Inhibition of Staphylococcus aureus by the commensal bacteria of human milk

f Human milk oligosaccharides (HMO), which constitute a major component of human milk, promote the growth of particular bacterial species in the infant's gastrointestinal tract. We hypothesized that HMO also interact with the bacterial communities present in human milk. To test this hypothesis, two experiments were conducted. First, milk samples were collected from healthy women (n ‫؍‬ 16); culture-independent analysis of the bacterial communities was performed, HMO content was analyzed, and the relation between these factors was investigated. A positive correlation was observed between the relative abundance of Staphylococcus and total HMO content (r ‫؍‬ 0.66). In a follow-up study, we conducted a series of in vitro growth curve experiments utilizing Staphylococcus aureus or Staphylococcus epidermidis and HMO isolated from human milk. HMO exhibited stimulatory effects on bacterial growth under various nutritional conditions. Analysis of culture supernatants from these experiments revealed that HMO did not measurably disappear from the culture medium, indicating that the growth-enhancing effects were not a result of bacterial metabolism of the HMO. Instead, stimulation of growth caused greater utilization of amino acids in minimal medium. Collectively, the data provide evidence that HMO may promote the growth of Staphylococcus species in the lactating mammary gland. Human milk oligosaccharides (HMO) are complex glycans highly abundant (ϳ5 to 15 g/liter) in human milk (5,6,24). Representing a diverse collection of structures, almost 150 distinct forms of HMO have been identified (42,43). Based upon their structures, HMO can be classified as simple (sialylated or fucosylated lactose compounds made of three sugar units) or complex (composed of differentially sialylated or fucosylated repeats of lacto-N-biose or N-acetyllactosamine linked to a lactose motif). Interestingly, HMO patterns are highly unique to individual women, and their concentrations vary over the course of lactation, with levels peaking in colostrum and lower concentrations in mature milk (8,12,15,39).From an evolutionary standpoint, it is logical that because the mammary gland exerts a substantial amount of energy to produce these compounds, HMO likely promote the fitness of the offspring even though the infant is largely unable to metabolize them (1, 14, 16). Research from several groups suggests the possibility that HMO are capable of interacting with an infant's gastrointestinal microbiota to promote his or her health (10,27,30,35,38). Indeed, some of the first studies in this area noted the capacity of HMO to promote growth of Bifidobacterium bifidum, a species overrepresented in the gastrointestinal tract of the breast-fed, but not formula-fed, infant (17,29,40). Over 50 years later, research has confirmed that the genetic capacity to metabolize these compounds is conserved among bifidobacteria species common in the infant's gastrointestinal tract (38). These findings suggest that HMO may serve a prebiotic function in selectively promoting the...

Section: Discussionmentioning

confidence: 99%

Human Milk Oligosaccharides Promote the Growth of Staphylococci

Hunt

Preuss

Nissan

et al. 2012

“…Bacteria commonly isolated from this biological fluid include staphylococci, streptococci, lactococci, lactobacilli, and enterococci (6,12). In previous studies, we isolated lactobacillus strains belonging to the species Lactobacillus gasseri, L. fermentum, and L. salivarius from milk of healthy mothers (10,12) and showed that their probiotic potential is similar to that of the strains commonly used in commercial probiotic products (10,14).…”

mentioning

confidence: 95%

“…In previous studies, we isolated lactobacillus strains belonging to the species Lactobacillus gasseri, L. fermentum, and L. salivarius from milk of healthy mothers (10,12) and showed that their probiotic potential is similar to that of the strains commonly used in commercial probiotic products (10,14). It has also been suggested that commensal bacteria isolated from human milk have potential use as bacteriotherapeutic agents for the prevention of breast infections caused by S. aureus (6).…”

mentioning

confidence: 97%

Oral Administration of Lactobacillus Strains Isolated from Breast Milk as an Alternative for the Treatment of Infectious Mastitis during Lactation

Jiménez

Fernández

Maldonado

et al. 2008

194

154

In this study, 20 women with staphylococcal mastitis were randomly divided in two groups. Those in the probiotic group daily ingested 10 log 10 CFU of Lactobacillus salivarius CECT5713 and the same quantity of Lactobacillus gasseri CECT5714 for 4 weeks, while those in the control one only ingested the excipient. Both lactobacillus strains were originally isolated from breast milk. On day 0, the mean staphylococcal counts in the probiotic and control groups were similar (4.74 and 4.81 log 10 CFU/ml, respectively), but lactobacilli could not be detected. On day 30, the mean staphylococcal count in the probiotic group (2.96 log 10 CFU/ml) was lower than that of the control group (4.79 log 10 CFU/ml). L. salivarius CECT5713 and L. gasseri CECT5714 were isolated from the milk samples of 6 of the 10 women of the probiotic group. At day 14, no clinical signs of mastitis were observed in the women assigned to the probiotic group, but mastitis persisted throughout the study period in the control group women. In conclusion, L. salivarius CECT5713 and L. gasseri CECT5714 appear to be an efficient alternative for the treatment of lactational infectious mastitis during lactation.

“…A nisin producer strain was isolated twice (L. lactis strains 310 and 2410) at monthly intervals in milk samples from the same donor. Lactic acid bacterial species have previously been found in human milk (6,19), but only one L. lactis strain producing nisin has previously been isolated (6). A reason for this could be that the plating technique and plates used in previous studies led to a lower frequency of isolating nisinproducing L. lactis strains.…”

mentioning

confidence: 99%

Nisin-Producing Lactococcus lactis Strains Isolated from Human Milk

Beasley

Saris

2004

130

Characterization by partial 16S rRNA gene sequencing, ribotyping, and green fluorescent protein-based nisin bioassay revealed that 6 of 20 human milk samples contained nisin-producing Lactococcus lactis bacteria. This suggests that the history of humans consuming nisin is older than the tradition of consuming fermented milk products.One of the most studied bacteriocins, nisin is naturally produced by Lactococcus lactis. Both nisin variants A and Z, with a difference of an amino acid (1), are approved for use in foodstuffs by food additive legislating bodies in the United States (Food and Drug Administration), the United Kingdom, and the European Union (16). Nisin is employed in the dairy industry to inhibit Clostridium botulinum and Bacillus cereus, due to its capacity to prevent spore germination (7,20). Nisin was first identified in fermented cow milk (13). Since then, it has been isolated from various milk and dairy products (8, 16) as well as from plant material (5, 16) and river water (21). In this study, human milk was screened for bacteria to reveal antibacterial activity caused by nisin producers.Early lactational (within 80 days of birth) human milk samples (n ϭ 20) were collected in southern Finland from healthy first-time deliverers and from mothers with several children. Two milk samples were received within a month from one donor. The donors were requested to collect milk in sterile test tubes with minimal skin contact. The fresh milk was screened within hours of delivery for bacteria with antibacterial properties by the agar diffusion test (17). Samples were spotted on nonselective Luria-Bertani agar (14) overlaid with 100 l (at an optical density at 600 nm of 1.6) of Micrococcus luteus A1 NCIMB86166 (National Collection of Industrial and Marine Bacteria), a strain sensitive to many antibacterial substances. Plates covered with M. luteus were allowed to dry with the lid open before 30-l milk sampling and were incubated overnight at 37°C in an aerobic atmosphere. Seven samples from six different mothers contained strains with strong antibacterial activity. Of the 38 isolated strains, 20 colonies produced a clear inhibition zone around M. luteus and were isolated on plates of M17 agar (Oxoid Ltd., Basingstoke, England) with 0.5% (wt/ vol) glucose (M17G) and grown overnight at 30°C.The 20 isolated inhibitory strains from human milk were characterized by partial 16S rRNA gene sequencing. A region of the 16S rRNA gene was amplified by 29 cycles of PCR (consisting of 30 s at 94°C, 60 s at 55°C, and 90 s at 72°C, with a final 120-s extension step at 72°C) with purified chromosomal DNA (18) from the strains as template and using universal primers pA (5Ј AGA GTT TGA TCC TGG CTC AG 3Ј) and pEЈ (5Ј CCG TCA ATT CCT TTG AGT TT 3Ј) (3). The amplified 900-bp fragments were harvested from low-meltingpoint gel LM-3 (Pronadisa, Madrid, Spain), purified with chloroform-propanol (14) The seven L. lactis strains (LL3, 310, 2410, 3A, 4B, 6A, and 6B) were further characterized by the RiboPrinter and compared to the ribop...