The Antimicrobial Effect of Lactoferrin on Gram-Negative and Gram-Positive Bacteria Original paper

What was studied?

This in vitro experimental study evaluated the antibacterial activity of lactoferrin against both Gram-negative and Gram-positive clinical bacterial isolates. The goal was to compare lactoferrin’s effectiveness on different bacterial species and assess whether there was a differential effect between Gram-positive and Gram-negative organisms.

Who was studied?

The researchers tested four bacterial strains—two Gram-positive (Staphylococcus epidermidis and Bacillus cereus) and two Gram-negative (Campylobacter jejuni and Salmonella spp.)—all of which were clinical isolates from wound, blood, urine, stool, and sputum samples collected at Namazi Hospital in Shiraz, Iran.

What were the most important findings?

Lactoferrin demonstrated notable antibacterial activity against all tested strains, with higher efficacy against Gram-positive bacteria. Specifically, colony reduction rates were highest for S. epidermidis and B. cereus, compared to Salmonella and C. jejuni. The authors confirmed that the antibacterial effect was statistically significant across all species.

Mechanistically, lactoferrin exerts its antimicrobial activity primarily through iron sequestration, depriving bacteria of an essential growth factor. In addition, apolactoferrin damages bacterial membranes, especially in Gram-negative species, by binding lipid A in LPS and disrupting membrane integrity. This dual action supports lactoferrin’s bacteriostatic and bactericidal capabilities. From a microbiome perspective, the selective suppression of pathogens without affecting commensals supports lactoferrin’s role as a microbiome-compatible antimicrobial agent, particularly in mucosal environments where microbial balance is critical for immune and epithelial homeostasis.

What are the implications of this study?

This study supports lactoferrin as a natural antimicrobial agent with broad efficacy, especially against Gram-positive pathogens. The non-toxic, iron-modulating mechanism offers an advantage over conventional antibiotics, particularly in the context of rising antimicrobial resistance. Clinically, lactoferrin could serve as a preventive or adjunctive therapy in infections where microbial disruption must be minimized, such as in gastrointestinal or urogenital settings where microbiome preservation is essential. The study further underscores the need to explore lactoferrin’s integration into microbiome-sensitive antimicrobial protocols and as a candidate in nutraceutical formulations.