Abstract
The present study aimed to determine the antibacterial activity of lactic acid bacteria metabolites against Listeria monocytogenes which was isolated from some foods in local markets of Erbil and Koya cities; 225 food samples were examined for the presence of Listeria species particularly L. monocytogenes from October 2010 to March 2011. The studied samples included 70 samples of raw chicken meat, 55 samples of raw milk, 50 samples of cheese and 50 samples of raw red meat. According to motility test, hemolysin production, sugar fermentation test, 8 isolates of L. monocytogenes were identified, 1 (2 %) isolate from cheese, 2 (4 %) isolates from red meat and 5 (7.3 %) isolates from chicken meat. The percentages of contaminated foods for Listeria species from chicken meat, raw milk, cheese and red meat were 20, 9, 20 and 22% respectively. With respect to the biocontrolling attempt, the effect of cell free extract (CFE) of lactic acid bacteria (LBA) which is considered as safe against isolated L. monocytogene was used as biocontrolling agent. The CFE of lactic acid bacteria which isolated from local dairy products, was tested for its controlling ability by agar diffusion method, the CFE showed inhibition zone from (15-23 mm) in diameter. Also the minimum inhibitory concentration MIC of CFE was determined at three additive percentages (0.5, 1.0 and 1.5ml to 10 ml of nutrient broth), the inhibition percentage ranged from (28.75 - 48.97) at (0.5 %), (52.13-95.55) at (1 %) and (82.93 -98.15) at (1.5 %) additive percentage of CFE of LAB.
Highlights
التأثير التثبيطي للنواتج الايضية لبكتريا حامض اللبنيك على نمو بكتريا Listeria monocytogenesالمعزولة من بعض مصادر الأغذية
Listeriosis is among the most common bacterial food-borne pathogens worldwide and the disease emerging as an important food –borne pathogen of public health concern (Chukwu et al, 2007) L. monocytogenes causes listeriosis which can be a non-invasive disease, but primarily occurs in an invasive form
Biocontrol of L. monocytogenes in food is achieved by adding bacteriocin-producing microorganism, bacteriocin-containing fermentate, bacteriocin crude extract, or purified bacteriocin, lactic fermentations are believed to be the oldest preservation known to human kind (Ross et al, 2000)
Summary
التأثير التثبيطي للنواتج الايضية لبكتريا حامض اللبنيك على نمو بكتريا Listeria monocytogenesالمعزولة من بعض مصادر الأغذية. Biocontrol of L. monocytogenes in food is achieved by adding bacteriocin-producing microorganism, bacteriocin-containing fermentate, bacteriocin crude extract, or purified bacteriocin , lactic fermentations are believed to be the oldest preservation known to human kind (Ross et al, 2000) Such an application i.e., the antimicrobial properties of lactic acid bacteria due to their ability to produce substance as a natural competitive means to overcome other microorganisms sharing the same ecological niche (Pattnaik et al, 2005) Bacteria that produce antilisterial bacteriocins include strains of lactic acid bacteria, lactic acid bacteria produce various types of compounds such as lactic acid, acetic acid, formic acid, phenyllactic acid, diacetyl, acetoin, reuterin, reutericyclin, cyclic dipeptides, bacteriocins and other inhibitory proteinaceous compounds, 3-hydroxy fatty acids and hydrogen peroxide (Schnurer and Magnusson, 2005; Francoise, 2010). The aims of this present study were: (1) to evaluate food in local market of Erbil and Koya cities for the presence of Listeria especially L.monocyogenes (2) to test the antimicrobial activity of LAB isolated from ‘‘local dairy products’’ against L. monocytogenes
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