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PubMed2003

Nosocomial superinfections due to linezolid-resistant Enterococcus faecalis: evidence for a gene dosage effect on linezolid MICs.

Resistance to linezolid among Enterococcus faecium and Enterococcus faecalis isolates has been reported in patients who receive a prolonged course of the drug. We report two cases of linezolid-resistant Enterococcus faecalis that occurred in patients who previously received linezolid for infections with vancomycin-resistant Enterococcus faecium. Both isolates had the G2576U mutation in the 23S rRNA previously reported in isolates of Enterococcus faecium. The number of gene copies mutated in the 23S rRNA correlated with the level of resistance.

Acetamides↗

PubMedDate not supplied

[Group D streptococci and enterococci: identification, sensitivity to antibiotics and a study of the high level resistance to aminosides (Charles Nicolle Hospital in Tunis)].

197 strains of enterococcus and group D Streptococcus were isolated from human material at Charles Nicolle Hospital (Tunis) and identified by biochemical tests: 174, Enterococcus faecalis, 6 Enterococcus faecium, 2 Enterococcus durans and 15 Streptococcus bovis. The sensitivity to antibiotics was studied: all Enterococcus faecium were resistant at least to one antibiotic, 15% of Enterococcus faecalis were sensitive for all antibiotics tested the other species were frequently sensitive. High level resistance to aminoglycosides were frequent in Enterococcus faecalis 40%: among these strains high level resistance to gentamicin accounts for 12% and 18 frequently associated with resistance to kanamycin and streptomycin, this situation present therapeutic problems in case of severe infection.

Aminoglycosides↗

PubMed1993

Frequency and antimicrobial susceptibility of clinical isolates of enterococci.

A study was performed to determine the frequency and antimicrobial susceptibility of Enterococcus species in clinical specimens. Of 943 aesculin-positive isolates, 873 (92%) were identified as enterococci (737 Enterococcus faecalis, 129 Enterococcus faecium and 7 other Enterococcus species). High-level resistance to gentamicin was found in 15.2% of Enterococcus faecalis, but not in Enterococcus faecium; 58% of Enterococcus faecium were resistant to gentamicin at a concentration of 64 mg/l. None of the isolates were shown to possess vancomycin resistance.

Drug Resistance, Microbial↗

PubMed2001

Molecular analysis of vanA enterococci isolated from humans and animals in northeastern Italy.

A total of 53 vancomycin-resistant vanA-positive enterococci isolates from poultry farms (17 Enterococcus faecium; 8 Enterococcus durans) and from different hospitals (23 E. faecium; 5 Enterococcus faecalis) in northeastern Italy were compared on the basis of their antibiotic susceptibilities, their SmaI pulsed-field gel electrophoresis (PFGE) patterns, and the organization of their Tn1546-related elements. Ampicillin resistance was similar in both groups of isolates (52 and 60.7%, respectively), whereas human strains were more resistant to high-level gentamicin and streptomycin. A total of 52% of animal strains and 60% of human strains were resistant to tetracycline, and 56% and 46.4% to quinupristin/dalfopristin, respectively. In E. faecium and E. durans animal isolates, nine and six distinct PFGE patterns, respectively, were found: in two instances indistinguishable isolates were found from different farms. In E. faecium and E. faecalis human isolates, nine and six distinct PFGE patterns, respectively, were found; among E. faecium strains, 12 were identical or closely related and were isolates from the same hospital. Elements mediating vanA-glycopeptide resistance were characterized by PCR with primers that amplified 10 overlapping fragments of Tn1546. A total of 84.6% of animal strains and 64.2% of human strains contained elements indistinguishable from the prototype Tn1546. In addition, nine different types were identified, but none was common to animal and human strains.

Animals↗

PubMed2005

Oligonucleotide microarray for identification of Enterococcus species.

For detection of most members of the Enterococcaceae, the specificity of a novel oligonucleotide microarray (ECC-PhyloChip) consisting of 41 hierarchically nested 16S or 23S rRNA gene-targeted probes was evaluated with 23 pure cultures (including 19 Enterococcus species). Target nucleic acids were prepared by PCR amplification of a 4.5-kb DNA fragment containing large parts of the 16S and 23S rRNA genes and were subsequently labeled fluorescently by random priming. Each tested member of the Enterococcaceae was correctly identified on the basis of its unique microarray hybridization pattern. The evaluated ECC-PhyloChip was successfully applied for identification of Enterococcus faecium and Enterococcus faecalis in artificially contaminated milk samples demonstrating the utility of the ECC-PhyloChip for parallel identification and differentiation of Enterococcus species in food samples.

DNA, Bacterial↗

PubMed1999

Antimicrobial resistance in key bloodstream bacterial isolates: electronic surveillance with the Surveillance Network Database--USA.

To assess the prevalence of antimicrobial-resistant pathogens among the most common bloodstream isolates, we examined antimicrobial susceptibility data from The Surveillance Network Database-USA, an electronic surveillance system that collects data from 118 clinical microbiology laboratories across the United States. Between 1995 and 1997, resistance to both vancomycin and ampicillin was much more prevalent among Enterococcus faecium than Enterococcus faecalis, suggesting the need for laboratories to identify to species. When staphylococcal isolates were examined for reduced susceptibility to vancomycin (minimum inhibitory concentration = 4 microg/mL), the frequency was highest in methicillin-resistant coagulase-negative staphylococci. We also learned that nonsusceptibility to ceftazidime in Klebsiella pneumoniae was more prevalent among isolates from blood (12.7%) than among isolates from urine (7.1%) or respiratory sources (9.3%). Although antimicrobial resistance is low overall for isolates of Escherichia coli from blood, the prevalence of cefoxitin resistance among ceftazidime-resistant strains (61.9%) suggests the action of mechanisms other than extended-spectrum beta-lactamase.

Anti-Bacterial Agents↗

PubMed1993

The vanB gene confers various levels of self-transferable resistance to vancomycin in enterococci.

Thirty-nine strains of Enterococcus faecium and Enterococcus faecalis resistant to vancomycin and susceptible to teicoplanin on disk susceptibility testing (phenotypic class B) were isolated in 15 hospitals in Europe and the United States. The MICs of vancomycin for these strains ranged from 4 to 1024 micrograms/mL. Part of the vancomycin resistance gene vanB from E. faecalis V583 hybridized with a single but variably sized HindIII-KpnI fragment of total DNA from all 39 strains. This indicates that a single class of resistance determinants accounts for the VanB phenotype. No hybridization was detected with DNA from intrinsically resistant Enterococcus gallinarum or Enterococcus casseliflavus. Hybridization with DNA from enterococcal strains susceptible to or with acquired resistance to vancomycin and teicoplanin was not observed. The genes conferring resistance to vancomycin were self-transferable to other Enterococcus strains in 14 of the 39 strains. It thus appears that vanB confers various levels of conjugative vancomycin resistance in enterococci.

Bacterial Proteins↗

PubMed1998

Antibacterial efficacy of nisin against multidrug-resistant Gram-positive pathogens.

The rapid spread of multidrug-resistant bacterial pathogens necessitates the search for alternative antibacterial agents. We examined the efficacy of the antibiotic nisin against 56 multidrug-resistant isolates of Streptococcus pneumoniae, 33 Staphylococcus aureus and 29 vancomycin-resistant Enterococcus faecium and Enterococcus faecalis isolates. The test strains represented a large variety of clonal types (as determined by a combination of DNA fingerprints) isolated from a variety of geographic sources, and included some of the major internationally-spread multiresistant epidemic clones of S. pneumoniae and methicillin-resistant S. aureus (MRSA), MRSA strains resistant to over 16 generically distinct antibacterial agents, and enterococcal strains resistant to all currently available chemotherapeutic agents including glycopeptides. In the overwhelming majority of cases, treatment of growing cultures with nisin at 1 mg/L (S. pneumoniae) or 10-20 mg/L (in MRSA and enterococci) caused extensive (10(3)- to 10(4)-fold) loss of viable titre accompanied by various degrees of loss in the optical density of the cultures, which was most extensive in pneumococci (>90%) and least extensive (40-50%) in enterococci. Nevertheless, extensive variation in rates of nisin-induced autolysis was observed in each bacterial species. Serial exposure of a penicillin-susceptible strain of S. pneumoniae to nisin (1 mg/L) in liquid culture resulted in the rapid appearance of stable nisin-resistant mutants in which the MIC increased from 0.4 to 6.4 mg/L and the resistance trait was transferable by genetic transformation.

Anti-Bacterial Agents↗

PubMedDate not supplied

Interactions of vancomycin resistant enterococci with biomaterial surfaces.

Enterococci are a frequent cause of nosocomial infections and are often found adherent to indwelling catheters. Concern about such device associated infections has increased with the appearance of vancomycin resistant (VR) enterococci. However, the possible influence of vancomycin resistance in the pathogenesis of biomaterial centered infection has not yet been assessed. Using polyethylene terephthalate (PET) disks as model surfaces, the authors evaluated possible differences in the adherence and persistence of vancomycin sensitive (VS) and VR strains of Enterococcus faecium and Enterococcus faecalis on biomaterial surfaces in vitro and in vivo. The results indicate that: 1) as expected, the clearance of free VR and VS organisms after intraperitoneal injection into normal mice is equally efficient. 2) In vitro, VR bacteria are roughly twice as adherent to plasma coated PET surfaces as are VS organisms. 3) However, in vivo persistence of VS organisms preadherent to biomaterial implants is 5- to 10-fold better than that of preadherent VR organisms. The authors now believe that a discrete change in bacterial cell wall composition between VR and VS enterococci may contribute to the substantial differences in bacterial adhesion and survival of adherent organisms.

Animals↗

PubMed2003

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.

Acetamides↗

PubMed2006

Partial characterization of enterocin MR99 from a corn silage isolate of Enterococcus faecalis.

AIMS: To assess the inhibitory activity on Gram-positive and Gram-negative bacteria of several species of enterococci recovered from a natural corn silage. METHODS AND RESULTS: The inhibitory activity of strains of Enterococcus faecalis (58), Enterococcus faecium (35), Enterococcus gallinarum (3) and Enterococcus casseliflavus (4) were studied employing indicator strains from various sources (clinical, food and ATCC). Enterococcus faecalis MR99, the only strain with inhibitory activity, inhibited other enterococci, Listeria spp., Staphylococcus aureus, Clostridium spp., Bacillus spp., Escherichia coli, Shigella sonnei and Shigella flexneri. The bacterium contained only one conjugative pheromone-responsive plasmid. The partially chromatography-purified MR99 enterocin (PPE) had a molecular weight of approx. 5000 Da and a pI of 6.2, was sensitive to proteolytic enzymes and could be extracted in benzene and butanol. It appeared stable to adjustment of pH 4.0, 5.0, 6.0, 7.0 and 8.0 and was resistant to heat. Inactivation was at 15 min at 121 degrees C. Enterocin MR99 was bactericidal on strains of Listeria monocytogenes, Staph. aureus, and bovine mastitis agents, it was bacteriostatic on E. coli. Although enterocins MR99 and AS48 have inhibitory activity on Gram-negative bacilli, PCR studies demonstrated a lack of relationship between them. CONCLUSIONS: The active component had a protein nature, was resistant to heat and presented a wide inhibitory spectrum. SIGNIFICANCE AND IMPACT OF THE STUDY: The biological properties of Ent. faecalis MR99 suggest that this strain merits further investigations so it can be applied in human and veterinary health programmes.

Bacillus↗

PubMedDate not supplied

In vitro susceptibility to everninomycin of gram-positive nosocomial pathogens isolated from intensive care units in Germany.

BACKGROUND: Gram-positive bacteria are increasingly found to be causative pathogens in nosocomial infections, and the occurrence of vancomycin resistance in enterococci as well as staphylococci has prompted the investigation of alternative antimicrobial agents active against these strains. Everninomycin, a new oligosaccharide antibiotic, has excellent in vitro activity against gram-positive bacteria, including those resistant to vancomycin. However, avilamycin, a related compound, has been used in Europe as a growth promoter in animal food for years and concern has been raised that cross-resistance in clinical isolates may arise. METHODS: We studied a collection of 268 nosocomial gram-positive isolates from intensive care unit patients with nosocomial pneumonia, urinary tract infection and sepsis, using standard in vitro susceptibility testing. RESULTS: It could be shown that all species tested were exquisitely sensitive to everninomycin (MIC(90) of 0.38 microg/ml for Staphylococcus aureus, 0.5 microg/ml for enterococci and 0.75 microg/ml for coagulase-negative staphylococci). Furthermore, no difference could be observed between methicillin-resistant and methicillin-sensitive S. aureus or between Enterococcus faecium and Enterococcus faecalis. CONCLUSIONS: These results suggest that everninomycin is a promising antibiotic for the treatment of nosocomial infections in intensive care unit patients and that the use of a related substance as an additive in animal food has not yet promoted resistance in clinical isolates.

Aminoglycosides↗

PubMedDate not supplied

Comparison of in vitro inhibitory and bactericidal activities of daptomycin (LY 146032) and four reference antibiotics, singly and in combination, against gentamicin-susceptible and high-level-gentamicin-resistant enterococci.

The in vitro inhibitory and bactericidal activities of daptomycin and reference antibiotics were determined by serial macrobroth dilution for 23 gentamicin-susceptible (MIC: < 2,000 mg/l) and 21 high-level-gentamicin-resistant (HLGR) Enterococcus faecalis, Enterococcus faecium, and Enterococcus avium isolates. The activities of daptomycin, vancomycin, and teicoplanin were independent of the gentamicin susceptibility profile and species tested. For all the isolates, the inhibitory activity of daptomycin (MIC90: 2 mg/l) was comparable to vancomycin (MIC90: 2 mg/l), but less than that of teicoplanin (MIC90: 0.5 mg/l). Daptomycin demonstrated excellent bactericidal activity against all enterococci tested (MBC90: 8 mg/l). In contrast, all microorganisms were tolerant to vancomycin and teicoplanin. Ampicillin and ciprofloxacin MICs and MBCs were dependent on enterococcal gentamicin resistance profile and species, with MICs and MBCs that ranged between 1 and > 64 mg/l. By time-kill curves, the combination of daptomycin plus ampicillin demonstrated synergistic bactericidal activity against gentamicin-susceptible and HLGR E. faecalis. Daptomycin, singly and in combination, may be useful in treating enterococcal infections, including those caused by HLGR microorganisms.

Ampicillin↗

PubMed2006

A field study of the microbiological quality of fresh produce of domestic and Mexican origin.

Produce is responsible for an increasingly larger proportion of foodborne disease outbreaks. In particular, the globalization of the food supply may introduce new food safety risks and allow widespread distribution of contaminated food, particularly produce. The objectives of this study were to: (i) compare the overall quality of domestic and Mexican produce throughout the packing process; (ii) examine changes in microbiological quality of both domestic and Mexican produce at each stage of production and processing; and (iii) evaluate the prevalence of select pathogens on fresh produce, including leafy green, herbs, melons, and vegetables. Furthermore, we also sought to characterize the antibiotic resistance profiles of Enterococcus faecium and Enterococcus faecalis strains isolated from fresh produce. A total of 466 produce and matching environmental swab samples was collected from various locations in packing sheds in the southern US from November 2002 through December 2003. These samples were assayed by enumerative tests for total aerobic bacteria (APC), total coliforms, total Enterococcus, and E. coli. Produce samples were also analyzed for the presence of Salmonella, Listeria monocytogenes, Shigella, and E. coli O157:H7. A total of 112 E. faecium and E. faecalis isolates were further screened for antibiotic resistance using a panel of seventeen antibiotics. Overall, the microbiological quality of fresh produce ranged from 4.0 to 7.9 log(10) CFU/g (APC); less than 1.0 log(10) to 4.5 log(10) CFU/g (coliforms); less than 1.0 log(10) to 4.0 log(10) CFU/g (E. coli); and less than 1.0 log(10) to 5.4 log(10) CFU/g (Enterococcus). No Salmonella, Shigella, or E. coli O157:H7 were detected from the 466 25-g produce samples tested. However, three domestic cabbage samples were found to be positive for L. monocytogenes. Of the Enterococcus isolates, E. faecium had a higher degree of resistance to antibiotics in general, while Enterococcus spp. isolated from Mexican produce had a higher degree of antibiotic resistance when compared to strains isolated from produce samples of domestic origin. Despite increased attention to the role of imported produce in foodborne disease, this study does not support the assumption that domestic produce is of higher microbial quality than Mexican produce.

Anti-Bacterial Agents↗

PubMed2004

Vancomycin tolerance in enterococci.

BACKGROUND: Tolerance can be defined as the ability of bacteria to grow in the presence of high concentrations of bactericide antimicrobics, so that the killing action of the drug is avoided but the minimal inhibitory concentration (MIC) remains the same. We investigated vancomycin tolerance in the Enterococcus faecium and Enterococcus faecalis strains isolated from different clinical specimens. METHODS: Vancomycin was obtained from Sigma Chemical Co. We studied 100 enterococci strains. Fifty-six and 44 of Enterococcus strains were idendified as E. feacalis and E. faecium, respectively. To determine MICs and minimal bactericidal concentration (MBC), we inoculated strains from an overnight agar culture to Muller-Hinton broth and incubated them for 4-6 h at 37 degrees C with shaking to obtain a logarithmic phase culture. The inoculum was controlled by performing a colony count for each test. We determined MBC values and MBC/MIC ratios to study tolerance to vancomycin. Vancomycin tolerance was defined as a high MBC value and an MBC/MIC ratio > or =32. RESULTS: Fifty-six and 44 of the Enterococcus strains were identified as E. faecium and E. faecalis, respectively. Thirty-one E. faecium and 48 E. faecalis were found to be susceptible to vancomycin and these susceptible strains were included in this study. The MICs of susceptible strains ranged from < or =1 to 4 mg/l, the MBCs were > or =512 mg/l. Tolerance was detected in all E. faecalis and E. faecium strains. The standard E. faecalis 21913 strain also exhibited tolerance according to the high MBC value and the MBC/MIC ratio. We defined the tolerant strains as having no bactericidal effect and MBC/MIC > or =32. We found that a 100% tolerance was present in susceptible strains. CONCLUSIONS: One of the hypotheses for tolerance is that tolerant cells fail to mobilize or create the autolysins needed for enlargement and division. Our data suggests that tolerance may compromise glycopeptide therapy of serious enterococci infections. To add an aminoglycoside to the glycopeptide therapy unless MBCs are unavailable can be useful in the effective treatment of serious Enterococcus infections.

Agar↗

PubMed2002

Enterococcus faecium-related outbreak with molecular evidence of transmission from pigs to humans.

Between 24 July and 31 August 1998, thousands of domestic pigs died of hemorrhagic shock in three adjunct counties along the YangZi River in Jiangshu Province, China. From 28 July to 6 September 1998, 40 local farmers (36 males and 4 females, ages 23 to 78 years) were hospitalized with severe illness characterized by high fever, erythematous rash or petechiae, and profound lethargy after contact with sick pigs. Twelve (30%) of these patients died of respiratory failure and shock. Eleven bacterial isolates recovered from 11 blood and cerebrospinal fluid specimens collected from seven patients and two pigs were identified as Enterococcus faecium based on biochemical reactions and 16S rRNA gene sequence analysis. Both pig and human E. faecium isolates displayed indistinguishable antibiotic susceptibility and pulsed-field gel electrophoresis patterns. These data strongly suggest the spread of an outbreak of E. faecium-related sepsis from pigs to humans.

Adult↗

PubMed2006

Antimicrobial resistance and the mechanisms implicated in faecal enterococci from healthy humans, poultry and pets in Portugal.

Antimicrobial resistance and the mechanisms implicated were studied in 440 enterococci (227 Enterococcus faecium, 177 Enterococcus faecalis, 32 Enterococcus hirae and 4 Enterococcus durans) recovered from 220 faecal samples of healthy humans, poultry and pets in Portugal. Higher levels of resistance were detected for ampicillin, tetracycline, erythromycin and chloramphenicol in poultry isolates (10.5%, 97%, 87.5% and 16%, respectively) compared with human isolates (0%, 26%, 31.5% and 5%, respectively); intermediate levels of resistance for these antibiotics were found in pet isolates. Thirty-three per cent of the E. faecium isolates of poultry origin showed quinupristin/dalfopristin resistance. High-level resistance to gentamicin or streptomycin was detected in 1-7% of isolates in our series of enterococci. The aac(6')-aph(2''), aph(3')-IIIa, erm(B) and tet(M) genes were demonstrated in most of the gentamicin-, kanamycin-, erythromycin- and tetracycline-resistant isolates, respectively. The vat(E) gene was found in 39% of the quinupristin/dalfopristin-resistant E. faecium isolates of poultry origin.

Animals↗

PubMed2006

Antibiotic resistant fecal isolates of Enterococci among unselected patients outside the clinical sector: an epidemiological study from Southern Germany.

PURPOSE: The aim of the study was to assess the prevalence and determinants of antibiotic-resistant Enterococci in a large group of outpatients in Southern Germany. METHODS: Stool samples were collected from 497 unselected patients aged 40-75 years attending general practitioners. Enterococcus faecium (E. faecium) and Enterococcus faecalis (E. faecalis) were cultured and minimal inhibitory concentrations of antibiotics used inside and outside the clinical sector were tested. RESULTS: E. faecium and E. faecalis could be identified and cultured in 60 (12.4%) and 205 (41.2%) of the stool samples, respectively. Under non-selective culture conditions no vancomycin-resistant Enterococcus (VRE) isolate was found. Only E. faecium isolates showed resistance to fluoroquinolones, 40% were resistant to ciprofloxacin. The prevalences of E. faecium resistance to ampicillin and doxycycline were 3.3% and 13.3%, respectively, whereas 0.5% and 29.6% of the E. faecalis isolates were resistant to ampicillin and doxycycline, respectively. Antibiotic use during the last 3 months was significantly associated with antibiotic resistance (to either ampicillin, imipenem, or doxycycline) of E. faecalis isolates (OR: 2.9; CI: 1.2-6.8). CONCLUSIONS: Prevalences of resistance were generally lower than and patterns of resistance were quite different from previous investigations in the clinical setting. Recent antibiotic use was associated with increased colonization with resistant strains.

Adult↗