Cu exposure under field conditions coselects for antibiotic resistance as determined by a novel cultivation-independent bacterial community tolerance assay.
Environmental reservoirs of antibiotic resistance are important to human health, and recent evidence indicates that terrestrial resistance reservoirs have expanded during the antibiotic era. Our aim was to study the impact of Cu pollution as a selective driver for the spread of antibiotic resistance in soil. Bacteria were extracted from a well-characterized soil site solely contaminated with CuSO₄ more than 80 years ago and from a corresponding control soil. Pollution-induced bacterial community tolerance (PICT) to Cu and a panel of antibiotics was determined by a novel cultivation-independent approach based on [³H]bromodeoxyuridine (BrdU) incorporation into DNA and by resistance profiling of soil bacterial isolates on solid media. High Cu exposure selected for Cu-tolerant bacterial communities but also coselected for increased community-level tolerance to tetracycline and vancomycin. Cu-resistant isolates showed significantly higher incidence of resistance to five out of seven tested antibiotics (tetracycline, olaquindox, nalidixic acid, chloramphenicol, and ampicillin) than Cu-sensitive isolates. Our BrdU-PICT data demonstrate for the first time that soil Cu exposure coselects for resistance to clinically important antibiotics (e.g., vancomycin) at the bacterial community-level. Our study further indicates that Cu exposure provides a strong selection pressure for the expansion of the soil bacterial resistome.
Department of Agriculture and Ecology and Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Jeanette
J
Berg
Maja K
MK
Thorsen
Peter E
PE
Holm
John
J
Jensen
Ole
O
Nybroe
Kristian K
KK
Brandt
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D001681:Biological Assay; D003300:Copper / Q000633:toxicity*; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D018570:Risk Assessment; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000633:toxicity*
D000900:Anti-Bacterial Agents; D012987:Soil; D012989:Soil Pollutants; D003300:Copper