Examining antimicrobial resistance in Escherichia coli: a case study in Central Virginia’s environment

Authors: KIM, CHYER - Virginia State University; RILEY, ALLISSA - Virginia State University; SRIHARAN, SHOBHA - Virginia State University; NARTEA, THERESA - Virginia State University; NDEGWA, EUNICE - Virginia State University; DHAKAL, RAMESH - Virginia State University; ZHENG, GUOLU - Lincoln University Of Missouri; Baffaut, Claire

Submitted to: Antibiotics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2024
Publication Date: 2/28/2024
Citation: Kim, C., Riley, A., Sriharan, S., Nartea, T., Ndegwa, E., Dhakal, R., Zheng, G., Baffaut, C. 2024. Examining antimicrobial resistance in Escherichia coli: a case study in Central Virginia’s environment. Antibiotics. 13(3):223. https://doi.org/10.3390/antibiotics13030223.
DOI: https://doi.org/10.3390/antibiotics13030223

Interpretive Summary: Medical treatment and prevention of infections caused by microbial, viral, and fungal infections has resulted in the bacteria, viruses, and fungi becoming resistant to the drugs used. Antimicrobial resistance (AMR) is a public health threat predicted to cause 10 million deaths worldwide annually by 2050. While environmental factors may contribute to AMR in bacteria, many aspects of environmental antibiotic pollution and resistance remain unknown. This study aimed to assess AMR variance in E. coli isolated from diverse environmental samples, such as livestock feces, wild avian feces, water from wastewater treatment plants (WWTP), and water from drainage areas of different land use systems (crop, forest, pasture, and urban land) in Central Virginia. A total of 450 E. coli strains were tested for their susceptibility to 12 antibiotics approved by the US Food and Drug Administration for clinical use. Approximately 88% of the strains were resistant to at least one antibiotic, with 3% of the strains showing multi-drug resistance. Resistance to streptomycin was the most common (73% of the strains), while chloramphenicol was effective for 98% of the strains. One strain obtained from WWTP was resistant to seven antibiotics. AMR was highest among the WWTP strains, followed by drainage areas with different land use, wild avian, and livestock. For livestock, AMR was the highest for horses and lowest for cattle. No significant difference in AMR was found across the different land use systems. This study identifies potential AMR hotspots, emphasizing the environmental risk for AMR E. coli. The findings aid policymakers and researchers, highlighting knowledge gaps in AMR-environment links. This nationally relevant research offers a scalable AMR model for understanding E. coli ecology. Further large-scale research is crucial to confirm environmental impacts on AMR prevalence in bacteria.

Technical Abstract: While environmental factors may contribute to antimicrobial resistance (AMR) in bacteria, many aspects of environmental antibiotic pollution and resistance remain unknown. Furthermore, the level of AMR in Escherichia coli is considered a reliable indicator of the selection pressure exerted by antimicrobial use in the environment. This study aimed to assess AMR variance in E. coli isolated from diverse environmental samples, such as animal feces and water from wastewater treatment plants (WWTPs) and drainage areas of different land use systems in Central Virginia. In total, 450 E. coli isolates obtained between August 2020 and February 2021 were subjected to susceptibility testing against 12 antimicrobial agents approved for clinical use by the U.S. Food and Drug Administration. Approximately 87.8% of the tested isolates were resistant to at least one antimicrobial agent, with 3.1% showing multi-drug resistance. Streptomycin resistance was the most common (73.1%), while susceptibility to chloramphenicol was the highest (97.6%). One isolate obtained from WWTPs exhibited resistance to seven antimicrobials. AMR prevalence was the highest in WWTP isolates, followed by isolates from drainage areas, wild avians, and livestock. Among livestock, horses had the highest AMR prevalence, while cattle had the lowest. No significant AMR difference was found across land use systems. This study identifies potential AMR hotspots, emphasizing the environmental risk for antimicrobial resistant E. coli. The findings will aid policymakers and researchers, highlighting knowledge gaps in AMR–environment links. This nationally relevant research offers a scalable AMR model for understanding E. coli ecology. Further large-scale research is crucial to confirm the environmental impacts on AMR prevalence in bacteria.