Unit 4 – Microbiology Test Questions – Flashcards

Unlock all answers in this set

Unlock answers
question
Portals of Entry for Microbial Infection
answer
Respiratory Tract
Genitourinary Tract (GU)
Gastrointestinal (GI)
Skin
Parenteral Route (Insect Bites)
Placenta
question
Invasiveness
answer
The ability of a microbe to colonize the tissues of a host.

Some bacteria have structural components which act as adhesions/ligands and bind to receptors on host cells- can form biofilms
Examples:
Capsule- Streptococcus mutans
Fimbriae- Escherichia coli
M Protein (wall)- Streptococcus pyogenes
Opa protein (wall)- Neisseria gonorrhoeae
Mycolic acid (wall)- Mycobacterium tuburculosis
A protein (wall)- A protein which binds antiodies by stem region- Staphococcus aureus

Some bacteria use structural components to protect themselves from phagocytosis:
Capsules & Cell Wall Proteins
question
Toxicity
answer
The ability of a microbe to produce a harmful substance such as an exotoxin or endotoxin.
question
Capsules
answer
Prevent phagocytosis
-Streptococcus pneumoniae
-Haemophilus influenzae
-Bacillus anthracis
question
Cell Wall Components
answer
M Protein- resists phagocytosis (streptococcus pyogenes)

Opa protein- inhibits T helper cells (Neisseria gonorrhoeae)

Mycolic acid (waxy lipid)- resists digestion (Mycobacterium tuberculosis)

A protein- Staph. aureus has a protein associated with the wall; "A-protein" which binds antibodies by the stem region.
question
Toxin
answer
Substance that contributes to pathogenicity.
question
Toxigenicity
answer
Ability to produce a toxin
question
Toxemia
answer
Presence of toxin in the host's blood.
question
Toxoid
answer
Inactivated toxin used in a vaccine.
question
Antitoxin
answer
Antibodies against a specific toxin
question
Membrane-Disrupting Toxins
answer
Lyse host's cells by-

1. Making protein channels in the plasma membrane (leukocidins, hemolysins (alph & beta), streptolysins

2. Disrupting phospholipid bilayer.
question
Superantigens
answer
Cause an intense immune response due to release of cytokines from host cells.

Symptoms: fever, nausea, vomiting, diarrhea, shock and death
question
Endotoxins and the Pyrogenic Response
answer
1. A macrophage ingests a gram-negative bacterium.
2. The bacterium is degraded in a vacuole, releasing endotoxins that induce the macrophage to produce cytokines IL-1 & TNF-alpha
3. The cytokines are released into the bloodstream by the macrophages, through which they travel to the hypothalamus of the brain.
4. The cytokines induce the hypothalamus to produce prostaglandins, which reset the body's "thermostat" to a higher temp, producing fever.
question
Enzymes Produced as Virulance Factors
answer
Hyaluronidase, Kinases, Coagulases, Collagenase, Ig-A proteases, Keritinase
question
Hyaluronidase
answer
called the "spreading factor"- breaks down hyaluronic acid, a tissue "cement" found particularly in connective tissue
question
Kinases
answer
enzymes that dissolve fibrin clots formed in tissue in response to trauma allowing organisms to invade
question
Coagulases
answer
enzymes that initiate clot formation (fibinogen->fibrin) in plasma walls off organisms and prevents phagocytosis. (Staph. aureus)
question
Collagenase
answer
an enzyme which breaks down collagen, a binding protein found in connective tissue throughout the body. (Gang green)
question
Ig-A Proteases
answer
destroy IgA (mucosal antibody) antibodies
question
Keratinase
answer
digest keratin- protein found in skin and nails
question
Exotoxins
answer
Proteins produced inside pathogenic bacteria, most commonly G+ bacteria, as part of their growth & metabolism. They are then secreted or released into the surrounding medium following lysis.

Heat sensitive; strongly anitigenic (immunize w/taxoid); can be classified by action; highly toxic.

A-B (diptheria & botulism)- inhibit protein synthesis)
Membrane Disruption- Hemolysins & Leukocidins
Superantigens- Staph. enterotoxin (in gut)

Symptoms: fever, cardiovascular disturbances, diarrhea & shock. (vary by which type)
question
Endotoxins
answer
The lipid portions of lipopolysaccharides (LPSs) that are part of the outer membrane of the cell wall of G- (Lipid A). They are liberated when the bacteria die and the cell wall breaks apart during lysis. Stimulate macrophages to release cytokines in very high, toxic concentrations.
Heat resistent; non-specific generalized action; weak antigen (antibodies are nonprotective, therefor, no toxoid); no antitoxin, but drug "Zovan" counteracts clotting & inflammation
Responsible for meningococcal meningitis & typhoid fever

Symptoms: chills, fever, weakness, generalized aches & in some cases, shock & death. Can also induce miscarriages.
question
Innate Immunity
answer
immunity that is present at birth.
question
First line of defense
answer
Intact skin
Mucous membranes and their secretions
Normal Microbiota
question
Second line of defense
answer
Phagocytes, such as neutrophils, eosinophils, dendritic cells and macrophages

Inflammation

Fever

Antimicrobial substances
question
Adaptive Immunity (3rd line of defense)
answer
Specialized lymphocytes: T cells & B cells

Antibodies
question
Cytokines
answer
proteins that regulate the intensity and duration of immune responses; recruit other macrophages & dendritic cells to isolate & destroy microbes as part of the inflammatory response; also activate T cells & B cells in adaptive immunity
question
Innate Immunity (function)
answer
Toll-like receptors (TLRs) attach to Pathogen-associated Molecular Patterns (PAMPs) and induce cytokines that regulate the intensity & duration of the immune response.
question
Mechanical Defenses in Innate Immunity
answer
Skin- epithelial barrier, keratin
Respiratory Tract- epithelial barrier; mucous membrane; cilia; haris in nares; coughing; sneezing
Gastrointestinal Tract- epithelial layer' mucous membranes; peristalsis (smooth muscle contraction)
Genitourinary Tract- epithelial barrier; mucous membranes; urine flow; length of urethra & ureters; cervical barrier; vaginal secretions
question
Chemical Defenses in Innate Immunity
answer
Skin- fatty acids in sebum; low pH; low moisture; high salt; lysozome; interferons
Respiratory Tract- lysozome; salt in tears; interferons
Gastrointestinal Tract- low pH; bile salts; gastric juices; lysozome; interferons
Genitourinary Tract- low pH; interferons
question
Cellular Defense Mechanisms
answer
Phagocytosis

Normal Microbiota

Inflammation

Fever

Interferons
question
Phagocytosis
answer
the ingestion of a microorganism or substance (such as debris) by a cell.

Process:
chemotaxis (chemical attraction)->Ingestion of microbe by phagocyte->Digestion of ingested microbe by enzymes (lysosome)-> Discharge of waste materials
question
Inflammation
answer
Function- Destruction of pathogen, confinement of injured area, repair of injured tissue

Triggers- injury to host tissue

Responsible Cells- basophils, mast cells & platelets

Signs: redness, swelling, pain, heat

Stages: vasodilation & increased permeability in blood vessels; phagocyte migration & phagocytosis; repair

Chemicals released: Histamine, Kinins, Prostaglandins, Leukotrienes
question
Fever
answer
ADVANTAGES:

Increases transferrins, decreasing iron available to microbes

Increases IL-1 activity, thus increasing T-cell production

Intensifies Interferon

Increases metabolic rate which may help w/body reactions or hurt w/acidosis

Slows growth of some pathogens, but will NOT kill bacteria

DISADVANTAGES:

Tachycardia
Acidosis (metabolizing fat instead of sugar)
Dehydration
44-46 degrees is fatal
question
Interferons
answer
Proteins produced in small amounts by specific host cells (host specific, not virus specific).

Types- Alpha, Beta & Gamma

"Paul Revere" cytokines that warn that a virus is present. Newly warned neighbor cell then produces anti-viral proteins (AVPs) which interfere with viral replication.
question
Complement System
answer
defensive system consisting of over 30 serum proteins found in normal serums.
question
What activates the 3 compliment pathways?
answer
1. Antigen Antibody Complex
2. Chemical complexes on the surface of foreign cells.
3. Lectins- proteins produced by the liver
question
What are the actions of complement?
answer
1. Opsonization or immune adherence (enhanced phagocytosis)
2. Membrane attack complex (cytolysis)
3. Attract phagocytes (Stimulate inflammation)
question
Neutrophils
answer
Phagocytosis

(70% of white blood cells)
question
Basophils
answer
(mast cells) Produce inflammatory chemicals: histamine, leucotrienes, prostaglandins
question
Eosinophils
answer
Produces toxic proteins against certain parasites, some phagocytosis

Numbers increase during an allergic response.
question
Dendritic Cells
answer
Derived from monocytes; phagocytosis and initiation of adaptive immune response-
APC (anitgen presenting cells)
question
Monocytes
answer
phagocytic as mature microphages- APC
question
Lymphocytes
answer
NK (natural killer cells)- Lymphocite cells without T or B cell markers that are NOT antigen specific. They have receptors for the Fc region of IgG antibodies. When they detect a cell with numerous IgG antibodies attached they attack it in the manner of the CD_8 cytotoxic cell using perforin and proteases to induce apoptosis. This is called antibody-dependent cell mediated cytotoxicity (ADCC). This is usefull in controlling large parasites too large to be engulfed by phagocytic cells.

Involved in adaptive immunity.
question
Chemicals Released by damaged cells
answer
Histamine- vasodilation, increased permeability of blood vessels

Kinins- Vasodilation, increased permeability of blood vessels

Prostaglandins- Intensity histamine and kinin effect

Leukotrienes- Increased permeability of blood vessels, phagocytic attachment
question
Opsonization
answer
The enhancement of phagocytosis by coating microorganisms with certain serum proteins (opsonins); also called immune adherence
question
IgM
answer
1st responder; pentamer
question
IgA
answer
in secretions; dimer
question
IgE
answer
allergic reactions; worms
question
IgG
answer
80% of serum antibodies; able to cross placenta & found in breast milk
question
T cells
answer
Cell-mediated immunity
question
B cells
answer
Descendents of B cells (plasma cells)- produce antibodies
question
T-lymphocytes
answer
mature in thymus; can be divided into 2 major subsets- CD4+ (helpers) & CD8+(cytotoxic)
question
CD-4 cells
answer
also known as TH or T-helper cells; once activated by antigen exposure they differentiate into 2 populations- TH-1s & TH-2s.
question
TH-1
answer
produce cytokines that activate macrophages, stimulate production of antibodies that promote phagocytosis & enhance complement; activates eosinophils.
question
TH-2
answer
produce cytokines that are primarily associated with antibody production, especially IgM & IgE; activates eosinophils.
question
CD-8 cells
answer
activated by dendritic cells & TH-1 cells to become CTLs (cytotoxic T lymphocyte), which release cytotoxins such as perforin and proteases. Perforin facilitates penetration of proteases called granzymes which induce apoptosis in the target cell- an abnormal host cell causing its death by minimizing inflammation or spread of a virus to other cells.
question
T-regulatory cells
answer
appear to suppress other T-cells, secrete IL-10 and regulate the immune response. They combat autoimmunity and protect the intestinal bacteria from the immune system. They are a subset of the CD-4 cells and also carry the CD-25 marker.
question
Superantigens
answer
relatively nonspecific antigens that indiscriminately activate many T-cell receptors at once, producing a response harmful to the host. Examples of such antigens are the enterotoxins of Staphylococcus aureus and the toxin of toxic shock syndrome.
question
Cytokines
answer
a small protein released from human cells that regulates the immune response; directly or indirectly may induce fever, pain or T-cell proliferation.
question
Lysosome
answer
an organelle containing digestive enzymes
question
Active Immunity
answer
when a person is exposed to microorganisms or foreign substances and the immune system responds.
question
Passive Immunity
answer
when antibodies are transferred from one person to another. Only lasts as long as the antibodies are present- in most cases, a few weeks.
question
Antiserum
answer
A blood-derived fluid containing antibodies.
question
M (microfold) cells
answer
Intestinal cells that take up and transfer antigens to lymphocytes.
question
Haptens
answer
A substance of low molecular weight that does not cause the formation of antibodies by itself, but does so when combined with a carrier molecule.
question
Clonal Selection
answer
The development of clones B and T cells against a specific antigen.
question
Apoptosis
answer
The natural programmed death of a cell; the residual fragments are disposed of by phagocytosis.
question
Hypersensitivity
answer
An altered, enhanced immune reaction leading to pathological changes; also called allergy
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New