A new study by researchers at the University of Exeter has thrown more light on how viruses can be used in tandem with antibiotics to more potently combat bacteria while guarding against resistance issues.
Antibiotics ranked among the most notable medical inventions of the 20th Century. They helped greatly in saving the lives of millions of people by boosting their immune system’s ability to combat bacterial infections.
But medical experts have noted with dismay a rising incidence of antibiotic resistance by bacteria. It is becoming harder to deal with these microbes using antibiotics. Bacteria responsible for gonorrhea, tuberculosis, salmonellosis, and pneumonia are among those known to show resistance.
As a result, patients are spending longer time in hospitals while receiving treatment. Costs of treatment are rising and more people are dying due to this resistance problem.
Researchers are now closer to using viruses to kill tough bacteria and break their resistance to antibiotics. In this new study, the team throws more light on how to combine viruses (phage therapy) and antibiotics to great effects in fighting these organisms.
Findings from the new research appeared in the journal Cell Host Microbe.
The resurgence of phage therapy
Phage therapy is the name for the treatment that involves using viruses to fight bacteria. Viruses that are harmless to humans are used to infect bacterial cells and so destroy them.
The idea of fighting bacteria with the aid of viruses has been around for over a century. A French microbiologist was reported as the first to give phage therapy to treat a young boy that was suffering from severe dysentery.
The discovery and use of antibiotics would lead to a decline in the interest to use viruses to fight bacteria.
However, now that more and more bacteria are starting to show resistance to antibiotics, researchers are exploring other treatments. These include the use of viruses. Interest in phage therapy is rising once again.
This alternative treatment is not without its challenge, though. Just as they can build resistance to antibiotics, bacteria can also do the same to infecting viruses or phages. This problem is one that the new research sheds more light on how it can be overcome.
Breaking down resistance
Bacteria possess a CRISPR defense system, similar to that found in humans. This features proteins that help to get rid of invading bacteria. With each virus successfully killed, the system learns to identify and fight off the same in the future.
Researchers carried out experiments on Pseudomonas aeruginosa in the current study. They exposed the bacterium, which causes disease in patients with cystic fibrosis or weakened immune system, to eight antibiotic types. The team observed differences in how the microbes develop resistance to phages.
Of the eight antibiotics, four produced a significant rise in CRISPR-based immunity levels. These bacteriostatic agents do not destroy cells directly but instead aim to slow their growth.
The researchers found that bacteriostatic antibiotics cause CRISPR-Cas immunity to improve due to a slower rate of phage replication. They, therefore, concluded that speeding up the rate of phage replication could make bacteria’s CRISPR systems less able to guard against viruses.
“We found that by changing the type of antibiotics that are used in combination with phage, we can manipulate how bacteria evolve phage resistance, increasing the chances that treatment is effective,” said Professor Edze Westra.
Apart from CRISPR-Cas immunity, bacteria also protect themselves by altering their cell surface to keep phages from sticking. This also reduces their ability to cause diseases, however.