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Anti-Pneumococcal Properties of the Native Human Milk Oligosaccharide Fraction: A Concentration-Dependent Study
Oliwia Makarewicz1, Tinatini Tchatchiashvili1, Lisa Jasef1
1Institute of Infectious Diseases and Infection Control, Jena University Hospital, Friedrich Schiller University Jena, Am Klinikum 1, 07747 Jena, Germany.
Insights
Human milk oligosaccharides (HMOs) demonstrate potent, serotype-independent antibacterial activity against Streptococcus pneumoniae. These findings highlight HMOs
Area of Science:
- Microbiology
- Immunology
- Pediatrics
Background:
- Streptococcus pneumoniae is a leading cause of infant infections.
- Human milk oligosaccharides (HMOs) are bioactive breast milk components with known immune properties.
Purpose of the Study:
- Investigate the antipneumococcal effects of HMOs across various S. pneumoniae serotypes.
- Determine concentration-dependent activity and explore underlying mechanisms of HMOs against pneumococci.
Main Methods:
- Growth curve analysis and colony-forming unit (CFU) assays were used to evaluate growth inhibition and bacterial viability.
- Tested HMOs against multiple S. pneumoniae serotypes at varying concentrations.
Main Results:
- HMOs inhibited pneumococcal growth in a concentration-dependent manner, with complete killing at 5 mg/mL for all serotypes.
- Physiologically relevant colostrum concentrations (20-25 mg/mL) showed complete bactericidal effects.
- Lactose showed no antimicrobial activity, confirming HMO specificity.
Conclusions:
- HMOs exhibit serotype-independent antipneumococcal activity, potentially by disrupting adhesion or metabolism.
- HMOs show promise as adjunctive agents for preventing pneumococcal infections in infants.
- Further in vivo studies are warranted to explore clinical applications.
Abstract:
Streptococcus pneumoniae is a major opportunistic pathogen and a leading cause of severe infections in infants under two years of age. Human milk oligosaccharides (HMOs), key bioactive components of breast milk, possess immunomodulatory and antimicrobial properties. In this study, the antipneumococcal effects of HMOs are investigated across multiple S. pneumoniae serotypes, focusing on concentration-dependent activity and underlying mechanisms. Growth inhibition and bacterial viability were evaluated using growth curve analysis and colony-forming unit (CFU) assays. HMOs inhibited pneumococcal growth in a concentration-dependent manner, with suppression observed at 1.5-2.5 mg/mL and complete killing at 5 mg/mL for all serotypes. Nonencapsulated strains were more sensitive, with inhibition at 1 mg/mL. In the CFU assays, killing occurred at 1.25-5 mg/mL depending on the strain. At physiologically relevant colostrum concentrations (20-25 mg/mL), HMOs achieved complete bactericidal effects across all the tested strains. In contrast, lactose at equivalent doses showed no measurable antimicrobial activity, confirming the specificity of the observed effects. Overall, HMOs exhibit serotype-independent antipneumococcal activity, possibly through interference with bacterial adhesion or metabolic disruption. These findings suggest a potential role for HMOs as adjunctive agents in the prevention of pneumococcal infections in vulnerable populations, such as infants, and warrant further in vivo studies to validate these effects and explore clinical applications.
