Is hydrogen peroxide responsible for the inhibitory activity of alpha-haemolytic streptococci sampled from the nasopharynx?

• Published in: Acta oto-laryngologica 2003-08, Vol.123 (6), p.724-729
• Main Authors: Tano, Krister, Håkansson, Eva Grahn, Wallbrandt, Pia, Rönnqvist, Daniel, Holm, Stig E., Hellström, Sten
• Format: Article
• Language: English
• Subjects: bacterial interfence; Bacterial Physiological Phenomena; Biological and medical sciences; Ear, auditive nerve, cochleovestibular tract, facial nerve: diseases, semeiology; electron microscopy; Ent. Stomatology; Haemophilus influenzae - growth & development; Humans; hydrogen peroxide; Hydrogen Peroxide - metabolism; Medical sciences; Moraxella catarrhalis - growth & development; Nasopharynx - microbiology; Non tumoral diseases; Otitis Media - microbiology; Otorhinolaryngology. Stomatology; Pharmacology. Drug treatments; Streptococcus pneumoniae - growth & development; Viridans Streptococci - growth & development; Viridans Streptococci - isolation & purification; Viridans Streptococci - metabolism; α-haemolytic Streptococci
• ISSN: 0001-6489; 1651-2251
• DOI: 10.1080/00016480310000403

Objective-The inhibitory effect of alpha-haemolytic Streptococci (AHS) in vitro on the three commonest otitis media pathogens, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, was previously investigated. The aim of this study was to determine the mechanism of this inhibitory activity. Material and Methods-When fractions of AHS filtrate were assayed to determine their inhibitory activity after size-exclusion chromatography, the inhibitory activity was found in the fractions with a low molecular weight. The inhibitory effect was completely reversed when catalase was added to the cell-free filtrate of AHS. A quantitative method also revealed high production (approximately 3 mmol/l) of hydrogen peroxide in the AHS filtrate with the best inhibitory activity. Electron microscopy of bacteria exposed to AHS filtrate with an inhibitory effect showed changes similar to bacteria exposed to hydrogen peroxide. Results-When fractions of AHS filtrate were assayed to determine their inhibitory activity after size-exclusion chromatography, the inhibitory activity was found in the fractions with a low molecular weight. The inhibitory effect was completely reversed when catalase was added to the cell-free filtrate of AHS. A quantitative method also revealed high production (approximately 3 mmol/l) of hydrogen peroxide in the AHS filtrate with the best inhibitory activity. Electron microscopy of bacteria exposed to AHS filtrate with an inhibitory effect showed changes similar to bacteria exposed to hydrogen peroxide. Conclusions-We conclude that the inhibitory effect of AHS is most likely due to the production of hydrogen peroxide. The significance of hydrogen peroxide production of AHS is discussed in relation to the non-specific and specific mucosal defence systems.