone of inhibition around the disk indicates the bacteria are resistant to the antibiotic.
  • Growth extends up to the edge of the disk.

Question 62

Kirby-Bauer test key points:

Answer 62

• Larger zones typically mean greater susceptibility
• The test does not measure the strength of the antibiotic, just whether the bacteria are affected by it.

Question 63

Be able to determine whether a disinfectant, antiseptic or antibiotic is effective or not based upon given information.

Answer 63

• Disinfectant: Kills/inhibits microorganisms on non-living surfaces (e.g., bleach).
  • Example: Large clear zone around bleach on agar = Effective.
• Antiseptic: Kills/inhibits microorganisms on living tissue (e.g., hydrogen peroxide).
  • Example: Moderate clear zone = Effective.
• Antibiotic: Kills/inhibits bacteria inside the body (e.g., penicillin).
  • Example:
    Clear zone around antibiotic disk = Effective;
    no zone = Ineffective

Question 64

EXERCISE 18: Solve any given serial dilution problem without a calculator. Review your pre-lab worksheet. This can be figuring out a dilution factor or original cell density from a specific plate count.