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At least 451 records · Page 25Linked to original sources
PubMed1993

The wall associated lipoteichoic acid of Streptococcus sanguis.

A competitive ELISA is described for the measurement of lipoteichoic acid. The assay was used to determine the wall associated lipoteichoic acid of Streptococcus sanguis which was found to represent only 2-4% of the phenol extractable content. Extracellular lipoteichoic acid was detected even after exhaustive cell washing. This material was not the result of de novo synthesis because membrane de-polarization had no effect on the amount detected. Since extracellular lipoteichoic acid interfered with the measurement of cell surface antigen, cells were fixed with glutaraldehyde prior to assay. Lipoteichoic acid was demonstrated on the surface of fixed cells which did not leak antigen. The relevance of fixation used in antigen location studies by electron microscopy of immune-labelled cells is discussed.

Anti-Bacterial Agents↗
PubMedDate not supplied

Influence of Ly146032 on chemotaxis, chemiluminescence of PMN and lymphocyte transformation in vitro.

The influence of Ly146032, a new acidic lipopeptide, on chemotaxis, luminol-dependent chemiluminescence of human polymorphonuclear leukocytes (PMN) and phythemagglutinin induced lymphocyte transformation of murine cells was investigated. At therapeutic range there was no remarkable effect on the parameters tested. Incubation with more than 20 mg/l Ly146032 was followed by depression of chemiluminescence, whilst transformation of maximally PHA stimulated lymphocytes was suppressed by more than 32 mg/l Ly146032.

Anti-Bacterial Agents↗
PubMed1996

In vitro study of the potential role of quinupristin/dalfopristin in the treatment of catheter-related staphylococcal infections.

The susceptibility of clinical isolates of methicillin-susceptible and -resistant staphylococci from cancer patients with central venous catheter bacteremia to quinupristin/dalfopristin, a semisynthetic streptogramin, was determined in vitro. Susceptibility of these isolates to nine other antistaphylococcal antibiotics was also determined for comparison. A total of 197 staphylococcal strains were tested from 1983 to 1992. Quinupristin/dalfopristin was bactericidal against all isolates, independent of their resistance to methicillin. Its activity was similar to that of vancomycin but superior to that of teicoplanin. Quinupristin/dalfopristin may prove to be an important addition to our armamentarium against catheter-related staphylococcal infections.

Anti-Bacterial Agents↗
PubMed1989

Treatment of chronic experimental Staphylococcus aureus osteomyelitis with LY146032 and vancomycin.

LY146032 and vancomycin were compared as therapeutic agents in the treatment of chronic Staphylococcus aureus osteomyelitis in the rat. Quantitative cultures disclosed that one of 16, none of 16 and two of 17 tibiae were sterile from the control LY146032, and vancomycin groups, respectively. From positive cultures, geometric mean staphylococcal CFU per gram of bone were as follows: control, 5.13 +/- 1.58; LY146032, 5.36 +/- 0.43 (p = 0.57); and vancomycin, 4.33 +/- 1.73 (p = 0.078). Mean gross pathology was decreased significantly in both treatment groups. LY146032 was no more effective than vancomycin in reducing bacterial counts.

Animals↗
PubMed1987

Comparative activity of LY146032 against anaerobic cocci.

Fifty strains of anaerobic gram-positive cocci were tested in vitro against benzylpenicillin, teicoplanin, vancomycin and LY146032. The organisms displayed a wide range of susceptibility to penicillin and the minimum inhibitory concentration for 11 of the strains was greater than or equal to 1 mg penicillin/L. The activity of teicoplanin exceeded that of vancomycin by a factor of two. The activity of LY 146032 varied in different culture media and was dramatically potentiated by the addition of a physiological concentration of calcium. Peptococci were, in general, more susceptible than peptostreptococci to penicillin and to LY146032 in the absence of added calcium.

Anti-Bacterial Agents↗
PubMed1987

Effect of abscess milieu on bactericidal activity of LY146032 against staphylococci.

The antistaphylococcal activity of LY146032 was tested in human pus in vitro and in a murine abscess model in vivo. The drug was not degraded by pus containing beta-lactamase and had equally good or better activity than nafcillin or vancomycin against Staphylococcus aureus or Staphylococcus epidermidis in vitro and in vivo. Its activity was slightly enhanced when used in combination with rifampin and tobramycin.

Abscess↗
PubMed1988

A comparative monomolecular film study of antibiotic A21978C homologues of various lipid chain length.

A21978C is a calcium-dependent lipopeptide antibiotic whose biological properties are modulated by changes in its lipid chain length. This article reports on the monolayer characteristics of this cyclic lipopeptide and of LY146032 a semi synthetic homologue. The equilibrium spreading pressure pi e increases linearly with the ionic concentration of the subphase and is higher with divalent cations. The nature of the divalent cation plays a crucial role in the spreading as indicated by the variation in the molecular free energy delta Gs.delta Gs decreases in the order K+ greater than Mg2+ greater than Ca2+, which indicates privileged interactions with Ca2+. Also, the larger the lipid chain, the easier the spreading of antibiotic molecules. The compression isotherm curves are shown. The mean area of the uncompressed molecules is around 220-240 A 2 which is compatible with the size of the peptide cycle lying at the interface. The isotherm curves of the natural compounds show a transition region where the molecules are more compressible. At a given area/molecule, the surface pressures increase with the acyl chain length. When the molecules are spread on various salt solutions, the surface pressures increase in the order K+ less than Mg2+ less than Ca2+. The isotherm curves are not reversible upon a compression-expansion cycle and a wide amplitude hysteresis is observed. If a second compression is done, the curve shape is that of a liquid-expanded state and the transition region is no longer observed. This implies a conformational change of the molecules during the first compression process.

Anti-Bacterial Agents↗
PubMed1988

In vitro activity of LY146032 against gram-positive bacteria.

The activity of LY146032 (LY) was evaluated against 269 clinical isolates: 150 Staphylococcus spp. (Staph), 45 enterococci, 51 Clostridium spp., and 23 peptostreptococci. LY was compared to penicillin, metronidazole, imipenem, clindamycin, oxacillin, ciprofloxacin, vancomycin, and ampicillin. LY and oxacillin were tested against Staph by microdilution in cation-supplemented Mueller-Hinton broth (CSMHB), and in unsupplemented Mueller-Hinton broth (MHB). For LY, the MIC 90s in CSMHB were 16-32 dilutions lower. Among the Staph, the MIC 90s for LY, vancomycin, and ciprofloxacin were 4 micrograms/ml, 4 micrograms/ml, and 2 micrograms/ml respectively. The MIC 90s for enterococci by agar dilution were as follows: LY 8 micrograms/ml; ampicillin 4 micrograms/ml; imipenem 4 micrograms/ml; vancomycin 4 micrograms/ml; and ciprofloxacin 2 micrograms/ml. Clindamycin and penicillin were the most effective drugs against peptostreptococci and Clostridia spp., but LY was the most active drug against Clostridium difficile. The bactericidal activity of LY was determined by 24-hr time-kill curves in MHB. These showed a bactericidal effect against enterococci, and a bacteriostatic effect against three of four strains of Staph. Synergy was demonstrated against enterococci and Staph when LY was tested with aztreonam, ceftriaxone, or tobramycin. LY is a promising new agent against gram-positive bacteria, including methicillin resistant strains of staphylococci and enterococci.

Anti-Bacterial Agents↗
PubMed2006

Antibiotics--past, present, and future.

The drug therapy for diseases other than those caused by microbial agents involves treating the host. In infectious diseases therapy, the goal is to rid the host of the pathogen. Hence, drug therapy is aimed at the pathogen. Because a second living agent is involved in the triangle, drug therapy is affected by the pathogen's nature, its tissue specificity, and, most importantly, the changes it undergoes to survive. The history of antimicrobial therapy has clearly demonstrated that the drugs that are used to treat infections are also responsible for making them more difficult to treat in future. The only way to keep antimicrobial agents useful is to use them appropriately and judiciously.

Aminoglycosides↗
PubMed1988

Fluorescence indicates a calcium-dependent interaction between the lipopeptide antibiotic LY146032 and phospholipid membranes.

LY146032 is one of the A21978C family of calcium-dependent antibiotics. This paper reports on its interactions with membranes as studied by its intrinsic fluorescence. The Trp residue was found to have a low fluorescence yield because of Förster-type energy transfer to the kynurenine residue (Kyn) (epsilon = 5000 at 364 nm). However, the Kyn fluorescence (lambda max = 465 nm in H2O) was a sensitive probe of the membrane interactions, and it was used in steady-state fluorescence measurements including fluorescence polarization anisotropy. Initial binding of the peptide to phospholipid vesicles occurs in calcium-free solutions. When calcium is added, the resulting 10-fold fluorescent enhancement and 15-nm blue shift show that it causes the antibiotic to penetrate further into the lipid bilayer. Calcium is bound with an association constant of 151 M-1, while a phospholipid titration in the presence of calcium gave an association constant of 5 x 10(3) M-1 for egg phosphatidylcholine. Magnesium and cadmium cause very slight fluorescence enhancements, but a more significant effect is caused by the trivalent lanthanide ions. Analysis of these data indicates that the calcium-selective site is on the peptide and that ion binding to the phospholipid headgroups has a secondary role. Comparison with the divalent cation dependent antibiotics bacitracin and amphomycin shows that LY146032 has a quite different activity and that a calcium-dependent membrane interaction could account for results obtained in vivo.

1,2-Dipalmitoylphosphatidylcholine↗