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.
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。