Infection from a razor??? Do you know if your friend is using a DE? I honestly can't say that I have ever heard of this happening.
After each shave, I spray my razor down with some 70% iso alcohol. This probably kills off bacteria, but my motivation to do it is more about reducing soap scum build up and making sure the razor dries quickly.
Razors don't shave people. People shave people!
There are three critical types of moments in life: Times when we should be enamoured of the finer details, and times we should ignore the minutia.