Lecture 40: POC- healthcare associated infections Flashcards
Common areas of infections post operatively?
Bladder infections related to uriniary catheters are common but are not life threatening and rather just uncomfortable
Blood infections related to canula insertions are also common and are much more life threatening and need to be urgently treated
What is a biofilm?
A common occurrence where a microbial community of cells that attach to a substrate or interface or to each other, embedded in a matrix of extracellular polymeric substance.
Bacterial Factors affecting infection?
Most common Bacteria:
- Staphylococcis epidermidis
- Staphylococcus aureis
- Escherichia coli
Factors:
- Non-specific (hydrophobicity, electrostatic forces) - stahpylococci, enterococci etc.
- Adhesive proteins (MSCRAMMs)
- Polysaccharide intercellular adhesin (PIA)
% of infection caused by different mircoorganisms?
Gram Positive
- 50-60% of nosocomial bacteremic events
- Mostly Staphylocossus epidermidis and aureus
Gram Negative
- 30% of all episides of bacteremia
- mostly E. coli
Fungi
- mostly Candida
Devices that favour bacterial adhesions?
- Device material
- PVC > teflon, steel > titanium
- Source of material
- Synthetic > biomaterial
- Surface of device
- Textured > smooth
- Shape of device
- Polumeric tubing > wire mesh
BUT REALLY THE MOST IMPORTANT THINGS ARE :
- How long the device has been in
- How well it has been put in
- How often it is utelised
Problems with biofilms developing?
- Antibiotics find it hard to reach bacteria deeper in film
- Can be a change in phenotype
- Can be a change of cell surface properties - increasing antibiotic tolerance
- Slower growth rate - more resistant to antibiotics
- Persister cells: Specialised survivor cells that are resisitant to antibiotics
- Difficult to determine antibiotic resistance (can’t do standard dilution tests)
Infection of cannula in arm is most likely to be? Next steps? Treatment?
Most often it is Staphylococcus aureus - we would send off a sample to the lab to be tested (blood, pus or even the tip of the cannula that has been in the persons arm)
If it is infact staph then we would treat with IV antiobiotics for 14 days - flucloxacillin would be given as 90% of staph in NZ can produce B-lactamase and so is resisitant to penicillin
Prevention of infection?
- Sterile technique always being used
- Only put in when necessary and take out when not being used
- Get the right people to put them in
Clostridium difficile?
Is part of the normal floca of the GI tract and carriage rates are around 5% in the community and up to 20% in hospitals.
Spread from person to person within hospital wards by diarrhoea contaminating the environment, unhygenic practices (not washing hands properly after going to the bathroom)
Has long lived bacteria endspores that survive in aerobic envronents until it getis into another anaerobic environment (the gut)
Peopl most at risk of C difficile?
Hospital patients recieving antibiotics - beta lactamas and clindamycin especially
Patients in hospital for longer than a week (time to be colonised)
Other treatments that distrupt the colonic flora (removes competition)
Colonisatoin factors and the likely route of colonisation? (C difficile)
- Antiobiotics reduce numbers of major genera of non-endospore forming aerobes in the colon
- C. difficile grows to high numbers, where it produces toxins
- C. difficile may be sensitive to antibiotics but survives as endospores and out-compete other species when treatment is stopped.
(Endospores are dormant, survival structures and not reproductive - only produces by species of Bacillus and Clostridium)
How do C difficile toxins work? Outcome?
- Attachment
- Endocytosis
- Acidification and release of toxin
- Interference with G-protein glucosylation
- Actin depolymerisation
= Collapse of the actin cytoskeleton
Pseudomembrane forms over the dead tissue (ulceration) - made of dead cells, WBC, mucus etc.
Toxic megacolon occurs when there is severe inflammation and it may need to be removed as it can perforate leading to death.
Diagnosis of C difficile?
Antibody test for the toxin in the person’s stool - (bacterial culture not useful as 20% on the hospital will be cerriers)
Sometimes the toxin levels aren’t high enough but there is bacteria culturing for C difficile with no other obvious cause of the diarrhoea. We can then in this case to PCR to look for genes that encode for the toxins.
Treatment for C difficile?
- Discontinue implicated antibiotic
- Treat with anti-C. difficile antibiotic -(IV metronidazole or oral vancomycin)
- Symptomatic treatment (fluid loss/pain)
- Restoration of microflora/probiotics
