It is not mandatory, nor necessary to use antibiotics during a medical abortion. Remember the risk of getting an infection is very low (less than 1%) , and most women do not have an infection after the procedure.
If you have signs or symptoms of infection after the abortion (new odorous or colored vaginal discharge with fevers, chills, pelvic pain, nause, vomiting), you should seek medical evaluation. If an infection is confimed, a medical doctor will prescribe you the necessary antibiotics. It is not advised to use antibiotics unless they are prescribed to you.
 Ipas. (2019). Clinical Updates in Reproductive Health. L. Castleman & N. Kapp (Eds.). Chapel Hill, NC: Ipas. Retrieved from: https://ipas.azureedge.net/files/CURHE19-april-ClinicalUpdatesInReproductiveHealth.pdf