Cat digestive system

Question
I obtained a cat from a shelter in July.  Immediately he began experiencing diarrhea and gas. He was negative on feline leukemia but his stool showed large amounts of bacteria; two prescriptions of antibiotics did not help. I learned he is an "outdoor" cat so likely his diet is not ideal; his outdoor time is now very little. Is there any cat food that would be better for his condition? Any other suggestions?

Answer
I would recommend trying an all natural diet that is free of preservatives, dyes, by-products, soy and corn.  I am in the process of switching my cats to a food called PRAIRIE by Nature's Variety www.naturesvariety.com ...they really seem to like it and it is an awesome food.  I would consider trying that food.  In addition, giving plain yogurt will help repopulate good bacteria in his intestinal tract.  And I would recommend adding digestive enzymes to his food.  I use Dancing Paws Shake "N Zyme www.dancingpaws.com for my cat who has inflammatory bowel disease.