Pathogenesis and the Disease State
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Classical Signs of Disease and Inflammation
- rubor (red flushing)
- tumore (swelling)
- calor (heat)
- dolor (pain)
- Functio Laesa (loss of function)
fluid and immune comp rush in--> swelling
- classic mechanisms for two reason:
- --> for viral infections: you don't feel like doing anything; limiting ability to host cells--> slow doown reproduction of pathogens
- --> pathogens stay 2-2.5 degrees in normal body temperature; above, bacteria can't get in
Most bacteria have __ signs of disease and inflammation
Classical Signs of disease and inflammation: who defined them?
1 to 4 as defined by Aulus Cornelius Celsus in De Medicina
5 as defined by Galen of Pergamon
Signs are __. Symptoms are __. Syndrome is __.
subjective changes (have to deal with individually)
Components of the diseased state
signs: objective changes in the normal physiology of an organism (eg: fever, rash, that are readily observable)
symptoms: subjective changes in the physiology of an organism, eg: loss of weight, loss of appetite, fatigue
sydrome: the characteristic manifestation of a specific set of signs and symptoms
What are the stages of progression of an infection?
the period during which the organism colonizes a healthy host. Towards the end of the period, the illness slowly becomes apparent
get exposed and start to feel a little bit off
the first symptoms of the disease appear. The organism has effectively colonized the organism and is rapidly reproducing. This is a stage at where the disease is highly communicable
you know; you're effectively colonized and organism is reproducing
the characteristic symptoms peak
characteristic symptoms peak
the first signs of the regression of the disease as well as the loss of communicability
feeling slightly better
the organism returns to full health
shortest of the lot
Infection/ Disease periods
latent, comunicability, and illness period
that part of the incubation stage that spans between the initial infection and the first apparent sign of the illness
the time span between the first signs of the illness and the first signs of the regression of the disease
90% of the time that you're sick
Illness period (acute phase)
the period of time between the end of the latent period and the beginning of the convalescent stage
Latent period to the convalescent stage
Avoidance of the Immune System
some species of bacteria can bind hte non functional end of an antibody
Neisseria sp. bind the proteins of the complement cascade, thus preventing their own lysis
Salmonella sp. are able to live within phagocytic white blood cells
the pili of Neisseria sp. inhibit the binding of phagocytic white cells
Avoidance of the Immune System:
__ of antigens binds __.
Bind at the __ end of the antibody
Can live in __ and avoid __.
fragment antigen binding (Fab fragment)
Neisseria have __ and __.
- weird pilis
- inhibit WBC by binding
an organism that is capable of causing disease
the qualitative description of an organism's ability to invade a host and cause disease
the quantitative description of an organism's ability to invade a host and case disease
the ability of a microorganism to invade a host cell or tissue and be able to multiply on or within them, i.e. the ability to establish an infection
Explain the disease process
attachment can lead to three things
--> non-invasive disease: localized symptoms; if a toxin is present, systemic symptoms
--> local invasive disease: localized symptoms
--> invasive disease: systemic symptoms
All can lead to possible sequela
a pathological condition resulting from a disease, injury,therapy, or other trauma.
What do pathogens have that help them adhere?
adhesin: surface molecules on a pathogen, called adhesins or ligands, bind specifically to complementary surface receptors on cells of certain host tissues
What is the second step after attachment?
- noninvasive, local invasive, or invasive
Penetration is mediated by __. Which ones?
- - hyaluronidase (digests hyaluronic acid)
- - coagulase (promotes fibrin clotting)
- - streptokinase (dissolves fibrin clots)
bacterial enzyme that digests hyaluronic acid
- - Glucosaminoglycan
- ---> Tissue structure
- ---> wound healing
- promotes spread of bacteria into tissues
- penetrates through the connective tissue layer
- secreted by
- - streptococcus sp.
- - staphycoccus sp.
- - clostridium sp
bacterial enzyme that promotes fibrin clotting
- promotes localizing bacteria
- - lack of spread/ penetration
- damage to wall of BV--> forms clot to make damage less noticeable and shields it from immune system
- sets up infection under clot
Coagulase is secreted by __.
Common pathologies: __
uncommon pathologies? __
- staphylococcus sp.
- Yersinia sp.
pimples, boils, abscess
Uncommon pathologies: variable myonecrotic syndromes
- Bacterial enzyme that dissolves fibrin clots
- promotes spreading of infection
- secreted by: Streptococcus sp.
localized--> gains critical mass--> breaks out of clot--> released anywhere within short distance of clot
ID50--> infectious dose (of organisms) for 50% of the test population (Infectious Dose for 50%)
LD50: lethal dose (of a toxin) for 50% of the test population (Lethal Dose for 50%)
Exotoxins and Endotoxins
gram positive have exotoxins
gram negative bacteria have endotoxins
- Source: __
- Relation to Microbe: __
- Chemistry: __
- Source: gram -
- relation: outer membrane (cell wall)
- chemistry: lipid A of LPS
Chemistry: Lipid A (of LPS)
-relation to microbe
- neutralized by antitoxin (antibody)
- Gram negative sp
- Relation to microbe: outer membrane (cell wall)
- Lipid A (of LPS)
- Not neutralized by antitoxin
- Relatively Large
- the mechanism of action is __
- the toxins are __
relation to microbe:
neutralized by antitoxin:
- highly specific
- species specific
- source ??
- relation: secreted by living cell
- chemistry: protein
- fever: no
- neutralized by antitoxin: yes
- LD50: small
Virulence of Bacterial toxins
- Typical endotoxin
- Typical exotoxin
endo: LD50 in mice= 200 micrograms
exo: LD50 in mice= 2 x 10-5 micrograms
Many __ genes are actually __ expressed in a __.
- viral genes
- lysogenized bacterial cell
Bacteriums and their diseases:
- __: diphtheria
- __: strep throat
- __: botulism
- __: cholera
What is the first rule of any good infection?
you gotta get in. If it can't get in, it can't cause disease
Virulence is equivalent to __.
the effectiveness of getting in
Invasiveness must ask the questions?
can the organism get in? If so, disease or no?
What is the first rule of thumb for the invasion process?
got to adhere (associate)
does this by adhesins: work with proteoglycan receptors on the cell
Endotoxins are released when __.
cells die in gram negative bacteria
Exotoxins are __. Secreted while __.
Two components of exotoxins.
bacteria is alive
one to bind and one to go in (shuts down protein synthesis)
proteins sitting on genes
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