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Gill A, McMahon T, Dussault F, et al. Delayed lactose utilization among Shiga toxin-producing Escherichia coli of serogroup O121. Food Microbiol. 2021;102:103903doi: 10.1016/j.fm.2021.103903.
Gill, A., McMahon, T., Dussault, F., Jinneman, K., Lindsey, R., Martin, H., Stoneburg, D., Strockbine, N., Wetherington, J., & Feng, P. (2022). Delayed lactose utilization among Shiga toxin-producing Escherichia coli of serogroup O121. Food microbiology, 102103903. https://doi.org/10.1016/j.fm.2021.103903
Gill, Alexander, et al. "Delayed lactose utilization among Shiga toxin-producing Escherichia coli of serogroup O121." Food microbiology vol. 102 (2022): 103903. doi: https://doi.org/10.1016/j.fm.2021.103903
Gill A, McMahon T, Dussault F, Jinneman K, Lindsey R, Martin H, Stoneburg D, Strockbine N, Wetherington J, Feng P. Delayed lactose utilization among Shiga toxin-producing Escherichia coli of serogroup O121. Food Microbiol. 2022 Apr;102:103903. doi: 10.1016/j.fm.2021.103903. Epub 2021 Sep 15. PMID: 34809935.
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Food Microbiol. 2022 Apr;102:103903. doi: 10.1016/j.fm.2021.103903. Epub 2021 Sep 15.

Delayed lactose utilization among Shiga toxin-producing Escherichia coli of serogroup O121.

Food microbiology

Alexander Gill, Tanis McMahon, Forest Dussault, Karen Jinneman, Rebecca Lindsey, Haley Martin, Devon Stoneburg, Nancy Strockbine, June Wetherington, Peter Feng

Affiliations

  1. Health Canada, Bureau of Microbial Hazards, 251 Sir Frederick Banting Driveway, Ottawa, Ontario, K1A 0K9, Canada. Electronic address: [email protected].
  2. Health Canada, Bureau of Microbial Hazards, 251 Sir Frederick Banting Driveway, Ottawa, Ontario, K1A 0K9, Canada.
  3. Health Canada, Bureau of Food Surveillance and Science Integration, 251 Sir Frederick Banting Driveway, Ottawa, Ontario, K1A 0K9, Canada.
  4. U.S. Food and Drug Administration, Office of Regulatory Affairs, Office of Regulatory Science, Pacific Northwest Laboratory, 22201 23rd Dr SE, Bothell, WA, 98021, USA.
  5. Enteric Diseases Laboratory Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.
  6. U.S. FDA, Division of Microbiology, College Park, MD, 20740, USA.

PMID: 34809935 DOI: 10.1016/j.fm.2021.103903

Abstract

Two outbreaks of Shiga toxin-producing Escherichia coli O121:H19 associated with wheat flour, in the United States of America and Canada, involved strains with an unusual phenotype, delayed lactose utilization (DLU). These strains do not ferment lactose when initially cultured on MacConkey agar (MAC), but lactose fermentation occurs following subculture to a second plate of MAC. The prevalence of DLU was determined by examining the β-galactosidase activity of 49 strains of E. coli O121, and of 37 other strains of E. coli. Twenty four of forty three O121:H19 and one O121:NM displayed DLU. Two strains (O121:NM and O145:H34) did not have detectable β-galactosidase activity. β-glucuronidase activity of O121 strains was also determined. All but six DLU strains had normal β-glucuronidase activity. β-glucuronidase activity was suppressed on MAC for 17 of 23 O121 non-DLU strains. Genomic analysis found that DLU strains possessed an insertion sequence, IS600 (1267 bp), between lacZ (β-galactosidase) and lacY (β-galactoside permease), that was not present in strains exhibiting normal lactose utilization. The insert might reduce the expression of β-galactoside permease, delaying import of lactose, resulting in the DLU phenotype. The high probability of DLU should be considered when using lactose-containing media for the isolation of STEC O121.

Crown Copyright © 2021. Published by Elsevier Ltd. All rights reserved.

Keywords: Delayed lactose utilization; Lac operon; O121:H19; Shiga toxin-producing E. coli

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