Session 7 Flashcards
(24 cards)
Define surface
The interface between a solid and liquid/gas
What is important to remember about the surfaces of the body?
They are likely to have residential flora eg skin
BUT some are meant to be sterile eg heart valves
What Gram negative fecal organisms does everyone carry from the waste down?
Enterobacteriase
What Gram positive bacteria does everyone carry on their skin?
Coagulase negative staphylococci
What Gram positive bacteria does 1 in 3 people carry on their skin?
Staphylococcus aureus
How can microbiota (commensals) be transferred to other sites where they can cause harm?
Invasion
Migration
Innoculation
Haemotogenous
How does Innoculation cause commensals to be transferred?
A scalpel can introduce bacteria into a new place eg Coagulative negative stapohylococcus into a prosthetic joint
How can haemotogenous tranferring cause commensals to be harmful?
The blood stream can be used to deliver commensals to harmful sites. eg viridans Streptococci endocarditis
What are some examples of prosthetic surface infections?
Catheters
Cardiac valves
Prosthetic joints
Endovascular grafts
How can infections occur on prosthetic joints?
Low virulence bacteria bind to the joint
How does prosthetic valve endocarditis occur?
Blood flow over the vales is abnormal which leads to turbulence and endothelial damage
This exposes viridan streptococci receptors
viridan streptococci binds
Vegetation occurs (Made of bacterial defences eg biofilm)
Endocarditis
Why is it hard to manage infections with a biofilm?
It is very hard to penetrate the Biofilm (Made of proteins etc) to get to the bacteria making it.
What is the process of pathogenesis of infections on surfaces?
Adherence
Biofilm formation
Invasion (of host tissues) and multiplication
Host respone (Pyogenic - Pus forms. Granulomatous)
How do pili/fimbriae aid bacteria?
They help adhere to the memebranes
How do bacteria excrete waste products from their biofilms?
There are channels that allow nutrients in and waste out (Biofilms use lots of energy)
What is Quorum sensing?
A system of stimulus and response correlated to population density of bacteria. Bacteria will coordinate gene expression depending on the stimuluses around them
What does Quorum sensing control?
Sporulation
Biofilm formation
Virulence factor secretion
What are the 3 principles of Quorum sensing?
Signalling molecules - autoinducers Cell surface/cytoplasmic receptors Gene expression (cooperative behaviours and more autoinducer production)
What are virulence factors?
Molecules secreted and excreted by pathogens to allow them to establish an infection in many ways. eg Endo/Exo toxins
How can you use blood cultures to distinguish a source of infection?
Take a blood sample from the central line and a peripheral vein. Culture both and if the central line grows bacteria faster then it suggests the central line is the source of infection.
How can you use flushing to see if there is a biofilm in a cannula?
If you flush the cannula and there is related pyrexia it suggests that the cannula has a biofilm in it
What is the course of action for someone with an infected prosthetic joint?
Remove the infected prosthetic joint
Insert spacers
Place on antibiotics for around 6 weeks
Insert a new prosthetic joint
How can you prevent bacterial infections?
Maintain the natural surface’s integrity eg silver coated IV lines/catheters, no pressure sores, avoid breaches in surface epithelium - healing by primary intention.
Removing colonising bacteria
When is it hard to close a wound by primary intention?
If there is too much inflammation. In this case the wound needs to be protected from bacteria entering somehow
