There can be several causes for an elevated PSA. Prostatitis, cancer, an enlarged prostate, or even a simple digital rectal exam are all possibilities.
The fact that the PSA decreased so dramatically after a course of antibiotics, suggests prostatitis. However, to be sure, you may want to be evaluated by a urologist to see if biopsies are need to definitively rule out cancer.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
http://www.straightfromthedoc.com