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Distribution of MRSA and ESBL E. coli in a constructed variable-flow wetland
Citation:
Pemberton, A., B. McMinn, J. Kelleher, AND A. Korajkic. Distribution of MRSA and ESBL E. coli in a constructed variable-flow wetland. ASM Microbe 2023, Houston, TX, June 15 - 19, 2023.
Impact/Purpose:
The purpose of this research project was to assess loading and distribution of antibiotic resistant bacteria in a constructed wetland designed to treat wastewater impacted creek.
Description:
Background: Antimicrobial resistance is an emerging threat to global public health. Specifically, methicillin resistant Staphylococcus aureus (MRSA) and extended spectrum beta-lactamase (ESBL) resistant Escherichia coli have been identified as current serious threat pathogens of interest. Constructed wetlands are economical, natural means of reducing microbial contamination, but relatively little is known about the fate of MRSA and ESBL E. coli in these systems. Methods: Banklick Creek wetland is variable-flow system treating wastewater-impacted creek in Northern Kentucky. Putative MRSA and ESBL E. coli were enumerated from water and sediment samples collected from inflow, outflow and five treatment sites within the Banklick Creek wetland on a biweekly basis (n=91). A subset of MRSA (n= 248) and ESBL E. coli (n= 112) were also subjected to multidrug resistance (MDR) testing, defined as resistance to at least three antibiotics. Results: Both ESBL E. coli and MRSA were consistently detected in the water column and sediments at all sites and concentrations of both were significantly higher in latter (p < 0.0001). Irrespective of the matrix 100% of ESBL E. coli were resistant to ampicillin, followed by amoxicillin/clavulonic acid (89.9%), cefepime (51.4%) and imipenem (40.4%), and no isolates displayed resistance to ertapenem and meropenem. Resistance to aminoglycosides and quinolones (p ≤ 0.0321) was more prevalent in the water column than sediments, but opposite was the case for tetracyclines (p = 0.0014). Nearly 74% of ESBL E. coli displayed MDR, but there was no significant difference between water column and sediments. Of MRSA isolated from water column and sediments 99.2% were resistant to clindamycin, followed by quinupristin/dalfopristin (89.1%), pirlimycin (77.0%), erythromycin (47.6%), ciprofloxacin (47.2%) and azithromycin (40.7%). Majority (83%) of MRSA were MDR, and significantly more so in the water column compared to sediments (p = 0.0212). Discussion: We did not observe any reduction in ESBL E. coli and MRSA concentrations, likely signifying different inputs from waterfowl and wildlife throughout the wetland. Furthermore, higher concentrations of MRSA, including MDR MRSA, and ESBL E. coli in sediments than the overlaying water column, indicates extended persistence and suggests they may act as reservoirs of these serious threat pathogens. Differential distribution of antibiotic resistance in the water column vs sediments, indicates differential survival characteristics between the two matrices.
