Can anything be used as an antibiotic if it is trying to destroy the right thing?

Question: Can anything be used as an antibiotic if it is trying to destroy the right thing?
- Keywords:
  disease,
  medicine,
  treatment
Asked by Shrek. to Sally, Rob, Matt, Marikka on 19 Nov 2014.
- Marikka Beecroft answered on 19 Nov 2014:
  
  The term antibiotic actually means something that can kill micro-organisms this covers a huge range of living things. Doctors use the term antibiotics so they don’t have to keep using different words for slightly different things and confuse patients. I suppose anything that can kill a micro-organism that’s detrimental to health could be called antibiotic!
- Robert Hampson answered on 19 Nov 2014:
  
  Any thing that kills bacteria or stops them multiplying that does not harm humans could theoretically be used as an antibiotic. There are some other concerns too, for example, if you need two kilograms of the stuff for it to work it will never become a medicine. Normally commercially available antibiotics kill bacteria when there is about a millionth of a gram of the antibiotic per millilitre of liquid.

Question: Can anything be used as an antibiotic if it is trying to destroy the right thing?