School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China.
J Appl Microbiol. 2023 Aug 1;134(8). doi: 10.1093/jambio/lxad177.
Disinfectants such as benzalkonium chloride (BC), extensively used in animal farms and food-processing industries, contribute to the development of adaptive and cross-resistance in foodborne pathogens, posing a serious threat to food safety and human health. The purpose of this study is to explore whether continuous exposure of Salmonella enterica serovar 1,4,[5],12:i:- (S. 1,4,[5],12:i:-) to sublethal concentrations of BC could result in acquired resistance to this agent and other environmental stresses (e.g. antibiotics, heat, and acid).
BC tolerance increased in all tested strains after exposure to gradually increasing concentrations of BC, with increases in minimum inhibitory concentrations between two and sixfold. The survival rate of BC-adapted strains was significantly (P < 0.05) higher than that of their wild-type (non-adapted) counterparts in lethal concentrations of BC. In addition, significant reductions (P < 0.05) in zeta potential were observed in BC-adapted strains compared to wild-type ones, indicating that a reduction in cell surface charge was a cause of adaptative resistance. More importantly, two BC-adapted strains exhibited increased antibiotic resistance to levofloxacin, ceftazidime, and tigecycline, while gene mutations (gyrA, parC) and antibiotic efflux-related genes (acrB, mdsA, mdsB) were detected by genomic sequencing analysis. Moreover, the tolerance of BC-adapted strains to heat (50, 55, and 60°C) and acid (pH 2.0, 2.5) was strain-dependent and condition-dependent.
Repeated exposure to sublethal concentrations of BC could result in the emergence of BC- and antibiotic-resistant S. 1,4,[5],12:i:- strains.
苯扎氯铵（BC）等消毒剂广泛应用于动物养殖场和食品加工业，导致食源性病原体产生适应性和交叉耐药性，对食品安全和人类健康构成严重威胁。本研究旨在探讨沙门氏菌 1,4,[5],12:i:-（S. 1,4,[5],12:i:-）连续暴露于亚致死浓度的 BC 是否会导致对该剂和其他环境应激（如抗生素、热和酸）的获得性耐药。
所有测试菌株在暴露于逐渐增加的 BC 浓度后，BC 耐受性均增加，最低抑菌浓度增加了 2 至 6 倍。BC 适应株在致死浓度的 BC 中的存活率明显（P < 0.05）高于其野生型（未适应）对照株。此外，与野生型相比，BC 适应株的 ζ 电位明显降低（P < 0.05），表明细胞表面电荷减少是适应性耐药的原因。更重要的是，两个 BC 适应株对左氧氟沙星、头孢他啶和替加环素的抗生素耐药性增加，而通过基因组测序分析检测到基因突变（gyrA、parC）和抗生素外排相关基因（acrB、mdsA、mdsB）。此外，BC 适应株对热（50、55 和 60°C）和酸（pH 2.0、2.5）的耐受性取决于菌株和条件。
重复暴露于亚致死浓度的 BC 可导致出现 BC 和抗生素耐药的 S. 1,4,[5],12:i:-菌株。
