Got it, I wanted to work out whether there were details like the kind of antibiotic that needed consideration.
Part of the reason you may be finding mixed answers about this is that only certain kinds of antibiotics can decrease the effectiveness of the pill. You can learn more about that here: Something You Can Worry About Less: Interference and Hormonal Birth Control
. Too, if your healthcare provider decided to proscribe that type of antibiotic, they'd ask about any other medications you're on and talk with you about reducing pregnancy risks while on the antibiotics.
In looking through different reputable resources, I don't see the recommendation to take emergency contraception if you had vaginal sex a few days prior to going on to antibiotics. A big reason for that may be that emergency contraception, like Plan B, can also have their effectiveness decreased by those types of antibiotics: https://ec.princeton.edu/questions/ecdilantin.html