question
What is bacterial pathogenesis?
answer
The mechanism by which a bacterial pathogen produces disease
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What is a bacterial pathogen?
answer
a bacteria that is capable of causing disease in a host
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what is a virulent pathogen?
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an exceedingly pathogenic organism
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what is an avirulent pathogen?
answer
a non pathogenic organism
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what is an attenuated pathogen?
answer
a less pathogenic organism
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what is a host?
answer
an organism that harbors another organism
ex. human
ex. human
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Mutualistic relationship
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both organisms benefit from the relationship
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commensalistic relationship
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one organism benefits while the other neither benefits nor is harmed
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parasitic relationship
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one organism benefits (parasite) from the relationship and the other organism (host) is harmed
ex. bacterial pathogens
ex. bacterial pathogens
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does the presence of bacteria indicate disease?
answer
no
ex. normal flora
ex. normal flora
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colonization
answer
establishment and multiplication of a microorganism in a host
pathogen or non-pathogen
ex. normal flora colonize the skin
pathogen or non-pathogen
ex. normal flora colonize the skin
question
infection
answer
refers to the multiplication of a PATHOGEN in a host with or without disease
can be with or without symptoms
can be with or without symptoms
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disease
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occurs when an infected host is injured or damaged in a manner that impairs host function
ex. symptoms
ex. symptoms
question
normal flora
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bacteria that establish permanent colonies inside or on the body without producing disease
ex. humans are bacteria free in utero but begin to develop flora soon after birth
ex. humans are bacteria free in utero but begin to develop flora soon after birth
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bacterial antagonism
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the normal flora can prevent colonization by pathogens because the normal flora is taking up room and nutrients
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opportunistic pathogens
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do not cause disease under normal conditions but can cause disease under special conditions
ex. staphylococcus epidermis
ex. staphylococcus epidermis
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Why antibiotics can be harmful in the long run
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they target both pathogens and beneficial bacteria
destroying the normal flora opens the door for opportunistic pathogens
Pathogen specific drugs would be more useful
destroying the normal flora opens the door for opportunistic pathogens
Pathogen specific drugs would be more useful
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Example of a good bacteria being wiped out by antibiotics
answer
H. Pylori used to be the dominant bacteria in the stomachs of all people. Antibiotics has drastically reduced the populations
lack of H. Pylori colonization can lead to asthma, hay fever and skin allergies
lack of H. Pylori colonization can lead to asthma, hay fever and skin allergies
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Locations of resident bacterial normal flora in humans
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number of microorganisms is about 1x10^4
2-3 pounds of bacteria in GI tract
500-1000 species in gut and about the same number on skin
2-3 pounds of bacteria in GI tract
500-1000 species in gut and about the same number on skin
question
Normal Flora - skin
answer
bacteria colonize moist areas of the skin [usually associated with apocrine sweat glands]
sweat has nutrients and moisture for organisms
mostly colonized by gram-positive bacteria
sweat has nutrients and moisture for organisms
mostly colonized by gram-positive bacteria
question
Ex. of Normal Flora - Skin
answer
Staphylococcus spp.
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Normal Flora - Oral Cavity
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extensive growth of bacteria form biofilms called dental plaque
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dental plaque
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biofilm of bacteria on teeth
as plaque gets thicker, other bacteria join in, even anaerobic
eventually leads to decalcification of the tooth enamel due to the organic acids from the bacteria
as plaque gets thicker, other bacteria join in, even anaerobic
eventually leads to decalcification of the tooth enamel due to the organic acids from the bacteria
question
dental caries
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caused by the decalcification of the tooth enamel
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Ex. of Normal Flora - Oral Cavity
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Streptococcus spp.
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Normal Flora - GI tract
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GI tract has the most bacteria in numbers and species
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benefits of GI microflora
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synthesis of Vitamin B12 and Potassium [K]
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Normal Flora - Respiratory tract
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upper respiratory tract is heavily inhabited
lower respiratory tract is essentially sterile
the presence of the normal flora prevents pathogens from multiplying/replicating
lower respiratory tract is essentially sterile
the presence of the normal flora prevents pathogens from multiplying/replicating
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Normal Flora - Urogenital Tract
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Bladder is normally sterile
urethra and vaginal surface are colonized
urethra and vaginal surface are colonized
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How bacteria/pathogens cause disease
answer
Contact Host [Transmissible]
Colonize/infect the host [adhere to host surface/multiply]
evade host defense system [prevent elimination]
Damage host cells/tissues [spread, release nutrients]
Colonize/infect the host [adhere to host surface/multiply]
evade host defense system [prevent elimination]
Damage host cells/tissues [spread, release nutrients]
question
virulence factors
answer
factors responsible for the virulence of a pathogen
they promote colonization and survival of a pathogen as well as damage the host
they promote colonization and survival of a pathogen as well as damage the host
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virulence factors that promote colonization and survival
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adhesins
invasins
evasins
invasins
evasins
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Virulence factors that damage the host
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Toxins
Enzymes
Enzymes
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Bacterial colonization
answer
first stage of a bacterial infection
occurs at portal of entry
pathogens must be able to adhere to the eukaryotic cells or tissue at a portal of entry and withstand the host's defenses
occurs at portal of entry
pathogens must be able to adhere to the eukaryotic cells or tissue at a portal of entry and withstand the host's defenses
question
bacterial Adhesins
answer
bacterial cell surface proteins or structures that bind to specific host cell receptors on epithelial cells or other exposed cells
question
two step process of bacterial adhesion
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Initial loose attachment
Strong or intimate attachment
followed by invasion of tissues in some cases
Strong or intimate attachment
followed by invasion of tissues in some cases
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Bacteremia
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bacteria in blood
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Septicemia
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bacteria growing and multiplying in the blood
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Extracellular Pathogens
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attach to receptor molecules on host cell surface and remain extracellular
question
intracellular pathogens
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invade host cells and multiply inside these cells
question
examples of intracellular pathogens
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facultative intracellular pathogens
obligate intracellular pathogens
obligate intracellular pathogens
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facultative intracellular pathogens
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can grow inside cells or outside cells
question
obligate intracellular pathogens
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only grow inside eukaryotic cells
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advantages of intracellular life
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host can't attack without harming its own cells
safe from antibodies, complement proteins, and some antibiotics
access to host cell nutrients of cytoplasm
safe from antibodies, complement proteins, and some antibiotics
access to host cell nutrients of cytoplasm
question
disadvantages of intracellular life
answer
must exit cells at some point in order to exit host and be transmitted to new host
question
advantages of extracellular life
answer
provides greater opportunity for rapid growth, reproduction and spreading
question
disadvantages of intracellular life
answer
must deal with antibodies, complement proteins etc
pathogen must compete with normal flora and other potential pathogens
pathogen must compete with normal flora and other potential pathogens
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