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Profiling antibiotic resistance in Escherichia coli strains displaying differential antibiotic susceptibilities using Raman spectroscopy
Author(s) -
Verma Taru,
Annappa Harshitha,
Singh Saumya,
Umapathy Siva,
Nandi Dipankar
Publication year - 2021
Publication title -
journal of biophotonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 66
eISSN - 1864-0648
pISSN - 1864-063X
DOI - 10.1002/jbio.202000231
Subject(s) - antibiotics , tetracycline , microbiology and biotechnology , antibiotic resistance , ampicillin , bacteria , ciprofloxacin , biology , escherichia coli , nucleic acid , chemistry , biochemistry , genetics , gene
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 (I 812 /I 830 ) and nucleic acid to lipid ratios (I 1483 /I 1452 ) whereas the opposite is seen with bacteriostatic antibiotics. Third, the protein to lipid ratio (I 2936 /I 2885 and I 2936 /I 2850 ) is a Raman stress signature common to both the classes. These signatures were validated using two mutants, Δ lon and Δ acrB , 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.