Bacterial Infections Flashcards
(43 cards)
What happens in Parasitic Host-Microbe interaction
One partner (the human host) is harmed
“harm” = “damage”
Other partner (the microbe) probably derives benefit.
Not always obvious what the benefit is
what is a parasitic organism
A Parasitic organism causes damage to its host
Viruses
Bacteria
Fungi
Protists*
Nematodes*
Helminths*
what does damage to host cause
disease
what is a pathogen
an organism participating in a parasitic interaction i.e. an organism that causes disease.
What is colonisation
growth of any microorganism within a host.
What is infection
growth of a pathogen within a host with concomitant damage to the host.
What turns a microorganism into a pathogen?
Two properties are needed
Ability to overcome non-specific defence (Innate immunity) mechanisms of the body
i.e. the ability to colonise and the Ability to cause damage
Can We can have colonisation without damage?
Yes, Damage without colonisation is relatively rare
Exception would be foodborne intoxication
Clostridium botulinum
What are some non-specific host defences?
- Rapid pH change inhibits microbial growth at the bottom of stomach
- Removal of particles including microbes by rapid passage of air over cilia in nasopharynx
- Mucus, cillia lining the trachea suspended and move microbes out of the body
- blood proteins inhibit microbal growth
- Flushing of urinary tract prevents colonisation
What is non-specific host defences
innate immunity
what are non-specific defenses always?
always active- instant response to infectious agent
What happens in innate immunity?
Individual components are not very powerful= collectively they exert a very powerful effect.
Each of the systems will be considered separately= no system works in isolation and physical, chemical, and biological barriers are closely integrated.
What barriers does innate immunity have
Physical Barriers
Chemical Barriers
Biological Barriers
General Barriers
What are physical barieers
Body surfaces need to provide a physical barrier
Skin
Thick layer of dead cells covered with keratin
Cannot be penetrated directly by microbes
How do pathogenic microbes cross skin?- after some form of direct trauma
How do micorbes overcome physical barriers?skin
Physical processes that damage skin integrity promote infection:
Wounds
Accidental trauma
Surgery
Biting insects
Ensure you can name some specific infections spread by biting insects
what are mucus membranes and how are they related to physical barriers
Mucus Membranes
Layer of epithelial cells covered with mucus
Vulnerable to penetration
Normally lining areas exposed to a flow of material
Examples??- nositals, mouth, anus, ears
How do pathogenic microbes overcome such a barrier?- they collect on mucosal surfaces in large numbers that overcome the mucus or cilia
where do most infections begin
in the mucus membrane- The most common infections are gastrointestinal or respiratory infections.
How do microbes overcome physical barriers in mucus membranes?
Direct damage of mucus membranes is not normally encountered:
Adhesion of pathogens to mucus membranes-invasion of the epithelial layer and a deeper penetration into the body.
Anchoring pathogens in Gut, respiratory tract etc.
What are alternative physical barriers
respiratory cilia, nasal baffle plates, gut peristalsis and urine flow
What is respiratory cilia
On epithelial cells of the respiratory tract
Trap particles (pathogens) in mucus and beating moves them upwards to be swallowed or coughed up
Interference with cilia increases respiratory infection
SMOKING
Medical ventilation
What are nasal baffle plates
acts as a filter for larger particles
what are gut peristalsis
Constant movement of longitudinal and circular muscles in the GI tract. Makes it difficult for pathogens to attach to these mucus membranes
what is urine flow
Regular flow of liquid removes pathogens
Interference with urine flow predisposes to Urinary Tract Infection. UTI a major complication of the use of catheters
what are the chemical barriers on the skin?
high salt
pH 5-6
low water availability
