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Occupational Health - Public Health Poster Session






Abstract

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EFFECTS OF STORAGE ON THE PHYSICOCHEMICAL AND ANTI-BACTERIAL PROPERTIES OF HUMAN BREAST-MILK


Contact Person: Michael O Ogundele (mogundel@yahoo.com)


Introduction

There is a conclusive body of evidence that breast-feeding protects the infant against a wide range of infectious and other diseases (1,2). Efforts have been directed in the past few years to identify various immune-active substances in the human breast-milk (HBM) which account for the observed protective effects. These include specific anti-viral antibodies, anti-bacterial antibodies, non-specific IgG, IgA, IgM, lactoferrin, lysozyme, different cytokines, lymphocytes, polymorphonuclear leucocytes, and macrophages (3-10). Only individual component proteins of the complement (C) system in the human breast milk (HBM) have been assayed so far, without any indication of their physiological significance (11-13).

The need to store breast-milk for at least limited periods of time is unavoidable especially in a neonatal unit taking care of sick and pre-term new-born infants and increasingly in several homes. Increasing numbers of mothers, even in the developing countries, have to go out to work soon after delivery (14), who still want to exclusively breastfeed their children. For the pre-term neonates, who are particularly susceptible to infection, and often require prolonged intensive care in the hospital, the mothers milk may still be inadequate for the first few days, due to an inadequate suckling stimulation by the weak neonate. With an increased risk of bacterial contamination associated with unhygienic preparation and improper storage of artificial formula feeds, many such pre-term babies may need to be fed with donor breast-milk that is aseptically stored in the hospital, with attendant transportation problems (15). Some small-for date babies could need to be given additional milk, other babies may be excessively hungry, while others may have mothers who are unwell after delivery and unable to express breast-milk e.g. after caesarean section.

The greatest fear that has greatly hindered the prospects in-vitro storage of breast-milk for any considerable period of time is the possibility of bacterial contamination and growth of infectious pathogens in the stored milk, thereby rendering them unsafe for human consumption.

Most contamination of stored milk is said to occur at collection (16). Freshly collected breast-milk is rarely sterile and normally contains bacteria originating from the maternal skin and nipple duct microflora. It also sometimes contain potential pathogens, which however seem to produce no ill effects on the suckling infant (17-19). Pooled human milk is known to contain potential pathogenic organisms, though the ability of these organisms to cause infection is uncertain, and probably minimal. This would however be no excuse for permitting heavy bacterial contamination, which would be undesirable since some of these pathogens produce lipases, proteases and decarboxylases, capable of damaging anti-microbial proteins or convert free amino acids into toxic amines (20). Other factors associated with increased bacterial contamination of expressed breast-milk is undue delay of the initiation of milk expression in the postpartum period (21).

Many bacteriological studies have concentrated on examining the changes occurring in the breast-milk stored by refrigeration. From studies conducted in tropical conditions, unheated breast-milk could be stored for at least 8 hours at room temperature, and up to 24 hours at +4C in the refrigerator, before bacterial multiplication occurs beyond unacceptable levels. The results showed that most of the milk samples had significant drop in the level of bacterial colony counts during the storage period (17,18). This is in sharp contrast to cows milk formula which showed significant increases in the bacterial counts during 6 hours of storage at both room temperature and refrigeration (17). Studies from the temperate climatic condition showed that breast-milk stored for up to 48 hours in the refrigerator is bacteriologically acceptable (23). The bacterial count in the refrigerated milk was also found to decrease after 3 days of storage (19,24). Similar decreases in the bacterial colony counts were also demonstrated in human milk after 5 days freezing at -20C (23). Freezing has been claimed not to denature milk proteins but significantly kills the milk cells (19). A number of studies which were conducted to examine the effects of different storage methods specifically on pH changes and complement-mediated bacteriolysis as well as adhesion of milk fat globule membrane (MFGM) to suspended bacteria.

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Ogundele, M.O.; (1998). EFFECTS OF STORAGE ON THE PHYSICOCHEMICAL AND ANTI-BACTERIAL PROPERTIES OF HUMAN BREAST-MILK. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/occupational/ogundele0300/index.html
© 1998 Author(s) Hold Copyright