Biofilm Formation in Cobe C3 Dialysis Machines

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Biofilm Formation in Cobe C3 Dialysis Machines

• British Renal Symposium
• 9th June 2001
• Gareth Murcutt
• Royal Free Hospital

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New Chamber
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January 2001
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What Is Biofilm?

• Biofilm is a polymer matrix formed by bacteria
• Bacteria produce these extra-cellular polymers
  using nutrients from the surrounding fluid
• These polymers become fixed to the inside of the
  hydraulic circuit

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Biofilm Formation
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Biofilm Up-close
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Effects of Bacterial Contamination

• Dialyser membranes are permeable to pyrogens
• Increased cytokine production occurs in patients
  exposed to contaminated dialysate .
• Both acute and chronic effects on patients are
  well documented

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Endotoxin Results 1997
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Endotoxin Results 98/99
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Machine Audit

• Only Cobe C3s affected
• 9/21 (43) showed evidence of biofilm formation.
• 6/21 (29) were found to have sever biofilm build
  up around the de-aeration chamber.

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Audit Image 1
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Audit Image 2
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Audit Image 3
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Response to the Audit
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Removing Biofilm

• Chemical cleaning
• Mechanical cleaning
• Replacement of heavily contaminated parts
• Bacterial sampling of cleaned machines

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Investigation

• Major water contamination
• Inadequate disinfection routines
• Inadequate maintenance

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Investigation

• Major water contamination
• Inadequate disinfection routines
• Inadequate maintenance

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Water Analysis
The European Pharmacopoeia sets a limit of 100
cfu/ml
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Investigation

• Major water contamination
• Inadequate disinfection routines
• Inadequate maintenance

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Review of Disinfection Policy

• All Cobe machines left in chemical dwell when not
  in use. Excellent compliance by nursing and ATO
  staff.
• The brand of peracetic acid/hydrogen peroxide
  used had been changed 6 months previously.

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Cobe C3 Flow Path
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Residual Peroxide Levels
High Medium Low
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Investigation

• Major water contamination
• Inadequate disinfection routines
• Inadequate maintenance

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Service History

• Planned maintenance was slightly behind schedule.
• There was no correlation between last service
  dates and the level of contamination.
• One badly effected machine had been serviced 3
  months before.

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Investigation

• Major water contamination
• Inadequate disinfection routines
• Inadequate maintenance

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Re-occurrence?

• During the next month a follow up check was done
  on all machines
• Fluid from a previously contaminated machine
  showed 39 cfu/ml and 0.01 EU/ml endotoxin count.
• There was no re-occurrence it was a problem
  that came and went

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The Vital Evidence
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Other Factors
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The Cat in the Hat Comes Back
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The Cat in the Hat Comes Back
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A Tidemark?
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A Tidemark?

• Machines hadnt been properly disinfected in the
  early part of their use
• The biofilm was found at the top of the chamber.
• Stronger disinfectant had been introduced
• Once cleaned away it never reappeared.

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Conclusions

• The evidence points to a historical build up of
  low-level biofilm.
• This was dislodged from its location by the more
  aggressive disinfectant
• It settled at the top of the de-aeration chamber
  when the dwell phase started
• What was found in January was a tidemark.

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Recommendations

• Technical departments must always be vigilant
• Any changes, even improvements, to disinfection
  routines should be closely monitored

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References

• Should ultrapure dialysate be mandatory
• G Lonnemann NDT(2000)15 supp 1 5559
• Biofilms invade nephrology G. Cappelli B.
  Purif 200018224-230
• Water quality in hemodialysis FMC ISBN
  3-933151-39-2
• Microbiologic purity of dialysate B Canaud B.
  Purif 200018200-214
• The cat in the hat comes back - Dr Seuss
• Email gareth.murcutt_at_royalfree.nhs.uk