Answer:
Bacteria are highly adaptable microorganisms who have the capability of developing defense mechanisms against that which may harm them. Not least important of all, is the easiness with which some bacteria, especially pathogenic bacteria like Salmonella, or Klebsiella, develop mechanisms of resistance to antiseptics and, most importantly, antibiotics.
Antibiotics are a chemical substance that was created, and has been developed, in order to be able to combat pathogenic microorganisms, specifically bacteria. However, because today these substances are being used indiscriminately, we are now seeing a very worrying pattern of antibiotic-resistance patterns in microorganisms that used to be sensible to them. The result, we are facing strains of pathogenic bacteria, like Klebsiella pneumonia and E. Coli, that have become resistan to all types of antibiotics, from first generation, to fourth generation. And this has meant that when people acquire infection by these pathogens, the likelihood of death by them has increased because there are no agents capable of combating them.
Exposure to antibiotics has been the sole reason why these resistant strains of bacteria have emerged, especially when these antibiotics are not necessary. And feeding these substances to animals, to ensure their development and weight gain, has not made the situation any better. Now, we are instead adding also bacteria to the list that did not use to be resistant, but that are becoming so as they become adjusted to the constant exposure to antibiotics. Again, the result has been: more people infected with bacterial strains that cannot be combated with any of the existing antibiotic agents.