OK, so we started this experiment two weeks ago. The experiment was to last one week. I used packaged sliced bread. Two weeks later the bread has not changed at all - just shows how many preservatives are in that type of bread!! So we restarted a week ago with freshly baked bread and we have seen changes, gross changes!
By day 4 there was quite a bit of growth on the plain bread and also the antibiotic bread but not where the antibiotic cream was. The toast was still as it was when it started. After a week only the toast shows no growth and remains the same in appearance but feels drier than when we started. I think we'll keep observing until the weekend and then into the garbage they will go. It has been interesting and both kids are surprised that the toasted bread had zero mould growth.