(MT 2) Topic 1: Immunity to Bacterial Pathogens Flashcards
Human microbiome
all the microbes that call us home and mostly keep us healthy
“happy passengers”
very few are actually pathogens
Pathogen
microbes that cause disease
Infection
microbe replicates in/on host beyond its normal role
Disease
microbial infection damages the host
Difference between Infection and Disease
There’s host damage in disease
Pathogenicity
ability of an organism to cause disease
whether to cause disease or not
Virulence
the extent to which a microbe can cause disease
how quickly it can cause disease
Virulence factors
the adaptations and traits that promote virulence in a pathogen
can be broader than some gene that they use or toxin; can be more subtle than that.
don’t have to be unique to that microbe (they can be but nor necessary)
Two Main Types of Pathogens
- Opportunistic Pathogen
- True Pathogen
Example of an opportunistic pathogen
S. aureus
Opportunistic infections can result from opportunistic conditions such as: (2)
- compromised immune system
- disruption in the balance of normal microbes
Two types of true pathogen
- Obligate pathogen
- Facultative pathogen
Obligate pathogen
give an example of a disease
- pathogens must cause disease to be transmitted
ex: Herpes
Facultative pathogen
give an example of a disease
- can cause disease but does not require a host to complete life cycle.
ex: Vibrio cholera
Does the presence and even growth of microorganisms on the host always lead to disease?
No, The presence and even growth of microorganisms on the host does not always lead to disease.
The interactions between the host and the microbe both contribute to the final outcome. This relationship is influenced by __________________ and ___________________.
- virulence of the microbe
- the defense mechanisms of the host
There are many steps to establishment of infection that start with: colonization, persistence and spread.
These can be subdivided into: (5)
- exposure to pathogens
- adherence to skin or mucosa
- invade host tissue through epithelium
- immune evasion
- host damage
How does bacteria access your nutrients?
It’s gonna damage you to access your nutrients
Do you get sick right away by getting exposed to a bacterium that is pathogenic?
No. Just because you’re exposed to a bacterium that is pathogenic doe snot mean you’re getting sick. The bacteria has to stick to you and penetrate into you.
Each step in the establishment of infection requires unique _____________ strategies for the pathogen
evasion
Pathogen Profile
Staphylococcus epidermidis (S. epidermidis)
- gram positive
- example of an opportunistic pathogen
- normal component of the skin microbiome and important in protecting skin form unwanted pathogens
- Encounter/Exposure -ubiquitous component of skin microbiome.
- Host entry -noscomial (hospital-borne); particularly it adheres to plastic catheters, pacemakers, implants as a biofilm.
- Adhesion and Invasion -tolerates changing osmolarity
-adheres via teichoic acid association to the plasmid
-binds extracellular matrix components of the host. - Immune system evasion -biofilms provide resistance to AMPs and antibodies and mechanical removal.
-extensive efflux pumps -provides AMP resistance; if you can get your host defenses into the bacterium, bacterium spits them out-efflux pumps pump them out. - Host damage -PSM=phenol-soluble modulins -damages membrane to allow access to host resources
PSM (phenol-soluble modulins)
damages membrane to allow access to host resources.
found in S. epidermidis
He developed the Germ Theory of Infectious Disease and disproved the notion of spontaneous generation of microbes and miasma (“spirits”) theory for the spread of disease.
He also explained why so many people died of infection after surgeries where handwashing and antiseptic technique was not practiced.
Louis Pasteur
How did Pasteur show that microbial cells arise from preexisting cells?
- Put beef broth into flash
- Heated neck of flask to introduce bend
- Boiled broth to sterilize
- Air could enter flash through bent neck, but microbes got stuck in the bend- bend in flask removed the route of entry of new microbes.
- Broth stayed sterile
He studied the theory that microorganisms cause human disease. He showed a cause and effect relationship between pathogen and disease.
Robert Koch
Koch’s postulates
- pathogen must be present in all cases of the disease.
- pathogen must be grown in pure culture.
- pathogen must cause disease from pure culture.
- pathogen must be reisolated from the organism where you induce the disease.
Pathogen Profile
Treponema pallidum
Example of Koch’s postulate in action
- believed to be the causative agent of STI syphilis
- spirochete
- has endoflagella where two or more flagella originate from opposite poles of the bacterium and are located in the periplasmic space.
- avoids recognition by the innate immune system and TLR5
- bacterium has never been grown in the lab and doe snot have an animal model.
What can treat syphilis and how many % is it asymptomatic?
Antibiotics, 43%
In 2017,
CDC- ___-____% of American population had previous syphilis infection.
15-20%
Case study
Clinical case of a woman with a year-long mouth ulcer in rural Uganda
- was about to go in for surgery to remove a presumptive tumor
- did ELISA and pathological analysis- T. pallidum spirochetes were detected
- Penicillin G managed the infection and it resolves in 2 months.
TRUE or FALSE
Alternative methods can be used to satisfy Koch’s postulates
TRUE
