Linezolid resistance in Enterococcus faecium and Enterococcus faecalis from hospitalized patients in Ireland: high prevalence of the MDR genes optrA and poxtA in isolates with diverse genetic backgrounds

Identification of an Enterococcus faecium strain isolated from raw bovine milk co-harbouring the oxazolidinone resistance genes optrA and poxtA in China

Oxazolidinones are potent antimicrobial agents used to treat human infections caused by multidrug-resistant Gram-positive bacteria. The growing resistance to oxazolidinones poses a significant threat to public health. In August 2021, a linezolid-resistant Enterococcus faecium BN83 was isolated from a raw milk sample of cow in Inner Mongolia, China. This isolate exhibited a multidrug resistance phenotype and was resistant to most of drugs tested including linezolid and tedizolid. PCR detection showed that two mobile oxazolidinones resistance genes, optrA and poxtA, were present in this isolate. Whole genome sequencing analysis revealed that the genes optrA and poxtA were located on two different plasmids, designated as pBN83-1 and pBN83-2, belonging to RepA_N and Inc18 families respectively. Genetic context analysis suggested that optrA gene on plasmid pBN83-1 was located in transposon Tn6261 initially found in E. faecalis. Comprehensive analysis revealed that Tn6261 act as an important horizontal transmission vector for the spread of optrA in E. faecium. Additionally, poxtA-bearing pBN83-2 displayed high similarity to numerous plasmids from Enterococcus of different origin and pBN83-2-like plasmid represented a key mobile genetic element involved in movement of poxtA in enterococcal species. The presence of optrA- and poxtA-carrying E. faecium in raw bovine milk represents a public health concern and active surveillance is urgently warranted to investigate the prevalence of oxazolidinone resistance genes in animal-derived food products.

Genomic epidemiology reveals multiple mechanisms of linezolid resistance in clinical enterococci in China

BACKGROUND

Infections caused by linezolid-resistant enterococci (LRE) are clinically difficult to treat and threaten patient health. However, there is a lack of studies on long time-span LRE strains in China. For this reason, our study comprehensively revealed the resistance mechanisms of LRE strains collected in a Chinese tertiary care hospital from 2011 to 2022.

METHODS

Enterococcal strains were screened and verified after retrospective analysis of microbial data. Subsequently, 65 LRE strains (61 Enterococcus faecalis and 4 Enterococcus faecium, MIC ≥ 8 µg/ml), 1 linezolid-intermediate Enterococcus faecium (MIC = 4 µg/ml) and 1 linezolid-susceptible Enterococcus faecium (MIC = 1.5 µg/ml) were submitted for whole-genome sequencing (WGS) analysis and bioinformatics analysis.

RESULTS

The optrA gene was found to be the most common linezolid resistance mechanism in our study. We identified the wild-type OptrA and various OptrA variants in 98.5% of LRE strains (61 Enterococcus faecalis and 3 Enterococcus faecium). We also found one linezolid-resistant Enterococcus faecium strain carried both optrA and cfr(D) gene, while one linezolid-resistant Enterococcus faecium only harbored the poxtA gene. Most optrA genes (55/64) were located on plasmids, with impB-fexA-optrA, impB-fexA-optrA-erm(A), fexA-optrA-erm(A), and fexA-optrA segments. A minority of optrA genes (9/64) were found on chromosomes with the Tn6674-like platform. Besides, other possible linezolid resistance-associated mechanisms (mutations in the rplC and rplD genes) were also found in 26 enterococcal strains.

CONCLUSIONS

Our study suggested that multiple mechanisms of linezolid resistance exist among clinical LRE strains in China.

Promiscuous, persistent and problematic: insights into current enterococcal genomics to guide therapeutic strategy

Vancomycin-resistant enterococci (VRE) are major opportunistic pathogens and the causative agents of serious diseases, such as urinary tract infections and endocarditis. VRE strains mainly include species of Enterococcus faecium and E. faecalis which can colonise the gastrointestinal tract (GIT) of patients and, following growth and persistence in the gut, can transfer to blood resulting in systemic dissemination in the body. Advancements in genomics have revealed that hospital-associated VRE strains are characterised by increased numbers of mobile genetic elements, higher numbers of antibiotic resistance genes and often lack active CRISPR-Cas systems. Additionally, comparative genomics have increased our understanding of dissemination routes among patients and healthcare workers. Since the efficiency of currently available antibiotics is rapidly declining, new measures to control infection and dissemination of these persistent pathogens are urgently needed. These approaches include combinatory administration of antibiotics, strengthening colonisation resistance of the gut microbiota to reduce VRE proliferation through commensals or probiotic bacteria, or switching to non-antibiotic bacterial killers, such as bacteriophages or bacteriocins. In this review, we discuss the current knowledge of the genomics of VRE isolates and state-of-the-art therapeutic advances against VRE infections.

Relationship Between COVID-19 and Linezolid-Resistant Enterococci: A Retrospective Single-Center Study

AIM AND OBJECTIVES

To evaluate the correlation between whether the COVID-19 pandemic turned out to be a great premise for increasing the incidence of linezolid resistance infections.

MATERIALS AND METHOD

The current retrospective study included data from March 2018 to March 2023 from a single center. The clinical records of the patients were reviewed to extract clinical data. Data gathered from medical records included demographic information, the type of specimen taken, the organism identified, and its sensitivity. Antibiotic susceptibility testing and bacterial identification are both done using the fully automated VITEK system.

RESULTS

The total number of samples collected in all the groups, i.e., Group 1 (PRE-COVID), Group 2 (COVID), and Group 3 (POST-COVID), were 201, 127, and 1315, respectively. Out of a total of 201 samples in Group 1, i.e., from March 2018 to February 2020, 47 (23.38%) samples were collected from blood, 104 (51.74%) samples were collected from urine, and the rest of the samples were collected from other sources (pus, sputum, wound, stool, pleural fluid, etc.). In Group 2, i.e., from March 2020 to February 2021, the total number of samples collected was 127, of which 21 were collected from blood, 86 were from urine, and the remaining 20 samples were from other sources. A total of 1315 samples were collected between March 2021 and February 2023, i.e., in Group 3, 598 samples were collected from blood and 548 samples from urine. The most common isolates in the study were Enterococcus faecalis (35.7%) and Enterococcus faecium (61.0%).

CONCLUSION

A new threat seems to be emerging in the era of COVID-19, the Enterococcus genus. Though the mechanism remains unidentified, the viral infection seems to cause changes in the bacterial flora, favoring Enterococcus and increasing gut permeability, which provides the perfect environment for Enterococcus bacteria to develop invasive infections. In our study, the prevalence of linezolid resistance was 18.2% for five years.

Genomic characteristics of cfr and fexA carrying Staphylococcus aureus isolated from pig carcasses in Korea

The emergence of transferable linezolid resistance genes poses significant challenges to public health, as it does not only confer linezolid resistance but also reduces susceptibility to florfenicol, which is widely used in the veterinary field. This study evaluated the genetic characteristics of linezolid-resistant Staphylococcus aureus strains isolated from pig carcasses and further clarified potential resistance and virulence mechanisms in a newly identified sequence type. Of more than 2500 strains isolated in a prior study, 15 isolated from pig carcasses exhibited linezolid resistance (minimum inhibitory concentration ≥ 8 mg/L). The strains were characterized in detail by genomic analysis. Linezolid-resistant S. aureus strains exhibited a high degree of genetic lineage diversity, with one strain (LNZ_R_SAU_64) belonging to ST8004, which has not been reported previously. The 15 strains carried a total of 21 antibiotic resistance genes, and five carried mecA associated with methicillin resistance. All strains harbored cfr and fexA, which mediate resistance to linezolid, phenicol, and other antibiotics. Moreover, the strains carried enterotoxin gene clusters, including the hemolysin, leukotoxin, and protease genes, which are associated with humans or livestock. Some genes were predicted to be carried in plasmids or flanked by ISSau9 and the transposon Tn554, thus being transmittable between staphylococci. Strains carrying the plasmid replicon repUS5 displayed high sequence similarity (99%) to the previously reported strain pSA737 in human clinical samples in the United States. The results illustrate the need for continuous monitoring of the prevalence and transmission of linezolid-resistant S. aureus isolated from animals and their products.

Synthesis and Evaluation of Imidazole Derivatives Bearing Imidazo[2,1-b] [1,3,4]thiadiazole Moiety as Antibacterial Agents

BACKGROUND

Drug-resistant infections kill hundreds of thousands of people globally every year. In previous work, we found that tri-methoxy- and pyridine-substituted imidazoles show strong antibacterial activities.

OBJECTIVE

The aim of this work was to investigate the antibacterial activities and bacterial resistances of imidazoles bearing an aromatic heterocyclic, alkoxy, or polycyclic moiety on the central ring.

METHODS

Three series of 2-cyclopropyl-5-(5-(6-methylpyridin-2-yl)-2-substituted-1H-imidazol-4- yl)-6-phenylimidazo[2,1-b][1,3,4]thiadiazoles (13a-e, 14a-d, and 15a-f) were synthesized and their antibacterial activity was evaluated. The structures were confirmed by their 1H NMR, 13C NMR, and HRMS spectra. All the synthesized compounds were screened against Gram-positive, Gramnegative, and multidrug-resistant bacterial strains.

RESULTS

More than half of the compounds showed moderate or strong antibacterial activity. Among them, compound 13e (MICs = 1-4 μg/mL) showed the strongest activity against Gram-positive and drug-resistant bacteria as well as high selectivity against Gram-negative bacteria. Furthermore, it showed no cytotoxicity against HepG2 cells, even at 100 μM, and no hemolysis at 20 μM.

CONCLUSION

These results indicate that compound 13e is excellent candicate for further study as a potential antibacterial agent.

One health genomic insights into the host-specific evolution and cross-host transmission of Staphylococcus aureus in animal farm environments, food of animal origin, and humans

OBJECTIVES

Staphylococcus aureus is an opportunistic pathogen that is considered a high priority for research. However, comparative studies of S. aureus strains from different environments and hosts are still lacking.

METHODS

Here, we performed a high-resolution bioinformatics analysis of 576 S. aureus genomes isolated from livestock, farm environments, farm workers, animal-origin food, and humans.

RESULTS

The S. aureus isolates showed high diversity in genetic lineages and demonstrated host specialization and multi-host range in the population phylogeny. Recent transmission events, historical divergences, and frequent host switching in specific sequence types (STs) and through the food chain and animal farm mediums were observed. Frequent gene transfer may quickly give rise to new fitness to colonize their host or switch to other hosts, even in isolates with the closest vertical evolutionary history. The large multi-host-shared antibiotic resistance gene (ARG) pool was the major factor shaping antibiotic resistance in S. aureus isolates. We revealed the genetic backgrounds of mec, cfr, and optrA, which could be spread among isolates from different species, hosts, and environments.

CONCLUSION

Overall, our findings provide One Health genomic insights into the evolution, transmission, gene content characteristics, and antibiotic resistance profiles of S. aureus from different hosts, suggesting that, despite well-formed host specificity during the evolution of S. aureus, the ever-expanding host range and the cross-hosts/niches transmission (at both the strain and genetic level) may be facilitated by diverse bacterial vehicles (e.g., food chain, farm environments, and workers), which will lead to emerging antibiotic resistance consequences and threaten public health and food safety.

CHROMAgar™ LIN-R as an efficient screening tool to assess the prevalence of linezolid-resistant enterococci in German hospital patients-a multicentre study approach, 2021-2022

BACKGROUND

In recent years, an increasing number of linezolid-resistant enterococci (LRE) was recognized at the German National Reference Centre (NRC) for Enterococci. National guidelines on infection prevention recommend screening for LRE in epidemiologically linked hospital settings without referring to a reliable and rapid diagnostic method. Since 2020, CHROMAgar™ provide a chromogenic linezolid screening agar, LIN-R, suitable to simultaneously screen for linezolid-resistant staphylococci and enterococci.

OBJECTIVES

To assess the applicability of CHROMAgar™ LIN-R in clinical settings for detecting LRE directly from patient material and to infer prevalence rates of LRE amongst German hospital patients.

METHODS

During the 3-month trial period, clinical samples were plated on CHROMAgar™ LIN-R. Antimicrobial susceptibility testing was performed using VITEK2 or disc diffusion. At the NRC, linezolid resistance was determined by broth microdilution, multiplex-PCR for cfr/optrA/poxtA and by a restriction-based assay for 23S rDNA mutations.

RESULTS

The 12 participating study sites used 13 963 CHROMAgar™ LIN-R plates during the study period. Of 442 presumptive LRE, 192 were confirmed by phenotypic methods. Of these, 161 were received by the NRC and 121 (75%) were verified as LRE. Most of LR-E. faecium 53/81 (65%) exhibited a 23S rRNA gene mutation as the sole resistance-mediating mechanism, whereas optrA constituted the dominant resistance trait in LR-E. faecalis [39/40 (98%)]. Prevalence of LRE across sites was estimated as 1% (ranging 0.18%-3.7% between sites).

CONCLUSIONS

CHROMAgar™ LIN-R represents a simple and efficient LRE screening tool in hospital settings. A high proportion of false-positive results demands validation of linezolid resistance by a reference method.

Carriage of linezolid-resistant enterococci (LRE) among humans and animals in Nigeria: coexistence of the cfr, optrA, and poxtA genes in Enterococcus faecium of animal origin

OBJECTIVES

In contrast to increasing reports of the emergence of linezolid-resistant enterococci (LRE) emanating from many countries in Europe, Asia, and North America, data on its status and dissemination from the African continent remain scarce, with the information available limited to countries in North Africa. This study investigated the carriage of LRE and the genetic mechanism of resistance among Enterococcus faecium and Enterococcus faecalis strains recovered from humans and animals in Makurdi, Nigeria.

METHODS

We conducted a cross-sectional study between June 2020 and July 2021 during which 630 non-duplicate human and animal faecal samples were collected and processed for the recovery of LRE. The genetic mechanisms for resistance were investigated using polymerase chain reaction (PCR) and Sanger sequencing.

RESULTS

Linezolid-resistant enterococci were recovered from 5.87% (37/630; 95% CI: 4.17-8.00) of the samples, with the prevalence in animals and humans being 6.22% [(28/450); 95% CI: 4.17-8.87] and 5.00% [(9/180); 95% CI: 2.31-9.28], respectively. All isolates remained susceptible to vancomycin. No known point mutation mediating linezolid resistance was detected in the 23S rRNA and ribosomal protein genes; however, acquisition of one or more potentially transferable genes (cfr, optrA, and poxtA) was observed in 26 of the 37 LRE isolates. Co-existence of all three transferable genes in a single isolate was found in four E. faecium strains of animal origin.

CONCLUSION

This study provides baseline evidence for the emergence and active circulation of LRE driven majorly by the acquisition of the optrA gene in Nigeria. To the best of our knowledge, our study is the first to report a co-carriage of all three transferable linezolid resistance determinants in E. faecium. Active LRE surveillance is urgently required to understand the extent of LRE spread across sub-Saharan Africa and to develop tailored mitigation strategies.

Top-Down Genomic Surveillance Approach To Investigate the Genomic Epidemiology and Antibiotic Resistance Patterns of Enterococcus faecium Detected in Cancer Patients in Arkansas

Control of hospital-associated Enterococcus faecium infection is a strenuous task due to the difficulty of identifying transmission routes and the persistence of this nosocomial pathogen despite the implementation of infection control measures that have been successful with other important nosocomial pathogens. This study provides a comprehensive analysis of over 100 E. faecium isolates collected from 66 cancer patients at the University of Arkansas for Medical Sciences (UAMS) between June 2018 and May 2019. In the top-down approach used in this study, we employed, in addition to the 106 E. faecium UAMS isolates, a filtered set of 2,167 E. faecium strains from the GenBank database to assess the current population structure of E. faecium species and, consequently, to identify the lineages associated with our clinical isolates. We then evaluated the antibiotic resistance and virulence profiles of hospital-associated strains from the species pool, focusing on antibiotics of last resort, to establish an updated classification of high-risk and multidrug-resistant nosocomial clones. Further investigation of the clinical isolates collected from UAMS patients using whole-genome sequencing analytical methodologies (core genome multilocus sequence typing [cgMLST], core single nucleotide polymorphism [coreSNP] analysis, and phylogenomics), with the addition of patient epidemiological data, revealed a polyclonal outbreak of three sequence types occurring simultaneously in different patient wards. The integration of genomic and epidemiological data collected from the patients increased our understanding of the relationships and transmission dynamics of the E. faecium isolates. Our study provides new insights into genomic surveillance of E. faecium to assist in monitoring and further limiting the spread of multidrug-resistant E. faecium. IMPORTANCE Enterococcus faecium is a member of the gastrointestinal microbiota. Although its virulence is low in healthy, immunocompetent individuals, E. faecium has become the third leading cause of health care-associated infections in the United States. This study provides a comprehensive analysis of over 100 E. faecium isolates collected from cancer patients at the University of Arkansas for Medical Sciences (UAMS). We employed a top-down analytical approach (from population genomics to molecular biology) to classify our clinical isolates into their genetic lineages and thoroughly evaluate their antibiotic resistance and virulence profiles. The addition of patient epidemiological data to the whole-genome sequencing analytical methodologies performed in the study allowed us to increase our understanding of the relationships and transmission dynamics of the E. faecium isolates. This study provides new insights into genomic surveillance of E. faecium to help monitor and further limit the spread of multidrug-resistant E. faecium.

Oxazolidinone resistance genes in florfenicol-resistant enterococci from beef cattle and veal calves at slaughter

Background

Linezolid is a critically important oxazolidinone antibiotic used in human medicine. Although linezolid is not licensed for use in food-producing animals, the use of florfenicol in veterinary medicine co-selects for oxazolidinone resistance genes.

Objective

This study aimed to assess the occurrence of cfr, optrA, and poxtA in florfenicol-resistant isolates from beef cattle and veal calves from different herds in Switzerland.

Methods

A total of 618 cecal samples taken from beef cattle and veal calves at slaughter originating from 199 herds were cultured after an enrichment step on a selective medium containing 10 mg/L florfenicol. Isolates were screened by PCR for cfr, optrA, and poxtA which are genes known to confer resistance to oxazolidinones and phenicols. One isolate per PCR-positive species and herd was selected for antimicrobial susceptibility testing (AST) and whole-genome sequencing (WGS).

Results

Overall, 105 florfenicol-resistant isolates were obtained from 99 (16%) of the samples, corresponding to 4% of the beef cattle herds and 24% of the veal calf herds. Screening by PCR revealed the presence of optrA in 95 (90%) and poxtA in 22 (21%) of the isolates. None of the isolates contained cfr. Isolates included for AST and WGS analysis were Enterococcus (E.) faecalis (n = 14), E. faecium (n = 12), E. dispar (n = 1), E. durans (n = 2), E. gallinarum (n = 1), Vagococcus (V.) lutrae (n = 2), Aerococcus (A.) urinaeequi (n = 1), and Companilactobacillus (C.) farciminis (n = 1). Thirteen isolates exhibited phenotypic linezolid resistance. Three novel OptrA variants were identified. Multilocus sequence typing identified four E. faecium ST18 belonging to hospital-associated clade A1. There was a difference in the replicon profile among optrA- and poxtA-harboring plasmids, with rep9 (RepA_N) plasmids dominating in optrA-harboring E. faecalis and rep2 (Inc18) and rep29 (Rep_3) plasmids in poxtA-carrying E. faecium.

Conclusion

Beef cattle and veal calves are reservoirs for enterococci with acquired linezolid resistance genes optrA and poxtA. The presence of E. faecium ST18 highlights the zoonotic potential of some bovine isolates. The dispersal of clinically relevant oxazolidinone resistance genes throughout a wide variety of species including Enterococcus spp., V. lutrae, A. urinaeequi, and the probiotic C. farciminis in food-producing animals is a public health concern.

Hyper-thermophilic anaerobic pretreatment enhances the removal of transferable oxazolidinone and phenicol cross-resistance gene optrA in enterococci

The extensive use of florfenicol in poultry industry results in the emergence of optrA gene, which also confers resistance to clinically important antibiotic linezolid. This study investigated the occurrence, genetic environments, and removal of optrA in enterococci in mesophilic (37 °C) and thermophilic (55 °C) anaerobic digestion systems, and a hyper-thermophilic (70 °C) anaerobic pretreatment system for chicken waste. A total of 331 enterococci were isolated and analyzed for antibiotic resistance against linezolid and florfenicol. The optrA gene was frequently detected in enterococci from chicken waste (42.7%) and effluents from mesophilic (72%) and thermophilic (56.8%) reactors, but rarely detected in the hyper-thermophilic (5.8%) effluent. Whole-genome sequencing revealed that optrA-carrying Enterococcus faecalis sequence type (ST) 368 and ST631 were the dominant clones in chicken waste, and they remained dominant in mesophilic and thermophilic effluents, respectively. The plasmid-borne IS1216E-fexA-optrA-erm(A)-IS1216E was the core genetic element for optrA in ST368, whereas chromosomal Tn554-fexA-optrA was the key one in ST631. IS1216E might play a key role in horizontal transfer of optrA due to its presence in different clones. Hyper-thermophilic pretreatment removed enterococci with plasmid-borne IS1216E-fexA-optrA-erm(A)-IS1216E. A hyper-thermophilic pretreatment is recommended for chicken waste to mitigate dissemination of optrA from animal waste to the environment.

Enterococcus faecium Bacteriophage vB_EfaH_163, a New Member of the Herelleviridae Family, Reduces the Mortality Associated with an E. faecium vanR Clinical Isolate in a Galleria mellonella Animal Model

The rise of antimicrobial resistant (AMR) bacteria is a major health concern, especially with regard to members of the ESKAPE group, to which vancomycin-resistant (VRE) Enterococcus faecium belongs. Phage therapy has emerged as a novel alternative for the treatment of AMR infections. This, however, relies on the isolation and characterisation of a large collection of phages. This work describes the exploration of human faeces as a source of new E. faecium-infecting phages. Phage vB_EfaH_163 was isolated and characterised at the microbiological, genomic, and functional levels. vB_EfaH_163 phage, a new member of Herelleviridae, subfamily Brockvirinae, has a dsDNA genome of 150,836 bp that does not harbour any virulence factors or antibiotic resistance genes. It infects a wide range of E. faecium strains of different origins, including VRE strains. Interestingly, it can also infect Enterococcus faecalis strains, even some that are linezolid-resistant. Its capacity to control the growth of a clinical VRE isolate was shown in broth culture and in a Galleria mellonella animal model. The discovery and characterisation of vB_EfaH_163 increases the number of phages that might be used therapeutically against AMR bacteria.

Antimicrobial Resistance, Virulence Factors, and Genotypes of Enterococcus faecalis and Enterococcus faecium Clinical Isolates in Northern Japan: Identification of optrA in ST480 E. faecalis

Enterococcus faecalis and E. faecium are the major pathogens causing community- and healthcare-associated infections, with an ability to acquire resistance to multiple antimicrobials. The present study was conducted to determine the prevalence of virulence factors, drug resistance and its genetic determinants, and clonal lineages of E. faecalis and E. faecium clinical isolates in northern Japan. A total of 480 (426 E. faecalis and 54 E. faecium) isolates collected over a four-month period were analyzed. Three virulence factors promoting bacterial colonization (asa1, efaA, and ace) were more prevalent among E. faecalis (46-59%) than E. faecium, while a similar prevalence of enterococcal surface protein gene (esp) was found in these species. Between E. faecalis and E. faecium, an evident difference was noted for resistance to erythromycin, gentamicin, and levofloxacin and its responsible resistance determinants. Oxazolidinone resistance gene optrA and phenicol exporter gene fexA were identified in an isolate of E. faecalis belonging to ST480 and revealed to be located on a cluster similar to those of isolates reported in other Asian countries. The E. faecalis isolates analyzed were differentiated into 12 STs, among which ST179 and ST16 of clonal complex (CC) 16 were the major lineage. Nearly all the E. faecium isolates were assigned into CC17, which consisted of 10 different sequence types (STs), including a dominant ST17 containing multidrug resistant isolates and ST78 with isolates harboring the hyaluronidase gene (hyl). The present study revealed the genetic profiles of E. faecalis and E. faecium clinical isolates, with the first identification of optrA in ST480 E. faecalis in Japan.

Emergence of OptrA Gene Mediated Linezolid Resistance among Enterococcus Faecium: A Pilot Study from a Tertiary Care Hospital, India

E. faecium is the third most common cause of nosocomial infections. Linezolid (LNZ) is a reserve antibiotic recommended for infections caused by vancomycin resistant E. faecium (VREfm).  The aim of the present study was to investigate the prevalence of optrA gene among linezolid resistant E. faecium (LREfm) and to study the molecular epidemiology using pulse field gel electrophoresis (PFGE). Clinically significant LREfm were identified and antimicrobial susceptibility was performed by disc diffusion. Minimum inhibitory concentration (MIC) of linezolid, vancomycin, daptomycin and quinupristin/dalfopristin was determined by E-test. PCR and PCR-RFPL were performed for the detection of optrA/cfr gene and G2576T mutation respectively. Molecular epidemiology was studied by PFGE. A total of 1081 clinically significant Enterococci species were isolated which included E. faecium 63.5% (n=687) and E. faecalis 36.5% (n=394). LREfm (30/687) were further studied. Multidrug resistance and vancomycin resistance was 100% and 80%, respectively. Linezolid MIC range was 8-256µg/ml and the most common mechanism of resistance was optrA gene (83.3%) followed by G2576T mutation (33.3%). PFGE analysis demonstrated 4 major clones. The optrA gene mediated linezolid resistance was high and PFGE suggests resistance was emerging in the different background strains irrespective of resistance mechanism. Studies are required to investigate factors driving the emergence of linezolid resistance. The review suggests that this is the first report of optrA-mediated resistance in E. faecium from India.

In vitro activities of licochalcone A against planktonic cells and biofilm of Enterococcus faecalis

This study aims to evaluate the in vitro antibacterial and anti-biofilm activities of licochalcone A on Enterococcus faecalis and to investigate the possible target genes of licochalcone A in E. faecalis. This study found that licochalcone A had antibacterial activities against E. faecalis, with the MIC50 and MIC90 were 25 μM. Licochalcone A (at 4 × MIC) indicated a rapid bactericidal effect on E. faecalis planktonic cells, and killed more E. faecalis planktonic cells (at least 3-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 2, 4, and 6 h of the time-killing test. Licochalcone A (at 10 × MIC) significantly reduced the production of E. faecalis persister cells (at least 2-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 24, 48, 72, and 96 h of the time-killing test. Licochalcone A (at 1/4 × MIC) significantly inhibited the biofilm formation of E. faecalis. The RNA levels of biofilm formation-related genes, agg, esp, and srtA, markedly decreased when the E. faecalis isolates were treated with licochalcone A at 1/4 × MIC for 6 h. To explore the possible target genes of licochalcone A in E. faecalis, the licochalcone A non-sensitive E. faecalis clones were selected in vitro by induction of wildtype strains for about 140 days under the pressure of licochalcone A, and mutations in the possible target genes were detected by whole-genome sequencing. This study found that there were 11 nucleotide mutations leading to nonsynonymous mutations of 8 amino acids, and among these amino acid mutations, there were 3 mutations located in transcriptional regulator genes (MarR family transcriptional regulator, TetR family transcriptional regulator, and MerR family transcriptional regulator). In conclusion, this study found that licochalcone A had an antibacterial effect on E. faecalis, and significantly inhibited the biofilm formation of E. faecalis at subinhibitory concentrations.

Emergence and Genomic Characterization of the First Reported optrA-Carrying Linezolid-Resistant Enterococci Isolated from Retail Broiler Meat in the United Arab Emirates

The foodborne transfer of resistant genes from enterococci to humans and their tolerance to several commonly used antimicrobials are of growing concern worldwide. Linezolid is a last-line drug for managing complicated illnesses resulting from multidrug-resistant Gram-positive bacteria. The optrA gene has been reported in enterococci as one of the acquired linezolid resistance mechanisms. The present study uses whole-genome sequencing analysis to characterize the first reported isolates of linezolid-resistant E. faecium (n = 6) and E. faecalis (n = 10) harboring the optrA gene isolated from samples of supermarket broiler meat (n = 165) in the United Arab Emirates (UAE). The sequenced genomes were used to appraise the study isolates’ genetic relatedness, antimicrobial resistance determinants, and virulence traits. All 16 isolates carrying the optrA gene demonstrated multidrug-resistance profiles. Genome-based relatedness classified the isolates into five clusters that were independent of the isolate sources. The most frequently known genotype among the isolates was the sequence type ST476 among E. faecalis (50% (5/10)). The study isolates revealed five novel sequence types. Antimicrobial resistance genes (ranging from 5 to 13) were found among all isolates that conferred resistance against 6 to 11 different classes of antimicrobials. Sixteen different virulence genes were found distributed across the optrA-carrying E. faecalis isolates. The virulence genes in E. faecalis included genes encoding invasion, cell adhesion, sex pheromones, aggregation, toxins production, the formation of biofilms, immunity, antiphagocytic activity, proteases, and the production of cytolysin. This study presented the first description and in-depth genomic characterization of the optrA-gene-carrying linezolid-resistant enterococci from retail broiler meat in the UAE and the Middle East. Our results call for further monitoring of the emergence of linezolid resistance at the retail and farm levels. These findings elaborate on the importance of adopting a One Health surveillance approach involving enterococci as a prospective bacterial indicator for antimicrobial resistance spread at the human–food interface.

Oxazolidinones: mechanisms of resistance and mobile genetic elements involved

The oxazolidinones (linezolid and tedizolid) are last-resort antimicrobial agents used for the treatment of severe infections in humans caused by MDR Gram-positive bacteria. They bind to the peptidyl transferase centre of the bacterial ribosome inhibiting protein synthesis. Even if the majority of Gram-positive bacteria remain susceptible to oxazolidinones, resistant isolates have been reported worldwide. Apart from mutations, affecting mostly the 23S rDNA genes and selected ribosomal proteins, acquisition of resistance genes (cfr and cfr-like, optrA and poxtA), often associated with mobile genetic elements [such as non-conjugative and conjugative plasmids, transposons, integrative and conjugative elements (ICEs), prophages and translocatable units], plays a critical role in oxazolidinone resistance. In this review, we briefly summarize the current knowledge on oxazolidinone resistance mechanisms and provide an overview on the diversity of the mobile genetic elements carrying oxazolidinone resistance genes in Gram-positive and Gram-negative bacteria.

Antimicrobial Susceptibility of Enterococcus Isolates from Cattle and Pigs in Portugal: Linezolid Resistance Genes optrA and poxtA

Enterococci are part of the commensal gut microbiota of mammals, with Enterococcus faecalis and Enterococcus faecium being the most clinically relevant species. This study assesses the prevalence and diversity of enterococcal species in cattle (n = 201) and pig (n = 249) cecal samples collected in 2017. Antimicrobial susceptibility profiles of E. faecium (n = 48) and E. faecalis (n = 84) were assessed by agar and microdilution methods. Resistance genes were screened through PCR and nine strains were analyzed by Whole Genome Sequencing. A wide range of enterococci species was found colonizing the intestines of pigs and cattle. Overall, the prevalence of resistance to critically important antibiotics was low (except for erythromycin), and no glycopeptide-resistant isolates were identified. Two daptomycin-resistant E. faecalis ST58 and ST93 were found. Linezolid-resistant strains of E. faecalis (n = 3) and E. faecium (n = 1) were detected. Moreover, oxazolidinone resistance determinants optrA (n = 8) and poxtA (n = 2) were found in E. faecalis (ST16, ST58, ST207, ST474, ST1178) and E. faecium (ST22, ST2138). Multiple variants of optrA were found in different genetic contexts, either in the chromosome or plasmids. We highlight the importance of animals as reservoirs of resistance genes to critically important antibiotics.

Fattening Pigs Are a Reservoir of Florfenicol-Resistant Enterococci Harboring Oxazolidinone Resistance Genes

ABSTRACT

The use of florfenicol in farm animals may select enterococci that carry resistance genes that confer resistance to linezolid, a critically important oxazolidinone antibiotic used in human medicine. This cross-sectional study aimed to assess the occurrence of oxazolidinone resistance genes in florfenicol-resistant enterococci from fattening pigs in Switzerland and to characterize a subset of the isolates using whole genome sequencing. A total of 31 florfenicol-resistant enterococcal isolates were obtained from 27 (5%) of 565 cecal samples of fattening pigs from seven (11%) of 62 farms. Screening by PCR revealed the presence of cfr-poxtA in 1 of 31, optrA in 15 of 31, and poxtA in 15 of 31 enterococcal isolates. One randomly selected isolate per PCR-positive Enterococcus species and positive farm was selected for further analysis (n = 10). In nine of the 10 isolates, the presence of oxazolidinone resistance genes did not result in phenotypic resistance. Whole genome sequencing analysis showed the presence of E. faecalis (n = 1), E. faecium (n = 1), and E. hirae (n = 1), harboring optrA18, optrA7, and a new optrA allele, respectively. E. durans (n = 1), E. faecium (n = 4), and E. hirae (n = 1) carried the wild-type poxtA, and E. faecalis (n = 1) coharbored cfr(D) and poxtA2. Except for optrA7, all oxazolidinone resistance genes were found on plasmids. Multilocus sequence typing analysis identified E. faecalis ST19 and ST376, E. faecium ST80 belonging to hospital-adapted clade A1, and E. faecium ST21, ST55, ST269, and ST416 belonging to clade A2, which represents human commensals and animal strains. The occurrence of cfr(D), optrA, and poxtA in various porcine Enterococcus spp. demonstrates the spread of oxazolidinone resistance genes among enterococci from fattening pigs in Switzerland. The presence in one sample of poxtA-carrying E. faecium ST80 emphasizes the potential risk to human health through dissemination of strains carrying oxazolidinone resistance genes into the food chain.

HIGHLIGHTS

Evaluation of CHROMagar™ LIN-R for the Screening of Linezolid Resistant Staphylococci from Positive Blood Cultures and Nasal Swab Screening Samples

The increasing number of nosocomial pathogens with resistances towards last resort antibiotics, like linezolid for gram positive bacteria, leads to a pressing need for screening and, consequently, suitable screening media. Some national guidelines on infection prevention (e.g., in Germany) have already recommended screening for linezolid-resistant bacteria, despite an accurate screening medium that was not available yet. In this study, we analyzed the performance and reliability of the first commercial chromogenic medium, CHOMagar™ LIN-R, for screening of linezolid-resistant gram-positive isolates. Thirty-four pure bacterial cultures, 18 positive blood cultures, and 358 nasal swab screening samples were tested. This medium efficiently detected linezolid-resistant S. epidermidis isolates from pure bacterial cultures and from positive blood cultures with a high sensitivity (100%) and specificity (100%). Among the 358 nasal swab screening samples prospectively tested, 10.9% were cultured with linezolid-resistant isolates (mostly S. epidermidis). Of note, slight growth was observed for 7.5% samples with linezolid-susceptible isolates of S. epidermidis (n = 1), S. aureus (n = 1), Enterococcus faecalis (n = 4), Lactobacillus spp. (n = 3), gram negatives (n = 18). Moreover, few Candida spp. also cultured on this medium (1.4%).

Sentinel Surveillance Reveals Emerging Daptomycin-Resistant ST736 Enterococcus faecium and Multiple Mechanisms of Linezolid Resistance in Enterococci in the United States

Enterococcus faecalis and faecium with resistance to daptomycin and/or linezolid are emerging globally. We present the genomic characterization of daptomycin- and linezolid-resistant E. faecalis and E. faecium surveillance isolates from the United States, 2013–2016. Daptomycin resistance was low among E. faecalis (2/364, 0.5%) and E. faecium (17/344, 5%). The majority (71%, 12/17) of daptomycin-resistant E. faecium isolates belonged to the emerging ST736 clone and contained mutations in liaFSR and cls previously associated with resistance. However, 1/2 E. faecalis and 3/17 E. faecium did not contain these mutations previously associated with daptomycin resistance. Linezolid resistance was rare among E. faecalis (1/364, 0.3%) and E. faecium (2/344, 0.6%). These two E. faecium isolates, one of which was also resistant to daptomycin and vancomycin, contained the 23S rRNA nucleotide mutation (G2576T) associated with linezolid resistance. Long-read sequencing revealed the linezolid-resistant E. faecalis isolate contained chromosomal- and plasmid-encoded copies of optrA. The chromosomal optrA was located on the recently described Tn6674 multiresistance transposon. The second copy of optrA was encoded on an ∼65 kb mosaic plasmid, with component regions sharing high sequence identity to optrA-encoding multiresistance plasmids of animal origin. The optrA-encoding plasmid contained open reading frames predicted to encode proteins associated with a pheromone-responsive plasmid transfer system, and filter mating experiments confirmed the plasmid was conjugative. Continued surveillance of enterococci is necessary to assess the prevalence and trends of daptomycin and linezolid resistance in the United States, characterize resistance mechanisms and how they transfer, and monitor for emerging sequence types associated with resistance.

Presence of optrA-mediated linezolid resistance in multiple lineages and plasmids of Enterococcus faecalis revealed by long read sequencing

Transferable linezolid resistance due to optrA, poxtA, cfr and cfr-like genes is increasingly detected in enterococci associated with animals and humans globally. We aimed to characterize the genetic environment of optrA in linezolid-resistant Enterococcus faecalis isolates from Scotland. Six linezolid-resistant E. faecalis isolated from urogenital samples were confirmed to carry the optrA gene by PCR. Short read (Illumina) sequencing showed the isolates were genetically distinct (>13900 core SNPs) and belonged to different MLST sequence types. Plasmid contents were examined using hybrid assembly of short and long read (Oxford Nanopore MinION) sequencing technologies. The optrA gene was located on distinct plasmids in each isolate, suggesting that transfer of a single plasmid did not contribute to optrA dissemination in this collection. pTM6294-2, BX5936-1 and pWE0438-1 were similar to optrA-positive plasmids from China and Japan, while the remaining three plasmids had limited similarity to other published examples. We identified the novel Tn6993 transposon in pWE0254-1 carrying linezolid (optrA), macrolide (ermB) and spectinomycin [ANT(9)-Ia] resistance genes. OptrA amino acid sequences differed by 0–20 residues. We report multiple variants of optrA on distinct plasmids in diverse strains of E. faecalis. It is important to identify the selection pressures driving the emergence and maintenance of resistance against linezolid to retain the clinical utility of this antibiotic.

Genomic analysis of 600 vancomycin-resistant Enterococcus faecium reveals a high prevalence of ST80 and spread of similar vanA regions via IS1216E and plasmid transfer in diverse genetic lineages in Ireland

BACKGROUND

Vancomycin-resistant Enterococcus faecium (VREfm) cause a wide range of hospital infections. Ireland has had one of the highest invasive VREfm infection rates in Europe over the last decade, yet little is known about Irish VREfm.

OBJECTIVES

To investigate the population structure of Irish VREfm, explore diversity by analysing the vanA transposon region and compare Irish, Danish and global isolates.

METHODS

E. faecium (n = 648) from five Irish hospitals were investigated, including VREfm [547 rectal screening and 53 bloodstream infection (BSI)] isolates and 48 vancomycin-susceptible (VSEfm) BSI isolates recovered between June 2017 and December 2019. WGS and core-genome MLST (cgMLST) were used to assess population structure. Genetic environments surrounding vanA were resolved by hybrid assembly of short-read (Illumina) and long-read (Oxford Nanopore Technologies) sequences.

RESULTS

All isolates belonged to hospital-adapted clade A1 and the majority (435/648) belonged to MLST ST80. The population structure was highly polyclonal; cgMLST segregated 603/648 isolates into 51 clusters containing mixtures of screening and BSI isolates, isolates from different hospitals, and VREfm and VSEfm. Isolates within clusters were closely related (mean average ≤16 allelic differences). The majority (96.5%) of VREfm harboured highly similar vanA regions located on circular or linear plasmids with multiple IS1216E insertions, variable organization of vanA operon genes and 78.6% harboured a truncated tnpA transposase. Comparison of 648 Irish isolates with 846 global E. faecium from 30 countries using cgMLST revealed little overlap.

CONCLUSIONS

Irish VREfm are polyclonal, yet harbour a characteristic plasmid-located vanA region with multiple IS1216E insertions that may facilitate spread.

Plasmid Fusion and Recombination Events That Occurred during Conjugation of poxtA-Carrying Plasmids in Enterococci

Linezolid plays a crucial role in the treatment of infections caused by multiresistant Gram-positive bacteria. The poxtA gene not only confers oxazolidinone and phenicol resistance but also decreases susceptibility to tetracycline. In this study, we investigated structural changes in mobilizable poxtA-carrying plasmids in enterococci which occurred during conjugation experiments using S1-PFGE (pulsed-field gel electrophoresis), Southern blot hybridization, and whole-genome sequencing (WGS) analysis. Two poxtA-carrying strains were identified in Enterococcus faecalis E006 and Enterococcus lactis E843, respectively. E. faecalis E006 contains the 121,520-bp conjugative plasmid pE006-121 and the 19,832-bp mobilizable poxtA-carrying plasmid pE006-19, while E. lactis E843 contains the 171,930-bp conjugative plasmid pE843-171 and the 27,847-bp mobilizable poxtA-carrying plasmid pE843-27. Moreover, both poxtA-carrying plasmids were mobilized by their respective conjugative plasmid in enterococci by plasmid fusion; one was generated by homologous recombination in E. faecalis through an identical 864-bp homologous region in the plasmids of the parental strain, while another was generated by an IS1216E-mediated plasmid integration in E. lactis, involving a replicative transposition.

IMPORTANCE Until now, all the poxtA genes described in enterococci, including E. faecalis, E. faecium, and E. hirae, are plasmid-borne, suggesting that plasmids play an important role in the dissemination of the poxtA gene among enterococci. This study showed that the mobilizable poxtA-carrying plasmid could transfer with the help of conjugative plasmid in enterococci via plasmid fusion, with one generated by homologous recombination in E. faecalis, and another by replicative transposition in E. lactis. During both the fusion events, the poxtA-carrying plasmids changed from nonconjugative to conjugative, leading to the generation and enhanced dissemination of the larger phenicol-oxazolidinone-tetracycline resistance-encoding plasmids in enterococci.

Emergence of optrA-Mediated Linezolid Resistance in Enterococcus faecium: A Molecular Investigation in a Tertiary Hospital of Southwest China from 2014-2018

Purpose

To investigate the potential mechanism and molecular characteristics of linezolid-non-sensitive Enterococcus faecium from a tertiary hospital in southwest China and characterize the relevant plasmids.

Patients and Methods

Linezolid-non-sensitive Enterococcus faecium (LNSEFM) isolates collected from January 2014 to December 2018 were screened for resistant genes 23s rRNA, rplC, rplD, rplV, optrA, cfr, poxtA, by PCR. Molecular epidemiological analysis was performed by multilocus sequence typing (MLST). The optrA-and-poxtA co-harboring strain EFM_7150 was subjected to the whole genome sequencing (WGS) by Illumina HiSeq and Oxford Nanopore MinION.

Results

A total of 15 LNSEFM with linezolid MICs ranging from 4 to 16 mg/L were identified. About 66.7% (10/15) of isolates were linezolid-resistant. About 46.7% (7/15) of strains were positive for optrA. Two types of optrA variants (P and EYDNDM) were identified. About 13.3% (2/15) of isolates had poxtA. 1 harbored a L22 protein alteration (Ser77Thr). One isolate coharbored optrA (EYDNDM variant) and poxtA. There was no mutation in the gene that encoded the ribosomal protein L3/L4 or the domain V of 23S rRNA. No cfr gene was detected. Based on WGS data, optrA was associated with Tn558 inserted to radC gene and poxtA was flanked by IS1216E.

Conclusion

OptrA is primary mechanism in linezolid-resistant Enterococcus faecium. This is the first report ofoptrA variants P and EYDNDM identified in Enterococcus faecium and optrA-and-poxtA co-harboring Enterococcus faecium clinically in southwest China. Besides, Tn558 and IS1216Es may play an important role in the dissemination of optrA and poxtA, respectively. The findings revealed the potential threat to nosocomial infection by optrA and coexistence of optrA and poxtA in Enterococcus faecium. Thus, clinical surveillance of linezolid-resistant Enterococcus is urgently needed.

Synthesis and biological evaluation of indole-based peptidomimetics as antibacterial agents against Gram-positive bacteria

The emergence of bacterial multidrug resistance and the lack of new antimicrobial agents urgently demand the discovery and development of novel antibacterials that avoid bacterial resistance. Antimicrobial peptidomimetics represent a promising approach for overcoming antibiotic resistance. Herein we report the synthesis and evaluation of indole-based amphiphilic antimicrobial peptidomimetics, bearing hydrophobic side chains and hydrophilic cationic moieties. Among these derivatives, compound 28 demonstrated potent antimicrobial activity against Gram-positive bacteria, low hemolytic activity and low toxicity towards mammalian cells, as well as good stability in salt conditions. Moreover, compound 28 showed the rapid killing of bacteria via membrane-targeting action without developing bacterial resistance. More importantly, compound 28 displayed high antimicrobial potency against Gram-positive bacteria in a murine model of bacterial keratitis, and was found to be more efficient than vancomycin. Thus, compound 28 had great potential as a promising lead compound for the treatment of Gram-positive bacterial infection.

Prediction of antimicrobial resistance in clinical Enterococcus faecium isolates using a rules-based analysis of whole genome sequences

Background: Enterococcus faecium is a major cause of clinical infections, often due to multidrug-resistant (MDR) strains. Whole genome sequencing (WGS) is a powerful tool to study MDR bacteria and their antimicrobial resistance (AMR) mechanisms. Here we use WGS to characterize E. faecium clinical isolates and test the feasibility of rules-based genotypic prediction of AMR. Methods: Clinical isolates were divided into derivation and validation sets. Phenotypic susceptibility testing for ampicillin, vancomycin, high-level gentamicin, ciprofloxacin, levofloxacin, doxycycline, tetracycline, and linezolid was performed using the VITEK 2 automated system, with confirmation and discrepancy resolution by broth microdilution, disk diffusion, or gradient diffusion when needed. WGS was performed to identify isolate lineage and AMR genotype. AMR prediction rules were derived by analyzing the genotypic-phenotypic relationship in the derivation set. Results: Phylogenetic analysis demonstrated that 88% of isolates in the collection belonged to hospital-associated clonal complex 17. Additionally, 12% of isolates had novel sequence types. When applied to the validation set, the derived prediction rules demonstrated an overall positive predictive value of 98% and negative predictive value of 99% compared to standard phenotypic methods. Most errors were falsely resistant predictions for tetracycline and doxycycline. Further analysis of genotypic-phenotypic discrepancies revealed potentially novel pbp5 and tet(M) alleles that provide insight into ampicillin and tetracycline class resistance mechanisms. The prediction rules demonstrated generalizability when tested on an external dataset. Conclusions: Known AMR genes and mutations can predict E. faecium phenotypic susceptibility with high accuracy for most routinely tested antibiotics, providing opportunities for advancing molecular diagnostics.

Large diversity of linezolid-resistant isolates discovered in food-producing animals through linezolid selective monitoring in Belgium in 2019

Background

Linezolid is a critically important antibiotic used to treat human infections caused by MRSA and VRE. While linezolid is not licensed for food-producing animals, linezolid-resistant (LR) isolates have been reported in European countries, including Belgium.

Objectives

To: (i) assess LR occurrence in staphylococci and enterococci isolated from different Belgian food-producing animals in 2019 through selective monitoring; and (ii) investigate the genomes and relatedness of these isolates.

Methods

Faecal samples (n = 1325) and nasal swab samples (n = 148) were analysed with a protocol designed to select LR bacteria, including a 44–48 h incubation period. The presence of LR chromosomal mutations, transferable LR genes and their genetic organizations and other resistance genes, as well as LR isolate relatedness (from this study and the NCBI database) were assessed through WGS.

Results

The LR rate differed widely between animal host species, with the highest rates occurring in nasal samples from pigs and sows (25.7% and 20.5%, respectively) and faecal samples from veal calves (16.4%). WGS results showed that LR determinants are present in a large diversity of isolates circulating in the agricultural sector, with some isolates closely related to human isolates, posing a human health risk.

Conclusions

LR dedicated monitoring with WGS analysis could help to better understand the spread of LR. Cross-selection of LR transferable genes through other antibiotic use should be considered in future action plans aimed at combatting antimicrobial resistance and in future objectives for the rational use of antibiotics in a One Health perspective.

Prevalence and Characteristics of Phenicol-Oxazolidinone Resistance Genes in Enterococcus Faecalis and Enterococcus Faecium Isolated from Food-Producing Animals and Meat in Korea

The use of phenicol antibiotics in animals has increased. In recent years, it has been reported that the transferable gene mediates phenicol-oxazolidinone resistance. This study analyzed the prevalence and characteristics of phenicol-oxazolidinone resistance genes in Enterococcus faecalis and Enterococcus faecium isolated from food-producing animals and meat in Korea in 2018. Furthermore, for the first time, we reported the genome sequence of E. faecalis strain, which possesses the phenicol-oxazolidinone resistance gene on both the chromosome and plasmid. Among the 327 isolates, optrA, poxtA, and fexA genes were found in 15 (4.6%), 8 (2.5%), and 17 isolates (5.2%), respectively. Twenty E. faecalis strains carrying resistance genes belonged to eight sequence types (STs), and transferability was found in 17 isolates. The genome sequences revealed that resistant genes were present in the chromosome or plasmid, or both. In strains EFS17 and EFS108, optrA was located downstream of the ermA and ant(9)-1 genes. The strains EFS36 and EFS108 harboring poxtA-encoding plasmid cocarried fexA and cfr(D). These islands also contained IS1216E or the transposon Tn554, enabling the horizontal transfer of the phenicol-oxazolidinone resistance with other antimicrobial-resistant genes. Our results suggest that it is necessary to promote the prudent use of antibiotics through continuous monitoring and reevaluation.

Prevalence of linezolid-resistant organisms among patients admitted to a tertiary hospital for critical care or dialysis

BACKGROUND

Linezolid is an oxazolidinone antimicrobial regarded as a "last resort" antimicrobial, used typically for treatment of Gram-positive bacterial infections. It is acknowledged that prevalence of resistance to linezolid is increasing in Europe. In Ireland, a number of outbreaks of linezolid-resistant isolates have been reported, including an outbreak at the location for this study, the Intensive Care Unit (ICU) of University Hospital Limerick (UHL).

METHODS

The Chromagar™ Lin-R selective medium was validated using a panel of linezolid-sensitive and linezolid-resistant strains. Subsequently, the prevalence exercise focused on a convenience sample of patients (n = 159) in critical care wards, ICU (n = 23) and High-Dependency Unit (HDU, n = 51), in addition to patients undergoing dialysis therapy (n = 77). Eight additional patients had specimens collected when attending more than one location. Growth on Chromagar™ Lin-R agar was followed by drug sensitivity testing by disc diffusion and minimum inhibitory concentration (MIC) testing.

RESULTS

A validation exercise was performed on 23 isolates: seven target and sixteen non-target organisms. Isolates performed as intended (100% sensitivity, 100% specificity). For the prevalence study, of 398 tests, 40 resulted in growth of non-target organisms (specificity approx. 90%). A sole patient (1/159) was identified as colonized by a linezolid-resistant Staphylococcus epidermidis, a prevalence of 0.63%. Molecular investigation confirmed presence of the G2576T mutation in the 23S rRNA.

CONCLUSION

While this point prevalence study identified extremely low carriage of linezolid-resistant bacteria, it remains prudent to maintain vigilance as reports of outbreaks associated with linezolid-resistant S. epidermidis (LRSE) in European critical care units are increasing.

Genetic features of the poxtA linezolid resistance gene in human enterococci from France

OBJECTIVES

To describe the prevalence of poxtA among clinical linezolid-resistant enterococci (LRE) collected in France from 2016 to 2020 and to extensively characterize its genetic supports and environments.

METHODS

All LRE clinical isolates received at the National Reference Centre for Enterococci from French hospitals between 2016 and 2020 were included. LRE isolates were screened for linezolid resistance genes (cfr-like, optrA and poxtA) by real-time PCR and phenotypically characterized. A collection of 11 representative poxtA-positive isolates (10 Enterococcus faecium and 1 Enterococcus faecalis) underwent WGS by hybrid assembly combining short-read (Illumina MiSeq) and long-read (MinION) approaches. Transferability of poxtA was attempted by filter-mating experiments.

RESULTS

Out of 466 LRE received at the National Reference Centre for Enterococci over the period, 47 (10.1%) were poxtA-positive, including 42 E. faecium. The 11 isolates characterized by WGS were confirmed to be epidemiologically unrelated by core genome analysis and eight different STs were assigned to E. faecium isolates. The poxtA gene was found to be plasmid carried and flanked by IS1216E transposase genes in all isolates and frequently linked with fexB, tet(M) and tet(L). A total of seven distinct poxtA-harbouring plasmids were obtained after hybrid assembly and plasmid transfer of poxtA was successful in three cases. For the two poxtA/optrA-positive isolates, those genes were carried by different plasmids.

CONCLUSIONS

The poxtA gene has been circulating among clinical enterococci in France since at least 2016, mostly in E. faecium and independently from optrA. The poxtA-carrying plasmids often co-carried resistance genes to phenicols and tetracyclines, and could have been co-selected through their veterinary use.

Mobile Oxazolidinone Resistance Genes in Gram-Positive and Gram-Negative Bacteria

Seven mobile oxazolidinone resistance genes, including cfr, cfr(B), cfr(C), cfr(D), cfr(E), optrA, and poxtA, have been identified to date. The cfr genes code for 23S rRNA methylases, which confer a multiresistance phenotype that includes resistance to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A compounds. The optrA and poxtA genes code for ABC-F proteins that protect the bacterial ribosomes from the inhibitory effects of oxazolidinones. The optrA gene confers resistance to oxazolidinones and phenicols, while the poxtA gene confers elevated MICs or resistance to oxazolidinones, phenicols, and tetracycline. These oxazolidinone resistance genes are most frequently found on plasmids, but they are also located on transposons, integrative and conjugative elements (ICEs), genomic islands, and prophages. In these mobile genetic elements (MGEs), insertion sequences (IS) most often flanked the cfr, optrA, and poxtA genes and were able to generate translocatable units (TUs) that comprise the oxazolidinone resistance genes and occasionally also other genes. MGEs and TUs play an important role in the dissemination of oxazolidinone resistance genes across strain, species, and genus boundaries. Most frequently, these MGEs also harbor genes that mediate resistance not only to antimicrobial agents of other classes, but also to metals and biocides. Direct selection pressure by the use of antimicrobial agents to which the oxazolidinone resistance genes confer resistance, but also indirect selection pressure by the use of antimicrobial agents, metals, or biocides (the respective resistance genes against which are colocated on cfr-, optrA-, or poxtA-carrying MGEs) may play a role in the coselection and persistence of oxazolidinone resistance genes.

Low Proportion of Linezolid and Daptomycin Resistance Among Bloodborne Vancomycin-Resistant Enterococcus faecium and Methicillin-Resistant Staphylococcus aureus Infections in Europe

Vancomycin-resistant Enterococcus faecium (VREF) and methicillin-resistant Staphylococcus aureus (MRSA) are associated with significant health burden. We investigated linezolid and daptomycin resistance among VREF and MRSA in the EU/EEA between 2014 and 2018. Descriptive statistics and multivariable logistic regression were used to analyze 6,949 VREF and 35,131 MRSA blood isolates from patients with bloodstream infection. The population-weighted mean proportion of linezolid resistance in VREF and MRSA between 2014 and 2018 was 1.6% (95% CI 1.33–2.03%) and 0.28% (95% CI 0.32–0.38%), respectively. Daptomycin resistance in MRSA isolates was similarly low [1.1% (95% CI 0.75–1.6%)]. On the European level, there was no temporal change of daptomycin and linezolid resistance in MRSA and VREF. Multivariable regression analyses showed that there was a higher likelihood of linezolid and daptomycin resistance in MRSA (aOR: 2.74, p < 0.001; aOR: 2.25, p < 0.001) and linezolid in VREF (aOR: 1.99, p < 0.001) compared to their sensitive isolates. The low proportion of linezolid and daptomycin resistance in VREF and MRSA suggests that these last-resort antibiotics remain effective and will continue to play an important role in the clinical management of these infections in Europe. However, regional and national efforts to contain antimicrobial resistance should continue to monitor the trend through strengthened surveillance that includes genomic surveillance for early warning and action.

Occurrence of multidrug-resistant Enterococcus faecium isolated from environmental samples

Enterococcus species are present in the microbiota of humans and animals and have also been described in the environment. Among the species, Enterococcus faecium is one of the main pathogens associated with nosocomial infections worldwide. Enterococcus faecium isolates resistant to different classes of antimicrobials have been increasingly reported, including multidrug-resistant (MDR) isolates in environmental sources, which is worrying. Therefore, this study aimed to characterize E. faecium isolates obtained from soil and water samples regarding antimicrobial resistance and virulence determinants. A total 40 E. faecium isolates were recovered from 171 environmental samples. All isolates were classified as MDR, highlighting the resistance to the fluoroquinolones class, linezolid and vancomycin. Furthermore, high-level aminoglycoside resistance and high-level ciprofloxacin resistance were detected in some isolates. Several clinically relevant antimicrobial resistance genes were found, including vanC1, ermB, ermC, mefAE, tetM, tetL, ant(6')-Ia, ant(4')-Ia, aph(3')-IIIa and aac(6')-Ie-aph(2″)-Ia. Three virulence genes were detected among the MDR E. faecium isolates, such as esp, gelE and ace. The results of this study contribute to a better understanding of MDR E. faecium isolates carrying antimicrobial resistance and virulence genes in environmental sources and report for the first time in the world the presence of vanC1-producing E. faecium isolated from soil.

Identification of the Multiresistance Gene poxtA in Oxazolidinone-Susceptible Staphylococcus haemolyticus and Staphylococcus saprophyticus of Pig and Feed Origins

Previous studies on the prevalence and transmission mechanism of oxazolidinone resistance gene poxtA in CoNS are lacking, which this study addresses. By screening 763 CoNS isolates from different sources of several livestock farms in Guangdong, China, 2018–2020, we identified that the poxtA was present in seven CoNS isolates of pig and feed origins. Species identification and multilocus sequence typing (MLST) confirmed that seven poxtA-positive CoNS isolates were composed of five ST64-Staphylococcus haemolyticus and two Staphylococcus saprophyticus isolates. All poxtA-positive Staphylococcus haemolyticus isolates shared similar pulsed-field gel electrophoresis (PFGE) patterns. Transformation assays demonstrated all poxtA-positive isolates were able to transfer poxtA gene to Staphylococcus aureus RN4220. S1-PFGE and whole-genome sequencing (WGS) revealed the presence of poxtA-carrying plasmids in size around 54.7 kb. The plasmid pY80 was 55,758 bp in size and harbored the heavy metal resistance gene czcD and antimicrobial resistance genes, poxtA, aadD, fexB and tet(L). The regions (IS1216E-poxtA-IS1216E) in plasmid pY80 were identified in Staphylococcus spp. and Enterococcus spp. with different genetic and source backgrounds. In conclusion, this was the first report about the poxtA gene in Staphylococcus haemolyticus and Staphylococcus saprophyticus, and IS1216 may play an important role in the dissemination of poxtA among different Gram-positive bacteria.

Linezolid Resistance Genes in Enterococci Isolated from Sediment and Zooplankton in Two Italian Coastal Areas

Linezolid is a last-resort antibiotic for the treatment of severe infections caused by multidrug-resistant Gram-positive organisms; although linezolid resistance remains uncommon, the number of linezolid-resistant enterococci has increased in recent years due to worldwide spread of acquired resistance genes (cfr, optrA, and poxtA) in clinical, animal, and environmental settings. In this study, we investigated the occurrence of linezolid-resistant enterococci in marine samples from two coastal areas in Italy. Isolates grown on florfenicol-supplemented Slanetz-Bartley agar plates were investigated for their carriage of optrA, poxtA, and cfr genes; optrA was found in one Enterococcus faecalis isolate, poxtA was found in three Enterococcus faecium isolates and two Enterococcus hirae isolates, and cfr was not found. Two of the three poxtA-carrying E. faecium isolates and the two E. hirae isolates showed related pulsed-field gel electrophoresis (PFGE) profiles. Two E. faecium isolates belonged to the new sequence type 1710, which clustered in clonal complex 94, encompassing nosocomial strains. S1 PFGE/hybridization assays showed a double (chromosome and plasmid) location of poxtA and a plasmid location of optrA Whole-genome sequencing revealed that poxtA was contained in a Tn6657-like element carried by two plasmids (pEfm-EF3 and pEh-GE2) of similar size, found in different species, and that poxtA was flanked by two copies of IS1216 in both plasmids. In mating experiments, all but one strain (E. faecalis EN3) were able to transfer the poxtA gene to E. faecium 64/3. The occurrence of linezolid resistance genes in enterococci from marine samples is of great concern and highlights the need to improve practices aimed at limiting the transmission of linezolid-resistant strains to humans from environmental reservoirs.IMPORTANCE Linezolid is one of the few antimicrobials available to treat severe infections due to drug-resistant Gram-positive bacteria; therefore, the emergence of linezolid-resistant enterococci carrying transferable resistance determinants is of great concern for public health. Linezolid resistance genes (cfr, optrA, and poxtA), often plasmid located, can be transmitted via horizontal gene transfer and have the potential to spread globally. This study highlights the detection of enterococci carrying linezolid resistance genes from sediment and zooplankton samples from two coastal urban areas in Italy. The presence of clinically relevant resistant bacteria, such as linezolid-resistant enterococci, in marine environments could reflect their spillover from human and/or animal reservoirs and could indicate that coastal seawaters also might represent a source of these resistance genes.

Genomic Insights Into Last-Line Antimicrobial Resistance in Multidrug-Resistant Staphylococcus and Vancomycin-Resistant Enterococcus

Multidrug-resistant Staphylococcus and vancomycin-resistant Enterococcus (VRE) are important human pathogens that are resistant to most clinical antibiotics. Treatment options are limited and often require the use of 'last-line' antimicrobials such as linezolid, daptomycin, and in the case of Staphylococcus, also vancomycin. The emergence of resistance to these last-line antimicrobial agents is therefore of considerable clinical concern. This mini-review provides an overview of resistance to last-line antimicrobial agents in Staphylococcus and VRE, with a particular focus on how genomics has provided critical insights into the emergence of resistant clones, the molecular mechanisms of resistance, and the importance of mobile genetic elements in the global spread of resistance to linezolid.

Spread of Linezolid-Resistant Enterococcus spp. in Human Clinical Isolates in the Czech Republic

The aim of this study was to map and investigate linezolid resistance mechanisms in linezolid-resistant enterococci in the Czech Republic from 2009 to 2019. Altogether, 1442 isolates of Enterococcus faecium and Enterococcus faecalis were examined in the National Reference Laboratory for Antibiotics. Among them, 8% of isolates (n = 115) were resistant to linezolid (E. faecium/n = 106, E. faecalis/n = 9). Only three strains of E. faecium were resistant to tigecycline, 72.6% of isolates were resistant to vancomycin. One isolate of E. faecium harbored the cfr gene. The majority (87%, n = 11) of E. faecium strains were resistant to linezolid because of the mutation G2576T in the domain V of the 23S rRNA. This mutation was detected also in two strains of E. faecalis. The presence of the optrA gene was the dominant mechanism of linezolid resistance in E. faecalis isolates. None of enterococci contained cfrB, poxtA genes, or any amino acid mutation in genes encoding ribosomal proteins. No mechanism of resistance was identified in 4 out of 106 E. faecium linezolid resistant isolates in this study. Seventeen sequence types (STs) including four novel STs were identified in this work. Clonal complex CC17 was found in all E. faecium isolates.

Linezolid Resistance in Enterococcus faecalis Associated With Urinary Tract Infections of Patients in a Tertiary Hospitals in China: Resistance Mechanisms, Virulence, and Risk Factors

Background:Enterococcus faecalis has been commonly considered as one of the major pathogens of the urinary tract infection (UTI) in human host worldwide, whereas the molecular characteristics of E. faecalis clinical isolates from the patients with UTI in China remains seldomly reported. This study aimed to investigate the resistance mechanism, molecular characteristics and risk factors of E. faecalis clinical isolates from patients with UTI in China.

Methods: A total of 115 non-duplicated E. faecalis clinical isolates from patients with UTI were retrospectively collected in a tertiary hospital in China and their clinical data was further analyzed. The linezolid and tedizolid susceptibility were determined by agar dilution. The resistance genes, including erm(A), erm(B), erm(C), tet(M), optrA, cfr, cfr(B), poxtA, and MLST-based housekeeping genes were investigated by PCR.

Results: In 115 non-duplicated E. faecalis clinical isolates from the patients with UTI in this hospital setting, the frequency of linezolid or tedizolid-resistant/intermediate isolates were 22.61 and 13.04%, respectively, and the frequency of linezolid-resistant/intermediate E. faecalis clinical isolates carrying with erm(A) were 86%. Among the five linezolid-resistant E. faecalis strains found in this study, three optrA-positive isolates and the other two linezolid-resistant strains were G2576U genetic mutations in the V domain of the 23S rRNA genes. The ST clonality analysis indicated that 31.42% (11/35) of ST16 E. faecalis UTI isolates were not susceptible to linezolid. Moreover, the univariable analysis indicated that the high risk factors of linezolid-resistant/intermediate E. faecalis infections involved the indwelling catheter, trachea cannula catheter and the carriage of erm(A) or optrA. Furthermore, the indwelling catheter and trachea cannula catheter were demonstrated as the independent predictors of linezolid-resistant/intermediate E. faecalis strains in patients with UTI by multivariable analysis.

Conclusion: Linezolid-resistant/intermediate E. faecalis associated with urinary tract infections of patients in this hospital setting from China might be explained by the high carriage frequency of optrA genes and moreover, indwelling catheter and trachea cannula should be considered as the independent predictors of linezolid-resistant/intermediate E. faecalis infections. The transmission mechanism of linezolid-resistant/intermediate E. faecalis in this hospital setting should be further studied.

Emergence of linezolid-resistance in vancomycin-resistant Enterococcus faecium ST117 associated with increased linezolid-consumption

OBJECTIVE

We aim to describe the epidemiological, clinical and microbiological characteristics of the linezolid- and vancomycin- resistant Enterococcus faecium (LVRE) in a tertiary care hospital in Germany.

METHODS

We conducted a retrospective analysis of 196 LVRE cases observed from 1st January 2012 to 31th December 2018. Patients' medical charts were reviewed and available LVRE (n = 102) were subjected to whole-genome-sequencing. Antibiotic consumption was measured in defined daily dose (DDD)/100 bed-days (BD).

RESULTS

The prevalence of LVRE isolates among VRE was 6.3 % in 2018. Most patients had an onco-hematological disease (134/196, 68.4 %). From 2012-2018 an increase of +356.7 % of linezolid defined daily dose/100 bed-days was observed. In 71.4 % (90/126, 70 missing values) of the patients, linezolid was prescribed in the previous 6 months. The median exposure to linezolid was 15 days (Interquartile, IQR 9-23). 42/196 (21.4 %) patients had an LVRE-related infection with an overall 30-day mortality rate of 33 %. In 121/196 (61.7 %) patients, linezolid-susceptible VREfm were isolated before LVRE, suggesting secondary acquisition of linezolid resistance. Genetic analysis revealed that most isolates belonged to ST117 (64/102 available isolates, 62.7 %). The G2576T 23S rDNA mutation was identified as the most common resistance mechanism (96/102, 94.1 %). poxtA was identified in two isolates, while cfr, and optrA were not detected.

CONCLUSIONS

Incidence of LVRE related to 23S rDNA mutations is rising and probably associated with antibiotic consumption. Restrictions in the use of linezolid may be needed in order to retain therapeutic options in VRE.

Excellent performance of CHROMagarTM LIN-R to selectively screen for linezolid-resistant enterococci and staphylococci

The increasing number of nosocomial pathogens with resistances against last resort antibiotics like linezolid leads to a pressing need for the reliable detection of these drug-resistant bacteria. National guidelines on infection prevention, e.g., in Germany, have already recommend screening for linezolid-resistant bacteria, although a corresponding screening agar medium has not been provided. In this study we analyzed the performance and reliability of a commercial, chromogenic linezolid screening agar. The medium was capable to predict more than a hundred linezolid-resistant isolates of E. faecium, E. faecalis, S. aureus, S. epidermidis, and S. hominis with excellent sensitivity and specificity. All isolates were collected at the National Reference Centre between 2010 and 2020.

Detection of the Phenicol-Oxazolidinone Resistance Gene poxtA in Enterococcus faecium and Enterococcus faecalis from Food-Producing Animals during 2008-2018 in Korea

We aimed to investigate the presence of the phenicol–oxazolidinone resistance gene poxtA in linezolid-resistant enterococci from food-producing animals and analyze its molecular characteristics. We collected 3941 Enterococcus faecium and 5088 E. faecalis isolates from all provinces of South Korea from 2008 to 2018. We found linezolid resistance in 0.79% (94/3941) of E. faecium and 1.22% (62/5088) of E. faecalis isolates. Overall, 23.1% (36/156) of the linezolid-resistant isolates had the poxtA gene, including 31 E. faecium and five E. faecalis isolates. The poxtA-positive enterococci were mainly isolated from chicken (86.1%; 26/36). Fifteen poxtA-harboring isolates co-carried another linezolid-resistance gene, optrA. Eight E. faecium isolates had an N130K mutation in the ribosomal protein L4, while no mutations were observed in E. faecalis isolates. The poxtA gene was transferred into 10 enterococci by conjugation. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) analysis indicated that poxtA-carrying isolates were heterogeneous. Three E. faecium isolates belonged to CC17 (ST32, ST121, and ST491). To our knowledge, this is the first report on the poxtA gene in Korea. Prudent use of antimicrobials and active surveillance on antimicrobial resistance are urgently needed to reduce the risk of dissemination of the linezolid-resistant isolates in humans and animals.

Thirty years of VRE in Germany - "expect the unexpected": The view from the National Reference Centre for Staphylococci and Enterococci

Enterococci are commensals of the intestinal tract of many animals and humans. Of the various known and still unnamed new enterococcal species, only isolates of Enterococcus faecium and Enterococcus faecalis have received increased medical and public health attention. According to textbook knowledge, the majority of infections are caused by E. faecalis. In recent decades, the number of enterococcal infections has increased, with the increase being exclusively associated with a rising number of nosocomial E. faecium infections. This increase has been accompanied by the dissemination of certain hospital-acquired strain variants and an alarming progress in the development of antibiotic resistance namely vancomycin resistance. With this review we focus on a description of the specific situation of vancomycin resistance among clinical E. faecium isolates in Germany over the past 30 years. The present review describes three VRE episodes in Germany, each of which is framed by the beginning and end of the respective decade. The first episode is specified by the first appearance of VRE in 1990 and a country-wide spread of specific vanA-type VRE strains (ST117/CT24) until the late 1990s. The second decade was initially marked by regional clusters and VRE outbreaks in hospitals in South-Western Germany in 2004 and 2005, mainly caused by vanA-type VRE of ST203. Against the background of a certain "basic level" of VRE prevalence throughout Germany, an early shift from the vanA genotype to the vanB genotype in clinical isolates already occurred at the end of the 2000s without much notice. With the beginning of the third decade in 2010, VRE rates in Germany have permanently increased, first in some federal states and soon after country-wide. Besides an increase in VRE prevalence, this decade was marked by a sharp increase in vanB-type resistance and a dominance of a few, novel strain variants like ST192 and later on ST117 (CT71, CT469) and ST80 (CT1065). The largest VRE outbreak, which involved about 2,900 patients and lasted over three years, was caused by a novel and until that time, unknown strain type of ST80/CT1013 (vanB). Across all periods, VRE outbreaks were mainly oligoclonal and strain types varied over space (hospital wards) and time. The spread of VRE strains obviously respects political borders; for instance, both vancomycin-variable enterococci which were highly prevalent in Denmark and ST796 VRE which successfully disseminated in Australia and Switzerland, were still completely absent among German hospital patients, until to date.

Hospital outbreak of linezolid-resistant and vancomycin-resistant ST80 Enterococcus faecium harbouring an optrA-encoding conjugative plasmid investigated by whole-genome sequencing

BACKGROUND

Linezolid is an antibiotic used to treat infections caused by multi-drug-resistant Gram-positive bacteria. Linezolid resistance in enterococci has been reported with increasing frequency, with a recent rise in resistance encoded by optrA, poxtA or cfr.

AIM

To investigate a hospital outbreak of linezolid- and vancomycin-resistant Enterococcus faecium (LVREfm) using whole-genome sequencing (WGS).

METHODS

Thirty-nine VREfm from patient screening (19 isolates, 17 patients) and environmental sites (20 isolates) recovered in October 2019 were investigated. Isolates were screened using polymerase chain reaction for optrA, poxtA and cfr, and underwent Illumina MiSeq WGS. Isolate relatedness was assessed using E. faecium core genome multi-locus sequence typing (cgMLST). One LVREfm underwent MinION long-read WGS (Oxford Nanopore Technologies) and hybrid assembly with MiSeq short-read sequences to resolve an optrA-encoding plasmid.

FINDINGS

Twenty isolates (51.3%) were LVREfm and optrA-positive, including the LVREfm from the index patient. A closely related cluster of 28 sequence type (ST) 80 isolates was identified by cgMLST, including all 20 LVREfm and eight linezolid-susceptible VREfm, with an average allelic difference of two (range 0-10), indicating an outbreak. Nineteen (95%) LVREfm harboured a 56,684-bp conjugative plasmid (pEfmO_03). The remaining LVREfm exhibited 44.1% sequence coverage to pEfmO_03. The presence of pEfmO_03 in LVREfm and the close relatedness of the outbreak cluster isolates indicated the spread of a single strain. The outbreak was terminated by enhanced infection prevention and control (IPC) and environmental cleaning measures, ceasing ward admissions and ward-dedicated staff.

CONCLUSION

WGS was central in investigating an outbreak of ST80 LVREfm. The rapid implementation of enhanced IPC measures terminated the outbreak.