I would imagine that the lack of any kind of food source for bacteria, freezing cold temperatures, and space radiation should be enough to sanitize the vehicle from anything from earth. We're not talking about organisms that thrive at the depths of the ocean or tardigrades (although I'm sure someone will bring them up). We're talking about molds and bacterias that grow in warm, damp places like car seats and dirty human crevices. I would be surprised if they lasted out there and would be giddy if it survived long enough to grow further. That's an experiment, right there.