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PubMed1995

Detection of aminoglycoside-penicillin synergy against Enterococcus faecium using high-content aminoglycoside disks.

Thirty-seven Enterococcus faecium strains were screened for high-level aminoglycoside resistance with an agar diffusion test using high-content aminoglycoside disks (300 micrograms of streptomycin and 120 micrograms of gentamicin, tobramycin, kanamycin or amikacin). The inhibition zones obtained were correlated with results of time-kill penicillin-aminoglycoside synergy studies. An 11 mm breakpoint differentiated strains susceptible or resistant to the synergy of streptomycin plus penicillin. Irrespective of the inhibition zones obtained with tobramycin and kanamycin disks, Enterococcus faecium strains never showed synergy with penicillin in combination with these aminoglycosides. Penicillin-amikacin synergy cannot be predicted by the amikacin disks. Nevertheless, even though kanamycin disks do not predict penicillin-kanamycin synergy, they can be used to predict penicillin-amikacin synergy. In summary, high-content streptomycin, gentamicin and kanamycin disks can be used to predict the susceptibility of Enterococcus faecium strains to the synergistic combination of penicillin plus one of the aminoglycosides (streptomycin, gentamicin or amikacin, respectively).

Aminoglycosides↗

PubMed1990

In vitro activity of daptomycin-metronidazole combinations against mixed bacterial cultures: reduced activity of metronidazole against Bacteroides species in the presence of Enterococcus faecalis.

The in vitro activity of daptomycin-metronidazole combinations against mixed cultures of gram-positive facultative cocci and strains of the Bacteroides fragilis group was investigated. Metronidazole did not influence the high activity of daptomycin against strains of Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis in the absence or presence of the co-cultured Bacteroides strains. In contrast, the Enterococcus faecalis isolates protected the co-cultured Bacteroides strains against the killing effect of metronidazole, even at a concentration four- or eightfold the MIC of metronidazole. Killing curve experiments confirmed this protective effect of different isolates of Enterococcus faecalis.

Anti-Bacterial Agents↗

PubMed1990

Isolation of three strains of beta-lactamase-producing Enterococcus faecalis in Argentina.

Of the 90 strains of Enterococcus spp. isolated in an Argentine laboratory in the period from January to July 1989, three were identified as beta-lactamase-producing Enterococcus faecalis. According to the literature reviewed, these appear to be the first beta-lactamase-positive strains of Enterococcus isolated outside the USA. They differed from most beta-lactamase-producing strains already described in that they were susceptible to low concentrations of macrolides. All three strains were resistant to high concentrations of aminoglycosides.

Aminoglycosides↗

PubMed1997

Enterococcus cecorum septicemia in a malnourished adult patient.

Enterococcus cecorum, a species typically isolated from chicken, pigs, calves, horses, ducks, cats, dogs, and canaries, was isolated from the blood of a patient with severe septicemia. The isolate was identified by conventional biochemical tests. Identity as Enterococcus cecorum was confirmed by SDS-PAGE analysis of whole cell protein. This is the first report of the isolation of Enterococcus cecorum in a clinical setting.

Adult↗

PubMed1998

Identification of clinically important species of Enterococcus within 1 day with randomly amplified polymorphic DNA (RAPD).

The use of randomly amplified polymorphic DNA (RAPD) for rapid, reliable, and easily interpreted identification of enterococci was evaluated. Nineteen type strains of Enterococcus, 12 reference strains, and 114 clinical isolates of Enterococcus were analyzed. Discrimination was obtained between most type strains, the exceptions being Ent. casseliflavus and Ent. flavescens, which had relatively similar RAPD-profiles. Ent. faecalis and Ent. faecium were readily separated, and Ent. gallinarum and Ent. durans could also be identified. Extracts to be used in the polymerase chain reaction (PCR) were prepared directly from agar plate colonies, which made it possible to complete the identification procedure in one day. RAPD was proved to be a fast and reliable method for identification of most Enterococcus spp. of clinical significance.

Enterococcus↗

PubMed2001

Photobiological activity of exogenous and endogenous porphyrin derivatives in Escherichia coli and Enterococcus hirae cells.

Photodynamic treatment, the combined application of a photosensitiser and visible light, represents a new and promising approach for the inactivation of microorganisms. The photosensitising potentials of exogenous zinc-phthalocyanine-tetrasulphonate (ZnPsTS), tetraphenylporphyrins (TPPs) and endogenous porphyrin derivatives were tested and compared on Gram-negative and Gram-positive bacteria, Escherichia coli B. and Enterococcus hirae, respectively. The synthesis of endogenous porphyrins was induced by 5-aminolevulinic acid (delta-ALA). The porphyrin- or delta-ALA-treated cells were irradiated with white light. The photosensitising efficiency of endogenous derivatives on both types of bacteria is ZnPcTS < TP(4-OGluOH)3P < TP(4-OGluOH)4P. However, neither exogenous derivatives exhibit appreciable photosensitising activity for disinfection application. ALA-induced photodynamic treatment showed good potential for the inactivation of Escherichia coli cells, but not towards Enterococcus hirae cells. The failure of photosensitisation of the Enterococcus hirae strain selected indicates that apart from the Gram-positive character, other structural elements of the membrane can influence the result of photodynamic treatments.

Dose-Response Relationship, Radiation↗

PubMed2000

Epidemiological, microbiological, clinical, and prognostic factors of bacteremia caused by high-level vancomycin-resistant Enterococcus species.

A case-control study was performed between 1994 and 1996 in order to study the epidemiological, microbiological, clinical, and prognostic features of high-level vancomycin-resistant enterococcal bacteremia. Seventeen consecutive patients who had clinically significant bacteremia due to vancomycin-resistant enterococci (vanA genotype: 16 Enterococcus faecalis, 1 Enterococcus faecium) were compared with 169 who had vancomycin-susceptible enterococcal bacteremia. The following were selected by multivariate analysis as independent risk factors that influenced the development of high-level vancomycin-resistant enterococcal bacteremia: prior glycopeptide therapy (P=0.049); inclusion in a hemodialysis program (P=0.046); prior therapy with corticosteroids or antineoplastic agents (P=0.029); and prior surgical treatment (P=0.022). The following other factors were selected by univariate analysis: tracheostomy (P=0.002); prolonged hospitalization (P=0.01); and any kind of puncture (P=0.02). The crude associated-mortality rate was 13.4%. Gene amplification of vanA was positive for 17 strains of enterococci. Pulsed-field gel electrophoresis of genomic DNA after SmaI digestion of vanA isolates revealed that one strain predominated (10 isolates), though at least four similar banding patterns were identified (6 isolates). The 16 strains closely related to the outbreak were investigated further. The surgical intensive care unit was the first and most involved service. The hospital outbreak of vanA vancomycin-resistant enterococcal bacteremia occurred between 1994 and 1995 and was caused by Enterococcus faecalis. This is believed to be the first and only such outbreak described in a Spanish hospital thus far.

Adolescent↗

PubMed2001

Antimicrobial activity of everninomicin against clinical isolates of Enterococcus spp., Staphylococcus spp., and Streptococcus spp. tested by Etest.

The in-vitro antimicrobial activity of everninomicin, a novel oligosaccharide antibiotic, was tested against clinical isolates of 11 methicillin-susceptible Staphylococcus aureus (MSSA) strains, 11 methicillin-resistant S. aureus (MRSA) strains, 22 Staphylococcus epidermidis strains, 23 Enterococcus faecalis strains, 23 Enterococcus faecium strains, 23 Enterococcus avium strains, 27 Streptococcus pneumoniae strains, 22 Streptococcus pyogenes strains, and 20 Streptococcus agalactiae strains. The minimum inhibitory concentrations (MICs) of everninomicin were determined by Etest and compared with those of vancomycin, teicoplanin, and minocycline. The Etest showed that everninomicin exhibited excellent activity (MIC, <0.016 to 1.5 microg/ml) against the gram-positive cocci tested. The antimicrobial activity of everninomicin against S. aureus and S. epidermidis was stronger than that of vancomycin, teicoplanin, and minocycline, in particular against MRSA, with an MIC50 of 0.38 microg/ml and an MIC90 of 0.5 microg/ml. Against strains of enterococci and streptococci, everninomicin was more active than vancomycin, but as active as teicoplanin.

Aminoglycosides↗

PubMed1994

Sequence of the vanB and ddl genes encoding D-alanine:D-lactate and D-alanine:D-alanine ligases in vancomycin-resistant Enterococcus faecalis V583.

A pair of degenerate oligodeoxyribonucleotides was used to amplify, by the polymerase chain reaction (PCR), DNA fragments internal to genes encoding D-Ala:D-Ala ligase-related proteins of vancomycin-resistant (VmR) Enterococcus faecalis V583. Cloning and nucleotide sequencing of the PCR products indicated that fragments of two genes, designated vanB and ddl, were co-amplified. The vanB gene was previously shown to be present in Enterococcus strains expressing VanB-type VmR [Quintiliani Jr. et al., J. Infect. Dis. 8 (1993) 943-950]. The ddl gene was detected by Southern hybridization in all VmR and VmS strains of En. faecalis, but not in representatives of 17 other species of Enterococcus. The vanB and ddl genes were cloned in bacteriophage lambda and sequenced. There was extensive similarity (76% amino-acid identity) between the product of vanB and the VmR protein, VanA. The product of ddl, the D-Ala:D-Ala ligases, DdlA and DdlB, of Escherichia coli and the resistance proteins, VanA and VanB, were more distantly related (32-40% aa identity). After induction of VmR, En. faecalis V583 synthesized the cell wall precursor, UDP-N-acetylmuramyl-tetrapeptide-D-lactate, indicating that the mechanism of glycopeptide resistance in strains with the VanA and VanB phenotype is similar.

Amino Acid Sequence↗

PubMed1995

Emerging multiply resistant enterococci among clinical isolates. I. Prevalence data from 97 medical center surveillance study in the United States. Enterococcus Study Group.

To assess the evolving problem of therapeutic drug resistances among enterococci, we organized a comprehensive national (United States) surveillance trial using 99 recruited microbiology laboratories in 48 of the 49 contiguous states or districts. All but two sites completed the protocol that generated information from nearly 2000 enterococci, usually isolated from blood cultures. All strains were speciated by the same method (API 20S) and were susceptibility tested by three methods (broth microdilution, disk diffusion, and Etest) against ampicillin, penicillin, vancomycin, teicoplanin, gentamicin, and streptomycin. Strains resistant to a glycopeptide or penicillin, or possessing high-level aminoglycoside resistance were referred to the monitor's laboratory for validation and additional susceptibility testing against other alternative antimicrobial agents. The most common species were Enterococcus faecalis and Enterococcus faecium. However, antimicrobial resistance occurred most often among the E. faecium isolates. Twenty-three percent of participant centers (22 sites) reported 87 vancomycin-resistant isolates, which accounts for 4.4% of the isolates evaluated. A recent audit (March 1994) of the laboratories not reporting vancomycin resistance during the study interval (October-December 1992) revealed that 61% of sites have now recognized these strains, a threefold increase in 12-15 months. Teicoplanin remained active against 28% (Van B phenotype) of vancomycin-resistant enterococci (10 E. faecalis, 13 E. faecium, and one Enterococcus spp.). Ampicillin-resistant beta-lactamase-positive strains were found only at one medical center (two strains, 0.2% of referred or validated strains); however, ampicillin-resistant strains represented 12% of all enterococcal, but nearly 60% of E. faecium strains.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗

PubMed2001

Development of glucosidase agar for the confirmation of water-borne Enterococcus.

Analysis of 56 river water samples by the Enterolert defined substrate technique, and standard m-Enterococcus agar isolation followed by confirmation, indicated that after 24 h incubation. Enterolert significantly underestimated the true numbers of enterococci. Extending Enterolert incubatioin to 36 h improved detection but also revealed false positives. These findings prompted the development of a novel confirmation medium we have termed glucosidase agar, which was prepared by dissolving Enterolert substrate in 2% (w/v) bacteriological agar. Analysis of 1,043 colonies arising on m-Enterococcus agar from 280 freshwater, marine and sewage effluent samples, demonstrated that 2-4 h incubation on glucosidase agar was a rapid and accurate means of confirming presumptive enterococci, when compared to standard confirmation procedures that take 48 h. The combination of primary isolation on m-Enterococcus agar followed by confirmation on glucosidase agar permits maximum recovery of Enteroccus whilst effectively eliminating false positives/negatives and provides a reliable alternative use of the Enterolert defined substrate technology.

Agar↗

PubMedDate not supplied

Antimicrobial resistance from enterococci in a pediatric hospital. Plasmids in Enterococcus faecalis isolates with high-level gentamicin and streptomycin resistance.

BACKGROUND: Enterococcus spp. is an important nosocomial and community-acquired pathogen. Recent studies have documented the increasing importance of this pathogen in children, particularly in the hospital setting. Our objective in this study was to report the frequency of antimicrobial resistance in enterococci and to determine the characteristics of high-level gentamicin resistance (HLGR) plasmids in Enterococcus faecalis clinical isolates. METHODS: Two hundred eighty-nine enterococcal isolates were collected during an 18-month period from a tertiary-care pediatric hospital in Mexico City. Isolates were screened for antibiotic resistance, including HLGR. High-level, gentamicin-resistant E. faecalis strains were selected for pulsed-field electrophoresis (PFGE) typing and plasmid analysis. Transferability of resistance markers was carried out using filter matings. RESULTS: Seventy-six percent of isolates were E. faecalis, 10% were E. avium, 5.2% E. faecium, 5.2% E. raffinossus, 1.38% E. malodoratus, 0.6% E. hirae, and 0.6% E. casseliflavus. Antimicrobial resistance was ampicillin and penicillin 29%, imipenem 17%, and vancomycin 3%, HLGR 5%. The following 15 high-level, gentamicin-resistant isolates were identified: six E. faecalis; four E. avium; three E. faecium, and two E. casseliflavus. Five of the six E. faecalis isolates were different by PFGE and transferred gentamicin and streptomycin resistance on filter membranes. Transfer frequencies ranged from 8.2 x 10(-4) to 6.92 x 10(-5) transconjugants/recipient cell. The plasmid content of donors and transconjugants were homogeneous (one plasmid of 47 kb). CONCLUSIONS: In this pediatric hospital, antimicrobial resistance in Enterococcus spp. is common. Frequency of high-level, gentamicin-resistant strains is low. Mechanism of HLGR appears to be due to a single plasmid dissemination.

Drug Resistance, Microbial↗

PubMed1999

Isolation and epidemiological study of vancomycin-resistant Enterococcus faecium from patients of a haematological unit in Poland.

Enterococcus faecium has recently emerged as a serious nosocomial pathogen. Vancomycin resistant enterococci (VRE) have been isolated in Europe and the USA since 1988. This is the first report on isolation of vancomycin resistant E. faecium (VREM) strains in Poland, from Haematological Unit patients in the Clinical Hospital in Gdańsk. In total, 6412 samples were examined between December 1996 and October 1997. Five hundred and five isolates of Enterococcus spp. were collected. One hundred and one were classified as Enterococcus faecium of which 49 were resistant to vancomycin (MIC > 256 mg/L) and teicoplanin (MIC > 256 mg/L), characteristic of the VanA phenotype. Twenty-nine patients were infected or colonized. A PCR-based specific diagnostic assay confirmed the phenotype. The multiplex PCR-restriction fragment length polymorphism patterns were consistent with VanA-type of vancomycin-resistant E. faecium for all isolates examined. These isolates were epidemiologically-related as shown by PCR-fingerprinting.

Adult↗

PubMed1998

In vitro activities of six fluoroquinolones against Canadian isolates of vancomycin-sensitive and vancomycin-resistant Enterococcus species.

The in vitro activities of six fluoroquinolones were determined against 1482 Enterococcus species isolates collected as part of a 1996 Canadian surveillance study. Clinafloxacin MIC90s were 4 or 8 microg/mL, trovafloxacin and BAY 12-8039 MIC90s were 8 or 16 microg/mL, sparfloxacin MIC90s were 32 microg/mL, and ciprofloxacin and ofloxacin MIC90s were >32 microg/mL for the vancomycin-sensitive Enterococcus faecalis, vancomycin-sensitive Enterococcus faecium, and vancomycin-resistant E. faecium isolates collected.

Anti-Bacterial Agents↗

PubMed2000

Aminoglycoside-modifying enzymes in high-level streptomycin and gentamicin resistant Enterococcus spp. in Spain.

Aminoglycoside resistance was evaluated in 690 enterococcus strains isolated from different clinical sources originating from patients at the University Clinic Hospital of Zaragoza (Spain). The enterococci obtained from clinically significant samples (blood, urine, or exudates) showed more high-level resistance to gentamicin and streptomycin (65 and 42%, respectively) than those isolated from faecal samples (49 and 23%, respectively). Aminoglycoside-modifying enzymes (AME) from 119 of these high-level gentamicin and streptomycin resistant enterococcus strains were studied. The most frequent AMEs found were APH(3') and AAC(6')-APH(2"). More than one enzyme was detected in 71% of the strains (four different enzymes in 5% of the strains). Three Enterococcus faecalis strains had ANT(4')(4") enzymatic activity. Different enzymatic expressions of the bifunctional enzyme AAC(6')-APH(2") were demonstrated in strains in which the complete aac(6')-aph(2") gene was detected by PCR and hybridization: (i) AAC(6') + APH(2") activity; (ii) AAC(6') only; (iii) APH(2") only; and (iv) no activity of AAC(6') or APH(2").

Anti-Bacterial Agents↗

PubMed2002

Interaction of fibronectin and aggregation substance promotes adherence of Enterococcus faecalis to human colon.

This in vitro study investigates the interaction between aggregation substance (AS), a virulence factor of Enterococcus faecalis, and colonic mucosal fibronectin in normal colon and colon from patients with Crohn's disease. Fibronectin was found to be overexpressed in Crohn's disease compared to normal colon. Compared to E. faecalis OG1X:pAM944 (AS-negative), E. faecalis OG1X:pAM721 (expressing AS) showed a significantly enhanced adhesion to human colonic mucosa in normal colon and in colon from patients with Crohn's disease. Double-staining of fibronectin and AS-positive enterococci showed that colocalization of bacteria and fibronectin was significantly more frequent in Crohn's disease than in normal colon. Preincubation of bacteria with soluble fibronectin caused a significant reduction in the adherence to fibronectin. In conclusion, the interaction between AS and fibronectin plays is an important factor that mediates adhesion of Enterococcus faecalis to colonic mucosa. This might be one of the mechanisms responsible for bacterial translocation of Enterococcus faecalis.

Bacterial Adhesion↗

PubMed2003

Potential of the enterocin regulatory system to control expression of heterologous genes in Enterococcus.

AIMS: To exploit the enterocin regulatory system for regulated expression of genes in Enterococcus. METHODS AND RESULTS: Production of some pediocin-like bacteriocins such as enterocin A in Enterococcus is regulated by a three-component system comprising a histidine kinase (entK ), a response regulator (entR) and an induction factor (entF ). Exposure to the induction factor results in the transcription of gene(s) under the control of the enterocin A promoter, including entA which encodes the bacteriocin. In an effort to exploit this system for expression of genes in Enterococcus, a number of vectors were constructed which contain the entA promoter followed by convenient cloning sites to introduce gene(s) of interest. These vectors were used in an enterococcal background which does not produce induction factor but does produce both the kinase and regulator proteins. The system was tested using the reporter genes ltnI (lacticin 3147 immunity) and gusA (beta-glucuronidase) under the control of the entA promoter. CONCLUSIONS: Upon addition of the induction factor, the beta-glucuronidase activity increased 20-fold when compared with uninduced cells. In addition, concentrations of as little as 0.2 nm synthetic EntF were sufficient to give maximal expression. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential benefit of having an expression system based on EntF is that gene expression can be finely controlled upon addition of low concentrations of a peptide that can easily be artificially synthesized.

Anti-Bacterial Agents↗

PubMed2002

Emergence of vancomycin-resistant Enterococcus faecium at a tertiary care hospital in Karachi, Pakistan.

Vancomycin-resistant enterococcus (VRE) has not been reported previously in Pakistan. This is the first report where in vancomycin-resistant Enterococcus faecium was isolated from the clinical specimens of six patients admitted to the intensive care unit (ICU) and neonatal intensive care unit (NICU) of the Aga Khan University Hospital, Karachi. To identify the extent of the outbreak, rectal swabs were obtained from all the patients admitted to the ICU and NICU at that time. A total of 10 strains of vancomycin-resistant Enterococcus faecium were isolated. All the strains showed high-level resistance to both glycopeptides (vancomycin and teicoplanin) with a vancomycin minimum inhibitory concentration greater than 256 mg/L. All isolates had the vanA gene detected by polymerase chain reaction. The contour-clamped homogeneous electric field (CHEF) pattern demonstrated that all but one of the isolates were of a single clone, suggesting that they were derived from common source. Use of vancomycin and prolonged hospitalization were common features in all cases investigated.

Adult↗