Pathogens Flashcards
Which one is the more virulent ?
S. pneumonia or Salmonella enterica serovar Typhimurium
S. pneumonia
Virulence is determined by 2 principal features
1- invasiveness
2- Toxigenicity
What is a pathogen?
Microorganisms capable of causing disease (damage to the host)
Does all strain of a specie have the same virulence properties?
No
Not all strains of a specie have the same ability to cause disease
True or false:
A pathogen is usually identified by the set of chromosomes that are carried and expressed?
False
True or false:
A pathogen is usually identified by the set of virulence genes that are carried and expressed?
true
Steps of infection
1- exposure
2- attachment-adhesion
3- invasion of tissues
4- Grow
Describe virulence:
Measure of the ability to cause damage to the host, depends on a number of virulence factors
invasiveness tools:
Adhesins capsules enzymes that destroy host tissues invasins T3SS T4SS
Are capsules only produces by bacterial pathogens?
No
The capsule is not only a virulence factor (non pathogenic microorganisms may have a capsule too)
What is invasion?
Destruction of host tissues
Gas gangrene : 3 extracellular enzymes
1- lecithinase to lyse host cell
2- Collagenase
and 3- hyaluronidase to destroy ECM
(both collagenase and hyaluronidase destroy ECM)
Hemolysin : some are cytolysin (do what)
and some are enzymes (lechithinase, phospholipase) (do what)
Cytolysin : pore forming
Lecithinase : degrade lecithin ( phosphatidylcholine) in cell membrane - cause the lysis of red blood cells and destroys tissues cell.
What is the major virulence factor of intracellular pathogens?
Invasins
T3ss also called…
injectosome
TXSS have a needle like structure
T3SS
Pneumonia : infection or intoxication
infection
Meningitis: infection or intoxication
infection
syphilis: infection or intoxication
infection
food poisonin: infection or intoxication
intoxication
AB toxin: Exotoxin or endotoxin
Exotoxin
extracellular enzymes (hyaluronidase, collagenase).. : Exotoxin or endotoxin
Exotoxin
A subunit?
Enzymatic subunit
B subunit?
Binding-cell entry
This subunit modifies a target inside the host cell leading to damage to the host
A
Botulinum toxin : Exotoxin or endotoxin
exotoxin
Cholera toxin: Exotoxin or endotoxin
exotoxin
What is botox used for? (3)
- reduces wrinkles-frown
- muscle spasms
- Hyperhydrosis (excessive sweating)
AB toxin : Botulinum toxin
This neurotoxin blocks…
acetylcholine release in neurmuscular junction
= Flaccid paralysis
AB5 toxins : Cholera toxin
Subunit A : ??
Adenylate cyclase, produce cAMP
Endotoxin describe it (at least 3 characteristics)
- Lipid A of LPS from Gram - bacterial pathogens. Released during multiplication or lysis of bacterial cells.
- Heat stable
- Weakly immunogenic (no antibody are produced against LPS).
- Very effective activator of the immune system, produce general systemic effect: fever (pyrogenic), shock, weakness, inflammation, diarrhea, SEPTIC SHOCK
- important cause of symptoms in all Gram-bacterial infections (Salmonella, E.coli).
Extremely potent, amongst the most lethal substances known
Exotoxins
How do you call a toxin that is inactivated by formaldehyde or heat
toxoid
True or false
Endotoxins cannot be activated by heat or formaldehyde and cannot be converted to a toxoid : no vaccine against endotoxins.
True
True or false
Exotoxins do not produce fever in host
true
True or false
Endotoxins do not produce fever in host
false
True or false
Mode of action of exotoxin: fever diarrhea vomiting
false
True or false
Mode of action of endotoxin : fever diarrhea vomiting
true
True or false
Exotoxin are highly immunogenic
true
True or false
Endotoxin are weakly toxic, rarely fatal
true
True or false
Exotoxins are heat-labile
true
True or false
Endotoxin are heat-labile
false
Innate defense are specific or not
non-specific
Adaptive defense are specific or not
yes specific.
based on antigens
Normal microbiome secrete…
bacteriocin
what are some antimicrobial substances: (4)
1- Fatty acids
2- lysozymes
3- antimicrobial peptides (AMPs)
4- antibodies (if the host is immune)
innate defense of the skin?
Thick layer of dead cells
Innate defense of the mucous membrane?
mucous
What are phagocytes?
Cells that take up and digest pathogens
inflamation is due to innate system or specific system against a host
innate system
What is the complement system?
set of proteins that creates pore in the pathogen membrane and induce lysis
(part of the second line of defenses)
Name all the proteins of the complement system
C1 C2 C3 C4 C5 C6 C7 C8 C9
What activate the classical pathway
antibodies
what activate the alternative pathway
microbial cell wall components (polysaccharides,lipopolysaccharides)
What happen when the complement is activated?
formation of a membrane attack complex (MAC, made of proteins C5b6789)
what happen when MAC is formed?
lysis of some Gram -, no effect on gram +
What is serum sensitivity?
test sensitivity to complement by exposing pathogens to serum (blood without RBC)
Name 2 cells made from Monocytes
Dendritic cell
Macrophage
Name 3 White blood cells
1- Monocyte
2- Granulocyte
3- Lymphocyte
What are the 4 steps of phagocytosis
1- Attachment of the organism to the membrane of the phagocyte
2- Ingestion : the organism become enclosed in a phagosome
3- A) Granules (endosomes, lysosomes) containing hydrolytic enzymes fuse with the phagosome, formation of the phagolysosomes.
B) Oxidative burst : production of reactive oxygen species ( ROS)
4. Killing and digestion of the microorganism
Phagocytosis is carried primarily by 2 types of cells
Neutrophils (WBC) and macrophages (WBC)
Characteristics of Inflammation, name a few
- Redness
- heat
- swelling
- pain
What is the function of inflammation
bring immune cells, antibodies, complement subunits
What does IL1 do
1- acts on the thermoregulatoy center of the brain
2- activates phagocytes and other cells of the immune system
3- make inflammation happen
Name some innate defenses
- complement
- antimicrobial proteins
- phagocytes (neutrophils, macrophages)
- Inflammation
leucocidin purpose
1kill white blood cell (leucocyte)
-pore forming toxin
extracellular enzyme to invade?
collagenase
purpose of T3SS
- insert protein into the host
- invasiveness
- take control of the host cell
whats in a lyzozome
- hydrolytic enzymes
- antimicrobial peptides
example of phagocyte
- macrophages
- neutrophiles
Mast cells are involved in
inflammation
What are the proteins of the complement that forms the MAC complex
-C123456789
-c1t o c4 are important for activation of the complement
C5 to C9 forms the MAC complex
2 ways to activate the complement
1- alternative pathway
LPS or surface proteins
2- classical pathway
by antibodies
Phagocytosis steps (4)
1- attachment 2- ingestion 3- formation of the phagolysosome Oxidative burst: ROS production 4- Killing and digestion of the microorganism
Set of proteins of the innate system
complements
Macrophage secretes
cytokine (hormone, signaling molecule) : interleukin-1
Mast cells senses
pathogens
Il-1 causes … to the blood vessel
vasodilatation
what is pyogenic
fever
What acts on the thermoregulatory center of the brain
Il-1
Innate defenses (4)
1- complement
2- antimicrobial proteins
3- phagocytes (neutrophils, macrophages)
4- Inflammation (and fever)
Adaptive defenses What cells (3)
1- B cells
2- T cells
3- antigen presenting cells (APCs : macrophage, dendritic cells)
Adaptive defense
3 characteristics
1- Specificity
2- Memory
3- Tolerance
T cells and B cells recognize billions of antigens
What concept?
Specificity
Making copies
What concept?
Memory
immune cells recognize and react with individual molecules(antigens) via direct molecular interactions
what concept?
Specificity
The immune response to a specific antigen is faster and stronger upon subsequent exposure because the initial antigen exposure induced growth and division of antigen-reactive cells, resulting in multiple copies of antigen-reactive cells.
What concept?
Memory
2 types of T cells
T helper cells
Cytotoxic T cells
MHC II expressed by (2)
APCs
B cells
MHC 1 expressed by which cells?
All cells
MHC1 recognized by
cytotoxic T cells
MHCII recognized by
helper T cells
macrophage has which MCH
MHCI and MHCII
APCs present antigen to T cells
Activated T cell produce
Il2
APCs include (3)
- macrophages
- dendritic cells
- B cells
Most important APCs for the process of presenting antigens to helper T cells (2)
- macrophages
- dendritic cells
Helper t cells activated do 2 things
clone (memory)
effector (join the fight)
Cytokine secreted by
T H cell
Perforin and granzyme are released by
T C cells
MHC 1 is related to which cell
Cytotoxic T cells
Activation of macrophages
When Th cell is activated,
it can activates macrophage by producing …
TNF-alpha
What are called activated macrophages by TNF-alpha?
Angry killer cells
picked up by phagocytosis
loaded by MHC..
MCH2
If the antigen is present in the cytoplasm of the host cell, it can be loaded by MHC..
MHC1
what is Fab
Antigen binding sites that are highly variable
What does the Fc (constant region) activates?
Complement (classical pathway)
B cells are phagocytic
display antobodies on its surface by MHC..
MHC 2
processed on a phagosome MHC…
MHC2
B cell multiplies and differentiates into (2)
Plasma cells
memory cells
Activated T cell bind to the antigens
Helper T cell secretes
Il-4
clue for the b cell to get activated
What is a clue for the b cell to get activated ?
Il-4
When B cell is activated what does it do
makes clones of himself
clones= plasma cell or memory cell
Plasma cell (short lifetime) secretes
antibodies
A molecule that enhances phagocytosis by marking an antigen for an immune response is known as
Opsonin
Antibody binds to
toxin
What are hemolysins
some are enzyme (lecithinase, phospholipase)
some are cytolysin (pore-forming)
Capsule is an essential virulence factor for 2 bacterial pathogens
Streptococcus pneumoniae
Haemophilus influenzae
Lecithinase degrades lecithin(phosphatidylcholine)
cause the lysis of
red blood cells
and destroys tissue cells
Leucocidin causes lysis of
leucocytes (white blood cells)
Proteases degrade
complement proteins and or antibodies
Which type of secretion system forms a channel through the bacterial cytoplasmic membrane, the periplasm, the outer membrane, and the host cell membrane ?
T3SS
___toxins are secreted into the surrounding as the bacterial pathogen grows
Exotoxin
__toxins are part of the bacterial pathogen
Endotoxin
I am among the most lethal substance known
Exotoxin
High cAMP makes a change in the cell and it stops picking up…
Sodium
Weakly immunogenic, Exo or Endo?
Endotoxins
Vaccines are against Exo or Endo?
Exotoxins
inactivated toxin is aka
toxoids
AMPs make ____ pores in the bacterial membrane
Pores
What is inflammation?
general nonspecific response of the innate system to toxins, pathogens and tissue damage
Complement system complement the action of
antibodies
What is the precursor of T and B cells
Lymphoid precursor
Name 3 WBC
Monocytes
granulocytes
lymphocytes
Name 2 T cells
T helper cells
cytotoxic T cells
