Mirror antibiotics must work in mirror bacteria. Mirror proteins should fold exactly like normal proteins, but mirrored. (There may be a problem with the weak force, but I never heard it's used in biology.)
Mirror symmetry breaks down in counter-intuitive ways in physics, that probably bubbles up into the chemistry side of things too. Not always, and not often. Probably just often enough to be confusing, and in this case, starkly terrifying and spirit-crushing.
