Medical Microbio Midterm 1

What does the gram stain differentiate between?

Gram positive and gram negative

What is the difference between gram-positive and gram-negative bacteria?

Gram-positive bacteria lack an outer membrane but are surrounded by layers of peptidoglycan many times thicker than in gram-negative

List the steps of testing for gram positive or gram negative bacteria. Which step is most critical?

1) Application of crystal violet (purple dye)

2) Application of iodine (mordant)

3) Alcohol wash (decolorization)

4) Application of safranin (counterstain)

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Step 3 is most critical

Gram + stains purple

Gram - stains pink

How do you stain acid-fast bacteria?

1) Stain w/ Carbol-Fuschin

2) Destain w/ hydrochloric acid/isopropanol

3) Counterstain w/ methylene blue

4) AFB bacteria remain bright red b/c carbol-fuschin stain is retained by a waxy lipid layer

What are the 4 postulates of Koch?

1) Microbe is present in diseased tissue but absent from healthy tissue

2) Microbe must be isolated and maintained in a pure culture

3) Inoculation of the cultured microbe into a susceptible host should reproduce original symptoms

4) The same microbe must be isolated again from the inoculated diseased host

What is the first barrier of defense against foreign objects and organisms?

epithelium

What is the function of skin-associated lymphoid tissue (SALT)?

Provides the skin w/ immune surveillance that effectively prejudices against the development of the cutaneous neoplasms and persistent infection w/ intracellular pathogens

What are the functions of these defenses?

What is the composition of mucosa?

epithelial cells

basal lamina (ECM)

lamina propria

What do junctional complexes prevent?

Passage of bacteria past the epithelial layer

What does rapid turnover of mucosal cells do?

Removes adherent bacteria

What cells of mucosa mainly secret mucus?

Goblet cells

What are the 3 different mechanisms antimicrobial proteins use to inhibit/kill bacteria?

1) disrupting bacterial membrane

2) disrupting bacterial cell wall

3) sequestration of nutrient

What does over-supplementation of iron lead to?

susceptibility to infection

Why would taking antibiotics for a prolonged period of time be harmful?

Antibiotics could be disruptive to normal microbiota and can increase susceptibility to certain types of infection

Define pathogen, allergen, and antigen

Pathogen: infectious agent that causes disease

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Allergen: substance that induces immune response against otherwise harmful stimuli

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Antigen: substance that induces production of antibodies

In terms of immunity, what occurs in the bone marrow?

The thymus?

The spleen, lymph nodes, mucosa-associated lymphoid tissue (MALT)?

Bone marrow: production of immune cells; development and maturation of B cells

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Thymus: development and maturation of T cells

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Spleen, lymph nodes, MALT? sites for T and B cell activation

What are the three different types of immune cells? And what are their functions?

1) Leukocytes: cells of adaptive immunity, recognize antigens and develop (differentiate) into cells that perform defense functions

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2) Antigen-presenting cells: cells that capture antigens and display them to lymphocytes

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3) Effector cells: leukocytes (white blood cells) or lymphocytes that eliminate microbes

Explain the difference between innate and adaptive immunity.

What does innate immunity respond to?

Microbes

Injured tissues or dead cell

In terms of innate immunity, what is the function of a dendritic cell?

A dendritic cell is an antigen presenting cell, serving as a bridge to pass on info from innate to adaptive immunity.

The two mechanisms for how phagocytes kill bacteria are

Nonoxidative and oxidative

How do natural killer cells induce apoptosis?

By secreting perforins and granzymes

What are the three major types of PRRs?

1) TLRs: toll-like receptors; interacts w/ bacterial or viral PAMPs

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2) NLRs: nucleotide-binding oligomerization domain (NOD)-like receptors; interacts w/ bacterial PAMPs

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3) RLRs: retinoid acid-inducible gene I (RIG-I)-like receptors; interacts w/ viral PAMPs

What is the localization, ligand, and origin of the ligand in TLR3, TLR4, and TLR5?

What pathway do both NOD1 and NOD2 activate?

NF-kB pathway

What pathway do RIG-1 and MDA5 activate?

IFN pathway

How does the complement system activate?

via proteolytic cleavage

Name the three pathways that initiate complement activation?

1) classical pathway (antibody crosslinking)

2) mannose-binding lectin pathway (MBL binding to bacterial cell wall components)

3) alternate pathway: serum C3 activation, C3b direct binding to bacteria surface and additional complement system processing

Name 3 functions of complement

1) Opsonization: coating of foreign objects to promote phagocytosis

2) Forms membrane attack complexes (MAC) to kill bacteria

3) Complement cytokines: increase vascular permeability and also activates immune cells

What are cytokines/chemokines? And what is their function?

soluble glycoproteins; regulate activation of immune cells and recruitment to location of infection

Name the 4 stages of transmigration

1) Rolling adhesion

2) tight binding

3) diapedesis

4) migration

Four clinical conditions of innate defenses

1) systemic inflammatory response syndrome (SIRS)

2) sepsis

3) septic shock

4) DIC: disseminated intravascular coagulation

Which of the following is an example of host physical barriers?

a) skin and mucosa

b) antimicrobial proteins

c) human microbiota

d) all of the above

d) all of the above

If the gram staining is purple, the bacteria is

a) gram positive

b) gram negative

c) inconclusive

a) gram positive

Which of the following steps is critical in determining gram-positive vs gram-negative?

a) application of iodine

b) alcohol wash (decolorization)

c) application of safranin

d) application of crystal violet

b) alcohol wash (decolorization)

Gram-positive differs from gram negative by having thinner peptidoglycan

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True or False

False. Gram-positive has a thicker peptidoglycan layer

Aerobic metabolism means oxygen is required

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True or False

True

Mycolic acid is present in acid-fast bacteria, a type of gram-positive bacteria

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True or False

True

Which of the following is one of the difficulties for Koch’s postulates?

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a) time consuming

b) very expensive

c) some are hard to culture

d) has to be done multiple times

c) some are hard to culture

Microbial nucleic acid of the pathogen should be found in all organs

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True or False

False

Which of the following is not a port of entry for bacteria?

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a) gastrointestinal

b) respiratory

c) skin

d) none of the above

d) none of the above

The mucous membrane in skin and intestines is a critical component to protect us from outside infections

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True or False

True

What is the largest organ in the body?

Skin

Skin is made up of layers known as: epidermis, dermis, and subcutaneous tissue

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True or False

True

Dry acidic environment defense helps with what function

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a) prevents bacterial growth

b) immune defense SALT

c) competes with photogenic bacteria

d) promotes bacterial growth

a) prevents bacterial growth

Antimicrobial proteins and lipids defense helps w/ what function?

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a) prevents bacterial growth

b) immune defense SALT

c) protects hair follicle and kills bacteria

d) prevents bacterial colonization

c) protects hair follicle and kills bacteria

Which of the following is NOT a composition of mucosa?

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a) epithelial cells

b) basal lamina (ECM)

c) lamina propria (connective tissue)

d) none of the above

d) none of the above

What is the purpose of cilia in the mucosa?

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a) kill bacteria w/ secretions

b) push stuff away

c) engulf dead cells

d) inflammation

b) push stuff away

The stomach has what defense

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a) tears

b) mucus

c) acidic environment (pH=2)

d) sphincter

c) acidic environment (pH=2)

The colon has what type of defense

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a) tears

b) acidic environment

c) peristalsis

d) urine flushing

c) peristalsis

Disrupting bacterial cell wall and membrane are ways antimicrobial proteins inhibit bacteria

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True or False

True

Microbiome is the microbial cell

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True or False

False. Microbiome is the collection of microbes, such as bacteria, fungi, viruses, and their genes, that naturally live in our bodies and inside us.

Microbiota are symbionts with their host

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True or False

True

A substance that induces immune response against otherwise harmless stimuli

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a) pathogen

b) allergen

c) antigen

d) all of the above

b) allergen

Substance that induces production of antibodies

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a) pathogen

b) allergen

c) antigen

d) all of the above

c) antigen

The immune system goes from a resting (inert) stage to an activation when induced with

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a) pathogen

b) allergen

c) antigen

d) all of the above

d) all of the above

Where does production of immune cells and development and maturation of B cells occur?

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a) bone marrow

b) thymus

c) spleen

d) lymph nodes

a) bone marrow

Cells of adaptive immunity that recognize antigens and develop into cells that perform defense functions

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a) antigen-presenting cells

b) effector cells

c) lymphocytes

d) all of the above

c) lymphocytes

Leukocytes (WBC) or lymphocytes eliminate microbes

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a) lymphocytes

b) antigen-presenting cells

c) effector cells

d) all of the above

c) effector cells

Development and maturation of T cells occurs in the

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a) bone marrow

b) thymus

c) spleen

d) lymph nodes

b) thymus

Which immunity is responsible in removing infectious agents in the first 0-96 hours

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Innate or Adaptive

Innate

The adaptive immunity is the first line of defense

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True or False

False. Innate immunity is the first line of defense

B cells and T cells are part of adaptive immunity

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True or False

True

Which of the following is part of the adaptive immunity?

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a) present at birth

b) specific defense

c) no memory

d) fast response

b) specific defense

The innate cells help w/ activating the adaptive immune cells to further target immune responses

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True or False

True

Monocytes are the precursors of macrophages

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True or False

True

Enhance anti-parasite effects and allergic reactions

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a) basophils

b) eosinophils

c) mast cells

d) dendritic cells

a) basophils

Release histamine for allergic reactions

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a) basophils

b) eosinophils

c) mast cells

d) dendritic cells

c) mast cells

Macrophages and dendritic cells are adaptive cells that are types of antigen presenting cells

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True or False

False. B and T cells are adaptive cells.

Cells that engulf foreign particles

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a) neutrophils

b) phagocytes

c) natural killer cells

d) dendritic cells

b) phagocytes

Antimicrobial peptides that kill bacteria and lysosomal enzymes that degrade bacteria are types of oxidative mechanisms

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True or False

False. Antimicrobial peptides and lysosomal enzymes are nonoxidative.

Natural killer cells ingest bacteria.

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True or False

False. Natural killer cells induce apoptosis of infected host cells.

Cells that induce apoptosis of infected host cells

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a) dendritic cells

b) phagocytes

c) natural killer cells

d) neutrophils

c) natural killer cells

Pathogen associated molecular patterns help determine non self cells

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True or False

True

Lipopolysaccharide in gram-negative bacteria and lipoteichoic acid (LTA) in gram-positive bacteria are examples of PAMPs

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True or False

True

What is a major type of Pattern Recognition Receptors

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a) toll-like receptors

b) nucleotide binding oligomerization domain-like receptors

c) retinoid acid inducible gene 1-like receptors

d) all of the above

d) all of the above

Which toll like receptor’s ligand is in the flagellin

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a) TLR3

b) TLR4

c) TLR5

d) TLR6

c) TLR5

The complement system is activation through proteolytic cleavage

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True or False

True

Antibody crosslinking is part of which complement activation pathway

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a) classical

b) mannose-binding lectin

c) alternative pathway

a) classical

Without pathogens, C3b is activated (for regulation)

False. C3b cannot activate without pathogens

Which part is responsible for making a hole in the membrane?

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a) membrane attack complex

b) C3b

c) C8

d) C9

a) membrane attack complex

Which of the following is responsible for recruitment of cells to location of infection

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a) cytokines

b) chemokines

c) all of the above

d) none of the above

c) all of the above

IL-1, IL-6, and TNF-gamma interact with the hypothalamus AND adrenal glands

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True or False

True

Main host specific defense against extracellular infections, antibody mediates, and specific

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a) cell-medicated

b) humoral

b) humoral

Antibodies known as immunoglobulins are made of glycoproteins

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True or False

True

T cells called plasma cells make antibodies

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True or False

False. B cells make antibodies

Antigen-binding region (Fab) and the constant region (Fc) are part of

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a) T cells

b) neutrophils

c) antibodies

d) dendritic cells

c) antibodies

The Fab segment consists of “__” that bind to antigens

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a) constant region

b) variable region

c) both

d) none

c) both

The Fc region of some antibodies can interact w/ the C1 and activate complement system

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True or False

True

The red represents

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a) light chain

b) heavy chain

c) constant

d) variable

a) light chain

Bacterias can’t exist independently

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True or False

False.

When bacteria are in dormant form resistant to environmental stresses

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a) protozoa

b) activation

c) endospores

d) biofilm

c) endospores

Dense, multiorganismal layers of bacterial cells attached to surfaces

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a) endospore

b) activation

c) NK cells

d) biofilms

d) biofilms

Flagellin are highly non-antigenic

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True or False

False

Flagella uses ATP as an energy source to inititiate rotation

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True or False

True

What element is essential for the growth of most bacteria?

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a) oxygen

b) iron

c) hydrogen

d) carbon

b) iron

Coating with host antigen is a type of immune evasion that is like camouflage

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True or False

True

Bacteria can either escape humoral immune response or respond to different environments within host

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True or False

True

What is a first line of defense for bacterial colonization?

sIgA (secretory IgA)