Linezolid-resistant Enterococcus Research Articles

The epidemiology of multidrug-resistant organisms in persons diagnosed with cancer in Norway, 2008–2018: expanding surveillance using existing laboratory and register data

Surveillance has revealed an increase of multidrug-resistant organisms (MDROs), even in low-prevalent settings such as Norway. MDROs pose a particular threat to at-risk populations, including persons with cancer. It is necessary to include such populations in future infection surveillance. By combining existing data sources, we aimed to describe the epidemiology of MDROs in persons diagnosed with cancer in Norway from 2008 to 2018. A cohort was established using data from the Cancer Registry of Norway, which was then linked to notifications of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin- and/or linezolid-resistant enterococci (V/LRE), and carbapenemase-producing Gram-negative bacilli (CP-GNB) from the Norwegian Surveillance System for Communicable Diseases, and laboratory data on third-generation cephalosporin-resistant Enterobacterales (3GCR-E) from Oslo University Hospital (OUH). We described the incidence of MDROs and resistance proportion in Enterobacterales from 6 months prior to the person’s first cancer diagnosis and up to 3 years after. The cohort included 322,005 persons, of which 0.3% (878) were diagnosed with notifiable MDROs. Peak incidence rates per 100,000 person-years were 60.9 for MRSA, 97.2 for V/LRE, and 6.8 for CP-GNB. The proportion of 3GCR-E in Enterobacterales in blood or urine cultures at OUH was 6% (746/12,534). Despite overall low MDRO incidence, there was an unfavourable trend in the incidence and resistance proportion of Gram-negative bacteria. To address this, there is a need for effective infection control and surveillance. Our study demonstrated the feasibility of expanding the surveillance of MDROs and at-risk populations through the linkage of existing laboratory and register data.

The Synergistic Activity of Rhamnolipid Combined with Linezolid against Linezolid-Resistant Enterococcus faecium.

Enterococci resistance is increasing sharply, which poses a serious threat to public health. Rhamnolipids are a kind of amphiphilic compound used for its bioactivities, while the combination of nontraditional drugs to restore linezolid activity is an attractive strategy to treat infections caused by these pathogens. This study aimed to investigate the activity of linezolid in combination with the rhamnolipids against Enterococcus faecium. Here, we determined that the rhamnolipids could enhance the efficacy of linezolid against enterococci infections by a checkerboard MIC assay, a time-kill assay, a combined disk test, an anti-biofilm assay, molecular simulation dynamics, and mouse infection models. We identified that the combination of rhamnolipids and linezolid restored the linezolid sensitivity. Anti-biofilm experiments show that our new scheme can effectively inhibit biofilm generation. The mouse infection model demonstrated that the combination therapy significantly reduced the bacterial load in the feces, colons, and kidneys following subcutaneous administration. This study showed that rhamnolipids could play a synergistic role with linezolid against Enterococcus. Our combined agents could be appealing candidates for developing new combinatorial agents to restore antibiotic efficacy in the treatment of linezolid-resistant Enterococcus infections.

Are enterococcal bloodstream infections an independent risk factor for a poorer 5-year survival or just a marker for severity of illness?-The Munich multicentric enterococci cohort.

The present study provides a substantial contribution to literature, showing that patients with enterococcal bloodstream infections (BSI) have a lower survival rate than those with Escherichia coli (E. coli) bloodstream infections after adjusting for 17 limiting prognostic factors and excluding patients with a limited life expectancy [metastatic tumor disease, Charlson Comorbidity Index (CCI) (greater than or equal to) 5]. This difference in the 5-year long-term survival was mainly driven by Enterococcus faecium (ECFM) bloodstream infections, with vancomycin resistance not being a significant contributing factor. Our findings imply that E. faecium bloodstream infections seem to be an independent risk factor for poor long-term outcomes. As such, future research should confirm this relationship and prioritize investigating its causality through prospective studies.

The emergence of multidrug-resistant Gram-positive bloodstream infections in India - a single center prospective cohort study.

Gram-positive bloodstream infections (BSIs) are an emerging health concern, especially in resource-limited settings. There is a paucity of data regarding the antimicrobial resistance (AMR) pattern of Gram-positive BSIs. The rise in multidrug-resistant infections further convoluted antibiotic selection. We aimed to assess the incidence, clinical and microbiological profile, antimicrobial resistance (AMR) and outcome in Gram-positive BSIs. This was a single-center prospective study conducted at a tertiary care hospital in Western India. All patients (age ≥18 years) with culture-proven Gram-positive BSIs were included. Data were collected on all patients' demography, risk factors, AMR and clinical outcome. A total of 210 clinically significant isolates were grown from July 2020 to December 2021. The incidence of Gram-positive BSIs was 29% (n=61); 55.9% of cases were healthcare-associated, while 44.1% were community-acquired. Coagulase-negative staphylococci (CoNS) were the major isolates (36.1%), followed by Enterococcus spp. (27.9%), methicillin-susceptible Staphylococcus aureus (MSSA) (18%) and methicillin-resistant Staphylococcus aureus (MRSA) (14.7%). The proportion of vancomycin and teicoplanin-resistant CoNS isolates was 13.6% and 19%. Among Enterococcus isolates, the proportion of vancomycin-resistant enterococci (VRE) and linezolid-resistant enterococci (LRE) were 11.8% and 5.9%. The overall mortality in Gram-positive BSIs was 42.6%. Older age, MRSA infection, septic shock, and high NLR were significantly associated with mortality. On the Cox regression model, age ≥65 years (HR: 2.5; 95%CI: 1.1-5.8; p=0.024) and MRSA infection (HR: 3.6; 95%CI: 1.5-8.5; p=0.021) were found as independent predictors of 30-day mortality. This study found substantial mortality with Gram-positive BSIs, especially MRSA infections. Moreover, the emergence of VRE and LRE is also alarming. Active surveillance of AMR and evaluation of mortality predictors may help overcome the therapeutic challenges in managing BSIs.

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

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. 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. 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. 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.

Genomic insights into linezolid-resistant Enterococci revealed its evolutionary diversity and poxtA copy number heterogeneity

ObjectivesThis study aimed to determine the molecular mechanisms of linezolid-resistant enterococci (LRE) in swine slaughterhouses in China and apply the “One Health” perspective to analyse the evolutionary dynamics of poxtA-positive E. faecium in clinical and non-clinical settings worldwide. MethodsThe phenotypic and genomic characteristics of multiple LRE isolates were systematically investigated using antimicrobial susceptibility testing, transfer assays, evolutionary experiments, quantitative RT-PCR assays, whole-genome sequencing, and bioinformatics analyses. ResultsSwine faeces served as a significant reservoir for LRE isolates, and optrA and poxtA were the primary contributors to linezolid resistance. Co-occurrence network analysis revealed a significant interconnection between optrA and several other ARGs. The poxtA copy number heterogeneity and polymorphism were initially observed in E. faecium parental and evolved isolates. The poxtA-carrying tandem repeat region exhibits high mobility and has undergone extensive duplication owing to linezolid pressure. The poxtA copy number varies from four copies on the plasmid of E. faecium IC25 to 11 copies on the plasmid and six copies on the chromosome in the evolved isolate IC25–50_poxtA. Furthermore, phylogenetic analysis of 185 poxtA-positive E. faecium strains worldwide found that one isolate from a French patient in 2018 shared only two SNPs with CC17 E. faecium isolates IC25 and IC7–2 from this study, highlighting the potential global transmission of CC17 poxtA-positive E. faecium between humans and animals. ConclusionThis study identified amplification of poxtA as a response of E. faecium to linezolid pressure. Phylogenetic analysis shed light on the potential global transmission of hospital-associated CC17 poxtA-positive E. faecium in clinical and non-clinical settings.

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.

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. 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. 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. 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). 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.

Bacterial distribution and drug resistance in blood samples of children in Jiangxi Region, 2017-2021.

This study aims to investigate the distribution and drug resistance of bacteria in clinical blood culture specimens from children in Jiangxi province in recent years and to provide a foundation for preventing and treating bloodstream infection diseases in children. The study involved a statistical analysis of the isolation and drug resistance of bacterial strains obtained from blood culture specimens of children in Jiangxi province between 2017 and 2021. The analysis was performed using the WHONET 5.6 software. A total of 7,977 bacterial strains were isolated from the blood samples of children between 2017 and 2021. Of these, 2,334 strains (29.3%) were identified as Gram-negative bacteria, and 5,643 strains (70.7%) were identified as Gram-positive bacteria. The most commonly isolated pathogens were coagulase-negative Staphylococcus, Escherichia coli, and Staphylococcus aureus. Among the Gram-negative bacteria, Escherichia coli (840 strains, 36.0%), Klebsiella pneumoniae (385 strains), Salmonella (283 strains), Acinetobacter baumannii (137 strains), and Pseudomonas aeruginosa (109 strains) were the most prevalent. Among the Gram-positive bacteria, coagulase-negative Staphylococcus (3,424 strains, 60.7%), Staphylococcus aureus (679 strains), Streptococcus pneumoniae (432 strains), Enterococcus sp. (292 strains), and Streptococcus agalactiae (192 strains) were the most common. Resistance to third-generation cephalosporins (cefotaxime/ceftriaxone) was observed in 45.9% and 56.0% of Escherichia coli and Klebsiella pneumoniae strains, respectively, while resistance to carbapenems was observed in 4.6% and 20.3% of these strains, respectively. Resistance to third-generation cephalosporins (cefotaxime/ceftriaxone) was observed in 15.5% of Salmonella strains, while resistance to imipenem was absent. Carbapenem resistance was observed in 17.1% (20/117) and 13% (14/108) of Acinetobacter baumannii and Pseudomonas aeruginosa strains, respectively. Methicillin-resistant Staphylococcus aureus (MRSA) was detected in 32.7% of the strains, while methicillin-resistant coagulase-negative Staphylococcus was detected in 64.3% of the coagulase-negative Staphylococcus strains. No Staphylococcus bacteria resistant to vancomycin were detected. Four strains of vancomycin-resistant Enterococcus faecium were detected over the 5-year period, and one strain of linezolid-resistant Enterococcus faecalis was detected. Gram-positive cocci were the most commonly isolated clinical pathogens in blood specimens from children in Jiangxi province. The composition of the pathogen species showed a slight change over the years. The detection ratios of pathogens varied with age group and season. Although the isolation rate of common carbapenem-resistant Enterobacter bacteria has decreased, it remains high. It is necessary to monitor the antimicrobial resistance of pathogens causing bloodstream infections in children more closely, and antimicrobial agents should be used with caution.

Transmission of linezolid-resistant Enterococcus isolates carrying optrA and poxtA genes in slaughterhouses

IntroductionThe presence of linezolid-resistant enterococci found in animal-derived food has attracted attention for possible transmission to human-derived enterococci through the food chain. Linezolid-resistant enterococci in farms have been widely reported, but enterococci carrying antimicrobial resistance (AMR) genes poxtA, optrA, or cfr(D) in slaughterhouse environments have not been well addressed.MethodsEnterococcus was isolated from the samples collected from two slaughterhouses in Hangzhou, and the Enterococcus carrying linezolidin-resistant genes was identified by PCR. The minimum inhibitory concentration (MIC) of the Enterococcus carrying linezolidin-resistant genes was determined by microbroth dilution method. Finally, the whole genome of strains carrying two or more linezoline resistance genes was sequenced using the Oxford Nanopore TechnologyResultsHere, 291 enterococci strains were isolated from 309 samples (94.17%). A total of 4 poxtA-positive enterococci and 42 optrA-positive enterococci were identified based on PCR. The antimicrobial susceptibility test showed that the highest rate of florfenicol resistance was 97.82% and the rate of multidrug resistance (MDR) was 95.65%. Two strains carried multiple linezolid resistance genes, among which Enterococcus casseliflavus CQFYY22-063 cocarrying optrA, poxtA, and cfr(D) was isolated from the duck cecum, and Enterococcus faecium CQFYH22-006 cocarrying optrA and poxtA was isolated from slaughterhouse sewage for the first time. Furthermore, Oxford Nanopore Technology revealed that the optrA gene of strain CQFYY22-063 was located on the Inc18-type plasmid pFYY063-optrA-70K, and the poxtA and cfr(D) genes were located on the Inc18-type plasmid pFYY063- poxtA-12K. Meanwhile, the poxtA gene of strain CQFYH22-006 was located on the Rep3-type plasmid pFYH006-poxtA-25K, and the optrA gene was located on the chromosome.DiscussionTogether, linezolid resistance in slaughterhouses deserves extensive attention, indicating the need to strengthen the monitoring of different links in the food production chain within the One Health concept.

Co-occurrence of multiple plasmid-borne linezolid resistance genes-optrA, cfr, poxtA2 and cfr(D) in an Enterococcus faecalis isolate from retail meat.

To investigate the molecular characteristics and transferability of plasmid-borne linezolid resistance genes optrA, cfr, poxtA2 and cfr(D) genes in one linezolid-resistant Enterococcus faecalis DM86 from retail meat. E. faecalis DM86 was screened for the presence of known linezolid resistance genes via PCR analysis. Conjugation experiments were used to evaluate the transferability of the resistance genes. The complete genome of E. faecalis DM86 was obtained using both the Illumina and Nanopore platforms. Analysis of the complete sequence showed that E. faecalis DM86 belonged to sequence type 116 (ST116). Four linezolid resistance genes were identified on three plasmids, designated as pDM86-2-cfr, pDM86-3-optrA and pDM86-4-poxtA [cfr(D) co-located]. IS1216 mobile elements were found to flank the cfr and optrA locus on these two plasmids. pDM86-3-optrA encoded the RDK-type OptrA protein and a common genetic array of 'IS1216-fexA-optrA-erm(A)-IS1216' was identified on this plasmid. The cfr(D) gene was closely associated with the poxtA2 gene on pDM86-4-poxtA, and similar plasmids and structures were reported recently in the E. faecalis of animal origin. The intra- and inter-species horizontal transferability of this plasmid to E. faecalis JH2-2, Enterococcus faecium BM4105RF and Staphylococcus aureus RN4220 was also proved, with a frequency of 2.8 × 10-3, 1.7 × 10-3 and 3.4 × 10-5, respectively. This was the first report of the co-existence of up to four plasmid-borne linezolid resistance genes in one E. faecalis. Thus, efficient actions should be exerted to circumvent the microbiota contamination of food and the further spread of these antimicrobial resistance reservoirs.

Complete genome sequence of optrA-carrying Enterococcus faecalis isolated from open pus in a Japanese patient

The occurrence of linezolid resistance in enterococci has recently increased. Here, we report the genomic characterization of Enterococcus faecalis strain JARB-HU0796-isolated from the open pus of a patient in Hiroshima, Japan-which shows nonsusceptibility to linezolid (MIC of 4 µg/mL). JARB-HU0796 whole-genome sequencing was performed using short-read sequencing with Illumina Hiseq X Five and long-read sequencing using GridION. These reads were collected using the assembly pipeline Unicycler and annotated with DFAST. Antimicrobial resistance genes were detected using the Abricate and ResFinder databases, and the sequence type identified using PubMLST. The antimicrobial susceptibility of JARB-HU0796 was determined with the Eiken dry-plate QH02 system. The JARB-HU0796 complete genome contained a circular chromosome (2 722 585 bp) and two circular plasmids (85 996 bp and 58 872 bp). The chromosome harbours the optrA gene, which confers resistance to oxazolidinones and phenicols. JARB-HU0796 showed nonsusceptibility to linezolid and multidrug resistance to other antibiotics. MLST analysis identified JARB-HU0796 as ST476, similar to the optrA-positive E. faecalis ST476 isolates from swine (South Korea, 2020) and pet food (Switzerland, 2022). The optrA region of JARB-HU0796 is nearly identical to that of ST476 E. faecalis strain TZ2, isolated from humans (China, 2013). To the best of our knowledge, this is the first report of the complete genome sequence of E. faecalis ST476 carrying optrA on a chromosome isolated from a patient in Japan. The strain may have originated in animals, suggesting that the organisms acquired resistance to linezolid because the optrA gene may be closely spread between animals and humans.

Identification of plasmids co-carrying cfr(D)/optrA and cfr(D2)/poxtA linezolid resistance genes in two Enterococcus avium isolates from swine brain

Oxazolidinones are critically important antibiotics to treat human infections caused by multidrug-resistant bacteria, therefore the occurrence of linezolid-resistant enterococci from food-producing animals poses a serious risk to human health. In this study, Enterococcus avium 38157 and 44917 strains, isolated from the brain of two unrelated piglets, were found to carry the linezolid resistance genes cfr(D)-optrA, and cfr(D2)-poxtA, respectively. Whole genome sequencing analysis of E. avium 38157 revealed that the genes were co-located on the 36.5-kb pEa_cfr(D)-optrA plasmid showing high identity with the pAT02-c of Enterococcus faecium AT02 from pet food. The optrA region, was 99% identical to the one of the pAv-optrA plasmid from a bovine Aerococcus viridans strain, whereas the cfr(D) genetic context was identical to that of the plasmid 2 of E. faecium 15–307.1. pEa_cfr(D)-optrA was not transferable to enterococcal recipients. In E. avium 44917 a cfr(D)-like gene, named cfr(D2), and the poxtA gene were co-located on the transferable 42.6-kb pEa-cfr(D2)-poxtA plasmid 97% identical to the Tn6349 transposon of the human MRSA AOUC-0915. The cfr(D2) genetic context, fully replaced the Tn6644 that in S. aureus AOUC-0915 harbor the cfr gene. In conclusion, this is, the best of our knowledge, the first report of the new cfr(D2) gene variant. The occurrence of plasmids co-carrying two linezolid resistance genes in enterococci from food-producing animals needs close surveillance to prevent their spread to human pathogens.

Nasotracheal enterococcal carriage and resistomes: detection of optrA-, poxtA- and cfrD-carrying strains in migratory birds, livestock, pets, and in-contact humans in Spain

This study determined the carriage rates and antimicrobial resistance (AMR) genes of enterococci from nasotracheal samples of three healthy animal species and in-contact humans. Nasal samples were collected from 27 dog-owning households (34 dogs, 41 humans) and 4 pig-farms (40 pigs, 10 pig-farmers), and they were processed for enterococci recovery (MALDI-TOF–MS identification). Also, a collection of 144 enterococci previously recovered of tracheal/nasal samples from 87 white stork nestlings were characterized. The AMR phenotypes were determined in all enterococci and AMR genes were studied by PCR/sequencing. MultiLocus-Sequence-Typing was performed for selected isolates. About 72.5% and 60% of the pigs and pig-farmers, and 29.4% and 4.9%, of healthy dogs and owners were enterococci nasal carriers, respectively. In storks, 43.5% of tracheal and 69.2% of nasal samples had enterococci carriages. Enterococci carrying multidrug-resistance phenotype was identified in 72.5%/40.0%/50.0%/23.5%/1.1% of pigs/pig-farmers/dogs/dogs’ owners/storks, respectively. Of special relevance was the detection of linezolid-resistant enterococci (LRE) in (a) 33.3% of pigs (E. faecalis-carrying optrA and/or cfrD of ST59, ST330 or ST474 lineages; E. casseliflavus-carrying optrA and cfrD); (b) 10% of pig farmers (E. faecalis-ST330-carrying optrA); (c) 2.9% of dogs (E. faecalis-ST585-carrying optrA); and (d) 1.7% of storks (E. faecium-ST1736-carrying poxtA). The fexA gene was found in all optrA-positive E. faecalis and E. casseliflavus isolates, while fexB was detected in the poxtA-positive E. faecium isolate. The enterococci diversity and AMR rates from the four hosts reflect differences in antimicrobial selection pressure. The detection of LRE carrying acquired and transferable genes in all the hosts emphasizes the need to monitor LRE using a One-Health approach.

Vancomycin and Linezolid-Resistant Enterococcus Isolates from a Tertiary Care Center in India.

There is increasing development of antibiotic resistance among the Enterococcus species. This study was performed to determine prevalence and characterize the vancomycin-resistant and linezolid-resistant enterococcus isolates from a tertiary care center. Moreover, the antimicrobial susceptibility pattern of these isolates was also determined. A prospective study was performed in Medical College, Kolkata, India, over a period of two years (from January 2018 to December 2019). After obtaining clearance from the Institutional Ethics Committee, Enterococcus isolates from various samples were included in the present investigation. In addition to the various conventional biochemical tests, the VITEK 2 Compact system was used to identify the Enterococcus species. The isolates were tested for antimicrobial susceptibility to different antibiotics using the Kirby-Bauer disk diffusion method and VITEK 2 Compact to determine the minimum inhibitory concentration (MIC). The Clinical and Laboratory Standards Institute (CLSI) 2017 guidelines were used to interpret susceptibility. Multiplex PCR was performed for genetic characterization of the vancomycin-resistant Enterococcus isolates and sequencing was performed for characterization of the linezolid-resistant Enterococcus isolates. During the period of two years, 371 isolates of Enterococcus spp. were obtained from 4934 clinical isolates showing a prevalence of 7.52%. Among these isolates, 239 (64.42%) were Enterococcus faecalis, 114 (30.72%) Enterococcus faecium, and others were Enterococcus durans, Enterococcus casseliflavus, Enterococcus gallinarum, and Enterococcus avium. Among these, 24 (6.47%) were VRE (Vancomycin-Resistant Enterococcus) of which 18 isolates were Van A type and six isolates of Enterococcus casseliflavus and Enterococcus gallinarum were resistant VanC type. There were two linezolid-resistant Enterococcus, and they were found to have the G2576T mutation. Among the 371 isolates, 252 (67.92%) were multi-drug resistant. This study found an increasing prevalence of vancomycin-resistant Enterococcus isolates. There is also an alarming prevalence of multidrug resistance among these isolates.

Detection of Genes Related to Linezolid Resistance (poxtA, cfr, and optrA) in Clinical Isolates of Enterococcus spp. from Humans: A First Report from Iran.

Enterococci may develop resistance to linezolid through chromosomal mutations that involve specific linezolid resistance genes, such as cfr, optrA, and poxtA. The objective of this study was to evaluate the antibiotic susceptibility of enterococcal isolates and identify cfr, optrA, and poxtA genes in MDR isolates. Enterococcal isolates were collected from various clinical specimens at Al-Zahra, Amin, and Khorshid Hospitals in Isfahan. The Enterococcus isolates were identified as belonging to the E. faecalis and E. faecium species by using specific gene (D alanine D alanine ligase ddl) sets in PCR. To detect cfr, optrA, and poxtA genes among the species, a multiplex-PCR assay was performed. Out of 175 isolates, E. faecalis predominated 129/175 (73.7%). Furthermore, the prevalence of vancomycin-resistant Enterococci (VRE) and linezolid-resistant Enterococci (LRE) was 29.7% and 4%, respectively. The overall prevalence of MDR was 91.1%, 68.9%, and 66.6% of E. faecium, E. faecalis, and other Enterococcus spp., respectively. Interestingly, the frequency of optrA (71.4%) in E. faecium and poxtA and crf (42.8%) in E. faecalis were detected among LRE species. A statistically significant relationship (P < 0.05) was found between the presence of the three genes and the occurrence of LRE. This is the first study to report the detection of linezolid resistance genes (cfr, optrA, and poxtA) in clinical Enterococcus spp. isolates from Iran, conducted at Isfahan University of Medical Sciences hospitals. The emergence of enterococcal strains that resist linezolid is concerning as it can lead to the spread of resistant strains among patients, resulting in treatment failure.

The emergence and molecular epidemiological characteristics of foodborne superbacteria resistant to next-generation antimicrobials

Superbacteria are antimicrobial resistant bacteria, and their emergence and widespread became great threats to humanity. Next-generation antimicrobials were developed to deal with existing antimicrobial resistance, but resistant bacteria emerged and spread immediately due to indiscriminate use of antimicrobials. In particular, the foodborne superbacteria are highly serious problem because they are closely related to the overall human life. In this article, we explored the distribution and resistance level of foodborne colistin-resistant Salmonella and linezolid-resistant Enterococcus among through the latest research papers about their resistance and molecular epidemiological transmission route. The transmission of resistance factors between food-derived superbacteria and other environment was also confirmed for the case of next-generation antimicrobials. Therefore, it is increasingly important to develop national and global resistance monitoring projects with One-health scheme.

Detection of optrA and poxtA genes in linezolid-resistant Enterococcus isolates from fur animals in China.

The emergence of linezolid-resistant (LR) enterococci found in food of animal origin arouses attention, but little is known about LR enterococci in fur animals. A total of 342 Enterococcus faecalis and 265 E. faecium strains isolated from fur animals in China from 2015 to 2017 were investigated to determine if LR enterococci (≥16 μg ml-1 ) are present. Overall, two E. faecalis and 12 E. faecium among these isolates were resistant to linezolid. In addition, all LR isolates were classified as multidrug-resistant isolates. We further explore the resistance genes of the LR enterococci, four E. faecalis and two E. faecium isolates contained optrA gene. Two of them co-harboured optrA and poxtA genes. We detected virulence genes in LR enterococci were the following: asa1, cylA, esp, gelE and hyl, among which the highest carrying rate gene was asa1. Besides, all of the LR enterococci we tested had the biofilm-forming ability. It is worth noting that we detected a novel ST type ST2010 from E. faecium 82-2. These data show LR enterococci exist in fur animals and have unique characteristics.

Investigation of a vanA linezolid- and vancomycin-resistant Enterococcus faecium outbreak in the Southwest Indian Ocean (Reunion Island)

IntroductionDual resistance to linezolid and glycopeptides is a milestone reached by certain extensively drug-resistant (XDR) enterococci. This paper describes the molecular and epidemiological investigations of a linezolid-resistant and vancomycin-resistant Enterococcus faecium (E. faecium) (LVREf) outbreak in the French overseas territory of Reunion Island (Indian Ocean). MethodsAll vancomycin-resistant Enterococcus (VRE) isolates detected on Reunion Island between 2015 and 2019 were included in the study. The VRE isolates were phenotypically characterised and genetically explored by whole-genome sequencing (WGS). ResultsSixteen vancomycin-resistant E. faecium (VREf) isolates were retrieved between 2015 and 2019. Seven isolates obtained in 2019 were involved in the outbreak. These seven LVREf isolates from the 2019 outbreak at the University Hospital of Reunion Island (UHRI) were suspected to be related to a linezolid-susceptible VREf strain imported from India. An epidemiological link was highlighted for six of the seven outbreak cases. All the LVREf outbreak isolates were obtained from rectal swabs (colonisation) and resistant to vancomycin (MIC > 128 mg/L) and linezolid (MIC 8–32 mg/L); one isolate was also resistant to daptomycin (MIC 8 mg/L). The seven outbreak isolates were positive for the vanA and optrA genes and belonged to ST761. ConclusionsThese results argue for the strict application of control and prevention measures for VRE clones at high risk of spread, particularly in areas such as Reunion Island where the risk of importation from the Indian subcontinent is high. The regional spread of optrA linezolid-resistance genes in VRE isolates is a matter of concern, due to possibility of treatment failure.

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.

Resistance towards Critically Important Antimicrobials among Enterococcus faecalis and E. faecium in Poultry Farm Environments in Selangor, Malaysia.

Multidrug resistant (MDR) enterococci pose significant public health challenges. However, the extent of resistance in the environment is less explored. This study aimed to determine the antibiotic resistance in a poultry farm environment. Eighty enterococcal isolates recovered from the soil and effluent water of 28 poultry farms in Selangor state were included in the study for further bacterial identification and antibiotic susceptibility testing using a VITEK 2 system. Data were analyzed using Statistical Package for Social Science (SPSS) version 27. The resistance rate and MDR of enterococcal isolates were reported. Out of 80 isolates recovered, 72 (90%) exhibited resistance to at least one antibiotic, with 50 isolates (62.5%) being found to be MDR. All linezolid-resistant enterococci (LRE) exhibit MDR, which constituted 40% of resistance among all the isolates recovered from poultry environment. Since linezolid is listed as critically important antibiotics for clinical use by the World Health Organization (WHO), the higher resistance towards it and other critically important antibiotic for human use is a serious concern. Hence, relevant agencies need to investigate the use of clinically important antimicrobials in poultry farms paying special attention towards linezolid or any other antibiotics that can facilitate the development of LRE.