Need help with digestive microbiology!

Could someone point me toward a specialist who actually focuses on digestive microbiology? I’ve consulted several gastroenterologists, but I'm not getting any real substance from them. They don't seem interested in diving into the granular details of gut flora balance, and frankly, even the nutritionists I've spoken with lack that specific depth.
I am looking for an expert capable of providing precise data—someone who can identify exactly which bacterial strains are deficient and explain the underlying reasons why my body reacts negatively to certain foods.