Pathogenesis Of Microbes Flashcards
Infection:
____________ of an infectious agent within the body.
Multiplication
Multiplication of the bacteria that are part of normal flora of gastrointestinal tract, skin, etc, is generally considered an infection.
T/F
F
Not
On the other hand, multiplication of pathogenic bacteria (e.g. Salmonella species), even if the person is _______, is deemed an infection.
T/F
asymptomatic
T
Pathogenicity:
The ability of an infectious agent to __________
cause disease.
Virulence:
The ______ of an agent to _______
quantitative ability
cause disease.
Virulent agents cause disease when introduced into the host in (small or large ?) numbers.
Small
Virulence involves _________ and _________
invasiveness and toxigenicity.
Toxigenicity:
The ability of a microorganism to ______________
produce a toxin that
contributes to the development of disease.
Invasion:
The process whereby bacteria, parasites, fungi and viruses ———————
enter the host cells or tissues and spread in the body.
Pathogen is A microorganism capable of causing disease.
T/F
T
Non-pathogen is A microorganism that does not cause disease. It may be part of the normal flora.
T/F
T
Opportunistic pathogen:
An agent capable of causing disease only when _______________
An agent capable of causing disease only when spread from the site with __________________ to the _________
the host ́s resistance is impaired (e.g. the patient is immunocompromised).
normal bacterial microflora
sterile tissue or organ.
The pathogenesis of bacterial infection includes the _____ of the infectious process and the mechanisms leading to the development of signs and symptoms of bacterial disease.
The outcome of the interaction between bacteria and host is determined by characteristics that favour establishment of the bacteria within the host and their ability to damage the host as they are opposed by host defense mechanisms.
initiation
Oubreak - ______
Epidemic - _______
Pandemic – _________
local
regional/national
widespread (international)
Most bacteria do not produce disease but ____________________ that ensures the survival, growth, and propagation of both the bacteria and the host.
achieve a balance with the host
Most bacteria produce disease
T/F
F
Sometimes bacteria that are clearly pathogens (e.g. Salmonella typhi) are present, but infection remains ____ or ______ and the host is a “ ______ “ of the bacteria.
latent
subclinical
carrier
In 1884, Robert Koch proposed a series of postulates in his treatise on ______ as _______
Mycobacterium tuberculosis and tuberculosis.
Koch ́s postulates are summarized as follows:
The microorganism should be _______of the disease in question, and its distribution in the body should be in accordancce with the _______ observed.
The microorganism should be grown in ______________ for several ______.
When such a pure culture is __________, the ________ must result.
The microorganism must again be ___________
found in all cases ; lesions
pure culture in vitro;23
inoculated into susceptible animal species; typical disease
isolated from the lesions of such experimentally produced disease.
Koch ́s postulates remain a mainstay of microbiology.
T/F
T
However, since the late 19th century, many microorganisms that do not meet the criteria of the postulates have been shown to cause disease. For example, Treponema pallidum (____) and Mycobacerium leprae (____) cannot be ______, but there are _________
syphilis; leprosy
grown in vitro
animal models of infection with these agents.
In another example, Neisseria gonorrhoeae (gonorrhea), there is no __________ even though the bacteria can readily be ________
animal model of infection
cultivated in vitro.
The __________ should be considered when an organism is being investigated as the possible cause of a disease.
host ́s immune responses
Analysis of infection and disease through the application of principles such as Koch ́s postulates leads to classification of bacteria as ________ or _________
pathogenic or non- pathogenic.
Examples of pathogenic bacterias include ______ (tuberculosis) and ___________ (plague).
Mycobacterium tuberculosis
Yersinia pestis
Other species are commonly part of the normal flora of humans (and animals) but can also frequently cause disease. For example, Escherichia coli is part of the gastrointestinal flora of normal humans, but it is also a comon cause of __________ infection, _______, and other diseases.
urinary tract
Traveller’s diarrhea
The infectious process
Infection indicates _______ of microorganisms.
Prior to that, bacteria (in case of bacterial infection) must ______ and ______ within the host.
The most frequent portals of entry are the _______,_______, and ________ tracts. Abnormal areas of ________ and ———- (e.g. cuts, burns) are also frequent sites of entry.
multiplication
enter and establish themselves
respiratory (mouth and nose), gastrointestinal, and urogenital
mucous membranes and skin
Nosocomial- originating in the ______
Hospital
Gist defenses
Gut : ______,______
respiratory tract: ______,_______,_______
urogenital tract; _______
peristalsis , defecation
ciliary action ,coughing , sneezing
urination
Connective tissue destrction Helps bacterial dissemination
T/F
T
Connective tissue destrction by :
________
________
collagenase
hyaluronidase
Extracellular pathogens are resistant to extra-cellular killing
T/F
T
Extracellular pathogens are killed on _________
phagocytosis
Extracellular pathogens resist killing by avoiding ________
internalization
Toxins produced by bacteria are generally classified into two groups:
______
________
exotoxins
endotoxins
Diphtheria toxin
(toxin of Corynebacterium diphtheriae)
Corynebacterium diphtheriae strains that carry a _______ with the structural gene for the toxin are toxigenic and produce diphtheria toxin.
This native toxin is enzymatically degraded into two fragments: ____ and ____, linked together by a ____ bound. Both fragments are necessary for toxin activity.
temperate bacteriophage
A and B
disulfide
Tetanospasmin (toxin of Clostridium tetani)
Clostridium tetani is an (aerobic or anaerobic?) gram-______ —— that is
widespread in the environment.
Clostridium tetani contaminates _____, and the spores germinate in the anaerobic environment of the devitalized tissue.
Anaerobic; positive ; rod
wounds
The vegetative forms of Clostridium tetani produce toxin ______. The released toxin has two peptides linked by disulfide bounds. Toxin reaches the central nervous system by ____ transport along _____ and through the _____ circulation. The toxin acts by blocking release of (excitatory or inhibitory?) mediator in motor neuron synapses. The result is initially _____ then _____, _____.
tetanospasmin
retrograde
axons; systemic
inhibitory; localized; generalized
muscle spasms
Extremely small amount of toxin tetanospasmin can be lethal for humans.
T/F
T
Botulotoxin (toxin of Clostridium botulinum)
An exceedingly potent toxin is produced by Clostridium botulinum strains. It is heat-(labile or stable?) and is destroyed by ________.
There are _____ disctinct serological types of toxin. Types ___ are most commonly associated wih human disease.
Toxin is absorbed from the ______ and carried to motor nerves, where it blocks the ___________ at synapses and neuromuscular junctions. Muscle ______ does not occur, and ______ results.
Labile; sufficient heating
eight; A, B and E
gut; release of acetylcholine
contraction; paralysis
the most potent toxin known is ??
Botulotoxin
Toxins of Clostridium perfringens
Spores of Clostridium perfringens are introduced into the wounds by contamination with ________. In the presence of ______ tissue (an anaerobic environment), spores germinate and vegetative cells produce several different toxins.
Many of these are _______ and _____ and favour the spread of ______, eg:
alpha toxin is a _____ that damages ________
______ toxin also has a necrotizing affect
and other
soil or faeces
necrotic
necrotizing and hemolytic
gangrene
lecithinase; cell membranes
theta
Streptococcal erythrogenic toxin( aka streptococcal ___________ toxin)
Some strains of hemolytic lysogenic streptococci produce a toxin that results in a _______________________________ rash, as in _______.
Production of erythrogenic toxin is under the genetic control of ________. If the phage is lost, the streptococi cannot produce toxin.
Pyrogenic
punctate maculopapular erythematous
scarlet fever
temperate bacteriophage
Toxic shock syndrom toxin - 1 (TSST-1)
Some _____________ strains growing on mucous membranes (e.g. on the vagina in association with menstruation), or in wounds, elaborate TSST-1.
Although the toxin has been associated with toxic shock syndrome, the mechanism of action in unknown.
The illness is characterized by ____,___, and a diffuse _____ that later desquamates, multiple other organs systems are involved as well.
Staphylococcus aureus
shock, high Fever
red rash
Exotoxins are associated with diarrheal diseases
T/F
T
Cholera toxin and E. coli labile toxin
Causes ______ of regulator
That leads to _______ activation leading to increase in _____
There’s _______ that leads to the diarrhea
ADP-ribosylation
adenylate cyclase
cyclic AMP
active ion and water secretion
Shiga toxin -_______
Shiga-like toxin – enterohemorrhagic E. coli
• lyses _____- in ribosome leading to death of __________
• poor ________ that sums up into diarrhea
shigellosis
28S rRNA
epithelial cells
water absorption
Endotoxins of gram-negative bacteria
The endotoxins of gram-negative bacteria are derived from bacterial _______ and are often liberated when the _________.
The substances are heat-(labile or stable?) and can be extracted (e.g. with ________)
cell walls; bacteria lyse
Stable; phenol-water
Pathophysiological effects of endotoxins are similar regardless of their bacterial origin
T/F
T
Coagulase:
Staphylococccus aureus produce coagulase, which works in conjuction with serum factors to _______. Coagulase contributes to the formation of ______ around staphylococcal lesions, which helps them persist in tissues.
coagulate plasma
fibrin walls
Hyaluronidases:
Enzymes that _________, a constituent of the ground substance of connective tissue. They are produced by many bacteria (e.g. staphylococci, streptococci and anaerobes) and aid in their spread through tissues.
hydrolyze hyaluronic acid
Streptokinase:
many hemolytic streptococci produce streptokinase (________), substance that activates a proteolytic enzyme of plasma. This enzyme, is then able to ____________ and probably aids in the spread of streptococci through tissues.
fibrinolysin
dissolve coagulated plasm
Streptokinase is used in treatment of __________ to ________
acute myocardial infarction
dissolve fibrin clots
Hemolysins and leukocidins:
Many bacteria produce substances that are ______ - they ___________(hemolysins) or _____________ (leukocidins).
cytolysins
dissolve red blood cells ; kill tissue cells or leukocytes
Streptolysin O, for example, is produced by group ___ streptococci and is lethal for ____ and hemolytic for red blood cells from many animals.
A
mice
_______ proteases
help the following survive on external surfaces
H.________
S.________
N._______
N. ______
IgA
influenzae; pneumoniae; gonorrhoeae
meningitidis
Once bacteria enter the body of the host, they must ______.If they do not adhere, they would be _________ and other fluids that bathe the tissue surface.
adhere to cells of a tissue surface
swept away by mucus
Most common form of bio terrorism is ___?
By air
