Detection of Enterobacter sakazakii in South African food products
Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2005. === It is estimated by the World Health Organisation (WHO) that thousands of millions of cases of foodborne diseases occur world–wide every year. Enterobacter sakazakii is a member of the family Enterobacteriaceae and has been...
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2008
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ndltd-netd.ac.za-oai-union.ndltd.org-sun-oai-scholar.sun.ac.za-10019.1-30972016-01-29T04:03:08Z Detection of Enterobacter sakazakii in South African food products Kemp, Francisca Witthuhn, R. C. Britz, T. J. University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science. Dissertations -- Food science Theses -- Food science Enterobacter Enterobacteriaceae Infant formulas -- Contamination Polymerase chain reaction Infant formula industry -- South Africa Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2005. It is estimated by the World Health Organisation (WHO) that thousands of millions of cases of foodborne diseases occur world–wide every year. Enterobacter sakazakii is a member of the family Enterobacteriaceae and has been identified as an occasional contaminant of powdered infant formula milk (IFM). Enterobacter sakazakii is an opportunistic emerging pathogen and has the ability to cause a severe form of neonatal meningitis. This organism was referred to as “yellow pigmented Enterobacter cloacae” until 1980 after which it was renamed as E. sakazakii. The current method for the detection of E. sakazakii is very time consuming and includes pre–enrichment, enrichment in Enterobacteriaceae enrichment broth, subsequent plating on violet red bile glucose agar and subculturing on tryptone soy agar. In this study a polymerase chain reaction (PCR) method was developed for the identification of the presence of E. sakazakii in infant food products. A part of the 16S ribosomal RNA (rRNA) gene from E. sakazakii was amplified using the primer pair Esak2 and Esak3. An internal amplification control (IAC) was constructed as part of the PCR detection method. The 850 base pair (bp) E. sakazakii PCR product was digested with AluI and the two fragments containing the primer binding sites were ligated, resulting in a 240 bp IAC. During this study a positive band for both the target DNA (850 bp) and the IAC (240 bp) was simultaneously observed when the IAC was added to the PCR mixture at a concentration of 0.72 pg.ml-1. Four of 22 South African food products tested positive for the presence of E. sakazakii, using both the PCR and recommended culturing methods. The PCR method was used successfully for the detection of E. sakazakii within three days and thus provides a possible alternative and improvement on the recommended current culturing methods. Other microorganisms present in the products tested included Escherichia coli, Klebsiella pneumoniae, Raoultella terrigena (“Klebsiella terrigena”) and Chryseomonas luteola. Since E. sakazakii is usually present in low numbers in food products, it is possible that these few cells are unevenly distributed in the products, making it important to take multiple samples when evaluating IFM and thereby ensuring that even low numbers of this pathogen are detected. 2008-07-15T13:03:13Z 2010-06-01T09:06:12Z 2008-07-15T13:03:13Z 2010-06-01T09:06:12Z 2005-12 Thesis http://hdl.handle.net/10019.1/3097 en University of Stellenbosch Stellenbosch : University of Stellenbosch |
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Dissertations -- Food science Theses -- Food science Enterobacter Enterobacteriaceae Infant formulas -- Contamination Polymerase chain reaction Infant formula industry -- South Africa |
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Dissertations -- Food science Theses -- Food science Enterobacter Enterobacteriaceae Infant formulas -- Contamination Polymerase chain reaction Infant formula industry -- South Africa Kemp, Francisca Detection of Enterobacter sakazakii in South African food products |
description |
Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2005. === It is estimated by the World Health Organisation (WHO) that thousands of millions of
cases of foodborne diseases occur world–wide every year. Enterobacter sakazakii is
a member of the family Enterobacteriaceae and has been identified as an occasional
contaminant of powdered infant formula milk (IFM). Enterobacter sakazakii is an
opportunistic emerging pathogen and has the ability to cause a severe form of
neonatal meningitis. This organism was referred to as “yellow pigmented
Enterobacter cloacae” until 1980 after which it was renamed as E. sakazakii.
The current method for the detection of E. sakazakii is very time consuming
and includes pre–enrichment, enrichment in Enterobacteriaceae enrichment broth,
subsequent plating on violet red bile glucose agar and subculturing on tryptone soy
agar. In this study a polymerase chain reaction (PCR) method was developed for the
identification of the presence of E. sakazakii in infant food products. A part of the 16S
ribosomal RNA (rRNA) gene from E. sakazakii was amplified using the primer pair
Esak2 and Esak3.
An internal amplification control (IAC) was constructed as part of the PCR
detection method. The 850 base pair (bp) E. sakazakii PCR product was digested
with AluI and the two fragments containing the primer binding sites were ligated,
resulting in a 240 bp IAC. During this study a positive band for both the target DNA
(850 bp) and the IAC (240 bp) was simultaneously observed when the IAC was
added to the PCR mixture at a concentration of 0.72 pg.ml-1.
Four of 22 South African food products tested positive for the presence of
E. sakazakii, using both the PCR and recommended culturing methods. The PCR
method was used successfully for the detection of E. sakazakii within three days and
thus provides a possible alternative and improvement on the recommended current
culturing methods. Other microorganisms present in the products tested included
Escherichia coli, Klebsiella pneumoniae, Raoultella terrigena (“Klebsiella terrigena”)
and Chryseomonas luteola.
Since E. sakazakii is usually present in low numbers in food products, it is
possible that these few cells are unevenly distributed in the products, making it important to take multiple samples when evaluating IFM and thereby ensuring that
even low numbers of this pathogen are detected. |
author2 |
Witthuhn, R. C. |
author_facet |
Witthuhn, R. C. Kemp, Francisca |
author |
Kemp, Francisca |
author_sort |
Kemp, Francisca |
title |
Detection of Enterobacter sakazakii in South African food products |
title_short |
Detection of Enterobacter sakazakii in South African food products |
title_full |
Detection of Enterobacter sakazakii in South African food products |
title_fullStr |
Detection of Enterobacter sakazakii in South African food products |
title_full_unstemmed |
Detection of Enterobacter sakazakii in South African food products |
title_sort |
detection of enterobacter sakazakii in south african food products |
publisher |
Stellenbosch : University of Stellenbosch |
publishDate |
2008 |
url |
http://hdl.handle.net/10019.1/3097 |
work_keys_str_mv |
AT kempfrancisca detectionofenterobactersakazakiiinsouthafricanfoodproducts |
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1718164097661403136 |