Other Project Number:
7/1/2010 - 6/30/2012
- Zhaohui Li, UW-Parkside
- Maria MacWilliams, UW-Parkside
Frequent use of antibiotics in livestock production will cause soil and groundwater contamination by these pharmaceuticals. In Wisconsin alone, 80% of the samples from selected wastewater treatment facilities were tested positive for tetracycline (TC) and oxytetracycline (OTC). Previous studies showed that sorption of TCs by swelling clays resulted in an interlayer expansion as much as 11 Å. The high affinity of TCs for clay minerals may alter their antimicrobial activity to common soil bacteria. As the soil is a mixture of different clay minerals (both swelling and non-swelling) and humus materials, the sorption of antibiotics may occur on different site via different sorption mechanisms. We hypothesize that TCs sorbed on different sites of different clay minerals may contribute to different antibiotic activities and induce different resistance for bacteria. Thus, through this study we plan to answer the following questions: (1) what is the desorption kinetics of the pharmaceuticls sorbed on the external surfaces of non-swelling clays and intercalated in the interlayer spaces of swelling clays? (2) What are the antimicrobial activities of the antibiotics sorbed on external surfaces of intercalated into the interlayer spaces of clay minerals? (3) Will soil microbes develop resistance to the antibiotics sorbed on external surfaces or intercalated into the interlayer spaces of clay minerals? (4) What are the genes responsible for development of resistance to the antibiotics sorbed on external surfaces or intercalated into the interlayer spaces of clay minerals? It is anticipated that our results will complement with current studies on TC resistance developed by soil bacteria and be beneficiary to future studies on antibiotic removal from water. If proven that the antimicrobial activity of TCs sorbed by these clay minerals remains, further evaluated for their potential use as antibiotic additives to enhance drug delivery in animal feeding industry could be initiated.