A Patient with Recurrent Bacterial Pneumonia Is Treated with an Antibiotic

A patient with recurrent bacterial pneumonia is treated with an antibiotic that has worked previously but is not working to reduce symptoms in a current infection. The nurse caring for this patient understands that this is likely for which reason?

A) The antibiotic altered the genetic makeup of the bacterial strain causing this infection.
B) The antibiotic caused host cells to change and become more susceptible to bacterial effects.
C) The antibiotic caused a mutation of the organism leading to reduced drug sensitivity.
D) The antibiotic destroyed competing organisms that secrete substances toxic to the pathogen.