Colorized image of methicillin-resistant Staphylococcus aureus (MRSA) bacteria; from a scanning electron micrograph captured at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Image Credit: National Institute of Allergy and Infectious Diseases (CC BY 2.0)
MRSA (short for methicillin-resistant Staphylococcus aureus) is a commonly found group of bacteria that spread primarily through skin-to-skin contact. Unlike other S. aureus strains, MRSA is resistant to a class of commonly used antibiotics known as ß-lactams. As a result, MRSA infections are extremely difficult to treat and can lead to potentially life-threatening conditions, such as pneumonia and sepsis.
It has been suggested that another way to eliminate drug-resistant bacteria like MRSA is to treat them with bacteriophages, viruses that specifically infect and kill bacteria. However, bacteria can become resistant to these phages as well. Interestingly, this can result in an evolutionary trade-off: as bacteria become more resistant to phages, they become less resistant to antibiotics. Could this trade-off also occur in MRSA?
To investigate, Tran et al. exposed different strains of MRSA to bacteriophages. While most bacterial cells were killed off, a small fraction survived and regrew to form a new population. Tran et al. found that the phage-resistant MRSA population became sensitive once again to ß-lactam antibiotics. Genetic analysis also revealed that the regrown MRSA population activated a different set of genes. Specifically, they downregulated genes that trigger and promote infections, as well as genes associated with cell-to-cell communication.
These findings suggest that bacteriophages could be a valuable tool for restoring antibiotic sensitivity in MRSA and offer fresh insights into how drug resistance evolves. Additionally, the study highlights how S. aureus bacteria genetically respond to bacteriophage infections. Further research is needed to better understand the molecular mechanisms behind this phage- and antibiotic-resistance trade-off.
