Issue 9, 2022

Inactivation mechanisms of Escherichia coli O157:H7 and Salmonella enterica by free residual chlorine

Abstract

The sub-cellular mechanisms by which residual free chlorine (FC) inactivates E. coli O157:H7 and S. enterica in the absence of organic matter was investigated. The average removal rates for E. coli were 38–99% after a 1 min exposure to 0.12–0.5 mg L−1 FC, while that of S. enterica were 10–50% after exposure to 0.5–2.0 mg L−1 FC. Chlorination caused significant membrane structural damage and reduced membrane potential. Low FC levels or short exposure times had a modest impact on S. enterica. Cell metabolic activity decreased over time for all initial FC levels, and with increasing FC levels at each time point. Total ATP levels increased in the first minute post-chlorination, while the intracellular ATP levels decreased with increasing FC levels and exposure time, likely due to ATP leakage. The depolarized E. coli density reached a plateau after the first 2 min at FC ≥ 0.5 mg L−1 while that of S. enterica took 5 min to reach a plateau even at FC ≥ 1 mg L−1, indicating their ability to withstand chlorination. Residual FC levels are sufficient to induce damage to cellular organelles and compromise their survival, and the mechanism of injury depends on FC levels and exposure time.

Graphical abstract: Inactivation mechanisms of Escherichia coli O157:H7 and Salmonella enterica by free residual chlorine

Supplementary files

Article information

Article type
Paper
Submitted
24 Maijs 2022
Accepted
04 Aug. 2022
First published
05 Aug. 2022

Environ. Sci.: Water Res. Technol., 2022,8, 2006-2018

Author version available

Inactivation mechanisms of Escherichia coli O157:H7 and Salmonella enterica by free residual chlorine

M. D. Abnavi, T. Larimian, P. Srinivasan, D. Munther and C. R. Kothapalli, Environ. Sci.: Water Res. Technol., 2022, 8, 2006 DOI: 10.1039/D2EW00382A

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