Bacterial growth in breast milk expressed under hygienic control: a pilot study

BMC Research Notes Miyatake et al. BMC Research Notes (2024) 17:271 https://doi.org/10.1186/s13104-024-06933-2 Open Access R E S E A R C H N OT E Bacterial growth in breast milk expressed under hygienic control: a pilot study Mika Miyatake1* , Yukihiro Tambe2 and Yumiko Tateoka1 Abstract Objective In this pilot study, we verified safe practices for breast milk expression, storage, and duration, based on bacteriological results. Results We collected breast milk samples from three healthy lactating volunteers and analyzed the bacterial flora and changes in the viable bacterial counts (including those of Staphylococcus) of the samples. Although no consistent change could be observed in the abundance of a particular bacterial group in samples expressed under hygienic control conditions, viable bacterial counts were higher in self-expressed milk than in milk expressed under hygienic control conditions. In conclusion, increased hygiene awareness is vital during breast milk expression and storage. Keywords Breast milk, Nipple skin wiping, Bacteria, Storage, Hygiene Introduction In Japan, hand expression of breast milk involves prior hand washing with soap and wiping the nipple and areola with clean cotton. However, preparation techniques are midwife-dependent. Certain midwives advise that wiping the nipple and areola before breastfeeding is unnecessary as the mucus secreted by the sebaceous glands of the areola protects the nipple, although this practice has not been validated. Furthermore, there are different recommendations concerning expressed breast milk storage duration. The Academy of Breastfeeding Medicine recommends the following optimum milk storage conditions: 4 h at room temperature (16–29 ℃) and 4 days in the refrigerator (~ 4 ℃) [1]. *Correspondence: Mika Miyatake 1 Department of Clinical Nursing, Division of Maternity Nursing, Shiga University of Medical Science, Tsukinowa-cho, Seta, Otsu-shi, Shiga, Japan 2 Department of Pathology, Division of Microbiology and Infectious Diseases, Shiga University of Medical Science, Tsukinowa-cho, Seta,Otsushi, Shiga, Japan Unfortunately, studies verifying the bacterial contamination of breast milk expressed with and without any hygienic control (wiping the nipple and areola before milk expression) are scarce. Therefore, bacterial contamination-related bacteriological safety assessment of expressed breast milk is of utmost importance. We examined the bacteriological safety of breast milk expressed using different methods, assessing bacterial growth under different storage conditions, including duration and location. Methods Study design We performed a pilot study on bacterial growth in breast milk. The Research Ethics Committee of the Shiga University of Medical Science approved this study (No. R2021-096). The research was conducted between September 24 and December 31, 2021. Participants Three lactating women with no abnormalities during their pregnancy, delivery, and postpartum period were included. The selection criteria were as follows: age ≥ 20 © The Author(s) 2024. 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To view a copy of this licence, visit http:// creativecommons.org/licenses/by-nc-nd/4.0/. Miyatake et al. BMC Research Notes (2024) 17:271 Page 2 of 6 years, ability to express 10 mL of breast milk from each breast in one batch, and provision of written consent. The exclusion criteria comprised formula feeding owing to the lack of sufficient daily breast milk supply and puerperal breast and nipple problems. To recruit participants, we distributed leaflets at the nursery school of our university. We explained the study verbally to the participants, and then arranged the date and site (a seminar room at our university or the participant’s home) for milk collection. We collected the following information through a verbal interview: number of days postpartum; feeding interval on the day of the survey; formula use; last time of milk discharge; presence of breast milk leakage; breast pad use; last time of breast pad change; breast or nipple problems; and last intake of oral medication since the day of the survey. The use of medications (especially antimicrobials) was investigated since they might affect bacteriological results. Viable bacterial count in breast milk samples Breast milk collection We collected approximately 10 mL of breast milk from both breasts of the participants and classified the samples into two groups based on whether they were obtained under hygienic conditions by the researcher or through self-expression performed by the participant. Only one expressing session was performed per participant. The expression process under hygienic conditions by the researcher was as follows: the researcher disinfected their hands with alcohol gel sanitizer and put on sterile gloves. Four pieces of absorbent cotton (soaked with pure water and sterilized in an autoclave) were used to wipe off the nipple and areola in a circular motion from the center to the outside of the nipple. Subsequently, the first few drops of milk were discharged onto a tissue, the sterile gloves were changed, and a sterile tube was used to collect the milk sample. The milk extraction process by the participants was as follows: the participants washed their hands and fingers with soap and running water. The first few drops of milk were discharged onto a tissue, and a sterile tube was used to collect the milk sample. We immediately transferred the collected milk samples into a cooler with ice and a temperature maintained near 0 °C, took them to the laboratory, and labeled them as samples I–III according to participants 1–3, respectively. We tested breast milk whey susceptibility to S. aureus (ATCC25923) using microdilution in 96-well plates as previously described [4]. 16 S rRNA bacterial flora analysis Immediately after collection, we submitted the six samples to 16 S rRNA bacterial flora analysis by Repertoire Genesis Inc [2]. Viable bacterial counts were measured in milk samples collected immediately, in those stored at room temperature (27.4 ± 0.12 (...truncated)