The water bottle

OK, I need your advice.

I started bringing a water bottle to work, because I believe wholeheartedly in the amazing power of WATER.  So I like to drink a lot of it during the day.  I rinse it out every day and wash it with soap twice a week.

However, a week ago, while I was drinking from the water bottle when I noticed there was some black crud in the drinking straw.  This inspired me to grab some cotton-tipped applicators from the supply closet and clean out the straw.  The cotton came away BLACK.  I used six of them, then washed again with soap, and then christened the water bottle as clean.

But when recounting this story to a coworker, they said I should have thrown it out and bought a new one.  That no matter how much I cleaned, it was not clean.  But to be fair, this coworker spends about ten minutes wiping down her work station every morning. (I'm not saying she's wrong to do that, but that's a level of disinfection I don't embrace.)

What do you think?  Can I still use my water bottle?  Is there a way to prevent this from happening again besides the cotton tips?

Have you ever done this before

This amazing cartoon was drawn by my daughter, who is only TWELVE!  Clearly, she is way more talented than her mom.