Transfer of antibiotic resistance genes between Enterococcus faecalis strains in filter feeding zooplankton Daphnia magna and Daphnia pulex

Temilola Olukayode Olanrewaju, Mary McCarron, J Dooley, Joerg Arnscheidt

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)
196 Downloads (Pure)


Antibiotic resistant bacteria from faecal pollution sources are pervasive in aquatic environments. A facilitating role for the emergence of waterborne, multi-drug resistant bacterial pathogens has been attributed to biofiltration but had not yet been substantiated. This study investigated the effect of filtration and gut passage in Daphnia spp. on conjugal transfer of resistance genes in Enterococcus faecalis. In vivo conjugation experiments involved a vancomycin-resistant donor strain bearing a plasmid-borne vanA resistance gene, and two vancomycin-susceptible and rifampicin-resistant recipient strains in the presence of Daphnia magna or Daphnia pulex. Results showed successful transfer of the vanA resistance gene from donor to recipient; gene identity was confirmed by PCR and DNA sequencing. There was no significant difference in the number of transconjugants recovered from D. magna and D. pulex. However, transconjugant numbers differed by one order of magnitude between recipient strains. Transconjugant numbers from D. magna were also significantly different between treatments with ingestion of individual phytoplankton species before filtration of bacteria. The highest transfer efficiency calculated from excreted transconjugants was 2.5 × 10-6. This proof of concept for facilitation of horizontal gene transfer by a filter feeding organism provides evidence that Daphnia can disseminate antibiotic resistant transconjugants in the environment.
Original languageEnglish
Pages (from-to)1168-1175
Number of pages8
JournalScience of the Total Environment
Early online date22 Dec 2018
Publication statusPublished (in print/issue) - 1 Apr 2019


  • Daphnia, antimicrobial resistance, vanA gene, conjugation, bacteria, Enterococcus faecalis, enterococci, Enterococcus, filter feeder, zooplankton, antibiotic resistance, horizontal transfer, multi-drug resistance, super bug, host microbe interaction, microbe, cladocera, palmellopsis, desmodesmus, chlorophyta
  • Enterococcus faecalis
  • Daphnia
  • Bacteria
  • Antimicrobial resistance
  • Conjugation
  • vanA gene


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