I think i have a uti from protected sex without spermicide. the doctors sent my urine off for a culture to detect what type of bacteria was in my urine. can the doctor tell from the bacteria in my urine if my uti is from sex?

Sometimes STDs can mimic UTI, especially gonorrhea or chlamydia. When sex triggers true UTI, it's because entirely normal bacteria in and around the vaginal opening are massaged into the urethra. Therefore, with a typical UTI bacteria (like E. coli, Klebsiella, Proteus and others), there is no way to know whether sex triggered it. But it doesn't matter: if triggered by sex, partner Rx not needed.

Sex does not cause UTI- Micro-organisms do. Your presumption about 'protected spermicide etc.' is wrong . Sex can sometimes irritate the bladder and cause symptoms similar to UTI ( frequency, burning, pain) . No your doc can not tell whether it is from sex or not by a urine test.