| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 1.95 MB | Adobe PDF |
Advisor(s)
Abstract(s)
Wastewater treatment plants (WWTPs) are relevant sources of antibiotic resistance into aquatic environments. Disinfection of WWTPs’ effluents (e.g. by UV-C irradiation) may attenuate this problem,
though some clinically relevant bacteria have been shown to survive disinfection. In this study we
characterized 25 CTX-M-producing Escherichia coli strains isolated from a WWTP’s UV-C-irradiated
effluent, aiming to identify putative human health hazards associated with such effluents. Molecular
typing indicated that the strains belong to the phylogroups A, B2 and C and clustered into 9 multilocus
sequence types (STs), namely B2:ST131 (n ¼ 7), A:ST58 (n ¼ 1), A:ST155 (n ¼ 4), C:ST410 (n ¼ 2), A:ST453 (n ¼ 2), A:ST617 (n ¼ 2), A:ST744 (n ¼ 1), A:ST1284 (n ¼ 3) and a putative novel ST (n ¼ 3). PCR-screening identified 9 of the 20 antibiotic resistance genes investigated [i.e. sul1, sul2, sul3, tet(A), tet(B), blaOXA-1-like, aacA4, aacA4-cr and qnrS1]. The more prevalent were sul1, sul2 (n ¼ 15 isolates) and tet(A) (n ¼ 14 isolates). Plasmid restriction analysis indicated diverse plasmid content among strains (14 distinct profiles) and mating assays yielded cefotaxime-resistant transconjugants for 8 strains. Two of the transconjugants displayed a multi-drug resistance (MDR) phenotype. All strains were classified as cytotoxic to
Vero cells (9 significantly more cytotoxic than the positive control) and 10 of 21 strains were invasive
towards this cell line (including all B2:ST131 strains). The 10 strains tested against G. mellonella larvae
exhibited a virulent behaviour. Twenty-four and 7 of the 25 strains produced siderophores and haemolysins,
respectively. Approximately 66% of the strains formed biofilms. Genome analysis of 6 selected strains identified several virulence genes encoding toxins, siderophores, and colonizing, adhesion and
invasion factors. Freshwater microcosms assays showed that after 28 days of incubation 3 out of 6 strains
were still detected by cultivation and 4 strains by qPCR. Resistance phenotypes of these strains remained
unaltered. Overall, we confirmed WWTP’s UV-C-treated outflow as a source of MDR and/or virulent
E. coli strains, some probably capable of persisting in freshwater, and that carry conjugative antibiotic
resistance plasmids. Hence, disinfected wastewater may still represent a risk for human health. More
detailed evaluation of strains isolated from wastewater effluents is urgent, to design treatments that can
mitigate the release of such bacteria.
Description
Keywords
WWTP Antibiotic resistance Virulence Environmental persistence Risk
Citation
Tavares, R. D., Tacão, M., Figueiredo, A. S., Duarte, A. S., Esposito, F., Lincopan, N., ... Henriques, I. (2020). Genotypic and phenotypic traits of blaCTX-M-carrying Escherichia coli strains from an UV-C-treated wastewater effluent. Water Research, 184, art. n.º 116079
Publisher
Elsevier