Effect of pH and Temperature on Biocontrol of Listeria monocytogenes in the North of

Listeria monocytogenes is a gram positive bacterium which through the contaminated foods causes Listeriosis in the human and abortion in livestock. This bacterium is widely available in the nature that the possibility of the food contamination is very high. Therefore, one of the possible ways of controlling the bacterium in the food and environment is the biocontrol of this bacterium. For this purpose bacteriophages might be used. To get rid of bacteria using phage depends on complex physical and chemical conditions. In this study we evaluated the effect of pH and temperature for 5 separate phages from lysogenic Listeria monocytogenes of aborted fetus on 4 strains of Listeria monocytogenes. The common bacteria in the ewes’ fetus abortion in different regions of Isfahan were investigated for two years. Lysogenic Listeria was inculcated in liquid medium. Five Listeria phages were extracted by a 0.45-μm filter. Then, 5 phages with a titer of 109 PFU/ml were selected and mixed together. Subsequently the selected mixtures were poured equally into 3 test tubes. The tubes’ pH s was adjusted to 4, 7, and 9. At temperatures 0◦ to 7◦C, 8◦ to 14◦C, 15◦ to 25◦C and 26◦ to 37◦C 2.5ml of each bacteriophages mixture with the same pH were mixed separately with 4 strains of Listeria monocytogenes and were incubated for 24 hours. Thereafter, a drop of each tube’s content was cultured on the blood agar. Lytic or lysogenic colonies of the bacterium were assessed. More than 2/3 of Listeria monocytogenes causing the abortion in the ewes are in lysogenic forms. The best pH for the attachment of the bacteriophages to the host bacterium is a neutral pH. To transform the bacterium into all pH s, a wide temperature range of (15◦C to 37◦C) was used. There was a significant difference (p = 0.0 5) between the formed lysogen from the bacterium having a 1<pH<7 and worth mentioning the bacterium form was transformed to lysogen forms. For biocontrol of Listeria monocytogenes in the environment and foods it is essential to know all the effective factors for the bacteriophages attachment to the Listeria monocytogenes and the conditions of the infected cells with the bacteriophages.