In an effort to take the resistance out of antibiotic-resistant bacteria, University of Idaho researchers are getting down to the genetic level to figure out how multidrug resistance plasmids increase their resistance.

Thanks to a five-year, $1.7 million grant from the National Institutes of Health, Eva Top, professor of biology, and Zaid Abdo, assistant professor of mathematics and statistics, will study drug resistant plasmids and the range of bacterial hosts in which they can be supported.

Plasmids are little pieces of DNA within a bacterial cell that jump from bacterium to bacterium. As they spread, they bring genetic information into the new cell and can rapidly increase the number of antibiotics to which bacteria are resistant.

"More and more bacteria are becoming resistant to antibiotics, making it more difficult to treat infections," says Top. "Plasmids play an important role in this spread of drug resistance, and we want to find out what determines the range of bacterial hosts they can move into.

Very little is known about the range of hosts to which plasmids can transfer, and if and how that range can change over time."

Top notes plasmids can confer resistance to 10 or more antibiotics as they move around. While some plasmids have a narrow range of hosts they can transfer to and stably replicate in, broad-host-range plasmids can transfer and replicate in distantly related bacteria—increasing the resistance spectrum. That is where Top's and Abdo's research will focus and provide a foundation for future opportunities to restrict transfer and spread of resistance.

Spurring the research is a growing trend of bacteria that are becoming resistant to antibiotics, like methicillin-resistant staphylococcus aureus (MRSA) infections that can become life-threatening. In extreme cases, doctors can run out of antibiotics to treat the infection.

"Plasmids have always been around and have carried antibiotic resistance," she says. "But with the high usage of antibiotics, we need to figure out how the plasmids work before we can fight them."

Top, Abdo, and their teams of students and researchers will be working to unlock the mystery behind plasmids: why do some plasmids multiply with the bacteria, but sometimes the transfer doesn't take place?