The discovery of Penicillin in 1928 led to one of the biggest advancements in modern medicine: antibiotics to treat bacterial infections. Subsequently, numerous different types of antibiotics developed. Many diseases were cured, and this type of medicine was responsible for saving many lives. Antibiotics are one of the cornerstones of modern medicine. But that could all change.
Bacteria have the ability to develop resistance to antibiotics. Think of it as an arms race. We develop a new weapon against the enemy. They respond by developing a defense. We improve our weapons to overcome their defense, but then they develop new defenses. The problem is that we are losing the arms race. An our enemy is a mere single-celled creature.
Recently, a new bacterial strain was found to be resistant to all of our best antibiotics. New E. coli strain resistant to all known antibiotics. Once some bacteria develop resistance to any antibiotic, they can pass on those genes to other bacteria. They literally send out a loop of dna, which the surrounding bacteria incorporate into their cell. Antibiotic resistance spreads rapidly between bacteria.
Some researchers blame excessive use of antibiotics in livestock for the rapid development of resistance to antibiotics. This resistance then spreads to bacteria which infect humans. The result is diseases that are very difficult to treat, because the bacteria are resistant to many different antibiotics. Development of new antibiotics is moving at too slow a pace to keep up with the spread of resistant bacteria.
Worst case scenario: a bacterial disease outbreak that cannot be treated or cured with antibiotics. It would be as if medicine were thrown back to the early 20th century. We would be starting from square one again.