PC2K,
Cool, Thanks for translating you did very well; I wish I could speak dutch so you are one up on me.

I would not be too worried. When I worked at a local REI we would get customers who would return a filter/purifier with all kinds of mold in it. They obviously did not dry out the cartridge after use which is necessary.
Boiling the MSR filter will work but air drying will kill the bacteria too. I would not worry about the bacteria while in the field for a short to meduim-long trips. I bet it would be fine plus in most wilderness it is not bacteria as much as protozoans you need to worry about.