Many people struggle with recurring bacterial infections - taking antibiotics seems to suppress the bacterial infection (for example, in a urinary tract infection or UTI), but the infection soon comes back. And so the cycle continues - infection, then antibiotics, then infection, more antibiotics, and so on.
Thus it was with interest that I read about a recent study that found that some pathogenic bacteria grow slowly and enter a dormant-like state (hibernation) when exposed to antibiotics so the antibiotics don't affect them (they're "persisters"). This is because antibiotics typically target a bacterial cell's ability to grow (and so do not have an effect on bacteria in a dormant phase). Then the bacteria resume normal growth and spread when the antibiotics are gone. This study was done in cell cultures in the lab using Escherichia coli bacteria from UTIs. Future research may look for drugs to target bacteria in the dormant state. From Science Daily:
University of Copenhagen researchers have discovered a surprising tactic of pathogenic bacteria when being attacked by antibiotics: hibernation.
Almost all pathogenic bacteria develop a small number of antibiotic-tolerant variants. This means that a significant fraction of bacteria survive courses of antibiotics.While it is no secret that pathogenic bacteria are able to develop antibiotic resistant variants, a less well-appreciated fact is that a small number of bacteria, including some of nature's nastiest pathogens, can resist antibiotics and escape antibiotic treatments without relying on variants.
How's that? Researchers at the University of Copenhagen now have an answer. They have found examples of a small portion of pathogenic bacteria hiding out in a dormant, hibernation-like state, until the danger posed to them by antibiotics passes. When safe, they awaken and resume their regular functions.
"We studied E. coli bacteria from urinary tract infections that had been treated with antibiotics and were supposedly under control. In time, the bacteria re-awoke and began to spread once again," explains Professor Kenn Gerdes of the University of Copenhagen's Department of Biology..
Antibiotics usually target a bacteria cell's ability to grow, which means that a hibernating bacterium is exempt from attack. "A bacterium in hibernation is not resistant. It is temporarily tolerant because it stops growing, which allows it to survive the effects of an antibiotic," says Professor Gerdes.
The researchers used a new method to study what happens in the disease-causing cells that go dormant and hide in the body. The researchers found an enzyme in dormant bacteria that is responsible for catalyzing hibernation, which allows the bacteria to avoid being attacked. "The discovery of this enzyme is a good foundation for the future development of a substance capable of combating dormant bacteria cells," says Professor Gerdes.
Electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is a rounded cylinder. Credit: Wikipedia