Short CommunicationBiofilm of Escherichia coli O157:H7 on cantaloupe surface is resistant to lauroyl arginate ethyl and sodium hypochlorite

- Biofilm formation by E. coli O157:H7 on cantaloupe surface was observed using Cryo-SEM.
- E. coli O157:H7 was able to form biofilm within 12 h at room temperature.
- Biofilm was associated with high bacterial resistance to lauroyl arginate ethyl and sodium hypochlorite.

Biofilms formed by Escherichia coli O157:H7 on cantaloupe rind were characterized in this study. Cantaloupe rind pieces inoculated with E. coli O157:H7 B6-914 was sampled after 2, 12, and 24 h incubation for imaging with cryo-scanning electron microscopy (Cryo-SEM) or treating with lauroyl arginate ethyl (LAE) or sodium hypochlorite (SHC). Cryo-SEM images showed that E. coli O157:H7 formed a biofilm within 12 h on the rind surface. For rind samples treated with LAE or SHC, the residual cell counts were significantly different (p < 0.05) between 2 and 12 h incubation, and between 2 and 24 h of incubation. For the 2 h incubation samples, E. coli O157:H7 was undetectable (> 5-log reduction) after treatment with 2000 μg/mL of LAE or SHC. In contrast, for 12 h incubation samples, 2000 μg/mL of LAE or SHC could only achieve 1.74 or 1.86-log reduction, respectively. The study showed the low efficacy of LAE and SHC on cantaloupe rind surface to reduce the E. coli biofilm, suggesting the needs for cantaloupe cleaning methods beyond washing with conventional antimicrobial agents.