The effect of DNasel enzyme on food pathogens subjected to different food processing treatments.

Detection of pathogens in contaminated food products by PCR can result in false-positive results due to amplification of DNA from non-viable cells. DNase treated DNA polymerase chain reaction (DTD-PCR) has been attempted to eliminate such contaminating DNAs from nonviable cells prior to the isolation of template DNA, and to improve the overall fidelity of such detection methods. The main objective of this work was to determine the effect of different DNasel enzyme treatments on the DNA present in viable and non-viable cells that were subjected to different food processing treatments. Hypothesis was based on the use of DNasel for the differentiation of viable and non-viable cells of food borne pathogens. The effect was observed both on gram positive (Listeria monocytogenes) and gram negative cells (Escherichia coli 0157:H7) of food pathogens after subjecting the cells to a range of heat, cold and chemical treatments. The

penetrability of DNasel enzyme into the cells and the subsequent digestion of DNA residing in the cell are based on the type and extent of DNasel treatment and the gram character of the cells. The results indicate the possibility of using DNasel to distinguish between viable and non-viable cells that were produced by heat treatments and some chemical treatments (ethyl alcohol and sodium hypochlorite). However, this cannot be applied for differentiation between viable and non-viable cells produced by cold treatments and sodium chloride treatments. Overall results confirmed the potential of developing DTD-PCR to differentiate the viable cells from the non-viable cells of test organisms after subjecting them to heat treatment, ethyl alcohol treatment and sodium hypochlorite treatment.

Keywords: Detection, DNasel, food borne pathogens, PCR

J. NatnScLFoundation Sri Lanka 2007 35(3): 167-173

doi: 10.4038/jnsfsr.v35i3.2015