Index with suffixes (MD, DMD, DO)

I have an index of about 1600 names. I'm willing to go through and mark them individually with sort by last name, and this appears to be working, however, it ignores the suffix. I tried inserting non-breaking spaces between the name and MD but it didn't change anything. If it does somehow include the MD's, it lists them under M as MD separately. Does anyone have any idea how to include these?

Thanks.