Determination of synergistic effects of antibiotics and Zno NPs against isolated E. Coli and A. Baumannii bacterial strains from clinical samples.

Abstract The mortality rates has been increased globally due to multidrug resistant (MDR) E.coli and A.baumanii bacterial strains and also there is an emerging resistance of the Enterobacteriaceae family of bacteria to Carbapenem antibiotics (CRE) in Saudi Arabia. The main aim of our research study is to isolate E.coli and A. baumannii bacterial species from various collected clinical samples and to evaluate the MIC and FICI of Colistin, Ciprofloxacin, Meropenem and ZnO NPs and in combination of Colistin, Ciprofloxacin, Meropenem with ZnO NPs. The clinical isolated strains of A. baumannii (MRO-17-13) and A. baumannii (MRO-17–25) was found to be sensitive towards colistin with 0.5 μg/mL concentration, whereas, all the isolated A. baumannii strains showed similar MIC value 2 mg/mL when tested with ZnO NPs, the MIC value for the ZnO NPs was found to be similar for all the E.coli strains 0.25 mg/mL. The effects of all Ciprofloxacin concentrations used in the study were bacteriostatic against E. coli (01UR19006568-01) strain but 1 mg/mL concentration of ZnO NPs alone is showed bactericidal activity, ZnO NPs effect was found to be concentration dependent, as highest concentration of ZnO NPs showed strongest antibacterial effect. In conclusion, more investigation is required to evaluate the acceptable concentration of Zno NPs and antibiotics selected to avoid toxicity and must be tested against more clinically isolated gram-negative bacterial strains.