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Dr John May retired from human milk research
in 2006 and the last entry was made in December 2005. While this page and
the related tables will be kept online, they will only be updated sporadically in the future, if
at all.
Department of Microbiology
Human milk - Tables of the antimicrobial
factors and microbiological contaminants relevant to human milk banking
Over the last few years less continuing
interest has been taken in the factors present in human milk that are
shown to protect infants from microbial infections (particularly with
respiratory or gastrointestinal infection). More recent interest has
centred on the presence in human milk of new viruses.
Epidemiological studies have been important
in demonstrating that breast feeding clearly protects infants against
respiratory and gastointestinal infections, or decreases the severity
of these infections. Breastfeeding can also protect against otitis media
(middle ear infection), pneumonia, diarrhoea, necrotizing enterocolitis
and sepsis. The primary protective factors in breast milk are the
presence of specific antibody and anti-adhesion factors in human milk.
However, a variety of antimicrobial factors (antiviral, antibacterial and
antiparasitic) have been detected in human milk over the years (see
Tables 1,2,3). Most of these factors are
not destroyed by pasteurisation (62.5°C for 30 minutes) (see
Table 7).
Microbial contaminants
in human milk (Table 4) are rare, as
are the associated infant infections from the milk. However, some
contaminants, such as cytomegalovirus, are commonly transferred to
infants from seropositive mothers, fortunately without adverse effects
in infants. Human T-lymphotropic virus type 1 is transferred via human
milk in endemic regions, while human immunodeficiency virus type 1 is
also transferred through human milk - but is not the exclusive mode of
transmission to infants. Pasteurisation (62.5°C for 30 minutes) has
been shown to destroy all microbial contaminants in human milk (except
hepatitis B, which is fortunately not transferred through milk). With
the use of new detection technology, low levels of some viruses have
been found in human milk, but no epidemiological evidence suggest any
transfer of these viruses from mother-to-infant via human milk. If a
mother and infant have the same virus infection, and even in some cases
if that virus is detected in the mother's milk, the milk may not be the
source of the virus transmission to the infant (Table 4).
Detection of virus nucleic acid does not mean enveloped viruses, in
particular, are still infectious in human milk. Various bacterial
contaminants present in expressed human milk have caused infections
(Table 5). Infections of infants have
occasionally occurred from bacterial contaminants in dried milk formula
(Table 6). The effect of heat treatment and
storage of human milk on some the antimicrobial factors is given in
Table 7.
The Human Milk Banking Association of North
America guidelines are for the donors of human milk to have negative
blood tests for human immunodeficiency virus type 1 and 2; syphilis;
hepatitis B and C; and human T lymphotropic virus type 1 and 2.
Temporary exclusion may occur if the donor is infected with rubella, has
had an attenuated virus vaccine (ie. rubella), cold sore virus (herpes
simplex virus) or chickenpox virus (varicella-zoster), or mastitis. The
milk collected should contain no pathogenic bacteria (Staphylococcus
aureus, group B streptococci, Pseudomonas aeruginosa, and
lactose-fermenting coliforms), or no more than 100,000 colony forming
units per millilitre of normal skin bacteria and contain no viable
bacteria after pasteurisation.
Human milk contains a variety of potential anti-inflammatory
agents, immunomodulators and bioactive compounds that may influence
the incidence of diarrhoea in infected infants.
References
- J.K. Welsh and J.T. May (1979). Anti-infective properties of breast
milk. J. Pediatrics. 94, 1-9.
- J.T. May (1984). Anti-microbial properties and microbial
contaminants of breast milk - an update. Aust. Ped. J.
20, 265-269.
- J.T. May (1988). Microbial contaminants and anti-microbial
properties of human milk. Microbiol. Sciences. 5, 42-46.
- J.T. May (1994). Anti-microbial factors and microbial contaminants in
human milk. J. Ped. Child Health. 30, 470-475.
- J.T. May (1995). Human milk - anti-microbial and microbial
contaminants relevant to human milk banking. In Breast milk and
special case nurseries: problems and opportunities. ALCA press.
Melbourne. pp19-24.
- J.T. May (1997). Clinical significance and recent studies of the
anti-infective properties and infectious contaminants in breast milk,
In "Breast feeding: The natural advantage". NMAA press: Sydney.
pp. 138-144.
- A, Inglis, J.T. May and C. Lighton (1998). Fact sheets on the web:
A case study of the on-line dissemination of information on the anti-
infective properties of breast milk. Contemporary Nurse. 7,
91-97.
- J.T. May (1999). Breast milk and infection - a brief overview.
Breastfeeding review. 7, 25-27.
Related Information
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A summary of whether or not it is okay to breastfeed in the USA with infectious diseases, medication,
or environmental contaminants is given in
R.M. Lawrence and R.A. Lawrence (2001) Given the benefits of breastfeeding, what contraindications
exist? Pediatrics Clinics of North America. 48, 235-251.
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R. A. Lawrence (1997) A review of the medical benefits and contraindications to breastfeeding in the United States.
Maternal & Child Health Technical Information Bulletin
(Online http://www.ncemch.org/pubs/PDFs/breastfeedingTIB.pdf)
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A summary of whether it is okay to breastfeed with known infectious microbial contaminants is also
given in
C.A. Jones (2001) Maternal transmission of infectious pathogens in breast milk.
Journal of Paediatric and Child Health. 37, 576-582.
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Recommendations of whether it is okay to breastfeed with virus contaminants is
also given in
E.R. Stiehm and M.A.Keller (2001) Breast milk transmission of viral disease. Advances in
Nutrition Research. 10, 105-122.
Human milk on the world-wide web
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