Black Carbon Nanoparticles Modify Pathogens and Affect Resistance

Nanoparticles of black carbon, one of the main components of air pollution, have been found to modify the way bacterial pathogens grow in vitro and in vivo and to significantly increase their resistance to treatment with certain antibiotics.

While the effects of the particulate matter in air pollution on human health are well established, the effects on bacteria – organisms central to ecosystems in humans and in the natural environment – are poorly understood.

To fill this gap, investigators at the University of Leicester examined the effect of black carbon particles on two human pathogens, Staphylococcus aureus and Streptococcus pneumoniae, which are both major causes of respiratory diseases and exhibit high levels of resistance to antibiotics.

The investigators reported in the February 28, 2017, online edition of the journal Environmental Microbiology that black carbon drastically changed the development of bacterial biofilms, key aspects of bacterial colonization and survival. Results showed that exposure to black carbon induced structural, compositional, and functional changes in the biofilms of both S. pneumoniae and S. aureus. Black carbon differentially altered the tolerance of biofilms to proteolytic degradation and multiple antibiotics, increasing S. pneumoniae survival against penicillin, the front line treatment of bacterial pneumonia.

In addition, the results revealed that black carbon impacted bacterial colonization in the body. In a mouse nasopharyngeal colonization model, black carbon caused S. pneumoniae to spread from the nasopharynx to the lungs, which is essential for subsequent infection.

Senior author Dr. Julie Morrissey, associate professor of microbial genetics at the University of Leicester, said, "This work increases our understanding of how air pollution affects human health. It shows that the bacteria, which cause respiratory infections, are affected by air pollution, possibly increasing the risk of infection and the effectiveness of antibiotic treatment of these illnesses. Our research could initiate an entirely new understanding of how air pollution affects human health. It will lead to enhancement of research to understand how air pollution leads to severe respiratory problems and perturbs the environmental cycles essential for life."