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Title: Potential pathogens, antimicrobial patterns, and genotypic diversity of Escherichia coli isolates in constructed wetlands treating swine wastewater

item Ibekwe, Abasiofiok - Mark
item MURINDA, S. - California Polytechnic State University
item DEBROY, C. - Pennsylvania State University
item REDDY, G. - North Carolina Agricultural And Technical State University

Submitted to: FEMS Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2016
Publication Date: 7/19/2016
Citation: Ibekwe, A.M., Murinda, S.E., Debroy, C., Reddy, G.B. 2016. Potential pathogens, antimicrobial patterns, and genotypic diversity of Escherichia coli isolates in constructed wetlands treating swine wastewater. FEMS Microbiology Ecology. 92:fiw006. doi: 10.1093/femsec/fiw006.

Interpretive Summary: Constructed wetlands can offer significant benefits such as water-quality improvement, water reclamation, habitat for species conservation, flood control, recreational and education activities for human populations in both developed and developing countries. In the swine production system, wastes are traditionally flushed into an anaerobic lagoon and then sprayed on agricultural fields. The lagoon and spray field system is the most commonly used method to dispose of liquid waste from swine houses. In this study, a marsh-pond-marsh constructed wetland was used to remove contaminants from swine waste. We determined population structure and antibiotic-resistant patterns of E. coli from the swine house through a surface flow constructed wetland used for treatment and removal of contaminants in swine waste. E. coli isolates identified from this study did not contain E. coli O157. However, a few non O157 E. coli and other types of E. coli that may be responsible for travelers’ diarrhea were identified, and some of the strains were resistant to different antibiotics. This information will be of interest to swine farmers, water quality agencies, government agencies, and researchers.

Technical Abstract: The treatment and removal of contaminants such as nutrients, salts, microbes, and pharmaceutically active compounds from swine waste by constructed wetlands involves complex biological processes. However, little is known about the population structure and antibiotic resistant patterns of E. coli emanating from swine house through marsh-pond-marsh constructed wetlands. To assess the impacts of seasonal variations and the effect of the wetland layout/operations on E. coli populations, we compared the genetic diversity and antimicrobial activities of generic E. coli in marsh-pond-marsh constructed wetlands used for treating swine waste. E. coli was enumerated, characterized, and typed from the samples collected from swine house, throughout different sections of the wetland, and the final effluent. Typing of E. coli was done using BOXAIR-1 and REP-PCR followed by antimicrobial activities. None of the isolates was confirmed as Shiga toxin E. coli O157:H7 (STEC), but as others, such as enterotoxigenic E. coli (ETEC). Using a 90% similarity index from BOXAIR-1 PCR, 175 unique genotypes were found, and with REP-PCR, 69 genotypes out of 422 E. coli isolates were found. Our data showed that most of the E. coli strains were without the Shiga toxin genes, but with high distribution of single or multi drug-resistant phenotypes/genotypes. Therefore, the occurrence of E. coli with multiple resistances in the wetland is a matter of great concern due to possible transfer of resistant genes from nonpathogenic to pathogenic strains in the environment.