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PubMed2001

Post-antibiotic growth suppression of linezolid against Gram-positive bacteria.

The in vitro post-antibiotic effects (PAEs) of eight different concentrations of linezolid against Gram-positive cocci were investigated and the results analysed using the sigmoid E(max) model for mathematically modelling the PAE. Mean maximal linezolid PAEs against strains of Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium and Streptococcus pneumoniae were 2.2, 1.8, 2.8, 2.0 and 3.0 h, respectively. Resistance to methicillin (for the staphylococci), vancomycin (for the enterococci) and penicillin (for the pneumococci) had no effect on the duration of the PAE. Results of PAE testing support twice-daily dosing of linezolid in humans.

Acetamides↗

PubMed2005

Enumeration and speciation of enterococci found in marine and intertidal sediments and coastal water in southern California.

AIMS: To determine the levels and species distribution of enterococci in intertidal and marine sediments and coastal waters at two beaches frequently in violation of bacterial water standards. METHODS AND RESULTS: Faecal indicator bacteria were extracted from sediment and enumerated using membrane filtration. High levels of enterococci were detected in intertidal sediments in a seasonal river and near a storm drain outlet. Low levels were found in marine sediments at 10 m depths and in surf zone sand. Bacterial isolates presumptively identified as Enterococcus on mEI media were speciated. The predominant species found in both water and sediment included Enterococcus faecalis, Enterococcus faecium, Enterococcus hirae, Enterococcus casseliflavus and Enterococcus mundtii. A number of isolates (11-26%) from regulatory water samples presumptively identified as enterococci on mEI media were subsequently identified as species other than Enterococcus. At both study sites, the distribution of species present in water was comparable with those in sediments and the distribution of species was similar in water samples passing and exceeding bacterial indicator standards. CONCLUSIONS: High levels of Enterococcus in intertidal sediments indicate retention and possible regrowth in this environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Resuspension of enterococci that are persistent in sediments may cause beach water quality failures and calls into question the specificity of this indicator for determining recent faecal contamination.

California↗

PubMed2006

High-level vancomycin-resistant Staphylococcus aureus isolates associated with a polymicrobial biofilm.

Glycopeptides such as vancomycin are the treatment of choice for infections due to methicillin-resistant Staphylococcus aureus. This study describes the identification of high-level vancomycin-resistant S. aureus (VRSA) isolates in a polymicrobial biofilm within an indwelling nephrostomy tube in a patient in New York. S. aureus, Enterococcus faecalis, Enterococcus faecium, Micrococcus species, Morganella morganii, and Pseudomonas aeruginosa were isolated from the biofilm. For VRSA isolates, vancomycin MICs ranged from 32 to >128 microg/ml. VRSA isolates were also resistant to aminoglycosides, fluoroquinolones, macrolides, penicillin, and tetracycline but remained susceptible to chloramphenicol, linezolid, rifampin, and trimethoprim-sulfamethoxazole. The vanA gene was localized to a plasmid of approximately 100 kb in VRSA and E. faecium isolates from the biofilm. Plasmid analysis revealed that the VRSA isolate acquired the 100-kb E. faecium plasmid, which was then maintained without integration into the MRSA plasmid. The tetracycline resistance genes tet(U) and tet(S), not previously detected in S. aureus isolates, were identified in the VRSA isolates. Additional resistance elements in the VRSA isolate included a multiresistance gene cluster, ermB-aadE-sat4-aphA-3, msrA (macrolide efflux), and the bifunctional aminoglycoside resistance gene aac(6')-aph(2")-Ia. Multiple combinations of resistance genes among the various isolates of staphylococci and enterococci, including vanA, tet(S), and tet(U), illustrate the dynamic nature of gene acquisition and loss within and between bacterial species throughout the course of infection. The potential for interspecies transfer of antimicrobial resistance genes, including resistance to vancomycin, may be enhanced by the microenvironment of a biofilm.

Acetamides↗

PubMed1999

Characterization of a bacteriocin-like substance produced by a vaginal Lactobacillus salivarius strain.

A novel bacteriocin-like substance produced by vaginal Lactobacillus salivarius subsp. salivarius CRL 1328 with activity against Enterococcus faecalis, Enterococcus faecium, and Neisseria gonorrhoeae was characterized. The highest level of production of this heat-resistant peptide or protein occurred during the late exponential phase. Its mode of action was shown to be bactericidal. L. salivarius subsp. salivarius CRL 1328 could be used for the design of a probiotic to prevent urogenital infections.

Bacteriocins↗

PubMed1996

Antimicrobial-resistant pathogens in the 1990s.

Streptococcus pneumoniae, Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, and Klebsiella pneumoniae have become increasingly resistant to antimicrobial agents. This chapter reviews the epidemiology of this resistance, its detection in the laboratory, the mechanisms of resistance, and the options for therapy and infection control.

Anti-Bacterial Agents↗

PubMed1990

Minimum inhibitory concentrations and disk diffusion zone diameter for selected antibiotics against streptococci isolated from bovine intramammary infections.

The antimicrobial susceptibility to 11 antibiotics was determined of 358 streptococcal isolates representing six species was determined. All isolates were from milk samples obtained from clinical or subclinical cases of bovine mastitis. Agar disk diffusion zone diameters and minimum inhibitory concentrations were obtained for all isolates. Of the antibiotics tested that are available for mastitis therapy, cephalothin, penicillin, ampicillin, novobiocin, and erythromycin demonstrated acceptable activity against nonenterococcal streptococci, but only penicillin and ampicillin demonstrated moderate activity against Enterococcus faecalis. Enterococcus faecalis demonstrated substantial resistance to cephalothin, erythromycin, gentamicin, streptomycin, and tetracycline, while the nonenterococcal streptococci demonstrated substantial resistance to gentamicin, streptomycin, and tetracycline. Streptococcus uberis demonstrated greater antibiotic resistance than did Streptococcus dysgalactiae, while Aerococcus viridans demonstrated the greatest overall resistance of the nonenterococcal species.

Animals↗

PubMed1988

In vitro selection of bacteria resistant to LY146032, a new cyclic lipopeptide.

Isolates of Streptococcus pneumoniae, Enterococcus faecalis, Enterococcus faecium, and coagulase-positive and -negative staphylococci were investigated for their abilities, in vitro, to develop resistance to LY146032. Exposure of the organisms to incremental concentrations of LY146032 resulted in MICs 8- to 32-fold higher than those for the original isolates. After three passages on antibiotic-free medium, the high MICs were maintained for the coagulase-negative staphylococci and pneumococci, with a twofold decrease observed for the enterococci and a fourfold decrease observed for Staphylococcus aureus. The frequency of spontaneous emergence of resistance was highest with S. pneumoniae (1.2 X 10(-6) at 16 times the original MIC) and lowest with S. aureus (7.0 X 10(-10) at 8 times the original MIC). For bacteria For bacteria surviving time-kill studies MICs were also higher than were those for the original isolates. Exposure to LY146032 in vitro selected for strains with decreased susceptibilities to the antimicrobial agent. However, the emergence of resistance in vivo is unpredictable and can be evaluated only after prolonged clinical use of the drug.

Anti-Bacterial Agents↗

PubMed1995

Structure-activity relationship of new 2-substituted penem antibiotics.

The antibacterial activities of three new penems with 4-hydroxyprolinamide, 1-prolinamide and N-methyl-N-2-propionamide substituents, respectively, in position 2 and of their stereoisomers were examined against Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, Escherichia coli and Pseudomonas aeruginosa. All substitutes conferred a broad antibacterial spectrum on the penem moiety. Changes in stereoisomerism selectively improved the activity against E. coli, S. aureus or enterococci. The structure-activity relationships of each compound were discussed in relation to minimum inhibitory concentrations, penicillin-binding protein (PBP) affinity and outer membrane permeability coefficient in E. coli. In this microorganism, PBP 2 was the target for all compounds. Changes in stereoisomerism influenced the affinity for PBPs 1A/B and 2. All antibiotics easily permeated the outer membrane of E. coli and, within each group of compounds, the penetration rate correlated with the antibacterial activity.

Anti-Bacterial Agents↗

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↗

PubMed1995

Evaluation of Vitek and API 20S for species identification of enterococci.

The performance of the Vitek System and the API 20S for identifying enterococci to the species level was evaluated in comparison with a conventional reference test scheme. A total of 369 isolates originally derived from a sample from 97 medical centers were tested, and the percentage of correctly identified organisms was (Vitek/API): 97.6%/79.2%, 95.3%/91.2%, and 86.0%/20.7% for Enterococcus faecalis, Enterococcus faecium, and Enterococcus non-faecalis-non-faecium species, respectively. In addition, the predictive values for species identification of the results reported by the systems were 98.1% for Vitek and 85.9% for API. The Vitek System GPI card (software version > or = 8.1) was considered to be very acceptable for enterococci identification, with errors principally among the rare Enterococcus raffinosus isolates.

Bacteriological Techniques↗

PubMed1987

Role of immunoblotting in the diagnosis of culture negative and enterococcal endocarditis.

Serum samples from patients with endocarditis and septicaemia due to Enterococcus faecalis, Enterococcus faecium, Streptococcus bovis, and Streptococcus sanguis were immunoblotted against antigenic extracts from all four species. In E faecalis endocarditis there was a strong IgM response to E faecalis antigenic bands of 112, 88-90, and 45-47 Kd and a strong IgG response to 88-90 and 45-47 Kd bands. In E faecium endocarditis there was a pronounced IgG response to an E faecium band of 82-90 Kd. For S bovis endocarditis, there was a strong IgG response to several components of S bovis including bands of 66, 58, 52 and 4 Kd. For S sanguis, there was a strong IgG response to bands of 80-82, 76, 60 and 45 Kd. These patterns of antibody production were absent in patients with uncomplicated septicaemia and in controls. The delineation of these patterns enabled confirmation of the final diagnosis in seven patients initially suspected of having culture negative endocarditis.

Antibodies, Bacterial↗

PubMed1986

Dispersal of a plasmid-borne chloramphenicol resistance gene in streptococcal and enterococcal plasmids.

Plasmids coding for chloramphenicol resistance, five isolated from streptococci of groups A, B, and G, ten from enterococci (Enterococcus faecalis, Enterococcus faecium), and two from staphylococci, were tested for sequence homology with the chloramphenicol resistance gene of pIP501, a 30-kb plasmid originally isolated from a group B Streptococcus. The 6.3-kb HindIII fragment of pIP501, known to carry the chloramphenicol resistance gene, was cloned into pBR322. A 1.6-kb portion of the cloned fragment, which included most of the chloramphenicol resistance gene, was used as probe in DNA-DNA hybridization experiments. Sequence homology was detected between the probe and four of the streptococcal, seven of the enterococcal, and one of the staphylococcal plasmids. The absence of hybridization between this probe and one plasmid isolated from a group B Streptococcus, as well as three isolated from E. faecalis, indicated that there are at least two different plasmid-borne chloramphenicol resistance determinants in the streptococci and in the enterococci.

Chloramphenicol↗

PubMed2003

A comparison of the antimicrobial resistance patterns of gram-positive cocci isolated from community-private and university-affiliated hospitals from Puerto Rico.

The antimicrobial resistance patterns of 2,462 selected Gram-positive cocci obtained from three Community-Private Hospitals (CPH) and three University-Affiliated Hospitals (UAH) were evaluated utilizing the institutions' antimicrobial susceptibility reports for the year 2000. The objectives of this study were: 1) to evaluate the in vitro resistance to selected standard antibiotics of Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium and Streptococcus pneumoniae clinical isolates, and 2) to compare the antimicrobial resistance patterns between community-private (CPH) and university-affiliated hospitals (UAH). Staphylococcus aureus was the most common Gram-positive isolated organism in CPH (63.3%) followed by E. faecalis (31.0%). In UAH, the most prevalent cocci were E. faecalis (51.7%) followed by S. aureus (43.9%). Enterococcus faecium represented 2.3% and 4.4% of CPH and UAH isolates, respectively. Streptococcus pneumoniae represented 3.4% of the total Gram-positive isolates from CPH, no S. pneumoniae was reported in UAH. The antimicrobial susceptibility results showed that for Staphylococcus aureus there was a statistically significant higher resistance to methicillin and thrimethoprim sulfamethoxazole in UAH, while resistance to erythromycin was significantly higher in CPH. There was no difference in the resistance of S. aureus to other antimicrobial agents between hospitals groups. A statistically significant resistant to vancomycin was found between enterococcal isolates from UAH (43%) and CPH (12.7%). High-level aminoglycoside resistance (HLAR) was observed among UAH enterococcal isolates with E. faecium showing a higher resistance than E. faecalis, no data for HLAR in CPH could be obtained. For pneumococci 46% of CPH isolates were resistant to penicillin. In summary, there are important differences in the prevalence and antimicrobial resistance between the Gram-positive bacteria isolated from community and teaching hospitals.

Anti-Bacterial Agents↗

PubMed2001

Evaluation of an automated system for the identification and antimicrobial susceptibility testing of enterococci.

The performance of a new version of an automated system panel, the Positive Combo Panel Type 11 of MicroScan WalkAway 96 (WA96; Dade Behring) was evaluated and compared to that of reference methods for the identification and for antimicrobial susceptibility testing of the different enterococcal species. A total of 376 enterococcal isolates were tested. The MicroScan WA96 correctly identified 99.6% (266/267), 78.3% (18/23) and 68.6% (59/86) of Enterococcus faecalis, Enterococcus faecium and species other than E. faecalis and E. faecium, respectively. Although low probability of accurate identification was obtained for 37 (9.8%) strains, the system indicated that supplementary tests were necessary for precise identification of 8 (9.3%) among the 86 strains included in the non-faecalis/non-faecium group and of 3 (13.0%) among the E. faecium isolates. In comparison to the agar screening method, the percentage of agreement for detection of resistance markers by the automated system was 90.2% (37/41) for ampicillin, 90.6% (48/53) for high-level resistance to streptomycin (HLRS), 96.4% (80/83) for high-level resistance to gentamicin (HLRG), and 100% (14/14) for vancomycin. The results indicate that the MicroScan WA96 performed well for the identification of E. faecalis and typical E. faecium isolates, and for the detection of resistance to vancomycin and HLRG. However, the system still needs further improvement in order to provide reliable results for the characterization of the other enterococcal species, including atypical variants of E. faecium.

Autoanalysis↗

PubMed1997

Species identification of enterococci via intergenic ribosomal PCR.

Accurate species identification of enterococci has become important with the wide prevalence of acquired vancomycin resistance and the presence of less epidemiologically important, inherently vancomycin-resistant enterococci. Using a collection of enterococcal strains, we found that PCR amplification of the intergenic spacer (ITS-PCR) between the 16S and 23S rRNA genes can produce amplicon profiles characteristic of the enterococcus examined. The species examined were group I enterococci (Enterococcus avium, Enterococcus raffinosus, Enterococcus malodoratus, and Enterococcus pseudoavium), group II enterococci (Enterococcus faecalis, Enterococcus faecium, Enterococcus casseliflavus, Enterococcus mundtii, and Enterococcus gallinarum), and group III enterococci (Enterococcus durans and Enterococcus hirae). The enterococcal species in group I, as well as E. faecalis and two strains of E. hirae, were similar and therefore had to be differentiated from each other by Sau3A restriction digests. This produced patterns characteristic of each of these species. The remaining group II and group III enterococcal species produced amplicons characteristic of a particular species except E. gallinarum. The PCR products from E. gallinarum displayed strain-to-strain heterogeneity in the number and size of amplicons. To further test the utility of this technique, 11 phenotypically aberrant strains which had been assigned species identification based on Facklam and Collins-type strain reactions (R.R. Facklam and M.D. Collins, J. Clin. Microbiol. 27:731-734, 1989) were subjected to ITS-PCR. ITS-PCR of the phenotypically aberrant strains identified six strains with reactions consistent with those of type strains. However, five strains were characterized as follows: two strains originally identified as E. mundtii were identified by ITS-PCR as E. casseliflavus, one strain originally identified as E. raffinosus was identified by ITS-PCR as E. durans, one strain originally identified as E. hirae was identified by ITS-PCR as E. faecium [corrected]. We conclude that amplification of the intergenic 23S and 16S rRNA gene regions of enterococci provides a reliable technique for species identification of enterococci.

Bacterial Typing Techniques↗

PubMed2000

Identification of Enterococcus species and phenotypically similar Lactococcus and Vagococcus species by reverse checkerboard hybridization to chaperonin 60 gene sequences.

Data from four recent studies (S. H. Goh et al., J. Clin. Microbiol. 36:2164-2166, 1998; S. H. Goh et al., J. Clin. Microbiol. 34:818-823, 1996; S. H. Goh et al., J. Clin. Microbiol. 35:3116-3121, 1997; A. Y. C. Kwok et al., Int. J. Syst. Bacteriol. 49:1181-1192, 1999) suggest that an approximately 600-bp region of the chaperonin 60 (Cpn60) gene, amplified by PCR with a single pair of degenerate primers, has utility as a potentially universal target for bacterial identification (ID). This Cpn60 gene ID method correctly identified isolates representative of numerous staphylococcal species and Streptococcus iniae, a human and animal pathogen. We report herein that this method enabled us to distinguish clearly between 17 Enterococcus species (Enterococcus asini, Enterococcus rattus, Enterococcus dispar, Enterococcus gallinarum, Enterococcus hirae, Enterococcus durans, Enterococcus cecorum, Enterococcus faecalis, Enterococcus mundtii, Enterococcus casseliflavus, Enterococcus faecium, Enterococcus malodoratus, Enterococcus raffinosus, Enterococcus avium, Enterococcus pseudoavium, Enterococcus new sp. strain Facklam, and Enterococcus saccharolyticus), and Vagococcus fluvialis, Lactococcus lactis, and Lactococcus garvieae. From 123 blind-tested samples, only two discrepancies were observed between the Facklam and Collins phenotyping method (R. R. Facklam and M. D. Collins, J. Clin. Microbiol. 27:731-734, 1989) and the Cpn60 ID method. In each case, the discrepancies were resolved in favor of the Cpn60 ID method. The species distributions of the 123 blind-tested isolates were Enterococcus new sp. strain Facklam (ATCC 700913), 3; E. asini, 1; E. rattus, 4; E. dispar, 2; E. gallinarum, 20; E. hirae, 9; E. durans, 9; E. faecalis, 12; E. mundtii, 3; E. casseliflavus, 8; E. faecium, 25; E. malodoratus, 3; E. raffinosus, 8; E. avium, 4; E. pseudoavium, 1; an unknown Enterococcus clinical isolate, sp. strain R871; Vagococcus fluvialis, 4; Lactococcus garvieae, 3; Lactococcus lactis, 3; Leuconostoc sp., 1; and Pediococcus sp., 1. The Cpn60 gene ID method, coupled with reverse checkerboard hybridization, is an effective method for the identification of Enterococcus and related organisms.

Bacterial Typing Techniques↗

PubMed2006

Activity and expression of a virulence factor, gelatinase, in dairy enterococci.

In order to understand the virulence potential of dairy enterococci, 35 isolates from raw ewe's milk and traditionally fermented cheeses, identified as Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, Enterococcus dispar and Enterococcus hirae, were screened for their capacity to produce gelatinase and for the presence of the genes gelE, sprE, fsrA, fsrB and fsrC. Studies correlating gelatinase production with maintenance and subculture of the isolates in the Laboratory environment, and growth in different media were performed. These studies were conducted with two dairy isolates identified as E. faecalis and E. durans, and one clinical isolate, E. faecalis OG1-10. RT-PCR was used for detection of transcripts of the above mentioned genes. Results demonstrated that the virulence factor gelatinase is disseminated among the genus Enterococcus and that dairy isolates are capable of producing gelatinase at comparable levels with clinical isolates, although this capacity is easily lost during conservation by freezing in the laboratory. Therefore, gelatinase production potential of dairy enterococci may be underestimated. The gene gelE was present in all studied isolates. The same was observed for the fsr operon, either complete or incomplete, revealing that the gelatinase genetic determinants, so far only described in E. faecalis, are a common trait in the genus. This work describes for the first time the detection of the complete Fsr-GelE operon in other species than E. faecalis, namely E. faecium and E. durans. The loss of expression of this virulence factor under laboratory culture conditions correlated with the loss of one or more genes of the regulatory fsr operon, although the gene gelE was maintained, demonstrating that a complete fsr operon is required for a positive GelE phenotype. Independent of the detection of any gelatinase activity, if both gelE and the complete fsr operon are present in the cell, all genes are transcribed, as revealed by RT-PCR, suggesting that regulation of gelatinase activity can also be post-transcriptional. The silent behavior of gelE was only observed in E. faecalis, but not in E. durans, suggesting different modulation mechanisms of gelatinase activity in these two species. Overall, these findings reopen the issue of food safety of enterococci and reinforce the need to further study the mechanisms responsible for triggering the virulence factor gelatinase in non-pathogenic enterococcal environmental isolates.

Animals↗

PubMed1992

In vitro evaluation of BAY Y3118, a new full-spectrum fluoroquinolone.

BAY Y3118, 1-cyclopropyl-7-(2,8-diazabicyclo[4.3.0]non-8-yl)-6-fluoro-8- chloro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid hydrochloride, is a new fluoroquinolone with antibacterial activity against an expanded spectrum of species including Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium, Streptococcus pneumoniae, Streptococcus pyogenes, and also anaerobes such as Bacteriodes fragilis and Clostridium perfringens. MIC90s for S. aureus, S. epidermidis, E. faecalis, and S. pneumoniae clinical isolates were 0.125, 0.25, 0.125 and 0.25 micrograms/ml, respectively. Against methicillin- and/or quinolone-resistant S. aureus, MIC50 levels of BAY Y3118 were 10- to 100-fold lower than those of tosufloxacin, sparfloxacin, or ciprofloxacin. The potency of BAY Y3118 against all members of the Enterobacteriaceae generally was equal to or 2-fold greater than that of ciprofloxacin or tosufloxacin. BAY Y3118 was also highly active against Haemophilus influenzae, Moraxella catarrhalis, Acinetobacter spp. and Pseudomonas aeruginosa. Increasing inoculum concentrations had a minimal effect on MIC determinations. The drug was determined to be bactericidal based upon reference MBCs and time-kill curves. From the results presented here, it was concluded that this new compound surpasses other known 4-quinolones both in spectrum and activity and that its further evaluation by in vitro, in vivo, and clinical studies seems warranted.

Anti-Infective Agents↗