Interim microbiology results

[Garry]

Are any units using an interim count or different test to obtain an 'early warning' of ring return/RO contamination in addition to the standard R2A, 7 day, 17-23deg method?

We have tried a 5 day 100ml filtration test though currently the results will return a >100cfu/100ml for anything over 1cfu/ml which, though useful to gauge compliance for ultrapure quality, doesn't shed much light on if the sample meets the basic standard for water for dialysis.

If any other unit has had success in using another method as an early warning before the 7 day test is complete I'll see if I can request that from our labs

Thanks

[Ian Wilde]

Hi Garry,

Have you got further filtration on your machines?  If so that should give you the safety net to wait the 7 days for your result and also give you time to take any actions required - or have I just totally missed the point of your question?

[Garry]

Hi Ian,

We do not have filtration on all of our equipment though they are being replaced with such as they are life cycled.  Even with filtration our policy would be to advise against HDF treatments until corrective measures and a satisfactory sample had be completed.  

[Ian Wilde]

Hi Garry,

If the standards say:

Dialysis water containing a total viable microbial count of less than 100 CFU/ml and an endotoxin concentration of less than 0.25 EU/ml is also the starting point in the production of ultrapure dialysis fluid or for on line infusion fluid used in haemodiafiltration (HDF). The production of ultrapure dialysis fluid is generally achieved by the use of additional filters which form part of the dialysis machine hydraulic pathway. BS EN ISO 23500:2015 states there is no requirement to test for bacterial growth or endotoxins when the haemodialysis system is fitted with endotoxin retentive filters that are operated according to the manufacturer’s instructions, unless the manufacturer requires such tests to be performed

and that:

We recommend that the quality of water produced by the water treatment system shall meet the concentration limits for microbiological contaminants detailed in BS EN ISO 13959:2015. This states that dialysis water shall contain a total viable microbial count of less than 100 CFU/ml and an endotoxin concentration of less than 0.25 EU/ml. If routine monitoring demonstrates microbiological
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contaminant levels in excess of 50% of the maximum permitted levels (based on the analysis of historic data) a programme of corrective measures should be commenced immediately.

are you finding yourself outside of these figures?  I'm just trying to gauge whether you may be worrying unnecessarily?

[Garry]

Hi Ian,

Happy with the standards.  This query originates from us receiving a very poor result from the labs.  No previous trend or breach of action levels so most likely sampling or lab contamination.  It really was just to gauge if others use an additional  shorter 'non standard' test to give a heads up of an impending poor 7 day count.


Post endotoxin filters on equipment still give 0 counts, as expected, so no worries there

Regards

Garry

[Ian Wilde]

Ah right. Will be good to see if anyone has any other ideas or suggestions

[Garry]

I notice that the latest revision of iso 23500-3 2019 now includes use of Tryptic Soy Agar (TSA) as a recommended method of monitoring microbial burden in water used for conventional or standard dialysis.  With the only a 2 day incubation time have any other units moved to this method?

Slightly confused by the explanatory text that mentions a statistical difference between TGEA and TSA and then goes onto to state that working group will include as recommended method for indicating microbial burden in water and dialysis fluid.

Thoughts?

[Ian Wilde]

Hi Garry,

Not heard of that myself.  I'll gladly send an email to ALS for clarification as they are usually pretty responsive.
Any chance you can email an excerpt?

Cheers

[Chris Bates]

This is an old idea I think.

As I recall the TSA test is at 35 degrees so it is much more likely to grow organisms which like warmer, fluid circuit type, temperatures.

The TGEA is a nutrient poor medium which is tested at 20 degrees and is therefore more likely to find the organisms which thrive in low nutrient and low temperature water samples.

Not sure how nutrient rich TSA would be.

20 + years ago everyone switched to TGEA as it was thought to be a better test for the organisms actually likely to thrive in RO water.

I believe one version the ISO recommendations allowed the TSA test as an exception for the USA

[Garry]

I agree, similar discussions many, many years ago but this is the latest revision of the standard and TSA is now included in the list of recommended methods.

Yes, American led.  This may have been the paper that ISO considered before adding TSA to the recommended list.

I did speak to ALS and they can currently only perform 100ml filtration with TSA at 48 - 72hours.  The test is also not UKAS accredited so likely a non starter for now