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PubMed1997

Comparative in-vitro activity of quinupristin/dalfopristin against Enterococcus spp.

The in-vitro activity of quinupristin/dalfopristin against Enterococcus spp. was compared with that of amoxycillin, vancomycin, telcoplanin and erythromycin. The susceptibility of 106 vancomycin-susceptible Enterococcus faecalis, 92 vancomycin-susceptible Enterococcus faecium and 14 vancomycin-resistant enterococci (VRE) was tested. Only one strain of vancomycin-susceptible E. faecium was not susceptible to < or = 0.5 mg/L quinupristin/dalfopristin; this strain required 4 mg/L. All strains of E. faecalis were inhibited by < or = 8 mg/L quinupristin/dalfopristin and all VRE strains were inhibited by < or = 2 mg/L. In contrast, teicoplanin and vancomycin showed inhibitory activity against E. faecalis and E. faecium but not against VRE. Amoxycillin was active against E. faecalis but not usually against E. faecium and showed variable activity against VRE; 38% of E. faecalis, 84% of E. faecium and 80% of VRE strains were resistant to erythromycin. The bactericidal activity of quinupristin/dalfopristin against E. faecium exceeded that of the comparator drugs as judged by MIC:MBC ratios and killing curves. The MBC99 of quinupristin/dalfopristin determined by a microdilution broth technique was < or = 1 mg/L for E. faecium. Four of the five strains of vancomycin-susceptible E. faecium and three of the five VRE strains tested with time-kill curves showed a > or = 2 log reduction in viable count after exposure to quinupristin/dalfopristin for 6 h.

Amoxicillin↗
PubMed1996

Emerging resistance in clinically important gram-positive cocci.

In the first half of the decade of the 1990s, we in the United States have seen the emergence and escalation of substantial antimicrobial resistance in medically important gram-positive cocci. The incidence of methicillin resistance of Staphylococcus aureus continues to increase (now 18%), resulting in many more isolates that are multiply resistant; all S aureus isolates are still susceptible to vancomycin. Enterococci, particularly Enterococcus faecium, have increasingly developed resistance to penicillin, gentamicin, streptomycin, and vancomycin (the last plasmid-mediated). More than a fourth of Streptococcus pneumoniae strains are now resistant to penicillin, and these strains tend to be multiply resistant, including to cephalosporins and macrolides.

Drug Resistance, Microbial↗
PubMed1993

In vitro activity of RP59500, an injectable streptogramin antibiotic, against vancomycin-resistant gram-positive organisms.

The in vitro activity of RP59500, a streptogramin antibiotic, against 146 clinical isolates of vancomycin-resistant gram-positive bacteria was examined. Five strains of the species Enterococcus casseliflavus and Enterococcus gallinarum, for which the MIC of vancomycin was 8 micrograms/ml, were also studied. Twenty-eight vancomycin-susceptible strains of Enterococcus faecalis and Enterococcus faecium were included for comparison. The drug was highly active against Leuconostoc spp., Lactobacillus spp., and Pediococcus spp. (MICs, < or = 2 micrograms/ml). RP59500 was more active against vancomycin-susceptible strains of E. faecium than E. faecalis (MICs for 90% of the strains [MIC90s], 1.0 versus 32 micrograms/ml). Vancomycin-resistant strains of E. faecalis were as resistant to RP59500 as vancomycin-susceptible strains (MIC90, 32 micrograms/ml), but some vancomycin-resistant E. faecium strains were relatively more resistant to the new agent (MIC90, 16; MIC range, 0.5 to 32 micrograms/ml) than were vancomycin-susceptible organisms of this species.

Drug Resistance, Microbial↗
PubMed2003

Multiple antibiotic resistance gene transfer from animal to human enterococci in the digestive tract of gnotobiotic mice.

It has been proposed that food animals represent the source of glycopeptide resistance genes present in enterococci from humans. We demonstrated the transfer of vanA and of other resistance genes from porcine to human Enterococcus faecium at high frequency in the digestive tract of gnotobiotic mice. Tylosin in the drinking water favored colonization by transconjugants.

Animals↗
PubMed1992

High-level aminoglycoside resistance in enterococci.

In recent years enterococci have been isolated with increasing frequency in association with serious infections. Suitable therapy for empirical treatment can only be chosen on the basis of susceptibility studies. The synergistic effects obtained by the combination of aminoglycosides with penicillin or vancomycin disappear in strains that show high level resistance (HLR) to the former. This highlights the importance of correct identification of the species of Enterococcus (especially Enterococcus faecium, a particularly resistant species), and of studies designed to examine HLR in severe infections. The preferred methods are dilution in solid or liquid medium with 2,000 micrograms of aminoglycoside per ml, or diffusion in solid medium from discs impregnated with 120 micrograms of gentamicin (which also predicts the microorganism's susceptibility to tobramycin and netilmicin) or kanamycin (which also predicts the response to amikacin), and 300 micrograms of streptomycin, for Enterococcus faecalis. The reliability of automated systems for the prediction of HLR to aminoglycosides has yet to be assessed.

Anti-Bacterial Agents↗
PubMedDate not supplied

Neonatal bacteremia due to high level aminoglycoside resistant (HLAR) enterococci.

A study was conducted to determine the drug resistance pattern of enterococci isolated from cases of neonatal bacteremia. A total of 41 strains of enterococci were isolated of which 35 (85.4%) were Enterococcus faecalis and 6 (14.6%) were Enterococcus faecium. A total of 3 (8.6%) strains of E. faecalis and 2 (33.3%) E. faecium strains showed high level aminoglycoside resistance (HLAR). None of the enterococci tested were vancomycin resistant. Drug resistance was more common among E. faecium strains. All clinically significant isolates of enterococci should be tested for their antibiotic sensitivity pattern including HLAR, and for treatment, antibiotics are selected based on in vitro antibiotic sensitivity test results.

Aminoglycosides↗
PubMed1999

Prevalence of resistance to MLS antibiotics in 20 European university hospitals participating in the European SENTRY surveillance programme. Sentry Participants Group.

Macrolide, lincosamide and streptogramin (MLS) antibiotics are chemically distinct inhibitors of bacterial protein synthesis. Resistance to MLS antibiotics may be constitutive or inducible. The purpose of this study is to update our understanding of the prevalence of different forms of MLS resistance in Europe. The analysis of 3653 clinical pneumococcal, staphylococcal and enterococcal isolates exhibited an average percentage of 21.3% and 6.2% intermediate and high-level penicillin-resistant Streptococcus pneumoniae, 21.8% methicillin-resistant Staphylococcus aureus and 11% vancomycin-resistant Enterococcus faecium. Geographical differences in erythromycin and clindamycin resistance in isolates of S. pneumoniae and S. aureus strongly reflect geographical variations in susceptibility to penicillin and methicillin, respectively. A very narrow range of MICs was obtained with quinupristin/dalfopristin, with no S. pneumoniae, S. aureus and E. faecium isolate having an MIC of > 4 mg/L, indicating a possible role of quinupristin/dalfopristin in the treatment of infections by multi-resistant Gram-positive bacteria.

Anti-Bacterial Agents↗
PubMed1988

Norfloxacin binds to human fecal material.

Earlier studies have reported very high (120 to 2,700 mg/kg) concentrations of norfloxacin in feces after therapeutic doses. MICs for fecal microorganisms are with few exceptions far below these levels. Nevertheless, clinical investigations show that the main part of the aerobic gram-positive and the anaerobic microflora remains unaffected after norfloxacin administration. In this study, the binding of [14C]norfloxacin to fecal material was analyzed. The binding of a group of nonlabeled quinolones to feces and the interactions between Enterococcus faecium, Bacteroides fragilis, and norfloxacin were also investigated. The results showed that norfloxacin has the ability to bind to feces. The specific binding was reversible, saturated after 90 min of incubation at 37 degrees C, and increased linearly with fecal concentration. Scatchard plots and nonlinear regression computer analyses revealed two different binding classes. The primary specific binding had a dissociation constant (KD) of 1.0 microM and a maximal binding capacity (Bmax) of 0.12 mumol/g of feces. The KD and Bmax of the secondary, more unspecific binding were 450 microM and 11.8 mumol/g of feces, respectively. The binding of unlabeled ciprofloxacin, enoxacin, ofloxacin, pefloxacin, and norfloxacin to feces was comparable to that of [14C]norfloxacin. The results of norfloxacin binding to suspensions of B. fragilis suggested that the main part of the binding is to the bacterial fraction of feces. In the presence of 8.0 g (dry weight) of B. fragilis per liter, the MBC of norfloxacin for E. faecium increased from 8 to 256 micrograms/ml. The finding of the present study indicated that binding of norfloxacin to feces may explain the paradox of high fecal concentrations of norfloxacin versus the actual effect on the normal gastrointestinal microflora.

Adult↗
PubMed2005

Antimicrobial activities of seven novel tetramethylpiperidine-substituted phenazines against multiple-drug-resistant Gram-positive bacteria.

BACKGROUND: A dramatic increase in multiple-drug-resistant (MDR) Gram-positive pathogens has occurred in recent times, leading to increased rates or morbidity and mortality and also associated with high costs for the treatment of these infections. It is clear that there is an urgent need for the development of effective antimicrobial agents. The anti-bacterial activity of seven 2,2,6,6-tetramethylpiperidine (TMP)-substituted phenazines, compared to clofazimine (B663), were tested against 70 clinical isolates of methicillin-resistant Staphylococcus aureus, MDR Streptococcus pneumoniae and resistant Enterococcus sp. METHODS: Standard minimum inhibitory concentration agar dilution susceptibility tests were done on all isolates, including ATCC control strains. RESULTS: All the TMP-substituted phenazines were more active than clofazimine against all isolates tested. Compound B4125 was the most active by inhibiting all growth of the organisms tested, including vancomycin-resistant Enterococcus faecium. CONCLUSION: Clofazimine has been shown to have anti-staphylococcal activity. We demonstrate enhanced anti-bacterial activity of TMP-substituted phenazines against drug-resistant Gram-positive organisms compared to clofazimine.

Clofazimine↗
PubMed1999

Antimicrobial susceptibilities of clinical isolates of vancomycin-resistant enterococci in Taiwan.

To understand the antimicrobial resistance patterns of vancomycin-resistant enterococci in Taiwan, we tested the in vitro activities of 10 antimicrobial agents against 71 clinical isolates (39 of Enterococcus faecalis and 32 of Enterococcus faecium) by means of the agar dilution method. Resistance was determined on the basis of the minimum inhibitory concentration (MIC) of each antimicrobial agent--MIC50 and MIC90 (minimum concentrations required to inhibit growth of 50% and 90% of isolates, respectively) were determined. No beta-lactamase producers were identified with the cefinase test. All E. faecalis isolates were susceptible to penicillin and ampicillin, and 97% of these isolates were resistant to teicoplanin (vanA phenotype). Of the E. faecium isolates, 75% were susceptible to teicoplanin (vanB phenotype) and most were resistant to penicillin (94%) and ampicillin (94%). Quinupristin/dalfopristin was markedly less active against E. faecalis than E. faecium isolates (MIC50, 64 vs 2 micrograms/mL; MIC90, 128 vs 8 micrograms/mL; susceptibility rates, 3% vs 81%). Five of the eight vanA phenotype E. faecium isolates and one of the 24 vanB phenotype E. faecium isolates were resistant to quinupristin/dalfopristin. The activity of rifampin was also species-specific, with E. faecium being markedly less susceptible to this agent than E. faecalis (MIC50, 16 vs 1 microgram/mL; MIC90, 64 vs 4 micrograms/mL). Our data suggest the potential of teicoplanin and quinupristin/dalfopristin as appropriate antimicrobial agents in the treatment of infections caused by vanB phenotype E. faecium. Penicillin, ampicillin, and rifampin alone, or preferably in combination with other agents, appear to be the most appropriate agents for the treatment of vancomycin-resistant E. faecalis infections in Taiwan.

Drug Resistance, Microbial↗
PubMed2002

The prevalence of faecal carriage of ampicillin-resistant and high-level gentamicin-resistant enterococci among inpatients at 10 major Norwegian hospitals.

From March to October 1999, 854 patients hospitalized at 10 major Norwegian hospitals were screened for rectal carriage of ampicillin-resistant enterococci (ARE) and high-level gentamicin-resistant enterococci (HLGRE). A total of 59 ARE carriers (prevalence 6.9%, range 0-22% among hospitals) and 28 HLGRE carriers (prevalence 3.3%, range 1-11%) were detected. All ARE or HLGRE strains were susceptible to vancomycin, whereas 77% of the ARE isolates were resistant to ciprofloxacin. All the ARE strains were identified as Enterococcus faecium, and 48% of these were genomically closely related as shown by PFGE. Specific point mutations in the pbp5 gene were associated with reduced susceptibility to ampicillin. The adjusted risk of becoming a carrier of ARE was related to the use of glycopeptides [odds ratio (OR) = 4.8], the use of any antimicrobial agent (OR = 3.1) and more than one hospital admission during the last six months (OR = 2.0). Twenty-five of 28 HLGRE isolates were Enterococcus faecalis. The aacA/aphD genes were detected in 26 (93%) and the aphA3 in 19 (68%) of the HLGRE isolates. Sixty-four percent of the HLGRE isolates belonged to two PFGE clusters. Consumption of antimicrobial agents was also a significant risk factor for HLGRE colonization (OR = 5.4), while prescription of penicillins was associated with reduced risk (OR = 0.28).

Ampicillin Resistance↗
PubMed2004

Linezolid and quinupristin/dalfopristin resistance in vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus prior to clinical use in Turkey.

The aim of this study was to determine the in vitro antimicrobial activity of recently licensed quinupristin/dalfopristin and linezolid which have not yet been in clinical use in Turkey against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) strains isolated from various clinical specimens by using the Etest. The results showed that all MRSA strains were fully susceptible to both the new compounds. All strains were inhibited by 1 mg/l quinupristin/dalfopristin (mode MIC 0.38 mg/l) and by 3 mg/l linezolid (mode MIC 1.5 mg/l). Four strains of Enterococcus faecium showed an increase of resistance of 2-3 mg/l to quinupristin/dalfopristin (susceptible mode MIC 0.38 mg/l). With linezolid, all strains except two fell within the range 0.75-2.0 mg/l.

Acetamides↗
PubMedDate not supplied

Increasing prevalence of high-level gentamicin resistance among Enterococci isolated in Greece.

High-level gentamicin-resistant enterococci (HLGRE) (MIC >512 microg/ml) were frequently recovered in the AHEPA University Hospital, Thessaloniki, Greece, during a 15-month period (67/158, 42.4%). PCR testing showed that high-level gentamicin resistance was attributable to the presence of the aac(6')-aph(2") gene, while the recently described genes aph (2")-Ic and aph(2")-Id were not detected. High-level gentamicin resistance could be transferred with varying frequency from 41 of 57 Enterococcus faecalis and 5 of 10 Enterococcus faecium isolates. All transconjugants acquired high-level resistance to streptomycin. HLGRE cause therapeutic problems in our region, since none of the clinically available aminoglycosides can be used in severe infections.

Anti-Bacterial Agents↗
PubMed2001

Antimicrobial resistance surveillance of bacteria in 1999 in Korea with a special reference to resistance of enterococci to vancomycin and gram-negative bacilli to third generation cephalosporin, imipenem, and fluoroquinolone.

The trend of antimicrobial resistance of bacteria isolated from patients in 30 Korean hospitals in 1999 was analyzed with a particular attention to cefotaxime- or fluoroquinolone-resistant gram-negative bacilli, imipenem-resistant Pseudomonas aeruginosa, and vancomycin-resistant enterococci. Adequacy of susceptibility testing, and any change in the frequencies of isolated species were also analyzed. The results showed that only 20% and 30% of hospitals tested the piperacillin-tazobactam and cefoxitin susceptibility of Enterobacteriaceae, respectively, only 24% of hospitals the piperacillin-tazobactam susceptibility of P. aeruginosa, and 17% of hospitals the fusidic acid susceptibility of staphylococci. Among the isolates 26.3% were glucose-nonfermenting gram-negative bacilli, and 34.7% of Enterococcus were Enterococcus faecium. Slight decline of cefotaxime-resistance rate to 20% was noted in Klebsiella pneumoniae, while fluoroquinolone-resistance rate was 68% in Acinetobacter baumannii. The ceftazidime- and imipenem-resistance rates were 17% and 18%, respectively in P. aeruginosa. The vancomycin-resistance rate of E. faecium rose significantly to 15.1%, but the rates varied significantly depending on hospitals suggesting presence of different degree of selective pressure or nosocomial spread. In conclusion, the prevalence of imipenem-resistant P. aeruginosa and the increase of vancomycin-resistant E. faecium were the particularly worrisome phenomena observed in this study.

Anti-Bacterial Agents↗
PubMed1994

Characterisation of lactic acid bacteria isolated from naturally fermented Greek dry salami.

A total of 348 lactic acid bacteria isolated from five batches of naturally fermented dry salami at various stages of ripening were characterised. The majority of the strains were assigned to two main phylogenetic groups of species: (i) the psychrotrophic, formerly called atypical, meat streptobacteria (169 strains) and (ii) a new genus Weissella (120), which was recently proposed (Collins et al., 1993) to include Leuconostoc paramesenteroides and some other closely related species. Meat streptobacteria were identified as Lactobacillus curvatus (88 strains) and L. sake (76), whereas 5 strains were indistinguishable and, thus designated L. sake/curvatus. Non-psychrotrophic streptobacteria were also isolated and identified as L. plantarum (34 strains), L. farciminis (10), L. coryniformis (1) and L. casei subsp. pseudoplantarum (1). The majority of the Weissella strains (86) were leuconostoc-like bacteria; four of them were identified as W. viridescens, 11 belonged to the newly described W. hellenica (Collins et al., 1993), another 11 resembled W. paramesenteroides, whereas 60 isolates were not classified to any species. The latter group comprised strains that produced D(L)-lactate. The remaining Weissella were gas-forming, arginine-positive rods assigned to W. minor (31) and W. halotolerans (3). Other species identified were Enterococcus faecium (10), Leuconostoc mesenteroides (1), L. brevis (1) and Pediococcus sp. (1). The main criteria used to distinguish between above species as well as their distribution on the five salami batches in relation to their succession with time and suitability as starters were discussed.

Animals↗
PubMed2003

In vitro activity of piperacillin/tazobactam and other broad-spectrum antibiotics against bacteria from hospitalised patients in the British Isles.

Piperacillin/tazobactam is used for empirical therapy of severe and complex infections. We assessed its activity, 9 years after launch, against consecutive, clinically significant isolates from in-patients in UK and Ireland. Standardised disc susceptibility tests were performed on 5031 isolates at 28 hospitals. For quality assurance purposes, 5% of these isolates were collected centrally for MIC tests, as were those with exceptional resistances. Compared with a similar pre-launch survey in 1991, there were major increases in the proportions of Staphylococcus aureus, Pseudomonas aeruginosa, beta-haemolytic streptococci and Enterococcus faecium isolates collected, balanced by decreases in Escherichia coli, Proteus mirabilis and coagulase-negative staphylococci. These changes in species prevalence mostly favoured organisms with inherent resistance(s) or-in the case of S. aureus-reflected the massive increase of MRSA, up from 0.7% of all isolates in 1991 to 14.8% in 2001. Based on the disc tests, piperacillin/tazobactam retained activity against 87% of Enterobacteriaceae isolates, 95% of P. aeruginosa, 99% of streptococci and 96% of Enterococcus faecalis. Resistance nevertheless had increased since 1991 in E. coli from 4 to 10%, Klebsiella spp. (5 to 21%) and in AmpC-inducible Enterobacteriaceae (17 to 23%), though not in P. mirabilis or P. aeruginosa. MIC tests confirmed most of the piperacillin/tazobactam resistance found by disc tests in Enterobacter spp., but indicated susceptibility for about half of the E. coli isolates recorded as resistant in disc tests. This situation might be remedied by reducing the zone breakpoint, but this would increase the "false susceptible" rate unacceptably. Thus, if disc tests suggest that an isolate is marginally resistant to piperacillin/tazobactam and the drug is sought as therapy, it is recommended that MIC be determined with, e.g., an Etest.

Bacteria↗
PubMed2005

Endocarditis due to vancomycin-resistant enterococci: case report and review of the literature.

BACKGROUND: Endocarditis due to vancomycin-resistant enterococci (VRE) is rare, and the literature consists almost exclusively of reports of single cases. METHODS: We report a case of VRE prosthetic valve endocarditis and review 18 cases of native and prosthetic valve VRE endocarditis reported in the literature. RESULTS: The majority of cases were due to Enterococcus faecium. Nearly all of these infections were hospital acquired, and the vast majority of patients had significant underlying disease processes, including dialysis and transplantation. More than three-quarters of cases were left-sided, and the aortic valve was most commonly involved. Peripheral stigmata of endocarditis were not reported in any of the cases. Approximately 40% of patients developed cardiac complications. Nearly three-quarters of patients survived, despite the difficulties associated with providing bactericidal antimicrobial therapy, and only 4 patients underwent valve replacement. CONCLUSIONS: VRE endocarditis is an uncommon nosocomial infection that affects patients with significant comorbid conditions. Most cases are due to E. faecium, and the aortic valve is involved in at least one-half of cases. One-third of patients require surgical treatment. Optimal antimicrobial therapy remains undefined, but an attempt to identify bactericidal combination therapy should be sought.

Adult↗