The effects of emerging contaminants on the behaviour of Acinetobacter calcoaceticus derived from biofilms

Abstract

Knowledge regarding the ecotoxicological effects of emerging contaminants (EC) in drinking water distribution system (DWDS) microbiota is limited. Given the issues associated with biofilm formation in DWDS, this work studied the effects of the exposure of Acinetobacter calcoaceticus biofilms to four pharmaceutical compounds already encountered in drinking water (DW) at residual concentrations (ng L⁻¹): caffeine – CAF, carbamazepine – CBZ, ciprofloxacin – CIP and ibuprofen – IBP. The exposure assays were performed with the compounds alone and in combination (MIX). The results obtained aim to contribute for the understanding of the role of ECs exposure for 7 days in bacterial behaviour, particularly the ability to form biofilms, susceptibility to antibiotics (CIP, levofloxacin – LEV, tetracycline – TET and trimethoprim–sulfamethoxazole – TMP-SMX), tolerance to NaOCl, motility and growth rate. It was found that IBP exposure decreased biofilm formation ability by 11%, while MIX exposure increased it by 16%. Regarding antibiotics susceptibility, CAF exposure decreased susceptibility to TPM-SMX, while CBZ and CIP exposures seem to cause an increase in the susceptibility to TMP-SMX. Furthermore, exposure to residual levels of CIP decreased the susceptibility to CIP and LEV, and IBP exposure seems to slightly decrease the susceptibility to LEV and TET. The ranges of minimum bactericidal concentration (MBC) of NaOCl have also slightly increased (for CIP and IBP exposure) or decreased (for the exposure to CBZ). Higher A. calcoaceticus growth rates were obtained after CIP exposure. These results demonstrate that the selected ECs affect the behaviour and growth dynamics of bacteria under conditions typically found in DWDS. Among the selected ECs, CIP and IBP were those causing the most significant effects. Furthermore, this study lays the groundwork for knowledge enrichment regarding bacterial behaviour in biofilms and their impact on DWDS.