Efficacy of Some Probiotics Bacteria Against Staphylococcus aureus food borne pathogen

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Omyma A. Awadallah, Hassan M. Emara, Ahmed Nasr

Abstract

The food industry has devoted intense research efforts to counteract the emergence of outbreaks caused by foodborne pathogenic bacteria. The aim of this study was to isolate, identify and evaluate the in vitro antagonistic activities of lactic acid bacteria isolated (probiotic) from the Raw milk and Yoghurt Samples in Egypt on foodborne pathogenic microorganism. (Staphylococcus aureus). Different biochemical tests were performed to identify isolated bacteria. Then, cell-free supernatant (CFS) was prepared from MRS culture and used in an antimicrobial assay that was performed by agar diffusion method. The effects of pH, and temperature, on antimicrobial activity were evaluated in the same test.. Simultaneously, the effects of lactic acid bacteria on antimicrobial materials production were also evaluated from Raw milk and Yoghurt. A total of 5 lactic acid bacteria were isolated; among them, one lactic acid bacteria(L5), belonging to the Lactobacillus plantarum. The cell-free supernatant of those five  isolates exhibited the highest antibacterial activity, with the inhibition zone was 22 mm diameter l effect against tested foodborne pathogenic bacteria . Both these cultures were subjected to Biochemical and molecular identification using 16S rRNA gene sequencing highlighted the presence of species: Lactiplantibacillus  plantarum, isolate ( Size 1200pb acc. no. LC727688) showed a similarity ˃ 98% to L. plantarum (acc.no.MT152629.1) and  the food borne pathogenic S.aureus( Size 1200pb acc. no. LC727687)  showed a similarity ˃ 99% to S. aureus(acc. no. LC606406.1)  . It maintained/retained antimicrobial activity in a wide range of pH 3.0–11, and temperature degree  from 15-45°C on MRS medium . CFS exhibited antibacterial activity against S. aureus, as confirmed by the increase in absorbance value between 0.312 - 0.821 and  0.422-0.821 OD600-nm respectively .The highest activity were obtained at pH6 and temperature degree 30°C. Also, concentrations of  bile salts and Sodium chloride. (gm /100ml) 1 and 0.6 respectively. Identification of the antimicrobial substances assay produced from L. plantarum and the SDS–PAGE analysis were able to produce bacteriocin with molecular weight 3.73 KDa . Evaluation the effect of  Potasium sorbate used as food preservative, individually and incombination with the anitimicrobial compound produced from L.plantarum under the optimized conditions showed significant differences in most of food processing industries inhibiting growth of pathogenic bacteria in foods and enhance extension of shelf life of food products.                                                                                                     


 


 

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Omyma A. Awadallah, Hassan M. Emara, Ahmed Nasr