Virulence Factors (Exam 1) Flashcards
What is a nosocomial infection
hospital or health associated place acquired infection
What can be the causes of nosocomial infection
endogenous or exogenous
What is an opportunistic infection
infection caused by a microorganism that does not usually cause a disease in a healthy individual
What is an endogenous source of infection
from person’s own microbiome
What is an exogenous source
outside of the person’s own microbiome
When will symptoms present in a patient with a nosocomial infection
48-72 hours after being admitted
What is virulence
ability of an organism to cause disease
What are virulence factors
products that the organism generates which enable it to survive and cause disease
What factors play into disease outcome
Person or host exposed
and
the microorganism
Is the outcome of exposure to an infectious agent the same for all who have been exposed
no
How does the person or host impact outcome of infection
immune system
How does the microorganism impact infection
number of microbes exposed
virulence of microbes
What are the steps in the infection process
Entry Adherence Gaining Nutrients Multiplying Evading Host Immune
What are the different methods of human to human transmission of organism
vertical
horizontal
What is vertical transmission of organisms
from parent to child, generational
What is horizontal transmission
from human to human
What are methods of vertical transmission
in utero, during delivery, through breast milk, blood
What are methods of horizontal transmission
direct contact
Respiratory
Fomites
How is blood transmitted
vertical or horizontal
What are fomites
intermediate, inanimate object that can transmit an infectious disease/pathogen
What are examples of vector born transmission
mosquitoes: malaria, west nile
Ticks: borrelia: lyme disease
What is zoonosis transmission
an infection transmitted to a human from an infected animal
What are the different methods of zoonosis transfer
direct: eating animal, scratches, bites, fecal
indirect: through an arthropod vector
How does Salmonella, Shigella, and E. coli gain entry
ingestion
How does mycobacterium and legionella gain entry
inhalation
How does clostridium tetani gain entry
trauma
How does staph epidermidis, S. aureus gain entry
needle stick
How does borrelia, ehrlichia, rickettsia gain entrance
arthropod bite
How does neisseria, chlamydia gain entrance
sexual transmission
What are the possible outcomes after being exposed to a pathogen
- clear pathogen, no infection
- asymptomatic
- carrier and pass it on
- develop symptoms
What are acute infection characteristics
sudden onset, short term
What are chronic infection characteristics
long term, slow progression, may last a lifetime
What is the function of pili in colonization
adhesion to cells and tissue
What is the function of adhesins in colonization
tight binding to host cells
If the receptor on host is a sugar, what is the adhesin known as
lectin
What is the role of invasion proteins in colonization
host cellular actin rearrangement
forced phagocytosis of bacteria to get bacteria inside host. Move from one host to another cell
What structure allows specific attachment of cells to other cells
pili
What are the 3 main functions of pili
Movement
Adhering
Conjugation: transfer of DNA
What is a conjugation pilus
allows the transfer of DNA material between cells
hollow in center
What is a capsule
polysaccharide and water structure that surrounds the cell
What bacteria is the exception to having a polysaccharide capsule
Bacillus anthracis
What type of capsule does Bacillus anthracis have
Protein: amino acids
What are the functions of a capsule
protect
nutrients
adherence
prevents dehydration
What allows organisms to cross the blood brain barrier
capsule
What are examples of encapsulated bacteria
Neisseria meningitidis streptococcus pneumonia klebsiella pneumoniae haemophilus influenza b pseudomonas aeruginosa bacillus anthracis
What is a biofilm
community of microorganisms encases within an exopolysaccharide matrix attached to a solid surface or to each other
What makes cells in a biofilm less susceptible to antibiotics
antibiotics cannot easily penetrate the biofilm
cells in the biofilm grow more slowly
WHy are biofilms less susceptible to the immune system
immune system cannot penetrate through the biofilm
What are medical biofilms
dental plaques Urinary catheters contact lenses cystic fibrosis endocarditis otitis media pacemakers
What is a common target within the GI tract for organisms that cause intestinal disease
Peyer patches: mucin layer thinner over M cells
What is the function of M cells
sample the luminal antigens and transport them to the lymphoid tissue below
What are examples of organisms that will invade through M cells
Shigella Salmonella Listeria Yersinia Enteropathogenic E. coli
What are the steps of shigella flexneri invasion
- taken up by M cell
- Escapes from vaccule
- lyses m cell and infects epithelial cell
- replicates in cytosol of new cell
- polymerizes F actin
- propels to new cell
What are direct ways in which a pathogen may cause damage
invade and disrupt cells
produce degradative enzymes and toxins
What are indirect ways in which a pathogen may cause damage
trigger an immune response: host can damage itself
superantigen
What does a superantigen cause
massive immune response resulting in shock and organ failure
How might bacterial metabolism cause damage to host tissue
acids and gases from metabolism can be toxic
What are examples of degradative enzymes that can causes damage to host tissues
streptococcus
pseudomonas
What does streptococcus produce that is harmful to host
hyaluronidase
What does pseudomonas produce that is harmful to host
elastase
What is the effect of hyaluronidase
breaks down the polysaccharide component responsible for binding cells together
What is the effect of elastase
breaks elastin down in the skin and CT
What are exotoxins
toxins produced by the bacteria in extracellular environment
What is an endotoxin
toxin attached to the bacterial cell
Lipopolysaccharide on gram negative bacteria
How will incubation times differ between endo and exotoxins
exotoxins have a shorter incubation time than endotoxins
How can exotoxins be designated
according to the location or tissue affected
What is a neurotoxin
toxin that interferes with neural transmission
What is an example of a neurotoxin
clostridium tetani: tetanus toxin
What are enterotoxins
toxin that affects the intestines
What is an example of an enterotoxin
vibrio cholerae: cholera toxin
What are cytotoxins
toxins that destroy host cells
What is an example of cytotoxins
clostridium perfringens: phospholipase C
What are hemolysins
toxins that lyse RBC
What is an example of hemolysin
strep pyogenes
What are the different types of hemolysis
alpha
beta
gamma
What occurs in beta hemolysis
complete breakdown of RBC
What occurs in alpha hemolysis
partial breakdown of RBC, green halo
What occurs in gamma hemolysis
cells grow, but do not lyse
What are different toxins that can disrupt the cell membrane leading to cell lysis
phospholipase and ore-formin exotoxin
What is an example of an exotoxin with two subunits
diphtheria toxin
What is the A subunit of the toxin
active portion
What is the B subunit of the toxin
receptor binding and transports the toxin into the cell
What is the mode of action of the diptheria toxin
ADP-ribosyl transferase
What does the ADP ribosyl transferase do
moves ADP to EF2 to inactivate the elongation factor and prevents host protein synthesis
What other organism shares the similar mode of action as diptheria toxin
P. aeruginosa
What is the mechanism of the cholera toxin
binds to Gs regulatory protein to activate adenylate cyclase to produce cAMP
What does increased cAMP lead to
cell pumps Cl- and water into the intestinal lumen causing diarrhea
What channel will the cholera toxin act on
CFTR cholride channel
What botulinum toxins are pathogenic in humans
A, B, and E
What is the mechanism of the botulism toxin
binds to the presynaptic terminal of a neuron to prevent release of ACh
What does botulism toxin result in
flaccid paralysis and skeletal muscle weakness
What is the mechanism of the tetanus toxin
binds to the presynaptic terminal of an inhibitory neuron preventing release of GABA
What does tetanus toxin result in
spastic paralysis
What will occur in response to a superantigen
cross linking of T cell receptors and MHC II molecules
What is stimulated by a superantigen
cytokine production and inflammatory response; TSS and death
What type of organism is more likely to elicit a superantigen response
gram positive organisms
What is the name of the superantigen for staphylococcus aureaus
TSST1
What is the name of the superantigen for Stap aureus
enterotoxins
What is the superantigen for stretococcus pyogenes
streptococcal pyrogenic exotoxin A
What type of organisms are endotoxins found in
gram negative
What may happen as a result of a large amount of gram negative bacteria being killed
large amount of endotoxin is released
septic shock
What type of organisms are responsible for toxic and septic shock
toxic: gram +
septic: gram -
What is the mechanism of LPS
binds to CD14 and TLR4 on macrophages to induce Il-1 and TNF alpha production
activates complement
stimulates B cells to produce antibodies
What cytokines will be released in response to LPS
TNF alpha
IL 1
What are siderophores
iron scavenging molecules secreted by bacteria to acquire iron from the environement and bring it back to the bacterial cell being ingested
What do siderophores bind to
Fe3+
What are examples of siderophores
lactoferrin
transferrin
ferritin
hemin
What is a type 3 secretion system
injects toxic proteins directly into host cell via syringe like apparatus
What are examples of type 3 secretion
salmonella
pseudomonas
yersinia
ecoli
What are the benefits of type 3 secretion systems
only produced when needed
doesn’t dilute toxins in environement
protects toxins from possible antibodies
What are examples of organisms that evade host defenses by preventing phagocytosis
S pneumonia
H inflenzae
K pneumonia
ALL VIA CAPSULE
S pyogenes: M protein
What are examples of organisms that evade host defenses by killing WBC
Staph and strepcoccus
What do staph and strep produce to kill WBC
leukocidins
What are examples of organisms that will produce enzymes to evade host defenses
staph aureas
streptococcus pneumoniae
strep pyogenes
What enzyme does Staph aureas produce
coagulase
What enzyme does streptoccoccus penumoniae produce
coagulase: coagulates fibrinogen forming abscesses
What enzyme does streptococcus penumoniae produce
IgA protease
What enzyme does streptococcus pyogenes produce
C5a protease
What is antigenic variation
change structure of surface antigens therefore antibodies do not recognize bacteria
How do organisms that grow intracellular evade the host defense
prevent phagosome lysosome fusion
escape phagosome
break down peroxide
How are staph and strep differentiated
catalase test
strep negative
staph positive
What is a coagulase test used to differentiate
between staph aureaus and other staph
Where are genes that code for virulence factors located
chromosome
plasmids
bacteriophages
transposons
What is a pathogenicity island
genes for toxin and secretory apparatus close together on the chromosome so they are produced efficiently
Where will transposons move genes
from plasmid to chromosome or vice versa or from one site on chrom to another
What is quorum sensing
bacterial interaction in which certain genes are turned on only when there are enough other bacteria in the area to make the response beneficial
What type of chemical is used in quorum sensing
autoinducer
What is an autoinducer
once the chemical reaches a high enough density it will bind to the promotor regions and turn on transcription followed by translation
What are the steps in quorum sensing
bacteria produce and secrete chemical molecules
concentration of molecules increases with increasing bacterial density
when critical concentration of molecule is reached, bacteria alter gene expression
What do chemical autoinducers mimic
human hormones
