please reinstall all your themes and plugins. most likely the maleware was inside one of your plugins and placed there at initial breach. since you have closed the door and removed the infection you should be good to reinstall all your plugins... again reinstall plugins form reserve. do not ftp a backup. backup may be infected also. reisntall your theme. check site and you should be clean and functioning at 100%
To avoid breach. always maintain updates for themes and plugins as well as the core.
I would also install wordfence for security.