Colitis and Antibiotics

Is there any way of determining whether or not colitis has been caused from poor circulation or the result of a one-time 2000MG dose of Amoxicilin? What is the likelihood of prophylactic benefit versus the adverse effects of taking the antibiotic for prophylactic reasons?

My related recent experience includes:

Day One I had 2000 MG Amoxicillan as a prophylactic for a routine dental examination. Day two I had severe diarrhea twice and vomited once. Day three, at about 4:00 p.m., I began bright red bleeding from my rectum and did so in the amount of two to three ounces every two hours until about midnight. Shortly after midnight, on day four, I was admitted to the hospital. I had a colonoscopy on day five which found no malignancy and supported a diognosis of ischemic colitis. The causation given was temporary poor circulation to the colon. Day five I returned home with a prescription for Cephalexin 500 MG for Keflex. Day six my right foot became too swollen to walk properly and resulted in excrusiating pain. I returned for urgent care and was given a pain killer and was diagnosed with cellulitis on my right foot.