Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

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  1. 1. Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry Stephen A. Boyd, Hui Li, Brian J. Teppen, Wei Zhang Department of Plant, Soil and Microbial Sciences Michigan State University
  2. 2. Pathways for Pharmaceuticals into the Environment Antibiotics Human treatments Aquaculture Inappropriate disposal of unused medicines Manure and slurry spreading Municipal wastewater treatment Storage of manure and slurry Livestock feeding and treatments
  3. 3. Using LC-MS/MS techniques, we have developed analytical protocols to quantify many types of antibiotics present in water (at ng/L level), in soils and biosolids (at g/kg level) as well as in vegetable produce (at g/kg level). Research question: How widespread are antibiotics in our food chain? Provide collaboration with projects which need analytical chemistry components for screening and quantification of chemicals of emerging concern (CECs). Identification and Quantification of Antibiotics in Environmental Matrices and Food Produce
  4. 4. Relation between Tetracycline Speciation and Expression of Antibiotic Resistance Genes
  5. 5. Uptake of tetracycline (100 g/L) by E. Coli bioreporter in the presence of (A) Ca2+ and (C) Mg2+, and the corresponding expression of antibiotic resistance genes (B and D) Ca2+ concentration (mM) 0 1 5 TetracyclineIntracellularConc(g/L) 0 10 20 30 40 50 60 70 pH 6 pH 7 pH 8 A Ca2+ concentration (mM) 0 1 5 PromoterActivity 0 200 400 600 800 1000 1200 1400 1600 1800 B Mg2+ concentration (mM) 0 1 5 TetracyclineIntracellularConc(g/L) 0 10 20 30 40 50 60 70 C Mg2+ concentration (mM) 0 1 5 PromoterActivity 0 200 400 600 800 1000 1200 1400 1600 1800 D
  6. 6. Tetracycline Zwitterion Concentration (g/L) 0 20 40 60 80 100 TetracyclineIntracellularConc.(g/g) 0 20 40 60 80 100 120 Bacterial uptake of tetracycline (and expression of antibiotic resistance genes) is strongly correlated with its zwitterionic form
  7. 7. Hypothesis: The neutral (zwitterionic) species of tetracycline (L) is more bioavailable to E. coli Research questions: 1) Given that manure contains many metals as well as many complexing ligands to compete with the antibiotic, how might management conditions be manipulated to minimize bioavailability? 2) Do other antibiotics and bacteria follow similar patterns? 3) How bioavailable are sorbed antibiotics, and could in-situ geosorbent amendments be used to reduce antibiotic uptake and selective pressure?
  8. 8. Bacteria could acquire antibiotic resistance genes via horizontal gene transfer. Environmental chemistry research questions: Knapp, et al., Environ. Sci. Technol. 2010; 44: 580-587 1.How stable (persistent) are these antibiotic resistance genes in soils? 2.Effects of sorbent? 3.Are the soil-sorbed genes still bioactive, and available for transfer into bacterial cells to develop antibiotic resistance?

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