The invention of antibiotics has proved to be a boon a boon to society. The credit of invention goes to Sir Alexander Fleming whose careful observations in 1928 resulted in the invention of antibiotics. Antibiotics are chemical substances produced by various species of micro-organisms and other living systems, which are capable in small concentrations of inhibiting the growth of or killing bacteria and other micro-organisms. These organisms can be bacteria, viruses, fungi, or animals called protozoa.