title: Accumulation of antibiotics and heavy metals in meat duck deep litter and their role in persistence of antibiotic-resistant Escherichia coli in different flocks on one duck farm.
abstract: Meat duck deep litter is considered to be an ideal environment for the evolution of bacterial antibiotic resistance if it is under poor management. The aim of this study was to characterize the accumulation of antibiotics and heavy metals in the deep litter and their role in the persistence of antibiotic resistance of Escherichia coli, and evaluate the service life of the deep litter. Samples were collected from initial, middle, and final stages of deep litter within 3 barns (zero, 4, and 8 rounds of meat duck fattening, d 34) and 9 flocks, with known consumption of antibiotics in the controlled trail. The feed and litter levels of consumed antibiotics and heavy metals were measured. E. coli (n = 147) was isolated and typed by Eric-PCR and the phylogenetic grouping technique, while minimal inhibitory concentrations of antibiotics and heavy metals were measured. This study confirmed the continuous accumulation of doxycycline and many heavy metals in the deep litter. The population of resistant certain bacteria to doxycycline (16 mg/L, 100 mg/L) or ofloxacin (8 g/mL, 50 g/mL) increased in the used deep litter (rounds 4 and 8). E. coli isolated from the 3 stages of sampling were highly resistant to ampicillin, tetracycline, florfenicol, and doxycycline. Increased resistance to ceftiofur, enrofloxacin, ofloxacin, and gentamicin were seen in the isolates from the final stage of deep litter. In addition, the percentage of isolates tolerant to zinc, copper, and cadmium and the numbers of Group-B2 isolates all increased in the used deep litter, and the isolates of each stage belonged predominantly to commensal groups. The antibiotic resistance of isolates with identical Eric-PCR patterns had improved from round 4 to 8, and differences still existed in the resistance profiles of isolates with identical Eric-PCR patterns from different barns of the same round. This study concluded that deep litter could be suitable for the evolution of bacterial antibiotic-resistance under conditions of continuous usage or accumulation of antibiotics and heavy metals without proper management.
authors.affiliation: College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu, China.|Key Laboratory of Animal Breeding and Reproduction, Institute of Livestock Science, Jiangsu Academy of Agricultural Sciences, Jiangsu, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Key Laboratory of Animal Breeding and Reproduction, Institute of Livestock Science, Jiangsu Academy of Agricultural Sciences, Jiangsu, China.
authors.forename: W
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Animal Breeding and Reproduction, Institute of Livestock Science, Jiangsu Academy of Agricultural Sciences, Jiangsu, China.
authors.forename: Z D
authors.initials: ZD
authors.lastname: Shi
authors.affiliation: Key Laboratory of Animal Breeding and Reproduction, Institute of Livestock Science, Jiangsu Academy of Agricultural Sciences, Jiangsu, China.
authors.forename: H R
authors.initials: HR
authors.lastname: Gu
authors.affiliation: College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu, China.
authors.forename: X T
authors.initials: XT
authors.lastname: Zhang
authors.affiliation: College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu, China.
authors.forename: X
authors.initials: X
authors.lastname: Ji
authors.affiliation: College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu, China.
authors.forename: X T
authors.initials: XT
authors.lastname: Zou
authors.affiliation: Poultry Institute, Chinese Academy of Agricultural Sciences, Yangzhou, Jiangsu, China.
authors.forename: J S
authors.initials: JS
authors.lastname: Gong
authors.affiliation: College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu, China.
authors.forename: W
authors.initials: W
authors.lastname: Yao
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis* / Q000494:pharmacology; D004318:Doxycycline / Q000032:analysis / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial; D004372:Ducks / Q000382:microbiology*; D004785:Environmental Pollutants / Q000032:analysis*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D006799:Housing, Animal; D019216:Metals, Heavy / Q000032:analysis*; D015242:Ofloxacin / Q000032:analysis / Q000494:pharmacology; D013839:Thiamphenicol / Q000031:analogs & derivatives / Q000032:analysis / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004785:Environmental Pollutants; D019216:Metals, Heavy; C035534:florfenicol; D015242:Ofloxacin; D013839:Thiamphenicol; D004318:Doxycycline
keywords: E. coli; antibiotic; deep litter; heavy metal; resistance