Abstract
Among food-borne pathogens, Listeria monocytogenes continues to pose concerns to food business operators due to its capacity to form biofilm in processing environments. Ozone may be an eco-friendly technology to control microbial contaminations, but data concerning its effect on Listeria monocytogenes biofilm are still limited. In this study, the effect of gaseous ozone at 50 ppm on planktonic cells and biofilm of reference and food-related Listeria monocytogenes strains was evaluated. Ozone caused a reduction in microbial loads of 3.7 ± 0.4 and 3.9 ± 0.4 Log10 CFU/mL after 10 and 30 min, respectively. A complete inactivation of planktonic cells after 6 h of treatment was observed. Biofilm inhibition and eradication treatments (50 ppm, 6 h) resulted in a significant decrease of the biofilm biomass for 59% of the strains tested, whilst a slight dampening of live cell loads in the biofilm state was observed. In conclusion, gaseous ozone is not sufficient to completely counteract Listeria monocytogenes biofilm, but it may be useful as an additional tool to contrast Listeria monocytogenes free-living cells and to improve the existing sanitization procedures in food processing environments.
Highlights
Despite the regular application of sanitization plans by food business operators (FBO), bacterial biofilms are commonly found in food processing environments [1]
All L. monocytogenes were previously classified as biofilm-forming strains
Effects of O3 on L. monocytogenes Planktonic Cells A reduction of L. monocytogenes loads was observed after the short-term
Summary
Despite the regular application of sanitization plans by food business operators (FBO), bacterial biofilms are commonly found in food processing environments [1]. L. monocytogenes is a ubiquitous Gram-positive bacterium responsible for human listeriosis [4], one of the most serious food-borne diseases with the highest case fatality (17.6%) and which showed a significant increasing trend in the last years [5]. This pathogen can survive and grow in a wide range of foods, such as dairy, meat, seafood and vegetable products, with a high incidence especially in ready-to-eat (RTE) foods [6,7]. The processing environment is considered the most likely source of foodstuffs contamination by L. monocytogenes as the pathogen, when organized in biofilm, can persist for months or even years on surfaces representing a source of recurrent contaminations [8,9,10,11,12,13]
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