Inhibitory and Bactericidal Effects of Hydrogen Peroxide Production byStreptococcus pneumoniaeon Other Inhabitants of the Upper Respiratory Tract

Abstract

An inverse correlation between colonization of the human nasopharynx by Streptococcus pneumoniae and Haemophilus influenzae, both common upper respiratory pathogens, has been reported. Studies were undertaken to determine if either of these organisms produces substances which inhibit growth of the other. Culture supernatants from S. pneumoniae inhibited growth of H. influenzae, whereas culture supernatants from H. influenzae had no effect on the growth of S. pneumoniae. Moreover, coculture of S. pneumoniae and H. influenzae led to a rapid decrease in viable counts of H. influenzae. The addition of purified catalase prevented killing of H. influenzae in coculture experiments, suggesting that hydrogen peroxide may be responsible for this bactericidal activity. H. influenzae was killed by concentrations of hydrogen peroxide similar to that produced by S. pneumoniae. Hydrogen peroxide is produced by the pneumococcus through the action of pyruvate oxidase (SpxB) under conditions of aerobic growth. Both an spxB mutant and a naturally occurring variant of S. pneumoniae, which is downregulated in SpxB expression, were unable to kill H. influenzae. A catalase-reversible inhibitory effect of S. pneumoniae on the growth of the respiratory tract pathogens Moraxella catarrhalis and Neisseria meningitidis was also observed. Elevated hydrogen peroxide production, therefore, may be a means by which S. pneumoniae is able to inhibit a variety of competing organisms in the aerobic environment of the upper respiratory tract.

Reactive oxygen: A novel antimicrobial mechanism for targeting biofilm-associated infection

“…Of particular interest is the >2-fold increase in expression of pyruvate oxidase (SpxB), an enzyme responsible for the production of extracellular hydrogen peroxide (H2O2). Production of this ROS confers pneumococcus a competitive advantage over other pathogens that share the same nasopharyngeal niche, including NTHi [19]. It is possible that through exploitation of this susceptibility towards H2O2 that the tolerance of NTHi biofilms to antibiotic treatment could be diminished, or may yet provide an avenue for the development of an alternative therapeutic strategy that dispenses with the need for antibiotic prescription.…”

Oxidative stress tolerance is manganese (Mn2+) regulated in Streptococcus gordonii

“…Many mitis-group streptococci produce relatively large amounts of H # O # during aerobic growth by the action of oxidase enzymes, e.g. NADH oxidase (Nox) and pyruvate oxidase (SpxB), the latter of which is up-regulated in response to O # (Auzat et al, 1999 ;Pericone et al, 2000). The expression of sodA is also enhanced under oxidative stress in some streptococci (Gibson & Caparon, 1996 ;Yesilkaya et al, 2000).…”

“…A number of species of streptococci appear to express a single SOD activity with Mn as preferred co-factor (Nakayama, 1992 ;Gibson & Caparon, 1996 ;Chang & Hassan, 1997 ;Pericone et al, 2000), while S. pneumoniae has been reported to produce MnSOD and FeSOD activities (Yesilkaya et al, 2000). To detect SOD activity in S. gordonii DL1, cell-free extracts of bacteria grown in BHY medium were subjected to non-denaturing PAGE and gels were activity-stained using NBT (Beauchamp & Fridovich, 1971).…”

Purification and Characterization of a Chimeric Enzyme fromHaemophilus influenzae Rd That Exhibits Glutathione-dependent Peroxidase Activity

“…Besides oxidative stress from its aerobic respiratory metabolism or as a result of the high O 2 tension at the nasopharynx, H. influenzae may also be exposed to high levels of oxidants produced by the host's immune system, which uses the destructive power of reactive oxygen species to eliminate bacterial infections (10). Moreover, experimental data indicate that H. influenzae has to deal with H 2 O 2 secreted by peroxidogenic Streptococci (11). Whereas the existence of an H 2 O 2 -inducible catalase (HktE) has been described in H. influenzae Rd, the enzyme seems to be redundant (12,13).…”