For years, scientists have been puzzled by a strange form of antibiotic resistance known as “heteroresistance.” This occurs when a small percentage of bacteria in a population can resist antibiotics, making it difficult to detect with standard clinical tests. Some experts believe that heteroresistance could be responsible for many cases of antibiotic treatment failures.
Karin Hjort, a microbiologist at Uppsala University in Sweden, is a leading authority on heteroresistance. In an interview with Live Science, Hjort explained what heteroresistance is and its implications for combating superbugs.
Heteroresistance is defined as having a resistant subpopulation within an otherwise antibiotic-susceptible group of bacteria. This subpopulation is typically very small, around one in ten million bacterial cells, and the level of resistance is significantly higher than the main population.
While heteroresistance is not a new phenomenon, it presents a unique challenge compared to general antibiotic resistance. These resistant subpopulations can survive higher concentrations of antibiotics, quickly outgrowing the susceptible bacteria when exposed to these drugs. Once the selection pressure is removed, the few susceptible cells that survived will eventually outcompete the resistant ones.
Unlike the common perception of bacteria being either resistant or susceptible, heteroresistance exists as a gray area where bacteria can transition between the two states rapidly. This transition typically occurs in response to antibiotic treatment, with resistant subpopulations surviving while susceptible ones perish.
Identifying heteroresistance in bacteria requires complex laboratory tests, making it challenging to detect in clinical settings. Hjort’s research focuses on unraveling how bacteria develop heteroresistance, with some gaining mutations while others acquire resistance through gene amplification.
While all bacteria have the potential to become heteroresistant, the specific mechanisms can vary between species. Not all antibiotics may trigger heteroresistance, and further research is needed to understand the relationship between different types of antibiotics and bacteria.
Heteroresistance is a common occurrence in clinical isolates, potentially contributing to treatment failures. While patient mortality due to treatment failure is rare, delays in recovery can result in extended hospital stays, posing challenges for healthcare providers.
Looking ahead, Hjort hopes for improved methods to quickly identify heteroresistant strains in clinical settings. Developing simpler and faster testing techniques is essential to guide treatment decisions and prevent the misuse of antibiotics. By enhancing our understanding of heteroresistance, researchers aim to provide clinicians with the tools needed to combat antibiotic-resistant bacteria effectively.
