bluuebunny/crossref_metadata_2025 huggingface dataset:
Endotoxin concentration in neutropenic patients with suspected gram-negative sepsis: correlation with clinical outcome and determination of anti-endotoxin core antibodies during therapy with polyclonal immunoglobulin M-enriched immunoglobulins
Authors: Behre G , Schedel I , Nentwig B , Wörmann B , Essink M , Hiddemann W
Published: June 2012

We carried out a study in patients with severe neutropenia from hematologic malignancy and suspected gram-negative sepsis to evaluate the clinical significance of endotoxin concentrations in plasma before and during a therapeutic intervention with a human polyclonal immunoglobulin M (IgM)-enriched immunoglobulin preparation (Pentaglobin; Biotest, Dreieich, Germany). Twenty-one patients with acute leukemia or non-Hodgkin's lymphoma entered the study upon the development of clinical signs of gram-negative sepsis and received the IgM-enriched immunoglobulin preparation every 6 h for 3 days (total dose, 1.3 liter with 7.8 g of IgM, 7.8 g of IgA, and 49.4 g of IgG), in addition to standardized antibiotic treatment. Concentrations of endotoxin and IgM and IgG antibodies against lipid A and Re lipopolysaccharide (LPS) in plasma were determined by a modified chromogenic Limulus amebocyte lysate test and semiquantitative enzyme linked immunosorbent assay, respectively, before each immunoglobulin infusion and during the following 25 days. Seventeen patients were endotoxin positive; in five of these patients, gram-negative infection was confirmed by microbiologic findings. Prior to therapy, endotoxemia correlated significantly with the occurrence of fever, and a quantitative correlation between the endotoxin concentration and body temperature was found during the individual course of infection in 8 of the 17 patients. Overall mortality from endotoxin-positive sepsis was 41% (7 of 17) and 64% (7 of 11) in patients with symptoms of septic shock. Nonsurvivors had significantly higher maximum concentration of endotoxin in plasma compared with those of survivors at the first study day (median of 126 versus 34 pg/ml; P < 0.05) and during the whole septic episode (median of 126 versus 61 pg/ml; P < 0.05). In survivors, immunoglobulin therapy resulted in a significant decrease in endotoxin levels in plasma within the initial 18-h treatment period, from a pretreatment median value of 28 pg/ml to a value of 8 pg/ml (P< 0.05). In the seven patients who died from uncontrollable infection, no effect of therapy on endotoxin levels in plasma was observed. IgM and IgG antibodies against lipid A and Re LPS increased significantly under immunoglobulin treatment, with significant correlations between antibodies against lipid A and Re LPS. These data strongly suggest a prognostic significance of the endotoxin levels in plasma and a potential effect of treatment with a polyclonal IgM-enriched immunoglobulin preparation. Further studies are needed to substantiate these findings and to assess the impact on the clinical course by way of a prospective placebo-controlled clinical trial.
Sequence analysis of the beta-lactamase repressor from Staphylococcus aureus and hybridization studies with two beta-lactamase-producing isolates of Enterococcus faecalis
Authors: Smith M C , Murray B E
Published: June 2012

The putative beta-lactamase (Bla) repressor gene, blaI, from the staphylococcal plasmid pI524 was isolated, and the DNA sequence was determined. The sequence of blaI was found to be identical to the blaI sequence from pI9789 (blaI blaZ seg-1), a plasmid related to pI524. A blaI probe from pI524 was hybridized with plasmid and genomic DNA from Bla+ Enterococcus faecalis isolates HH22 and PA. The Bla structural gene of HH22 has been previously shown to be of staphylococcal origin, but DNA homologous to the staphylococcal Bla repressor was not found, indicating that the constitutive production of beta-lactamase in these E. faecalis isolates may be the result of a missing repressor protein.
Investigation of the early killing of Staphylococcus aureus by daptomycin by using an in vitro pharmacodynamic model
Authors: Vance-Bryan K , Larson T A , Rotschafer J C , Toscano J P
Published: June 2012

The purpose of this study was to develop a pharmacodynamic model to describe the dependency of the rate of Staphylococcus aureus killing upon the concentration of daptomycin. A range of free (unbound) daptomycin concentrations ranging from 0.12 to 27 times the MIC were simulated in the peripheral compartment of a two-compartment pharmacokinetic model. Log-linear regression of free daptomycin concentrations versus growth or kill rate constants showed a significant correlation (r = -0.90; P less than 0.001). A Lineweaver-Burk plot of the reciprocal transformation of these data yielded a poor fit (r = -0.38; P greater than 0.05). When a Lineweaver-Burk-type regression analysis was performed on the reciprocal of the change in the rate constant rather than the rate constant itself, the result demonstrated good correlation (r = 0.90; P less than 0.0001). The observations were also well described by a sigmoidal maximum plateau pharmacologic effect model, in which the pharmacologic effect of daptomycin is a reduction in the bacterial exponential growth rate constant from the baseline in the absence of antibiotic to a lower (positive) growth or (negative) death rate constant observed in the presence of antibiotic. These data confirm that daptomycin exhibits concentration-dependent killing over a wide range of free daptomycin concentrations relative to the MIC and suggest that this is a saturable process similar to the Michaelis-Menten pharmacokinetic elimination of certain drugs.
Sparfloxacin, ethambutol, and cortisol receptor inhibitor RU-40 555 treatment for disseminated Mycobacterium avium complex infection of normal C57BL/6 mice
Authors: Perronne C , Cohen Y , Truffot-Pernot C , Grosset J , Vildé J L , Pocidalo J J
Published: June 2012

Sparfloxacin (50 mg/kg of body weight given subcutaneously each day), alone or in combination with ethambutol (50 mg/kg given subcutaneously each day), was examined for its therapeutic efficacy against experimental infection induced with the Mycobacterium avium complex in normal C57BL/6 mice. In addition, the potential anti-infective role of RU-40 555 (100 mg/kg given intraperitoneally each day), a drug that inhibits the cortisol receptors, was examined in the same model. Treatments were started 24 h after intravenous bacterial challenge and were continued for 21 days. Compared with controls, sparfloxacin or ethambutol decreased the CFU counts in spleens and lungs (P < 0.001). The sparfloxacin plus ethambutol combination was more effective than sparfloxacin alone in spleens (P < 0.001) but not in lungs. The sparfloxacin plus ethambutol plus RU-40 555 combination was more effective than the sparfloxacin plus ethambutol combination in spleens and lungs (P < 0.001). Thus, in this model, RU-40 555 enhanced the antibacterial activities of the antibiotics tested. Results of the study showed that normal C57BL/6 mice infected with the M. avium complex can be used for the evaluation of antimicrobial agents.
Activity of clarithromycin against Mycobacterium avium complex infection in beige mice
Authors: Klemens S P , DeStefano M S , Cynamon M H
Published: June 2012

The activity of clarithromycin alone and in combination with other antimycobacterial agents was evaluated in the beige (C57BL/6J bgj/bgj) mouse model of disseminated Mycobacterium avium complex (MAC) infection. A dose-response experiment was performed with clarithromycin at 50, 100, 200, or 300 mg/kg of body weight administered daily by gavage to mice infected with approximately 10(7) viable MAC. A dose-related reduction in spleen and liver cell counts was noted with treatment at 50, 100, and 200 mg/kg. The difference in cell counts between treatment at 200 and 300 mg/kg was not significant. Clarithromycin at 200 mg/kg of body weight was found to have activity against three additional MAC isolates (MICs for the isolates ranged from 1 to 4 micrograms/ml by broth dilution). Clarithromycin at 200 mg/kg in combination with amikacin, ethambutol, temafloxacin, or rifampin did not result in increased activity beyond that seen with clarithromycin alone. Clarithromycin in combination with clofazimine or rifabutin resulted in an increase in activity beyond that seen with clarithromycin alone. The combination of clarithromycin with clofazimine or rifabutin should be considered for evaluation in the treatment of human MAC infections.
Selective inhibition of human immunodeficiency viruses by racemates and enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine
Authors: Schinazi R F , McMillan A , Cannon D , Mathis R , Lloyd R M , Peck A , Sommadossi J P , St Clair M , Wilson J , Furman P A
Published: June 2012

2',3'-Dideoxy-5-fluoro-3'-thiacytidine (FTC) has been shown to be a potent and selective compound against human immunodeficiency virus type 1 in acutely infected primary human lymphocytes. FTC is also active against human immunodeficiency virus type 2, simian immunodeficiency virus, and feline immunodeficiency virus in various cell culture systems, including human monocytes. The antiviral activity can be prevented by 2'-deoxycytidine, but not by other natural nucleosides, suggesting that FTC must be phosphorylated to be active and 2'-deoxycytidine kinase is responsible for the phosphorylation. By using chiral columns or enzymatic techniques, the two enantiomers of FTC were separated. The (-)-beta-enantiomer of FTC was about 20-fold more potent than the (+)-beta-enantiomer against human immunodeficiency virus type 1 in peripheral blood mononuclear cells and was also effective in thymidine kinase-deficient CEM cells. Racemic FTC and its enantiomers were nontoxic to human lymphocytes and other cell lines at concentrations of up to 100 microM. Studies with human bone marrow cells indicated that racemic FTC and its (-)-enantiomer had a median inhibitory concentration of > 30 microM. The (+)-enantiomer was significantly more toxic than the (-)-enantiomer to myeloid progenitor cells. The susceptibilities to FTC of pretherapy isolates in comparison with those of posttherapy 3'-azido-3'-deoxythymidine-resistant viruses in human lymphocytes were not substantially different. Similar results were obtained with well-defined 2',3'-dideoxyinosine- and nevirapine-resistant viruses. (-)-FTC-5'-triphosphate competitively inhibited human immunodeficiency virus type 1 reverse transcriptase, with an inhibition constant of 2.9 microM, when a poly(I)n.oligo(dC)19-24 template primer was used. These results suggest that further development of the (-)-Beta-enantiomer of FTC is warranted as an antiviral agent for infections caused by human immunodeficiency viruses.
Pharmacokinetics and metabolism of racemic 2',3'-dideoxy-5-fluoro-3'-thiacytidine in rhesus monkeys
Authors: Schinazi R F , Boudinot F D , Ibrahim S S , Manning C , McClure H M , Liotta D C
Published: June 2012

2',3'-Dideoxy-5-fluoro-3'-thiacytidine (FTC) is a nucleoside analog that selectively inhibits human immunodeficiency and hepatitis B viruses in vitro. In this study, the preclinical pharmacokinetics of racemic FTC in rhesus monkeys following intravenous and oral administration were characterized. The terminal half-life of FTC was independent of the route of administration and averaged 1.34 +/- 0.18 h (mean +/- standard deviation). Total clearance of FTC was moderate to high, averaging 1.49 +/- 0.24 liters/h/kg. Qualitative assessment of urine samples suggests that renal excretion of unchanged FTC was the major route of elimination of the nucleoside. The compound was also eliminated by metabolism and the deaminated biotransformation product 2,3'-dideoxy-5-fluoro-3'-thiauridine (FTU) was detected in serum and urine. This metabolite has no antiviral activity in human lymphocytes and liver cells. FTC and the metabolite FTU were conjugated, to a minor extent yielding the corresponding glucuronides. No 5-fluorouracil was detected in serum or urine. This is consistent with chromatographic studies using a chiral column that indicated that when racemic FTC is treated with cellular cytidine-deoxycytidine deaminase, the D-(+)-enantiomer of FTC is slowly deaminated to D-(+)-FTU, whereas the L-(-)-enantiomer is essentially resistant to this enzyme. The steady-state volume of distribution of FTC in serum averaged 2.23 +/- 0.42 liters/kg, and the nucleoside analog was distributed into the cerebrospinal fluid, which suggests that this drug penetrated the blood-brain barrier. Absorption of FTC after oral administration was rapid, with bioavailability averaging 73 +/- 6%. Taken together, the results indicate that the unusual L-(-)-enantiomer of FTC should be evaluated further in rhesus monkeys prior to determination of whether this compound is useful for treatment of human immunodeficiency and hepatitis B virus infections.
Pharmacokinetics and inflammatory fluid penetration of sparfloxacin
Authors: Johnson J H , Cooper M A , Andrews J M , Wise R
Published: June 2012

A single 400-mg oral dose of sparfloxacin was given to each of six healthy male volunteers, and the concentrations of the drug were measured in plasma, cantharides-induced inflammatory fluid, and urine over the subsequent 52 h. The mean peak concentration in plasma of 1.6 micrograms/ml was attained at a mean time of 2.7 h postdose. The mean peak concentration in inflammatory fluid of 1.3 micrograms/ml was attained at a mean time of 5 h postdose. The mean elimination half-life in plasma was 17.6 h, and that in inflammatory fluid was 19.7 h. The overall penetration into inflammatory fluid was 117%. Urinary recovery within the first 52 h postdose was 8.8% of the administered dose. Our results indicate that a once-daily dosage of sparfloxacin should be adequate to treat systemic infections caused by most common bacterial pathogens.
Steady-state pharmacokinetics and sputum penetration of lomefloxacin in patients with chronic obstructive pulmonary disease and acute respiratory tract infections
Authors: Kovarik J M , Hoepelman A I , Smit J M , Sips P A , Rozenberg-Arska M , Glerum J H , Verhoef J
Published: June 2012

Oral doses of 400 mg of lomefloxacin were administered once daily prior to breakfast to 10 middle-aged to elderly hospitalized patients with chronic obstructive pulmonary disease during treatment for bronchopulmonary infections. Serial plasma and sputum samples and fractional urine samples were obtained over a steady-state dosing interval. Lomefloxacin concentrations were determined in duplicate by a validated agar well diffusion microbiological assay. The maximum plasma lomefloxacin concentration (4.5 +/- 1.8 mg/liter), the time of occurrence of the maximum concentration (1.7 +/- 1.6 h), and the apparent volume of distribution associated with the terminal phase (2.19 +/- 1.05 liter/kg) were comparable to the values reported for healthy, young volunteers. Compared with the data reported for young adults, the elimination half-life (12.7 +/- 4.67 h) was longer and the apparent total body clearance (132 +/- 36.6 ml/min/1.73 m2) was lower in middle-aged to elderly patients. These differences were most likely attributable to age-related decreases in renal function, as evidenced by the lower lomefloxacin renal clearance (70.3 +/- 33.5 ml/min) in patients. The presence of acute respiratory infection per se did not appear to alter lomefloxacin pharmacokinetics. The peak lomefloxacin concentration in purulent, expectorated sputum samples of 4.3 +/- 1.2 mg/liter occurred 3.1 +/- 1.7 h after dose administration and subsequently declined to 1.7 +/- 0.5 mg/liter at the end of the 24-h dosing interval. The percent penetration into sputum, as assessed by comparing the area under the curve for sputum and plasma samples, was 120 +/- 39.8 (range, 70 to 185). The steady-state lomefloxacin concentrations in plasma and sputum samples from ill, older patients were in excess of the MICs for 90% of the strains tested of common, susceptible respiratory pathogens over most of the dosing interval.
Pharmacokinetics of a clarithromycin suspension in infants and children
Authors: Gan V N , Chu S Y , Kusmiesz H T , Craft J C
Published: June 2012

The single- and multiple-dose pharmacokinetics of clarithromycin and its 14-(R)-hydroxylated metabolite in infants and children were studied after oral administration under fasting and nonfasting conditions. Drug absorption appeared to be rapid following a brief delay in its onset; the mean peak concentrations in plasma (Cmax) for clarithromycin were reached within about 3 h under both conditions. The mean Cmax for the parent drug were 3.59 and 4.58 micrograms/ml in single-dose fasting and nonfasting patients, and the respective Cmax for the metabolite were 1.19 and 1.26 micrograms/ml. Data indicate good absorption and no significant effects by food. There was no unusual accumulation in the area under the concentration-time curve and Cmax in the multiple-dose group.
Penetration of vancomycin in uninfected sternal bone
Authors: Massias L , Dubois C , de Lentdecker P , Brodaty O , Fischler M , Farinotti R
Published: June 2012

Concentrations of vancomycin in sternal bones of 10 patients undergoing cardiac surgery were studied at steady state, 48 h after starting intravenous prophylaxis. A sample of sternal bone was taken before (group I) or after (group II) cardiopulmonary bypass. The mean vancomycin concentrations in sternal bones were not significantly different between the groups and were 9.3 +/- 3.0 micrograms/g. The concentrations of vancomycin in sternal bones were always above the MICs for staphylococci, streptococci, and enterococci.
Characterization of an azole-resistant Candida glabrata isolate
Authors: vanden Bossche H , Marichal P , Odds F C , Le Jeune L , Coene M C
Published: June 2012

A Candida (Torulopsis) glabrata strain (B57149) became resistant to fluconazole after a patient carrying the organism was treated with the drug at 400 mg once daily for 9 days. Growth of the pretreatment isolate (B57148) was inhibited by 50% with 0.67 microM ketoconazole, 1.0 microM itraconazole, and 43 microM fluconazole, whereas growth of B57149 was inhibited slightly by 10 microM ketoconazole but was unaffected by 10 microM itraconazole or 100 microM fluconazole. This indicates cross-resistance to all three azole antifungal agents. The cellular fluconazole content of B57149 was from 1.5- to 3-fold lower than that of B57148, suggesting a difference in drug uptake between the strains. However, this difference was smaller than the measured difference in susceptibility and, therefore, cannot fully explain the fluconazole resistance of B57149. Moreover, the intracellular contents of ketoconazole and itraconazole differed by less than twofold between the strains, so that uptake differences did not account for the azole cross-resistance of B57149. The microsomal cytochrome P-450 content of B57149 was about twice that of B57148, a difference quantitatively similar to the increased subcellular ergosterol synthesis from mevalonate or lanosterol. These results indicate that the level of P-450-dependent 14 alpha-demethylation of lanosterol is higher in B57149. Increased ergosterol synthesis was also seen in intact B57149 cells, and this coincided with a decreased susceptibility of B57149 toward all three azoles and amphotericin B. B57149 also had higher squalene epoxidase activity, and thus, more terbinafine was needed to inhibit the synthesis of 2,3-oxidosqualene from squalene. P-450 content and ergosterol synthesis both decreased when isolate B57149 was subcultured repeatedly on drug-free medium. This repeated subculture also fully restored the strain's itraconazole susceptibility, but only partly increased its susceptibility to fluconazole. The results suggest that both lower fluconazole uptake and increased P-450-dependent ergosterol synthesis are involved in the mechanism of fluconazole resistance but that only the increased ergosterol synthesis contributes to itraconazole cross-resistance.
Relationships among antibacterial activity, inhibition of DNA gyrase, and intracellular accumulation of 11 fluoroquinolones
Authors: Bazile S , Moreau N , Bouzard D , Essiz M
Published: June 2012

A series of 11 fluoroquinolone antibacterial agents, including 8 newly synthesized molecules and 3 reference compounds (pefloxacin, ciprofloxacin, and sparfloxacin), were tested for their MICs against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The intracellular accumulation of fluoroquinolones by these microorganisms was measured by centrifugation through silicone oil and a fluorescence assay. The minimal effective dose (MED) was determined for all agents in a supercoiling assay with E. coli DNA gyrase. The hydrophobicities of the quinolones were determined and expressed as the logarithm of the coefficient of distribution (log D) between 1-octanol and phosphate buffer (pH 7.2). No correlation was found between MICs and cell accumulation for the quinolones studied. A correlation was found between log D and accumulation by S. aureus (r = 0.71, n = 11), and an inverse correlation was found between log D and accumulation by E. coli (r = 0.73, n = 11) and P. aeruginosa (r = 0.64, n = 10). The correlation coefficients between MICs and MED for E. coli, which were 0.60, 0.64, and 0.74 (n = 11) for E. coli, P. aeruginosa, and S. aureus, respectively, rose to 0.85, 0.74, and 0.74 (n = 11) for the same microorganisms, respectively, when the accumulation of the drug by the cell was taken into account. It was concluded that the inhibitory activity against DNA gyrase remains the most important parameter for quinolone potency, but that intracellular accumulation must be taken into account, since, for a given organism, both parameters are under the control of the physicochemical properties of the quinolones.
Prospective observational study of Klebsiella bacteremia in 230 patients: outcome for antibiotic combinations versus monotherapy
Authors: Korvick J A , Bryan C S , Farber B , Beam T R , Schenfeld L , Muder R R , Weinbaum D , Lumish R , Gerding D N , Wagener M M
Published: June 2012

Combination antimicrobial agent therapy has been advocated for treatment of gram-negative bacteremia, including that caused by Klebsiella spp. We performed a prospective, observational, 10-hospital collaborative study to evaluate the efficacy of antibiotic combination therapy versus that of monotherapy for 230 consecutive patients with Klebsiella bacteremia. The species involved were K. pneumoniae (82%), K. oxytoca (15%), and K. ozaenae (0.4%). Of the bacteremias, 26% were polymicrobial in nature. A total of 53% of cases were nosocomial infections. The most common portals were the urinary tract (28%), biliary tract (12%), lung (10%), and abdomen (9%). Some 49 and 51% of the patients had received monotherapy and antibiotic combination therapy (beta-lactam plus aminoglycoside), respectively; 14-day mortalities in the two groups were 20 and 18%, respectively. However, for the subgroup of patients who experienced hypotension within 72 h prior to or on the day of the positive blood culture, those patients who received combination therapy experienced significantly lower mortality (24%) than did those who received monotherapy (50%). We conclude that monotherapy with an antibiotic that is active in vitro against Klebsiella (beta-lactam or aminoglycoside) is sufficient therapy for less severely ill patients (immunocompetent, urinary tract portal, mentally alert, normal vital signs). On the other hand, for severely ill patients who experience hypotension, antibiotic combination therapy with a beta-lactam and an aminoglycoside agent is preferred.
Pharmacokinetics and transplacental passage of imipenem during pregnancy
Authors: Heikkilä A , Renkonen O V , Erkkola R
Published: June 2012

Imipenem pharmacokinetics were studied in early pregnancy (n = 7; length of gestation, 8.6 +/- 1.5 weeks, mean +/- standard deviation), in late pregnancy (n = 7; length of gestation, 38.7 +/- 1.4 weeks), and in the nonpregnant state (n = 6). A single dose of 500 mg of imipenem-cilastatin (1:1) was administered as a 20-min infusion. Multiple plasma and urine samples, as well as specimens of umbilical plasma and amniotic fluid from the pregnant subjects, were collected at frequent intervals for 8 h. Imipenem concentrations were assayed by specific microbiologic assay. The mean peak concentrations in plasma were 14.7 +/- 4.9, 14.9 +/- 5.2, and 43 +/- 28.3 micrograms/ml in early pregnancy, late pregnancy, and the nonpregnant state, respectively. The volumes of distribution were significantly larger during early pregnancy (0.98 +/- 0.45 liter/kg of body weight, P < 0.005) and late pregnancy (0.59 +/- 0.19 liter/kg, P < 0.05) than in the nonpregnant state (0.33 +/- 0.10 liter/kg), and total clearances from plasma were faster in early pregnancy (12.7 +/- 7.8 ml min-1 kg-1, P < 0.05) and late pregnancy (10.7 +/- 4.6 ml min-1 kg-1, P < 0.05) than in the nonpregnant state (5.77 +/- 1.19 ml min-1 kg-1). The mean concentrations in amniotic fluid were 0.07 +/- 0.01 and 0.72 +/- 0.85 micrograms/ml in early and late pregnancy. The mean umbilical venous and arterial drug concentrations were 1.72 +/- 1.22 and 1.64 +/- 1.22 micrograms/ml. The feto-maternal ratio at the time of cesarean section was 0.33 +/- 0.12. These results indicate that an adjustment of doses of imipenem may be required when treating pregnant women because of considerable changes in imipenem pharmacokinetics during pregnancy.
The anti-hepatitis B virus activities, cytotoxicities, and anabolic profiles of the (-) and (+) enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine
Authors: Furman P A , Davis M , Liotta D C , Paff M , Frick L W , Nelson D J , Dornsife R E , Wurster J A , Wilson L J , Fyfe J A
Published: June 2012

The anti-hepatitis B (anti-HBV) activities of the (-) and (+) enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine (2'-deoxy-3'-thia-5-fluorocytosine [FTC]) were studied by using an HBV-transfected cell line (HepG2 derivative 2.2.15, subclone P5A). The (-) isomer was found to be a potent inhibitor of viral replication, with an apparent 50% inhibitory concentration of 10 nM, while the (+) isomer was found to be considerably less active. Both isomers showed minimal toxicity to HepG2 cells (50% inhibitory concentration, > 200 microM) and showed minimal toxicity in the human bone marrow progenitor cell assay. In accord with the cellular antiviral activity data, the 5'-triphosphate of (-)-FTC inhibited viral DNA synthesis in an endogenous HBV DNA polymerase assay, while the 5'-triphosphate of the (+) isomer was inactive. Unphosphorylated (-)-FTC did not inhibit product formation in the endogenous assay, suggesting that the antiviral activity of the compound is dependent on anabolism to the 5'-triphosphate. Both (-)- and (+)-FTC were anabolized to the corresponding 5'-triphosphates in chronically HBV-infected HepG2 cells. The rate of accumulation and the steady-state concentration of the 5'-triphosphate of (-)-FTC were greater. Also, (-)-FTC was not a substrate for cytidine deaminase and, therefore, is not subject to deamination and conversion to an inactive uridine analog. The (+) isomer is, however, a good substrate for cytidine deaminase.
In vitro pharmacodynamic effects of concentration, pH, and growth phase on serum bactericidal activities of daptomycin and vancomycin
Authors: Lamp K C , Rybak M J , Bailey E M , Kaatz G W
Published: June 2012

Clinical trials with daptomycin were halted in December 1990 because of treatment failures including two resistant Staphylococcus aureus strains. High protein binding of daptomycin (> 90%) and the lower-than-expected concentrations in serum with the dosage regimen of 3 mg/kg of body weight every 12 h may have contributed to these failures. To evaluate the effect that higher concentrations would have on bactericidal activity measured by time-kill curves, peak and trough concentrations were estimated for dosage regimens of 3, 5, and 10 mg/kg every 12 h. MICs, MBCs, and killing curves for daptomycin and vancomycin were performed by using the estimated concentrations with four S. aureus strains obtained from patients who failed daptomycin therapy for endocarditis. MICs and MBCs of daptomycin demonstrated a greater inoculum effect than those of vancomycin; MICs and MBCs of daptomycin increased three- to fourfold, but those of vancomycin increased only one- to twofold when the inoculum was increased from 5 x 10(5) to 5 x 10(7) CFU/ml. No pH-dependent effect on MICs or MBCs was seen. Strenuous experimental conditions were chosen: high inoculums (5 x 10(7) CFU/ml), extremes of pH (6.4, 7.4, and 8), and stationary and exponentially growing organisms; and all experiments completed in the presence of pooled human serum. Daptomycin exhibited concentration-dependent killing and statistically faster kill rates than vancomycin against stationary- or exponential-growth-phase organisms. A pH-dependent decrease in activity with daptomycin was also demonstrated. Daptomycin and vancomycin produced higher kill rates against exponentially growing organisms. A pH-dependent decrease in activity with daptomycin was also demonstrated. Daptomycin and vancomycin produced higher kill rates against exponentially growing organisms. The results indicate that the use of higher dosage regimens with compounds similar to daptomycin may be capable of overcoming the effects of pH, high inoculum, and protein binding.
Fluoxetine hydrochloride enhances in vitro susceptibility to chloroquine in resistant Plasmodium falciparum
Authors: Gerena L , Bass G T , Kyle D E , Oduola A M , Milhous W K , Martin R K
Published: June 2012

The emergence of chloroquine resistance in Plasmodium falciparum has necessitated the development of alternate strategies for chemotherapy and chemoprophylaxis. One approach has been the identification of drugs that do not possess any intrinsic antimalarial activity when used alone but that potentiate the effect of currently available antimalarial drugs, such as chloroquine. We identified fluoxetine hydrochloride (Prozac), a commonly prescribed antidepressant, as another resistance modulator for drug-resistant P. falciparum. Studies with chloroquine-resistant clones and isolates from various geographical locations confirmed our initial observations with a chloroquine-resistant P. falciparum clone, W2. Fluoxetine concentrations of 500 nM were found to effectively modulate chloroquine resistance by 66% in clone W2. In comparison, verapamil at similar concentrations was observed to modulate chloroquine resistance in clone W2 by 61%. Neither fluoxetine nor verapamil was observed to possess any innate antimalarial activity. These data augment the current description of the chloroquine resistance phenotype and may provide additional insights into lead-directed synthesis of new antimalarial drugs.
Interleukin-1-induced nonspecific resistance to bacterial infection in mice is not mediated by glucocorticosteroids
Authors: Vogels M T , Sweep C G , Hermus A R , van der Meer J W
Published: June 2012

Preexposure to a low dose of interleukin-1 (IL-1; 3 to 30 micrograms/kg) 24 h before a lethal gram-negative bacterial infection prolonged survival in normal and granulocytopenic mice. To examine whether this protective effect is mediated by glucocorticosteroids, we first measured corticosterone concentrations in mice after administration of 80 and 800 ng of IL-1. IL-1 induced a dose-dependent increase in corticosterone levels in plasma. Next, the corticosterone peak induced by a protective dose of IL-1 (800 ng) was simulated by administration of synthetic human adrenocorticotropic hormone 1-24 (ACTH) in normal and neutropenic mice. Although corticosterone levels induced by pretreatment with IL-1 or ACTH were virtually identical, the ACTH-induced corticosterone peak was not associated with protection against Klebsiella pneumoniae infection in normal mice and Pseudomonas aeruginosa infection in neutropenic mice. This indicates that the protective effect of IL-1 pretreatment against gram-negative bacterial infection is not mediated by elevated levels of glucocorticosteroids. In addition, we found that plasma corticosterone concentrations during K. pneumoniae infection were significantly lower after pretreatment with IL-1 than after pretreatment with ACTH or vehicle, probably reflecting the better physical condition of IL-1-treated mice.
Pharmacokinetics of meropenem (ICI 194,660) and its metabolite (ICI 213,689) in healthy subjects and in patients with renal impairment
Authors: Leroy A , Fillastre J P , Borsa-Lebas F , Etienne I , Humbert G
Published: June 2012

The pharmacokinetics of meropenem (ICI 194,660) and its open-ring metabolite (ICI 213,689) were studied in 6 healthy volunteers and 16 patients with moderate to severe renal impairment after a single intravenous dose of 500 mg given as a 30-min infusion. Concentrations of unchanged meropenem in plasma and urine were measured by both microbiological and high-pressure liquid chromatographic (HPLC) assays. A good correlation was found between the two techniques. Pharmacokinetic parameters of unchanged meropenem were determined by using the HPLC data. The terminal half-life of unchanged meropenem increased in relation to the degree of renal impairment, being 1.2 h in subjects with normal renal function and 10 h in patients with end-stage renal failure. Total body clearance and renal clearance of unchanged meropenem are linearly related to creatinine clearance. The concentrations of the metabolite in plasma, which are very low in healthy subjects, significantly increased in uremic patients. The apparent half-life of ICI 213,689 increased in uremic patients and was about 35 h in patients with severe renal insufficiency. Meropenem and its metabolite are effectively removed by hemodialysis. The dialysis clearance of the unchanged drug was 81 +/- 22 ml/min. Dosage adjustments of meropenem will be necessary in patients with severe renal impairment.
Efficacies of liposome-encapsulated streptomycin and ciprofloxacin against Mycobacterium avium-M. intracellulare complex infections in human peripheral blood monocyte/macrophages
Authors: Majumdar S , Flasher D , Friend D S , Nassos P , Yajko D , Hadley W K , Düzgüneş N
Published: June 2012

Current treatments of disseminated infection caused by the Mycobacterium avium-M. intracellulare complex (MAC) are generally ineffective. Liposome-mediated delivery of antibiotics to MAC-infected tissues in vivo can enhance the efficacy of the drugs (N. Düzgüneş, V. K. Perumal, L. Kesavalu, J. A. Goldstein, R. J. Debs, and P. R. J. Gangadharam, Antimicrob. Agents Chemother. 32:1404-1411, 1988; N. Düzgüneş, D. A. Ashtekar, D. L. Flasher, N. Ghori, R. J. Debs, D. S. Friend, and P. R. J. Gangadharam, J. Infect. Dis. 164:143-151, 1991). We investigated the therapeutic efficacies of liposome-encapsulated streptomycin and ciprofloxacin against growth of the MAC inside human peripheral blood monocyte/macrophages. Treatment was initiated 24 h after infection of macrophages with the MAC and stopped after 20 h, and the cells were incubated for another 7 days. The antimycobacterial activity of streptomycin was enhanced when the drug was delivered to macrophages in liposome-encapsulated form, reducing the CFU about threefold more than the free drug did throughout the concentration range studied (10 to 50 micrograms/ml). With 50 micrograms of encapsulated streptomycin per ml, the CFU were reduced to 11% of the initial level of infection. Liposome-encapsulated ciprofloxacin was at least 50 times more effective against the intracellular bacteria than was the free drug: at a concentration of 0.1 microgram/ml, liposome-encapsulated ciprofloxacin had greater antimycobacterial activity than the free drug at 5 microgram/ml. With liposome-encapsulated ciprofloxacin at 5 micrograms/ml, the CFU were reduced by more than 1,000-fold at the end of the 7-day incubation period, compared with untreated controls. These results suggest that liposome-encapsulated ciprofloxacin or other fluoroquinolones may be effective against MAC infections in vivo.
Antimicrobial susceptibilities of Campylobacter jejuni and Campylobacter coli isolated in Sweden: a 10-year follow-up report
Authors: Sjögren E , Kaijser B , Werner M
Published: June 2012

Resistance to erythromycin and doxycycline and more recently to fluoroquinolones has been reported to occur in Campylobacter spp. both in vitro and in patients treated with these antibiotics. The frequency of resistance to 14 antimicrobial agents in Campylobacter jejuni and Campylobacter coli isolated from patients infected in Sweden or abroad is described. For some agents, a comparison of susceptibility in strains of Campylobacter spp. isolated in 1978 with those isolated in 1988 is made. No general increase in in vitro resistance to antibiotics commonly used for the treatment of human gastroenteritis caused by C. jejuni or C. coli has occurred during the last 10 years in Sweden, which might be a consequence of strict antibiotic control. The numbers of strains from 1988 to 1989 resistant to ciprofloxacin and to norfloxacin included in this study (0.7 and 1.4%, respectively) are still fewer than those that were resistant to erythromycin (7.3%) or doxycycline (12.4%). There is, however, since 1989 to 1990 an indication of increasing resistance to these antibiotics.
In vitro antibiotic susceptibilities of Neisseria gonorrhoeae isolates in the Philippines
Authors: Clendennen T E , Hames C S , Kees E S , Price F C , Rueppel W J , Andrada A B , Espinosa G E , Kabrerra G , Wignall F S
Published: June 2012

Antibiotic susceptibility surveillance testing was performed on clinical isolates of Neisseria gonorrhoeae collected in September 1989 in the Philippines. beta-Lactamase was produced by 77 (55%) of 140 isolates. In vitro MIC testing revealed significant resistance to penicillin (MIC for 90% of isolates [MIC90], greater than 64 micrograms/ml), tetracycline (MIC90, 4 micrograms/ml), and cefmetazole (MIC90, 8 micrograms/ml). Spectinomycin resistance was rare (10 of 117), but the MIC90 was 32 micrograms/ml. Isolates were susceptible to fluoroquinolones and cephalosporins at the time of this survey, as evidenced by the MIC90s of ciprofloxacin (0.25 microgram/ml), norfloxacin (2.0 micrograms/ml), ofloxacin (0.625 microgram/ml), cefpodoxime (2.0 micrograms/ml), cefotaxime (1.0 microgram/ml), ceftazidime (0.25 microgram/ml), ceftizoxime (0.25 microgram/ml), and ceftriaxone (0.06 microgram/ml). To date, ceftriaxone resistance has not emerged, despite the widespread use of this antibiotic in the Philippines.
In vitro activities of three semisynthetic amide derivatives of teicoplanin, MDL 62208, MDL 62211, and MDL 62873
Authors: Biavasco F , Lupidi R , Varaldo P E
Published: June 2012

MDL 62208, MDL 62211, and MDL 62873 are three semisynthetic amide derivatives of teicoplanin (MDL 62208 is an amide of teicoplanin aglycone, MDL 62211 is an amide of the teicoplanin A2 complex, and MDL 62873 is the corresponding derivative of peak A2-2 of the complex). The three semisynthetic glycopeptides were evaluated for in vitro antibacterial activity in comparison with the parent drug (teicoplanin) and vancomycin. A variety of gram-positive bacteria of clinical origin, whose species were carefully determined and that included 428 staphylococci (207 methicillin susceptible and 221 methicillin resistant), 41 streptococci, 82 enterococci, 43 strains of Listeria monocytogenes, 10 JK coryneform bacteria, and 67 anaerobes belonging to the genera Clostridium, Propionibacterium, Peptostreptococcus, and Eubacterium, were tested. The only resistances to MDL 62208, MDL 62211, and MDL 62873 were encountered with vancomycin- and teicoplanin-resistant enterococci. All of the other test strains, including some teicoplanin-resistant coagulase-negative staphylococci of the species Staphylococcus haemolyticus and Staphylococcus epidermidis, were highly susceptible to the three teicoplanin amides. Only minor differences in activity were observed among MDL 62208, MDL 62211, and MDL 62873, whereas the three experimental compounds were usually found to be more potent than teicoplanin or vancomycin (especially against staphylococci, with differences mostly ranging from 2- to 16-fold). The MBC-to-MIC ratios varied depending on the organisms, with the highest ratios usually observed for enterococci and listeriae. Overall, the MBC-to-MIC ratios yielded by the teicoplanin analogs were slightly greater than those yielded by teicoplanin or vancomycin.
Pharmacokinetics and distribution over the blood brain barrier of two acyclic guanosine analogs in rats, studied by microdialysis
Authors: Ståhle L , Oberg B
Published: June 2012

The free extracellular concentrations of acyclovir and (R)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) in the blood and in brain tissue of rats were measured in microdialysis samples by high-pressure liquid chromatography with UV detection. The half-life of acyclovir in blood was 2 h, while that of H2G was 28 min. The concentration attained in the brain compared with the concentration in blood was slightly lower for H2G than for acyclovir. The results show that the pharmacokinetic profiles of acyclic nucleosides may vary as a consequence of the structure of the acyclic chain corresponding to the sugar moiety.
Pentoxifylline modulates activation of human neutrophils by amphotericin B in vitro
Authors: Sullivan G W , Carper H T , Mandell G L
Published: June 2012

The antifungal agent amphotericin B (AmB) alters neutrophil (polymorphonuclear leukocyte [PMN]) function, and this may be the mechanism for some of the adverse effects caused by AmB. AmB is a potent inhibitor of PMN migration, increases PMN adherence and aggregation, and primes PMN for increased oxidative activity in response to a second stimulus. AmB also stimulates mononuclear leukocytes (MNLs) to release inflammatory mediators which augment the effects of AmB on PMN function. In the present study, we observed that the methylxanthine derivative pentoxifylline decreased the effects of AmB on PMN function. AmB (2 micrograms/ml) priming doubled PMN chemiluminescence stimulated by fMet-Leu-Phe. In the presence of MNLs, AmB priming increased fMet-Leu-Phe-stimulated PMN chemiluminescence to 622% of unprimed PMN activity. Pentoxifylline (100 microM) blunted the rise in AmB-augmented PMN chemiluminescence in the presence of MNLs to 282% of unprimed PMN activity, and pentoxifylline metabolites were active at 10 microM. Pentoxifylline (100 microM) also blocked AmB-augmented PMN oxidative activity in whole blood, as measured by nitroblue tetrazolium reduction. In the presence of MNL, AmB (2 micrograms/ml) doubled the expression of the important PMN adherence factor Mac-1. Pentoxifylline (1 mM) decreased AmB-stimulated PMN Mac-1 expression back to unstimulated amounts. In the presence of MNLs, AmB (2 micrograms/ml) decreased PMN nondirected and directed migration to fMet-Leu-Phe to 40 and 38% of control PMN migration, respectively. Pentoxifylline (300 microM) counteracted AmB inhibition of nondirected and directed migration to fMet-Leu-Phe, resulting in migration that was 71 and 87% of control PMN migration, respectively. In contrast, the methylxanthine caffeine (100 muM) increased AmB-enhanced chemiluminescence but did not affect AmB-inhibited PMN migration. Pentoxifylline should be evaluated as adjunctive therapy to lessen the inflammatory damage caused by AmB.
Antiviral activities of ribavirin, 5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide, and 6'-(R)-6'-C-methylneplanocin A against several ortho- and paramyxoviruses
Authors: Shigeta S , Mori S , Baba M , Ito M , Honzumi K , Nakamura K , Oshitani H , Numazaki Y , Matsuda A , Obara T
Published: June 2012

5-Ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide (EICAR) and 6'-(R)-6'-C-methylneplanocin A (TJ13025) are two novel antiviral agents which are targeted against IMP dehydrogenase and S-adenosylhomocysteine hydrolase, respectively. These compounds have been examined for their activities against various strains of orthomyxoviruses (influenza virus) and paramyxoviruses (parainfluenza virus, mumps virus, measles virus, and respiratory syncytial virus) in vitro. EICAR was 10- to 59-fold more active than ribavirin and TJ13025 was 32- to 330-fold more active than ribavirin against parainfluenza virus types (2 and 3), mumps virus, and measles virus. EICAR was also more active than ribavirin against respiratory syncytial virus and influenza virus, whereas TJ13025 was virtually inactive against these viruses. The 50% virus-inhibitory concentrations of EICAR and TJ13025 were generally within the 0.1- to 1-microgram/ml range. Although the compounds did not prove cytotoxic to stationary host cells (HeLa, Vero, MDCK, and LLCMK2) at a concentration of 200 micrograms/ml, concentrations of 4 to 13 micrograms/ml inhibited the growth of dividing cells. EICAR and TJ13025 should be further pursued as candidate drugs for the treatment of ortho- and paramyxovirus infections.
Utilization of pulse oximetry for the study of the inhibitory effects of antiviral agents on influenza virus in mice
Authors: Sidwell R W , Huffman J H , Gilbert J , Moscon B , Pedersen G , Burger R , Warren R P
Published: June 2012

Pulmonary disease in mice induced by influenza virus was monitored by measurement of oxygen saturation (SaO2) in blood with a pulse oximeter. The SaO2 declined in inverse proportion to the viral inoculum. The known antiviral agent ribavirin inhibited the SaO2 decline, prevented death, lowered lung consolidation, and reduced the level of recoverable virus. Pulse oximetry is an effective means of monitoring murine influenzal disease and can be used in the study of potential antiviral drugs.
Effect of glycerol monolaurate on bacterial growth and toxin production
Authors: Schlievert P M , Deringer J R , Kim M H , Projan S J , Novick R P
Published: June 2012

Glycerol monolaurate (GML) is a naturally occurring surfactant that has potential use as an additive to tampons and wound dressings to reduce the incidence of certain bacterial toxin-mediated illnesses. In vitro studies were undertaken to evaluate the effect of GML on the growth of and toxin production by potentially pathogenic bacteria. GML inhibited the growth of clinical isolates of group A, B, F, and G streptococci at concentrations of 10 to 20 micrograms/ml. Exotoxin production, including that of pyrogenic exotoxins and hemolysins, was reduced by concentrations of GML that were below those inhibitory for growth as well as growth inhibitory. The growth of Staphylococcus aureus strains from patients with toxic shock syndrome and scalded skin syndrome was inhibited or delayed in the presence of 100 to 300 micrograms of GML per ml. Growth inhibition by GML could be overcome by the production of lipase. S. aureus elaboration of hemolysin, toxic shock syndrome toxin 1, and exfoliative toxin A was inhibited at GML concentrations below those necessary to inhibit growth. Results similar to those for S. aureus were obtained in tests of S. hominis. Escherichia coli growth and Salmonella minnesota growth were unaffected by GML, but an S. minnesota Re mutant was susceptible to growth-inhibitory activity. Endotoxin release into the medium from E. coli cells was also unaffected by GML, but the release or activity of E. coli hemolysin was increased by GML. Streptococcal pyrogenic endotoxin A production by an E. coli clone was not affectd by GML. These studies indicate that GML is effective in blocking or delaying the production of exotoxins by pathogenic gram-positive bacteria.