Bacteriological quality of raw human milk: effect of storage in a refrigerator

Bacterial Growth in Expressed Mother's Milk Stored and Transported Under Different Simulated Conditions in a Tropical Country

Background: Research on how storage and transport of expressed human milk in a tropical country affect the milk bacterial count is limited. Materials and Methods: A cross-sectional descriptive study of 50 mothers of infants in a Sri Lankan tertiary neonatal unit was performed. Expressed mother's milk was divided into three bottles and kept under varied environmental conditions to simulate different storage and transport methods. Initial bacterial culture of milk was performed <30 minutes after expression, with further cultures at predetermined times. Bottles A and B were stored at room temperature and in a cool bag for the first 6 hours, respectively, and then refrigerated; and bottle C was refrigerated for 24 hours, transported in a cool bag for 6 hours, and rerefrigerated until 72 hours. Total colony counts >10⁵ colony-forming units (CFU)/mL of viable microorganisms or >10⁴ CFU/mL of either Enterobacteriaceae or Staphylococcus aureus were considered positive. Results: Initial culture was positive in 30% (15/50) of samples; majority, 87% (13/15), of these were S. aureus. For bottle A, 26% (13/50), 36% (18/50), 34% (17/50), and 26% (13/50) of samples were positive at 4, 6, 24, and 72 hours, respectively. For bottle B, positive cultures were found in 26% (13/50) and 17% (8/47) of samples at 24 and 72 hours, respectively. For bottle C, results were similar to bottle B. Conclusions: Transportation of expressed mother's milk for 4 hours in a tropical climate using a low-cost cool bag, with refrigeration at other times, maintained acceptable bacterial counts for up to 72 hours after expression. Hygienic practices at collection are extremely important as most samples with significant bacterial growth were positive on initial culture.

Effect of storage on breast milk antioxidant activity

BACKGROUND

Human milk, which contains compounds beneficial to infants, is often expressed and stored before use. Changes in its antioxidant activity with storage have not been studied.

OBJECTIVES

To measure antioxidant activity of fresh, refrigerated (4 degrees C), and frozen human milk (-20 degrees C), stored for two to seven days; to compare the antioxidant activity of milk from mothers delivering prematurely and at term; to compare the antioxidant activity of infant formulas and human milk.

METHODS

Sixteen breast milk samples (term and preterm) were collected from mothers within 24 hours of delivery and divided into aliquots. Fresh samples were immediately tested for antioxidant activity, and the rest of the aliquots were stored at -20 degrees C or 4 degrees C to be analysed at 48 hours and seven days respectively. The assay used measures the ability of milk samples to inhibit the oxidation of 2,2'-azino-di-3-(ethylbenzthiazolinesulphonate) to its radical cation compared with Trolox.

RESULTS

Antioxidant activity at both refrigeration and freezing temperatures was significantly decreased. Freezing resulted in a greater decrease than refrigeration, and storage for seven days resulted in lower antioxidant activity than storage for 48 hours. There was no difference in milk from mothers who delivered prematurely or at term. Significantly lower antioxidant activity was noted in formula milk than in fresh human milk.

CONCLUSIONS

To preserve the antioxidant activity of human milk, storage time should be limited to 48 hours. Refrigeration is better than freezing and thawing.

Bacteriological screening of expressed breast milk revealed a high rate of bacterial contamination in Chinese women

A screening programme for expressed breast milk (EBM) revealed the alarming fact that our study group had the highest rate of contamination ever reported. The programme started in July 2002 and involved a group of Chinese women whose premature babies were in the neonatal intensive care unit. EBM was considered to be contaminated if there was any growth of pathogens, including Gram-negative bacteria, enterococci or Staphylococcus aureus, or if the total bacterial count was >10(5) cfu/mL. Of 59 samples from 23 mothers, 63% were contaminated. This high contamination rate could be due to the Chinese tradition of avoiding bathing for one month after childbirth. Previous studies have shown that feeding EBM rather than premature infant formula milk has advantages in terms of decreased incidence of necrotizing enterocolitis and neonatal sepsis. However, in this population, with such a high incidence of contaminated EBM, this may not be the case. Further studies to compare EBM with premature infant formula in this population are required.

Contamination of breast milk obtained by manual expression and breast pumps in mothers of very low birthweight infants

The objective of this study was to compare the rates of bacterial contamination of expressed breast milk (EBM) obtained by manual expression and breast pumps in mothers of very low birthweight (VLBW) infants (<1501 g). This was a randomized, controlled study carried out on 28 mothers of such babies and 92 specimens of EBM were collected: 41 specimens from 13 mothers assigned to the manual group and 51 specimens from 15 mothers in the breast-pump group. EBM was cultured quantitatively by the Miles and Misra method. Breast milk expressed by breast pumps (86.3% or 44/51 specimens) had a significantly higher rate of bacterial contamination than milk expressed by the manual method (61.0% or 25/41 specimens) (P= 0.005). When breast milk was expressed in the hospital, there was no significant difference in contamination rates between the two methods. When breast milk was expressed at home, the rates of bacterial contamination by staphylococci (P= 0.003) and Gram-negative bacilli (P= 0.002) were significantly higher in the breast-pump group than the manual group. In conclusion, the rate of bacterial contamination of EBM of mothers of VLBW infants was high, especially when EBM was obtained by the breast pump or when expression was carried out at home.

How suitable is human milk for pre-term babies?

Optimum nutrition for pre-term babies can be defined as that which permits satisfactory growth and health in the short term, free from metabolic problems and infection, and in the long-term fulfillment of growth and neuro-developmental potential. This paper examines how human milk meets these requirements. The composition of the various types of human milk available to the pre-term baby is described along with their short-term influences on early growth, infection, necrotising enterocolitis and protein allergy and long-term effects on physical size and neuro-psychological function. The conclusion reached is that while admitting that human milk will often fail to meet some of the special nutritional needs of small pre-term babies, there is as yet insufficient evidence to discourage its feeding to these babies. Its antimicrobial properties, potential immunological benefits and possible advantages to body (and brain) composition justify its continued use, particularly in those parts of the world where risks of neonatal infection are high.