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PubMed1994

Faecal carriage and nosocomial spread of vancomycin-resistant Enterococcus faecium.

Eight clinical isolates of vancomycin-resistant Enterococcus faecium (VRE) were obtained from four renal and four other in-patients within an 11 week period during 1992. Characterisation of the isolates by restriction enzyme analysis with Sal I and rRNA gene restriction patterns (ribotyping) showed them to be clonally related. During the next 3 months an additional 14 VRE were isolated from hospital patients, nine of which were indistinguishable by ribotyping from the strain associated with the outbreak. An epidemiological survey was instigated in order to determine the level of carriage of this VRE. A total of 354 stool specimens was screened using a highly selective enrichment broth. VRE were detected in the stools of 11/73 (15%) of renal patients, 5/97 (5%) of other hospital patients and 3/184 (2%) of patients based in the community. Of the 25 stool isolates that were further characterised by ribotyping, 17 were indistinguishable from the outbreak strain. The remaining eight isolates gave seven different patterns. Patients harbouring the outbreak strain stayed in hospital significantly longer and had received more antibiotic treatment, for longer, than those patients from whom other VRE had been isolated. There was no significant difference in vancomycin or cephalosporin usage between the two groups of patients. Ribotyping showed there to be a number of clones of VRE carried by patients and that one of these clones was especially prevalent and has been responsible for the outbreak of infection in the renal unit. The technique also showed the presence of different VRE in general practice patients suggesting they are not just a hospital phenomenon.

Adult↗
PubMed1994

In-vitro postantibiotic effect of sparfloxacin and ciprofloxacin against Pseudomonas aeruginosa and Enterococcus faecalis.

The effect of concentration and exposure time on the postantibiotic effect (PAE) of sparfloxacin and ciprofloxacin against Pseudomonas aeruginosa Psa-1 and Enterococcus faecalis SD-63 was evaluated by the colony counting method using centrifugation to remove the antibiotic. The microorganisms were exposed for 15, 30 and 60 min to drug concentrations ranging from 1 x MIC to 31 x MIC. The PAE was calculated as the difference in time required by test and control cultures to increase 1 log10 after the drug was removed. The MICs of sparfloxacin for P. aeruginosa and E. faecalis were 0.50 mg/L and 0.25 mg/L, respectively, whereas the MICs of ciprofloxacin were 0.25 mg/L for P. aeruginosa and 0.50 mg/L for E. faecalis. PAEs increased as a function of concentration and exposure time. Against E. faecalis no point of maximal response was reached. On the contrary, against P. aeruginosa this point was reached at 8 x MIC of ciprofloxacin and 16 x MIC of sparfloxacin PAE values of sparfloxacin for P. aeruginosa and E. faecalis ranged from 7 to 96 min and from 0 to 112 min, respectively, and those of ciprofloxacin from 8.5 to 82.33 min and from 0 to > 136 min, respectively. Significant PAEs for P. aeruginosa were obtained after 60 min exposure at 4 x MIC (62.6 min) and 2 x MIC (52.6 min) of ciprofloxacin and sparfloxacin, respectively, and at 8 x MIC (81.5 min) and 16 x MIC (81.6 min) for E. faecalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Infective Agents↗
PubMed1994

Treatment of experimental endocarditis due to multidrug resistant Enterococcus faecium with ciprofloxacin and novobiocin.

The effectiveness of ciprofloxacin and/or novobiocin therapy was assessed for experimental endocarditis caused by three strains of Enterococcus faecium resistant to ampicillin, vancomycin, and aminoglycosides. Rabbits with endocarditis caused by two of the strains had a significant decrease in bacterial counts in vegetations when treated with both antibiotics. Further studies using combination therapy with ciprofloxacin plus novobiocin for multidrug resistant strains of E. faecium are warranted.

Animals↗
PubMed1995

Detection of high- and moderately high-level resistance to gentamicin and streptomycin in Enterococcus faecium by a disc diffusion method.

We evaluated an agar disc diffusion test for the detection of high-level (> or = 2000 mg/L) and moderately high-level resistance to gentamicin (MIC, > or = 128- < or = 1024 mg/L) and streptomycin (MIC, > or = 256- < or = 1024 micrograms/ml) with 70 clinical isolates of Enterococcus faecium. Results obtained using disks containing 120 micrograms gentamicin and 300 micrograms streptomycin were compared with MICs determined by an agar dilution method. Based on the scattergrams, the closest zone diameter correlations with MIC breakpoints were as follows: susceptible, > or = 16 mm; and resistant, < or = 10 mm, for both streptomycin and gentamicin. No major or very major errors were found with either aminoglycoside using these values. We conclude that agar disk diffusion test can be used to accurately detect high-level or moderately high-level gentamicin and streptomycin resistance in E. faecium.

Anti-Bacterial Agents↗
PubMed1995

Ampicillin plus ciprofloxacin therapy of experimental endocarditis caused by multidrug-resistant Enterococcus faecium.

The combination of ampicillin and ciprofloxacin displayed bactericidal in-vitro activity against two strains of Enterococcus faecium which were highly resistant to ampicillin, vancomycin, and aminoglycosides. This antibiotic combination was used to treat rabbits with experimental endocarditis caused by these strains. Although a significant decrease in vegetation bacterial counts occurred with one strain, the degree of killing did not approach that of penicillin with an aminoglycoside against susceptible enterococci.

Ampicillin↗
PubMed1995

Mechanism of sulphadiazine enhancement of trimethoprim activity against sulphadiazine-resistant Enterococcus faecalis.

Sulphadiazine had little or no antibacterial effect against three strains of Enterococcus faecalis (MICs of above 3600 mg/L) but it caused approximately six-fold increases in bacterial uptake of trimethoprim, increased release of bacterial ATP and produced ultrastructural damage to both the trimethoprim resistant E. faecalis 463 and the trimethoprim sensitive NCTC 5957. MICs of trimethoprim were 0.6, 0.8 and 76.8 mg/L for E. faecalis NCTC 775, NCTC 5957 and 463 respectively. When log phase E. faecalis 463 and NCTC 5957 were grown for 4 h in trimethoprim 56 and 0.6 mg/L plus sulphadiazine 320 and 100 mg/L respectively there was an approximate ten-fold and nine-fold increase in uptake of sulphadiazine and a two-fold increase in leakage of ATP. Trimethoprim caused more damage to the cell wall and cytoplasmic membrane than sulphadiazine but the combination of sulphadiazine plus trimethoprim caused the most cell damage. The increased activity observed with the combination seems very likely to have resulted from the increased uptakes of the antibacterials, which in turn had resulted from the cell wall damage and consequent increased cell permeability caused by each antibacterial. It is proposed that a markedly subinhibitory concentration of sulphadiazine enhanced the antibacterial activity of trimethoprim against all three strains of E. faecalis by this mechanism.

Adenosine Triphosphate↗
PubMed1996

Treatment of experimental endocarditis due to multidrug-resistant Enterococcus faecium with clinafloxacin and penicillin.

Clinafloxacin, a new quinolone antibiotic with enhanced activity against Gram-positive bacteria, has demonstrated in-vitro activity against multidrug-resistant Enterococcus faecium, particularly when combined with penicillin. Rabbits with experimental endocarditis due to a multidrug-resistant strain of E. faecium were treated with clinafloxacin and/or penicillin. After three days of therapy, significant reduction of bacterial concentrations were found in vegetations, kidneys, and spleens of animals treated with clinafloxacin. The combination of clinafloxacin and penicillin was significantly better in reducing vegetation bacterial concentrations compared to the other groups (-4.4 log10 cfu/g compared with control). Serum levels of clinafloxacin consistently exceeded the MIC of the strain, and clinafloxacin-resistant isolates could not be detected. Clinafloxacin demonstrated promising activity in vivo against multidrug-resistant E. faecium, and further studies are warranted.

Animals↗
PubMed1996

Treatment of experimental endocarditis caused by multidrug resistant Enterococcus faecium with ramoplanin and penicillin.

Antibiotic resistant strains of enterococci are being isolated with increasing frequency. Effective treatment of infections caused by Enterococcus faecium resistant to ampicillin, vancomycin and aminoglycosides has not been established. We studied the activity of ramoplanin, a new lipoglycopeptide antibiotic, against two strains of multidrug resistant E. faecium. In time kill studies, ramoplanin was bactericidal against both strains, but not in the presence of 50% serum. The combination of ramoplanin and penicillin was bactericidal even in the presence of serum. In rabbits with experimental endocarditis neither penicillin nor ramoplanin significantly reduced vegetation colony counts when given alone, although ramoplanin significantly reduced spleen and kidney bacterial counts of both strains. The combination of ramoplanin plus penicillin resulted in a significant reduction of vegetation bacterial counts (-3.2 and -3.7 log10 cfu/g for strains VA3 and MMC3, respectively, P < 0.01). All spleen cultures and 9 out of 10 kidney cultures from each strain were sterile following combination therapy. While ramoplanin will not be available for parenteral therapy, further research into the development of other lipoglycopeptide antibiotics is warranted.

Animals↗
PubMed1996

Penicillin-binding protein 5 as an inhibitory target of cefozopran in Enterococcus faecalis.

The concentration of cefozopran which inhibits binding of [14C]benzylpenicillin to penicillin-binding protein (PBP) 5 of Enterococcus faecalis TN2OO5 by 50% was 11 mg/L, and its MIC was 12.5 mg/L. Ceftazidime and cefmenoxime, which were inactive at 100 mg/L, showed no affinity for PBP 5 at this concentration. Ampicillin, benzylpenicillin and imipenem showed higher affinity for PBPs 3/4 and PBP 5 than cefozopran, and their MICs were lower than that of cefozopran. No correlation between MICs of the test compounds and the affinity for PBP 1, 2 or 6 was found. These results suggest that cefozopran exhibits antimicrobial activity against E. faecalis TN2OO5 by binding to PBP 5.

Anti-Bacterial Agents↗
PubMed1996

Brodimoprim synergy against Enterococcus faecalis evaluated in vitro.

Combinations of either brodimoprim or trimethoprim plus either carbenicillin, gentamicin, ciprofloxacin or rifampicin showed synergy at sub-inhibitory concentrations against both Enterococcus faecalis NCTC 5957 and 775. Brodimoprim alone and in combination showed greater antibacterial activity against both strains of E. faecalis than trimethoprim. MBCs of brodimoprim and trimethoprim were 14.4 and 25.6 mg/L for E. faecalis NCTC 5957 and 7.2 and 12.8 mg/L for E. faecalis NCTC 775. Combinations of either brodimoprim or trimethoprim plus the other antibacterial agents, except gentamicin and dibromopropamidine isethionate, were bactericidal at achievable plasma concentrations. Viable count determinations of cultures of both test organisms in the presence of 3/4 of the MIC of each of the four antibiotics and the two antifolates alone and combinations of each antibiotic with either brodimoprim or trimethoprim indicated that only the combinations prevented recovery and regrowth of the cultures over 24 h. The ATP released from cultures of both strains of E. faecalis treated with brodimoprim and trimethoprim at the same concentrations was approximately 1.5 times greater with brodimoprim than with trimethoprim. Combinations of 3/4 of the MIC of each of the antibiotics in combination with 3/4 of the MIC of brodimoprim against cultures of both strains of E. faecalis resulted in greater release of ATP than occurred with equivalent trimethoprim combinations. It is postulated that the increased activities observed with the brodimoprim combinations resulted from an effect of brodimoprim on the bacterial cell permeability control. These results indicate that both brodimoprim and trimethoprim offer potential benefits for use with either carbenicillin, gentamicin, ciprofloxacin or rifampicin for the treatment of E. faecalis infections.

Anti-Bacterial Agents↗
PubMed1997

Therapeutic effects of cefozopran against experimental mixed urinary tract infection with Enterococcus faecalis and Pseudomonas aeruginosa in mice.

The therapeutic activity of cefozopran, a new semisynthetic parenteral cephalosporin, was compared with those of ceftazidime, ampicillin, imipenem/cilastatin and ofloxacin against an ascending mixed urinary tract infection induced in mice with Enterococcus faecalis TN2005 and Pseudomonas aeruginosa P9. Cefozopran significantly reduced viable cell counts of both organisms in the kidneys. Ceftazidime, imipenem/cilastatin and ofloxacin were active against only P. aeruginosa, and ampicillin was active against only E. faecalis.

Ampicillin↗
PubMed1997

Molecular typing of Enterococcus faecalis strains resistant to high levels of gentamicin and isolated in Romania.

Sixteen Enterococcus faecalis strains resistant to high levels of gentamicin, 15 of which were isolated in the same year in a Romanian hospital, harboured conjugative gentamicin resistance (Gm(r)) plasmids ranging from 55 to 85 kilobases. On the basis of restriction enzyme and DNA-DNA hybridization profiles of these plasmids, as well as of chromosomal SmaI macrorestriction and Tn916 hybridization patterns, clonal relationship was established for seven strains whereas the other strains were considered to be independent. Nine and seven of the Gm(r) plasmids carried Tn4001-like and Tn4001-truncated structures, respectively; the latter structures were truncated in the right-hand flanking extremity of the element.

Chromosomes, Bacterial↗
PubMed1997

Influence of gentamicin dosing interval on the efficacy of penicillin-containing regimens in experimental Enterococcus faecalis endocarditis.

The influence of the gentamicin dosing regimen was studied in experimental Enterococcus faecalis endocarditis. After inoculation, animals received penicillin, or penicillin plus once-daily gentamicin, or penicillin plus thrice-daily gentamicin, or no treatment. After the treatment period, bacterial densities within the vegetations (mean +/- SEM) were 6.06 +/- 0.30, 5.42 +/- 0.29, 4.98 +/- 0.10 and 9.97 +/- 0.16 log cfu/g for the four groups. All regimens produced significant reductions in bacterial density when compared with controls; penicillin plus thrice-daily gentamicin resulted in a significant difference from penicillin alone. Although once-daily regimens have proved effective in trials involving other organisms, such regimens do not appear to be so optimal for the treatment of enterococcal endocarditis.

Animals↗
PubMed1997

The effect of antibiotic exposure on adherence to neutrophils of Enterococcus faecium resistant to phagocytosis.

Many clinical isolates of Enterococcus faecium are resistant to neutrophil-mediated phagocytosis and killing. As antibiotic exposure may alter bacterial surface properties and promote phagocytosis, we used a fluorescence microscopy assay to examine the effect of antibiotic pretreatment on the resistance to phagocytosis of six strains of E. faecium. Using two antimicrobial agents with good in-vitro activity against E. faecium, namely quinupristin/ dalfopristin and sparfloxacin, we found that exposure to quinupristin/dalfopristin at concentrations both below and above the MIC promoted bacterial adherence to neutrophils (PMNs) for all of three strains of vancomycin-susceptible E. faecium, while sparfloxacin was similarly effective in two of these three strains. In contrast, neither antibiotic was effective in promoting PMN adherence for three vancomycin-resistant strains of E. faecium. The variability amongst strains in response to antibiotic exposure suggests that either the mechanisms of resistance to phagocytosis, or its regulation, may be different amongst different strains of E. faecium.

Anti-Bacterial Agents↗
PubMed1997

Effect of quinupristin/dalfopristin on the outcome of vancomycin-resistant Enterococcus faecium bacteraemia: comparison with a control cohort.

Serious infection with vancomycin-resistant Enterococcus faecium (VREF) strains has no proven effective antimicrobial therapy. We compared the clinical and bacteriological outcomes of 20 patients with VREF bacteraemia treated with quinupristin/dalfopristin (RP 59500), an investigational streptogramin, with a historical cohort of 42 patients with VREF bacteraemia treated with other agents. Quinupristin/dalfopristin demonstrated in-vitro bacteriostatic activity against all 20 initial VREF blood isolates (MIC range 0.03-0.50 mg/L) by macrobroth dilution. The clinical characteristics of both groups were comparable for major outcome-dependent variables. There were five cases of recurrent VREF bacteraemia in the quinupristin/dalfopristin-treated cohort and 21 in the controls (P = 0.11); persistence of VREF at the primary site was found in six and 18 of the evaluable patients with follow-up cultures in these two cohorts (P = 0.06). In-hospital mortality was high in both groups: 65% in the quinupristin/dalfopristin group and 52% in the control group; however, VREF-associated mortality was significantly lower in the quinupristin/dalfopristin group (five and 17 respectively; P = 0.05). Follow-up susceptibility testing of five VREF isolates in the quinupristin/ dalfopristin group did not demonstrate resistance to quinupristin/dalfopristin. Quinupristin/ dalfopristin may be a useful agent for the therapy of serious VREF infection. Further clinical investigations are warranted to confirm or refute its clinical efficacy.

Adult↗
PubMed1997

Bactericidal and inhibitory activity of quinupristin/dalfopristin against vancomycin- and gentamicin-resistant Enterococcus faecium.

There is a need for new agents, or combinations of agents, for the treatment of infections caused by vancomycin- and gentamicin-resistant Enterococcus faecium (VGREF) that may be resistant to all available antimicrobial agents. The early in-vitro activity of quinupristin/dalfopristin (30:70)--an injectable streptogramin--encouraged us to test this agent against VGREF. By broth dilution, the MICs of quinupristin/dalfopristin against 38 isolates of VGREF ranged from 0.06 mg/L to 2.0 mg/L (mode 0.12 mg/L). The addition of 0.5 mg/L of ciprofloxacin significantly reduced the modal MIC of quinupristin/dalfopristin to 0.015 mg/L (P = 5.75 x 10(-8)). Although the addition of 8.0 mg/L of teicoplanin or 4 mg/L of tetracycline did not significantly reduce the modal MIC, the lowest concentration of the MIC range was reduced from 0.06 to 0.015 mg/L. In broth, quinupristin/dalfopristin had slow bactericidal activity against the four strains tested over 48 h, with a 1-2 log10 cfu/mL reduction after 24 h in > 1 mg/L of quinupristin/dalfopristin for two strains and > 8 mg/L for the two other strains. A mixture of quinupristin/dalfopristin in a 70:30 ratio was more bactericidal: against one of the four strains 4-32 mg/L of the combination produced a further 0.5-1.0 log10 reduction in cfu/mL after 24 h and there was a reduction of 6.0 log10 cfu/mL after 48 h for another. By ultracentrifugation, the binding of 32 mg/L quinupristin/dalfopristin to human plasma protein was 90%, and in plasma broth, 32 mg/L of quinupristin/dalfopristin maintained bacteriostatic but not bactericidal activity. There is some useful synergy with ciprofloxacin and tetracycline, and the activity of quinupristin/dalfopristin may be enhanced against some strains by reversing the concentrations of its two components, quinupristin and dalfopristin, as that may occur in vivo.

Anti-Bacterial Agents↗
PubMed1997

Synergic activity of vancomycin-quinupristin/dalfopristin combination against Enterococcus faecium.

Clinical specimens were cultured, and the strains identified by the Vitek system as Enterococcus faecium were characterized by their DNA. The MIC vancomycin, quinupristin/dalfopristin and teicoplanin for each isolate was determined. Ten vancomycin-sensitive and ten vancomycin-resistant strains of E. faecium were tested. Quinupristin/dalfopristin at 0.25 x MIC and vancomycin at 0.5 x MIC separately as well as in combination were added to Trypticase Soy Broth tubes inoculated with a 24 h culture. The results obtained by determining cfu at 2, 4, 8, 12 and 24 h indicated that the combination of subinhibitory concentrations of quinupristin/dalfopristin plus vancomycin produced after 24 h, in vancomycin-resistant strains, a consistent degree of synergy. Synergy was observed up to only 12 h when similar combinations were employed for vancomycin-sensitive strains. Vancomycin-sensitive strains tended to be slightly less susceptible to quinupristin/dalfopristin than vancomycin-resistant strains.

Colony Count, Microbial↗
PubMed1997

In-vitro studies of the activity of glycopeptide combinations against Enterococcus faecalis biofilms.

Perfused biofilms of Enterococcus faecalis reached a pseudo-steady state, with respect to bioburden and the numbers of cells liberated within the perfusates. Biofilm growth rate was slow (approximately 0.006 doublings/h) relative to batch culture (approximately 0.01 doublings/h). MICs were determined for vancomycin (0.12 mg/L) and teicoplanin (1.2 mg/L) in batch culture. Steady-state biofilms (24 h and 48 h) were perfused continuously for 96 h with medium containing antibiotic at 4 X MIC. Susceptibility was assessed as cfu in the perfusate, indicating growth inhibition, and as cfu for the parent biofilm. Vancomycin at these levels had little or no effect on either parameter, whilst teicoplanin produced a temporary (30 h) reduction in growth rate (99.99% for 24 h biofilms, 50% for 48 h biofilms). Antibiotic concentrations were raised to therapeutic (trough) levels (vancomycin, 5 mg/L; teicoplanin, 12 mg/L) and applied continuously to 24 h old biofilms. Neither agent affected viability of the biofilm over 96 h. Biofilm growth rate, however, was decreased markedly over the first 8-10 h of antibiotic treatment and was maintained at the reduced level for approximately 40 h. Thereafter growth of the biofilms gradually returned to pre-exposure levels. The pattern of recovery was different for the two agents suggesting that different mechanisms might be involved. Accordingly biofilms were exposed to successive and concurrent 24 h treatments with vancomycin (5 mg/L) and teicoplanin (12 mg/L). This led not only to a further 2-3 log reduction in the growth rate but also to a 3 log reduction in the viability of the parent biofilm. Such synergy between the glycopeptide agents might have therapeutic implications for the treatment of E. faecalis infection.

Anti-Bacterial Agents↗