Vancomycin-resistant E. Faecium Research Articles

National surveillance on vancomycin-resistant Enterococcus faecium in Taiwan: emergence and widespread of ST414 and a Tn1546-like element with simultaneous insertion of IS1251-like and IS1678.

Cases of bacteremia caused by vancomycin-resistant E. faecium (VRE-fm) increased significantly in Taiwan. The present multicenter surveillance study was performed to reveal the associated epidemiological characteristics. In 2012, 134 non-repetitive VRE-fm isolates were prospectively collected from 12 hospitals in Taiwan. Antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and analysis of van genes and Tn1546 structures were investigated. Two isolates carried vanB genes, while all the remaining isolates carried vanA genes. Three isolates demonstrated a specific vanA genotype - vanB phenotype. Nine (6.7%) isolates demonstrated tigecycline resistance, and all were susceptible to daptomycin and linezolid. Molecular typing revealed 58 pulsotypes and 13 sequence types (STs), all belonged to three major lineages 17, 18, and 78. The most frequent STs were ST17 (n = 48, 35.8%), ST414 (n = 22, 16.4%), and ST78 (n = 16, 11.9%). Among the vanA harboring isolates, eight structure types of the Tn1546-like element were demonstrated. Type I (a partial deletion in the orf1 and insertion of IS1251-like between the vanS - vanH genes) and Type II (Type I with an additional insertion of IS1678 between orf2 - vanS genes) were the most predominant, consisted of 60 (45.5%) and 62 (47.0%) isolates, respectively. The increase of VRE-fm bacteremia in Taiwan may be associated with the inter- and intra-hospital spread of some major STs and horizontal transfer of vanA genes mostly carried on two efficient Tn1546-like elements. The prevailing ST414 and widespread of the Type II Tn1546-like elements are an emerging problem that requires continuous monitoring.

Application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry in the screening of vanA-positive Enterococcus faecium.

In order to evaluate a rapid matrix-assisted laser desorption ionization-time of flight mass spectrometry (MAIDI-TOF MS) assay in screening vancomycin-resistant Enterococcus faecium, a total of 150 E. faecium clinical strains were studied, including 60 vancomycin-resistant E. faecium (VREF) isolates and 90 vancomycin-susceptible (VSEF) strains. Vancomycin resistance genes were detected by sequencing. E. faecium were identified by MALDI-TOF MS. A genetic algorithm model with ClinProTools software was generated using spectra of 30 VREF isolates and 30 VSEF isolates. Using this model, 90 test isolates were discriminated between VREF and VSEF. The results showed that all sixty VREF isolates carried the vanA gene. The performance of VREF detection by the genetic algorithm model of MALDI-TOF MS compared to the sequencing method was sensitivity = 80%, specificity = 90%, false positive rate =10%, false negative rate =10%, positive predictive value = 80%, negative predictive value= 90%. MALDI-TOF MS can be used as a screening test for discrimination between vanA-positive E. faecium and vanA-negative E. faecium.

Increase in the Prevalence of Carbapenem-Resistant Acinetobacter Isolates and Ampicillin-Resistant Non-Typhoidal Salmonella Species in Korea: A KONSAR Study Conducted in 2011.

BackgroundAntimicrobial surveillance is important for providing an up-to-date understanding of the epidemiology of antimicrobial resistance and for creating a forum for rational drug development. In this study, we analyzed antimicrobial test data generated in 2011 by hospitals and commercial laboratories participating in the Korean Nationwide Surveillance of Antimicrobial Resistance program (KONSAR).Materials and MethodsData on the results of susceptibility tests conducted in 32 hospitals and two commercial laboratories were analyzed. Data on isolates from patients admitted to an intensive care unit (ICU) and those admitted to other wards were compared. Intermediate susceptibility was not analyzed and duplicate isolates were excluded.ResultsEscherichia coli was the most prevalent organism identified in both the hospital and commercial laboratories. Among the hospital isolates, methicillin-resistant Staphylococcus aureus (MRSA), penicillin G-non-susceptible Streptococcus pneumoniae, and ampicillin-resistant Enterococcus faecium remained as prevalent as they were in 2009. The proportion of vancomycin-resistant E. faecium (VR-EFM) slightly decreased from 29% in 2009 to 23% in 2011. Resistance rates of Klebsiella pneumoniae to ceftazidime, cefoxitin, fluoroquinolone, and amikacin were 24%, 14%, 27%, and 8%, respectively. Resistance rates of Pseudomonas aeruginosa to fluoroquinolone, ceftazidime, imipenem, and amikacin were 33%, 20%, 22%, and 16%, respectively, whereas those of Acinetobacter spp. resistance were 71%, 66%, 64, and 51%, respectively. The prevalence of oxyimino-cephalosporin-resistant E. coli and K. pneumoniae, carbapenem-resistant Acinetobacter spp. and P. aeruginosa, MRSA, and VR-EFM among ICU isolates was higher than those among non-ICU isolates. Extended-spectrum β-lactamase-producing E. coli and K. pneumoniae, imipenem-resistant P. aeruginosa, and VR-EFM were more prevalent among isolates from commercial laboratories than those from hospitals. Resistance rates of K. pneumoniae to ceftazidime and amikacin decreased from 32% and 24% in 2005 to 24% and 8% in 2011, respectively. The resistance rate of P. aeruginosa to amikacin decreased from 22% in 2005 to 16% in 2011. The proportion of imipenem-resistant Acinetobacter spp. increased from 16% in 2005 to 64% in 2011.ConclusionsThe prevalence of MRSA, penicillin G-non-susceptible S. pneumoniae, and ampicillin-resistant E. faecium among clinical isolates tested in laboratories remained high. Multidrug resistance was more prevalent among isolates from ICUs. The prevalence of ceftazidime-resistant and amikacin-resistant K. pneumoniae and amikacin-resistant P. aeruginosa decreased after 2005, while the prevalence of imipenem-resistant Acinetobacter spp. increased.

Could a Phosphotransferase System Provide the Means to Control Outbreaks of Enterococcus faecium Infection?

The epidemiology of enterococcal infections has changed dramatically over the past 100 years [1]. Until relatively recently, the vast majority were caused by Enterococcus faecalis and were acquired in the community; then, during the 1970s– 1980s, the percentage of nosocomial infections due to E. faecalis tripled [2,3],an increase temporally associated with increasing use of third-generation cephalosporins. In the United States, an increase in the proportion of nosocomial infections caused by Enterococcus faecium was observed in the 1980s [4, 5], and by 2006–2007, a Centers for Disease Control survey of healthcare-associated infections found that approximately 38% of clinical enterococcal isolates identified to the species level were E. faecium [6]. This increase was blamed on the acquisition of vancomycin resistance by E. faecium (which seldom occurred in E. faecalis) and the increasing use of vancomycin in hospitalized patients. However, the epidemiology of vancomycin-resistant E. faecium (VREfm) presented a quandary: at the time, VREfm was alreadyacommon cause of US healthcare-associated infections, such organisms were not found in the community [7].Yet, concurrently, VREfm was rare as a cause of infection in the European Union but were commonly found in feces of food animals in Europe, in products derived from these animals, in feces of individuals handling them, and even in feces of

Isolation and Structural Elucidation of Armeniaspirols A–C: Potent Antibiotics against Gram‐Positive Pathogens

In an antibiotic lead discovery program, the known strain Streptomyces armeniacus DSM19369 has been found to produce three new natural products when cultivated on a malt-containing medium. The challenging structural elucidation of the isolated compounds was achieved by using three independent methods, that is, chemical degradation followed by NMR spectroscopy, a computer-assisted structure prediction algorithm, and X-ray crystallography. The compounds, named armeniaspirol A-C (2-4), exhibit a compact, hitherto unprecedented chlorinated spiro[4.4]non-8-ene scaffold. Labeling experiments with [1-(13)C] acetate, [1,2-(13)C2] acetate, and [U-(13)C] proline suggest a biosynthesis through a rare two-chain mechanism. Armeniaspirols displayed moderate to high in vitro activities against gram-positive pathogens such as methicillin-resistant S. aureus (MRSA) or vancomycin resistant E. faecium (VRE). As analogue 2 was active in vivo in an MRSA sepsis model, and showed no development of resistance in a serial passaging experiment, it represents a new antibiotic lead structure.

Intestinal Colonization with Enterococcus faecium Does Not Influence Pulmonary Defense against Pseudomonas aeruginosa in Mice

BackgroundEnterococci, and especially multiresistant Enterococcus faecium, are increasingly found colonizing hospitalized patients. This increased prevalence of colonization is not only associated with an increased prevalence of infections caused by enterococci, but also by infections with other nosocomial pathogens. In this study we investigated the causality of this observed relationship, by determining the influence of intestinal colonization with E. faecium on pulmonary defense against Pseudomonas aeruginosa.Methodology/Principal FindingsThree groups of mice were tested; 2 groups of mice were pre-treated with vancomycin, of which one group was subsequently treated by oral gavage of vancomycin-resistant E. faecium (VRE). The third group did not receive any pre-treatment. P. aeruginosa pneumonia was induced in all mice. Vancomycin treatment resulted in intestinal gram-negative bacterial overgrowth and VRE treatment resulted in colonization throughout the intestines. All 3 groups of mice were able to clear P. aeruginosa from the lungs and circulation, with comparable lung cytokine responses and lung damage. Mice treated with vancomycin without VRE colonization displayed modestly increased plasma levels of TNF-α and IL-10.ConclusionOvergrowth of E. faecium and/or gram-negative bacteria does not impact importantly on pulmonary defense against P. aeruginosa pneumonia.

A Stereoselective Synthesis of C26-C36 Fragment of Arenicolide A

Scheme 2. Synthesis of C26-C36 Fragment (4). (a) n-Bu2BOTf (1.5 eq), Et3N (1.6 eq), butyraldehyde (2.0 eq), CH2Cl2, ‐78 C, 4 hr, 96%. (b) TBSOTf (1.2 eq), 2,6-lutidine (2.0 eq), CH2Cl2, ‒78 C, 3 hr, 84%. (c) LiBH4 (1.12 eq), water (1.12 eq), ether, rt, 45 min, 94%. (d) (COCl)2 (2.5 eq), DMSO (4.5 eq), Et3N (7.5 eq), CH2Cl2, ‒78 C, 1.5 hr, 91%. (e) Ph3P=C(Me)CO2Et (2.5 eq), benzene, reflux, overnight, 92%. (f) DIBAL (5.0 eq), CH2Cl2, ‒78 C, 2 hr, 94%. (g) mCPBA (1.5 eq), K2HPO4 (3.0 eq), CH2Cl2, rt, 18 hr, 72%. (h) (COCl)2 (2.0 eq), DMSO (4.0 eq), Et3N (5.0 eq), CH2Cl2, ‒78 C, 40 min, 88%. (i) (-)Ipc2BOMe (1.2 eq), allylmagnesium bromide (2.0 eq), ether, ‒100 C, 3 hr, 67%. (j) TBSOTf (1.5 eq), 2,6-lutidine (2.0 eq), CH2Cl2, ‒78 C, 30 min, 88%. Recently, arenicolides A (1) and B (2) were isolated from the large-scale fermentation of the S. arenicola strain CNR005 and its relative stereochemical relationship except C-12, C-30, and C-31 chiral centers was proposed by H NMR, C NMR, Mass, IR, UV, CD, chemical degradation methods. Arenicolides A (1) and B (2) are 26-membered macrolides with three conjugated dienes and nine chiral centers in the ring. There is one side chain which comprises the C-26 ~ C-36 carbon chain with five consecutive chiral centers. Arenicolide A (1) also showed moderate anti-cancer activity toward the human colon adenocarcinoma cell line HCT-116 (IC50; 30 μg/ mL) and three cell lines in the National Cancer Institute, and no activity against antimicrobial assay using methicillinresistant S. aureus (MRSA) and vancomycinresistant E. faecium (VREF).

Nationwide surveillance in Taiwan of the in-vitro activity of tigecycline against clinical isolates of Gram-positive cocci

Tigecycline In-vitro Surveillance in Taiwan (TIST), initiated in 2006, is a nationwide surveillance programme designed to monitor longitudinally the in-vitro activity of tigecycline against commonly encountered resistant bacteria in Taiwan. This study, part of TIST-2006 study, aimed to compare the in-vitro activity of tigecycline against clinical isolates of Gram-positive bacteria. A total of 805 isolates of Gram-positive bacteria were collected from patients treated at 20 teaching hospitals. Minimum inhibitory concentrations (MICs) of tigecycline for these isolates were determined by the broth microdilution method according to the guidelines of the Clinical and Laboratory Standards Institute, and by the Etest as per the manufacturer's instructions. Susceptibility results were interpreted by the MIC criteria recommended by the US FDA. Agreement between the two methods was low: 80.7% for methicillin-resistant Staphylococcus aureus (MRSA), 27.2% for Streptococcus pneumoniae, 22.8% for other Streptococcus spp., and 30.8% for vancomycin-resistant E. faecium (VRE). There were no very major or major errors noted. Tigecycline exhibited excellent in-vitro activity against Gram-positive cocci, including MRSA, VRE, S. pneumoniae and other Streptococcus spp. isolates in Taiwan. Correlation between MIC values determined using the broth microdilution and Etest methods for these organisms was poor.

Emergence of CC17Enterococcus faecium: from commensal to hospital-adapted pathogen

For many years, Enterococcus faecium was considered to be a commensal of the digestive tract, which only sporadically caused opportunistic infections in severely ill patients. Over the last two decades, vancomycin-resistant E. faecium (VREF) has emerged worldwide as an important cause of nosocomial infections, especially in immunocompromised patients. The global Vancomycin-resistant enterococci (VRE) epidemic was preceded by the emergence of ampicillin-resistant E. faecium (AREfm) in the United States in the early 1980s, followed by the rapid emergence of VRE in the 1990s. A similar increase of VRE may occur in countries with still low levels of VRE in hospitals (such as The Netherlands), but increasing incidence of AREfm infections. Molecular epidemiological studies of both human- and animal-derived E. faecium isolates using multilocus sequence typing revealed the existence of host-specific genogroups, including a specific genetic lineage designated CC17, associated with hospital-related isolates. These strains were characterized by ampicillin and quinolone resistance. In addition, the majority of these CC17 isolates contain over hundred hospital-clade-specific genes, including mobile elements, phage genes and plasmid sequences, hypothetical and membrane proteins and antibiotic and regulatory genes and a putative pathogenicity island including the esp gene.

Antimicrobial Resistance and Multilocus Sequence Typing of Vancomycin-Resistant Enterococcus faecium Isolated from Clinical Specimens

A total of 58 vancomycin-resistant E. faecium (VREF) was isolated from 3 hospitals located in Daegu, Korea. The VREF isolates were evaluated for the antimicrobial susceptibility pattern and resistance determinants against vancomcin, aminoglycosides, and macrolides. The multilocus sequence types (MLST) were determined to characterize the clonal diversity of the VREF isolates. The VREF isolates were highly resistance to teicoplanin, erythromycin, ciprofloxacin, gentamicin, and streptomycin, whereas quinupristin-dalfopristin and linezolid were the most susceptible drugs. All isolates carried the vanA gene. The aac6'-aph2 (n=53) and aadE (n=27) genes were detected in the high-level aminoglycoside resistant (HLAR) isolates. The aac6'-aph2 gene was located in the conjugally transferable plasmids. The ermB and ermA genes were detected in the 54 and 3 VREF isolates, respectively. The VREF isolates showed 11 different sequence types (ST). The VREF isolates belonging to ST192 was the most prevalent (n=19), but detected in one hospital, whereas the isolates belonging to ST203 (n=11) were detected in 3 hospitals. These results suggest that the VREF isolates resistant to aminoglycosides and erythromycin are originated from different clones and specific VREF clones are spread in the study hospitals.

Vancomycin-resistant Enterococci, Mexico City

Vancomycin-resistant Enterococci, Mexico City

Ecological replacement of Enterococcus faecalis by multiresistant clonal complex 17 Enterococcus faecium

The proportion of enterococcal infections caused by ampicillin-resistant Enterococcus faecium (AREfm) in a European hospital increased from 2% in 1994 to 32% in 2005, with prevalence rates of AREfm endemicity of up to 35% in at least six hospital wards. Diabetes mellitus, three or more admissions in the preceding year, and use of beta-lactams and fluoroquinolones, were all associated with AREfm colonisation. Of 217 AREfm isolates that were genotyped, 97% belonged to clonal complex 17 (CC17). This ecological change mimics events preceding the emergence of vancomycin-resistant E. faecium (VREF) in the USA and may presage the emergence of CC17 VREF in European hospitals.

Vancomycin-resistantEnterococcus faeciumClone in Swine, Europe

To the Editor: The use of antimicrobial agents for growth promotion (AGP) in food-producing animals has been extensively debated because of the risk of establishing a reservoir of antimicrobial resistance genes or antimicrobial-resistant organisms of potential relevance for human health. This concern has motivated the progressive ban of the use of different AGP in the European Union, which began in 1997 with avoparcin and will end in 2006 (1). Worldwide trade of living animals for food production or breeding and of meat products enables multidrug-resistant pathogens to spread across national borders. Intercontinental dissemination of antimicrobial-resistant bacteria associated with food animals has been described for particular clones such as Salmonella enterica Typhimurium DT104 or Escherichia coli O157:H7 and for transferable genetic elements such as the genomic island SG1 or the streptococcal plasmid pRE25 (2). Vancomycin-resistant enterococci (VRE) in European farms were initially associated with the intensive use of avoparcin; however, the persistence of VRE in food animal environments after years of avoparcin withdrawal indicates that coselection by further antimicrobial or other agents, increased fitness of strains, and mobile genetic elements cannot be ruled out (1–3). A specific clone was recently detected among vancomycin-resistant E. faecium (VREF) isolated from different swine farms in Denmark and Switzerland and from a healthy Danish woman without antimicrobial drug exposure who ate pork, chicken, and beef (4,5). Since Portugal and Spain maintain commercial trade of food-producing swine (living or meat products) between them and with other European countries, including Denmark (http://www.dgv.min-agricultura.pt/dgv.nsf), we investigated a possible relationship among VREF swine fecal isolates from Portugal and Spain and compared these isolates with the Swiss/Danish clone. We studied 3 VREF from a Figueira da Foz slaughterhouse in central Portugal (1997–1998) and 3 VREF isolates from 3 Spanish slaughterhouses in Valencia, Lugo, and Murcia in eastern, northern, and southern Spain, respectively (1998–2000). These isolates were recovered in the course of previous surveillance studies (C. Novais/I. Herrero, unpub data). Antimicrobial susceptibility was tested for 13 antimicrobial agents by using the agar dilution method (6). Clonal relationships were analyzed by pulsed-field gel electrophoresis (PFGE) and characterization of pur-K alleles by amplification and further sequencing (6,7; http://efaecium.mlst.net). Species identification, genes coding for antimicrobial resistance genes or for putative virulence traits, and the backbone structure of Tn1546 were analyzed by polymerase chain reaction followed by sequencing when necessary (6,8). Broth and filter mating were performed by using E. faecium GE1 as recipient strain (6). Following criteria published elsewhere (6), the VREF isolates studied were considered a single clone (0–4 bands difference by PFGE). Some vancomycin-susceptible E. faecium swine isolates (VSEF) from Spain and Switzerland showed an SmaI-PFGE pattern closely related to that of VREF isolates (data not shown [4]; ). Representative VREF of each country harbored the allele 9 of the housekeeping gene purK, previously found among E. faecium isolates from swine and healthy persons (7). All VREF isolates were resistant to glycopeptides (vanA), erythromycin [erm(B)], and tetracycline. Two Spanish isolates were also highly resistant to streptomycin and kanamycin [aph(3´)-IIIa] (Table). All VREF isolates tested carried a Tn1546 type D, previously found in isolates from food-producing animals (8). This element showed alterations in orf1 and a G-T point mutation in the position 8234 at vanX. Transfer of vancomycin resistance was detected for the Swiss (4), Spanish, and Portuguese isolates and was associated with erythromycin resistance in all cases. Tetracycline resistance was also transferable in the Spanish strains. No virulence traits were detected. Table Features of vancomycin-resistant Enterococcus faecium swine isolates from European countries* We describe the simultaneous occurrence of a VREF strain among swine in 4 distant European countries for at least a 4-year period. Tn1546 type D has been largely described in European swine isolates, which indicates stability of this particular type among the high diversity of Tn1546 described to date (8). The finding of a group of genetically closely related strains, which include both VSEF and VREF isolates and which harbor a particular purK allele previously associated with E. faecium swine strains, might mirror wide dissemination of a host-specific clone more prone than others to acquire and spread different antimicrobial resistance, as reported for human clinical E. faecium isolates (9). Since enterococci from swine are able to colonize in the human gut (5,7) and isolates harboring purK-9 can be recovered from hospitalized patients with severe infections (10), specific swine enterococcal strains might represent a risk for antimicrobial resistance spread in the clinical setting. Further analyses need to be performed to understand the role of international animal movements, animal feed, and colonized farmers in the spread of this particular strain and to assess whether this clone shows an increased fitness in the porcine intestine when compared to other E. faecium strains.

Drug resistance of Enterococcus faecium clinical isolates and the conjugative transfer of gentamicin and erythromycin resistance traits

Drug resistance and the transferability of resistance were examined in 218 Enterococcus faecium clinical isolates obtained from in-patients of a Japanese university hospital between 1990 and 1999. One hundred and sixty one isolates (73.9%) were drug-resistant and 127 (58.2%) isolates were resistant to two or more drugs. Vancomycin resistant E. faecium (VRE) was not isolated. The transferability of drug-resistance to an E. faecium strain was examined by broth or filter mating. Six (12.5%) of the 48 gentamicin resistance traits, and fifty (50%) of the 101 erythromycin resistance traits were transferred by filter mating. The gentamicin resistance traits of five isolates and the erythromycin resistance traits of four isolates were transferred to the recipient strains by both broth mating and filter mating at a frequency of about 10 −6 and 10 −5 per donor cell, respectively. The five gentamicin resistant strains were shown to harbor pMG1-like plasmids on the basis of their Southern hybridization with pMG1 (65.1 kbp, Gm r), which transfers efficiently between enterococci by broth mating. Each of the four erythromycin resistant transconjugants obtained by broth mating harbored a large conjugative plasmid (more than 100 kbp). The plasmids showed no homology with well-characterized enterococcal conjugative plasmids such as pAD1, pPD1, pAMβ1, pIP501 and pMG1 by Southern hybridization. Of the erythromycin resistance traits that transferred only by filter mating, it was found that the erythromycin resistance trait was conferred by a 47-kbp transposable element that transferred from the chromosome of the donor strain to different sites within the pheromone responsive plasmid pAD1 (60 kbp) of the recipient strain, suggesting that the erythromycin resistance trait was encoded on a conjugative transposon, which was named Tn 950.

Two episodes of vancomycin-resistant Enterococcus faecium outbreaks caused by two genetically different clones in a newborn intensive care unit

In 2001 two outbreak episodes (January-March and June-July) caused by vancomycin-resistant E. faecium (VRE) of the VanA-type were observed at a neonatal intensive care unit (NICU) of a university hospital in south-west Germany. To identify the initial source and the route of transmission environmental samples were examined as well as stool samples from patients and the staff. VRE was not found in environmental samples. However, stool samples from 24 hospitalised children tested positive and bacterial clonality was assessed by Sma1-based macro restriction analysis. Furthermore, esp gene and vancomycin resistance gene carriage were examined as well as bacteriocin production. PCR analysis showed that all 24 isolates carried vanA gene cluster, encoding resistance to vancomycin and teicoplanin. However, five of the vanA-positive isolates were resistant to vancomycin but not to teicoplanin. Only these five isolates produced bacteriocin, but in none of the isolates esp gene was detected. PFGE revealed that both outbreaks were caused by two different clones. The patient initiating the first episode, was identified whereas the origin of the second episode remained unknown. From one of the 40 staff stool samples VRE was isolated. This strain was related to the clone of the summer outbreak. In conclusion there were two independent episodes of self limiting VRE outbreaks and transmission on the ward is highly probable.

Pharmacology Review

Linezolid is an oxazolidinone antibiotic recently approved for treatment of infections due to antibiotic-resistant strains of Enterococcus faecium , Staphylococcus aureus, and Streptococcus pneumoniae. Because infections with these organisms, particularly vancomycin-resistant E faecium (VREF) and methicillin-resistant S aureus (MRSA), are becoming more common in critically ill neonates, linezolid is likely to play an increasingly important role in the antibiotic treatment of neonates who have antibiotic-resistant gram-positive infections. ### Mechanism of Action Oxazolidinone antibiotics, including linezolid, inhibit bacterial protein translation through a unique mechanism. Linezolid binds to the 23S subunit of the bacterial 50S ribosome. In doing so, the antibiotic blocks formation of the 70S translation initiation complex. Not surprisingly, nonclinical strains that have 23S rRNA mutations have shown linezolid resistance in vitro. ### Spectrum of Action Organisms against which linezolid has proven antibacterial efficacy include: E faecium (vancomycin-resistant strains only), S aureus (including methicillin-resistant strains), S agalactiae , S pneumoniae, and S pyogenes. Linezolid also shows in vitro activity against E faecalis (including vancomycin-resistant strains), E faecium (vancomycin-susceptible strains), S epidermidis (including methicillin-resistant strains), S haemolyticus , S pneumonia (penicillin-resistant strains), viridans-group streptococci, and Pasteurella multocida. In general, linezolid is bacteriostatic for staphylococci and enterococci, but is bactericidal for streptococci. Linezolid has activity against methicillin-sensitive and -resistant strains of S aureus and reportedly is active even against glycopeptide-intermediate and -resistant S aureus strains. ### Absorption Linezolid is administered either intravenously or orally. The intravenous preparation contains 2 mg/mL linezolid in an isotonic citrate buffer; the oral suspension contains 20 mg/mL linezolid. The oral bioavailability of linezolid suspension in older children and adults is 100% and is not altered by food. Neither preparation contains alcohol. No data on oral absorption in neonates are available. ### Distribution Linezolid distributes to well-perfused tissues and has low plasma protein binding (approximately 31%). Studies have shown that linezolid penetrates into osteoarticular tissues well, exceeding the minimum inhibitory …

Multilocus sequence typing scheme for Enterococcus faecium.

A multilocus sequence typing (MLST) scheme has been developed for Enterococcus faecium. Internal fragments from seven housekeeping genes of 123 epidemiologically unlinked isolates from humans and livestock and 16 human-derived isolates from several outbreaks in the United States, the United Kingdom, Australia, and The Netherlands were analyzed. A total of 62 sequence types were detected in vancomycin-sensitive E. faecium (VSEF) and vancomycin-resistant E. faecium (VREF) isolates. VSEF isolates were genetically more diverse than VREF isolates. Both VSEF and VREF isolates clustered in host-specific lineages that were similar to the host-specific clustering obtained by amplified fragment length polymorphism analysis. Outbreak isolates from hospitalized humans clustered in a subgroup that was defined by the presence of a unique allele from the housekeeping gene purK and the surface protein gene esp. The MLST results suggest that epidemic lineages of E. faecium emerged recently worldwide, while genetic variation in both VREF and VSEF was created by longer-term recombination. The results show that MLST of E. faecium provides an excellent tool for isolate characterization and long-term epidemiologic analysis.

Cost of hospitalization for and risk factors associated with vancomycin-resistant Enterococcus faecium infection and colonization.

The increase in costs of hospitalization for patients with drug-resistant infection may be associated with drug resistance itself or with the severity of the underlying illness that predisposes patients to acquire the drug-resistant infection. To address this issue, risk factors and cost of hospitalization were compared for patients infected or colonized with vancomycin-susceptible Enterococcus faecium (VSEF) or vancomycin-resistant E. faecium (VREF) in a large tertiary-care hospital in New York City. From January 1995 through December 1996, 157 patients with VSEF and 262 patients with VREF were identified. CMI (case-mix index) was assigned to each patient as a measure of severity of illness, with a CMI of 1 considered to represent illness of average severity. For all patients who were assigned a CMI of <3, the cost per day of hospitalization for patients with VREF was significantly greater than that for patients with VSEF. However, for patients with a CMI of >3, there was no difference between cost of hospitalization for patients with VREF and that for patients with VSEF. These observations indicate that, although vancomycin resistance is associated with an increased cost of hospitalization for less severely ill patients with VREF, patients with severe underlying illness, regardless of vancomycin resistance, incur similar hospitalization costs.

Isolation of vancomycin-resistant Enterococcus faecium from Italian cheeses

Several industrial and artisan Italian cheeses were screened for the presence of vancomycin-resistant enterococci (VRE). One hundred and two strains, mostly belonging to the species Enterococcus faecium after species-specific PCR identification, were tested for antibiotic susceptibility by standard disc diffusion method and for resistance to vancomycin in liquid medium. About 25% of strains were resistant to both vancomycin and teicoplanin. PCR experiments showed that all resistant isolates harboured the vanA gene. Minimum inhibitory concentration (MIC) values of vancomycin for most of the vancomycin resistant E. faecium (VREF) ranged from 128 to 512 μg ml−1(high level resistance). PCR fingerprinting of VREF indicated that multiple isolation of the same strains did not occur. The importance of finding VRE in cheeses is discussed.

Low Prevalence of VRE Gastrointestinal Colonization of Hospitalized Patients in Manitoba Tertiary Care and Community Hospitals

To determine the prevalence of vancomycin-resistant enterococci (VRE) bowel colonization in hospitalized patients in Manitoba who had stool specimens collected for Clostridium difficile toxin and/or culture testing. Two tertiary care and five community hospitals in Winnipeg and three rural Manitoba community hospitals participated in this study. From January 1 to December 31, 1997 stool specimens, one per patient, submitted to hospital microbiology laboratories for C difficile toxin and/or culture testing were screened for VRE on colistin-nalidixic acid-vancomycin (6 microg/mL) (CNAV) agar plates. The study was divided into six, eight-week intervals. Stool specimens received in the first two weeks of each eight week interval were screened for VRE. A total of 1408 stool specimens were submitted over the 48-week study period. Sixty-seven (4.8%) patients with VRE colonization of their lower gastrointestinal tract were identified. Three of the 67 (4.5%) VRE isolates were Enterococcus faecium, with the remaining 64 (95.5%) were Enterococcus gallinarum. The three vancomycin-resistant E faecium -VREF- (from two different Winnipeg hospitals) demonstrated the vanA genotype, and were resistant to vancomycin, teicoplanin and ampicillin. All three VREF isolates also demonstrated high level resistance to both gentamicin and streptomycin but were susceptible to quinuprisitin/dalfopristin and LY333328. VRE colonization in hospitalized patients in Manitoba is infrequent and most commonly due to E gallinarum. The prevalence of VREF colonization in the patients studied was 0.2% (three of 1408).