Inhibition of Staphylococcus aureus by the commensal bacteria of human milk

摘要

Aims: To study the bacterial diversity in expressed human milk with a focus on detecting bacteria with an antimicrobial activity against Staphylococcus aureus, known a sa causative agent of maternal breast infections and neonatal infections. Methods and Results: Random isolates (n = 509) were collected from breast milk samples (n = 40) of healthy lactating women, genotypically identified, and tested for antimicrobial activity against Staph. aureus. Commensal staphylococci (64%) and oral streptococci (30%), with Staph. epidermidis, Step. salivarius, and Strep, mitis as the most frequent isolates, were the predominant bacterial species in breast milk. One-fifth of Staph. epidermidis and half of Strep. aureus. Enterococci (Ent. faecalis), isolated from 7.5% of samples, and lactic acid bacteria (LAB) (Lactobacillus rhamnosus, Lact. crispatus, Lactococcus lactis, Leuconoctoc mesenteroides), isolated from 12.5% of samples, were also effective aginast Staph. aureus. One L. lactis isolate was shown to produce nisin, a bacteriocin used in food industry to prevent bacterial pathogens and spoilage. Conclusions: Expressed breast milk contains commensal bacteria, which inhibit Staph. aureus. Significance and Impact of the Study: The strains inhibitory against the pathogen Staph. aureus have potential use as bacteriotherapeutic agents in preventing neonatal and maternal breast infections caused by this bacterium.