The ‘captain of the men of death’, Streptococcus pneumoniae , fights oxidative stress outside the ‘city wall’

Abstract

We have come a long way since Streptococcus pneumoniae was first isolated in 1880. Over the years, the ability to combat this gram‐positive bacterium branded ‘captain of the men of death’ by William Osler in 1918 has been greatly enhanced by the development of vaccines and antibiotics. However, despite the existence of these therapeutic strategies, S. pneumoniae continues to kill to this day. The bacterium, which is usually found as a resident of the human naso‐oropharynx, causes indeed serious invasive diseases such as pneumonia, bacteraemia and meningitis, especially in young children, the elderly and immunocompromised individuals. Worldwide, it causes between 700,000 to 1 million child deaths every year (O'Brien et al, 2009). The limitations of existing vaccines, the emergence of antibiotic resistant clones, and the aging of the population will only make the problem worse, calling for new approaches against this pathogenic microorganism. S. pneumoniae is an anaerobic bacterium. However, it is tolerant to the oxygen (O2) present in the respiratory tract and is equipped with antioxidant systems to fight reactive oxygen species (ROS). ROS, such as superoxide (![Formula][1] ) and hydrogen peroxide (H2O2), are produced by transfer of electrons to O2 following metabolic reactions or through the oxidative burst in neutrophils and macrophages. Like many other bacteria, S. pneumoniae possesses specialized antioxidant enzymatic squads that are in the front line to convert ROS to innocuous products unable to damage cellular components. The ROS detoxifying proteins that have been described in S. pneumoniae include a superoxide dismutase (SodA), a thiol peroxidase (TpxD) and an alkyl hydroperoxidase … [1]: /embed/mml-math-1.gif