The rapid identification of antibiotic resistant bacteria is important for public health. In the environment, bacteria are exposed to sub‐inhibitory antibiotic concentrations which has implications in the generation of multi‐drug resistant strains. To better understand these issues, Raman spectroscopy was employed coupled with partial least squares‐discriminant analysis to profile Escherichia coli strains treated with sub‐inhibitory concentrations of antibiotics. Clear differences were observed between cells treated with bacteriostatic (tetracycline and rifampicin) and bactericidal (ampicillin, ciprofloxacin, and ceftriaxone) antibiotics for 6 hr: First, atomic force microscopy revealed that bactericidal antibiotics cause extensive cell elongation whereas short filaments are observed with bacteriostatic antibiotics. Second, Raman spectral analysis revealed that bactericidal antibiotics lower nucleic acid to protein (I₈₁₂/I₈₃₀) and nucleic acid to lipid ratios (I₁₄₈₃/I₁₄₅₂) whereas the opposite is seen with bacteriostatic antibiotics. Third, the protein to lipid ratio (I₂₉₃₆/I₂₈₈₅ and I₂₉₃₆/I₂₈₅₀) is a Raman stress signature common to both the classes. These signatures were validated using two mutants, Δlon and ΔacrB, that exhibit relatively high and low resistance towards antibiotics, respectively. In addition, these spectral markers correlated with the emergence of phenotypic antibiotic resistance. Overall, this study demonstrates the efficacy of Raman spectroscopy to identify resistance in bacteria to sub‐lethal concentrations of antibiotics.

中文翻译：

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使用拉曼光谱对表现出不同药敏性的大肠杆菌菌株进行耐药性分析

快速鉴定抗生素抗性细菌对公共卫生非常重要。在环境中，细菌暴露于亚抑制性抗生素浓度下，这对产生多重耐药菌株产生了影响。为了更好地理解这些问题，拉曼光谱法与偏最小二乘判别分析相结合，对大肠杆菌进行了分析。用亚抑制浓度的抗生素治疗的菌株。在用抑菌（四环素和利福平）和杀菌（氨苄青霉素，环丙沙星和头孢曲松）抗生素处理6小时的细胞之间观察到明显的区别：首先，原子力显微镜检查显示杀菌抗生素引起广泛的细胞伸长，而杀菌细菌则观察到细丝。其次，拉曼光谱分析表明，杀菌抗生素可降低核酸与蛋白质的比例（I ₈₁₂ / I ₈₃₀）和核酸与脂质的比例（I ₁₄₈₃ / I ₁₄₅₂），而抑菌抗生素则相反。第三，蛋白质与脂质的比率（I ₂₉₃₆ / I ₂₈₈₅和I ₂₉₃₆ / I ₂₈₅₀）是这两个类共有的拉曼应力特征。使用两个突变体Δlon和ΔacrB分别验证了这些特征，分别对抗生素表现出较高的抗性和较低的抗性。另外，这些光谱标记物与表型抗生素抗性的出现相关。总体而言，这项研究证明了拉曼光谱法可鉴定细菌对亚致死浓度的抗生素的抵抗力。