Vancomycin-resistant enterococci with vanA and vanB genes in Australian gulls

Enterococci as a One Health indicator of antimicrobial resistance

The rapid increase of antimicrobial-resistant bacteria in humans and livestock is concerning. Antimicrobials are essential for the treatment of disease in modern day medicine, and their misuse in humans and food animals has contributed to an increase in the prevalence of antimicrobial-resistant bacteria. Globally, antimicrobial resistance is recognized as a One Health problem affecting humans, animals, and environment. Enterococcal species are Gram-positive bacteria that are widely distributed in nature. Their occurrence, prevalence, and persistence across the One Health continuum make them an ideal candidate to study antimicrobial resistance from a One Health perspective. The objective of this review was to summarize the role of enterococci as an indicator of antimicrobial resistance across One Health sectors. We also briefly address the prevalence of enterococci in human, animal, and environmental settings. In addition, a 16S RNA gene-based phylogenetic tree was constructed to visualize the evolutionary relationship among enterococcal species and whether they segregate based on host environment. We also review the genomic basis of antimicrobial resistance in enterococcal species across the One Health continuum.

Draft Genome Sequence of Enterococcus dispar CoE-457-22, Isolated from Traditionally Produced Montenegrin Dry Sausage

Enterococcus dispar was isolated for the first time from synovial fluid and stool cultures and described as a new species in 1991. Here, we report the genome of E. dispar CoE-457-22, which was obtained from traditionally produced Montenegrin dry sausage (sudzuk).

Presence and antimicrobial resistance profiles of Escherichia coli, Enterococcusspp. and Salmonellasp. in 12 species of Australian shorebirds and terns

Antibiotic resistance is an ongoing threat to both human and animal health. Migratory birds are a potential vector for the spread of novel pathogens and antibiotic resistance genes. To date, there has been no comprehensive study investigating the presence of antibiotic resistance (AMR) in the bacteria of Australian shorebirds or terns. In the current study, 1022 individual birds representing 12 species were sampled across three states of Australia (Victoria, South Australia, and Western Australia) and tested for the presence of phenotypically resistant strains of three bacteria with potential to be zoonotic pathogens; Escherichia coli, Enterococcusspp., and Salmonellasp. In total, 206 E. coli, 266 Enterococcusspp., and 20 Salmonellasp. isolates were recovered, with AMR detected in 42% of E. coli, 85% of Enterococcusspp., and 10% of Salmonellasp. Phenotypic resistance was commonly detected to erythromycin (79% of Enterococcusspp.), ciprofloxacin (31% of Enterococcusspp.) and streptomycin (21% of E. coli). Resident birds were more likely to carry AMR bacteria than migratory birds (p ≤ .001). Bacteria isolated from shorebirds and terns are commonly resistant to at least one antibiotic, suggesting that wild bird populations serve as a potential reservoir and vector for AMR bacteria. However, globally emerging phenotypes of multidrug‐resistant bacteria were not detected in Australian shorebirds. This study provides baseline data of the carriage of AMR bacteria in Australian shorebirds and terns.

Hiding in plain sight - Wildlife as a neglected reservoir and pathway for the spread of antimicrobial resistance: A narrative review

Antimicrobial resistance represents a global health problem, with infections due to pathogenic antimicrobial resistant bacteria (ARB) predicted to be the most frequent cause of human mortality by 2050. The phenomenon of antimicrobial resistance has spread to and across all ecological niches, and particularly in livestock used for food production with antimicrobials consumed in high volumes. Similarly, hospitals and other healthcare facilities are recognized as significant “hotspots” of ARB and antimicrobial resistance genes (ARGs); however, over the past decade, new and previously overlooked ecological niches are emerging as hidden reservoirs of ARB/ARGs. Increasingly extensive and intensive industrial activities, degradation of natural environments, burgeoning food requirements, urbanization, and global climatic change have all dramatically affected the evolution and proliferation of ARB/ARGs, which now stand at extremely concerning ecological levels. While antimicrobial resistant bacteria and genes as they originate and emanate from livestock and human hosts have been extensively studied over the past 30 years, numerous ecological niches have received considerably less attention. In the current descriptive review, the authors have sought to highlight the importance of wildlife as sources/reservoirs, pathways and receptors of ARB/ARGs in the environment, thus paving the way for future primary research in these areas.

The Role of Gulls as Reservoirs of Antibiotic Resistance in Aquatic Environments: A Scoping Review

The role of wildlife with long-range dispersal such as gulls in the global dissemination of antimicrobial resistance (AMR) across natural and anthropogenic aquatic environments remains poorly understood. Antibiotic-resistant bacteria have been detected in resident and migratory gulls worldwide for more than a decade, suggesting gulls as either sentinels of AMR pollution from anthropogenic sources or independent reservoirs that could maintain and disperse AMR across aquatic environments. However, confirming either of these roles remains challenging and incomplete. In this review, we present current knowledge on the geographic regions where AMR has been detected in gulls, the molecular characterization of resistance genes, and the evidence supporting the capacity of gulls to disperse AMR across regions or countries. We identify several limitations of current research to assess the role of gulls in the spread of AMR including most studies not identifying the source of AMR, few studies comparing bacteria isolated in gulls with other wild or domestic species, and almost no study performing longitudinal sampling over a large period of time to assess the maintenance and dispersion of AMR by gulls within and across regions. We suggest future research required to confirm the role of gulls in the global dispersion of AMR including the standardization of sampling protocols, longitudinal sampling using advanced satellite tracking, and whole-genome sequencing typing. Finally, we discuss the public health implications of the spread of AMR by gulls and potential solutions to limit its spread in aquatic environments.

Antibiotic-Resistant Enterococcus Species in Marine Habitats: A Review

Antibiotic-resistant Enterococcus (ARE) are among leading causes of nosocomial infections worldwide. Enterococcus spp. are ubiquitous in sewage, which can contaminate surface waters via many pathways, providing a route of exposure for humans. This review focuses on ARE in marine and estuarine habitats, including marine animals. Phylogenetic confirmation of the genus Enterococcus and intermediate or full resistance to clinically relevant antibiotics were inclusion criteria. The proportion of resistant isolates varied greatly among antibiotics, for example, 24.2% for ampicillin and 2.4% for vancomycin. The water column contained the highest proportion of ARE observations (18.8%), followed by animal feces and tissues (14.8%), sediment (9.4%), and sand (2.0%). The proportion of multidrug-resistant isolates was the greatest in animal tissue and fecal samples, followed by water and sediments. This review indicates that clinically relevant ARE are present in marine/estuarine habitats and that animals may be important reservoirs.

Vancomycin resistance plasmids affect persistence of Enterococcus faecium in water

Vancomycin resistant enterococci (VRE) cause 20,000 infections annually in the United States, most of which are nosocomial. Recent findings of VRE in sewage-contaminated surface waters demonstrate an alternate route of human exposure, and a possible setting for horizontal gene exchange facilitated by plasmids and other mobile genetic elements. Maintenance of antibiotic resistance genes and proteins may, however, present a fitness cost in the absence of selective pressure, particularly in habitats such as environmental waters that are not optimal for gut-associated bacteria. Nutrient levels, which are transiently elevated following sewage spills, may also affect survival. We tested the hypotheses that nutrients and/or plasmids conferring vancomycin resistance affect Enterococcus faecium survival in river water by measuring decay of strains that differed only by their plasmid, under natural and augmented nutrient conditions. In natural river water, decay rate (log₁₀ reduction) correlated directly with plasmid size; however, plasmid presence and size had no effect on decay rate when nutrients levels were augmented. Under natural nutrient levels, the vancomycin-resistant strain with the largest plasmid (200 kb) decayed significantly more rapidly than the plasmid-less, susceptible parent strain, in contrast to similar decay rates among strains under augmented nutrient conditions. This work is among the first to show that plasmids conferring antibiotic resistance affect fitness of Enterococcus species in secondary habitats such as surface water. The nutrient-dependent nature of the fitness cost suggests that conveyance of VRE to environmental waters in nutrient-rich sewage may prolong survival of these pathogens, providing greater opportunity for host infection and/or horizontal gene transfer.

Phylogenomics of Enterococcus faecalis from wild birds: new insights into host-associated differences in core and accessory genomes of the species

Wild birds have been suggested to be reservoirs of antimicrobial resistant and/or pathogenic Enterococcus faecalis (Efs) strains, but the scarcity of studies and available sequences limit our understanding of the population structure of the species in these hosts. Here, we analysed the clonal and plasmid diversity of 97 Efs isolates from wild migratory birds. We found a high diversity, with most sequence types (STs) being firstly described here, while others were found in other hosts including some predominant in poultry. We found that pheromone-responsive plasmids predominate in wild bird Efs while 35% of the isolates entirely lack plasmids. Then, to better understand the ecology of the species, the whole genome of fivestrains with known STs (ST82, ST170, ST16 and ST55) were sequenced and compared with all the Efs genomes available in public databases. Using several methods to analyse core and accessory genomes (AccNET, PLACNET, hierBAPS and PANINI), we detected differences in the accessory genome of some lineages (e.g. ST82) demonstrating specific associations with birds. Conversely, the genomes of other Efs lineages exhibited divergence in core and accessory genomes, reflecting different adaptive trajectories in various hosts. This pangenome divergence, horizontal gene transfer events and occasional epidemic peaks could explain the population structure of the species.

Wild corvid birds colonized with vancomycin-resistant Enterococcus faecium of human origin harbor epidemic vanA plasmids

The most prevalent type of acquired vancomycin resistance in Enterococcus faecium (VREfm) is encoded by the vanA transposon Tn1546, mainly located on transferable plasmids. vanA plasmids have been characterized in VREfm from a variety of sources but not wild birds. The aim of this study was to analyse the genetic context of VREfm strains recovered from wild corvid birds and to compare their plasmid and strain characteristics with human strains. To achieve that, 75 VREfm isolates, including strains from wild birds recovered during wide surveillance studies performed in Europe, Canada and the United States (2010-2013), and clinical and wastewater strains from Czech Republic, a region lacking data about vanA plasmids, were analysed. Their population structure, presence of major putative virulence markers and characterization of vanA transposons and plasmids were established. VREfm from wild birds were mainly associated with major human lineages (ST18 and ST78) circulating in hospitals worldwide and were enriched in putative virulence markers that are highly associated with clinical E. faecium from human infections. They also carried plasmids of the same families usually found in the clinical setting [RCR, small theta plasmids, RepA_N (pRUM/pLG1) and Inc18]. The clinically widespread IS1251-carrying Tn1546 type "F" was predominant and Tn1546-vanA was mainly located on pRUM/Axe-Txe (USA) and Inc18- or pLG1-like (Europe) plasmids. VREfm from hospitals and wastewaters carried Tn1546-vanA in different plasmid types including mosaic pRUM-Inc18 plasmids, not identified in wild birds. This is the first characterization of vanA plasmids obtained from wild birds. A similar plasmid pool seems to exist in different clonal E. faecium backgrounds of humans and wild birds. The isolation of VREfm strains from wild birds that belong to human E. faecium adapted lineages and carry virulence genes, Tn1546 and plasmid variants widespread in the clinical setting is of concern and highlight their role as potential drivers of the global dissemination of vancomycin resistance.