While
 antibiotics have saved countless lives that would have been lost due to
 infection, they are a double-edged sword.  Antibiotics are prescribed 
to kill a particular pathogen, for instance, one causing strep throat. 
 Sometimes, these antibiotics are targeted to a particular pathogen, 
often called Gram negative or Gram positive, but more often 
broad-spectrum antibiotics are prescribed to hasten the healing process.
  
Antibiotic-associated diarrhea[41] is
 often the result of antibiotic use and directly caused by altering the 
gut flora.  When the gut flora is altered, as it is with a round of 
antibiotics, pathogens are allowed to grow out of control and biofilms 
develop that protect these pathogens.