Query for those using mikrocount dipslides (a schulke product)

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Query for those using mikrocount dipslides (a schulke product)

Posted by mikethair on August 9, 2019 at 12:49 am

I have had some contadictory advice on a set of mikrocount dipslide results.

The evaluation tables for mikrocount total plate count bacteria are shown below:

For the two samples using mikrocount dipslides out results came back as ND (no colonies detected). These are samples from two different water sources used in our cosmetics manufacturing. The dipslideswere cultured @ 30 C for 48 hours.

Samples of the same water sent to a commercial laboratory came back with the following results for Heterotrophic Plate Count @35°C for 48 hours :

Sample # 1: 1.4 x 10 (to the power 5) cfu/mL (sorry, cannot display the 5 superscript here).

Sample # 2: 2: 5.0 x 10 (to the power 4) cfu/mL

Any opinions on these sets of results?

Thanks.

Doreen replied 4 years, 9 months ago 4 Members · 8 Replies
8 Replies

ozgirl

Member
August 9, 2019 at 2:52 am

Check the use by date on your Microcount dipslides. They have a very short shelf life (<12 months).

Maybe try testing some water/sample that you know is contaminated by bacteria to check if you can get any response from the dipslides.

You could also try contacting Schulke as they have a microbiology lab and they might be able to test your water samples there as well.
mikethair

Member
August 9, 2019 at 6:06 am

Thanks @ozgirl All suggestions done, and all checked out. The sample results quoted in my post are from an SGS lab.

I need to work through the distributor of Microcount dipslides here in Malaysia. Who then contact the Schulke technical people in China. The answer that came back was:

In general I think the findings are comparable and reasonable as mikrocount duo is semi-quantitative and fast. The minimum determination limit is ~10^2 cfu /ml level. That means the SGS result 350cfu/ml is also in this minimum range.
The result is very related to the sample amount to the agar, that’s why for water testing the minimum determination is higher that high viscosity products such as solid/creams, which can be sampled more to the agar surface.

Didn’t make a lot of sense to me, given the external lab results.

Our QC Manager took the water samples for the Microcount dipslides plus SGS lab at the same time. So that eliminates a few variables.

If I am reading the results correctly, the SGS lab results are well above the ND result from the Microcount dipslides. Others (include he Schulke technical people in China) have said differently. Therefore, I’m now asking here.
EVchem

Member
August 9, 2019 at 11:23 am

We used to use duo and we got some false negatives- do you have access to the mikrocount combi. Would the lab be using the same kind of agar/media as the mikrocount? Different media could be a variable here right?

Can the lab perform any identity testing
Doreen

Member
August 9, 2019 at 3:16 pm

ozgirl said:

Check the use by date on your Microcount dipslides. They have a very short shelf life (<12 months).

And usually even way shorter!
We had so often growth on unused plates that were still in unopened package (and still had a good expiry date!) the decision followed to use double sterilized plates (those that are also sterilized in its secundary package) instead. More pricey, but problem solved! And to imagine that the primary packages of the plates were only opened in class B cleanrooms…
(Ok, these are a different brand and are plates instead of dipslides, but the medium and use are the same)
mikethair

Member
August 12, 2019 at 8:45 am

EVchem said:

do you have access to the mikrocount combi.

What would be the point of switching to mikrocount combi?

Thanks
mikethair

Member
August 12, 2019 at 8:47 am

Doreen said:

the decision followed to use double sterilized plates (those that are also sterilized in its secundary package) instead. More pricey, but problem solved!
(Ok, these are a different brand and are plates instead of dipslides, but the medium and use are the same)

What brand and product are you referring to?

Thanks
EVchem

Member
August 12, 2019 at 11:59 am

@mikethair they are slightly different compositions and pH- it’s also what Schulke recommended to us when we mentioned the false negatives we saw on duo
Doreen

Member
August 13, 2019 at 8:39 am

@mikethair
The brand is Tritium (select English flag right above for site translation) and the type I was referring to in particular were rodac plates with TSA.