Inhibition of Staphylococcus aureus by the commensal bacteria of human milk.
OBJECTIVE
To study the bacterial diversity in expressed human milk with a focus on detecting bacteria with an antimicrobial activity against Staphylococcus aureus, known as a causative agent of maternal breast infections and neonatal infections.


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, Strep. 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. salivarius isolates suppressed growth of Staph. 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 against 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.


CONCLUSIONS
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.
Heikkilä
M P
MP
Department of Applied Chemistry and Microbiology, University of Helsinki, Helsinki, Finland.
Saris
P E J
PE
D000898:Antibiosis; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification; D015373:Bacterial Typing Techniques / Q000379:methods; D015169:Colony Count, Microbial; D005516:Food Microbiology; D006801:Humans; D013294:Lactococcus lactis / Q000378:metabolism; D008895:Milk, Human / Q000382:microbiology*; D009561:Nisin / Q000096:biosynthesis; D013211:Staphylococcus aureus / Q000254:growth & development* / Q000302:isolation & purification
D009561:Nisin