There are plenty of ID folks who do basic science research without a PhD. If you are not planning on seeing pt's at all, the PhD may be helpful as you will be competing with MD/PhD's for grants. Many of the people I work with in my ID division who do basic science research without a PhD also do some clinical work, ie. attend on the wards for 4 weeks or so per year.
If you want to do research, go to an academic program that expects/requires you to do three years. Programs are only "required" to be 2 years long. In those programs, you will do clinical work for 2 years. At academic programs, you will do one year of intensive clinical work followed by 2 years of research. You will still have some clinical duties such as a continuity clinic, but will be primarily focused on research. Find a program that guarantees your funding for all three years and does not require you to find a grant for your third year.
Hope that helps.