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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #371199

Research Project: Ecology and Detection of Human Pathogens in the Produce Production Continuum

Location: Produce Safety and Microbiology Research

Title: Effects of lyophilization on the stability of bacteriophages against different serogroups of Shiga toxin-producing Escherichia coli

Author
item LAVENBURG, VALERIE - Volunteer
item Liao, Yen-Te
item Salvador, Alexandra
item Hsu, Angeline
item Harden, Leslie - Les
item Wu, Vivian

Submitted to: Cryobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2020
Publication Date: 9/28/2020
Citation: Lavenburg, V., Liao, Y., Salvador, A., Hsu, A.L., Harden, L.A., Wu, V.C. 2020. Effects of lyophilization on the stability of bacteriophages against different serogroups of Shiga toxin-producing Escherichia coli. Cryobiology. 96:85-91. https://doi.org/10.1016/j.cryobiol.2020.07.012.
DOI: https://doi.org/10.1016/j.cryobiol.2020.07.012

Interpretive Summary: Lyophilization (or freeze-drying) has been widely used to preserve numerous microorganisms. However, little information is found regarding the effects of the freeze-drying process on the stability of the phages that infect Shiga toxin-producing E. coli (STEC) strains. Seven phages, lytic against seven different types of pathogenic E. coli strains, were selected to test the effects of two stabilizers (sucrose and trehalose at both 0.1M and 0.5M concentrations) during the freeze-drying process and -80'C storage for 6 months. The results showed that regardless of the type and concentration of the stabilizers, two freeze-dried phages, S1 O26 and Pr121lvw, remained similar titer levels after 6 months of storage. Two other phages, Ro103C3lw and Ro145clw, were able to maintain similar phage levels using 0.1M sucrose. Most importantly, no significant changes were observed on the lytic effect and structural integrity of the freeze-dried phages during storage. These findings provide valuable insight into the use of the freeze-drying method to preserve STEC-specific phages.

Technical Abstract: Lyophilization effectively preserves the physiological and genetic viability of bacteriophages (or phages). However, information is scarce regarding lyophilized phages specific to Shiga toxin-producing Escherichia coli (STEC) strains. The objective of this study was to determine the effects of lyophilization with different cryoprotectants (sucrose and trehalose) and concentrations (0.1 M and 0.5 M) on the stability of seven lytic phages specific to STEC O157 and top 6 non-O157 strains during 6-month storage at -80'C. The lyophilized STEC O26-infecting podophage (S1 O26) and STEC O121-infecting myophage (Pr121lvw) remained similar titers after 6-month storage regardless of cryoprotectants (P>0.05). However, two myophages—STEC O45-infecting phage (Sa45lw) and STEC O157-infecting phage (A4 O157)—were susceptible to the stress during post-lyophilization storage, resulting in approximately 2 log reduction with 0.5M of both sucrose and trehalose. Additionally, all lyophilized phages remained similar antimicrobial activities infecting their bacterial host, and no detectable damage of the phage structure were observed under transmission electron microscope after 6-month post-lyophilization storage at -80'C. The findings of this study show that, though subtle variations, both sucrose and trehalose are effective in preserving the structural integrity and antimicrobial activities of the lyophilized phages infecting STEC O157 and top 6 non-O157 strains.