The impact of antibiotic residues on resistance patterns in leek at harvest
Judith Huygens,
Geertrui Rasschaert,
Bart Cottyn,
Jeroen Dewulf,
Els Van Coillie,
Koen Willekens,
Paul Quataert,
Ilse Becue,
Els Daeseleire,
Marc Heyndrickx
Affiliations
Judith Huygens
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium
Geertrui Rasschaert
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium; Corresponding author.
Bart Cottyn
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Plant Science Unit, Caritasstraat 39, 9090 Melle, Belgium
Jeroen Dewulf
Ghent University, Faculty of Veterinary Medicine, Department of Internal Medicine, Reproduction an Population Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium
Els Van Coillie
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium
Koen Willekens
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Plant Science Unit, Caritasstraat 39, 9090 Melle, Belgium
Paul Quataert
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Plant Science Unit, Caritasstraat 39, 9090 Melle, Belgium
Ilse Becue
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium
Els Daeseleire
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium
Marc Heyndrickx
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium; Ghent University, Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Salisburylaan 133, 9820 Merelbeke, Belgium
When crops are cultivated on fields fertilized with animal manure, the risk exists that plants may take up antibiotic residues and may be exposed to antibiotic resistance genes and antibiotic resistant bacteria. During cultivation in a greenhouse pot experiment, leek (Allium porrum) was fertilized with either pig slurry or mineral fertilizer and exposed to either no antibiotics, doxycycline (10,000 μg/kg manure), sulfadiazine (1000 μg/kg manure), or lincomycin (1000 μg/kg manure). At harvest, 4.5 months later, lincomycin, sulfadiazine or doxycycline were not detected in any of the leek samples nor in their corresponding soil samples. Further, antimicrobial susceptibility testing was performed on 181 Bacillus cereus group isolates and 52 Pseudomonas aeruginosa isolates from the grown leek. For the B. cereus group isolates, only a small shift in MIC50 for lincomycin was observed among isolates from the lincomycin and control treatment. For P. aeruginosa, only in the setup with doxycycline treatment a higher MIC50 for doxycycline was observed compared to the control, specifically the isolates selected from growth media supplemented with 8 mg/L doxycycline. Nine antibiotic resistance genes (tet(B), tet(L), tet(M), tet(O), tet(Q), tet(W), erm(B), erm(F) and sul2) were investigated at harvest in the leek and soil samples. In the leek samples, none of the antibiotic resistance genes were detected. In the soil samples fertilized with pig slurry, the genes erm(B), erm(F), tet(M), sul2, tet(W) and tet(O) were detected in significantly higher copy numbers in the lincomycin treatment as compared to the other antibiotic treatments. This could be due to a shift in soil microbiota induced by the addition of lincomycin. The results of this study indicate that consumption of leek carries a low risk of exposure to antibiotic residues or antibiotic resistance to doxycycline, sulfadiazine or lincomycin.
