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109 Cards in this Set

  • Front
  • Back
definition: PATHOGEN
infectious agent that has the ABILITY to cause disease in a particular host
strict pathogen
always pathogenic
opportunistic pathogen
pathogenic in immunocompromised host or when introduced to unprotected site
virulence
degree of pathogenicity
virulence factor+
property that enhances ability of microorganism to cause disease
carriage
host colonized with a pathogen, but no overt symptoms of disease

can still be infectious

can be transient or long-term
latent
infectious agent present, not growing, can reactivate
commensal
part of normal flora
infectious dose
# of organisms required to cause disease
Koch's First Postulate
organism must always be found in diseased animals, but not in healthy ones
Koch's Second Postulate
organism must be isolated from diseased animals and grown in pure culture away from the animal
Koch's Third Postulate
organism isolated in pure culture must initiate and reproduce the disease when reinoculate into susceptible animals
Koch's Fouth Postulate
organism should be reisolated from experimentally infected animals
Modified Koch's Postulates for molecular biology (1)
1. gene must be identified from virulent microorganism
Modified Koch's Postulates for molecular biology (2)
2. gene must be inactivated by methods which do not allow reversion in original strain, constructing an isogenic strain that is negative for that gene
Modifed Koch's postulates for molecular biology (3)
3. strain w/ inactivated gene must be shown to be avirulent or to have measurably reduced virulence
Modified Koch's postulates for molecular biology (4)
reintroduction of the WT gene into the iosgenic negative strain should lead to a return of original virulence
5 steps of typical infectious cycle
entry of the pathogen
colonization
avoidance of host defenses
damage to the host
exit
4 reservoirs of infection
environment
infected persons
infected animals
self
5 routes of transmission
airborne/respiratory
oral-fecal
direct inoculation
direct contact
congenital
host defenses in upper respiratory tract (URT)
mucous lining
ciliated cells on lining
secretory immune system, eg: IgA
alveolar Mphages
normal microbiota
4 examples of airborne pathogens
Legionella
N. meningitis
M. tuberculosis
S. pyogenes
host defenses against oral-fecal transmission
intact intestinal mucosal epithelium
secretory immune system & IgA
bile, acid, digestive enzymes
peristalsis
normal microbiota
4 oral-fecal transmitted bacteria
V. cholerae
E. coli
Salmonella
Shigella
host defenses against direct inoculation
intact skin barrier
examples of direct inoculation
most staph infections
deep wound infections (tetanus, gangrene)
disease spread by insect vectors
disease spread by transfusion
man zoonotic infections
4 examples of diseases spread by insects
malaria
plague
typhus
arboviral diseases
host defenses against direct contact transmission
intact epithelial surface
mucosal secretory immune system
examples of diseases transmitted by direct contact
skin diseases, eg: impetigo, athlete's foot

mucosal infections: STDs, conjunctivitis, trachoma, herpes
host defenses against congenital transmission
placenta
examples of transplacentally transmitted diseases
congenital rubella
congenital syphilis
examples of diseases transmitted at birth
any STD
herpes
group B strep
colonization
attachment of a microorganism to host tissues and its multiplication on these surfaces
adhesins
attachments factors on invading organism
receptors
factors on host cells recognized and bound by adnesins
2 protein types used in colonization
adhesins

receptors
5 examples of bacterial adhesins
E. coli Pap pili
Streptococcal F protein
Mycoplasma pneumoniae membrane protein
Neisseria pili
Vibrio cholerae
3 factors other than adhesins/receptors that affect attachment
motility
mucinases
IgA1 proteases
during colonization, bacteria can attach to what 3 things
inanimate objects (biofilms)
other microbes
other microbe communities
biofilms
cooperative behavior of a bacterial population wherein the bacteria adhere to one another as well as a surface
function of biofilm
facilitates colonization

prevents washing away
communities of bacteria morphologically and physiologically differentiated from free-living bacteria
biofilms
can biofilms be composed of multiple species?
yes
quorum-sensing
involves production and sensing of small molecules called bacterial pheronomes

facilitates cell-cell communication
prosthetic valve

bacteria that form biofilms
disease that results
S. epidermis
S. sanguis

--> endocarditis
artificial heart

bacteria that form biofilms
disease that results
P. aeruginosa
S. aureus
S. epidermis

--> septicemia
IV catheters

bacteria that form biofilms
disease that results
Staphylococcus epidermidis
Staphylococcus aureus

--> septicemia, endocarditis
urinary catheters

bacteria that form biofilms
disease that results
P. aeruginosa
proteus mirabilis
E. coli
E. faecalis

--> bacteriuria
contact lensesq
P. aeurinosa
S. epidermidis

--> keratinitis
type of biofilm that causes periodontal disease
usually mixed communities
species that forms biofilm in CF lung
P. aeruginosa
species that forms biofilms in environment, but is planktonic in gut
V. cholerae
bacterial disease
result of bacterial invasion
& sometimes host response to invasion --> damage to host
3 mechanisms used by pathogens that cause disease
direct damage by toxins and enzymes

penetration and destruction of host cells

indirect damage by immunopathologic reactions
toxin
molecule produced by bacterium that is

RELEASED

to affect host cells at a distance
two means of toxin release
shed

actively secreted
exotoxin
protein released from bacterial cell that is toxic for target cells or animals
endotoxin
LPS
cell wall components that mediate toxicity
petidoglycan (G+ and G-)

techoic and lipotechoic acid (G+)
what type of bacteria is LPS never found in?
G+
effects of LPS
stimulation of Mphages, B-cells and other cells to multiply and release cytokines, inflammatory molecules
LPS always lacking O-antigen

name
2 bacteria type
LOS

Neisseria
Haemophilus
LPS sometimes lacking O-Ag

name
bacteria
rough LPS

Salmonella
LPS shed by bacterial cells forms a complex with WHAT, WHERE?
with an LPS-binding protein

in serum
what does LPS-protein complex bind on WBCs?
CD14 receptors
what does LPS bind on endothelial cells (besides CD14R)
TLR4
proinflammatory cytokines triggered by endotoxins
IL-1, IL-6, TNF-a, IL-12
3 inflammatory mediators triggered by endotoxins
PGs
LTs
kinins
do endotoxins initiate adaptive immune response?
yes
at LOW concentrations, endotoxins are _____
immunostimulants, eliciting protective responses
4 effects of LOW concentration endotoxin
fever

increased phagocytic ability

increased Ab synthesis

vasodilation
HIGH concentrations of endotoxin lead to...
hypotension and shock
shock
widespread hypoperfusion of tissues

due to reduction in blood volume or cardiac output --> inadequate circulating volume
3 types of shock
endotoxic
cardiogenic
hypovolemic
3 types of exotoxins
neurotoxins
enterotoxins
cytotoxins
3 types of endotoxins by morphology
AB subunit toxins

cytolysins

superAg toxins
AB subunit exotoxin mechanism of action
ADP-ribosylation

A subunit is ADP-ribosyl transferase

transfers ADP-ribose from NAD to some host protein, resulting in host protein inactivation
3 examplse of ADP-ribosylation
diphtheria toxin

cholera toxin

tetanus and botulinism toxin
phospholipases
hydrolyze membrane phospholipids and destabilize cell membranes

e.g.: Clostridium perfringens alpha-toxin
superAg toxins
protein toxins that exert their effect by forming a bridge btw MHC class II of Mphages and V-beta portion of TCR
do superAg toxins need to be processed by APCs to be effective?
NO
2 things superAgs stimulate
T-cells
B-cells
how are superAgs different from true mitogens
true mitogens stimulate ALL T-cells to proliferate

SuperAg's only activate T cells expressing certain TCR V-beta proteins
how are superAgs different from normal Ags?
normal Ags activate a single or very limited subset of lymphocytes expressing TCRS specific for that Ag

SuperAg's activate all T cells expressing certain TCR V-beta proteins
extracellular enzymes, aka:
spreading factors
4 types of spreading factors
collagenases

proteases

hyaluronidase

DNase
chemical nature of endotxins vs. exotoxins
endotoxins - lipopolysaccharides

exotoxins - proteins
which are more strongly neutralized by Ab's, endo- or exotoxins?
exotoxins are more strongly neutralized by Ab's
which are stable to boiling, endotoxins or exotoxins?
endotoxins are stable to boiling
which stimulates B cells, endotoxins or SuperAg's?
both
which stimulates T cells, endotoxins or superAg's?
superAg's
which bridges MHC II and TCRs, endotoxins or superAg's?
superAg's
which stimulates IL-1 and TNFa, endotoxins or superAg's?
both endotoxins and superantigens
which stimulates coagulation cascade, endotoxins or superAg's?
endotoxins only
which stimulates fibrin cascade, endotoxins or superAg's?
endotoxins only
non-professional phagocytes
host cells that are not normally phagocytic but can be induced to take up a bacterial pathogen by PATHOGEN-SPECIFIED receptor-mediated endocytosis
bacterial mechanisms to avoid phagocytic killing
prevention of maturation of phagolysosome

alteration of phagosome

escape from phagosome
bacteria that survive w/in professional phagocytes trigger their own uptake into the cells by binding to which phagocyte surface receptors?
C3b

fibronectin receptors
proteins that bind to host cell receptors and induce uptake into non-professional phagocytes
invasins
zipper mechanism of host cell invasion
invasin binds to host cell receptor and "zips" the host cell membrane around the bacterium by sequential binding
trigger mechanism of host cell invasion
bacterial type III secretion system injects one or more proteins into host cell

triggers membrane ruffling, including actin polymerization and cytoskeletal rearrangements
coiling phagocytosis mechanism of host cell invasion
characteristic of L. penumophila

occuras spontaneously with Legionella via interaction between bacterial porin and complement

coils form around organism and phagosome " sinks" into cell
what 2 things does zipper mechanism require
host cell actin network

host cell signaling via tyrosine kinase
2 examples of zipper mechanism
Yersinia species INVASIN binds beta-1 integrin

Listeria monocytogenes INTERNALIN binds E-cadherin
In zipper mechanism, bacterium is taken up into a ____ or ____
membrane-bound vacuole or phagosome
4 things trigger mechanism requires
energy expenditure by host cell

actin and microfilament network

host cell signaling cascades

metabolically active bacteria
host cell entry mechanism that does not disrupt integrity of host cell
trigger mechanism
2 examples of bacteria that use trigger mechanism
Salmonella typhimurium SipB-D proteins

Shigella dysenteriae IpaB-D proteins
3 types of indirect damage by immunopathologic reactions
induction of cross-reacting antibodies, e.g.: S. pyogenes and heart tissue

dposition of immune complexes in tissue, e.g.: glomerulonephritis (Type III reaction)

Delayed hypersensitivity and granuloma formation e.g.: TB (type IV reaction)