Clinical and molecular epidemiology of vancomycin-resistant Enterococcus faecium bacteremia from an Indian tertiary hospital

Enterococcal bacteremia in children: Clinical Significance of vancomycin resistance

BACKGROUND

We aimed to describe the clinical and microbiological characteristics of enterococcal bacteremia, as well as the effect of Enterococcus resistance against vancomycin on clinical outcomes in Korean children.

METHODS

We retrospectively reviewed the medical records of children diagnosed with enterococci isolated from blood cultures at Pusan National University Children's Hospital between December 2009 and November 2021.

RESULTS

In total, 64 patients were enrolled in the study. The median age was 0 years (range 0-15), and 43 (67.2%) patients were male. Enterococcus faecalis (50%) was the most commonly identified bacterial strain. Significant underlying diseases were present in 60 patients (93.8%), and the source of bacteremia was identified in 36 patients (56.3%). Among these, intravascular device was the most common identifiable source. Fifty-six (87.5%) patients had previously received broad-spectrum antibiotics and 54 (84.4%) patients were nosocomial in origin. Twenty-nine (45.3%) strains were resistant to ampicillin, and 16 (25%) strains were resistant to vancomycin. All patients with vancomycin-resistant enterococci (VRE) had underlying disease (P = 0.199), and focus of bacteremia was significantly more frequent in VRE patients (P = 0.014). Of all the patients, after appropriate antibiotic treatment, five (7.8%) patients had recurrent enterococcal bacteremia, and seven (10.9%) patients were diagnosed with bacteremia, defined as other pathogens from blood culture. The 30-day mortality rate was 7.8%.

CONCLUSION

Enterococcal bacteremia in children is usually nosocomial and occurs in children with serious underlying diseases. Because the number of enrolled patients and mortality were small in our study, it is difficult to identify whether the factor that determines prognosis in patients with enterococcal bacteremia is VRE or an underlying disease. Further studies with a large number of patients in a specific group are needed.

Enterococcus: Understanding Their Resistance Mechanisms, Therapeutic Challenges, and Emerging Threats

The Enterococcus species originates as non-harmful bacteria indigenous to human intestines but has transformed into severe hospital-acquired pathogens due to antimicrobial resistance (AMR). The clinical species Enterococcus faecalis and Enterococcus faecium create the most relevant infections because they appear in urinary tract infections, bloodstream infections, endocarditis, and wound infections. Enterococcus species demonstrate multiple antibiotic class resistance and resistance determinant acquisition properties that make treatment difficult for medical professionals. Vancomycin-resistant enterococci (VRE) together with high-level aminoglycoside-resistant strains and resistance to both linezolid and daptomycin have exhausted available treatment options. The review investigates the development process of Enterococcus infections by examining virulence characteristics, which involve biofilm production and defense mechanisms against the immune response and transmission of resistance genes. A thorough investigation of medical publications used Google Scholar along with PubMed and ScienceDirect and Medical Subject Headings (MeSH) as appropriate search terms. The traditional classification of Enterococcus species from historical context to modern epidemiology and pathogenesis and available treatment and test approaches are explained in this review. This section examines two categories of resistance together with their mechanisms of action with a specific focus on vancomycin resistance produced by van gene clusters as well as its prevalence trends. An examination of how horizontal gene transfer functions in transferring resistance throughout healthcare facilities is included. The paper investigates the different symptoms of enterococcal infections together with diagnostic obstacles and treatment modalities. Drug-resistant Enterococcus infections continue to increase internationally, so healthcare professionals need new therapeutic methods, better antimicrobial policies, and stronger infection prevention measures. The examination surveys Enterococcus infections through an extensive evaluation of developing resistance patterns combined with emerging intervention requirements.

Antimicrobial resistance, virulence gene profiles, and molecular epidemiology of enterococcal isolates from patients with urinary tract infections in Shanghai, China

Urinary tract infections (UTIs) are among the most prevalent infectious diseases, yet there is still limited understanding of the epidemiology of Enterococcal strains isolated from UTI patients in Shanghai. This study aims to elucidate the antimicrobial resistance profiles, virulence gene carriage, and molecular epidemiology of selected Enterococcal strains from UTI patients in Shanghai. A cohort of 80 Enterococcus faecalis and 40 Enterococcus faecium clinical isolates were randomly selected from UTI patients from October 2022 to March 2023. No vancomycin-resistant strains were identified based on minimum inhibitory concentration (MIC) testing. However, five strains of linezolid-resistant E. faecalis were identified, all of which were confirmed to be optrA-positive through whole-genome sequencing (WGS), with ST300 being reported as the first instance of this ST type in China. Polymerase chain reaction (PCR) assays were employed to ascertain the presence of virulence genes and multi-locus sequence type (MLST). In E. faecalis, the most common virulence genes were asal (75%), gelE (65%), esp (52.5%), and cylA (47.5%). In contrast, E. faecium primarily exhibited esp (65%) and hyl (12.5%). Among the E. faecalis strains, 21 distinct MLST types were identified, with ST16 and ST179 prevailing. Conversely, E. faecium exhibited only five MLST types, with ST78 being predominant. The prevalence of E. faecalis CC16 and E. faecium CC17 further complicates the treatment landscape for Enterococcal UTIs.

IMPORTANCE

This study highlighted the critical need to understand Enterococcal strains causing UTIs in Shanghai, given their high prevalence. By assessing antimicrobial resistance profiles, virulence gene presence, and molecular epidemiology, the research offered valuable insights into the local epidemiology of Enterococcus faecalis and Enterococcus. faecium. Identifying linezolid-resistant strains, all of which carry the optrA gene, including the first report of ST300 in China and recognizing dominant MLST types, such as ST16 and ST179 for E. faecalis and ST78 for E. faecium, are vital for guiding treatment and addressing the challenges these infections present. The data emphasize the need for ongoing surveillance and customized therapeutic approaches to combat emerging resistance and virulence factors in Enterococcal UTIs.

Analysis of molecular epidemiological characteristics and antimicrobial susceptibility of vancomycin-resistant and linezolid-resistant Enterococcus in China

BACKGROUND

This study investigates the distribution and characteristics of linezolid and vancomycin susceptibilities among Enterococcus faecalis (E. faecalis) and Enterococcus faecium (E. faecium) and explores the underlying resistance mechanisms.

METHODS

A total of 2842 Enterococcus clinical isolates from patients were retrospectively collected, and their clinical data were further analyzed. The minimum inhibitory concentrations (MICs) of vancomycin and linezolid were validated by broth dilution method. The resistance genes optrA, cfr, vanA, vanB and vanM were investigated using polymerase chain reaction (PCR). Housekeeping genes and resistance genes were obtianed through whole-genome sequencing (WGS).

RESULTS

Of the 2842 Enterococcus isolates, 88.5% (2516) originated from urine, with E. faecium accounted for 60.1% of these. The vanA gene was identified in 27/28 vancomycin resistant Enterococcus (VRE) isolates, 4 of which carried both vanA and vanM genes. The remaining strain was vanM positive. The optrA gene was identified in all E. faecalis isolates among linezolid resistant Enterococcus (LRE). E. faecium showed a higher multiple antibiotic resistance index (MAR index) compared to E. faecalis. The multi-locus sequence typing (MLST) showed the sequence type of E. faecium mainly belongs to clonal complex (CC) 17, nearly E. faecalis isolates analyzed were differentiated into 7 characteristics of sequence types (STs), among which ST16 of CC16 were the major lineage.

CONCLUSION

Urine was the primary source of VRE and LRE isolates in this study. E. faecium showed higher levels of resistance compared to E. faecalis. OptrA gene was detected in 91.6% of LRE, which could explain linezolid resistance, and van genes were detected in all vancomycin resistant Enterococcus strains, while vanA was a key resistance mechanism in VRE identified in this study.

Molecular characterization and biofilm formation ability of Enterococcus faecium and Enterococcus faecalis bloodstream isolates from a Chinese tertiary hospital in Beijing

To investigate the molecular characteristics and biofilm-forming ability of 116 Enterococcus faecium (Efm) and 72 Enterococcus faecalis (Efs) isolates obtained from patients with bloodstream infections (BSI) at a Chinese hospital between July 2011 and March 2018. The presence of glycopeptide resistance genes and five virulence genes (esp, gelE, asa1, hyl, and cylA) was screened using two multiplex PCR. MLST was used to assess the clonality. Crystal violet staining was used to detect biofilms. Vancomycin resistance was detected in 30.1% of Efm and 2.8% of Efs isolates, respectively. All VRE strains carried the vanA gene. The esp, gelE, asa1, and cylA genes in 72 Efs strains were detected at 62.5%, 84.7%, 84.7%, and 69.4%, respectively. Among the 116 Efm isolates, 74.1% and 25.8% carried esp and hyl, respectively. The esp gene was significantly associated with vancomycin-resistant Efm (VREfm) compared to vancomycin-susceptible Efm (VSEfm). In total, 91.7% of Efs and 20.0% of Efm produced biofilms. Twenty-six STs were identified among the 72 Efs isolates, with ST4 (29.2%) being the predominant. In total, 116 Efm strains were grouped into 26 STs, with ST78 (46.6%) being the predominant. Both VREfm (41.7%) and VSEfm (48.8%) were dominant in ST78. There is no clear evidence suggesting that some STs are associated with vancomycin resistance or biofilm formation. Both Efm and Efs BSI isolates showed a polyclonal pattern with a dominant clone and many unique types, implying the coexistence of clonal dissemination and an influx of new clones. The horizontal transmission of resistance genes may play a more important role in VREfm prevalence than clonal expansion.

Genomic characterization of vancomycin-resistant Enterococcus faecium clonal complex 17 isolated from urine in tertiary hospitals in Northeastern Thailand

Vancomycin-resistant Enterococci (VREs) have increasingly become a major nosocomial pathogen worldwide, earning high-priority category from the World Health Organization (WHO) due to their antibiotic resistance. Among VREs, vancomycin-resistant Enterococcus faecium (VREfm) is particularly concerning, frequently isolated and resistant to many antibiotics used in hospital-acquired infections. This study investigated VREfm isolates from rural tertiary hospitals in Northeastern Thailand based both antibiotic susceptibility testing and whole-genome sequencing. All isolates showed resistance to vancomycin, ampicillin, erythromycin, tetracycline, ciprofloxacin, norfloxacin, and rifampin. Nitrofurantoin and tigecycline resistance were also observed in nearly all isolates. Conversely, all isolates remained susceptible to chloramphenicol, daptomycin, and linezolid. Genomic characterization revealed that all VREfm isolates belonged to clonal complex 17 (CC17), primarily consisting of sequence type (ST) 80, followed by ST17, ST761, and ST117. Additionally, all isolates harbored numerous antimicrobial-resistant genes, including vanA, tet(L), tet(M), aac(6')-li, ant(6)-Ia, aph(3')-III, aac(6')-aph(2″), aph(2″)-la, ant(9)-la, erm(B), msr(C), erm(T), erm(A), fosB, dfrG, and cfr(B). Notably, all isolates contained virulence genes, for collagen adhesin (acm) and cell wall adhesin (efafm), while hylEfm (glycosyl hydrolase) was detected in VREfm ST80. This study provided important information for understanding the genomic features of VREfm isolated from urine.

Rapid and specific detection of Enterococcus faecium with an isothermal amplification and lateral flow strip combined method

Enterococcus faecium is responsible for a highly contagious, drug-resistant nosocomial infection that often causes serious illness. In this study, a rapid and sensitive RPA-LFS (recombinase polymerase amplification-lateral flow strip) method for the detection of E. faecium was established based on specific primers and probes designed using the ddl gene. To verify the specificity and sensitivity of the method, 26 specific strains and 100-106 CFU/μL E. faecium were selected for detection. The results show that the proposed method can specifically detect E. faecium, and the minimum detection limit is 100 CFU/μL. To compare the clinical application of the method with qPCR, 181 clinical samples were collected for testing. RPA-LFS and qPCR had the same practical applicability, and 61 parts of E. faecium were detected in 183 clinical samples. The methods developed in this study not only have the advantages of rapid sensitivity and specificity but also meet the needs of remote areas with scarce medical resources.

Epidemiology and outcomes of vancomycin-resistant enterococcus infections: a systematic review and meta-analysis

Vancomycin-resistant enterococci (VRE) cause many infections in the healthcare context. Knowledge regarding the epidemiology and burden of VRE infections, however, remains fragmented. We aimed to summarize recent studies on VRE epidemiology and outcomes in hospitals, long-term-care facilities (LTCFs) and nursing homes worldwide based on current epidemiological reports. We searched MEDLINE/PubMed, the Cochrane Library, and Web of Science for observational studies, which reported on VRE faecium and faecalis infections in in-patients published between January 2014 and December 2020. Outcomes were incidence, infection rate, mortality, length of stay (LOS), and healthcare costs. We conducted a meta-analysis on mortality (PROSPERO registration number: CRD42020146389). Of 681 identified publications, 57 studies were included in the analysis. Overall quality of evidence was moderate to low. VRE incidence was rarely and heterogeneously reported. VRE infection rate differed highly (1-55%). The meta-analysis showed a higher mortality for VRE faecium bloodstream infections (BSIs) compared with VSE faecium BSIs (risk ratio, RR 1.46; 95% confidence interval (CI) 1.17-1.82). No difference was observed when comparing VRE faecium vs VRE faecalis BSI (RR 1.00, 95% CI 0.52-1.93). LOS was higher in BSIs caused by E. faecium vs E. faecalis. Only three studies reported healthcare costs. In contrast to previous findings, our meta-analysis of included studies indicates that vancomycin resistance independent of VRE species may be associated with a higher mortality. We identified a lack of standardization in reporting outcomes, information regarding healthcare costs, and state-of-the-art microbiological species identification methodology, which may inform the set-up and reporting of future studies.

Virulence gene detection and antimicrobial resistance analysis of Enterococcus faecium in captive giant pandas (Ailuropoda melanoleuca) in China

BACKGROUND

The emergence of multidrug resistance among enterococci makes effective treatment of enterococcal infections more challenging. Giant pandas (Ailuropoda melanoleuca) are vulnerable to oral trauma and lesions as they feast on bamboo. Enterococci may contaminate such oral lesions and cause infection necessitating treatment with antibiotics. However, few studies have focused on the virulence and drug resistance of oral-derived enterococci, including Enterococcus faecium, in giant pandas. In this study, we analyzed the prevalence of 8 virulence genes and 14 drug resistance genes in E. faecium isolates isolated from saliva samples of giant pandas held in captivity in China and examined the antimicrobial drug susceptibility patterns of the E. faecium isolates.

RESULTS

Twenty-eight isolates of E. faecium were successfully isolated from the saliva samples. Four virulence genes were detected, with the acm gene showing the highest prevalence (89%). The cylA, cpd, esp, and hyl genes were not detected. The isolated E. faecium isolates possessed strong resistance to a variety of drugs; however, they were sensitive to high concentrations of aminoglycosides. The resistance rates to vancomycin, linezolid, and nitrofurantoin were higher than those previously revealed by similar studies in China and other countries.

CONCLUSIONS

The findings of the present study indicate the drugs of choice for treatment of oral E. faecium infection in the giant panda.

Novel linear plasmids carrying vanA cluster drives the spread of vancomycin resistance in Enterococcus faecium in India

OBJECTIVES

The genetic basis for the spread of vancomycin resistance in E. faecium is largely unexplored in India. The present study aimed to investigate the plasmid diversity and variation of Tn1546 associated with vanA harbouring VREfm isolates.

METHODS

A total of 122 VREfm isolates collected from blood cultures were included in this study. MLST analysis was performed on all isolates and they were also screened for the presence of vanA and vanB genes. Whole genome sequencing was performed for a subset of fifteen VREfm isolates belonging to ST1643.

RESULTS

All of the 122 VREfm isolates carried the vanA gene. Twenty four different sequence types were seen, of these ST1643, ST80 and ST17 were predominant. Whole genome sequencing was performed on fifteen VREfm isolates belonging to ST1643. For eight isolates the vanA gene was found on pRUM like circular plasmids, and for the remaining seven isolates, the vanA gene was found in linear plasmids. Novel Tn1546 variants carrying vanA were found on both circular and linear plasmids. Interestingly, co-presence of vanA and optrA were seen in the backbone of three linear plasmids.

CONCLUSION

Multiple vanA carrying plasmids and Tn1546 like elements were involved in the dissemination of vancomycin resistance in VREfm. The co-occurrence of Tn1546 carrying vanA and Tn554 family transposon carrying optrA on the backbone of plasmids is worrisome. The dissemination of such plasmids may pose treatment and infection control challenges.

Perfil epidemiológico de la infección por Enterococcus SPP en un hospital regional

Introducción: los enterococos son responsables de múltiples infecciones y por su creciente patrón de resistencia se ha vuelto de interés en el país y en el mundo. Objetivo: caracterizar las infecciones por Enterococcus spp. Metodología: estudio descriptivo, retrospectivo observacional transversal desde enero 2015 hasta enero 2018 en un hospital regional. Resultados: la prevalencia de las infecciones por Enterococcus spp. fue de 0,154%. El E. faecalis fue el más aislado, seguido del E. faecium. La resistencia a ampicilina fue de 19% y a vancomicina de 10%; 32% de los pacientes tuvieron terapia empírica con vancomicina y 22% con piperacilina tazobactam, la mediana de antibioticoterapia fue de 10 días. Discusión: el interés por los Enterococcus spp. se ha incrementado debido a que representan una carga importante en las infecciones asociadas con la atención en salud (IAAS). La mayoría se dan en hombres con una edad mediana de 40 a 60 años, hospitalizados en UCI, con infecciones urinarias y comorbilidades como inmunosupresión y cirugías previas. Conclusión: como ha venido reportándose aumento en las tasas de resistencia a vancomicina y ampicilina, se recomienda el uso responsable de la terapia antibiótica, con la finalidad de erradicar en forma eficaz al patógeno y prevenir nuevas resistencias.

A vanA vancomycin-resistant Enterococcus faecium ST80 outbreak resulting from a single importation event

BACKGROUND

A marked genotype shift among vancomycin-resistant Enterococcus faecium (VREfm) from vanB to vanA in Australia between 2011 and 2015 is a well-known phenomenon. It is hypothesized that this was caused by multiple independent clones emerging simultaneously in different settings and/or regions.

OBJECTIVES

To gain insights into the circumstances surrounding the shift from vanB to vanA VREfm in one Australian hospital.

METHODS

The genomes of 69 vanA VREfm isolates from St George Hospital collected between 2009 and 2018 were studied. An expansion of ST80 vanA VREfm was noted following a single introduction. ST80 isolates were thus further characterized using hybrid sequencing and contextualized through comparisons with other published Australian ST80 isolates. Phylogenies were constructed with plasmid sequences compared with the index isolate.

RESULTS

The 2011 expansion of ST80 vanA VREfm isolates in our institution originated from the 2009 index isolate, from a patient transferred from overseas. Phylogenetic analysis with other Australian ST80 vanA VREfm isolates showed that the 2011 expansion event was unique, with limited spread to adjacent local health districts. Plasmid analysis showed multiple variants, which can also be traced back to the 2009 isolate, consistent with ongoing plasmid adaptation over time.

CONCLUSIONS

These findings confirm an expansion event following a VREfm introduction event leading to a sustained clonal and plasmid outbreak over several years. Moreover, it demonstrates the complexity of countrywide replacement events. This study also highlights the use of hybrid sequencing in establishing an epidemiological relationship to the index isolate that was initially inapparent.