Efficacy of Quaternary Ammonium Compounds for Control of Individual and Mixed Cultures of Escherichia coli with High- and Low-Quaternary Ammonium Compounds Resistance
Citation
Castro, V.S., Conte, C.A., De Souza Figueiredo, E.E., Yang, X., Stanford, K. (2023). Efficacy of Quaternary Ammonium Compounds for Control of Individual and Mixed Cultures of Escherichia coli with High- and Low-Quaternary Ammonium Compounds Resistance. Foodborne Pathogens and Disease, [online] 20(7), 261-269. http://dx.doi.org/10.1089/fpd.2023.0005
Plain language summary
Quaternary ammonium compounds (QACs) are the most commonly used sanitizer in food processing settings. There have some concerns about potential bacterial resistance to this group of compounds. We compared different combinations of resistance levels of E. coli, a commonly used indicator organism for food processing hygiene in their response to QACs. One of the low resistance pair (T18 consisting strains C20 and C23) showed greater resistance than individual strains, likely resulting from the yehW gene harbored by C23. Regardless, the minimum inhibition concentrations (MIC) of all the strains tested were ≤ 12.5 ppm, well below the in-use concentration of QACs, 200 ppm. The findings of this work show that it would be unlikely that the application of QACs as a sanitizer in food setting leads to resistance in E. coli.
Abstract
Escherichia coli is a well-characterized micro-organism in scientific literature. Similarly, quaternary ammonium compounds (QACs) are historical sanitizers in food processing. However, the use of QACs has been questioned due to bacterial resistance in some studies. Therefore, this study aimed to compare effects of single and mixed cultures of E. coli strains of different serogroups with either high (six strains) or low (five strains) resistance to QACs. Twenty-five combinations of strains with either high (H)- or low (L)-QAC resistance were analyzed (H + H vs. L + L). After exposure to QAC, combinations with statistical differences (p < 0.05) compared with individuals were selected and an inactivation model determined using GInaFit®. Only one combination of two strains (C23 and C20) with low-QAC resistance (mixture T18) had greater resistance (p < 0.05) than the individual isolates. The combination T18 and individual strain C23 presented a Weibull model, whereas the other isolated strain (C20) presented a biphasic inactivation model with a shoulder. Whole genome sequencing determined that unlike C20, C23 carried yehW, which may have led to Weibull inactivation. Possibly, very rapid interaction of C20 with the QAC favored increased survival of C23 and overall persistence of the T18 mixture. Consequently, our results indicate that individual E. coli with low-QAC resistance can synergistically interfere with QAC inactivation.