I always make sure I'm particularly careful with diet after ABX, not that I've had them in years thankfully. I don't eat sugar because it feeds opportunistic bacteria which can create an imbalance in your flora. I would also try to include lots of homemade fermented foods, sauerkraut, kefir, yoghurt etc. You can buy these from the supermarket too, but many have been pasteurised to death. Live yoghurt is a good supermarket option. A good quality probiotic may help as well, VSL-3 is a well researched one. I would follow the tips herein and general tips to improve the gut flora, I'd just be particularly hot on them post ABX.