There's not a whole lot of micro in the small intestine due to gastric pH-but here's a sampling:
E. coli, Bacteroides, Lactobacillus, Strep, possible Enterococcus, Vibrio (if you're unlucky and have cholera), bifidiobacterium, Clostridium?
Candida albicans is the only yeast that comes to mind, unless you really got into somethign bad.
Enjoy...