Colistin and carbapenems are two categories of antibiotics utilized as a last-resort treatment for infections caused by multi-drug resistant (MDR) and extensively drug resistant (XDR) bacteria. Resistance to these last lines of defence can eventuate total antibiotic resistance. At present, there is scarcity of research present to estimate the current load and impact of the residual concentrations of colistin and carbapenems on environmental microbiome. However, there have been several reports demonstrating resistance development to colistin and carbapenems in a range of environmental compartments in the past few years. Most of their dosage is discharged as waste in its original form, thereby making its way into the urban wastewater. Expected low environmental concentrations, complex structures, stability, and interfering substances make quantification of colistin and carbapenems from environmental samples extremely challenging. There are a few major knowledge gaps addressed in this PhD
Carbapenems are last-resort antibiotics used to treat bacterial infections unsuccessfully treated by most common categories of antibiotics in humans. Most of their dosage is secreted unchanged as waste, thereby making its way into the urban water system. There are two major knowledge gaps addressed in this study to gain a better understanding of the effects of their residual concentrations on the environment and environmental microbiome: development of a UHPLC-MS/MS method of detection and quantification from raw domestic wastewater via direct injection and study of their stability in sewer environment during the transportation from domestic sewers to wastewater treatment plants. The UHPLC-MS/MS method was developed for four carbapenems: meropenem, doripenem, biapenem and ertapenem, and validation was performed in the range of 0.5–10 μg/L for all analytes, with limit of detection (LOD) and limit of quantification (LOQ) values ranging from 0.2–0.5 μg/L and 0.8–1.6 μg/L respecti