The shortest interval from exposure to a sexually transmitted disease to symptoms of that infection is 1-2 days, but very few (Herpes, Gonorrhea) have that ability. The majority of STDs (eg: Chlamydia, Trichomonas, Syphilis, HIV, Hepatitis B) don’t manifest for 1-4 weeks. That means after a potential exposure cultures are unlikely to reveal an infection for (at least) 2-3 weeks) and should be repeated 1-2 months later because some of these STDs (eg: Syphilis, HIV) may not be detectable for that amount of time.