Hi, maybe some of the water people can help:
what is the recommennded bacterial culture incubation period / temp / media? Thank you!

If I remember correctly....

Media - TSA
Temp - 37.0 C
Time - 48 hrs
Must NOT use a calibrated loop.

Chuck

Correct.

Thank you - what is your opinion about the European Best Practise for ultra pure water??
Media: TGEA
Temp: 20 0 C
Time: 7 days
Please advise as we are changing to pure water.

From what I understand the European method is much more accurate but the incubation time of 7 days makes it a little impractical.

The European method is mentioned in the ISO guidelines. It will result in a different cfu/ml value. Sometimes it will be higher, and sometimes it will be lower. Although, ISO 13959 says "Extending the culturing time up to 168 h and using a lower incubation temperature have also been shown to increase the recovery of bacteria compared to incubation for 48 h at 35 °C as recommended in ANSI/AAMI RD52."

Also, keep in mind that the ISO guidelines have a bacteria limit of 100 cfu/ml with an action level of 50. And, endotoxin limit of 0.25 EU/ml with an action level of 0.125.

One more thought, the current method using TSA is to count the colonies after 48 hours (before 72 hours). If you get a result that has no counts (<2cfu/ml), I would suggest asking the lab to count it after 7 days, to see if anything grows. The valid number is still the one counted between 48 and 72 hours. But, also counting at 7 days may show there is something that you did not know about. There is always bacteria in the water. You don't need to do it to every sample; just one sample (end of loop) every so often (few times per year).

Just a thought.