Could Antibiotics Affect The Efficacy Of Anti-depressants?

Hi - I was prescribed 15 capsules of Amoxycillin by my dentist after dental work. However I have been on Fluoxetine for the past 6 months - I didn't really want to mention this to my dentist when she prescribed me the antibiotic. Anyway, I've finished the course of antibiotics now, but feel as if my anti-depressants have not been working at all the past week. Could antibiotics affect the efficacy of anti-depressants, or is this just coincidental? Thanks.