Multiple Drug-Resistant Staphylococcus aureus (MRSA) is a bacterium that has developed resistance to ...

Multiple Drug-Resistant Staphylococcus aureus (MRSA) is a bacterium that has developed resistance to a wide range of antibiotics.
 
  Its resistance to penicillin, methicilliin, and oxacillin is a result of the serial use of these antibi-otics, which created a selective environment that favored resistance to the drug being used at the time. This resistance provides this class of bacteria the ability to thrive while being treated with standard antibiotics, thereby making it a dangerous human health hazard. Why would one expect MRSA to retain penicillin resistance even if this antibiotic is rarely used?
 
  What will be an ideal response?