Role of Staphylococcus aureus catalase in niche competition against Streptococcus pneumoniae

Division of Pediatric Infectious Diseases and the Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, Department of Pediatrics, Division of Pharmacology & Drug Discovery, School of Medicine, University of California at San Diego, La Jolla, CA 92093

^* To whom correspondence should be addressed. Email: george.liu{at}cshs.org.

	Abstract

Nasal colonization by Staphylcococcus aureus is a major predisposing factor for subsequent infection. Recent reports of increased S. aureus colonization among children receiving pneumococcal vaccine implicate Streptococcus pneumoniae as an important competitor for the same niche. Since S. pneumoniae uses H₂O₂ to kill competing bacteria, we hypothesized that oxidant defense could play a significant role in promoting S. aureus colonization of the nasal mucosa. Using targeted mutagenesis, we show that S. aureus expression of catalase contributes significantly to the survival of the pathogen in the presence of S. pneumoniae, both in vitro and in a murine model of nasal co-colonization.