Effect of benzalkonium chloride adaptation on the tolerance of Cronobacter sakazakii exposed to subsequent lethal stresses

Benzalkonium Chloride (BC) is applied in food processing, clinical settings, and households to control the spread of pathogens. However, BC adaptation may promote bacterial resistance against biocides and physical stresses. In the study, the sensitivity of non-adapted and BC-adapted C. sakazakii to subsequent lethal stresses was assessed. Results indicated that BC adaptation provided C. sakazakii direct protection against high BC concentrations, but no cross-protection against heat, acid, osmotic, desiccative, and ethanol-related stress. BC adaptation reduced the proportion of saturated fatty acids (SFA) and the ratio of SFA to unsaturated fatty acids (SFA/USFA), whereas increasing the proportion of unsaturated fatty acids (USFA) in C. sakazakii. Six genes related to motility, metabolism, transport, and efflux were upregulated under BC adaptation. Some Surface-enhanced Raman spectroscopy (SERS) signal characteristics of the BC-adapted cell were significantly different from that of the non-adapted cell, which reflected the changes of intracellular proteins, nucleic acids, carbohydrates, and other cellular components. Consequently, the ability of BC-adapted C. sakazakii to withstand subsequent stresses should be taken into account when developing microbial control measures. A greater understanding of BC adaptation mechanisms in C. sakazakii will provide important insights for disease prevention.