Immunity to Bacterial Pathogens Flashcards
What is the human microbiome?
All the microbes that call us home
Very few microbes are pathogens
What is a pathogen?
Microbes that can cause disease
What is an infection?
When a microbe replicates in or on a host
What is disease?
When microbial infection damages the host
What is pathogenicity?
The ability of an organism to cause disease
Qualitative trait
What is virulence?
The extent to which a microbe can cause disease
What are virulence factors?
The adaptations and traits that promote virulence in a pathogen
What is a good pathogen?
One that makes us just sick enough so that it can find a new host
What is a bad pathogen?
One that kills us before it has the chance to find a new host
What is an opportunistic pathogen?
One that takes advantage of weakened immune systems (immunodeficiency) and causes a disruption in the balance of normal microbes
What is an obligate pathogen?
The pathogen must cause disease to be transmitted
What is a facultative pathogen?
The pathogen can cause disease but does not require a host to complete its life cycle
What contributes to the final outcome of the disease?
Interactions between the host and the microbe
What is the relationship between the host and the microbe influenced by?
Virulence of the microbe
The defense mechanisms of the host
What are the steps to the establishment of infection?
Pathogen encounter
Host entry
Adhesion and invasion
Immune system evasion
Host damage
What is the gram stain of S. epidermidis and what type of pathogen is it?
Gram-positive
Opportunistic bacteria
What is the typical role of S. epidermidis?
It is a normal part of the skin microbiome and important in protecting the skin from unwanted pathogens
How are we exposed to S. epidermidis?
It is very hardy as it is an ubiquitous component of the human skin
How does S. epidermidis enter the host?
Typically nosocomial (hospital borne) through catheters, pacemakers, and plastic implants as a biofilm
How does S. epidermidis adhere and invade?
Tolerates changing osmolarity
Adheres via hydrophobic associations
Teichoic acid polymers associate with plastic
Bacterial components bind ECM component of the host (collagen in particular)
How does S. epidermidis evade the immune system?
Biofilms provide resistance to antibiotics and protections from AMPs
AMP resistance through efflux pumps
Extensive antibiotic resistant genes
PGA - poly-gamma-glutamic acid production in capsule-like exopolymer
What does PGA do?
Protect against phagocytosis and AMPs
How does S. epidermidis damage the host?
Through PSM’s (phenyl-soluble modulins) which allows access to host cells
What did Pasteur show?
That cells arise from preexisting cells
What was the bubonic plague’s causative agent and its route of entry?
Y. pestis and through flea bites
How does Y. pestis cause infection?
It replicates in the macrophages and the macrophages then migrate to the lymph nodes
Buboe’s form which is the next route of exposure
What did Koch show?
A cause and effect relationship between pathogen and disease
What were Koch’s postulates?
- Pathogen must be present in all cases of disease
- Must be grown in pure culture
- Must cause disease from the culture
- Must be able to reisolate the pathogen in that same form
