🦠 Discovery of a survival mechanism of Staphylococcus aureus in the blood

Staphylococcus aureus is one of the main causes of bacterial infection worldwide, notably responsible for hospital-acquired infections. Scientists from INRAE, the CEA and the CNRS have discovered how this bacterium can survive in the hostile environment of the blood.

Staphylococcus aureus detects heme, a molecule toxic to bacteria, thanks to a specific biosensor that triggers the synthesis of a protective barrier on its surface. This mechanism allows the progression of the infection due to the survival and multiplication of this pathogen in the blood. The discovery of how this sensor works opens up prospects for new antibiotic strategies against Staphylococcus aureus. These results are published in the journal mBio.


Bacterial infections are the second leading cause of death worldwide and Staphylococcus aureus, Staphylococcus aureus, ranks among the deadliest bacteria. In 2019, Staphylococcus aureus is estimated to have caused more than 1 million deaths worldwide and more than 16,000 in France, according to a study published in 2022 in The Lancet.

In France, it is one of the main germs causing hospital-acquired infections and food poisoning. Today antibiotics remain the most effective treatment, but resistant strains are emerging, posing a risk of therapeutic dead end. In this context, a research team from INRAE, in collaboration with the CEA and the CNRS, has been studying Staphylococcus aureus for several years, particularly how it manages to survive in the blood.

Blood: a hostile environment for bacteria

Mammalian blood contains red blood cells, which carry oxygen. These cells contain large amounts of a molecule called heme, which is used to bind oxygen. But heme is toxic to bacteria or other cells if it escapes from red blood cells. However, if they find themselves in the blood, pathogenic bacteria like Staphylococcus aureus cause hemolysis, that is, the bursting of red blood cells and the release of heme. They can then come into contact with heme, which is toxic to them.

The scientists discovered that Staphylococcus aureus is able to detect heme thanks to a specific sensor called HssS present on its membrane. When it detects heme, this sensor triggers a defense mechanism in Staphylococcus aureus that synthesizes a heme efflux pump, a mechanism that pushes heme out of the bacterium. This creates a protective barrier allowing it to survive in the blood and progress the infection. Laboratory experiments show that Staphylococcus aureus lacking the HssS sensor, and therefore unable to detect heme, have a greatly weakened virulence.

A lead for new innovative antibiotic strategies

Faced with the challenges of antibiotic resistance, these results open new avenues for antibiotic strategies to fight Staphylococcus aureus by searching for molecules that inhibit the HssS sensor, which would reduce its virulence. Moreover, since the HssS sensor is specific to pathogenic bacteria, antibiotic strategies targeting this sensor would be more targeted and would theoretically not affect other bacteria beneficial to our body, such as those making up the gut microbiota.