Microorganisms are minute living things that individually are too small to be seen with the unaided eyes (Tortora et al, 2007).  Though only a minority of microorganisms are pathogenic (disease producing), practical knowledge of microbes is necessary for medicine and related health sciences.  For example hospital workers must be able to protect patients from common microbes that are normally harmless but pose a threat to the sick and injured.  Thousands of people died in devastating epidemics; the cause of which was not understood.  Entire families died because vaccination and antibiotics were not available to fight infection (Johnson and Case, 1995).  This leads to scientific control of microbial growth.  This began only about 100 years ago.  It was Pasteur’s work on microorganism that led scientists to believe that microbes were a possible cause of diseases and need to be eliminated or destroyed.  Some examples off these microbes are; Bacteria, fungi, viruses and protozoa etc (Tortora et al, 2007).