Those sound like round worms. They're very common.
Whether or not he's been dewormed, what you'll need to do are keep the litter boxes VERY clean. Scoop as often as you can. Once a week, dump the litter and bleach the boxes. Put new litter in them. It's expensive - but it helps prevent other kitties from getting round worm from him - and if he's by himself, it helps prevent him from getting reinfested with the worms.
Round worm is usually pretty treatable. Our old vet used to give us Drontal for it. That is a pill and easy to give. Some round worm, however, are not killed by Drontal. We ended up having to use Panacur (a liquid) to get rid of the round worms.
About three weeks after you've given kitty the second dose of whatever de-wormer is used (if he's already received one deworming, he'll need another about three weeks from whenever the first one was given), if you can have your mom get a stool sample to a vet, the vet can look in the microscope and see if the worms are actually gone.
Poor Bing is probably not feeling so well after the surgery, and the worms and maybe after-effects of the anesthesia are making him vomit.
Maybe they're just giving him the antibiotics to prevent any potential infection. It's something you'd have to ask - why he's on antibiotics now.
I'm sure he'll feel a lot better tomorrow - especially if he was dewormed. It is poison after all. And if he wasn't de-wormed, he does need to be, poor baby.
Bing is such a cute name!