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J. Bacteriol. doi:10.1128/JB.00950-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Hydrogen peroxide mediated interference competition by Streptococcus pneumoniae has no significant effect on Staphylococcus aureus nasal colonization of neonatal rats

Department of Biology, Emory University, Atlanta, GA 30322, USA

^* To whom correspondence should be addressed. Email: emargol{at}emory.edu.

	Abstract

It has been proposed that the relative scarcity of Staphylococcus aureus and Streptococcus pneumoniae co-colonization in the nasopharynx of humans can be attributed to hydrogen peroxide-mediated interference competition. Previously it has been shown in vitro that H₂O₂ produced by S. pneumoniae is bactericidal to S. aureus. To ascertain whether H₂O₂ has this inhibitory effect in the nasal passages of neonatal rats, colonization experiments were performed with S. aureus and S. pneumoniae. The results of these experiments in neonatal rats are inconsistent with the hypothesis that hydrogen peroxide - mediated killing of S. aureus by S. pneumoniae is responsible for relative scarcity of co-colonization by these bacteria. In mixed inocula colonization experiments and experiments where S. aureus invades the nasopharynx of rats with established S. pneumoniae populations, the density of S. aureus did not differ whether the S. pneumoniae strain was H₂O₂ secreting or non-H₂O₂ secreting strain (SpxB). Moreover, the advantage of catalase production by S. aureus in competition with a non-catalase producing strain (KatA) during nasal colonization is no greater in the presence of H₂O₂ producing S. pneumoniae than non-H₂O₂ producing S. pneumoniae.