Flies in my bag of bread - bad bread?
Sometimes the presence of insects in certain foods cannot be avoided. The FDA has regulations on this, but I couldn't find any specific references to bread per se. However, based on standards for some other foods in there, two flies probably aren't a big issue.

At the same time, flies are well known for spreading bacteria harmful to humans all over the place, and if you're feeling squeamish about this, I would just throw out the bread. This may be true especially considering that you don't know how long the flies have been present with the bread, and that the bread has been sliced and thus exposes more surface area.