Bacteria such as Staphyloccoccus aureus are constantly evolving, which is why methicillin-resistent Staphylococcus aureus (MRSA) exists in the first place. A new strain occurs when an existing bacterial strain undergoes a mutation. New strains of pathogens may develop new antibiotic resistances, become more or less virulent or infect new host species. In the case of a MRSA strain that was discovered by researchers in June 2011, the strain is…