Waste water effluent contributes to the dissemination of CTX-M-15 in the natural environment
Journal of Antimicrobial Chemotherapy
Oxford University Press (OUP)
© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/ 3.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
OBJECTIVES: Multidrug-resistant Enterobacteriaceae pose a significant threat to public health. We aimed to study the impact of sewage treatment effluent on antibiotic resistance reservoirs in a river. METHODS: River sediment samples were taken from downstream and upstream of a waste water treatment plant (WWTP) in 2009 and 2011. Third-generation cephalosporin (3GC)-resistant Enterobacteriaceae were enumerated. PCR-based techniques were used to elucidate mechanisms of resistance, with a new two-step PCR-based assay developed to investigate bla(CTX-M-15) mobilization. Conjugation experiments and incompatibility replicon typing were used to investigate plasmid ecology. RESULTS: We report the first examples of bla(CTX-M-15) in UK river sediment; the prevalence of bla(CTX-M-15) was dramatically increased downstream of the WWTP. Ten novel genetic contexts for this gene were identified, carried in pathogens such as Escherichia coli ST131 as well as indigenous aquatic bacteria such as Aeromonas media. The bla(CTX-M-15) -gene was readily transferable to other Gram-negative bacteria. We also report the first finding of an imipenem-resistant E. coli in a UK river. CONCLUSIONS: The high diversity and host range of novel genetic contexts proves that evolution of novel combinations of resistance genes is occurring at high frequency and has to date been significantly underestimated. We have identified a worrying reservoir of highly resistant enteric bacteria in the environment that poses a threat to human and animal health.
This work was supported by the Natural Environment Research Council (grant NE/E004482/1). G. C. A. A. was supported by a BBSRC studentship. W. H. G. has been supported by the ERDF and ESF since moving to the University of Exeter
This is the final version of the article. Available from the publisher via the DOI in this record.
Vol. 69, pp. 1785 - 1791
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