Occurrence and resistance risk assessment of selected antimicrobials in surface waters of Juja, Kenya

Abstract

This thesis aimed to investigate the occurrence of selected antibiotics and antiretrovirals in the surface water of Juja, Kenya. Juja is a fast-growing town near Nairobi, which can be described by inadequate sanitation and relatively high usage of antibiotics and antiretrovirals for the treatment of HIV/AIDS as well as other infections. When entering the environment, these compounds can have adverse effects and exacerbate the problem of antibiotic resistance. The selected compounds included amoxicillin (AMX), ampicillin (AMP), tetracycline (TET), oxytetracycline (OXT), doxycycline (DOX), sulfamethoxazole (SMX), sulfadiazine (SDZ), sulfamethazine (SMZ), trimethoprim (TMP), carbamazepine (CBZ), lamivudine (3TC), and nevirapine (NVP). The occurrence of these was investigated by collecting water samples from the unlined open drains, a river, and a pond in the study area. Sampling was conducted in two rounds. Samples were extracted using solid-phase extraction and then analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Based on the measured concentrations, the risk for resistance development was evaluated by calculating risk quotient (RQ) values. Most of the studied compounds were detected in the samples, except for OXT and SDZ. Overall, the concentration ranged from 17 ng/l to 4269 ng/l. In both sampling rounds, SMX was detected with the highest concentration of antibiotics, while 3TC was the most abundant antiretroviral. The concentrations during the second sampling were significantly higher compared to the first sampling, with the total sum of concentrations being almost two times higher. The concentration between sampling points varied, with the highest concentration measured from open drains in more densely populated areas and close to the old WWTP. Measured concentrations in a river and a pond were generally lower compared to open drains. Differences in concentrations can be influenced by varying environmental conditions as well as different consumption levels and the physicochemical properties of the compounds. The measured concentrations in this study were lower compared to previous studies conducted in the same region and other sub-Saharan countries. However, the order of the compounds and the most detected compounds were similar. When compared to high-income countries, the concentrations were higher. The RQs ranged between 0.01 and 1.01, which indicates a low to high risk for the development of antibiotic resistance. TMP posed the highest risk for resistance selection. Further research on the subject, particularly regarding the development and occurrence of antibiotic resistance, is needed.