Transcript
Page 1: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

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

Page 2: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

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

Page 3: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

•  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 µg/kg level) as well as in vegetable produce (at µg/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

Page 4: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

Relation between Tetracycline Speciation and Expression of Antibiotic Resistance Genes

Page 5: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

Uptake of tetracycline (100 µg/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

Tetra

cycli

ne In

trace

llular

Con

c (µ g

/L)

0

10

20

30

40

50

60

70

pH 6 pH 7 pH 8

A

Ca2+ concentration (mM)

0 1 5

Prom

oter A

ctivit

y

0

200

400

600

800

1000

1200

1400

1600

1800

B

Mg2+ concentration (mM)

0 1 5

Tetra

cycli

ne In

trace

llular

Con

c (µ g

/L)

0

10

20

30

40

50

60

70C

Mg2+ concentration (mM)

0 1 5

Prom

oter A

ctivit

y

0

200

400

600

800

1000

1200

1400

1600

1800D

Page 6: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

Tetracycline Zwitterion Concentration (µg/L)0 20 40 60 80 100Te

trac

yclin

e In

trac

ellu

lar C

onc.

(µg/

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

Page 7: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

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?

Page 8: Antibiotics and Antibiotic Resistance: Perspectives from Environmental Soil Chemistry

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?


Top Related