There are two things that may help.

1) Kefir--- This has tremendous numbers of 12 cultures, and I used it myself and still am since Sept. It took 3 days to reverse my GI agony. Lifeway is available now in most stores. My Kroger's has it in several forms. Gluten free too!
http://www.lifeway.net/
Far superior to yogurt which typically have 3-6 varieties of cultures.

2) Metamucil will help with chronic diarrhea also. I use the capsules, but it doesn't really matter. This recommendation came from a GI specialist I went to years ago... and it works very well. When the psyllium seed swells up in the bowel, it acts as an adsorbent and sponges up whatever nasties are there
and allows you to get rid of them manually.

Next time ask for Zithromax. This is usually very easy to tolerate.

I would space the kefir around the Metamucil, so the good bacteria have a chance to work their magic.