Researchers from the Quadram Institute and the University of East Anglia have explored how resistance helped drive the emergence of dominant strains of salmonella. In addition to antimicrobial resistance, resistance to phages may give these insects a boost, at least in the short term.
With antimicrobial resistance on the rise, the search for new ways to combat disease-causing bacteria continues.
One line of inquiry is to look for bacteria’s natural enemy – viruses. There are more virus particles on Earth than there are stars in the universe, and some of them specialize in using bacteria to replicate themselves. These viruses, called phages, also kill their bacterial hosts, making them potential new allies in the fight against bacterial infections.
One of the leading causes of bacterial diseases globally salmonella bacteria. They are behind 78 million cases of illness each year and many of these are attributed to a closely related group salmonella that infect humans and animals; Enteric salmonella Typhimurium serovar, or s. Typhimurium for short.
salmonella Typhimurium’s success is due to its genetic flexibility, which allows it to adapt and overcome resistance. This has led to waves of related strains prevailing for 10 to 15 years but then being replaced by new strains. These new strains may show better resistance to efforts to control them, making it difficult to design new interventions such as trying to hit a moving target.
Professor Rob Kingsley of the Quadram Institute and the University of East Anglia and his team supported the fight effort salmonella By studying its genome to find evidence of its adaptability, and how changes in the genetic code gave the breeds a competitive advantage. A 2021 study revealed, for example, how salmonella Carves a niche in pork production.
In a new study recently published in the journal Microbial GenomicsThey have now looked at the effect of bacteriophage resistance on populations dispersed in salmonella, How did this relationship between predator and prey evolve? The research was funded by the Biotechnology and Biological Sciences Research Council, part of Research and Innovation UK.
This is a complex relationship—while phages prey on bacteria, they can also promote the spread of genetic material across strains. That’s because the spread of genetic divergence and the transfer of resistance genes between bacterial populations can be mediated by phages – a process known as phage-mediated transduction.
“There is renewed interest in using phages as an alternative or as an adjunct to antibiotic therapy for bacterial infections, and like antibiotics, the key to understanding the potential emergence of resistance to phage therapy lies in how resistance emerges in nature.said Professor Rob Kingsley.
Working with the UK Health Security Agency (UKHSA) and the Animal and Plant Health Agency (APHA), the scientists examined whole-genome sequences of strains collected from human and animal infections over the past several decades.
They find that strains salmonella They are best adapted to living in livestock, so those most likely to cause disease in humans tend to be more resistant to phages. The resistance of the phages appears to help the bacteria invade new environmental niches
The current dominant strain, ST34, in addition to being resistant to several drugs, also shows higher resistance to attack by phages than its predecessors. This appears to be because they acquired the phage’s genetic material into their genome – a move that increased their resistance to phage attack.
But this leads to an interesting situation, in that resistance to phages means that these bacteria are less likely to acquire new genetic material, including resistance genes, through phage-mediated transduction. So could short-term gains in bacteriostatic resistance lead to long-term consequences that make bacteria unable to adapt to changes in their environment such as societal interventions, even new antimicrobial therapies? Monitoring data suggests that this opens the door for another clone to take its place.
Whatever the situation, what is clear is that genetic monitoring of these bacteria, and their phages, is essential to ensure that any new emerging threats are recognized and able to respond to them. The more we learn about the way these microbes evolve, the better chance we have of confronting their threats to human health.
charitable foundation, O.J., et al. (2022) Increased resistance to phages through lysogenic conversion associated with the emergence of the Salmonella Typhimum monophyletic strain ST34. Microbial Genomics. doi.org/10.1099/mgen.0.000897.