Microbiology Final Flashcards
What is an antigen?
Stimulates an immune response: A substance the body recognizes as forign
Non-self
immunogenic - stimulates an immune response (immunogen)
large, complex molecules
Composed of antigenic determinants - the part of the antigen that actually stimulates and reacts with the immune response
What parts of the bacteria have antigenic determinants?
Proteins, lipids, mucleic acids, CHO
Flagellum
Pilli
**Proteins make the best antigenic determinant
What is a hapten?
molecule that, by itself, is too small to be immunogenic
**When attached to a larger molecule like a protein then it can be imunogenic
Properties of immune responses
Recognition - of self vs. non-self
- self = host tissue
- Non-self = forign substances
Specificity - each immune response is directed toward a specific ag but the response to one ag doesn’t affect the response to another. Cross Rx occurs if two ag’s are similar
Diversity - The immune system can respond to many different Ag’s (>1 billion)
Memory - The immune system can recognize ag’s it has previously encountered. It responds quicker the second/subsequent time it encounters that ag
Define tolerance
the host doesn’t mount an immune response to self ag’s under normal circumstances
B lymphocytes (B cells)
Arise in bone marrow; primarily involved in antibody mediated immunity
Reside in the lympohid organs and in the bloodstream
Receptor: an Ab molecule that recognizes and binds a specific Ag
T lymphocytes (T cells)
Arise in thymus gland; Primarily involved in cell-mediated immunity
Reside in lymphoid organs and in the bloodstream
Receptor: T-cell receptor, receptor that recognizes and binds a specific Ag.
Cell-mediated Immune Response
- Ag is recognized and phagocytosed by macrophages- Ag presenting cells
- Macrophages fins corresponding helper T cell; presents Ag (binds)
- Helper T cells sound the alarm (CD-4+) - interleukin-1 stimulate T-cells to mature; interleukin-2 stimulates T-cells to rapidly divide
- The alarm encourages the production and rapid division of cytotoxic T-cells
- Cytotoxic T-cells find and infect cells that present Ag and lyse them
What are cytokines?
Cell communication molecules; released by one cell to signal or stimulate another cell.
Released by helper T cells
What are perforins?
Released from cytotoxic T cells; forms pores in target cell membrane
What are Antibodies?
Proteins that circulate in the bloodstream
sythesize and secreted by plasma cells
Each Ab is specific for 1 particular antigenic determinant
React with Ag that is outside host cell like toxins, bacterial surfaces, viruses
Plasma cells
B lymphocytes that circulate in the bloodstream and synthesize & secrete Ab
Antibody mediated (humoral) immune response
- Macrophages comes across an antigenic determinant
- Macrophage must find appropriate B cell with matching surface proteins to the antigenic determinant
- Helper T cells help activate and encourage reproduction of B cells by means of cytokines which give rise to plasma cells
- Ab find and antigen and mark for destruction
- Marked antigens are then easier to phagocytize
- Memory B cells created to anticipate the reappearance of certain Ag
IgM Ab
Pentamer
First to appear esp. in primary Ab response
In bloodstream on surface of B cells
IgG
Monomer
Major circulating Ab
Appears later than IgM esp. in secondary Ab response
Crosses placenta
IgA
Monomer/dimer
occurs in serum and in secretions
Secreted into mucosal surfaces, in tears, saliva, colostrum
IgE
Monomer
On surface of mast cells and plays a role in allergenic reactions
IgD
Monomer
Surface receptor on B lymphocytes
Primary Ab response
- Occurs first time Ag is encountered
- Ab begins to appear in 5 days
- First Ab is IgM then wanes
- Next Ab is IgG appears in greater amount
Secondary Ab response
- Occurs at second/subsequent Ag exposure
- Results from B memory cells
- Occurs more quickly than primary response
- Produces more Ab than primary response
- Lasts longer than primary response
Neutralizing antibodies
Viruses clump them together so they cannot enter cell
Antitoxins - alters the active sites and masks their toxicity, ^ toxins size making it easier to phagocytize
Block adhesions-binds adhesins, prevent from attaching and colonizing host
Opsonize - enhance phagosytosis; handle
Agglutinate - clump insoluble particles together making them easier to phagocytize
Precipitate - Clump soluble molecules together, making them easier to phagocytize
Activate complement - forms MAC, resulting in lysis & killing of pathogen
Natural active immunity
- Define
- Whats given to host
- Immune response
- Immune response develops naturally within a host
- Example: Getting the chicken pox
- What’s given to host: You get the virus
- Immune response is fast; after initial exposure
- Immune response is either short or long lived
Natural passive immunity
- Define
- What’s given to host?
- Immune response
- Immune response develops naturally and is provided to the host
- Example: breast milk
- What’s gien to host: Maternal Ab provided to newborn
- Immune response is fast
- Immune response lasts for 3-6 months
Artificial active immunity
- Define
- Example
- Immune response
- Immune response develops after an intentional or purposful action within the host
- Example: vaccine
- What’s actually given to host: piece of a bacterium or cead virus
- Immune response is fast
- Immune response lasts long
Artificial passive immunity
- Define
- Example
- immune response
- Immune response develops after an intentional or purposful action and is provided to host
- Snake vaccine
- immunity taken from someone else (Ab)
- Immune response is fast
- Immune response is short lived
Inactivated vaccine
- Define
- Advantage
- Concern
- Whole bacterium or virus is killed and given as an Ag
- Advantage: No danger or getting the disease from vaccine
- Concern: Releases endotoxins; short lived immunity
Attenuated Vaccine
- Define
- Advantage
- Concern
- Live organism with reduced pathogenicity is given causing a small subclinical infection
- Advantage: longer lasting immunity
- Concern: You can get sick
Subunit vaccine
- Define
- Advantage
- Concern
- Only part of the organism get infected
- Advantage: Won’t get sick;fewer side effects
- Concern: Short term immunity
Toxoid
Inactivated toxin given as Ag; has lost it’s toxic activity but retained it’s immunogenicity
EX: tetanus
Conjugated vaccine
A subunit is linked or conjugated to another molecule to increase its immunogenicity
Hapten is connected with a protein to elict greater immune response
EX: Hib vaccine
Synthetic/recombinant vaccine
A subunit or part of an organism if produced using genetic engineering
EX: hep. B vaccine & gardasil
Herd immunity
Means that it’s difficult for a disease to spread in the population if a sufficient number of individuals are immunized
90% have to be vaccinated
Adverse reactions to vaccines
Soreness at injection site, raised & red; mild fever, malaise
Due to hypersensitivity or allergy to vaccine components
wheel and flare
Hypersensitivity
an increased, exaggerated or inappropriate immune response that negatively affects the host
“Too much of a good thing”
A host is sensitized if they are hypersensitive to a particular Ag.
Allergy or allergic response
Ag is often something the host should be tolerant to
Hypersensitivity exposure
Sensitizing dose = 1st exposure; usually a large dose
Elicting dose or provocative dose = 2nd or subsequent exposure; can be quite small
Type 1 hypersensitivity
immediate-type hypersensitivity
involves IgE on the surface of mast cells and basophils and result in as immediate pharmacologic response
Ag is often an allergen
IgE binds to the surface of cells:
- Mast cells - CT cells found around respiratory & GI tracts, near blood vessels
- Basophils - granulocytes that circulate in the bloodstream
Degranulation
A rapid release of chemical substances that induce an allergic response from mast and basophil cells
Histamine dilates capillaries; immediate onset
- increase vascular permeability
- constricts smooth muscle
- increase mucus secretions
- Stimulates nerve endings > itch & pain
This reaction is called anaphylaxis
Localized anaphylaxis - local Ag exposure
Rx occurs where allergen enters body
Skin: Wheel & flare - skin Rx characterized by a swollen white center surrounded by redness & itching
Respiratory tract: bronchi constriction, weezing, cough, fluid in lungs, mucous
Digestive tract/food allergy: vomit, diahrea
Treatment: antihistamine stops the release of histamine
Asthma
Systemic anaphylaxis - Ag in bloodstream
Systemic Rx –> anaphylactic shock: blood vessels suddenly dilate and become more permeable causing a drop in blood pressure
Can be rapidly fatal (15 min)
EX: Epi pen
Treatment: desensitization-repeated injection of small amounts of denatured Ag. May prevent B cells from maturing into IgE. May induce tolerance to the Ag
Controlling type 1 hypersensitivity
Avoid contact with allergen
Antihistamine
Desensitization- repeasted injections of small amounts of denatured Ag; prevent B cells from maturing into IgE secreting plasma cells; May induce tolerance ot the Ag
Block Ab- immunize with the denatured allergen to produce serum IgG; Serum IgG blocks allergen from reaching IgE
Type 2 cytotoxic hypersensitivity
Ab usually IgG or IgM
Ag on the surface of cells
Compliment
Adverse effects appear within min-hrs
Hemolytic disease of newborn
Rh (rhesus) Ag on erythrocytes
Treatment: shot of RhoGAM - anti Rh Ab
- administered to mother at birth of first Rh+ child
- Binds up Rh Ag, preventing it from stimulating mother’s immune system
- So that Rh Ab is not produced
- Artificial Passive Immunity
Type 3 immune complex hypersensitivity
Ags - usually soluble in lrg amounts entering host
Abs - IgG or IgM
Complement
PMN’s - neutrophils
Adverse effects appear within hrs-days
Serum sickness
Type 3
Ab develops to Ags in an antiserum preperation
Next administration: Ag-Ab complexes form and damage kidneys
Type 4 cell-mediated hypersensitivity
Ags-usually displayed on cells or have become attached to cell surfaces
Sensitized T cells
- Generated upon first exposure to Ag
- React on second exposure to Ag
Often observed as a skin reaction because they are associated with Ag being on the skin
Delayed; starts after >12 hrs; maximal rx 24-72 hrs after Ag exposure. Some takes weeks to develop
Contact dermatitis
Type 4
CMI response develops to Ag deposited ont he skin
EX: poison ivy
Test with allergen patch
Treatment: antiinflamatory, steroids
Tuberculin sensitivity
type 4
CMI response develops from infection
tuberculin skin test provides second exposure to Ag
Positive test means you’ve been exposed
Granulomatous hypersensitivity
type 4
“walled off”
macrophages have phagocytosed pathogens but can’t kill them
Sensitized T cells respond to form a granuloma
Autoimmune disorders
host mounts immune response against its own Ags, cells, or tissues
host should be tolerant to “self”
“a good thing turned bad”
Auto Ag - the self Ag to which the host is responding
Immune response may involve auto Ab or cellular response
Rx typically results in destruction of host cells or tissues
How does autoimmune disprder develop?
antigenic mimicry - cross-rx btw a forign and self Ag
Tolerance failed to develop- cells that respond to self ags were not destroyed in development of the immune system
Genetic factors
Auto immune disorders
Myasthma gravis
- affects skeletal muscles; unable to contract properly
- Auto Ab against neurotransmitter receptor at nerve-muscle junction
Rheumatoid arthritis
- Auto Ag unclear
- Immune complexes form in the joints
Systemic lupus erythematosus
- Ab to nuclear compoments of host’s cells
- Immune complexes form in the skin, organs
Immunodeficiency Diseases
Immune system responds inadequately to an Ag due to a genetic or acquired defect in the immune system
“too little of a good thing”
Primary immunodeficiency= genetic or developmental defect in immunity
Secondary immunodeficiency= results from damage to the immune cells after they have developed normally
Define sterilization
the killing or removal of all life forms
Define disinfection
Reduction in the amount of pathogenic organisms
Microbial death curve
definite proprtion of organisms die in a given time interval
EX: 20% die one minute; 20% will die the next minute
The more microbes present the more time needed to kill them all so you want to clean before sterilizing.
Nevery really reach 0.
Microbial killing with heat
function of time and temperature
- the higher the temp. the shorter the time
- The lower the temp. the longer the time
- Depends on the type of organism
- Depends ont he type of material
- The presence of organic matter shields oragniams from heat
- Overkill- use more force that was is needed
Microbial killing with Dry heat
Standard conditions: 160 C for 2 hrs.
- penetration is slow
- Mechanism: oxidizes molecules
- Materials must be heat stable
- Doesn’t corrode or dull sharp instruments
- Sterilze dentures and surgical instruments
Microbial killing with moist heat
standard conditions for boiling water:
- Vegatative cells: 100 C for 10 minutes
- Spores: 100 C for >2 hrs.
- Water conducts heat more effectively
- May or may not sterilize
- Mechanism: denatures proteins & other maccromolecules
Microbial killing with autoclave
Moist heat and pressure
Standard conditions: 121 C for 15 min. at 15lb/in2
- pressure increases temp. over 100C
- pressure helps steam/heat to penetrate
- Limitations: items wrapped in foil and urea broth
Pasteurization removes pathogens
- Targeted at removing oathogens and reducing overall bacterial population
- Not effective against spores
- does not sterilize
standard conditions (milk): 62.9 C for 30 min.
What is ultrapasteurization?
What is UHT pasteurization?
UP: over heating - 82 C for 30 min.
increased shelf life
UHT: 140 C for 3 sec.
Filtration traps microorganisms
- liquid or gas is passed through a membrane filter which traps micrpprganisms; .2 pore size
- May or may not sterilize; viruses pass through still.
- Use on heat sensitive liquids, culture media, iv solutions, beverages, gases.
Limitations:
- fliters may clog
- Breaks, cracks or flaws in filter
- Some molecules bind to filter
HEPA filter- high efficiency particulate filter
- air filtration for clean rooms/surgical suites/burn units
- often used with uv light for sterility
UV light control on microbial growth
wavelength of 100-400nm
UV light forms thymine dimers in DNA
Requires direct, close contact
useful on air and surfaces
Limitations:
- doesn’t penetrate
- less effective at greater distances
- Damage skin and eyes
Ionizing radiation can sterilize materials
x-rays & gamma rays
expose materials in lead-lined chamber
Mechanism: excites electrons, creating ions–> inactivate proteins & amino acids
Penetrates well & useful on heat sensitive items
Approved for preservation of food
- kills foodborne oathogens
- concerna about safety of workers
- concerns about saety of consumers
Define sanitation
reducing the microbial population to a safe level, as determined by some sort of standard
Define degerming
removing organisms from a surface
define -cidal and -static
- cidal: kills organisms
- static: inhibits the growth of
Chemical agent: Halogens
Mechanism:
- oxidize proteins
- Chlorine & Iodine
- Bacterial cidal
- effective against a variety of organisms
Limitations:
- Work slowly against spores
- inactivated by organic matter
- Noticable taste & odor
Chlorine
- Release hypochlorous acid in solutions
- oxidizes proteins
- water purification - city water & pools
Iodine
oxidizes proteins
skin antisepsis and surgical prep
EX: betadine
Chloroprep Skin antiseptic
Gram positive and Negative
Uses:
- oral rinses
- skin cleanseres
- small quanities
Phenolics
Mechanism:
- Denatures or coagulates proteins
- Hydrophobic–> disrupt cell membranes and loosen organisms from surfaces
Useful for disinfecting surfaces
Limitations:
- More active against Gm +
- little activity against spores
Alcohols
- denature proteins and disrupt membranes
- ethanol & isopropyl alcohol
Mechanism:
dissolves lipids/disrupts membranes
antisepsis on skin
Quaternary Ammonium compounds (quats)
have + charged N
amphipathic molecules
Mechanism:
- dissolve lipids in cell membranes
- effective against bacteria & enveloped viruses
- used in cleaning products
Ethylene oxide
reactive gas
Mechanism: an alkylating agent–> crosslinks proteins and other macromolecules
kills all microorganisms including spores
sterilizes
Chemiclave
sealed chamber for etO sterilization
EtO for 3 hrs.
Flush with inert gas for 8-12 hr
useful for plastics, medical devices, surgical supplies
Chemotherapeutic agent
chemical substance that is used in the body for therapy
Antimicrobial agent
a chemotherapeutic agent used to treat infections caused by microbes
Antibacterial agent
a drug used to treat infections caused by bacteria
Antibiotic
an antimicrobial substance produced by a microorganism that inhibits or kills another microorganism
Natural products
purified from natural sources or from microorganisms
Synthetic
completely made by chemical synthesis
Semi-synthetic
initially purified from a natural source, with subsequent synthetic modification
Antibacterial class
- general type or group of antibacterial agent
- Based on mechanism of action or target
- Usually have similar chemical structure
Antibacterial generation
groups of agents within a class that represent a major improvement over other members of the class
Selective toxicity
kills or inhibits the pathogen, but not the host
Broad spectrum
Active against a wide array of bacteria, including both Gram(+) & Gram(-) organisms
Narrow spectrum
Active against a limited range of organisms
Bactericidial
Kills pathogen
Usually requires 99.9% kill to be –cidal
Bacteriostatic
Inhibits the growth of the pathogen
Relies on host defenses to kill
Directed therapy
Selection of agent based on results of culture and sensitivity testing
Takes 24-48 hours to get results
Granulocytes
- have granules in cytoplasm & lobed nucleus
- *Neutrophils** [polymorphonuclear leukocytes, PMNs] – professional phagocytes; granules contain lysosomal enzymes
- *Basophils** – granules contain physiologically active substances (histamine)
- *Eosinophils** – granules contain toxic substances that defend against parasites
Agranulocytes
– have no granules in cytoplasm & round nucleus
- *Monocytes** – can leave the circulation and enter tissues, where they develop or differentiate into macrophages – which are professional phagocytes
- *Lymphocytes** – include B & T lymphocytes, involved in antibody responses & cellular immune responses
- *NK cells** (natural killer cells) – involved in extracellular killing of virus-infected cells
Lymph
fluid that surrounds cells and tissues
extracellular fluid; interstitial fluid
Lymph vessels
drain lymph from tissues
empties into circulatory system at thoracic duct
lymph nodes
lymphoid organs positioned along the lymph vessels; they filter out foreign material
non-specific resistance
3 characteristics:
Exists in all people, all the time
Active at first (and all subsequent) exposures
Protects against all microbes
Also called innate immunity
Specific resistance
3 characteristics:
Exists only in those previously exposed to a particular parasite
Active at second (and all subsequent) exposures
Protects against only that specific microbe
Also called acquired immunity
Physical barriers
Cells, structures, or forces that cover or line body surfaces, making it difficult for microbes to penetrate
Chemical barriers
Chemical molecules produced by the body that inhibit or prevent microbial growth
Neutraphils
Granulocytes
Reside in blood; recruited to infection site
First-responders in inflammation
Short-lived (~3 day life span)
Tend to die after phagocytosis pus
Macrophages
“big eaters”
Mononuclear cells; derived from monocytes
Reside in certain tissues or wandering
Later responders in inflammation
Longer-lived (months/years life span)
Phagocytose and keep on going
Chemotaxis
Movement in response to a chemical attractant
Chemokines
the chemical attractants that phagocytes respond to, for example:
Short peptides that bacteria release
Molecules that other phagocytes release
Phagocytosis
- *Adherence** – phagocyte binds to specific molecules on microbe’s surface
- *Ingestion** – phagocyte engulfs microbe and takes it inside within a phagosome
- *Fusion of phagosome with lysosome** –lysosomes contain many digestive enzymes
- *Killing & digestion** –can occur within 20 minutes. debris is released outside the phagocyte
Inflammation
A nonspecific response to tissue injury
Wound, infection, burn, chemical insult
Kills microbes, clears debris, heals tissue
Starts quickly (begins within min, occurs within hr)
Neutrophils are the first responders; Macrophages come later
Characteristics of inflammation
Redness – increased blood flow to area
Heat – from warmth of blood
Swelling – from accumulation of fluid
Pain – from injury to local nerves
Inflammation & phagocytosis work together to prevent or contain infection
Acute inflammation
Release of chemical mediators
Capillaries dilate and become leaky
Phagocytes migrate to the site
Phagocytosis
Tissue repair & healing
pyrogen
substance that causes fever; acts on hypothalamus to “increase” the thermostat
Exogenous pyrogens – come from outside the body;
Endogenous pyrogens – come from inside the body
Compliment
marks pathogens for destruction
Stimulates inflammation - with chemokines
Promotes phagocytosis - by opsonization
Opsonin = a molecule that promotes phagocytosis when bound to the surface of a microbe; a “handle” for phagocytosis
Destroys pathogens directly - with membrane attack complexes
