Microbiological study of breast milk with special reference to its storage in milk bank.

L Deodhar, S Joshi 
 Department of Microbiology, L.T.M. Medical College, Sion, Bombay, Maharashtra.

Correspondence Address:
L Deodhar
Department of Microbiology, L.T.M. Medical College, Sion, Bombay, Maharashtra.

Full Text

::   Introduction

Human milk is unquestionably the best source of nutrition for infants[5]. It has unique components which include immunoglobulins and active leucocytes that enhance resistance to infection. In recent years, there has been an increased interest in providing milk via human milk banks to Premature children. However, clear guidelines for collection, processing or storing of human milk for therapeutic use have not been established, but milk samples showing bacterial counts more than 10,000 colony forming units per mililitre are unacceptable[1]. In the present paper, the results of microbiological study of breast milk are reported.

::   Material and method

Sixty-five samples of manually expressed breast milk were processed[2] in the laboratory and standard procedures, were used for identification of the organisms. Each sample was processed thrice-in fresh state, after heating at 100?C and five days after keeping in refrigerator at -20?C. This duration of 5 days was chosen on the presumption that milk in the milk bank will be consumed during the said period. Colony counts were also done wherever required. Smears from the fresh milk samples were stained by Gicmsa's staining and examined for inclusion bodies of cytomegalo virus (CMV). Besides the milk sample, serum sample of every mother was collected and studied for Hepatitis B surface antigen (HBsAg) by indirect Haem-agglutination method, (for this, kit supplied by Hoechst Pharmaceuticals was used) and human Immunodeficiency virus (HIV) antibodies by ELISA, using Well-cozyme HIV recombinant kit.

::   Results

Staphylococci (coagulase negative in 50 and coagulase positive in 12 samples) and diplitheroids were predominant organisms which were isolated while other organisms were Escherichiae R. coli, Klebsiella and Streptococcus viridans. Group B beta Streptococci (GBBS) were not isolated from any of the samples. Mixed flora was found in 23.3% of samples while 7(10.7%) samples were sterile. No bacteria were grown from any of the samples after heating the milk while in 33% of samples kept at refrigerator tcmperature (-20?C) same organisms were grown. Four fresh milk samples and 2 after freezing, showed colony counts more than 10,000 CFU/ml. CMV inclusion bodies were not detected in any milk sample; similarly none of the serum sample was positive for HBsAg or HIV antibodies.

::   Discussion

Out of 65 samples processed for bacteriological analysis, with the exception of 4 samples where E. coli and Klebsiella were grown, all identified bacteria have been reported as normal skin flora. All the milk samples showed a decrease in colony count after freezing and 50% of the samples showed a beneficial decrease in colony count from the unacceptable (> 10,000 CFU/ml) to the acceptable range (< 10,000 CFU/ml). Some and Barness[7] have reported isolation of Klebsiella in 2 and Pseudomonas in one sample while in all the remaining samples, bacteria were the same as those of skin flora. In their study, bacterial colony counts progressively decreased throughout the five day refrigeration period. Freezing is a better method compared to heating. It produces no appreciable loss of lactoferrin, lysozyme, IgG, IgA or C3[4]. Though Schreiner et al[6] have reported 2 cases of GBBS meningitis in breast fed infants whose mothers had GBBS of the same subtype isolated from their breast milk, we did not get any sample positive for GBBS.

Human milk contains Cytomegalo virus (CMV) in 10-17% of mixed unselected publications[3]. Infants born to mothers without immunity and fed on banked human milk that includes samples from these virus excreting donors get exposed to the virus and develop serious form of infection, as they do not have protection via trans placental antibody[3]. In the present study, CMV inclusions were not detected in any sample, though culturing of the virus was not done.

Though HbsAg is found in breast milk, its transmission by this route has not been documented. The possibility that HIV could be transmitted through breast-feeding or breast milk is supported by a report that HIV can be cultured from breast milk of mothers who are themselves infected. At present the risk of HIV infection from mothers to infants through breast feeding has not yet been defined, but if such transmission occurs, the relative contribution of this route is very small - as compared with in caters or intrapartum transmissions[8]. In general for identifying HIV infected infant, the persistence of HIV antibodies beyond the first 15 months of life is important.

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