Isolation and characterization of glycopeptide-resistant enterococci from hospitalized patients over a 30-month period

Molecular Analysis of Vancomycin-Resistant Enterococci Isolated from Regional Hospitals in Trinidad and Tobago

Geographic spread of vancomycin-resistant enterococci (VRE) clones in cities, countries, or even continents has been identified by molecular techniques. This study aimed at characterizing virulent genes and determining genetic relatedness of 45 VRE isolates from Trinidad and Tobago using molecular tools, including polymerase chain reaction, pulsed-field gel electrophoresis (PFGE), and Random Amplification Polymorphic DNA (RAPD). The majority (84%) of the isolates were Enterococcus faecium possessing vanA gene while the rest (16%) were Enterococcus faecalis possessing vanB. The esp gene was found in all 45 VRE isolates while hyl genes were found only in E. faecium species. The E. faecium species expressed five distinct PFGE patterns. The predominant clones with similar or common patterns belonged to clones one and three, and each had 11 (29%) of the VRE isolates. Plasmid content was identified in representative isolates from each clonal group. By contrast, the E. faecalis species had one PFGE pattern suggesting the presence of an occult and limited clonal spread. The emergence of VRE in the country seems to be related to intra/interhospital dissemination of an epidemic clone carrying the vanA element. Therefore, infection control measures will be warranted to prevent any potential outbreak and spread of VRE in the country.

Genotyping of vancomycin resistant enterococci in arak hospitals

BACKGROUND

Enterococcal species have emerged as important pathogens in Iran as well as throughout the world. With the increased use of vancomycin, Vancomycin-Resistant Enterococci (VRE) has become an important nosocomial pathogen.

OBJECTIVES

The aim of the present study was to determine the incidence and antimicrobial susceptibility pattern of VRE and also to determine the most important genes that cause resistance to vancomycin in clinical samples in Arak, Iran.

MATERIALS AND METHODS

In total, 200 enterococci samples were collected from clinical specimens of Arak hospitals. Enterococcal species were identified using standard biochemical tests. Antibiotic susceptibility was tested by the Clinical and Laboratory Standards Institute (CLSI) disk diffusion. Minimum Inhibitory Concentration (MICs) was determined by broth micro dilution. All of the VRE isolates were examined by PCR to detect the presence of VRE genes.

RESULTS

Disk diffusion agar showed that 96 strains (48%) were resistant to gentamicin, 89 (44.5%) to ciprofloxacin, 127 (63.5%) to erythromycin, 142 (71%) to tetracycline, 11 (5.5%) to teicoplanin, 32 (16%) to vancomycin, none to linezolid and 96 (48%) to co-trimoxazole. The MICs of the resistant isolates were as follows; 88 strains had MIC ≥ 32 μg/mL to vancomycin and 59 strains had MIC ≥ 32 μg/mL to teicoplanin. Molecular studies revealed that 59.09% of VRE contained VanA genes and 7.95% of VRE contained the VanB genes. None of the strains had vanC1 and vanC2/3 gene.

CONCLUSIONS

According to the results of this study, rates of vancomycin-resistance in enterococci, in Iran like other parts of the world, is increasing. Therefore accurate methods are required for identifying strains that possess resistance genes because many cases of hospital infections are caused by these strains.

Prevalence and antimicrobial resistance pattern of multidrug-resistant enterococci isolated from clinical specimens

PURPOSE

Vancomycin-resistant enterococci (VRE) pose an emerging problem in hospitals worldwide. The present study was undertaken to determine the occurrence, species prevalence, antibacterial resistance, and phenotypic and genetic characteristics of VRE isolated in Riyadh hospitals, KSA.

MATERIALS AND METHODS

Two hundred and six isolates of enterococcal species were obtained from clinical samples. The antibiotic susceptibility of isolates and minimum inhibitory concentration (MIC) tests for vancomycin and teicoplanin were determined. Molecular typing of VRE isolates was carried out by using pulsed field gel electrophoresis (PFGE) and the resistance genotype was determined by polymerase chain reaction (PCR).

RESULTS

VRE accounted for 3.9% of the isolates and were detected mostly in urine, wound and blood specimens isolated from ICU, internal medicine and surgical wards. All strains were identified to species level and were found to consist of E. faecalis (69.2%), E. faecium (11.3%), E. avium (2.1%), E. hirae (0.8%), E. casseliflavus (1.3%) and E. gallinarum (1.3%) species. According to the susceptibility data obtained, 8 (3.9%) out of 206 isolates were found to be VRE (MICs > 32 μg/ml). The vanA, vanB and vanC gene fragments of E. faecalis, E. faecium and E. gallinarum were amplified from isolates and were detected. PFGE patterns of the VRE isolates revealed homogenous patterns with dominant clone suggesting that the strains intrinsic resistance is independent.

CONCLUSIONS

This study shows an emergence of VRE along with increased rate of multidrug-resistant enterococci in the area of the study. Regular surveillance of antimicrobial susceptibilities should be done regularly and the risk factors should be determined.

Epidemiology and control of an outbreak of vancomycin-resistant enterococci in the intensive care units

PURPOSE

This study was aimed to describe a vancomycin-resistant enterococci (VRE) outbreak across three intensive care units (ICUs) of a Korean hospital from September 2006 to January 2007 and the subsequent control strategies.

MATERIALS AND METHODS

We simultaneously implemented multifaceted interventions to control the outbreak, including establishing a VRE cohort ward, active rectal surveillance cultures, daily extensive cleaning of environmental surfaces and environmental cultures, antibiotic restriction, and education of hospital staff. We measured weekly VRE prevalence and rectal acquisition rates and characterized the VRE isolates by polymerase chain reaction (PCR) of the vanA gene and Sma1-pulsed-field gel electrophoresis (PFGE).

RESULTS

During the outbreak, a total of 50 patients infected with VRE were identified by clinical and surveillance cultures, and 46 had vancomycin-resistant Enterococcus faecium (VREF). PFGE analysis of VREF isolates from initial two months disclosed 6 types and clusters of two major types. The outbreak was terminated 5 months after implementation of the interventions: The weekly prevalence rate decreased from 9.1/100 patients-day in September 2006 to 0.6/100 by the end of January 2007, and the rectal acquisition rates also dropped from 6.9/100 to 0/100 patients-day.

CONCLUSION

Our study suggests that an aggressive multifaceted control strategy is a rapid, effective approach for controlling a VRE outbreak.

Enterococci and streptococci

Besides Staphylococcus aureus, other Gram-positive bacteria have become multidrug-resistant and cause therapeutic problems, particularly amongst hospitalised patients. The acquisition of vancomycin resistance by strains of Enterococcus faecium and Enterococcus faecalis is of particular concern and has resulted in treatment failures. Some of the infections caused by these bacteria do respond to treatment with new antibiotics that have been released in the last few years, however more options are required as not all enterococci are inherently susceptible and resistance is beginning to emerge amongst those that were susceptible. Resistance to commonly used antibiotics is also emerging in Streptococcus spp., particularly to the tetracyclines and macrolides. In both genera, multiresistant strains spread between patients and between hospitals. In the laboratory, these bacteria show considerable susceptibility to tigecycline, with little propensity to develop resistance, indicating that tigecycline could assume an important role in controlling infections caused by these Gram-positive bacteria.

Does vancomycin prescribing intervention affect vancomycin-resistant enterococcus infection and colonization in hospitals? A systematic review

Background

Vancomycin resistant enterococcus (VRE) is a major cause of nosocomial infections in the United States and may be associated with greater morbidity, mortality, and healthcare costs than vancomycin-susceptible enterococcus. Current guidelines for the control of VRE include prudent use of vancomycin. While vancomycin exposure appears to be a risk factor for VRE acquisition in individual patients, the effect of vancomycin usage at the population level is not known. We conducted a systematic review to determine the impact of reducing vancomycin use through prescribing interventions on the prevalence and incidence of VRE colonization and infection in hospitals within the United States.

Methods

To identify relevant studies, we searched three electronic databases, and hand searched selected journals. Thirteen studies from 12 articles met our inclusion criteria. Data were extracted and summarized for study setting, design, patient characteristics, types of intervention(s), and outcome measures. The relative risk, 95% confidence interval, and p-value associated with change in VRE acquisition pre- and post-vancomycin prescription interventions were calculated and compared. Heterogeneity in study results was formally explored by stratified analysis.

Results

No randomized clinical trials on this topic were found. Each of the 13 included studies used a quasi-experimental design of low hierarchy. Seven of the 13 studies reported statistically significant reductions in VRE acquisition following interventions, three studies reported no significant change, and three studies reported increases in VRE acquisition, one of which reported statistical significance. Results ranged from a reduction of 82.5% to an increase of 475%. Studies of specific wards, which included sicker patients, were more likely to report positive results than studies of an entire hospital including general inpatients (Fisher's exact test 0.029). The type of intervention, endemicity status, type of study design, and the duration of intervention were not found to significantly modify the results. Among the six studies that implemented vancomycin reduction strategies as the sole intervention, two of six (33%) found a significant reduction in VRE colonization and/or infection. In contrast, among studies implementing additional VRE control measures, five of seven (71%) reported a significant reduction.

Conclusion

It was not possible to conclusively determine a potential role for vancomycin usage reductions in controlling VRE colonization and infection in hospitals in the United States. The effectiveness of such interventions and their sustainability remains poorly defined because of the heterogeneity and quality of studies. Future research using high-quality study designs and implementing vancomycin as the sole intervention are needed to answer this question.

Thoracic organ transplantation may not increase the risk of bacterial transmission in intensive care units

A transmission study was performed to investigate whether organ recipients suffer more transmissions of bacteria than do non-transplanted patients. We chose enterococci for molecular typing because of their high prevalence, transmissibility, and predominance in causing nosocomial infections. Patients staying longer than 48h in a cardiovascular surgery intensive care unit (ICU) were included in our one-year prospective cohort study. Enterococci identified from clinical or surveillance isolates were collected and typed by PFGE. Episodes of transmission were defined by the identification of genetically indistinguishable isolates in two or more patients who were treated during overlapping intervals or within a 9-day window period in the same ICU. Risk factor analysis was performed. Out of 585 patients microbiological specimens were cultured from 336 patients. From 187 of these, enterococci were isolated. From 81 patients 186 enterococci isolates were typed. Out of 105 different enterococci strains, 16 cluster strains were detected and 30 episodes of transmissions occurred. The transmission rate was 7.8 per 1000 patient days. No significant association was found between "being cluster member "and "patient organ transplanted" (OR 1.5, CI(95%) 0.58; 3.98, p=0.38) or "patient treated in a single-room only" (OR 1.06, CI(95%) 0.36;3, 12, p=0.91), respectively. In contrast, "being cluster member" was associated with a prolonged length of stay (OR per additional days of stay 1.05, CI(95%) 1.01-1.09, p<0.01). Thoracic organ transplantation was not found to be a risk factor for bacterial transmission, but transmission was associated with a prolonged length of stay.

Abietanes from Plectranthus grandidentatus and P. hereroensis against methicillin- and vancomycin-resistant bacteria

The antimicrobial activity of 10 natural abietanes isolated from Plectranthus grandidentatus and P. hereroensis acetonic extract was evaluated against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VRE). The results revealed that the most active diterpenes were coleon U (1), 7alpha-acetoxy-6beta-hydroxyroyleanone (2) and horminone (3). Minimum inhibitory concentration (MIC) values ranging 0.98-15.63 microg/ml were obtained for MRSA clinical strains, and MIC values of 15.63 and 31.25 microg/ml were obtained for VRE clinical strains. Some structure-activity relationships are emphasized.

Drug resistance in fecal enterococci in Hong Kong

Our purpose was to estimate the rate of carriage of vancomycin-resistant enterococci (VRE) in hospitalized patients in a district hospital and in healthy subjects in the community in Hong Kong. Rectal swabs were collected from all patients admitted to the intensive care unit, and stool specimens were collected from all patients presenting with suspected antibiotic-associated diarrhea over a 2-month period. Stool specimens were also collected from healthy subjects in the community. Specimens were enriched and cultured on selective media for the isolation of enterococci. All isolates were identified, and their minimum inhibitory concentration for vancomycin was determined. Susceptibility to other antibiotics was investigated. Samples yielded 125 isolates of enterococci, the majority of isolates being Enterococcus faecalis (75) and E. faecium (35). Nine of 11 strains of E. gallinarum and 2 of 2 strains of E. casseliflavus isolated from hospitalized patients were intermediately resistant to vancomycin, but no strains highly resistant to vancomycin were isolated. Resistance to other drugs, including the fluoroquinolones, was present, and a high-level resistance to gentamicin and streptomycin was found in 37% and 46% of strains, respectively. Colonization with VRE remains low in Hong Kong. This result is supported by the low level of isolation of VRE from infections in the region and may be attributable to low levels of vancomycin use. High-level aminoglycoside resistance and fluoroquinolone resistance are common, and continued monitoring for VRE is suggested.

Methods used for the isolation, enumeration, characterisation and identification of Enterococcus spp

This paper reviews the methodology applied for the identification and characterisation of enterococci and covers phenotypic, genotypic and phylogenetic techniques. Although conventional phenotypic typing schemes are useful for rapid and simple identification of enterococcal species for routine applications, other methods like standardised sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), multilocus enzyme electrophoresis (MLEE), antimicrobial susceptibility testing, serotyping, pyrolysis mass spectrometry (pyMS) and vibrational spectroscopic methods allow a more in-depth characterisation of enterococci. Many of the recently described enterococcal species exhibit deviations from hitherto so-called classical enterococci with regard to their phenotypical properties. Therefore, genotypic methods have to be used to clarify their possible assignment to the genus Enterococcus. In this review, special emphasis is given on recently developed polymerase chain reaction (PCR)-based typing methods such as random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), specific and random amplification (SARA) and modifications of PCR-ribotyping as well as pulsed-field gel electrophoresis (PFGE) and partial sequence analysis. The use of PCR and probes for genus and species identification of enterococci is also considered like the application of sequence data of conserved DNA regions (e.g., ribosomal ribonucleic acid (rRNA) genes) in the case of species identification.

SHEA guideline for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus aureus and enterococcus

BACKGROUND

Infection control programs were created three decades ago to control antibiotic-resistant healthcare-associated infections, but there has been little evidence of control in most facilities. After long, steady increases of MRSA and VRE infections in NNIS System hospitals, the Society for Healthcare Epidemiology of America (SHEA) Board of Directors made reducing antibiotic-resistant infections a strategic SHEA goal in January 2000. After 2 more years without improvement, a SHEA task force was appointed to draft this evidence-based guideline on preventing nosocomial transmission of such pathogens, focusing on the two considered most out of control: MRSA and VRE.

METHODS

Medline searches were conducted spanning 1966 to 2002. Pertinent abstracts of unpublished studies providing sufficient data were included.

RESULTS

Frequent antibiotic therapy in healthcare settings provides a selective advantage for resistant flora, but patients with MRSA or VRE usually acquire it via spread. The CDC has long-recommended contact precautions for patients colonized or infected with such pathogens. Most facilities have required this as policy, but have not actively identified colonized patients with surveillance cultures, leaving most colonized patients undetected and unisolated. Many studies have shown control of endemic and/or epidemic MRSA and VRE infections using surveillance cultures and contact precautions, demonstrating consistency of evidence, high strength of association, reversibility, a dose gradient, and specificity for control with this approach. Adjunctive control measures are also discussed.

CONCLUSION

Active surveillance cultures are essential to identify the reservoir for spread of MRSA and VRE infections and make control possible using the CDC's long-recommended contact precautions.

Species prevalence and antibacterial resistance of enterococci isolated in Kuwait hospitals

This study investigated the species prevalence and antibacterial resistance among enterococci isolated in Kuwait hospitals. They consisted of 415 isolates of Enterococcus faecalis (85.3 %), Enterococcus faecium (7.7 %), Enterococcus casseliflavus (4.0 %), Enterococcus avium (1.2 %), Enterococcus durans (1.0 %), Enterococcus gallinarium (0.5 %) and Enterococcus bovis (0.2 %) isolated from urine (36.6 %), blood (10.4 %), wound swabs (11.0 %), stool samples (12.0 %), high vaginal swabs (9.0 %), endocervical swabs (3.0 %) and miscellaneous sources (18.0 %). All of them were susceptible to linezolid. Fifty-two (12.5 %) isolates were ampicillin resistant but none of them produced beta-lactamase. They were resistant to erythromycin (63.3 %), tetracycline (60.5 %), ciprofloxacin (40.0 %), chloramphenicol (28.0 %), vancomycin (2.6 %), and teicoplanin (2.6 %). Fourteen, 19 and 20 % of them expressed high-level resistance to gentamicin, kanamycin and streptomycin, respectively. All of the vancomycin-resistant strains carried the vanA phenotype and genotype. There was no evidence of clonal spread of the vancomycin-resistant isolates.

Epidemiology of vancomycin-resistant Enterococcus faecium under a selective isolation policy at an urban county hospital

BACKGROUND

We report our experience in a county hospital with the use of selective contact isolation for patients with vancomycin-resistant Enterococcus faecium (VREF). About 12% of patients with VREF are isolated for reasons such as draining wounds and uncontrolled diarrhea.

METHODS

Passive surveillance identified all inpatients (181) from 1995 to 1999 with cultures positive for VREF. Data were collected via electronic databases and from prospectively maintained infection control records. Isolates were typed with use of pulsed-field gel electrophoresis.

RESULTS

Nearly all patients (175/181) with VREF had been admitted at least 48 hours or had a history of previous hospitalization. Most patients (69%) had urine cultures positive for VREF without blood cultures positive for the organism. Only 12 of 127 (9.%) patients with complete data had VREF infection on the basis of receiving treatment and/or having more than 1 blood culture positive for VREF. After VREF became endemic, statistically significant increased prevalence was not detected via surveillance of clinical cultures nor sequential point-prevalence studies. Two major genotypes carrying vanB resistance genes were identified and persisted throughout the period studied. VREF persisted in individual patients up to 46 months.

CONCLUSIONS

The number of VREF infections in this facility has been low, despite appreciable colonization, for an extended period during which selective isolation was used.

Antibiotic resistance of enterococci isolated at a teaching hospital in Kuwait

Enterococci isolated in a teaching hospital were studied for their resistance to different antibiotics. Minimum inhibitory concentrations to high-level aminoglycosides and glycopeptide antibiotics were determined by agar dilution and E-test methods respectively. Genes encoding aminoglycoside-modifying enzymes were detected by the polymerase chain reaction (PCR). 195 enterococci were isolated from urines (54.3%), wounds (16.4%), blood (10.2%), and miscellaneous sources (18.9%). They consisted of E. faecalis (88.7%), E. faecium (9.2%), E. casseliflavus (1.5%) and E. bovis (0.5%). None of the enterococci produced penicillinase but 3.5% of them were resistant to ampicillin. They were also resistant to high-level gentamicin (15.9%), kanamycin (22.0%), streptomycin (21.0%), tetracycline (65.1%), erythromycin (62.6%), ciprofloxacin (36.1%), chloramphenicol (26.1%), vancomycin (3.0%) and teicoplanin (2.0%). Most of the high-level aminoglycoside-resistant isolates contained genes coding the bifunctional aminoglycoside modifying enzymes AAC(6')-APH(2"), APH(3') and ANT(6') but not the ANT(4') enzyme. The results demonstrated a low prevalence of vancomycin resistance among Enterococci in this hospital.

Insights into the epidemiology and control of infection with vancomycin-resistant enterococci

Despite control efforts, the incidence of nosocomial infections due to vancomycin-resistant enterococci (VRE) continues to increase in the United States. VRE are thought to spread primarily by cross-contamination. Recent molecular epidemiologic studies have refined our understanding of this phenomenon. If VRE are not controlled soon after introduction into a hospital, sporadic cases may evolve into a monoclonal outbreak, which may then evolve to polyclonal endemicity. An intervention that is effective in containing VRE in one setting may be ineffective in another. Control of VRE where they are endemic is particularly challenging. Although eradication of endemic VRE may not be possible, aggressive, multifaceted programs have been successful in diminishing the problem. A mathematical model of transmission of VRE and the effect of infection control measures in settings where they are endemic has been reported. The use of such a model may allow more precise determination of the impact of control strategies in the future.

Identification and characterization of vanB2 glycopeptide resistance elements in enterococci isolated in Scotland

Thirty-two vanB glycopeptide-resistant enterococci (28 Enterococcus faecium and 4 Enterococcus faecalis) were collected from hospitalized patients in Glasgow, Edinburgh, Dundee, and Aberdeen, Scotland, and the vanB element in each was compared to vanB1 of E. faecalis strain ATCC 51299. HhaI digestion of PCR fragments of the vanB ligase gene was used to identify vanB subtypes. All E. faecium isolates were vanB2, and all E. faecalis isolates were vanB1. Restriction fragment length polymorphism analysis of a 5,180-bp vanS(B)-vanX(B) long-PCR fragment of the vanB cluster showed the loss of HaeII restriction sites in vanS(B), vanW, and vanX(B) in strains containing a vanB2 ligase gene. Partial sequences of genes in the vanB2 cluster for two genomically distinct Scottish isolates were >99.8% identical to each other. vanS(B2), vanX(B2), and vanB2 sequences differed at the nucleotide level from those of vanS(B), vanX(B), and vanB by 4.2, 4.6, and 4.8%, respectively. The vanB2 resistance element appears to be widespread among VanB glycopeptide-resistant E. faecium strains isolated in Scottish hospitals.