Infective endocarditis due to Staphylococcus aureus: 59 prospectively identified cases with follow-up.
Fifty-nine consecutive patients with definite Staphylococcus aureus infective endocarditis (IE) by the Duke criteria were prospectively identified at our hospital over a 3-year period. Twenty-seven (45.8%) of the 59 patients had hospital-acquired S. aureus bacteremia. The presumed source of infection was an intravascular device in 50.8% of patients. Transthoracic echocardiography (TTE) revealed evidence of IE in 20 patients (33.9%), whereas transesophageal echocardiography (TEE) revealed evidence of IE in 48 patients (81.4%). The outcome for patients was strongly associated with echocardiographic findings: 13 (68.4%) of 19 patients with vegetations visualized by TTE had an embolic event or died of their infection vs. five (16.7%) of 30 patients whose vegetations were visualized only by TEE (P < .01). Most patients with S. aureus IE developed their infection as a consequence of a nosocomial or intravascular device-related infection. TEE established the diagnosis of S. aureus IE in many instances when TTE was nondiagnostic. Visualization of vegetations by TTE may provide prognostic information for patients with S. aureus IE. (+info)
The in-vitro activity of HMR 3647, a new ketolide antimicrobial agent.
The in-vitro activity of HMR 3647, a novel ketolide, was investigated in comparison with those of erythromycin A, roxithromycin, clarithromycin (14-membered ring macrolides), amoxycillin-clavulanate and ciprofloxacin against 719 recent clinical Gram-positive, Gram-negative and anaerobic isolates and type cultures. HMR 3647 generally demonstrated greater activity than the other compounds with MIC90s of < or =0.5 mg/L, except for Staphylococcus epidermidis (MIC90 > 128 mg/L), Haemophilus influenzae (MIC90 = 2 mg/L), Enterococcus faecalis (MIC90 = 2 mg/L), Enterococcus faecium (MIC90 = 1 mg/L) and the anaerobes, Bacteroides fragilis (MIC90 = 2 mg/L) and Clostridium difficile (MIC90 = 1 mg/L). In general, an increase in the size of the inoculum from 10(4) to 10(6) cfu on selected strains had little effect on the MICs of HMR 3647. Additionally, the in-vitro activity of HMR 3647 was not affected by the presence of either 20 or 70% (v/v) human serum. The antichlamydial activity of HMR 3647 was generally greater than that of commonly used antichlamydial antimicrobials. (+info)
Cell-wall determinants of the bactericidal action of group IIA phospholipase A2 against Gram-positive bacteria.
We have shown previously that a group IIA phospholipase A2 (PLA2) is responsible for the potent bactericidal activity of inflammatory fluids against many Gram-positive bacteria. To exert its antibacterial activity, this PLA2 must first bind and traverse the bacterial cell wall to produce the extensive degradation of membrane phospholipids (PL) required for bacterial killing. In this study, we have examined the properties of the cell-wall that may determine the potency of group IIA PLA2 action. Inhibition of bacterial growth by nutrient deprivation or a bacteriostatic antibiotic reversibly increased bacterial resistance to PLA2-triggered PL degradation and killing. Conversely, pretreatment of Staphylococcus aureus or Enterococcus faecium with subinhibitory doses of beta-lactam antibiotics increased the rate and extent of PL degradation and/or bacterial killing after addition of PLA2. Isogenic wild-type (lyt+) and autolysis-deficient (lyt-) strains of S. aureus were equally sensitive to the phospholipolytic action of PLA2, but killing and lysis was much greater in the lyt+ strain. Thus, changes in cell-wall cross-linking and/or autolytic activity can modulate PLA2 action either by affecting enzyme access to membrane PL or by the coupling of massive PL degradation to autolysin-dependent killing and bacterial lysis or both. Taken together, these findings suggest that the bacterial envelope sites engaged in cell growth may represent preferential sites for the action and cytotoxic consequences of group IIA PLA2 attack against Gram-positive bacteria. (+info)
Interactions of a nonpeptidic drug, valacyclovir, with the human intestinal peptide transporter (hPEPT1) expressed in a mammalian cell line.
The results of previous work performed in our laboratory using an in situ perfusion technique in rats and rabbit apical brush border membrane vesicles have suggested that the intestinal uptake of valacyclovir (VACV) appears to be mediated by multiple membrane transporters. Using these techniques, it is difficult to characterize the transport kinetics of VACV with each individual transporter in the presence of multiple known or unknown transporters. The purpose of this study was to characterize the interaction of VACV and the human intestinal peptide transporter using Chinese hamster ovary (CHO) cells that overexpress the human intestinal peptide transporter (hPEPT1) gene. VACV uptake was significantly greater in CHO cells transfected with hPEPT1 than in cells transfected with only the vector, pcDNA3. The optimum pH for VACV uptake was determined to occur at pH 7.5. Proton cotransport was not observed in hPEPT1/CHO cells, consistent with previously observed results in tissues and Caco-2 cells. VACV uptake was concentration dependent and saturable with a Michaelis-Menten constant and maximum velocity of 1.64 +/- 0.06 mM and 23.34 +/- 0.36 nmol/mg protein/5 min, respectively. A very similar Km value was obtained in hPEPT1/CHO cells and in rat and rabbit tissues and Caco-2 cells, suggesting that hPEPT1 dominates the intestinal transport properties of VACV in vitro. VACV uptake was markedly inhibited by various dipeptides and beta-lactam antibiotics, and Ki values of 12.8 +/- 2.7 and 9.1 +/- 1.2 mM were obtained for Gly-Sar and cefadroxil at pH 7.5, respectively. The present results demonstrate that VACV is a substrate for the human intestinal peptide transporter in hPEPT1/CHO cells and that although transport is pH dependent, proton cotransport is not apparent. Also, the results demonstrate that the hPEPT1/CHO cell system has use in investigating the transport kinetics of drugs with the human intestinal peptide transporter hPEPT1; however, the extrapolation of these transport properties to the in vivo situation requires further investigation. (+info)
Identification of positively charged residues of FomA porin of Fusobacterium nucleatum which are important for pore function.
FomA porin is the major outer-membrane protein of Fusobacterium nucleatum. It exhibits the functional properties of a general diffusion porin, but has no sequence similarity to other porins. According to the proposed topology model, each monomer of this trimeric protein is a beta-barrel consisting of 16 transmembrane segments with eight surface-exposed loops. Several conserved charged residues are proposed to extend from the beta-barrel wall into the aqueous channel lumen, and may contribute to a transverse electric field similar to that at the pore constriction of porins with known structure. The goal of our study was to identify particular basic residues contributing to such an electric field in FomA. Several arginines and lysines were replaced by negatively charged glutamates or uncharged alanines. The mutated FomA porins were expressed in Escherichia coli, and the effects on pore function were studied in vivo, by assaying the uptake rate of beta-lactam antibiotics, and in vitro after reconstitution of the purified proteins in lipid bilayer membranes. Some of the point mutations had a significant impact on the channel properties. The substitution R92A produced a 130% increased permeability of the zwitterionic beta-lactam cephaloridine, and the cation selectivity of R92E increased by 70%. The effects of the R90E substitution on channel properties were similar. Most of the point mutations had a minor effect on the voltage gating of the FomA channel, resulting in an increased sensitivity, except for K78E, which showed a decreased sensitivity. The latter mutation had no effect on cation selectivity, but the K78A substitution improved the uptake rate of cephaloridine. The results presented here indicate that arginines 90 and 92 are probably part of the constriction zone of the FomA porin, and lysine 78 and arginines 115 and 117 are probably in close proximity to this region as well. (+info)
Microbiological degradation of bile acids. Nitrogenous hexahydroindane derivatives formed from cholic acid by Streptomyces rubescens.
The metabolism of cholic acid (I) by Streptomyces rubescens was investigated. This organism effected ring A cleavage, side-chain shortening and amide bond formation and gave the following metabolites: (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1 beta-yl]valeric acid (IIa) and its mono-amide (valeramide) (IIb); and 2,3,4,6, 6abeta,7,8,9,9aalpha,9bbeta-decahydro-6abeta-methyl-1H-cyclopenta[f]quinoline-3,7 -dione(IIIe)and its homologues with the beta-oriented side chains, valeric acid, valeramide, butanone and propionic acid, in the place of the oxo group at C-7, i.e.compounds (IIIa), (IIIb), (IIIc) and (IIId) respectively. All the nitrogenous metabolites were new compounds, and their structures were established by partial synthesis except for the metabolite (IIIc). The mechanism of formation of these metabolites is considered. A degradative pathway of cholic acid (I) into the metabolites is also tentatively proposed. (+info)
Intravenous and oral mono- or combination-therapy in the treatment of severe infections: ciprofloxacin versus standard antibiotic therapy. Ciprofloxacin Study Group.
Five hundred and forty patients with severe infection were enrolled in a multicentre, prospective, randomized, non-blinded study to compare the efficacy and safety of i.v. ciprofloxacin with i.v. standard therapy. Five hundred and thirty-one patients received at least one dose of study drug for pneumonia (310), septicaemia (112) or skin and skin structure infection (109). Intravenous ciprofloxacin (400 mg, every 8 h) or i.v. ciprofloxacin (400 mg, every 8 h) plus a beta-lactam were compared with a standard monotherapy (beta-lactam) or combination (aminoglycoside plus a beta-lactam) therapy. Patients were treated parenterally for a minimum of 2 or 3 days, then at the discretion of the investigator could be switched to oral therapy (ciprofloxacin 750 mg, every 12 h or a standard oral therapy). Patients were randomized in the ratio of 2:1 for the ciprofloxacin and standard therapy treatment groups and stratified to monotherapy if the APACHE II score was < or = 20 or to combination therapy if the APACHE II score was 21-29. Three hundred and ninety-five (74%) patients were valid for the efficacy analysis: these comprised 242 pneumonia (167 ciprofloxacin and 75 standard therapy), 70 septicaemia (47 ciprofloxacin and 23 standard therapy), and 83 skin infections (56 ciprofloxacin and 27 standard). The primary efficacy variable was clinical response and the secondary efficacy assessment was bacteriological response at the end of therapy (2 or 3 days after treatment). The mean duration of therapy for patients receiving only i.v. monotherapy or combination therapy was shorter (9-10 days) than for patients receiving sequential i.v./p.o. therapy (14-17 days). At the end of therapy, overall clinical resolution/improvement (success) for monotherapy was 138/166 (83%) for the ciprofloxacin group, compared with 74/87 (85%) for standard-treated patients (95% CI = -11.5% to 7.6%), and for combination therapy the response was 43/51 (84%) for the ciprofloxacin group and 14/20 (70%) for standard-treated patients (95% CI = -6.3% to 34.9%). For pneumonia, the most frequent infection treated, clinical success rates following monotherapy were 85% for ciprofloxacin and 83% for standard-treated patients and 83% for ciprofloxacin compared with 69% for standard-treated patients in the combination therapy group. Bacteriological eradication/presumed eradication following monotherapy was 85/102 (83%) for ciprofloxacin and 31/46 (67%) for standard-treated patients (95% CI = 1.6% to 30.3%), and that for combination therapy was 29/36 (81%) for ciprofloxacin and 7/10 (70%) for standard-treated patients (95% CI = -18.3% to 39.5%). Drug-related adverse events, primarily diarrhoea and nausea, were reported in 22% of ciprofloxacin-treated patients and 20% of standard-treated patients. In summary, ciprofloxacin administered alone or in combination was found to be effective in treating a wide range of severe infections. (+info)
A macrolactam inhibitor of T helper type 1 and T helper type 2 cytokine biosynthesis for topical treatment of inflammatory skin diseases.
T lymphocytes play a critical part in inflammatory skin diseases but are targeted by available therapies that have only partial efficacy, significant side-effects, or both. Because psoriasis, atopic dermatitis, and allergic contact hypersensitivity are associated with T helper type 1 (Th1), T helper type 2 (Th2), or mixed Th1-Th2 cell subsets and cytokine types, respectively, there is a need for a better broad-based inhibitor. The macrolactam ascomycin analog, ABT-281, was found to inhibit potently T cell function across species and to inhibit expression of multiple cytokines in human peripheral blood leukocytes which have been found in human skin disease cells and tissues. These included immunoregulatory Th1 (interleukin-2 and interferon-gamma) and Th2 (interleukin-4 and interleukin-5) cytokines. ABT-281 was shown to have potent topical activity (ED50 = 0.6% in acetone/olive oil) in a stringent swine model of allergic contact hypersensitivity, but its potency was markedly reduced compared with ascomycin when administered systemically due to more rapid clearance. Topical application of 3% ABT-281 in acetone/olive oil over 25% of the body surface in swine resulted in undetectable blood levels. Compared with a wide potency range of topical corticosteroids in clinical formulations, 0.3% and 1% ABT-281 ointments profoundly inhibited dinitrochlorobenzene-induced contact hypersensitivity in the pig by 78% and 90%, respectively, whereas super-potent steroids such as clobetasol propionate only inhibited in the 50% range and mild to moderate potency steroids such as fluocinolone acetonide were inactive. The potent topical activity of ABT-281 in swine, its superior efficacy, its rapid systemic clearance following uptake into the bloodstream, and its ability to inhibit cytokine biosynthesis of both Th1 and Th2 cell subsets, suggests that it will have a broad therapeutic value in inflammatory skin diseases, including psoriasis, atopic dermatitis, and allergic contact dermatitis. (+info)