Stephen A. Boyd, University Distinguished Professor, Crop and Soil Sciences; Hui Li, associate professor, Plant, Soil and Microbial Sciences; Brian J. Teppen, professor, Crop and Soil Sciences; Wei Zhang, assistant professor, Plant Soil and Microbial Sciences;

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. 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. • 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

4. Relation between Tetracycline Speciation and Expression
of Antibiotic Resistance Genes

5. 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
TetracyclineIntracellularConc(µg/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(µg/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. Tetracycline Zwitterion Concentration (µg/L)
0 20 40 60 80 100
TetracyclineIntracellularConc.(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

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. 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?