Antibiotics in shallow groundwater underlying urban informal settlements in developing countries: influence of on-site sanitation practices and risk assessment

Abstract

This study investigated the influence of on-site sanitation practices (OSS) on antibiotics in shallow groundwater underlying an informal settlement in Kampala City (Uganda) and the resulting antibiotic resistance risks. Ten antibiotics (including sulfonamides, fluoroquinolones, quinolones, penicillins and tetracyclines) were investigated in 17 groundwater sources in relation to physico-chemical and bacteriological water quality parameters. Seven antibiotics were detected, at a maximum total concentration of 1,400 ng/L during the dry season and 730 ng/L during the wet season. A significant positive correlation was observed between sulfathiazole and Escherichia coli (p < 0.001), supported by principal component analysis. Hierarchical cluster analysis showed grouping of antibiotics with parameters usually associated with OSS (E. coli, chlorides, nitrates, sodium and sulphates). Over 65% of the locations presented a high risk for antibiotic resistance during the dry season. This study showed that the population in informal settlements is exposed to a high risk of antibiotic resistance, influenced by OSS.