Abstract
Continuous monitoring of Listeria spp., particularly Listeria monocytogenes, in foods is a mandatory task for food safety and microbiology sectors. This study aimed to determine the prevalence and antimicrobial resistance patterns of L. monocytogenes in milk and dairy products retailed in Egypt. Furthermore, an experimental trial was conducted to investigate the antilisterial effects of some phytochemicals. A total of 200 samples (market raw milk, Kareish cheese, Damietta cheese, and plain yoghurt, 50 each) were collected and examined for detection of Listeria spp. The results revealed that 8, 12, 1, and 0 samples of market raw milk, Damietta cheese, Kareish cheese, and plain yoghurt were contaminated with Listeria spp., respectively. Antimicrobial sensitivity testing revealed that all L. monocytogenes isolates (15) were resistant to streptomycin and erythromycin. Molecular analysis revealed that 86.67% of L. monocytogenes harbored hylA virulent gene. Use of rosmarinic acid, ascorbic acid, thyme, and clove essential oils significantly ( P < 0.05 ) reduced L. monocytogenes growth in soft cheese—artificially contaminated with L. monocytogenes throughout a 4-week incubation period. In conclusion, strict hygienic conditions should be adopted during the preparation and distribution of dairy products. In addition, rosmarinic acid, ascorbic acid, clove, and thyme essential oils are good candidates as food preservatives with antilisterial activities.
Highlights
Contamination of milk and dairy products during processing and storage by food poisoning organisms is still a significant concern in dairy plants [1, 2]
The achieved results illustrated that 16%, 24%, and 2% of market raw milk, Damietta cheese, and Kariesh cheese were positive for Listeria spp., respectively, while Listeria spp. could not be recovered from yoghurt
Fifteen out of twenty-five isolates were confirmed as L. monocytogenes as 6, and 9 isolates were recovered from raw milk and Damietta cheese, respectively
Summary
Contamination of milk and dairy products during processing and storage by food poisoning organisms is still a significant concern in dairy plants [1, 2]. More than 250 various illnesses have been reported to be transmitted via the consumption of contaminated foods [3]. E pathogenicity of L. monocytogenes is attributed to its resistance to a wide range of environmental stressors. It can withstand chilling, thermal, and osmotic stressors [4]. L. monocytogenes was isolated from raw milk, cheese, and butter at 29.2%, 14.1%, and 4%, respectively, in Yazd, central Iran [5]. In Faisalabad, L. monocytogenes was detected in unheated dairy products such as raw milk at 17.78% and cheese at 5.55% [6]
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