Objectives
Non-digestible oligosaccharides such as milk oligosaccharides (MOS) can regulate and influence immune function. As an example, galactooligosaccharides (GOS), and 2′-fucosyllactose (2′-FL; a specific human MOS) regulate immune development and functionality. Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA), both serious pathogens, can cause severe and life-threatening infections. The aim of this study was to examine the effects of GOS and 2′-FL on bacterial growth and on polymorphonuclear (PMN) phagocytosis.

Methods
PMNs were isolated from heparinized whole human blood before treatment/incubation with GOS (0.0625–10%), 2′-FL (0.5–2.5%) and/or GOS combined with 2′-FL (GOS 10%/2′-FL 2.5%; GOS 0.0625%/2′-FL 0.5%) and incubation with green florescent protein (GFP)-labeled SA or PA for 60 h. GFP-relative fluorescent units (GFP-RFU) was measured ≤60 h using a plate reader. Bacterial lag time was determined by the time to onset of exponential bacterial fluorescence/growth alone or after co-culture of bacteria and PMN. Viable bacterial colony-forming units (CFUs) were determined after 60 h.

Results
SA and PA growth lag time was suppressed by co-incubation with GOS in a concentration-dependent manner. This was significant for both SA and PA at concentrations >2.5% GOS (P ≤ 0.05 for both SA and PA) but only for SA at 1% GOS (P ≤ 0.05). 1.5% 2′-FL significantly suppressed the lag time of SA growth (P ≤ 0.05) and was effective against SA and PA at 2.5% (P ≤ 0.01 and P ≤ 0.01, respectively). GOS (10%, 5%) and 2.5% 2′-FL significantly decreased SA and PA bacterial growth/CFUs (P ≤ 0.05).

Conclusion
The data suggests that both GOS and 2′-FL can suppress growth of serious pathogens and enhance phagocytosis.