If it really was infected, kill everything with fire. Don't try to propagate anything that came out of that fermenter. Clean everything and let it soak in hot sanitizer for a long time. Try to wash and reuse your next good batch.
Cleanliness is next to godliness, something like that. Anyway, clean kit means good beer, unless you're trying for lambics. Then you need to be a special kind of infected.
I reused yeast once, worked fine and was pretty easy. But I'm both a busy and lazy guy so I tend just to pitch fresh every time. If I ever brew something twice in a row I might just re-use the yeast cake, but I haven't done that yet.
