Antibiotics are produced to fight prokaryotic cells and their characteristic features (such as their particular ribosomes). Fungi, in contrast, are eukaryotes with distinct features which are unaffected by antibiotics or minimally effective.
Work Step by Step
Look at what antibiotics usually are effective against (prokaryotes) and try to find contrasts with fungi. The most obvious comparisons are based in the fact that fungi are eukaryotes, not prokaryotes.