13. Bacteria-host interactions Flashcards
What kind of microbe-host interactions do we have
Contamination
Colonization
Infection
What’s contamination
The host encounters the mo when it reaches the skin or mucosal sirfaces
What’s colonization
Mo finds ideal conditions for its settlement in a specific host district and starts proliferation( cell growth and division)
Is presence of mo in host district immediately an infection or a disease
No
What’s infection
Mo in specific district establishes a balanced relationship with the host defenses
Does infection leave sign on host’s immune system
Yes
What are districts in a human body where we shouldn’t find mo and finding them indicates severe infectious disease
Blood, internal organs, lymphatic system and nervous system
What are colonized districts of the human body
Skin and mucous membranes
How does normal microbic flora get to the organism
All organisms are sterile in utero. After birth, skin and many mucous membranes become rapidly colonized by non pathogenic microbes(normal microbic flora, microbiota)
Are microbiota beneficial
Yes, and they don’t cause diseases. They can participate in synthesis of vitamins and protection from pathogenic bacteria
What are some examples of microbiota?
Lactobacillus spp.; Bacteroides spp.; viridans streptococci, enterobacteriales and Candida spp.
What factors are impacting the change of endogenous microflora
Age, gender( hormonal state), diet, health state, drugs
What type of colonization can we have
Transient and chronic
What’s disease
Interaction that leads to harmful pathogenic process
What does disease depend on
Microbial factors
Host immune response against mo
Host genetic factors
What is pathogenicity
Ability of mo to cause a disease
What does pathogenic potential depend on
Virulence factors and mechanism(mo related)
Initial inoculum(initial number of infecting bacteria
Immune status and health conditions of the host( host related)
What’s virulence
Degree of which a pathogenic organism can cause a disease
What does virulence depend on
Infectivity: ability to establish an initial infectious outbreak
Invasivity: ability to spread to other host tissues escaping the host defense mechanisms
Toxinogenicity: ability to produce toxins
What are nonpathological bacteria
Bacteria that don’t cause infection in humans
What are pathogenic bacteria
Bacterial species that are always pathogenic and their simple presence indicates a pathological process
Do pathogenic bacteria abide by Koch’s postulates
Yes
What are opportunistic pathogenic bacteria
Bacterial species that constitute the normal microbic flora in humans and animals and can cause diseases only in immunodepressed or debilitated subjects
What are occasional pathogenic bacteria
Bacterial species that don’t usually interact with the host, but whenever they are innoculated in host tissues they can cause disease
When do opportunistic bacteria become pathogenic
When:
1. They change host district( ex: E.coli can cause urinary tract infectious)
2. Habitat is altered
3. Immature/ decline of host defenses
What is successful pathogenic microbe
Microbe that can adopt specific counteracting strategies to overcome host defense barriers
What are portals of entry for mo
Mucous membranes, skin, parenteral route, endogenous infections
What is colonization a result of
Virulence mechanism that make microbe able to:
-Adhere to the host cells and tissues
-Invade the host tissues
-Resist the innate immunity
-Escape adaptive immunity
-Compete for nutrients
What are the steps of bacterial pathogenic process
1.Exposure
2.Adhesion
3.Colonization
4.Invasion
5.Proliferation
6. Tissue damage due to proliferation and alteration of host’s physiological functions
7.Host-mediated immunopathogenesis
What are exotoxins
Proteins that can be found both in gram+ and Gram - bacteria. They are released by cell in exponential growth and have different mechanism of action and effects.
When are exotoxins endowed activity
At very low concentrations
What can exotoxins target
Cell surface and intracellular components
What are endotoxins
Lipid portion that are part of outer membrane in Gram - bacteria. they are liberated when bacteria dies and the cell wall breaks apart
What components can be endotoxins
-LPS-lipopolysaccharide
-portions of peptidoglycan with endotoxin-like activity
-lipoteichoic acid( even if its from Gram +)
-other components of cell wall lining
Can proteins and enzymes be endotoxins
No
What do endotoxins do
Trigger nonspecific inflammatory reactions;
stimulate pro-inflammatory cytokine release;
induce complement activation;
stimulate proliferation of B lymphocytes and antibody production
induce fever
What is relationship between vaccines and endotoxins
Endotoxins act as adjuvant for vaccines
Adjuvant= substance that enhances body’s immune response to antigen
What are some mechanism by which pathogens evade immune response
-Inhibition or resistance to phagocytosis
-Degradation/inhibition of immune components: pathogens can degrade immune components( such as antibodies or complement proteins). Proteases break down these molecules, impairing immune function
-Antigenic mimicry :pathogens may host molecules to avoid detection. Strategies include:
*capsules : coating themselves with protective layer
*surface proteins : displaying proteins similar to host proteins
*binding to host proteins
