Pathogen biofilm formation on cantaloupe surface and its impact on the antibacterial effect of lauroyl arginate ethyl

Pathogen biofilm at fruit surface may pose a particular risk to food safety. In this study, the biofllms of Listeria monocytogenes V7 and Salmonella enterica serovar Typhimurium ATCC 13311 on cantaloupe fruit surface were visualized; and the resistance of biofllms against lauroyl arginate ethyl (LAE, an antibacterial compound) was evaluated. Each bacterium was inoculated on isolated cantaloupe rind surfaces at 10(5)-10(6) CFU/cm(2) and after incubation for 2, 12, 24, and 48 h, the surfaces were imaged using cryo-scanning electron microscopy (Cryo-SEM). The images showed that both pathogens formed biofllms on rind surfaces, with S. Typhimurium forming biofilm in 12 h and L monocytogenes cells starting to aggregate in 2 h. For the inoculated rind surfaces treated with LAE, the cell counts were affected by both the incubation time and LAE concentration. For rind surface with 2 h incubation of S. Typhimurium, 400 and 800 mu g/mL LAE was able to achieve >2.00 log reduction; however, 12 h incubation required 1600 and 2000 mu g/mL LAE for >2.00 log reduction. In contrast, even the highest LAE concentration (2000 mu g/mL) was unable to cause 1.00 log reduction for L monocytogenes regardless the incubation time applied. The results showed that the biofllms of both bacteria substantially reduced LAE efficacy, and that the biofilm of L monocytogenes was more resistant than that of S. Typhimurium. (C) 2016 Elsevier Ltd. All rights reserved.