Post Operative Complications: Healthcare Associated Infections Flashcards Preview

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Flashcards in Post Operative Complications: Healthcare Associated Infections Deck (29):

Fever, tachycardia and low BP are common signs post surgery of....

Healthcare associated


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

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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

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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?

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  • Bladder catheter → 95% of UTIs
  • Indwelling vascular catheter → 87% of blood stream infections 
  • Mechanical ventilation → 86% of pneumonia


How common are device-associated infections

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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
  1. single bacteria; cells float through bloodstream and start to make a gooey protein material 
  2. This starts to stick to things, eg; metal, teeth etc and start to build a thick structure that is many layers of bacteria.
  3. The top layer can come apart and end up once again as single bacteria in the blood stream, re infecting other surfaces

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What are the factors that contibute to pathogenesis of device-associated infections

  • Host
  • Device
  • Bacteria

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What are the bacterial factors in the pathogenesis of Device-associated infection?

Most common bacteria: Staphylucoccus epidermidis, Staphylococcus aureus, Escherichia coli


  • 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


  • 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

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Staph aureus is a very common cause of 

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skin and soft tissue infections and a common cause of indwelling catheters


What can you do to prevent device-associated infections?

  • Reconsider requirement for the device
  • handwashing before and after touching the device
  • place the device appropriately under aseptic conditions; avoid femoral site
  • Monitor devices carefully for signs of infection
  • remove unnecessary devices
  • reduced central venous catheter infection by 66%


How to treat device ass. infections

  • Cannula removed and replaced if needed
  • Receive antibiotic treatment
    • if staph aureus treat with flucloxacillin (if MRSA strain this will not work)


Likely source and mode of transmission of this infection??

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  • 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


Who are the people most at risk of a clostridium difficile infection?

  • Hospital patients receiving antibiotics: reduce numbers of major general of non-endospore forming anaerobes in the colon. C. difficile may be sensitive to antibiotic but survive as endospores and out-compete other species post treatment
    • beta lactams and clindamycin especially
    • fluoroquinolone (epidemic) 
  • Longer than 1 week in hospital
    • time to become colonised 
  • other treatments that disrupt to colonic flora
    • ​removes competition, allows C. difficile to grow!


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)

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What are the two Clostridium difficile virulence factors?

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Toxin A and Toxin B

  1. These are really big toxins release by bacteria into gut.
  2. They then attach to epithelium of colon and endocytosed into those cells.
  3. When these cells get acidified protein changes its confirmation and is secreted into the cytosol
  4. effects G-protein glucosylation causing it to be constantly on
  5. changes the cells aintanence of actin skeletona and the cell can collapse.
  6. 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

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This is?

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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

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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

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Treatment of Clostridium difficile?

  • Stop implicated antibiotic: this can be enough in mild cases
  • Treat with anti- C.difficile antibiotic
    • IV metronidazole
    • oral vancmycin
  • Support fluid loss/pain
  • Restoration of microflora/probiotcs: what is going to help long term and out-compete the clostridium. Best thing is a faecal transplant


Whats the concern for  the rest of the ward if a patient has Clostridium difficile infection

  • Potential for an outbreak as they are producing infectious spores
  • Attention to hygiene and cleanliness
    • thorough cleaning where infected patients have been 
    • general attention to cleanliness to prevent patient to patient spread
    • hand hygiene. Toilet disinfection regime. Sporocidal disinfectant
  • Limit use of predisposing antibiotic
  • Note theres a 20% relapse rate



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