Poster Presentation Australian Microbial Ecology 2017

Silver, copper, and zinc induced cross-resistance to antibiotics in a wastewater bacterial community (#115)

Xiayuan Wu 1 , Sotirios Vasileiadis 1 , Gianluca Brunetti 1 , Barbara Drigo 1 , Enzo Lombi 1 , Christopher Saint 1 , Erica Donner 1
  1. University of South Australia, Adelaide/Mawson Lakes, SOUTH AUSTRALIA, Australia


To understand the microbial/environmental interactions associated with metal induced cross-resistance to antibiotics in urban wastewaters.


Methods and results

Influent collected from an Australian wastewater treatment plant was used to create microcosms that were spiked with silver, copper, or zinc at concentrations ranging from 1-10000 µM. All treatments (including unamended controls) were sampled for analysis after one and seven days incubation. Next-generation-sequencing and real-time/digital-droplet PCR were used to assess the bacterial diversity and abundance of horizontal-gene-transfer/antibiotic-resistance marker genes respectively. Detailed chemical analyses were also conducted.


Exposure time and metal concentration gradient were the main factors correlating with the resulting community structures. Silver induced a greater reduction in α-diversity than copper and zinc. High metal concentrations strongly and consistently selected for operational taxonomic units (OTUs) within the Acinetobacter and Arcobacter. Maximum likelihood phylogenies of the selected OTUs indicated the selection of potential human pathogens commonly linked to stress survival through association with protists. Preliminary real-time PCR data showed an increase in the intI-1 and korB genes relative to the control at low to intermediate range concentrations over 7 days and increasing tetW at high metal concentrations. An inverse gene-copy/metal-dose relationship was observed for the qacE gene over 7 days. Correlations for these genes and key OTUs were subsequently explored.



Plasmid dispersal mechanisms can be very active in wastewater and metal stress may select for some pathogens. Cross-resistance was indicated for tetW and the ongoing quantification of a broader range of ARGs may help elucidate the underlying mechanisms.   


Significance of study

Horizontal transfer mediated microbial cross-resistance to metals and antibiotics is a naturally occurring phenomenon that may potentially be enhanced in evolutionary hotspots such as industrial and municipal wastewaters. We are working towards understanding the relevant underlying ecological mechanisms in order to help prevent the evolution of “superbugs” in wastewater.