bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Plasmodium falciparum thymidylate synthase: interactions with high-affinity metabolites of 5-fluoroorotate and D1694
Authors: Hekmat-Nejad M , Rathod P K
Published: October 2018

Consistent with a proposed mechanism for the potent antimalarial activity of 5-fluoroorotate, 5-fluoro-2'-deoxyuridylate inhibited Plasmodium falciparum thymidylate synthase with a Ki of 2 nM. Steady-state kinetics revealed no significant differences between malarial and mammalian thymidylate synthases. Thus, additional biochemical parameters must underlie the selective antimalarial activity of 5-fluoroorotate. A polyglutamylated folate analog, D1694-(glu)4, was also a potent inhibitor of malarial thymidylate synthase (Kis = 1.5 nM).
Antipneumococcal activities of RP 59500 (quinupristin-dalfopristin), penicillin G, erythromycin, and sparfloxacin determined by MIC and rapid time-kill methodologies
Authors: Pankuch G A , Lichtenberger C , Jacobs M R , Appelbaum P C
Published: October 2018

Previous time-kill studies have shown that RP 59500 is rapidly bactericidal against pneumococci. To extend these findings, the activities of RP 59500, its two components RP 57669 RP 54476, penicillin G, erythromycin and sparfloxacin against 26 penicillin-susceptible, 25 penicillin-intermediate, and 25 penicillin-intermediate, and 25 penicillin-resistant pneumococci were determined by the agar dilution MIC and the time-kill testing methodologies within 10 min (ca. 0.2 h) and at 1 and 2 h. Respective agar dilution MICs at which 90% of isolates are inhibited for penicillin-susceptible, -intermediate, and -resistant strains were as follows: penicillin G, 0.03, 1, and 4 micrograms/ml;RP 59500, 1, 1, and 1 microgram/ml; RP 57669, 8, 32, and 16 micrograms/ml; RP 54476, > 128, > 128, and > 128 micrograms/ml; erythromycin, 0.06, 2, and > 128 micrograms/ml; and sparfloxacin, 1, 0.5, and 0.5 microgram/ml. RP 59500 was equally active (MIC at which 90% of isolates are inhibited, 1.0 microgram/ml) against erythromycin-susceptible and -resistant strains. Time-kill testing results showed that only RP 59500 at one to four times the MIC killed pneumococci at 0.2 h; RP 59500 was also the most active compound at 1 and 2 h. By comparison, penicillin and sparfloxacin at one, two, and four times the MICs reduced the original inoculum by > or = 1 log at 2 h for 46, 80, and 95% and for 50, 72, and 86% of strains, respectively. The killing activity of RP 59500 was the same against erythromycin-susceptible and -resistant strains. RP 57669, RP 54479, and erythromycin were either inactive or bacteriostatic at 2 h. Of all drugs tested, RP 59500 yielded the most rapid killing.
Canadian ciprofloxacin susceptibility study: comparative study from 15 medical centers. Canadian Ciprofloxacin Study Group
Authors: Blondeau J M , Yaschuk Y
Published: October 2018

We tested 4,507 microorganisms, from 15 Canadian medical centers, against ciprofloxacin and several other antimicrobial agents to determine the in vitro susceptibilities. Overall, susceptibility of members of the family Enterobacteriaceae to ciprofloxacin was 97%; Moraxella and Haemophilus spp. had susceptibilities of 98 and 99%, respectively; and P. aeruginosa and S. aureus had susceptibilities of 79 and 96%, respectively.
Isoniazid induces expression of the antigen 85 complex in Mycobacterium tuberculosis
Authors: Garbe T R , Hibler N S , Deretic V
Published: October 2018

Exposure to isoniazid induced the expression of several secreted proteins in Mycobacterium tuberculosis H37Rv. Two-dimensional gel electrophoresis and immunoblot analyses indicated that two of the prominent isonicotinic acid hydrazide-inducible polypeptides were members of the antigen 85 complex, recently demonstrated to have mycolyltransferase activity. We postulate the existence of an intermediate, whose production is inhibited by isonicotinic acid hydrazide, which plays a negative feedback regulatory role in the metabolism of mycolic acids are revealed by the overexpression of the antigen 85 complex. The approach described here relies on analyses of differential gene expression following exposure to inhibitors and may become a more general tool in dissecting the effects of antimicrobial agents.
Effects of two oral erythromycin ethylsuccinate formulations on the motility of the small intestine in human beings
Authors: Caron F , Bouaniche M , Delatour F , Ducrotte P , Torlotin J C , Denis P , Humbert G , Rouveix B
Published: October 2018

Fourteen-membered macrolides are known to produce alterations in digestive tract motor activity; these include the induction of strong gastric contractions and a decrease in the motility of the small intestine. The aim of the study was to compare the effects of two different formulations of erythromycin ethylsuccinate (EE) on duodenojejunal motility. Compared with the more commonly used crystalline formulation of EE (CEE), the amorphous formulation (AEE) has previously been described to have greater bioavailability and to induce significantly fewer gastrointestinal side effects when given at therapeutic and what have been considered to be equivalent oral doses (i.e., CEE, 1,000 mg every 12 h; AEE, 500 mg every 12 h). In a crossover double-blind study, duodenojejunal manometric recordings were performed for 10 volunteers treated with placebo, CEE at 1,000 mg, or AEE at 500 mg. Recordings for each volunteer were obtained for a fed period after a standard dinner and then for a nocturnal fasting period. When compared with the placebo, CEE significantly decreased the motility index of the duodenum during the 30 min after the peak serum erythromycin concentrations, shortened the duration of the fed state, and had no effect during the fasting state. In contrast, AEE did not significantly modify any motility parameter. Because AEE produced significantly lower concentrations in serum than CEE, these results do not necessarily imply that the two formulations of EE act differently on the motility of the small intestine.
In vitro and in vivo activities of LB10522, a new catecholic cephalosporin
Authors: Kim M Y , Oh J I , Paek K S , Kim Y Z , Kim I C , Kwak J H
Published: October 2018

In vitro activity of LB10522 was compared with those of cefpirome, ceftazidime, ceftriaxone, and cefoperazone against clinical isolates. Against gram-positive bacteria, LB10522 was most active among the compounds tested. It was fourfold more active than cefpirome against methicillin-susceptible Staphylococcus aureus and Enterococcus faecalis. LB10522 was highly effective against most members of the family Enterobacteriaceae tested. Ninety percent of isolates of Escherichia coli, Klebsiella oxytoca, Proteus vulgaris, Proteus mirabilis, and Salmonella spp. were inhibited at a concentration of < or = 0.5 micrograms/ml. These activities were comparable to those of cefpirome. Against Pseudomonas aeruginosa, LB10522 with a MIC at which 90% of the isolates are inhibited of 2 micrograms/ml was 16- and 32-fold more active than ceftazidime and ceftazidime against systemic infections caused by Staphylococcus aureus giorgio, Streptococcus pneumoniae III, Pseudomonas aeruginosa 1912E, Escherichia coli 851E, Proteus mirabilis 1315E, Serratia marcescens 1826E, and Acinetobacter calcoaceticus Ac-54. LB10522 was very resistant to hydrolysis by various beta-lactamases such as TEM-3, TEM-7, SHV-1, FEC-1, and P-99. LB10522 did not induce beta-lactamase in Enterobacter cloacae 1194E, although most of the reference cephalosporins acted as inducers of beta-lactamase in this strain. Time-kill study showed that LB10522, at concentrations of two or four times the MIC, had a rapid bactericidal activity against Staphylococcus aureus 6538p, Escherichia coli 851E, and Pseudomonas aeruginosa 1912E.
Hydrophilicity of quinolones is not an exclusive factor for decreased activity in efflux-mediated resistant mutants of Staphylococcus aureus
Authors: Takenouchi T , Tabata F , Iwata Y , Hanzawa H , Sugawara M , Ohya S
Published: October 2018

The elevated expression of the norA gene is responsible for efflux-mediated resistance to quinolones in Staphylococcus aureus (E.Y.W. Ng, M. Trucksis, and D.C. Hooper, Antimicrob. Agents Chemother. 38:1345-1355, 1994). For S. aureus transformed with a plasmid containing the cloned norA gene, SA113(pTUS20) (H. Yoshida, M. Bogaki, S. Nakamura, K. Ubukata, and M. Konno, J. Bacteriol. 172:6942-6949, 1990), and an overexpressed mutant, SA-1199B (G.W. Kaatz, S.M. Seo, and C.A. Ruble, J. Infect. Dis. 163:1080-1086, 1991), the MICs of norfloxacin increased 16 and 64 times compared with its MICs for the recipient and wild-type strains, SA113 and SA-1199, respectively. MICs of CS-940, however, increased only two and eight times, even though these two fluoroquinolones are similarly hydrophilic (apparent logPs of approximately -1). No good correlation was found, among 15 developed and developing quinolones, between the increment ratio in MICs and hydrophobicity (r = 0.61). Analysis of the quantitative structure-activity relationship among 40 fluoroquinolones revealed that the MIC increment ratio was significantly correlated with the bulkiness of the C-7 substituent and bulkiness and hydrophobicity of the C-8 substituent of fluoroquinolones (r = 0.87) and not with its molecular hydrophobicity (r = 0.47). Cellular accumulation of norfloxacin in SA-1199B was significantly lower than that in SA-1199, and it was increased by addition of carbonyl cyanide m-chlorophenyl hydrazone. On the other hand, accumulations of CS-940 in these strains were nearly identical, and they were not affected by addition of the protonophore.
Structure-related inhibitory effect of antimicrobial enoxacin and derivatives on theophylline metabolism by rat liver microsomes
Authors: Mizuki Y , Fujiwara I , Yamaguchi T , Sekine Y
Published: October 2018

Enoxacin, an antimicrobial fluoroquinolone with a 7-piperazinyl-1, 8-naphthyridine skeleton, is a potent inhibitor of cytochrome P-450-mediated theophylline metabolism. The present study was designed to clarify, using seven enoxacin derivatives, the molecular characteristics of the fluoroquinolone responsible for the inhibition. Three derivatives with methyl-substituted 7-piperazine rings inhibited rat liver microsomal theophylline metabolism to 1,3-dimethyluric acid to an extent similar to that of enoxacin (50% inhibitory concentrations [IC50s] = 0.39 to 0.48 mM). 7-Piperazinyl-quinoline derivatives, 8-hydroenoxacin (8-Hy) and 1-cyclopropyl-8-fluoroenoxacin (8-F1), which have a hydrogen and a fluorine at position 8, respectively, more weakly inhibited metabolite formation (IC50s = 0.88 and 1.29 mM, respectively). Little inhibition (IC50 > 2 mM) was observed in those with 3'-carbonyl and 4'-N-acetyl groups on the piperazine rings. The substrate-induced difference spectra demonstrated that the affinities of enoxacin, 8-Hy, and 8-F1 to cytochrome P-450 were parallel with their inhibitory activities. The substituent at position 8 was found to determine the molecular conformations of the fluoroquinolones, and the planarity in molecular shape decreased in the same order as the inhibitory activity (enoxacin > 8-Hy > 8-F1). Moreover, the 3'-carbonyl and 4'-N-acetyl groups decreased the basicity of their vicinal 4'-nitrogen atoms when judged from their electrostatic potentials, which showed a remarkably broadened negative charge around the nitrogens. As a result, the planarity of the whole molecule and the basicity of the 4'-nitrogen atom of enoxacin are likely to be dominant factors in the inhibition of theophylline metabolism by cytochrome P-450.
Characterization of bactericidal activity of clindamycin against Bacteroides fragilis via kill curve methods
Authors: Klepser M E , Banevicius M A , Quintiliani R , Nightingale C H
Published: October 2018

Kill curves were determined for five isolates of Bacteroides fragilis with clindamycin at concentrations equal to the MIC or to 4, 16, and 64 times the MIC. Examination of plots of log CFU per milliliter versus time revealed no association between the clindamycin concentration and the rate and extent of the bactericidal activity against B. fragilis at or below 64 times the MIC.
Response to fluconazole by 23 patients with human immunodeficiency virus infection and oral candidiasis: pharmacological and mycological factors
Authors: Lacassin F , Damond F , Chochillon C , Longuet P , Lebras J , Vilde J L , Leport C
Published: October 2018

The MICs of fluconazole for strains of Candida species and the levels of fluconazole in serum were determined at day 0 and day 14 for 23 human immunodeficiency virus-infected patients with oral candidiasis who were treated orally with 100 mg of fluconazole per day for 14 days. Among the 23 patients, 11 (48%) were not clinically cured and had persistent isolation of Candidiasis albicans (n = 10) and/or presence of non-C. albicans (n = 6). Clinical response could be predicted by the susceptibility of the strain to fluconazole determined at day 0. All 12 patients who were cured were infected with a strain for which the MIC was < 0.78 mg/liter. All four patients who were infected with a strain for which the MIC was > 3.12 mg/liter experienced clinical failure. These data suggest that a C. albicans strain could be defined as being susceptible when the MIC of fluconazole is < 0.78 mg/liter and as being resistant when the MIC is > 3.12 mg/liter.
Potent anti-murine cytomegalovirus activity and reduced nephrotoxicity of ganciclovir cyclic phosphonate
Authors: Smee D F , Reist E J
Published: October 2018

Ganciclovir cyclic phosphonate (SR3775) is a derivative of the R enantiomer (SR3773) of ganciclovir phosphonate (9-[((+/-)-1-hydroxymethyl-3-phosphono)propyloxymethyl]guanine), both of which are potent inhibitors of human ctyomegalovirus and murine cytomegalovirus (MCMV). Against wild-type and four drug-resistant strains of MCMV, SR3773 was 2.3- to 3-fold more potent than SR3775. SR3775 was about half as active as SR3773 against MCMV infections in severe combined immunodeficient mice. However, whereas SR3773 caused 20 to 30% destruction of renal tubules at 50 mg/kg of body weight per day (but exerted no toxicity at 25 mg/kg/day), SR3775 showed no deleterious renal effects at 600 mg/kg/day over 14 days. SR3775 has a therapeutic index at least 12 times higher than SR3773 in mice, making it a candidate for the treatment of human cytomegalovirus disease.
In vitro and in vivo effects of rifabutin alone or combined with atovaquone against Toxoplasma gondii
Authors: Romand S , Della Bruna C , Farinotti R , Derouin F
Published: October 2018

The efficacy of rifabutin (RIFA) alone or in combination with atovaquone (ATO) was examined in vitro and in a murine model of acute toxoplasmosis. In vitro studies were performed with MRC5 fibroblast tissue cultures, with quantification of Toxoplasma growth by enzyme-linked immunosorbent assay. For in vivo studies, mice were acutely infected with 10(4) tachyzoites of the virulent RH strain and were then treated perorally for 10 days from day 1 or day 4 postinfection. The efficacy of each drug regimen was assessed by determination of survival rates and sequential titration of parasites in blood, brain, and lungs by a tissue culture method. In vitro, RIFA was inhibitory for Toxoplasma growth at concentrations between 0.5 and 20 micrograms/ml; the 50% inhibitory concentration was estimated to be 1.68 micrograms/ml. When RIFA and ATO were combined, synergistic effects were noted for RIFA at 20 micrograms/ml combined with ATO at 0.01 or 0.02 microgram/ml and RIFA at 1, 2, or 5 micrograms/ml combined with ATO at 0.02 microgram/ml. In vivo, administration of RIFA at 200 mg/kg of body weight per day from day 1 to day 10 resulted in a 100% protection during treatment, with clearance of parasites from the blood, brain, and lungs. After the cessation of therapy, relapses occurred in the brain and lungs; the mortality was 46% at the end of the experiment (day 30). Among the mice treated with RIFA at 200 mg/kg/day from day 4 to day 14, no death was recorded during the treatment period and a marked reduction in parasite burdens was observed in blood and tissues; however, relapses occurred and 10% of mice survived until day 30. Administration of RIFA at 200 mg/kg/day in combination with ATO at 100 mg/kg/day resulted in a marked prolongation of survival compared with that for mice that received ATO or RIFA alone. However, in mice receiving the combination, parasite burdens in blood and organs were similar to those in mice treated with RIFA alone. These results confirmed the activity of RIFA in the treatment of acute toxoplasmosis and the potential of the combination of RIFA-ATO since the two drugs act synergistically against Toxoplasma gondii.
Expression of the multidrug resistance operon mexA-mexB-oprM in Pseudomonas aeruginosa: mexR encodes a regulator of operon expression
Authors: Poole K , Tetro K , Zhao Q , Neshat S , Heinrichs D E , Bianco N
Published: October 2018

The region upstream of the multiple antibiotic resistance efflux operon mexA-mexB-oprM in Pseudomonas aeruginosa was sequenced, and a gene, mexR, was identified. The predicted MexR product contains 147 amino acids with a molecular mass of 16,964 Da, which is consistent with the observed size of the overexpressed mexR gene product. MexR was homologous to MarR, the repressor of MarA-dependent multidrug resistance in Escherichia coli, and other repressors of the MarR family. A mexR knockout mutant showed a twofold increase in expression of both plasmid-borne and chromosomal mexA-reporter gene fusions compared with the MexR+ parent strain, indicating that the mexR gene product negatively regulates expression of the mexA-mexB-oprM operon. Furthermore, the cloned mexR gene product reduced expression of a plasmid-borne mexA-lacZ fusion in E. coli, indicating that MexR represses mexA-mexB-oprM expression directly. Consistent with the increased expression of the efflux operon in the mexR mutant, the mutant showed an increase (relative to its MexR+ parent) in resistance to several antimicrobial agents. Expression of a mexR-lacZ fusion increased threefold in a mexR knockout mutant, indicating that mexR is negatively autoregulated. OCR1, a nalB multidrug-resistant mutant which overproduces OprM, exhibited a greater than sevenfold increase in expression of a chromosomal mexA-phoA fusion compared with its parent. Introduction of a mexR knockout mutation in strain OCR1 eliminated this increase in efflux gene expression and, as expected, increased the susceptibility of the strain to a variety of antibiotics. The nucleotide sequences of the mexR genes of OCR1 and its parental strain revealed a single base substitution in the former which would cause a predicted substitution of Trp for Arg at position 69 of its mexR product. These data suggest that MexR possesses both repressor and activator function in vivo, the activator form being favored in nalB multidrug-resistant strains.
A rob-like gene of Enterobacter cloacae affecting porin synthesis and susceptibility to multiple antibiotics
Authors: Lee E H , Collatz E , Podglajen I , Gutmann L
Published: October 2018

A chromosomal gene of Enterobacter cloacae affecting the synthesis of major outer membrane proteins in E. cloacae and Escherichia coli was cloned by using selection for resistance to cefoxitin in E. coli. The presence of the gene, when plasmid-borne, led to a decrease in the amount of porin F in E. cloacae and the amount of OmpF in E. coli and caused 2- to 32-fold increases in the MICs of chloramphenicol, tetracycline, quinolones, and beta-lactam antibiotics. The gene encoded a 33-kDa protein, similar (83% identity) to the protein Rob involved in the initiation of DNA replication in E. coli, which was called RobA(EC1) by analogy. RobA from E. cloacae was found to inhibit ompF expression at the posttranscriptional level via activation of micF, a gene also apparently present in E. cloacae, as detected by PCR. As with its homolog from E. coli, RobA(EC1) is related to the XylS-AraC class of positive transcriptional regulators, along with MarA and SoxS, which also cause a micF-mediated decrease in the level of ampF expression.
Pharmacokinetic interaction between itraconazole and rifampin in Yucatan miniature pigs
Authors: Kaltenbach G , Levêque D , Peter J D , Salmon J , Elkhaili H , Cavalier A , Salmon Y , Monteil H , Jehl F
Published: October 2018

The objective of this study was to examine the effects of rifampin on itraconazole pharmacokinetics, at steady state, in three Yucatan miniature pigs. Daily for 3 weeks, the pigs received 200 mg of itraconazole orally at the beginning of each meal, and for the following 2 weeks they received itraconazole orally combined with intravenous administration of rifampin at 10 mg/kg/day. Coadministration of rifampin resulted in an 18-fold decrease in the maximum concentration of itraconazole in serum, from 113.0 (standard deviation [SD] 17.2) to 6.2 (SD, 3.9) ng/ml and a 22-fold decrease in the area under the concentration-time curve, from 1,652.7 (SD, 297.7) to 75.6 (SD, 30.0) ng.h/ml. The active metabolite of itraconazole, hydroxyitraconazole, was undetectable. This study demonstrates that rifampin affects itraconazole kinetics considerably at steady state in this miniature-pig model, probably by inducing hepatic metabolism of itraconazole.
In vivo activity and pharmacodynamics of amoxicillin in combination with fosfomycin in fibrin clots infected with highly penicillin-resistant Streptococcus pneumoniae
Authors: Chavanet P , Peyrard N , Pechinot A , Buisson M , Duong M , Neuwirth C , Kazmierczak A , Portier H
Published: October 2018

Using a clinical pneumococcal strain for which MICs were 4, 2, and 32 mg/liter for penicillin, amoxicillin, and fosfomycin, respectively, we studied the efficacies of these antibiotics alone and their combinations in the treatment of prolonged (48-h) experimental fibrin clot infection in rabbits. Treatments were as follows: amoxicillin IV at 20 mg/kg of body weight in one dose (Amo20), 50 mg/kg in one dose (Amo50), or two doses 6 h apart (Amo20 x 2 and Amo50 x 2); fosfomycin IV at a fixed dose of 50 mg/kg in one dose (Fos50) or two divided doses 6 h apart (Fos50 x 2); or the combinations of amoxicillin and fosfomycin with the same schedules. Maximum concentrations in clots were 2.03 +/- 1.02 and 2.13 +/- 0.33 mg/liter for Amo20 regimens, 3.7 +/- 1.9 and 4 +/- 1.3 mg/liter for Amo50 regimens, and 24 +/- 7 and 40 +/- 8 mg/liter for fosfomycin regimens, respectively. The mean half-lives of elimination from clots were between 2 and 3 h for amoxicillin regimens and between 5 and 7 h for fosfomycin. We observed the highest bacterial reductions (log10 CFU/gram) for Amo50 in two divided doses with or without fosfomycin. A significantly higher bacterial reduction than that with each monotherapy was observed when Amo20 was combined with fosfomycin in either one dose or two doses 6 h apart (0.16 +/- 0.8 and 1.64 +/- 1.6 log10 CFU/g for Amo20 in one and two doses, respectively, and 0.93 +/- 0.81 and 0.61 +/- 0.56 log10 CFU/g for fosfomycin in one and two doses, respectively, versus 3.46 +/- 1.26 and 3.16 +/- 1.31 log10 CFU/g for Amo20 plus fosfomycin in one and two doses, respectively [P < 0.001]). A time-dependent effect was observed with amoxicillin regimens. The time of regrowth was significantly delayed when amoxicillin was combined with fosfomycin. By using a multivariate analysis, we demonstrated that the most important parameter correlated to efficacy of the combination amoxicillin-fosfomycin was the length of the period during which the concentration of amoxicillin remained above the MIC. We demonstrated that the in vivo efficacy of the combination of amoxicillin and fosfomycin gave higher antibacterial effect than each monotherapy.
Single-dose and steady-state pharmacokinetics of hypericin and pseudohypericin
Authors: Kerb R , Brockmöller J , Staffeldt B , Ploch M , Roots I
Published: October 2018

Single-dose and steady-state pharmacokinetics of antivirally acting hypericin (H) and pseudohypericin (PH) were studied in 13 healthy volunteers by administration of St. John's Wort extract LI 160, a plantal antidepressant. Oral administration of 250, 750, and 1,500 micrograms of H and 526, 1,578, and 3,156 micrograms of PH resulted in median peak levels in plasma (Cmax) of 1.3, 7.2, and 16.6 micrograms/liter for H and 3.4, 12.1, and 29.7 micrograms/liter for PH, respectively. The Cmax and the area under the curve values for the lowest dose were disproportionally lower than those for the higher doses. A lag time of 1.9 h for H was remarkably longer than the 0.4-h lag time for PH. Median half-lives for absorption, distribution, and elimination were 0.6, 6.0, and 43.1 h after 750 micrograms of H and 1.3, 1.4, and 24.8 h after 1,578 micrograms of PH, respectively. Fourteen-day treatment with 250 micrograms of H and 526 micrograms of PH three times a day resulted in median steady-state trough levels of 7.9 micrograms/liter for H and 4.8 micrograms/liter for PH after 7 and 4 days, respectively; the corresponding Cssmax levels were 8.8 and 8.5 micrograms/liter, respectively. Kinetic parameters after intravenous administration of Hypericum extract (115 and 38 micrograms for H and PH, respectively) in two subjects corresponded to those estimated after an oral dosage. Both H and PH were initially distributed into a central volume of 4.2 and 5.0 liter, respectively. The mean distribution volumes at steady state were 19.7 liters for H and 39.3 liters for PH, and the mean total clearance rates were 9.2 ml/min for H and 43.3 ml/min for PH. The systemic availability of H and PH from LI 160 was roughly estimated to be 14 and 21%, respectively. Treatment with Hypericum extract, even in high doses, was well tolerated.
Antimicrobial activity of human pancreatic juice and its interaction with antibiotics
Authors: Minelli E B , Benini A , Bassi C , Abbas H , Falconi M , Locatelli F , de Marco R , Pederzoli P
Published: October 2018

Pancreatic juice (PJ) should be a factor of variability in the antimicrobial activity of antibiotics eliminated by the pancreas during pancreatic infections. We studied its effects on the activity of antimicrobial drugs with different mechanisms of action. Samples of pure PJ were collected from 16 patients with stabilized external pancreatic fistulas. The antimicrobial activity of the juice at different concentrations (from 1.25 to 100%) alone and in combination with mezlocillin, imipenem, ceftriaxone, gentamicin, ofloxacin, and ciprofloxacin was studied by a microbiological method (continuous turbidimetric recording of bacterial growth). The human PJ showed dose-dependent antimicrobial activity that increased directly with the concentration. The activity of the antibiotics at bactericidal concentrations were not modified by the PJ, while the combination with subinhibitory concentrations produced the following variable and different effects: (i) additivity with mezlocillin, ceftriaxone, gentamicin, and ciprofloxacin and autonomy (no interaction) with imipenem and ofloxacin against Providencia rettgeri and (ii) additivity with ceftriaxone, ofloxacin, gentamicin, imipenem, and mezlocillin and autonomy with ciprofloxacin against Escherichia coli. In the presence of PJ, fluoroquinolones showed constant positive effects, while beta-lactams showed more variable antimicrobial activity. Antibiotic concentrations and PJ pharmacodynamics are the main factors determining the final effect of the interaction in vitro. These results may be useful in choosing antibiotics for the treatment of pancreatic infections when they are supplemented with the pharmacokinetic data for each drug.
Comparison study of broth macrodilution and microdilution antifungal susceptibility tests for the filamentous fungi
Authors: Pujol I , Guarro J , Llop C , Soler L , Fernández-Ballart J
Published: October 2018

An evaluation of broth dilution antifungal susceptibility tests was performed by determining both the micro- and macrodilution MICs of amphotericin B, fluconazole, ketoconazole, 5-fluorocytosine, miconazole, and itraconazole against representative species of opportunistic hyphomycetes (Fusarium spp. and Cladosporium [Cladophialophora] spp.) and ascomycetes (Chaetomium spp.). A total of 78 strains were tested, the majority of them twice and some three times on different days. Both methods were performed according to the recommendations of the National Committee for Clinical Laboratory Standards (Document M27-P), with the exception of the temperature of incubation, which was 25 degrees C in our case. A spectrophotometric method for inoculum preparation, RPMI 1640 medium buffered with morpholinepropanesulfonic acid (pH 7.0), and an additive drug dilution procedure were used. The MICs obtained by the two methods were read after 48, 72, and 96 h of incubation for Fusarium spp. and after 72, 96, and 120 h for the remaining isolates. The kappa test was used to calculate the degree of agreement. Considering the three fungal groups together, a good agreement between the results of both tests was observed with almost all the drugs at the different incubation times. There were no cases of poor agreement. The highest level (kappa index = 1) was observed with ketoconazole at the second-day reading. These results support the further evaluation of the broth microdilution test as an alternative to the reference broth macrodilution susceptibility test.
Recovery of active beta-lactamases from Proteus vulgaris and RTEM-1 hybrid by random mutagenesis by using a dnaQ strain of Escherichia coli
Authors: Hosseini-Mazinani S M , Nakajima E , Ihara Y , Kameyama K Z , Sugimoto K
Published: October 2018

Proteus vulgaris and RTEM-1 beta-lactamases that belong to molecular class A with 37% amino acid similarity were examined to find the relationship between amino acid residues and activity of enzymes. MICs of ampicillin were > 2,000 micrograms/ml for Escherichia coli cells producing these enzymes. We have made 18 hybrid genes by substituting the coding region of the P. vulgaris beta-lactamase gene with the equivalent portions from the RTEM-1 gene. Most of these hybrids produced inactive proteins, but a few hybrid enzymes had partial or trace activity. From one of the hybrid genes (MIC of ampicillin, 100 micrograms/ml), we recovered three kinds of active mutants which provided ampicillin MICs of 1,000 micrograms/ml by the selection of spontaneous mutations in a dnaQ strain of E. coli. In these mutants, Leu-148, Met-182, and Tyr-274 were replaced with Val, Thr, and His, respectively. These amino acids have not been identified as residues with functional roles in substrate hydrolysis. Furthermore, from these hybrid mutants, we obtained a second set of mutants which conferred ampicillin MICs of 1,500 micrograms/ml. Interestingly, the second mutations were limited to these three amino acid substitutions. These amino acid residues which do not directly interact with substrates have an effect on enzyme activity. These mutant enzymes exhibited lower K(m) values for cephaloridine than both parental enzymes.
Effect of fluconazole on fungicidal activity of flucytosine in murine cryptococcal meningitis
Authors: Larsen R A , Bauer M , Weiner J M , Diamond D M , Leal M E , Ding J C , Rinaldi M G , Graybill J R
Published: October 2018

Both animal and in vitro studies have demonstrated that combinations of flucytosine with amphotericin B and with fluconazole have significantly improved activity against cryptococcal meningitis compared with the activity of each drug used alone. However, very few dose levels of these agents have been tested in combination. This study evaluated the efficacy of fluconazole plus flucytosine in a murine model of cryptococcal meningitis over a broad range of dose combinations (fluconazole, 0 to 40 micrograms/g of body weight per day; flucytosine, 0 to 200 micrograms/g/day). Both drugs were dissolved in drinking water, with treatment on days 2 to 11. In this highly reproducible model, fluconazole had a dramatic effect on the fungicidal activity of flucytosine. Flucytosine at dose levels of as much as 200 micrograms/g/day alone or in combination with low doses of fluconazole had minimal fungicidal activity, whereas in combination with fluconazole at 24 to 40 micrograms/g/day, flucytosine showed fungicidal activity in the range of 45 to 65% of the animals treated at doses of 40 to 100 micrograms/g/day. This striking effect of fluconazole is consistent with the results of both in vitro and clinical studies. In the clinic, the use of flucytosine is often limited by severe toxicity, while toxicity is rarely observed with fluconazole. These results suggest that when flucytosine is given with higher doses of fluconazole, the maximum therapeutic effect of the former in the clinic may be observed at dose levels that are far less than the doses commonly employed (150 micrograms/g daily).
Evidence that high-dosage zidovudine at time of retrovirus exposure reduces antiviral efficacy
Authors: Mathes L E , Hayes K A , Kociba G
Published: October 2018

The antiviral efficacy of prophylactic 3'-azido-3'-deoxythymidine (AZT) therapy administered by continuous infusion or intermittent injection was compared in pediatric cats infected with feline leukemia virus. A 4-week treatment regimen of AZT was initiated at -48, 8, or 96 h postinfection (p.i.). For AZT therapy begun at -48 h p.i., significant efficacy was attained when therapy was given by continuous infusion but not by intermittent injection. However, when AZT therapy was delayed until 96 h p.i., both continuous infusion and intermittent injection gave complete protection. The results suggest that intermittent AZT administration is less efficacious than continuous infusion. Higher peak AZT concentrations in plasma associated with intermittent injection compared with those associated with continuous infusion may be immunotoxic, thus reducing the drug-induced vaccine effect. Furthermore, AZT toxicity seemed to be restricted to a window of sensitivity close to the time of virus challenge because delaying the start of AZT therapy until 96 h p.i. was highly efficacious, regardless of the method of administration.
Systemic availability of itraconazole in lung transplantation
Authors: Patterson T F , Peters J , Levine S M , Anzueto A , Bryan C L , Sako E Y , Miller O L , Calhoon J H , Rinaldi M G
Published: October 2018

Systemic availability of itraconazole in lung transplantation was evaluated by serially measuring the bioactivity of itraconazole in lung transplant patients who received itraconazole for prophylaxis (n = 12) or therapy (n = 5). These patients also received concomitant antacid and H2 blocker therapy. In patients receiving itraconazole at 200 and 400 mg/day, the median concentrations in serum were 0.5 microgram/ml (range, < 0.05 to 2.7) and 3.5 micrograms/ml (< 0.5 to 14), respectively. The concentration following administration of 400 mg/day was > 2.5 micrograms/ml in 56% of samples, while only 4% of samples from patients who were administered 200 mg/day had levels over 2.5 micrograms/ml. This study documents that itraconazole can be absorbed in patients receiving concomitant antacid and H2 blocker therapy. However, the reduced and variable absorption suggests the importance of confirming drug delivery by measurement of concentrations in serum.
Effects of cyclophosphamide and ceftriaxone on gastrointestinal colonization of mice by Candida albicans
Authors: Samonis G , Karyotakis N C , Anaissie E J , Barbounakis E , Maraki S , Tselentis Y , Bodey G P
Published: October 2018

Adult male Crl:CD1 (ICR) mice were fed chow containing Candida albicans to induce sustained gastrointestinal colonization by the yeast. Groups of mice were rendered neutropenic with cyclophosphamide and subsequently received ceftriaxone, while other groups received normal saline and served as controls. Stool cultures were obtained immediately before and at the end of treatment. The administration of cyclophosphamide substantially increased the C. albicans counts in the stools of mice. The addition of ceftriaxone to the cyclophosphamide regimen did not significantly increase the level of gastrointestinal colonization by C. albicans. There was no evidence of Candida dissemination to internal organs.
Glycylcyclines bind to the high-affinity tetracycline ribosomal binding site and evade Tet(M)- and Tet(O)-mediated ribosomal protection
Authors: Bergeron J , Ammirati M , Danley D , James L , Norcia M , Retsema J , Strick C A , Su W G , Sutcliffe J , Wondrack L
Published: October 2018

N,N-dimethylglycylamido (DMG) derivatives of 6-demethyl-6-deoxytetracycline and doxycycline bind 5-fold more effectively than tetracycline to the tetracycline high-affinity binding site on the Escherichia coli 70S ribosome, which correlates with a 10-fold increase in potency for inhibition of E. coli cell-free translation. The potencies of DMG-doxycycline and DMG-6-demethyl-6-deoxytetracycline were unaffected by the ribosomal tetracycline resistance factors Tet(M) and Tet(O) in cell-free translation assays and whole-cell bioassays with a conditional Tet(M)-producing E. coli strain.
In vitro activity of BMS-181184 compared with those of fluconazole and amphotericin B against various candida spp
Authors: Wardle H M , Law D , Denning D W
Published: October 2018

We compared the in vitro activity of BMS-181184, the first compound of a new class of antifungal agents, the pradimicins, with those of fluconazole and amphotericin B against 64 clinical isolates of Candida species. MICs were determined by a microdilution method with high resolution medium for BMS-181184 and fluconazole and antibiotic medium no. 3 with 2% glucose for amphotericin B. MICs of BMS-181184 for all yeasts were in the range of 0.78 to 12.5 micrograms/ml. BMS-181184 was active against isolates resistant to other antifungal agents, consistent with a novel mode of action. Minimum fungicidal concentrations for 16 isolates showed that BMS-181184 was fungicidal. Clinical studies are now required to confirm its activity.
Evaluation of a brain-targeting zidovudine chemical delivery system in dogs
Authors: Brewster M E , Anderson W R , Webb A I , Pablo L M , Meinsma D , Moreno D , Derendorf H , Bodor N , Pop E
Published: October 2018

AIDS encephalopathy is an insidious complication of human immunodeficiency virus infection which is difficult to treat because of the poor uptake of many potentially useful antiretroviral drugs through the blood-brain barrier. A chemical delivery system (CDS) for zidovudine (AZT) based on redox trapping within the brain has been prepared and tested in several animal models to circumvent this limitation. The behavior of the AZT-CDS in the dog was considered. Parenteral administration of AZT resulted in rapid systemic elimination and poor uptake by the central nervous system. Ratios of the area under the concentration-time curve of AZT for cerebrospinal fluid to that for blood were 0.32, and ratios of the area under the concentration-time curve of AZT for brain to that for blood were approximately 0.25. Administration of an aqueous formulation of the AZT-CDS resulted in rapid tissue uptake and conversion of the CDS to the corresponding quaternary salt with the subsequent production of AZT. Delivered in this way, the levels of AZT in brain were 1.75- to 3.3-fold higher than those associated with conventional AZT administration. In addition, the levels of AZT in blood were 46% lower than those associated with AZT administration. The higher concentrations in brain and lower concentration in blood combined to significantly increase the ratio of the concentration of AZT in the brain to that in blood after AZT-CDS administration compared to that after AZT dosing.
Prednisolone at anti-inflammatory or immunosuppressive dosages in conjunction with doxycycline does not potentiate the severity of Rickettsia rickettsii infection in dogs
Authors: Breitschwerdt E B , Davidson M G , Hegarty B C , Papich M G , Grindem C B
Published: October 2018

Dogs were experimentally inoculated with Rickettsia rickettsii to determine if anti-inflammatory or immunosuppressive dosages of prednisolone, when administered in conjunction with an antirickettsial antibiotic (doxycycline), induced therapeutically relevant pathophysiological consequences that ultimately influence disease outcome. Although the duration of rickettsemia was prolonged in dogs receiving immunosuppressive, but not anti-inflammatory, corticosteroids, concurrent administration of doxycycline and corticosteroids conferred no other detected detrimental effects. Treatment with doxycycline or doxycycline in conjunction with prednisolone resulted in decreased R. rickettsii-specific antibody titers; however, examination of appropriately timed acute- and convalescent-phase serum samples would have facilitated an accurate diagnosis of Rocky Mountain spotted fever (RMSF) in all 16 dogs. We conclude that the concurrent use of anti-inflammatory or immunosuppressive doses of prednisolone in conjunction with doxycycline, early in the course of experimental RMSF, confers no clinically relevant detrimental effects and that additional studies might be indicated to detect possible beneficial effects in cases of severe or potentially fulminant RMSF. However, because the illness induced in these dogs was of mild to moderate severity, the results of this study should definitely not be construed as supporting the safety or efficacy of prednisolone for treatment of severe canine or human RMSF.
MIC and time-kill studies of antipneumococcal activity of GV 118819X (sanfetrinem) compared with those of other agents
Authors: Spangler S K , Jacobs M R , Appelbaum P C
Published: October 2018

Agar dilution MIC methodology was used to test the activities of GV 118819X (sanfetrinem), ampicillin, amoxicillin, amoxicillin-clavulanate, cefpodoxime, loracarbef, levofloxacin, clarithromycin, ceftriaxone, imipenem, and vancomycin against 53 penicillin-susceptible, 84 penicillin-intermediate and 74 penicillin-resistant pneumococci isolated in the United States. GV 118819X was the most active oral beta-lactam, with MIC at which 50% of the isolates were inhibited (MIC50)/MIC90 values of 0.008/0.03, 0.06/0.5, and 0.5/1.0 micrograms/ml against penicillin-susceptible, -intermediate, and -resistant stains, respectively. Amoxicillin and amoxicillin in the presence of clavulanate (2:1) were the second most-active oral beta-lactams, followed by ampicillin and cefpodoxime; loracarbef was not active against penicillin-intermediate and -resistant strains. Clarithromycin was most active against penicillin-susceptible strains but was less active against intermediate and resistant stains. All pneumococcal stains were inhibited by ceftriaxone and imipenem at MICs of < or = 4.0 and < or = 1.0 micrograms/ml, respectively. The activities of levofloxacin and vancomycin were unaffected by penicillin susceptibility. Time-kill studies of three penicillin-susceptible, three penicillin-intermediate, and three penicillin-resistant pneumococci showed that all compounds, at the broth microdilution MIC, yielded 99.9% killing of all strains after 24 h. Kinetic patterns of all oral beta-lactams, ceftriaxone, and vancomycin were similar relative to the MIC, with 90% killing of all strains first observed after 12 h. However, killing by amoxicillin-clavulanate, imipenem, and levofloxacin was slightly faster and that by clarithromycin was slower than that by the above-described drugs. At 2 x the MIC, more strains were killed earlier than was the case at the MIC, but the pattern seen at the MIC prevailed. When MICs and kill kinetics were combined, sanfetrinem was the most active oral antipneumococcal agent in this study.
The immunosuppressant FK506 and its nonimmunosuppressive analog L-685,818 are toxic to Cryptococcus neoformans by inhibition of a common target protein
Authors: Odom A , Del Poeta M , Perfect J , Heitman J
Published: October 2018

The immunosuppressant FK506 (tacrolimus) is an antifungal natural product macrolide that suppresses the immune system by blocking T-cell activation. In complex with the intracellular protein FKBP12, FK506 inhibits calcineurin, a Ca(2+)-calmodulin-dependent serine-threonine protein phosphatase. We recently reported that growth of the opportunistic fungal pathogen Cryptococcus neoformans is resistant to FK506 at 24 degrees C but sensitive at 37 degrees C and that calcineurin, the target of FKBP12-FK506, is required for growth at 37 degrees C in vitro and pathogenicity in vivo. These findings identify calcineurin as a potential antifungal drug target. In previous studies the calcineurin inhibitor cyclosporin A (CsA) was effective against murine pulmonary infections but exacerbated cryptococcal meningitis in rabbits and mice, likely because CsA does not cross the blood-brain barrier. Although we find that FK506 penetrates the CNS, FK506 also exacerbates cryptococcal meningitis in rabbits. Thus, FK506 immunosuppression outweighs antifungal action in vivo. Like FK506, the nonimmunosuppressive FK506 analog L-685,818 is toxic to C. neoformans in vitro at 37 degrees C but not at 24 degrees C, and FK506-resistant mutants are resistant to L-685,818, indicating a similar mechanism of action. Fluconazole-resistant C. neoformans clinical isolates were also found to be susceptible to both FK506 and L-685,818. Our findings identify calcineurin as a novel antifungal drug target and suggest the nonimmunosuppressive FK506 analog L-685,818 or other congeners warrant further consideration as antifungal drugs for C. neoformans.
Effects of steroidal allenic phosphonic acid derivatives on the parasitic protists Leishmania donovani, Leishmania mexicana mexicana, and Pneumocystis carinii carinii
Authors: Beach D H , Chen F , Cushion M T , Macomber R S , Krudy G A , Wyder M A , Kaneshiro E S
Published: October 2018

Several pathogenic fungi and protozoa are known to have sterols distinct from those of their mammalian hosts. Of particular interest as targets for drug development are the biosyntheses of the sterols of important parasites such as the kinetoplastid flagellates and the AIDS-associated opportunistic protist Pneumocystis carinii. These pathogens synthesize sterols with an alkyl group at C-24, and some have a double bond at C-22 of the side chain. Humans and other mammalian hosts are incapable of C-24 alkylation and C-22 desaturation. In the present study, three steroidal compounds with side chains substituted by phosphonyl-linked groups were synthesized and tested for their effects on Leishmania donovani and L. mexicana mexicana culture growth. The compounds inhibited organism proliferation at concentrations in micrograms per milliliter. The most potent inhibitors of this group of compounds were characterized by two ethyl groups at the phosphate function. Leishmania organisms treated with 17-[2-(diethylphosphonato) ethylidienyl]3-methoxy-19-norpregna-1,3,5-triene exhibited reduced growth after transfer into inhibitor-free medium. Because there are currently no axenic methods available for the continuous subcultivation of P. carinii, the effects of these drugs on this organism were evaluated by two alternative screening methods. The same two diethyl phosphonosteroid compounds that inhibited Leishmania proliferation were also the most active against P. carinii as determined by the potent effect they had on reducing cellular ATP content. Cystic as well as trophic forms responded to the drug treatments, as evaluated by a dual fluorescent staining live-dead assay. Other modifications of steroidal phosphonates may lead to the development of related drugs with increased activity and specificity for the pathogens.