Nearly 1 billion children worldwide carry Streptococcus pneumoniae (Spn) in the upper airways. Human bile salts are known to dissolve the Spn cell wall of which deoxycholic acid (DoC) is approved by the FDA for aesthetic treatment (10 mg/ml). We investigated the antimicrobial effect of DoC against pneumococcal strains.
Dose-response and time-course studies were conducted with Spn reference strains (N=2) and MDR strains (N=3). We then challenged Spn strains (N=55), including vaccine types, and other oral bacterial species (N=21) with a MIC90 and viability was investigated. An in-vitro model of pneumococcal colonization assessed the antimicrobial activity in a life-like scenario.
MIC90 was achieved with 0.5 mg/ml of DoC incubated for 2 h with vaccine and non-vaccine type strains and reference strains TIGR4 and D39. The pneumococcal colonization model demonstrated that DoC eradicated 107 cfu/ml of MDR strains bearing resistance to Penicillin, Meropenem, and/or Erythromycin within 20 min post-exposure. Viability of most oral bacterial species was not affected by a treatment with a Spn-MIC90.
DoC eradicated Spn strains with a MIC90 20-fold lower than the recommended human dose. It has the potential for prophylactic eradication of Spn carriage from the upper airways with no disturbance of other oral bacteria.