Antibiotic Resistance

Antibiotics have been a critical public health tool since the discovery of penicillin in 1928, saving the lives of millions of people around the world.  Today, however, the emergence of antibiotic resistance in bacteria is reversing the advances of the past eighty years.   Many classes of antibiotics that worked well previously have been rendered ineffective and the treatment of many bacterial infections now requires a hospital admission and treatment with one or more intravenous drugs.  These antibiotics used to treat drug-resistant infections often have longer treatment durations or are older products with higher rates of side effects.  The Centers for Disease Control and Prevention (CDC) estimates that drug-resistant bacteria cause two million illnesses and approximately 23,000 deaths each year in the United States alone.

What causes antibiotic resistance? Some resistance happens naturally, due to underlying biology.  The rapid replication rates of bacteria results in high turnover, and they are able to quickly evolve past a problem they encounter, such as a drug that is trying to kill them.  The microbes that mutate and develop resistance to a drug will be the ones that survive and go on to proliferate the most. 

But some human behaviors and practices have helped these microbes evolve faster than they otherwise may have:

  • Overuse of antibiotics – while antibiotics are used to treat bacterial infections, they are not effective against viral infections like the common cold, sore throats, and the flu. Overprescribing of antibiotics for disease states where they are not effective has helped fuel antibiotic resistance
  • Misuse of antibiotics - If people stop taking antibiotics after a few days because they feel better, the bacteria-fighting medicine kills some of the bacteria, but stronger ones can survive.
  • Usage in animal feed – the majority of antibiotic usage in the world is used in animal feed to promote weight gain. The resistant bacteria that develop in antibiotic fed livestock can be transferred to the general human population via food.

There are many mechanisms of bacterial resistance.  Some resistance mechanisms are broad and affect several antibiotics, while others are found only in specific classes of antibiotics.  For the tetracycline class of antibiotics, there are two main mechanisms of resistance: pump efflux and ribosomal protection.  

  • Efflux-mediated resistance enables bacteria to utilize efflux pumps to actively pump out the antibiotic from the cell.
  • Ribosomal protection is a way that bacteria can protect the intracellular ribosome which creates proteins required for the bacteria to live. Drug resistant bacteria have developed the capacity to produce proteins which preferentially bind to the 30S subunit of the ribosome and block tetracyclines from binding to the 30S subunit, so the pathogen continues to survive and can spread.