Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “enterococci”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,441 records · Page 80Linked to original sources
PubMed1998

Pharmacodynamic properties of HMR 3004, a novel ketolide, on respiratory pathogens, enterococci and Bacteroides fragilis demonstrated by studies of time kill kinetics and postantibiotic effect.

OBJECTIVE: The pharmacodynamic properties of the novel ketolide (a new class of macrolide) antibiotic, HMR 3004, were investigated by studying time-kill kinetics and postantibiotic effect. METHODS: The time-kill kinetics were studied at two inocula against three strains each of Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, Streptococcus pyogenes, Enterococcus faecalis, Enterococcus faecium and Bacteroides fragilis. The postantibiotic effects of HMR 3004 were also investigated on these organisms at concentrations equivalent to 1, 4 and 10 x MIC. RESULTS: The time kill-kinetic data demonstrated that HMR 3004 is inoculum dependent and predominantly bacteriostatic being only slowly bactericidal at higher concentrations. HMR 3004 exhibited a significant postantibiotic effect with all strains studied, ranging from 1.9--6.2 h at 10 x MIC. CONCLUSIONS: The bacteriostatic activity and significant postantibiotic effect demonstrated by HMR 3004 are similar to those previously obtained with other macrolides.

Journal Article↗
PubMed2002

Physical and genetic map of Enterococcus faecium ATCC19434 and demonstration of intra- and interspecific genomic diversity in enterococci.

A physical map of the Enterococcus faecium ATCC19434 chromosome was constructed by NotI, I-CeuI and Sse8387I. The chromosome was a circular DNA of 2600 kb in size, and contained six rRNA operons (rrn). The locations and orientations of the six rrn operons and 24 different determinants were mapped. Genomes of three additional E. faecium strains were also analyzed by I-CeuI digestion, and the genome sizes were found to vary from 2550 to 2995 kb. We further investigated the genome sizes and number of rrn operons in four E. faecalis, one E. avium, and one E. durans strains. The genome sizes were larger than E. faecium: 3000-3250 kb in E. faecalis, 3445 kb in E. avium, and 3070 kb in E. durans. E. avium and E. durans contained six rrn operons as in E. faecium, but all the E. faecalis strains possessed four rrn operons.

Chromosomes, Bacterial↗
PubMed1988

Synergistic effect of ampicillin or vancomycin in combination with decreasing concentrations of streptomycin against enterococci.

The extent of synergistic killing and duration of the post-antibiotic effect (PAE) was evaluated in streptomycin-susceptible strains of Streptococcus faecalis and Streptococcus faecium with 20 mcg/ml of ampicillin or 10 mcg/ml of vancomycin in combination with decreasing concentrations of streptomycin (20, 10, 5, 2, 1, 0.5 mcg/ml). The bactericidal activity or duration in recovery period declined progressively in a linear pattern with decreasing concentrations of streptomycin. One log10 or greater reduction in viable counts was seen with streptomycin concentrations of 2 mcg/ml or higher with both ampicillin and vancomycin. A synergistic increase in recovery period (PAE greater than or equal to 0.5 h) of ampicillin or vancomycin was observed with concentrations of streptomycin in excess of 2 mcg/ml and 1 mcg/ml, respectively. These results suggest that lower dosage of streptomycin in the therapy of enterococcal infections will probably result in a higher relapse rate.

Ampicillin↗
PubMed1989

Evaluation of the combination effects of ampicillin or vancomycin combined with streptomycin, gentamicin, tobramycin or netilmicin against enterococci.

Seven strains of Streptococcus faecalis, of which two possessed high-level resistance to streptomycin (MIC greater than or equal to 2000 mcg/ml), and two strains of Streptococcus faecium were evaluated with respect to killing-effect and duration of post-antibiotic effect (PAE) of ampicillin and vancomycin in combination with streptomycin, gentamicin, tobramycin and netilmicin. No synergistic combination effects were seen with the two strains highly-resistant to streptomycin or with the two Streptococcus faecium strains to netilmicin and tobramycin. When these strains were excluded, no significant difference in average killing could be detected between the four aminoglycosides. The mean prolongation in recovery period of susceptible strains was significantly longer with combinations of ampicillin and netilmicin or streptomycin as compared with either gentamicin or tobramycin. A similar relationship was seen for combinations of vancomycin with the four aminoglycosides.

Ampicillin↗
PubMed1985

In vitro activity of Sch 34343 against enterococci and other gram-positive bacteria.

The in vitro activity of Sch 34343, a new penem antibiotic, was compared with those of imipenem, vancomycin, and eight other antibiotics against gram-positive bacteria. Ninety percent of methicillin-susceptible Staphylococcus aureus and penicillin-susceptible streptococcal isolates were inhibited by Sch 34343 at concentrations of less than or equal to 0.125 micrograms/ml. Listeria monocytogenes isolates were susceptible to the penem at concentrations of less than or equal to 0.25 micrograms/ml. Penicillin-resistant pneumococci and viridans streptococci were relatively resistant to Sch 34343 (MIC for 90% of the isolates, 4 micrograms/ml), as were methicillin-resistant strains of S. aureus (MIC for 90% of the isolates, greater than or equal to 256 micrograms/ml). All 48 strains of Streptococcus faecalis were inhibited by concentrations of less than or equal to 8 micrograms of the drug per ml. Combinations of Sch 34343 with gentamicin demonstrated bactericidal synergism against 5 of 10 enterococcal strains tested in broth media and against 6 of 10 strains tested in 50% pooled human serum. The serum protein binding of Sch 34343 was ca. 65%. The antibacterial activity of Sch 34343 remained stable after 24 h of incubation at 37 degrees C in water or Dextrose-Phosphate broth. However, 63% of bioassayable activity was lost after 24 h of incubation at 37 degrees C in 50% human serum buffered with HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) (pH 7.4).

Anti-Bacterial Agents↗
PubMed1985

Antagonistic effect of penicillin-amikacin combinations against enterococci.

Amikacin has been shown to antagonize the bactericidal effect of penicillin against strains of Streptococcus faecalis which produce aminoglycoside 3'-phosphotransferase. The mechanism by which this phenomenon occurs was studied with an enzyme-producing strain (8436) and an enzyme-negative strain (8436c) derived by curing the former with novobiocin. Combinations of amikacin with beta-lactam antibiotics were antagonistic against strain 8436 but synergistic against strain 8436c. Against strain 8436 penicillin-amikacin combinations resulted in levels of killing comparable to those seen with high concentrations of penicillin (500 micrograms/ml), which were less bactericidal than lower concentrations of penicillin. No antagonism was observed between amikacin and non-beta-lactam cell wall-active drugs or between penicillin and kanamycin or neomycin, both of which are substrates for the enzyme. At concentrations near the MIC, amikacin was bactericidal against strain 8436c but bacteriostatic against strain 8436 (MIC, 250 micrograms/ml; MBC, 2,000 micrograms/ml). Neither penicillin nor phosphorylated amikacin affected the inhibition of ribosomal protein synthesis by amikacin in a cell-free system. Although antagonism of killing by amikacin in enzyme-positive strains was specific for combinations which included beta-lactam antibiotics, amikacin did not influence the binding of [3H]penicillin to penicillin-binding proteins in isolated bacterial cell membranes or in intact cells and did not detectably affect the autolytic system of cells exposed to penicillin. Antagonism of beta-lactam activity by a bacteriostatic effect of amikacin against the enzyme-producing strain is the most likely explanation for this phenomenon.

Amikacin↗
PubMed1985

Reversal of the in vitro susceptibility of enterococci to trimethoprim-sulfamethoxazole by folinic acid.

The in vitro susceptibilities of 21 clinical isolates of Streptococcus faecalis to trimethoprim (TMP) in combination with sulfamethoxazole (SMX) was evaluated in Mueller-Hinton broth (MHB) in the presence and absence of folinic acid as well as in urine. The mean MIC and MBC in MHB, expressed as the TMP concentration, was 0.13 and 0.32 micrograms of TMP-SMX per ml, respectively. In MHB supplemented with folinic acid, the mean MIC and MBC was 3.3 and 5.5 micrograms of TMP-SMX per ml, respectively. In urine the mean MIC of TMP-SMX for these isolates was 8.1 micrograms/ml (range, 1.6 to 50 micrograms/ml). All isolates were inhibited by less than 0.01 micrograms of TMP-SMX per ml when methotrexate was added to the urine.

Drug Combinations↗
PubMed1989

In vitro activities of quinolones against enterococci resistant to penicillin-aminoglycoside synergy.

The MICs and MBCs of CI-934, ciprofloxacin, difloxacin (A-56619), A-56620, norfloxacin, enoxacin, amifloxacin, and coumermycin were determined for 43 clinical isolates of Enterococcus faecalis known to be resistant to penicillin-aminoglycoside synergy. Results were compared with those obtained for 37 synergy-susceptible E. faecalis and 22 Enterococcus faecium strains. Although no substantial differences in quinolone activities were observed between synergy-resistant and -susceptible E. faecalis strains, CI-934 and ciprofloxacin were the drugs that demonstrated the greatest bactericidal activity against both types of E. faecalis. The MBCs of the other quinolones were generally within a single twofold dilution of the MICs, but their antienterococcal activity did not approach that of CI-934 or ciprofloxacin. The MBCs for 90% of the isolates of CI-934 for synergy-resistant and -susceptible E. faecalis strains were 1 and less than or equal to 0.5 microgram/ml, respectively. The ciprofloxacin MBC for 90% of the E. faecalis strains tested was 1 microgram/ml. For E. faecium isolates the CI-934 and ciprofloxacin MBCs for 90% of the isolates were 8 and 4 micrograms/ml, respectively. Time-kill assays performed with synergy-susceptible enterococcal strains showed that the bactericidal activities of both CI-934 and ciprofloxacin were less than those of the penicillin-aminoglycoside combinations tested. However, against synergy-resistant isolates the activities of these two quinolones were comparable with and sometimes greater than those of penicillin-aminoglycoside combinations.

4-Quinolones↗
PubMed1990

Chemoprophylactic efficacy against experimental endocarditis caused by beta-lactamase-producing, aminoglycoside-resistant enterococci is associated with prolonged serum inhibitory activity.

We studied the prevention of experimental aortic endocarditis caused by a beta-lactamase-producing, aminoglycoside-resistant strain of Enterococcus faecalis (HH22) in 146 catheterized rabbits. Both vancomycin and ampicillin-sulbactam readily killed this resistant enterococcus strain in vitro. At a challenge inoculum of approximately 10(9) CFU, vancomycin (40 mg/kg intravenously [i.v.]), ampicillin (40 mg/kg i.v.), or a combination of ampicillin plus a beta-lactamase inhibitor, sulbactam (20 mg/kg, i.v.), did not prevent the development of endocarditis in any of the animals, although mean intravegetation bacterial densities were significantly lower in animals that received vancomycin than they were in animals that received other therapies (P less than 0.001). At a challenge inoculum of 10(6) CFU, vancomycin was 100% effective in preventing enterococcal endocarditis compared with ampicillin (29%; P less than 0.00001) and ampicillin-sulbactam (65%; P less than 0.01). Factors associated with the superior prophylactic efficacy of vancomycin in this model included prolonged serum inhibitory activity and time above MICs. Factors not associated with the antienterococcal prophylactic efficacy of vancomycin included the duration of the in vitro postantibiotic effect of the drug and the magnitude of the ability of this drug to enhance enterococcal in vitro opsonophagocytic killing by polymorphonuclear leukocytes. The superior prophylactic efficacy of vancomycin in this endocarditis model related to the superior pharmacokinetic profile of the drug when it was given intermittently at dose intervals of every 6 h.

Aminoglycosides↗
PubMed1991

Effects of combinations of beta-lactams, daptomycin, gentamicin, and glycopeptides against glycopeptide-resistant enterococci.

Activities of combinations of beta-lactams, daptomycin, gentamicin, teicoplanin, and vancomycin against 11 clinical isolates of Enterococcus faecium highly resistant to glycopeptides, three plasmid-cured derivatives, eight E. faecalis and E. faecium transconjugants, and two susceptible recipient strains were tested. A marked synergy between penicillins or imipenem and glycopeptides against the glycopeptide-resistant strains but not against the glycopeptide-susceptible strains was observed by the double-disk agar diffusion assay. The synergy of combinations of amoxicillin, imipenem, penicillin G, or piperacillin with vancomycin or teicoplanin against resistant strains was confirmed by the checkerboard technique. The fractional inhibitory concentration indexes were generally below 0.25, except for one strain of E. faecium resistant to high levels of penicillin G. However, the combinations were not bactericidal as tested by time-killing experiments, and high concentrations (64 micrograms/ml) of amoxicillin, penicillin G, or piperacillin combined with 8 micrograms of vancomycin or teicoplanin per ml tended to be antagonistic. Addition of 4 micrograms of gentamicin per ml to these combinations enhanced their bactericidal effect, but they occasionally remained slightly less effective than beta-lactams associated with gentamicin. The combination of 10 micrograms of daptomycin per ml with gentamicin was bactericidal after 6 h against 11 glycopeptide-resistant strains.

Anti-Bacterial Agents↗