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.

Spread of vancomycin-resistant Enterococcus faecium ST133 in the aquatic environment in Switzerland

OBJECTIVES

The global dissemination of vancomycin-resistant enterococci (VRE) has become a serious public-health concern. Although outbreaks are typically caused by nosocomial transmission, contaminated food and water may contribute to the spread of VRE. The aim of this study was to assess the presence of VRE in flowing surface water bodies in Switzerland and to characterise the isolates.

METHODS

Surface water was sampled from rivers, streams and canals throughout Switzerland and was screened for the presence of VRE. Whole-genome sequencing was used to identify antimicrobial resistance genes and the phylogenetic similarity of the obtained isolates.

RESULTS

VRE were detected in 6 (3.1%) of 191 water samples. The six VRE-containing samples were all collected near treated wastewater discharge sites. The six isolates were identified as Enterococcus faecium sequence type 133 (ST133) and harboured the vancomycin resistance-conferring vanA gene cluster on transposon Tn1546. They showed a close phylogenetic relationship to ST133 swine faecal isolates obtained during a previously reported screening in Switzerland.

CONCLUSION

Our results suggest that surface water contributes to the environmental dissemination of VRE. Repeated identification of ST133 clones in geographically distinct water sampling sites and swine faecal samples collected in slaughterhouses may indicate a local dominance of this VRE lineage in Switzerland.

vB_EfaS-DELF1, a novel Siphoviridae bacteriophage with highly effective lytic activity against vancomycin-resistant Enterococcus faecalis

Enterococcus faecalis is an environmental agent of bovine mastitis in cows and has many cytopathic effects on the urinary tract in both humans and animals. In this study, a novel lytic bacteriophage, vB_EfaS-DELF1, was isolated against 21 E. faecalis isolated from bovine mastitis, including vancomycin-resistant E. faecalis (VRE). vB_EfaS-DELF1 bacteriophage was specific for E. faecalis and showed no lytic effects against other tested Enterococcus spp., Gram-negative, or Gram-positive bacteria. Moreover, no activity was observed against yogurt starters. The phage suspension was stable in a wide range of pH, salinity, and temperature. It retained its activity in 3.5 % fat milk. vB_EfaS-DELF1 has the common phenotypic features of Siphoviridae with a double-strand DNA of 40,248 bp in length and a G + C content of 34.9 %. The genome encodes 62 putative ORFs and no tRNA. No undesirable genes such as lysogenic mediators, antibiotic resistance, or virulence factor genes were detected in the genome. The comparative genomic analysis demonstrated similarity to the other available phage genomes. The highest similarity was observed with two other phages (50 % coverage and 82.38 % identities with IME-EFm1; 35 % coverage and 86.22 % identities with IME-EFm5) that were placed in the same clade. The differences with the other aligned phages were high and were placed in distant clusters. Regarding the specificity of this new bacteriophage against all of the tested E. faecalis isolates and, in particular, against the vancomycin-resistant ones, and also the absence of antibiotic resistance or virulence genes in its genome, vB_EfaS-DELF1 is suggested as a potential candidate for biocontrol of E. faecalis infections.

Comparative genomics of vancomycin-resistant Enterococcus spp. revealed common resistome determinants from hospital wastewater to aquatic environments

The rise of vancomycin-resistant Enterococcus spp. (VRE) has led to treatment challenges in hospital settings worldwide. Hospital wastewater (HW) might disseminate this threat to the aquatic environment. Thus, this study elucidates the VRE resistance quotient (RQ) of different environmental matrixes in wastewater and compares genomic determinants of VRE strains recovered from HW to water resources. Presumptive Enterococcus spp. and VRE were quantified and isolated using standard microbiological procedures. Fourteen VRE genomes were then sequenced using an Illumina HiSeq X™ Ten platform. Subsequently, VRE genomes were compared based on antibiotic resistance genes, plasmids, bacteriophages, insertion sequences, transposons, virulence and pathogenicity. Wastewater effluent showed the highest RQ among all sampled matrixes. The phylogeny of vancomycin-resistant E. faecalis (VREfs) and E. faecium (VREfm) revealed a tree structure based on their respective sequence type. A comparative genomic analysis of 14 genomes highlighted regions encoding phage protein, phage holin, phage integrase, integrase and transposase on both query genomes and the reference genome. Acquired resistance to vancomycin was conferred by vanA, vanN, vanL, vanG and the intrinsic resistance vanC operons. Plasmids were dominated by the presence of conserved areas of the replication initiating genes (rep). The Tn3-like and Tn917 transposons were present in all erythromycin-carrying erm(B) isolated VRE genomes. All VRE genomes expect one were putatively predicted as human pathogens with varying degrees of virulence. The presence of such resistant bacteria in African water resource is of great public health concern. It is, therefore, recommended that these bacteria be tracked and characterised from different environments to contribute to improved epidemiological containment action.

Comparison of biofilm production and virulence gene distribution among community- and hospital-acquired Staphylococcus aureus isolates from northwestern Iran

INTRODUCTION

The emergence of antimicrobial-resistant isolates among Staphylococcus aureus and their genetic variations has become a major concern worldwide. The present study aims at comparing the biofilm formation and the genes encoding adhesion molecules in methicillin-susceptible, community- and hospital-acquired methicillin-resistant, vancomycin-intermediate and vancomycin-resistant S. aureus isolates.

METHODOLOGY

The current study was conducted on 60 S.aureus isolates, collected at Urmia University of Medical Sciences, Iran, between the years 2014 and 2015. The modified Congo-red agar and Microtiter plate methods were used to determine biofilm production. PCR was used to detect the genes which were associated with a protein family of staphylococcal microbial surface components recognizing adhesive matrix molecules. The data were analyzed using SPSS (IBM SPSS Statistics, version 16).

RESULTS

Of 60 isolates, 57 (95%) were biofilm producers. Unlike the bbp gene, which was only detected in 3 (5%) isolates, the eno and icaD genes were identified as the most prevalent as they were detected in 53 (88.3%) and 50 (85%) of 60 isolates, respectively. The dominant virulotype comprised eight genes (icaA, icaD, clfA, clfB, fnbA, cna, eno, ebpS) in eight isolates, six of which were community-acquired-MRSAs.

CONCLUSION

A high percentage of the S. aureus isolates could produce a biofilm which is more common among methicillin-susceptible isolates. The high frequency of eno and icaD genes suggests that these genes may synergistically function in the onset and progression of bacterial colonization and biofilm formation. Meanwhile, this ability may help the bacteria resist the exposure of antibacterial agents and cause severe infections.

Exogenous endophthalmitis caused by Enterococcus casseliflavus: A case report

BACKGROUND

Endophthalmitis caused by Enterococci is rare, and cases involving vancomycin-resistant enterococci are even rarer. We report the first case of Enterococcus casseliflavus endophthalmitis associated with injury caused by a pig. We also review reported cases of exogenous endophthalmitis caused by Enterococcus casseliflavus and discuss the clinical management and prognosis of this disease.

CASE SUMMARY

A 43-year-old man with no previous visual problems complained of endophthalmitis in his left eye following injury caused by a pig. Visual acuity was light perception and B-ultrasonography revealed vitreous opacities with retinal detachment. He was treated with intravitreal vancomycin and ceftazidime after refusing vitrectomy. However, the vitreous opacities and retinal detachment deteriorated and he underwent vitrectomy 5 d post-injury. Intraoperatively, advanced rhegmatogenous and tractional retinal detachment with proliferative vitreoretinopathy were observed. On postoperative day 5, vitreous cultures grew Gram-positive cocci identified as Enterococcus casseliflavus. A 2-wk course of intravenous ampicillin and dexamethasone was commenced. On postoperative day 14, visual acuity improved to hand movement. At 6 mo post-injury, visual acuity improved to 20/667, but optic atrophy was present.

CONCLUSION

Systemic administration of linezolid in the treatment of Enterococcus casseliflavus endophthalmitis can improve visual acuity. However, intravitreal amikacin should be considered despite concerns of toxicity when oral linezolid fails to prompt improvement.

Vancomycin-resistant enterococci (VRE): a reason to isolate?

In recent years, an increase in invasive VRE infections has been reported worldwide, including Germany. The most common gene encoding resistance to glycopeptides is VanA, but predominant VanB clones are emerging. Although neither the incidence rates nor the exact routes of nosocomial transmission of VRE are well established, screening and strict infection control measures, e.g. single room contact isolation, use of personal protective clothing by hospital staff and intensified surface disinfection for colonized individuals, are implemented in many hospitals. At the same time, the impact of VRE infection on mortality remains unclear, with current evidence being weak and contradictory. In this short review, we aim to give an overview on the current basis of evidence on the clinical effectiveness of infection control measures intended to prevent transmission of VRE and to put these findings into a larger perspective that takes further factors, e.g. VRE-associated mortality and impact on patient care, into account.

Emergence of vancomycin-intermediate and -resistant Staphylococcus aureus among methicillin-resistant S. aureus isolated from clinical specimens in the northwest of Iran

OBJECTIVES

The aim of this study was to evaluate the frequency as well as the phenotypic and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) isolates from clinical specimens at three university teaching hospitals in Urmia, Northwest Iran, from 2012-2015.

METHODS

Following identification of the isolates, antibiotic susceptibility testing was performed. The presence of the mecA, vanA and pvl genes was evaluated, and staphylococcal cassette chromosome mec (SCCmec) typing was performed.

RESULTS

A total of 177 S. aureus isolates were collected from various clinical specimens. Antibiotic susceptibility testing revealed high resistance rates to penicillin (98.9%), followed by erythromycin (61.6%). A total of 95 isolates (53.7%) were confirmed as MRSA. Among the initially screened vancomycin-intermediate S. aureus (VISA) isolates, one isolate with a minimum inhibitory concentration (MIC) of 6μg/mL harboured the vanA gene. Eleven MRSA isolates (11.6%) were also VRSA. A majority (23/95; 24.2%) of MRSA were classified as SCCmec type III. Only 6 MRSA isolates (6.3%) harboured the pvl gene.

CONCLUSIONS

This study highlights the presence of MRSA along with VISA and VRSA in our setting. To our knowledge, this is the first report showing that a strain can be defined as VISA phenotypically and as VRSA by molecular analysis. Such a finding raises major concerns with regard to control measures and reliable laboratory tests for screening of resistant strains.

Clinical characteristics and treatment outcomes of vancomycin-resistant Enterococcus faecium bacteremia

BACKGROUND

Vancomycin-resistant Enterococcus faecium (VRE-fm) bacteremia causes significant mortality in hospitalized patients. We sought to investigate clinical characteristics, treatment outcomes, and microbiological eradication associated with VRE-fm bacteremia.

METHODS

A retrospective cohort study was conducted and included 210 adult patients admitted between January 1, 2011 and December 31, 2015.

RESULTS

The mean Pitt bacteremia score was 4.7. ICU stay (48.6%) and mechanical ventilation (46.2%) were common. Diabetes mellitus was the most common concomitant disease (43.3%), followed by malignancies, including hematologic malignancies (14.3%) and solid cancers (28.1%). The 14-day and 28-day mortality rates were 37.1% and 50.5%, respectively. Linezolid or daptomycin treatment for at least 10 days and higher Pitt bacteremia scores were independently associated with 14-day and 28-day mortality. Longer treatment duration of linezolid or daptomycin predicted microbiological eradication independently. Daptomycin-treated patients tended to have higher 14-day and 28-day mortality, and lower microbial eradication rates (20.8% versus 8.7%; 40.6% versus 26.1%; 14.1% versus 26.1%; respectively) than linezolid-treated patients, and cumulative survival rates at 14 and 28 days tended to be lower in patients who received low-dose daptomycin (<10 mg/kg/day) than that in those who received linezolid and high-dose daptomycin (≥10 mg/kg/day); however, the differences were not statistically significant.

CONCLUSION

Higher disease severity and inappropriate treatment were associated with increased mortality and longer treatment duration of linezolid or daptomycin was associated with microbial eradication for the patient with VRE-fm bacteremia.

Comparative genome analysis of multiple vancomycin-resistant Enterococcus faecium isolated from two fatal cases

Enterococcus faecium is both a commensal of the human intestinal tract and an opportunistic pathogen. The increasing incidence of enterococcal infections is mainly due to the ability of this organism to develop resistance to multiple antibiotics, including vancomycin. The aim of this study was to perform comparative genome analyses on four vancomycin-resistant Enterococcus faecium (VRE_fm) strains isolated from two fatal cases in a tertiary hospital in Malaysia. Two sequence types, ST80 and ST203, were identified which belong to the clinically important clonal complex (CC) 17. This is the first report on the emergence of ST80 strains in Malaysia. Three of the studied strains (VREr5, VREr6, VREr7) were each isolated from different body sites of a single patient (patient Y) and had different PFGE patterns. While VREr6 and VREr7 were phenotypically and genotypically similar, the initial isolate, VREr5, was found to be more similar to VRE2 isolated from another patient (patient X), in terms of the genome contents, sequence types and phylogenomic relationship. Both the clinical records and genome sequence data suggested that patient Y was infected by multiple strains from different clones and the strain that infected patient Y could have derived from the same clone from patient X. These multidrug resistant strains harbored a number of virulence genes such as the epa locus and pilus-associated genes which could enhance their persistence. Apart from that, a homolog of E. faecalis bee locus was identified in VREr5 which might be involved in biofilm formation. Overall, our comparative genomic analyses had provided insight into the genetic relatedness, as well as the virulence potential, of the four clinical strains.

Effect of chlorhexidine bathing in preventing infections and reducing skin burden and environmental contamination: A review of the literature

Chlorhexidine bathing is effective in reducing levels of pathogens on skin. In this review, we examine the evidence that chlorhexidine bathing can prevent colonization and infection with health care-associated pathogens and reduce dissemination to the environment and the hands of personnel. The importance of education and monitoring of compliance with bathing procedures is emphasized in order to optimize chlorhexidine bathing in clinical practice.

Exogenous endophthalmitis caused by Enterococcus casseliflavus: A case report and discussion regarding treatment of intraocular infection with vancomycin-resistant enterococci

Due to poor penetration of systemic or topical antibiotics into the vitreous chamber, treating endophthalmitis is challenging, especially in rare cases in which vancomycin-resistant enterococci are present. Caused by the unique mechanism of high-velocity water stream trauma, a case of exogenous endophthalmitis in a four-year-old-boy is discussed.

Endophthalmitis caused by enterococci is rare, and cases involving vancomycin-resistant enterococci are even more so. Due to the poor bioavailability of many antibiotics in the vitreous chamber, special considerations are required when choosing antibiotics to treat these infections. The authors report the first case of exogenous endophthalmitis caused by Enterococcus casseliflavus via the unique mechanism of high-velocity water stream trauma from a toy water gun.

A previously healthy four-year old boy presented with endophthalmitis of the left eye after injury from a water gun. Empirical treatment for endophthalmitis was started on presentation to the ophthalmologist. After the identification of the pathogen and a review of the literature, the antibiotic regimen was changed to include intravitreal ampicillin and amikacin with systemic linezolid.

Endophthalmitis caused by E casseliflavus and other vancomycin-resistant enterococci are challenging to treat. Rapid identification of vancomycin-resistant enterococcal endophthalmitis is important to guide appropriate antibiotic therapy. Systemic linezolid achieves excellent intravitreal concentrations, and should be used in combination with intravitreal and topical antibiotics.