ABSTRACT
Aims@#This study was designed to evaluate the effectiveness of the synthesised carvacrol loaded chitosan nanoparticles (CLCNPs) on the growing and pre-formed biofilms of Listeria monocytogenes isolated from slaughterhouses.@*Methodology and results@#The swab samples were collected from knives, hocks and cutting tables representing slaughterhouses meat contact surfaces (MCS), while those samples from walls and floors represent slaughterhouses meat non-contact surfaces (MNCS). The bacteriological analysis revealed the existence of L. monocytogenes with a prevalence rate of 3.3, 10 and 6.7% for knives, hocks and cutting tables, respectively and 2.2 and 6.6% for walls and floors, respectively. The isolates L. monocytogenes were assayed for biofilm production by the crystal violet binding assay method. Among the 10 L. monocytogenes isolates, 10%, 50% and 30% of the isolates were found to be strong, moderate and weak biofilm producers, respectively. The activities of carvacrol, chitosan nanoparticles (NPs) and CLCNPs against the only strong biofilm producer strain of L. monocytogenes were tested by microtiter plate assay. The minimum inhibitory concentrations (MIC) values were 3.75 mg/mL for CAR, 5 mg/mL for chitosan NPs and 0.62 mg/mL for CLCNPs. CLCNPs inhibit the produced biofilm by 35.79, 73.37 and 77.76%, when 0.5 MIC, 1 MIC and 2 MIC were used, respectively. Furthermore, the pre-formed L. monocytogenes biofilms were significantly reduced from 1.01 (control) OD570 to 0.40 and 0.29 OD570 by applying 2 MIC and 4 MIC doses, respectively.@*Conclusion, significance and impact of study@#The data generated is promising to develop bio-green disinfectants to inhibit biofilm formation by L. monocytogenes in the food processing environment and control its adverse effects for consumers.