I have been using a waterpik unit that i discovered has a pink mold (serratia marcescens?) in the tubing , concerned that i may get a blood infection from using this "infected water" around my gums.

Stop immediately: I would not recommend using any instrument that is infected as you could introduce the organisms into your system.

Listerine: If you run some original listerine thru the irrigator first there should not be a problem. That stuff kills everything.

Throw it out!: It is very hard to be sure the tubing is cleaned out properly. Best to discard the unit and buy a new one. You could try to contact the company to see if you can easily purchase and install new tubing. An excellent water pik is under $60. I would feel more comfortable with a new unit since you do not know what else has been contaminated. Be sure to change your tips every 3-4 months!