Lecture 4 Flashcards
Where are microbes?
Everywhere.
What is infectivity?
Ability of microbe to establish itself on the host or within the host.
What is virulence?
Capacity of the microbes ability to do damage to the host.
What is the immune system?
Cells and organs (i.e. spleen) that contribute to immune defences against infectious and non-infectious (e.g.cancer) conditions. (self vs non-self)
Why is the spleen important?
-organ that reacts to blood bourne pathogens (T/B cells)
How does the immune system recognise the pathogen?
Pathogen recognition: Cell surface/ soluble receptors
What is the main role of the immune system?
Contain/eliminate infection (killing/clearance mechanisms)
Remember the pathogens preventing reoccurrence
Regulate itself- minimum damage to the host (otherwise you develop autoimmune disease)
What are the different types of immunity?
Innate (first line of defence) -immediate protection -fast -lack of specificity/memory -no change in intensity Adaptive (microbe through innate immunity) -slow -specificity (recognise gram+/-, different strains of the same pathogen) -immunologic memory -changes in intensity
What are the barriers of the innate response?
Barriers to stop pathogen entering
- physical barrier (skin, muscles membrane of mouth, resp/GI/urinary tract, bronchial cilia-beat, expel trapped microbes in mucous)
- physiological barriers (diarrhoea, vomiting, coughing, sneezing)
- chemical barriers (low pH [skin 5.5, stomach 1-3, vagina 4.4], antimicrobial molecules)
- biological barriers (normal flora-compete with pathogens for attachment sites and resources, produce antimicrobial chemicals, synthesise vitamins)
Give some examples of antimicrobial molecules:
-IgA (tears, saliva, mucous membrane)
-Beta-defensins (epithelium)
-gastric acid
-
Where are normal flora found?
Non pathogenic microbes (if in correct place-not in tissues/organs)
- nasopharyx
- mouth/throat
- skin
- GI tract
- vagina (lactobacillus)
Give some examples of normal flora that inhabit the skin/nasopharynx:
Skin
- staphylococcus aureus (cellulitis)
- staphylococcus epidermidis
- streptococcus pyogenes
- candida albicans (
When is normal flora displaced?
Breaching of skin integrity -skin loss (burns) -surgery -IV line -skin diseases -injection drug users -tattoo/piercing Feta-oral route -foodbourne infection Poor dental hygiene -dental extraction -gingivitis -brushing/flossing
What are some high risk patients?
- asplenic patient (no spleen)
- patients with damaged or prosthetic valves
- patients with previous endocarditis
Give some examples of auto immune disease:
- diabetes
- AIDS
- malignant diseases
- chemotherapy (mucositits- inflammation of muscosal membrane )
How is Normal flora depleted in muscosal surfaces by antibiotic therapy?
Vagina: thrush (candida
What are exogenous and endogenous microbes?
Exogenous
Endogenous - already on the body
What are the main phagocytes?
- macrophages
- neutrophils
- monocytes (precursor or macrophages)
What are the key cells of innate immunity?
- basophils/mast cells
- eosinophils
- Natural killer cells (viral infection)
- dendritic cells
What are PAMP’s?
Pathogen associated molecular patterns (pathogen recognition)
(Phagocytes contain PRR’s:pathogen recognition receptors)
What are some gram+/- types of bacteria?
+ peptidoglycan
+lipo
What is opsonin receptor?
Sticky molecule that binds to microbe.
-phagocytes have opsonin receptors so can now bind
When they bind it signals the phagocyte to kill the microbe
(Macrophages produce cytokines which signal the liver to make CRP)
Why is the spleen good at clearing encapsulated bacteria?
….
What is the process of phagocytosis?
H
What are the 2 phagocyte intracellular killing mechanisms ?
Oxygen dependent
What are the complement pathways?
Alternative
MBL
What cytokines are produced by macrophages when they sense the pathogen/microbe?
TNF alpha
IL-1
IL-6
What are some clinical problems when phagocytosis is reduced?
Decreased spleen function
Decreased neutrophil
What 3 factors determine the outcome of the host pathogen relationship?
- infectivity
- virulence
- host’s immune response
What categories of people have immune deficiency?
- children
- elderly
What is an infectious disease?
When the pathogen suceeds in evading/overwhelming the host’s immune defences
