title: Heavy metals in liquid pig manure in light of bacterial antimicrobial resistance.
abstract: Heavy metals are regularly found in liquid pig manure, and might interact with bacterial antimicrobial resistance. Concentrations of heavy metals were determined by atomic spectroscopic methods in 305 pig manure samples and were connected to the phenotypic resistance of Escherichia coli (n=613) against 29 antimicrobial drugs. Concentrations of heavy metals (/kg dry matter) were 0.08-5.30 mg cadmium, 1.1-32.0 mg chrome, 22.4-3387.6 mg copper, <2.0-26.7 mg lead, <0.01-0.11 mg mercury, 3.1-97.3 mg nickel and 93.0-8239.0 mg zinc. Associated with the detection of copper and zinc, resistance rates against β-lactams were significantly elevated. By contrast, the presence of mercury was significantly associated with low antimicrobial resistance rates of Escherichia coli against β-lactams, aminoglycosides and other antibiotics. Effects of subinhibitory concentrations of mercury on bacterial resistance against penicillins, cephalosporins, aminoglycosides and doxycycline were also demonstrated in a laboratory trial. Antimicrobial resistance in the porcine microflora might be increased by copper and zinc. By contrast, the occurrence of mercury in the environment might, due to co-toxicity, act counter-selective against antimicrobial resistant strains.
authors.affiliation: Chair of Animal Hygiene, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany. Christina.Hoelzel@wzw.tum.de
authors.forename: Christina S
authors.initials: CS
authors.lastname: Hölzel
authors.forename: Christa
authors.initials: C
authors.lastname: Müller
authors.forename: Katrin S
authors.initials: KS
authors.lastname: Harms
authors.forename: Sabine
authors.initials: S
authors.lastname: Mikolajewski
authors.forename: Stefanie
authors.initials: S
authors.lastname: Schäfer
authors.forename: Karin
authors.initials: K
authors.lastname: Schwaiger
authors.forename: Johann
authors.initials: J
authors.lastname: Bauer
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004347:Drug Interactions; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D016014:Linear Models; D008372:Manure / Q000032:analysis / Q000382:microbiology*; D019216:Metals, Heavy / Q000032:analysis / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D013054:Spectrophotometry, Atomic / Q000662:veterinary; D013552:Swine / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D008372:Manure; D019216:Metals, Heavy