The mild infections may make a large contribution to antibiotic use, and could have a big impact on resistance evolution. A new study published in the journal PLOS Biology suggests that development of alternative therapies for mild infections could help slow the development and spread of antibiotic resistance, thereby preserving the drugs' effectiveness for use in severe infections.

Antibiotic resistance occurs when bacterial pathogens change in ways that reduce the drugs' effectiveness for use in infections. It poses a serious and sometimes deadly challenge to the treatment of severe bacterial infections. Each year, over 20,000 people die from antibiotic-resistant infections in the U.S. alone.

Most research to identify alternatives to antibiotics, such as bacteria-killing viruses, has focused on targeting bugs responsible for severe infections using alternative therapies. However, such efforts have met with limited success.

To identify approaches that might be more effective, Kristofer W. Waldetoft and Sam P. Brown of Georgia Institute of Technology reviewed previous studies of antibiotics use. They used an evolutionary framework to analyze data from these studies and determined that widespread use of antibiotics against certain mild infections may contribute to the development of antibiotic resistance.

This is, in part, because antibiotics can select for resistance in any bacteria present in a patient, not just in the target bug. And since many antibiotics operate in similar ways, a single antibiotic can promote resistance for many drugs. As a result, they concluded that research efforts to develop alternative therapies should shift focus from severe infections to milder ones.

The analysis suggests that alternative therapies for certain mild infections — which may be easier to develop — could indirectly slow development of antibiotic resistance in more dangerous bugs. This could help maintain the ability to use antibiotics against severe infections for which new drugs have been difficult to develop.

The authors note that development of non-antibiotic alternatives for mild infections is just one strategy to combat antibiotic resistance. Other strategies include shorter courses of antibiotic treatment and use of antibiotics that act against a narrower range of species.