title: The effect of conventional wastewater treatment on the levels of antimicrobial-resistant bacteria in effluent: a meta-analysis of current studies.
abstract: Antimicrobial agents in the environment are a cause for concern. Antimicrobial drug residues and their metabolites reach the aquatic and terrestrial environment primarily through wastewater treatment plants (WWTP). In addition to the potential direct negative health and environmental effects, there is potential for the development of antimicrobial-resistant bacteria. Residue levels below the minimum inhibitory concentration for a bacterial species can be important in selection of resistance. There is uncertainty associated with resistance formation during WWTP processing. A meta-analysis study was carried out to analyse the effect of WWTP processing on the levels of antimicrobial-resistant bacteria within bacterial populations. An analysis of publications relating to multiple antimicrobial-resistant (MAR) bacteria (n = 61), single antimicrobial-resistant (SAR) E. coli (n = 81) and quinolone/fluoroquinolone-resistant (FR) bacteria (n = 19) was carried out. The odds-ratio (OR) of MAR (OR = 1.60, p < 0.01), SAR (OR = 1.33, p < 0.01) and FR (OR = 1.19, p < 0.01) bacteria was determined. The results infer that WWTP processing results in an increase in the proportion of resistant bacteria in effluent, even though the overall bacterial population may have reduced (i.e. a reduction in total bacterial numbers but an increase in the percentage of resistant bacteria). The results support the need for further research into the development of antimicrobial-resistant strains and possible selective pressures operating in WWTPs.
authors.affiliation: Biosystems Engineering, UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Suvi
authors.initials: S
authors.lastname: Harris
authors.forename: Martin
authors.initials: M
authors.lastname: Cormican
authors.forename: Enda
authors.initials: E
authors.lastname: Cummins
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D024881:Drug Resistance, Bacterial; D004784:Environmental Monitoring; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000382:microbiology*; D018508:Water Purification
chemical_list: D000900:Anti-Bacterial Agents; D062065:Wastewater