Complete the paragraph by choosing the words given in the bracket :
(Pathogen, broad spectrum, bacteria, Medicine, antibiotics, fungi)
Carbon compounds obtained from some bacteria and ......... for destroying or preventing the growth of harmful micro-organisms are called '...........' Antibiotics, a discovery of the 20th century, have brought about a revolution in the field of... Antibiotics mainly act against .......... Some antibiotics are useful against a wide variety of bacteria. They are called ......... antibiotics. They are used when the ......... cannot be identified.