β-defensin-2 in breast milk displays a broad antimicrobial activity against pathogenic bacteria

J Pediatr (Rio J). 2015 Jan-Feb;91(1):36-43. doi: 10.1016/j.jped.2014.05.006. Epub 2014 Sep 7.

Abstract

Objective: To describe the antimicrobial activity of β-defensin-2 produced in the mammary gland and secreted in human breast milk.

Methods: The peptide production was performed by DNA cloning. β-defensin-2 levels were quantified in 61 colostrum samples and 39 mature milk samples from healthy donors, by an indirect enzyme-linked immunosorbent assay (ELISA). Using halo inhibition assay, this study assessed activity against seven clinical isolates from diarrheal feces of children between 0 and 2 years of age. The activity of β-defensin-2 against three opportunistic pathogens that can cause nosocomial infections was determined by microdilution test.

Results: The peptide levels were higher in colostrum (n=61) than in mature milk samples (n=39), as follows: median and range, 8.52 (2.6-16.3) μg/ml versus 0.97 (0.22-3.78), p<0.0001; Mann-Whitney test. The recombinant peptide obtained showed high antimicrobial activity against a broad range of pathogenic bacteria. Its antibacterial activity was demonstrated in a disk containing between 1-4 μg, which produced inhibition zones ranging from 18 to 30 mm against three isolates of Salmonella spp. and four of E. coli. β-defensin-2 showed minimum inhibitory concentrations (MICs) of 0.25 μg/mL and 0.5 μg/mL for S. marcescen and P. aeruginosa, respectively, while a higher MIC (4 μg/mL) was obtained against an isolated of multidrug-resistant strain of A. baumannii.

Conclusions: To the authors' knowledge, this study is the first to report β-defensin-2 levels in Latin American women. The production and the activity of β-defensin-2 in breast milk prove its importance as a defense molecule for intestinal health in pediatric patients.

Keywords: Agentes anti-infecciosos; Anti-infective agents; Antimicrobial cationic peptides; Breast milk; Defensinas; Defensins; Lactancy; Lactação; Leite materno; Peptídeos catiônicos antimicrobianos; hBD2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Colostrum / chemistry*
  • Enzyme-Linked Immunosorbent Assay / methods
  • Escherichia coli / drug effects
  • Female
  • Humans
  • Lactation / immunology
  • Microbial Sensitivity Tests
  • Milk, Human / chemistry*
  • Pregnancy
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Salmonella / drug effects
  • Young Adult
  • beta-Defensins / analysis
  • beta-Defensins / pharmacology*

Substances

  • DEFB4A protein, human
  • beta-Defensins