Abstract：
OBJECTIVE: 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).
RESULTS: 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.
CONCLUSIONS: Repeated exposure to sublethal concentrations of BC could result in the emergence of BC- and antibiotic-resistant S. 1,4,[5],12:i:- strains.
RESULTS: 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.
CONCLUSIONS: Repeated exposure to sublethal concentrations of BC could result in the emergence of BC- and antibiotic-resistant S. 1,4,[5],12:i:- strains.
摘要：
目的：消毒剂如苯扎氯铵（BC）广泛用于动物养殖场和食品加工行业，有助于发展食源性病原体的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。本研究的目的是探讨是否连续接触肠道沙门菌1,4,[5],12:i:-(S.1,4,[5],12：i：-）对亚致死浓度的BC可能导致对这种药物和其他环境压力的获得性抗性（例如抗生素，热,和酸）。
结果：暴露于逐渐增加浓度的BC后，所有测试菌株的BC耐受性均增加，最低抑制浓度增加2到6倍。在BC的致死浓度下，适应BC的菌株的存活率显着（P<0.05）高于其野生型（非适应）对应物。此外,与野生型相比，在适应BC的菌株中观察到zeta电位显着降低（P<0.05），表明细胞表面电荷的减少是适应性电阻的原因。更重要的是,两种适应BC的菌株对左氧氟沙星的抗生素耐药性增加，头孢他啶,还有替加环素,而基因突变(gyrA，parC)和抗生素外排相关基因(acrB，mdsA,mdsB）通过基因组测序分析检测。此外，适应BC的菌株对热（50、55和60°C）和酸（pH2.0、2.5）的耐受性取决于菌株和条件。
结论：反复暴露于亚致死浓度的BC可能导致出现对BC和抗生素耐药的S.1,4,[5]，12:i:-菌株。
结果：暴露于逐渐增加浓度的BC后，所有测试菌株的BC耐受性均增加，最低抑制浓度增加2到6倍。在BC的致死浓度下，适应BC的菌株的存活率显着（P<0.05）高于其野生型（非适应）对应物。此外,与野生型相比，在适应BC的菌株中观察到zeta电位显着降低（P<0.05），表明细胞表面电荷的减少是适应性电阻的原因。更重要的是,两种适应BC的菌株对左氧氟沙星的抗生素耐药性增加，头孢他啶,还有替加环素,而基因突变(gyrA，parC)和抗生素外排相关基因(acrB，mdsA,mdsB）通过基因组测序分析检测。此外，适应BC的菌株对热（50、55和60°C）和酸（pH2.0、2.5）的耐受性取决于菌株和条件。
结论：反复暴露于亚致死浓度的BC可能导致出现对BC和抗生素耐药的S.1,4,[5]，12:i:-菌株。
