Microbiome convergence following sanitizer treatment and identification of sanitizer resistant species from spinach and lettuce rinse water

Authors: GU, GANYU - Virginia Tech; OTTESEN, ANDREA - Food And Drug Administration(FDA); BOLTEN, SAMANTHA - Orise Fellow; Luo, Yaguang - Sunny; RIDEOUT, STEVEN - Virginia Tech; Nou, Xiangwu

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2019
Publication Date: 11/23/2019
Citation: Gu, G., Ottesen, A., Bolten, S., Luo, Y., Rideout, S., Nou, X. 2019. Microbiome convergence following sanitizer treatment and identification of sanitizer resistant species from spinach and lettuce rinse water. International Journal of Food Microbiology. 318:0168. https://doi.org/10.1016/j.ijfoodmicro.2019.108458.
DOI: https://doi.org/10.1016/j.ijfoodmicro.2019.108458

Interpretive Summary: Fresh produce can harbor large and diverse populations of microorganisms, including those that are potentially able to cause foodborne infections. These microorganisms are released into water during washing and inactivated by chemicals applied as sanitizers with varying efficacy. In collaboration with FDA, USDA-ARS scientists determined the changes in the collective bacterial species (microbiome) following treatments with chlorine and peracetic acid sanitizers by DNA sequencing, and determined a sanitizer resistant microbiome composed of Bacillus and other spore forming bacteria, among other species. The information is useful for understanding the bacterial inactivation dynamics for the produce industry and researchers.

Technical Abstract: Fresh produce, source of multiple foodborne outbreaks, harbors large quantities of diverse microbes, which are partially released into wash water during processing. However, the dynamics of bacterial communities in wash water during produce processing is unclear. In this study, we investigated the effect of chlorine (FC) and peracetic acid (PAA) on the microbiome dynamics in spinach and romaine lettuce rinse water. Treatments with increasing concentrations of sanitizers resulted in convergence of distinct microbiomes. The resultant sanitizer resistant microbiome showed dominant presence by Bacillus spp., Arthrobacter psychrolactophilus, Cupriavidus sp., and Ralstonia sp.. Most of the FC and PAA resistant bacteria isolated from spinach and lettuce rinse water after sanitation were gram positive spore forming species including Bacillus and Brevibacterium spp., while several PAA resistant Pseudomonas spp. were also isolated from lettuce rinse water. Inoculation of foodborne pathogens altered the shift in bacterial communities in spinach rinse water under PAA treatment, but not in lettuce rinse water or FC treated samples. These inoculated foodborne pathogens were not isolated among the sanitizer resistant strains.