An active fraction extracted from Lactobacillus acidophilus La5 cell-free spent medium (LAla-5AF) was incorporated in a dairy matrix and tested to assess its antivirulent effect against enterohemorrhagic Escherichia coli (EHEC). Mice in experimental groups were fed for 4 days with yogurt supplemented with LAla-5AF. On the fifth day, mice were challenged with a single dose (10(7) CFU per mouse) of E. coli O157:H7. The clinical manifestations of the infection were significantly less severe in mice fed the yogurt supplemented with LAla-5AF. EHEC attachment and colonization was attenuated by LAla-5AF. Tumor necrosis factor alpha production was down-regulated, which might indicate a protective effect in the kidney during EHEC infection. To investigate the mechanisms associated with the in vivo effects observed, LAla-5AF was tested by reverse transcription real-time PCR to confirm its effects on the expression of several virulence genes of EHEC O157. The results showed that these fractions were able to down-regulate several virulence genes of EHEC, including stxB2, qseA, luxS, tir, ler, eaeA, and hlyB.

Listeria monocytogenes contaminated processing equipment and the general packing environment have been implicated in deadly foodborne listeriosis outbreaks, highlighting the significance of proper sanitization and disinfection of food contact surfaces. This study aims to comprehensively evaluate antimicrobial efficacy of commercially available, economical sanitizers at practical concentrations against L. monocytogenes biofilm formed on polystyrene surfaces under different conditions. Ozonated water 1-min treatment at 1.0, 2.0, and 4.0 ppm resulted in ∼0.9, 3.4, and 4.1 log reduction of L. monocytogenes single strain biofilm grown on polystyrene surfaces, respectively. However, its efficacy was dramatically diminished in multi-strain L. monocytogenes biofilm and was further compromised by aged biofilm and in the presence of organic matter. Quaternary ammonium compounds (QAC) at 100/400 ppm, chlorine at 100/200 ppm, chlorine dioxide at 2.5/5.0 ppm and peroxyacetic acid (PAA) at 80/160 ppm resulted in 2.4/3.6, 2.0/3.1, 2.4/3.8, and 3.6/4.8 log reduction of L. monocytogenes single strain biofilm, respectively. Antimicrobial efficacies of all tested sanitizers against 7-day-old biofilm were much lower when compared to 2-day-old biofilm, with PAA being the least influenced by the age of the biofilm. Organic matter conditioning with diluted milk or apple juice dramatically impacted the antimicrobial efficacy of all sanitizers. PAA treatment of 1 min at 160–200 ppm resulted in a 3.2–3.5 log reduction against 7-day-old biofilm in the presence of organic matter, thus showing its effectiveness in eradicating L. monocytogenes biofilm on polystyrene surface. Collectively, data highlight the importance of timely and thoroughly cleaning food contact surfaces before disinfection and provides practical information and guidance for the food industry in selecting the most effective sanitizer in their sanitizing regimes to eliminate L. monocytogenes biofilm.

The objectives of this study were to assess the microbiological quality of domiati cheese and to evaluate the capacity of Lactobacillus acidophilus La-5 and Bifidobacterium longum ATCC15707 to inhibit the growth of Staphylococcus aureus and Escherichia coli O157:H7 during manufacture and storage of domiati cheese. The results of the microbial investigation indicated poor microbiological quality of cheese samples, the microbiological parameters recorded higher values than admissible levels. Domiati cheese produced from milk artificially contaminated with S. aureus and E. coli O157:H7 was used as a model for studying the antibacterial activity of L. acidophilus La-5 and B. longum ATCC15707 against these pathogens. The results obtained in this study indicated the remarkable effect of L. acidophilus La-5 and B. longum ATCC15707 in preventing survival of S. aureus and E. coli O157:H7 during cheese storage. The inactivation rate was more pronounced with S. aureus than E. coli O157:H7 and it was dependent on probiotic strain. L. acidophilus inactivation was significantly higher (P value < 0.05) than that attained with B. longum. Survival of probiotic bacteria in domiati cheese was satisfactory. PRACTICAL APPLICATIONSThe microbial contamination of domiati cheese represents not only spoilage of the product but also constitutes a high risk to human health. The probiotic bacteria have the ability to improve the microbiological quality and safety of domiati cheese. Survival of both Lactobacillus acidophilus La-5 and Bifidobacterium longum ATCC15707 in domiati cheese was satisfactory, which indicate that the domiati cheese would be a suitable vehicle for the delivery of probiotic bacteria.

Food adulteration is an act for debasing the quality of food with an admixture or through the substitution of inferior substances or by removing some invaluable ingredients from the food product. A total of 150 random samples of milk and some milk products (30 samples from each of raw cow's milk, UHT milk, Thick cream, Imported butter, Farmers Butter) were collected from different regions of Beni-Seuf city, Egypt and subjected to chemical analysis for detection of various adulterants. This study proved that the most prominent types of adulteration were addition of water, partial skimming or both. On the other hand, preservatives and commercial additives were absent in all milk and cream samples except gelatin which was found in 76.6% of cream samples. The mean iodine number of the imported butter and farmers butter samples ranged from 39.93 ±1.173 and 37.43 ± 0.718, respectively. All examined butter samples were free from cotton seed oil and starch while sesame oil was present in a percentage of 56.67% and 36.67% in the examined imported and farmers butter, respectively. In conclusion this qualitative analysis which has unfolded proved that some of milk and milk product procured did not conform to the legal standard and adulterated with some adulterants which decrease their nutritive value and may cause public health hazard.

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