Worst smell ever

This one year old neutered "TOM" weighing in at 15 lbs has the worst smelling poops ever!  No worms, no giardia, not malnurished (nor is he obese, just big). The probiotic FortiFlora suggested by the VET has not helped.  I have had Seven cats in my life and this issue is my first.  Any suggestions other then room freshener is appreciated.

Well, the smell certainly indicates something is off. What's he being fed? It seems his food doesn't agree with him.

You might want to try a human grade acidophilus+bifidus supplement. If you're in the U.S., many on this site use Natural Factors double-strength acidophilus+bifidus with goat milk. It is 10 billion CFU. I buy it from amazon, though a local health food store carries it. I'd start by giving him 1/2 a capsule 2x a day, but you may need to bump it up to a full capsule a day. We had a similar issue with one of our rescue cats - actually, he also had diarrhea, and the Fortiflora made it worse.

I concur with Laurie.  I think a decent probiotic and change in foods will fix him right up.  It's amazing, but my little girl had the WORST smelling poop one day, and I realized I had given her some canned food with grains in it for the first time in over a year and a half.  That was all it took.  One little 3 oz can and ooooh weeeee