Enhanced degradation of ciprofloxacin by Sri Lankan red earth

Abstract

Ciprofloxacin is the most widely prescribed fluoroquinolone-class antibiotic in the world. Excess application and improper utilization cause ciprofloxacin accumulation in natural environments. It’s long half-life in soil can lead to the development of antibiotic resistance among microorganisms, which is a global health issue. Therefore, identifying mechanisms to enhance antibiotic degradation to reduce their half-life is highly important. This study investigated the efficiency of ciprofloxacin degradation via photocatalytic oxidation and Fenton process by a natural Fe and Ti oxides rich red soil (RE). The degradation experiments were carried out by mixing 500 mg of ciprofloxacin in 100 g of RE. Ciprofloxacin containing crude was extracted at different time intervals (1 day, 1, 3, 5, 7, 9 and 16 weeks) using methanol. The extracted crude was analyzed by the Fourier Transform Infrared Spectroscopy (FTIR) to identify the structural changes in ciprofloxacin. Antibacterial activity of the crude against Staphylococcus aureus ATCC 25923 was tested using the agar diffusion method and determining the minimum inhibitory concentration (MIC) by broth dilution method to semi-quantitatively assess the degree of degradation of ciprofloxacin by RE. Appearance of FTIR peak at 1741 cm-1 position afterfive weeks exposure time confirmed the formation of by-products by ciprofloxacin degradation. A decreased inhibition zone was observed at day 25 and no inhibition zone was observed after 64 days indicating complete degradation of ciprofloxacin. The MIC increased from 39 mg/kg to 1250 mg/kg at day 1 and week 16, respectively, suggesting a 32-fold reduction in biologically-active ciprofloxacin concentration. Results of the present study indicate that RE has the potential to degrade and reduce the half-life of ciprofloxacin.