Ok, granted that male DNA will show up in any male cell why were they checking for male DNA. Any male contaminant DNA from her brother would have degraded to the point that PCR analysis would not have been able to detect it. Furthermore, DNA degrades very rapidly in a hot, moist environment ie. a toothbrush being run under hot water. This degradation is why it's crucial to get swabs for a post rape kit in the first 24 hours or so. If it wasn't semen, then whomever used Natalee's toothbrush that was male had to have access to her personal toiletries(my wife won't even let me look through her purse) in the last few hours that she was in the room. Of course maybe her roommate had a stay over friend that last night and could be why she's not saying much.
I think that the whole thing about male DNA is a ruse or falsehood to simply make Natalee look bad as I said in the last sentence of my previous post.
TAW