Flow Injection-High Resolution-Electrospray Ionization-Mass Spectrometry (FI-HR-ESI-MS) Method for the Screening of Antimicrobial Pharmaceutical Drugs and Compounds against Klebsiella pneumoniae.

The development of drug resistant microorganism is a global threat. Therefore, screening of more compounds for antimicrobial potentials is needed. Hence, a rapid method was developed for the screening of antimicrobial drugs and compounds against Klebsiella pneumoniae using Flow Injection Analysis-High Resolution-Mass Spectrometry. The method was optimized for bacterial culture time and concentration of drugs. IC50 values for the drugs were calculated from the percent intensity of 704.5207 m/z of K. pneumoniae at 5 hrs incubation. This mass was proposed as diacylglycerophosphoethanolamine and observed as a potential biomarker of K. pneumoniae for the evaluation of inhibition potential of antimicrobial drugs and compounds. The calculated values for half maximal inhibitory concentration of cefixime, gentamicin and enrofloxacin were 0.052, 0.028 and 0.042 µg/mL, respectively. Ten compounds were also screened against the developed method, among them one compound (RSE-6) was found to be active with IC50 value of 45.08 µg/mL. The obtained results were further compared with MIC values, obtained from micro dilution and Alamar blue assay after 24 hrs incubation. In comparison to these methods, developed method is sensitive, reproducible, rapid and robust for the determination of IC50 value or inhibition potential of the drugs and compounds even at early incubation period of 5 hours.