Isolation, identification and characterization of Staphylococcus epidermidis in human milk

- Eleven Staphylococcus epidermidis strains were isolated from human breast milk.
- According to PFGE analysis, S. epidermidis strains were divided into two main groups.
- Five of S. epidermidis showed inhibitory effect on all pathogens used in the study.
- S. epidermidis population contributes towards the beneficial effect of human milk.

Staphylococcus epidermidis is one of the dominant bacteria present in human breast milk. A baby takes approximately 105-107 bacteria daily via consuming 800 mL of breast milk. This means that the microbiota of human milk affects the intestinal flora of the infant and the immune system of the babies as well. In the current study, S. epidermidis strains of human milk were isolated, characterized and evaluated for their antimicrobial efficacy against Listeria monocytogenes 7644, Staphylococcus aureus ATCC 25923, Salmonella enterica Typhimurium SL1344 and Escherichia coli CFA 1. Eleven S. epidermidis strains were isolated from human breast milk and confirmed by 16S rDNA gene sequencing method. According to PFGE cluster tree, the strains were divided into two main groups; A and B with 22%, and 35% similarity rate, respectively. The group A was also divided into 3 subgroups; A1, A2 and A3. The antimicrobial efficacy results showed that all S. epidermidis strains inhibited the E. coli strain and 5 of 11 S. epidermidis showed antimicrobial activity against all of the pathogenic bacteria tested in this study. The results indicate that S. epidermidis population in human milk is diverse and contributes towards the beneficial effect of human milk.