Malaysian Applied Biology Journal

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Malays. Appl. Biol. (1997) 26(1): 19-23


SON RADU*1, RUSUL, G.2, KARIM, M. I. A.1 and YUSOFF, K.3

1 Department of Biotechnology, 2 Department of Food Science, 3 Department of Biochemistry and Microbiology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia


Several studies have demonstrated the usefulness of recombinant DNA probes for identifying enterotoxigenic Escherichia coli (ETEC). In this study, an enzyme-labelled oligonucleotide probe for an ETEC heat-stable toxin (ST) gene was compared with the standard suckling mouse assay for their ability to identify ETEC in a group of adults experiencing acute episode of diarrhoea. The ST probe hybridized with 48% (10 of 21) of the E. coli colonies tested, whereas 38% (8 of 21) were positive by the suckling mouse bioassay. For the patient samples tested, three ST-probe positive were negative for suckling mouse bioassay. Plasmid DNA among the 10 ST-probe positive E. coli strains ranging in size between 1.6 kb to 35 kb were shown to hybridize with the biotinylated ST DNA probe. These results indicate that the biotinylated enterotoxin probe is useful in the diagnosis of enterotoxigenic E. coli strains by colony hybridization, and that ETEC play a modest role in the aetiology of diarrhoea among the group of patients examined.


Beberapa kajian telah menunjukkan penggunaan prob DNA untuk mengenalpasti Escherichia coli enterotoksigenik (ETEC). Dalam kajian ini, prob oligonukleotid yang dilabel dengan enzim untuk gen toksin tahan haba ETEC (ST) dibandingkan dengan 'suckling mouse assay' bagi melihat keberkesanan mereka mengesan ETEC dalam sekumpulan orang dewasa yang mengalami cirit birit. Prob ST berhibrid dengan 48% (10 dari 21) koloni E. coli yang diuji, manakala 38% (8 dari 21) adalah positif dengan cara 'suckling mouse assay'. Dari sampel yang diuji, tiga yang prob-positif adalah negatif dengan 'suckling mouse bioassay'. Plasmid DNA dikalangan 10 asingan E. coli yang prob-positif bersaiz antara 1.6 kb dan 35 kb menghibrid kepada prob ST DNA yang dilabelkan dengan biotin. Keputusan yang diperolehi menunjukkan bahawa prob snterotoksin yang dilabelkan dengan biotin amat berguna dalam pengesanan asingan E. coli dengan cara hibridisasi koloni, dan juga ETEC memainkan peranan dalam kejadian cirit birit dikalangan pesakit yang diuji.

Key words: Biotinylated DNA probe, enterotoxigenic E. coli, heat-stable enterotoxin, suckling mouse assay


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