Hi, a few things to consider. Are your bacterial strains aerobic or anaerobic? How do you plan to administer the bacterial mixture? At what CFU/bacteria is your target bacterial concentration inoculation?
Maybe this journal can also be of help in planning your preparation. http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001637#pbio.1001637.s011