Post Operative Complications: Healthcare Associated Infections Flashcards
Fever, tachycardia and low BP are common signs post surgery of….
Healthcare associated
infection!
Remember in surgery there is both the skin level and organ level surgical stiches and change both
What does the significance of a urine sample from a catheter with >1000 million WBC/L have?
A urinary catheter if left in long enough will develop into pyuria.
So this can be ignored if it’s been in a while, look to see if there is somehing more suspicious going on (eg; fecal peritonitis from a ruptured bowel)
What is CA-UTI
an ILLNESS caused by bacterial infection associated with urinary catheter.
- presence of bacteria in the urine is very common (NB 3x risk of DEATH compared with people without bacteruria)
- prevalence: approx 10% patients with catheters
- approx, 100 (10% of inpatients) in ACH have an IDC in situ
- Risk factors: female, duration of catheterisation, poor care
- this is also a reflection of how unwell the patients are! There are many other factors!
- If you put a catheter in for long enough ANYONE WILL get an infection
- catheter bag never on bed so the urine can’t slosh back into patient!!
How do you recognise and identify a CA-UTI??
Specific symptoms may be lacking: fever, confusion, lethargy, flank pain
The presence of pyuria alone IS NOT DIAGNOSTIC: absence of pyuria however suggests an alternate diagnosis
The presence/absence of smelly/cloudy urine IS NOT DIAGNOSTIC:
Cultures usually show 1 bacterial species eg; E.coli
if no WBC you can relax!
What strategies might reduce CA-UTI??
- avoid catheters: use non-invasive condom devices instead of urethral device
What is the significance of Candida albicans as a pathogen?
The usual cause of thursh, but can also cause more invasive infections, usually only in the presence of catheters!
- one of ~150 candida yeasts
- but C. albicans is the most common cause of human illness (90%), nine species cause almost all human disease
- Found as part of human flora, in soil, on animals, hospital environments
- Unprovoked illness is RARE: usually due to some other illness/issue/medication in the host
- VERY RARE in healthy people and represents colonisation and in neonates it might represent candidaemia
If someone has the presence of C.albicans in the catheter do they require treatment??
- If there’s a belly infection and there’s something else going on then no
- If there’s no other problems but there’s fever, chills etc: removal of the catheter should be enough. Maybe take a sample after to be sure.
What medical devices cause Infections and to what extent?
- Bladder catheter → 95% of UTIs
- Indwelling vascular catheter → 87% of blood stream infections
- Mechanical ventilation → 86% of pneumonia
How common are device-associated infections
How do these bacteria actually cause the infection?
- They make a Biofilm
- a microbial community of cells that attach to a substrate or interface to each other, embedded in a matrix of extracellular polymeric substance
- single bacteria; cells float through bloodstream and start to make a gooey protein material
- This starts to stick to things, eg; metal, teeth etc and start to build a thick structure that is many layers of bacteria.
- The top layer can come apart and end up once again as single bacteria in the blood stream, re infecting other surfaces
What are the factors that contibute to pathogenesis of device-associated infections
- Host
- Device
- Bacteria
What are the bacterial factors in the pathogenesis of Device-associated infection?
Most common bacteria: Staphylucoccus epidermidis, Staphylococcus aureus, Escherichia coli
Factors:
- Non-specific (hydrophobicity, electrostatic forces)
- Adhesive proteins (MSCRAMMs)
- Polysaccharide intercellular adhesin (PIA)
Some bacteria stick to EVERYTHING and then others are very specific
Micro-organisms associated with Device-ass. infections
Gram positives (mainly)
- 50-60% of nosocomial bacteremic events
- mostly staph aureus and staph epidermidis
Gram negatives
- ~30% of all episodes of bacteremia at most institutions
- mostly E.coli, klebsiella pneumoniae, Pseudomonas aeruginosa, enterobacter aerognes
Fungi
- mostly candida
What are Device factors that favour bacterial adhesion?
Device material: PVC > Teflon, PE > PU, steel > titanium, latex > silicon
Source of material : Synthetic > biomaterial
Surface of device: textured > smooth, irregular > regular
Shape of Device: polymeric tubing > wire mesh
Host factors in device associated infections
- Can affect bacterial adherence to the device eg; host-tissue ligands (fibronectin easier to stick to)
- Immune response
Problems with biofil-associated bacteria
Staph aureus is a very common cause of
skin and soft tissue infections and a common cause of indwelling catheters
Likely source and mode of transmission of this infection??
- Clostridium difficile is part of the normalflora of the GI tract
- Carriage rates; 5% in community and 20% in hospital
- Spread from person to person within hospital ward
- diarrhoea; contiminates environment
- long-lived bacterial endospores
What are endospores?
What kills them
- Only produced by species of Bacillus and Clostridium
- A dormant, survival structure and not reproductive
- Endospore dormation for survival in hosptial situation
Killed by:
- Heat- autoclaving
- Chemicals: need to be sporicidal
Not killed by: heat pasteurisation, antibiotics and oxygen (even though the actual C. diff will die the spore wont)
What are the two Clostridium difficile virulence factors?
Toxin A and Toxin B
- These are really big toxins release by bacteria into gut.
- They then attach to epithelium of colon and endocytosed into those cells.
- When these cells get acidified protein changes its confirmation and is secreted into the cytosol
- effects G-protein glucosylation causing it to be constantly on
- changes the cells aintanence of actin skeletona and the cell can collapse.
- Colonic epithelial cells no longer have nice tight epithelial barrier and so watery diarrhea and thing from the gut can get into sub-mucosal tissue causing infections: eventual ulceration, pus, loss of water as diarrhoea and is now a pseudomembrane
This is?
Pseudomembrane colitis caused by Clostriium difficile.
Lots of dead cells, WBCs, mucins
What is a Toxic megacolon
Extremely severe case of colitis! Severly inflammed colon, may need to be surgically removed may perforate and even be fatal!
Spesis: from bacteria from colon leaking
Severe inflammation: colon just a cytokine factory of inflammation
Diagnosis of Clostridium difficle
- If they have Diarrhoea do a stool test to look for TOXIN (rather then bacteria as many people are colonised but asymptomatic)
- Antibody based assay for toxins
- May also do a PCR for toxin genes: can help even if you could find toxin with previous tests
…
