Copper amendment of agricultural soil selects for bacterial antibiotic resistance in the field
Version of Record online: 21 DEC 2004
Letters in Applied Microbiology
Volume 40, Issue 2, pages 146–151, February 2005
How to Cite
Berg, J., Tom-Petersen, A. and Nybroe, O. (2005), Copper amendment of agricultural soil selects for bacterial antibiotic resistance in the field. Letters in Applied Microbiology, 40: 146–151. doi: 10.1111/j.1472-765X.2004.01650.x
- Issue online: 21 DEC 2004
- Version of Record online: 21 DEC 2004
- 2004/1009: received 31 August 2004, revised 15 October 2004 and accepted 19 October 2004
- amplified ribosomal DNA restriction analysis;
- community structure;
- copper resistance;
- culturable bacteria
Aims: The objective of this study was to determine whether Cu-amendment of field plots affects the frequency of Cu resistance, and antibiotic resistance patterns in indigenous soil bacteria.
Methods and Results: Soil bacteria were isolated from untreated and Cu-amended field plots. Cu-amendment significantly increased the frequency of Cu-resistant isolates. A panel of isolates were characterized by Gram-reaction, amplified ribosomal DNA restriction analysis and resistance profiling against seven antibiotics. More than 95% of the Cu-resistant isolates were Gram-negative. Cu-resistant Gram-negative isolates had significantly higher incidence of resistance to ampicillin, sulphanilamide and multiple (≥3) antibiotics than Cu-sensitive Gram-negative isolates. Furthermore, Cu-resistant Gram-negative isolates from Cu-contaminated plots had significantly higher incidence of resistance to chloramphenicol and multiple (≥2) antibiotics than corresponding isolates from control plots.
Significance and Impact of the Study: The results of this field experiment show that introduction of Cu to agricultural soil selects for Cu resistance, but also indirectly selects for antibiotic resistance in the Cu-resistant bacteria. Hence, the widespread accumulation of Cu in agricultural soils worldwide could have a significant effect on the environmental selection of antibiotic resistance.