Evaluation of Chemical Changes in Laboratory-Induced Colistin-Resistant .

This study evaluates the electrical potential and chemical alterations in laboratory-induced colistin-resistant , as compared to the susceptible strain using spectroscopic analyses. The minimal inhibitory concentration (MIC) of colistin, ζ-potential and chemical composition analysis of strains are determined. The results obtained for the with induced high-level colistin resistance (MIC = 16.0 ± 0.0 mg/L) are compared with the strain susceptible to colistin (MIC = 0.25 ± 0.0 mg/L). Fourier transform infrared (FTIR) and Raman spectroscopic studies revealed differences in bacterial cell wall structures and lipopolysaccharide (LPS) of and strains. In the beginning, we assumed that the obtained results could relate to a negative charge of the bacterial surface and different electrostatic interactions with cationic antibiotic molecules, reducing the affinity of colistin and leading to its lower penetration into cell. However, no significant differences in the ζ-potential between the and strains are noticed. In conclusion, this mechanism is most probably associated with recognisable changes in the chemical composition of the cell wall (especially in LPS) when compared to the susceptible strain.