Antimicrobial Resistance Gene Detection and Plasmid Typing Among Multidrug Resistant Enterococci Isolated from Freshwater Environment.

Sohyun Cho,Charlene R Jackson,Jonathan G Frye,John B Barrett

doi:10.3390/microorganisms8091338

Abstract

In this study, mechanisms of antimicrobial resistance (AR) as well as the abundance and diversity of plasmids were determined among multidrug resistant (MDR) enterococci from surface water in GA, USA. A total of 51 enterococci isolates were screened for the presence of 27 AR genes conferring resistance to ciprofloxacin, erythromycin, tylosin, kanamycin, streptomycin, lincomycin, Quinupristin/Dalfopristin (Q/D), and tetracycline. A plasmid classification system based on replication genes was used to detect 19 defined Gram-positive plasmid replicon families. Twelve genes were identified as conferring resistance to erythromycin and tylosin (erm(B) and erm(C)), kanamycin (aph(3′)-IIIa), streptomycin (ant(6)-Ia), lincomycin (lnu(B)), Q/D (vat(E)), ciprofloxacin (qnrE. faecalis), and tetracycline (tet(K), tet(L), tet(M), tet(O) and tet(S)). Twelve different rep-families were identified in two-thirds of the isolates. While AR genes commonly found in human and animals were detected in this study among environmental enterococci, resistance genes could not be determined for many of the isolates, which indicates that diverse AR mechanisms exist among enterococci, and the understanding of AR mechanisms for environmental enterococci is limited. Diverse rep-families were identified among the enterococci recovered from the aquatic environment, and these rep-families appear to be quite different from those recovered from other sources. This work expands knowledge of AR gene reservoirs and enterococcal plasmids across a wider range of environments.

Highlights

Enterococci are Gram-positive bacteria that are a part of the intestinal microbiota of warm-blooded animals
The treatment of enterococcal infections is often complicated by antimicrobial resistant enterococci, those that are resistant to multiple drugs, and this is a major problem for public health worldwide as it results in limited therapeutic options [2]
A limited number of studies on environmental enterococci are mostly focused on water environments polluted by human inputs, such as wastewater, on species that are associated with human infections, such as E. faecalis and E. faecium, and on certain antimicrobial drugs, such as vancomycin [4,5,6,7]

Summary

Introduction

Enterococci are Gram-positive bacteria that are a part of the intestinal microbiota of warm-blooded animals. The treatment of enterococcal infections is often complicated by antimicrobial resistant enterococci, those that are resistant to multiple drugs, and this is a major problem for public health worldwide as it results in limited therapeutic options [2]. Antimicrobial resistant enterococci released into surface water through human and agricultural wastes are a public health concern, due to human exposure to these bacteria through water-related activities, and due to potential dissemination of genes encoding AR to other bacteria present in the environment. A limited number of studies on environmental enterococci are mostly focused on water environments polluted by human inputs, such as wastewater, on species that are associated with human infections, such as E. faecalis and E. faecium, and on certain antimicrobial drugs, such as vancomycin [4,5,6,7]. Monitoring resistant enterococci present in the environment and investigating a potential transfer of AR determinants to other bacteria in the same niche would enhance the understanding of AR from the one health perspective [11]

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Conclusion