bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloning and nucleotide sequence of the gyrA gene from Campylobacter fetus subsp. fetus ATCC 27374 and characterization of ciprofloxacin-resistant laboratory and clinical isolates
Authors: Taylor D E , Chau A S
Published: October 2018

The gyrA gene of Campylobacter fetus subsp. fetus, which encodes the A subunit of DNA gyrase, was cloned, and its nucleotide sequence was determined. An open reading frame of 2,586 nucleotides which encodes a polypeptide of 862 amino acids with an Mr of 96,782 was identified. C. fetus subsp. fetus GyrA is most closely related to Campylobacter jejuni GyrA, with 73% homology at the nucleotide level and 78% identity between polypeptides. The next most closely related GyrA was that from Helicobacter pylori, with both DNA homology and amino acid identity of 63%. The gyrA and gyrB (DNA gyrase B subunit) genes were located on the genomic map of C. fetus subsp. fetus ATCC 27374 and shown to be separate. A clinical isolate of C. fetus subsp. fetus and a laboratory-derived mutant of ATCC 27374, both resistant to ciprofloxacin, had identical mutations within the quinolone resistance determining region. In both mutants a G-->T transversion, corresponding to a substitution of Asp-91 to Tyr in GyrA, was linked to ciprofloxacin resistance, giving MICs of 8 to 16 micrograms/ml.
Fungicidal action of aureobasidin A, a cyclic depsipeptide antifungal antibiotic, against Saccharomyces cerevisiae
Authors: Endo M , Takesako K , Kato I , Yamaguchi H
Published: October 2018

Aureobasidin A, an antifungal antibiotic inhibiting a wide range of pathogenic fungi, is lethal for growing cells of susceptible fungi. We did cytological studies on the mechanism of its fungicidal action against Saccharomyces cerevisiae. When cultures were treated with 5.0 micrograms of aureobasidin A per ml, the numbers of viable cells started to decrease after 2 to 3 h of incubation, and most cells had lost viability after 5 to 6 h. When cell death in the treated cultures began, amino acids released by the cells could be detected, indicating disruption of the cell membrane. The proportion of cells with a single small bud or two or more buds increased as the population of viable cells decreased. Most such cells had the DNA content of cells in the G2 phase of the cell cycle, suggesting that the drug inhibited some cellular process involved in normal bud growth but did not affect DNA replication. Disruption of actin assembly was found in many cells treated for 2 to 3 h, as was chitin delocalization. The results suggest that aureobasidin A has a previously unknown mechanism of fungicidal action toward S. cerevisiae. It causes aberrant actin assembly, inhibiting the normal budding process and leading to cell death, probably through destruction of membrane integrity.
In vitro susceptibilities of clinical yeast isolates to a new echinocandin derivative, LY303366, and other antifungal agents
Authors: Pfaller M A , Messer S A , Coffman S
Published: October 2018

LY303366 is a new semisynthetic echinocandin derivative with potent, broad-spectrum fungicidal activity. We investigated the in vitro activity of LY303366, amphotericin B, flucytosine (5FC), fluconazole, and itraconazole against 435 clinical yeast isolates (413 Candida and 22 Saccharomyces cerevisiae isolates) obtained from over 30 different medical centers. MICs for all five antifungal agents were determined by the National Committee for Clinical Laboratory Standards method with RPMI 1640 test medium. LY303366 was also tested in antibiotic medium 3 as specified by the manufacturer. Overall, LY303366 was quite active against all of the yeast isolates when tested in RPMI 1640 (MIC at which 90% of the isolates are inhibited [MIC90], 1.0 microg/ml) but appeared to be considerably more potent when tested in antibiotic medium 3 (MIC90, 0.03 microg/ml). When tested in antibiotic medium 3, LY303366 was 16- to >2,000-fold more active than itraconazole, fluconazole, amphotericin B, or 5FC against all species except Candida parapsilosis. When tested in RPMI 1640, LY303366 was comparable to amphotericin B and itraconazole and more active than fluconazole and 5FC. All of the isolates for which fluconazole and itraconazole had elevated MICs (> or = 128 and > or = 2.0 microg/ml, respectively) were inhibited by < or = 0.007 microg of LY303366/ml when tested in antibiotic medium 3 and < or = 0.5 microg/ml when tested in RPMI 1640. Based on these studies, LY303366 has promising antifungal activity and warrants further in vitro and in vivo investigation.
Bactericidal activity of DU-6859a compared to activities of three quinolones, three beta-lactams, clindamycin, and metronidazole against anaerobes as determined by time-kill methodology
Authors: Spangler S K , Jacobs M R , Appelbaum P C
Published: October 2018

The activities of DU-6859a, ciprofloxacin, levofloxacin, sparfloxacin, piperacillin, piperacillin-tazobactam, imipenem, clindamycin, and metronidazole against 11 anaerobes were tested by the broth microdilution and time-kill methods. DU-6859a was the most active drug tested (broth microdilution MICs, 0.06 to 0.5 microg/ml), followed by imipenem (MICs, 0.002 to 4.0 microg/ml). Broth macrodilution MICs were within 3 (but usually 1) dilutions of the broth microdilution MICs. All compounds were bactericidal at the MIC after 48 h; after 24 h, 90% killing was shown for all strains when the compounds were used at four times the MIC. DU-6859a at < or = 0.5 microg/ml was bactericidal after 48 h.
Combination of mutations in human immunodeficiency virus type 1 reverse transcriptase required for resistance to the carbocyclic nucleoside 1592U89
Authors: Tisdale M , Alnadaf T , Cousens D
Published: October 2018

The carbocyclic nucleoside 1592U89 is a selective inhibitor of the human immunodeficiency virus (HIV), targeting the reverse transcriptase (RT). In vitro selection studies were undertaken to generate resistant variants with both HIV type 1 (HIV-1) wild-type strain HIV-1(HXB2) and 3'-azido-3'-deoxythymidine (AZT)-resistant strain HIV-1(RTMC). At least two or three mutations in RT were required to produce a 10-fold reduction in susceptibility. The first RT mutation selected was at codon 184, methionine (M) to valine (V), for HIV-1(HXB2) and HIV-1(RTMC), conferring two- and fivefold resistance, respectively. Two additional mutations were selected with HIV-1(HXB2), either leucine (L) 74 to V and lysine (K) 65 to arginine (R) (first-passage series) or L74 to V and tyrosine (Y) 115 to phenylalanine (F) (second-passage series). Cloned variants, obtained from the 1592U89 selection, were either double RT mutants 65R/184V and 74V/184V or triple RT mutant 74V/115Y/184V. Molecular clones were constructed with single, double, and triple combinations of these mutations for resistance analysis with different RT inhibitors. Each individual mutation conferred only low-level resistance (two- to fourfold) to 1592U89 in the HXB2 background. Double mutants containing the 184V mutation and triple mutants showed slightly greater levels of resistance to 1592U89 (7- to 11-fold). Some of the 1592U89-resistant variants were cross-resistant with 2',3'-dideoxycytidine, 2',3'-dideoxyinosine, and (-)-2'-deoxy-3'-thiacytidine, but none were resistant to 2',3'-didehydro-3'-deoxythymidine or AZT.
Clinical resistance to erythromycin and clindamycin in cutaneous propionibacteria isolated from acne patients is associated with mutations in 23S rRNA
Authors: Ross J I , Eady E A , Cove J H , Jones C E , Ratyal A H , Miller Y W , Vyakrnam S , Cunliffe W J
Published: October 2018

The genetic basis of erythromycin resistance in cutaneous propionibacteria was determined by comparing the nucleotide sequences of the peptidyl transferase region in the 23S rRNAs from 9 susceptible and 26 resistant clinical isolates as well as 4 laboratory-selected erythromycin-resistant mutants of a susceptible strain. In 13 isolates and the 4 laboratory mutants, cross-resistance to macrolides, lincosamides, and B-type streptogramins was associated with an A-->G transition at a position cognate with Escherichia coli 23S rRNA base 2058. These strains were resistant to > or = 512 microg of erythromycin per ml. Two other mutations were identified, an A-->G transition at base 2059 in seven strains, associated with high-level resistance to all macrolides, and a G-->A transition at base 2057 in six strains, associated with low-level resistance to erythromycin. These mutations correspond to three of four phenotypic classes previously identified by using MIC determinations.
Metabolism of rifabutin and its 25-desacetyl metabolite, LM565, by human liver microsomes and recombinant human cytochrome P-450 3A4: relevance to clinical interaction with fluconazole
Authors: Trapnell C B , Jamis-Dow C , Klecker R W , Collins J M
Published: October 2018

Rifabutin and fluconazole are often given concomitantly as therapy to prevent opportunistic infections in individuals infected with the human immunodeficiency virus. Recent reports have shown increased levels of rifabutin and its 25-desacetyl metabolite, LM565, in plasma when rifabutin is administered with fluconazole. Since fluconazole is known to inhibit microsomal enzymes, this study was undertaken to determine if this rifabutin-fluconazole interaction was due to an inhibition of human hepatic enzymes. The metabolism of both rifabutin and LM565 was evaluated in human liver microsomes and recombinant human cytochrome P-450 (CYP) 3A4 in the presence of fluconazole and other probe drugs known to inhibit CYP groups 1A2, 2C9, 2D6, 2E1, and 3A. The concentrations of rifabutin (1 microg/ml), LM565 (1 microg/ml), and fluconazole (10 and 100 microg/ml) used were equal to those observed in plasma after the administration of rifabutin and fluconazole at clinically relevant doses. High-performance liquid chromatography was used to assess the metabolism of rifabutin and LM565. Rifabutin was readily metabolized to LM565 by human microsomes, but the reaction was independent of NADPH and was not affected by the P-450 inhibitors. No rifabutin metabolism by recombinant CYP 3A4 was found to occur. LM565 was also metabolized by human microsomes to two products, but metabolism was dependent on NADPH and was affected by certain P-450 inhibitors. In addition, LM565 was readily metabolized by the recombinant CYP 3A4 to the same two products found with its metabolism by human microsomes. Therefore, rifabutin is metabolized by human microsomes but not via cytochrome P-450 enzymes, whereas LM565 is metabolized by CYP 3A4.
Topotecan inhibits human immunodeficiency virus type 1 infection through a topoisomerase-independent mechanism in a cell line with altered topoisomerase I
Authors: Zhang J L , Sharma P L , Li C J , Dezube B J , Pardee A B , Crumpacker C S
Published: October 2018

Topotecan (TPT), a known inhibitor of topoisomerase I, has previously been shown to inhibit the replication of several viruses. The mechanism of inhibition was proposed to be the inhibition of topoisomerase I. We report that TPT decreased replication of human immunodeficiency virus type 1 (HIV-1) in CPT-K5, a cell line with a topoisomerase I mutation. TPT inhibited production of HIV-1 RNA and p24 in CPT-K5 and wild-type cells equally effectively. The antiviral effects of TPT were observed not only in the topoisomerase-mutated CPT-K5 line but also in peripheral blood mononuclear cells (PBMC) acutely infected with clinical isolates and in OM10.1 cells latently infected with HIV and activated by tumor necrosis factor alpha. Little toxicity from TPT was noted in HIV-1-infected PBMC and in CPT-K5 and OM10.1 cells as measured by cell growth and proliferation assays. These observations suggest that TPT targets factors in virus replication other than cellular topoisomerase I and inhibits cytokine-mediated activation in latently infected cells by means other than cytotoxicity. These results suggest a potential for TPT and for other camptothecins in anti-HIV therapy alone and in combination with other antiretroviral drugs.
Pharmacokinetics of liposomal amphotericin B (Ambisome) in critically ill patients
Authors: Heinemann V , Bosse D , Jehn U , Kähny B , Wachholz K , Debus A , Scholz P , Kolb H J , Wilmanns W
Published: October 2018

The liposomal formulation of amphotericin B (AmBisome) greatly reduces the acute and chronic side effects of the parent drug. The present study describes the pharmacokinetic characteristics of AmBisome applied to 10 patients at a dose of 2.8 to 3.0 mg/kg of body weight and compares them to the pharmacokinetics observed in 6 patients treated with amphotericin B deoxycholate at the standard dose of 1.0 mg/kg. Interpatient variabilities of amphotericin B peak concentrations (Cmax) and areas under concentration-time curves (AUC) were 8- to 10-fold greater for patients treated with AmBisome than for patients treated with amphotericin B deoxycholate. At the threefold greater dose of AmBisome, median Cmaxs were 8.4-fold higher (14.4 versus 1.7 microg/ml) and median AUCs exceeded those observed with amphotericin B deoxycholate by 9-fold. This was in part explained by a 5.7-fold lower volume of distribution (0.42 liters/kg) in AmBisome-treated patients. The elimination of amphotericin B from serum was biphasic for both formulations. However, the apparent half-life of elimination was twofold shorter for AmBisome (P = 0.03). Neither hemodialysis nor hemofiltration had a significant impact on AmBisome pharmacokinetics as analyzed in one patient. In conclusion, the liposomal formulation of amphotericin B significantly (P = 0.001) reduces the volume of drug distribution, thereby allowing for greater drug concentrations in serum. The low toxicity of AmBisome therefore cannot readily be explained by its serum pharmacokinetics.
Antimicrobial susceptibility of flavobacteria as determined by agar dilution and disk diffusion methods
Authors: Chang J C , Hsueh P R , Wu J J , Ho S W , Hsieh W C , Luh K T
Published: October 2018

A total of 106 clinical isolates of flavobacteria, including 41 isolates of Flavobacterium meningosepticum, 59 of Flavobacterium indologenes, and 6 of Flavobacterium odoratum were collected from January 1992 to December 1995 from patients in Taiwan. The in vitro activities of antimicrobial agents were determined concomitantly by the standard agar dilution and disk diffusion methods. More than 90% of the flavobacterial isolates were resistant to cephalothin, cefotaxime, ceftriaxone, moxalactam, aztreonam, imipenem, aminoglycosides, erythromycin, and glycopeptides. The majority of F. meningosepticum isolates were susceptible to piperacillin and to minocycline but resistant to ceftazidime, with MICs at which 90% of the isolates are inhibited being 8, 4, and > 128 microg/ml, respectively. Approximately half of the F. indologenes isolates were susceptible to piperacillin, cefoperazone, ceftazidime, and minocycline, with MICs at which 50% of the isolates are inhibited being 4, 16, 8, and 4 microg/ml, respectively. The majority of F. odoratum isolates were resistant to all the antimicrobial agents tested except minocycline, to which five of six isolates were susceptible. With least-squares regression analysis and error rate-bounded analysis methods, the following resistant and susceptible zone diameter breakpoints were established: < or = 12 and > or = 17 mm, respectively, for piperacillin against F. meningosepticum and F. indologenes; < or = 13 and > or = 18 mm, respectively, for ceftazidime against F. meningosepticum and F. indologenes, < or = 17 and > or = 21 mm, respectively, for ofloxacin against F. indologenes; < or = 16 and > or = 20 mm, respectively, for ciprofloxacin against F. meningosepticum. Valid breakpoints for the disk diffusion method could not be established for cefoperazone and ofloxacin against F. meningosepticum and for minocycline against F. meningosepticum and F. indologenes due to a poor correlation coefficient for the regression line or for cefoperazone and ciprofloxacin against F. indologenes due to the presence of remarkable error rates.
Pharmacodynamic evaluation of a new glycopeptide, LY333328, and in vitro activity against Staphylococcus aureus and Enterococcus faecium
Authors: Mercier R C , Houlihan H H , Rybak M J
Published: October 2018

The objectives of the present study were to compare the in vitro activity of LY333328 (LY) to that of vancomycin (V) alone and in combination with gentamicin (G) and rifampin (R) against methicillin-resistant Staphylococcus aureus (MRSA) and V-resistant Enterococcus faecium (VREF), by using the killing curve methods. In addition, the effect of the inoculum size and protein on LY's activity was evaluated by using MICs and killing curves. MICs, MBCs, and killing curves were determined with supplemented Mueller-Hinton broth (B), B with albumin (4 g/dl) (A), and B with 50% pooled human serum (S). For MRSA, time to 99.9% killing after exposure to LY at four times the MIC (4x MIC) was achieved at 0.5 +/- 0 h (mean +/- standard deviation) and was significantly faster than that by V (8.54 +/- 0.10 h; P = 0.001). Against VREF, LY decreased the inoculum by 2.2 log10 CFU/ml at 24 h (P = 0.002). With a large inoculum of MRSA, the activity of LY and V at 4x MIC was decreased compared to that with the standard inoculum (P = 0.0003) and regrowth occurred at 24 h. The reduction in the number of CFU per milliliter at 24 h to 2 log10 CFU/ml was restored by increasing the LY concentration to at least 16x MIC. At 24 h, the combinations of LY and G, LY and R, LY and V, and V and G were better than either LY or V alone against a large inoculum of MRSA (P = 0.0002). LY and G achieved 99.9% killing at 1.01 +/- 0.03 h and was more rapid (P < 0.007) than all the other regimens studied except for V and G, which achieved 99.9% killing at 3.59 +/- 0.01 h. Killing curves determined with different media against a standard inoculum of MRSA did not demonstrate a significant difference between LY and V at 24 h. Time to 99.9% killing was more rapid with LY than with V in B, A, and S (P = 0.0002). Times to 99.9% killing by LY in B, A, and S were not significantly different from each other. Against VREF, LY killed better than V in B, A, or S at 24 h (P = 0.0002). LY in B was more active than LY in A or S (P = 0.0002). LY is a new potent glycopeptide with a unique activity profile. It has a greater activity than that of V against MRSA and has activity against VREF. LY demonstrated synergism in combination with gentamicin against MRSA. LY was affected by large inoculum sizes and proteins in time-kill studies. However, the effect was compensated for by increasing the drug concentration to 16x MIC.
In vitro induction of human immunodeficiency virus type 1 variants resistant to 2'-beta-Fluoro-2',3'-dideoxyadenosine
Authors: Tanaka M , Srinivas R V , Ueno T , Kavlick M F , Hui F K , Fridland A , Driscoll J S , Mitsuya H
Published: October 2018

2'-beta-Fluoro-2',3'-dideoxyadenosine (F-ddA) is an acid-stable purine dideoxynucleoside analog active against a wide spectrum of human immunodeficiency virus type 1 (HIV-1) and HIV-2 strains in vitro. F-ddA is presently undergoing a phase I clinical trial at the National Cancer Institute. We induced HIV-1 variants resistant to F-ddA by exposing wild-type HIV-1 (HIV-1LAI) to increasing concentrations of F-ddA in vitro. After 18 passages, the virus was fourfold less sensitive to F-ddA than HIV-1LAI. Sequence analyses of the passage 18 virus revealed changes in three amino acids in the reverse transcriptase (RT)-encoding region of the pol gene: P to S at codon 119 (P119S; present in 3 of 13 and 28 of 28 molecular clones before and after F-ddA exposure, respectively), V179D (0 of 13 and 9 of 28, respectively), and L214F (9 of 13 and 28 of 28, respectively). Drug sensitivity assays using recombinant infectious clones confirmed that P119S was directly responsible for the reduced sensitivity of HIV-1 to F-ddA. Various infectious clones with single or multiple amino acid substitutions conferring viral resistance against nucleoside RT inhibitors, including HIV-1 variants with multi-dideoxynucleoside resistance, were generally sensitive to F-ddA. The moderate level of resistance of HIV-1 to F-ddA, together with the lack of conferment of significant cross-resistance by the F-ddA-associated amino acid substitutions, warrants further investigation of F-ddA as a potential antiviral agent for use in treatment of HIV-1 infection.
In vitro and in vivo activities of AM-1155, a new fluoroquinolone, against Chlamydia spp
Authors: Miyashita N , Niki Y , Kishimoto T , Nakajima M , Matsushima T
Published: October 2018

The in vitro and in vivo activities of AM-1155, a new quinolone, against Chlamydia spp. were investigated. The MIC of AM-1155 for 10 standard strains of different Chlamydia spp. and 25 wild-type strains of Chlamydia pneumoniae isolated in Japan, which were morphologically different from clinical isolates from the United States, ranged from 0.063 to 0.125 microg/ml. Its activity was almost the same as those of sparfloxacin and tosufloxacin and was 4 and 16 times superior to those of levofloxacin and ciprofloxacin, respectively, but lower than those of clarithromycin and minocycline (range for each, 0.016 to 0.031 microg/ml). The minimal chlamydiacidal concentration of AM-1155 ranged from 0.063 to 0.125 microg/ml, while those of clarithromycin and minocycline ranged from 0.016 to 0.031 microg/ml and 0.016 to 0.063 microg/ml, respectively. The therapeutic effect of a 7-day course of AM-1155 at doses of 5 and 10 mg/kg of body weight administered orally twice daily to mice with experimental Chlamydia psittaci pneumonia was excellent, with a 100% survival rate at 21 days after infection. The efficacy was equal to those of clarithromycin and minocycline and higher than those of ciprofloxacin and ofloxacin.
Comparative activity of trovafloxacin, alone and in combination with other agents, against gram-negative nonfermentative rods
Authors: Visalli M A , Bajaksouzian S , Jacobs M R , Appelbaum P C
Published: October 2018

In the first part of this study, agar dilution MICs were used to test the activities of trovafloxacin, ciprofloxacin, ofloxacin, levofloxacin, sparfloxacin, clinafloxacin, ceftazidime, and imipenem against 458 gram-negative nonfermenters. The overall respective MICs at which 50% of isolates are inhibited (MIC50s) and MIC90s were as follows: trovafloxacin, 1.0 and 16.0 microg/ml; ciprofloxacin, 2.0 and 16.0 microg/ml; ofloxacin, 2.0 and 32.0 microg/ml; levofloxacin, 1.0 and 16.0 microg/ml; sparfloxacin, 1.0 and 16.0 microg/ml; clinafloxacin, 0.5 and 4.0 microg/ml; ceftazidime, 8.0 and 128.0 microg/ml; imipenem, 2.0 and 256.0 microg/ml. Clinafloxacin was the most active of all the quinolones tested. The MIC90s of trovafloxacin were < or = 4.0 microg/ml for Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Flavobacterium odoratum, and Chryseobacterium meningosepticum; trovafloxacin MIC90s were < or = 2.0 microg/ml for Moraxella spp., Pseudomonas stutzeri, and Chryseobacterium indologenes-C. gleum. Of the other quinolones tested, the MICs of sparfloxacin and levofloxacin were lower than those of ciprofloxacin and ofloxacin. High ceftazidime MICs (> or = 32.0 microg/ml) were observed for all nonfermentative species tested. Although for the majority of strains tested imipenem MICs were < or = 8.0 microg/ml, high imipenem MICs were observed for many species, especially S. maltophilia, Burkholderia cepacia, F. odoratum, and Chryseobacterium meningosepticum. For Alcaligenes xylosoxidans strains, the MICs of all compounds were generally a few dilutions lower than those for Alcaligenes faecalis-A. odorans. Time-kill studies with five strains revealed that trovafloxacin and all quinolones yielded more rapid time-kill kinetics than ceftazidime and imipenem. Synergy testing by checkerboard titrations of 286 strains with trovafloxacin combined with ceftazidime, amikacin, and imipenem revealed fractional inhibitory concentration (FIC) indices in the range indicating synergism (< or = 0.5) for 81, 41, and 40 strains, respectively, and FIC indices indicating additivity or indifference (> 0.5 to 4.0) for 205, 245, and 246 strains, respectively. No FIC indices indicating antagonism (> 4.0) were observed. Synergy between trovafloxacin and ceftazidime was found for 32 of 36 S. maltophilia strains. Time-kill studies with 20 strains showed that for most strains for which FIC indices were in the range indicating additivity or indifference, FIC indices indicated synergy by the time-kill method. Synergy was particularly noticeable for S. maltophilia strains with combinations of ceftazidime and trovafloxacin.
Rifabutin absorption in the gut unaltered by concomitant administration of didanosine in AIDS patients
Authors: Li R C , Narang P K , Sahai J , Cameron W , Bianchine J R
Published: October 2018

Didanosine (ddI) is currently used in the management of patients infected by the human immunodeficiency virus. Rifabutin (RBT) is being extensively used for prophylaxis against Mycobacterium avium complex (MAC) infections. Due to its acid-labile characteristics, ddI must be administered with a buffer. Recent reports have indicated that absorption of ketoconazole, ciprofloxacin, and dapsone, etc., in the gut is altered by concomitant ddI dosing. We have assessed whether concomitant dosing of ddI as antiretroviral therapy modifies RBT absorption in the gut, its steady-state pharmacokinetics, and/or safety in 15 patients with AIDS. Of the 15 patients enrolled, 12 completed the study and 3 receiving 600 mg of RBT with concomitant ddI administration withdrew prematurely from the study. Steady-state RBT pharmacokinetics were assessed on day 13 (ddI plus RBT) and day 16 (RBT alone). The ddI doses (adjusted for body weight) were 167 to 375 mg twice daily, while RBT was administered as a single 300- or 600-mg daily dose. No statistically significant (P > 0.05) differences were seen in RBT absorption parameter estimates between days 13 and 16: maximum concentration in plasma (Cmax; 511 +/- 341 ng/ml versus 525 +/- 254 ng/ml) and the time at which Cmax was observed (3.0 versus 2.5 h). The mean RBT estimates for area under the concentration-time curve from 0 to 24 h (AUC(0-tau)) (5,650 versus 5,023 ng x h/ml) and for oral clearance (1.28 versus 1.18 liter/h/kg) on both study days were also similar. Assessment based on urinary recovery of RBT (3.1 versus 3.7 mg) and its predominant deacetyl metabolite, LM565 (1.6 versus 1.4 mg), showed no apparent effect of ddI. The fraction of the RBT dose converted to LM565, as suggested by the ratio of AUC of the metabolite to AUC of the parent drug, was also unaltered (0.15 versus 0.12). A ratio analysis (day 13/day 16) of the RBT pharmacokinetic estimates showed that the 95% confidence intervals for all parameters were inclusive of one. Furthermore, the brief interruption of ddI therapy over this short study period at steady state produced no clinically significant changes in body weight, hematology, and renal and pancreatic functions. Therefore, concomitant administration of ddI appears not to affect RBT absorption in the gut and its disposition or safety in patients with AIDS.
Comparison of cefdinir and cefaclor in treatment of community-acquired pneumonia
Authors: Drehobl M , Bianchi P , Keyserling C H , Tack K J , Griffin T J
Published: October 2018

Six hundred ninety patients were enrolled in a multicenter, randomized, double-blind trial comparing the efficacy and safety of cefdinir with those of cefaclor in the treatment of community-acquired pneumonia. Patients received either 10 days of treatment with cefdinir (n = 347) at 300 mg twice daily or 10 days of treatment with cefaclor (n = 343) at 500 mg three times daily. Microbiological assessments were performed on sputum specimens obtained at admission and at the two posttherapy visits, if available. Respiratory tract pathogens were isolated from 538 (78%) of 690 patient admission sputum specimens, with the predominant pathogens being Haemophilus parainfluenzae, Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus. The microbiological eradication rates at the test-of-cure visit were 92% (238 of 260 pathogens) and 93% (245 of 264 pathogens) for the evaluable patients treated with cefdinir and cefaclor, respectively. A satisfactory clinical response (cure plus improvement) was achieved in 89% (166 of 187) and 86% (160 of 186) of the evaluable patients treated with cefdinir and cefaclor, respectively. Except for the incidence of diarrhea, adverse event rates while on treatment were equivalent between the two treatment groups. Diarrhea incidence during therapy was higher for patients treated with cefdinir (13.7%) than for patients treated with cefaclor (5.3%). These results indicate that cefdinir is effective and safe in the treatment of patients with pneumonia.
Molecular analysis of katG gene mutations in strains of Mycobacterium tuberculosis complex from Africa
Authors: Haas W H , Schilke K , Brand J , Amthor B , Weyer K , Fourie P B , Bretzel G , Sticht-Groh V , Bremer H J
Published: October 2018

A sample of 124 isoniazid (INH)-resistant and 88 susceptible strains of Mycobacterium tuberculosis complex from south, central, and west Africa was analyzed by direct sequence analysis and PCR-restriction fragment length polymorphism analysis of their catalase-peroxidase (katG) genes. Point mutations at codon 315 were found in the genomes of 64% of INH-resistant strains, but no complete deletions were identified. Mutations at codon 463 were independent of INH resistance and were linked to the geographic origins of the strains.
Structure-activity relationship of carbacephalosporins and cephalosporins: antibacterial activity and interaction with the intestinal proton-dependent dipeptide transport carrier of Caco-2 cells
Authors: Snyder N J , Tabas L B , Berry D M , Duckworth D C , Spry D O , Dantzig A H
Published: October 2018

An intestinal proton-dependent peptide transporter located on the lumenal surface of the enterocyte is responsible for the uptake of many orally absorbed beta-lactam antibiotics. Both cephalexin and loracarbef are transported by this mechanism into the human intestinal Caco-2 cell line. Forty-seven analogs of the carbacephalosporin loracarbef and the cephalosporin cephalexin were prepared to evaluate the structural features necessary for uptake by this transport carrier. Compounds were evaluated for their antibacterial activities and for their ability to inhibit 1 mM cephalexin uptake and, subsequently, uptake into Caco-2 cells. Three clinically evaluated orally absorbed carbacephems were taken up by Caco-2 cells, consistent with their excellent bioavailability in humans. Although the carrier preferred the L stereoisomer, these compounds lacked antibacterial activity and were hydrolyzed intracellularly in Caco-2 cells. Compounds modified at the 3 position of cephalexin and loracarbef with a cyclopropyl or a trifluoromethyl group inhibited cephalexin uptake. Analogs with lipophilic groups on the primary amine of the side chain inhibited cephalexin uptake, retained activity against gram-positive bacteria but lost activity against gram-negative bacteria. Substitution of the phenylglycl side chain with phenylacetyl side chains gave similar results. Compounds which lacked an aromatic ring in the side chain inhibited cephalexin uptake but lost all antibacterial activity. Thus, the phenylglycl side chain is not absolutely required for uptake. Different structural features are required for antibacterial activity and for being a substrate of the transporter. Competition studies with cephalexin indicate that human intestinal Caco-2 cells may be a useful model system for initially guiding structure-activity relationships for the rational design of new oral agents.
Efficacy of azithromycin or clarithromycin for prophylaxis of viridans group streptococcus experimental endocarditis
Authors: Rouse M S , Steckelberg J M , Brandt C M , Patel R , Miro J M , Wilson W R
Published: October 2018

The efficacy of azithromycin or clarithromycin was compared to that of amoxicillin, clindamycin, or erythromycin for the prevention of viridans group streptococcus experimental endocarditis. Rabbits with catheter-induced aortic valve vegetations were given no antibiotics or two doses of amoxicillin at 25 mg/kg of body weight, azithromycin at 10 mg/kg, clarithromycin at 10 mg/kg, clindamycin at 40 mg/kg followed by clindamycin at 20 mg/kg, or erythromycin at 10 mg/kg. Antibiotics were administered 0.5 h before and 5.5 h after intravenous infusion of 5 x 10(5) CFU of Streptococcus milleri. Forty-eight hours after bacterial inoculation, the rabbits were killed and aortic valve vegetations were aseptically removed and cultured for bacteria. Infective endocarditis occurred in 88% of untreated animals, 1% of animals receiving amoxicillin, 9% of animals receiving erythromycin, 0% of animals receiving clindamycin, 2.5% of animals receiving clarithromycin, and 1% of animals receiving azithromycin. All five regimens were more effective (P < 0.001) than no prophylaxis. Erythromycin was less effective (P < 0.05) than amoxicillin or clindamycin. Azithromycin or clarithromycin was as effective as amoxicillin, clindamycin, or erythromycin for the prevention of viridans group streptococcus experimental endocarditis in this model.
Combination of flucloxacillin and gentamicin inhibits toxic shock syndrome toxin 1 production by Staphylococcus aureus in both logarithmic and stationary phases of growth
Authors: van Langevelde P , van Dissel J T , Meurs C J , Renz J , Groeneveld P H
Published: October 2018

Production of exotoxins by staphylococci and streptococci may lead to the development of toxic shock syndrome (TSS). Because clindamycin inhibits exotoxin production, its use has been advocated for the treatment of TSS. However, the bacteriostatic action of clindamycin might be a disadvantage for the treatment of overwhelming infections. We investigated the effects of flucloxacillin and gentamicin on exotoxin production, because incubation with these antibiotics combines bactericidal action with protein synthesis inhibition. Staphylococcus aureus during the logarithmic and stationary phases of growth was incubated with either clindamycin, flucloxacillin, or a combination of flucloxacillin and gentamicin at concentrations of 2 or 10 times the MIC. In logarithmic-phase cultures clindamycin had a static effect on bacterial growth. After incubation with flucloxacillin, either alone or in combination with gentamicin, a rapid and large reduction in the number of viable bacteria was demonstrated. In stationary-phase cultures none of the antibiotics significantly changed the number of viable bacteria. TSS toxin 1 (TSST-1) production during logarithmic-phase growth was inhibited by > or =95% by all antibiotics. In stationary-phase cultures, clindamycin, flucloxacillin, and the combination of flucloxacillin and gentamicin inhibited TSST-1 production by 95, 30, and 75%, respectively, compared with the level of exotoxin production in the controls. The present results indicate that clindamycin inhibits TSST-1 production and exerts bacteriostatic activity in both bacterial growth phases. Because the combination of flucloxacillin and gentamicin combines the inhibition of exotoxin production with high bactericidal activity at least in logarithmic-phase cultures, it should be considered an alternative to clindamycin for the treatment of exotoxin-mediated diseases, especially in patients with overwhelming infections.
Hypoxanthine phosphoribosyltransferase from Trypanosoma cruzi as a target for structure-based inhibitor design: crystallization and inhibition studies with purine analogs
Authors: Eakin A E , Guerra A , Focia P J , Torres-Martinez J , Craig S P
Published: October 2018

The hypoxanthine phosphoribosyltransferase (HPRT) from Trypanosoma cruzi is a potential target for enzyme structure-based inhibitor design, based on previous studies which indicate that these parasites lack the metabolic enzymes required for de novo synthesis of purine nucleotides. By using a bacterial complement selection system, 59 purine analogs were assayed for their interaction with the HPRTs from T. cruzi and Homo sapiens. Eight compounds were identified from the bacterial assay to have an affinity for the trypanosomal enzyme. Inhibition constants for four of these compounds against purified recombinant trypanosomal and human HPRTs were determined and compared. The results confirm that the recombinant system can be used to identify compounds which have affinity for the trypanosomal HPRT. Furthermore, the results provide evidence for the importance of chemical modifications at positions 6 and 8 of the purine ring in the binding of these compounds to the HPRTs. An accurate three-dimensional structure of the trypanosomal enzyme will greatly enhance our understanding of the interactions between HPRTs and these compounds. Toward this end, crystallization conditions for the trypanosomal HPRT and preliminary analysis of X-ray diffraction data to a resolution of 2 A is reported. These results represent significant progress toward a structure-based approach to the design of inhibitors of the HPRT of trypanosomes with the long-range goal of developing new drugs for the treatment of Chagas' disease.
Inducible expression of human hepatitis B virus (HBV) in stably transfected hepatoblastoma cells: a novel system for screening potential inhibitors of HBV replication
Authors: Ladner S K , Otto M J , Barker C S , Zaifert K , Wang G H , Guo J T , Seeger C , King R W
Published: October 2018

We report the development and isolation of a cell line, termed HepAD38, that replicates human hepatitis B virus (HBV) under conditions that can be regulated with tetracycline. In the presence of the antibiotic, this cell line is free of virus due to the repression of pregenomic (pg) RNA synthesis. Upon removal of tetracycline from the culture medium, the cells express viral pg RNA, accumulate subviral particles in the cytoplasm that contain DNA intermediates characteristic of viral replication, and secrete virus-like particles into the supernatant. Since the HepAD38 cell line can produce high levels of HBV DNA, it should be useful for analyses of the viral replication cycle that depend upon viral DNA synthesis in a synchronized fashion. In addition, this cell line has been formatted into a high-throughput, cell-based assay that permits the large-scale screening of diverse compound libraries for new classes of inhibitors of HBV replication.
Inhibition of replication of hepatitis B virus by cytallene in vitro
Authors: Zhu Y L , Pai S B , Liu S H , Grove K L , Jones B C , Simons C , Zemlicka J , Cheng Y C
Published: October 2018

The acyclic cytosine nucleoside analog cytallene [1-(4'-hydroxy-1',2'-butadienyl)cytosine], which has both (+)- and (-)-enantiomers, was evaluated for its anti-hepatitis B virus (HBV) activity in 2.2.15 cells and was found to have potent activity against HBV DNA synthesis. The R-(-)-enantiomer was found to be the more active of the cytallene enantiomers, with a 50% inhibition concentration against HBV synthesis (HBIC50) of 0.08 microM. Its antiviral activity could be reversed by deoxycytidine (dC) and less efficiently by cytidine. Upon removal of the R-(-)-enantiomer from culture medium, the synthesis of HBV DNA could reinitiate, which suggested that the antiviral action is reversible. The R-(-)-enantiomer was also found to be more cytotoxic than the S-(+)-enantiomer. The degree of cytotoxicity varied among the cell lines, with a 50% inhibition of cell growth at greater than 10 microM. The R-(-)-enantiomer had no effect on HBV RNA synthesis and mitochondrial DNA synthesis at a concentration of 10 times or more than the HBIC50. The two enantiomers cannot be deaminated by dC deaminase, and they can be phosphorylated by cytoplasmic dC kinase. The R-(-)-enantiomer of cytallene is the first acyclic cytosine analog with potent inhibitory activity against HBV similar to those of other L-(-)-ddC analogs.
Influence of electric fields and pH on biofilm structure as related to the bioelectric effect
Authors: Stoodley P , deBeer D , Lappin-Scott H M
Published: October 2018

Mixed species biofilms of Klebsiella pneumoniae, Pseudomonas fluorescens, and Pseudomonas aeruginosa were grown in a flow cell fitted with two platinum wire electrodes. The biofilm growing on the wires reached a thickness of approximately 50 microm after 3 days. When a voltage was applied with oscillating polarity, the biofilm attached to the wire expanded and contracted. The biofilm expanded by approximately 4% when the wire was cathodic but was reduced to 74% of the original thickness when the wire was anodic. The phenomenon was reproduced by alternately flushing the flow cell with media adjusted to pH 3 and pH 10 with no electric current. At pH 10 the biofilm was unaltered, but it became compacted to 69% of the original thickness at pH 3. We explained these phenomena in terms of the molecular interactions between charged acidic groups in the biofilm slime and the bacterial cell walls. Contraction of the biofilm under acidic conditions may be caused by (i) the elimination of electrostatic repulsion from neutralization of negatively charged carboxylate groups through protonation and (ii) subsequent hydrogen bonding between the carboxylic acids and oxygen atoms in the sugars. Electrostatic interactions between negatively charged groups in the biofilm and the charged wire may also be expected to cause biofilm expansion when the wire was cathodic and contraction when the wire was anodic. The consequences of the explanation of the increased susceptibility of biofilm cells to antibiotics in an electric field, the "bioelectric effect," are discussed.
Streptogramin B biosynthesis in Streptomyces pristinaespiralis and Streptomyces virginiae: molecular characterization of the last structural peptide synthetase gene
Authors: de Crécy-Lagard V , Saurin W , Thibaut D , Gil P , Naudin L , Crouzet J , Blanc V
Published: October 2018

Streptomyces pristinaespiralis and S. virginiae both produce closely related hexadepsipeptide antibiotics of the streptogramin B family. Pristinamycins I and virginiamycins S differ only in the fifth incorporated precursor, di(mono)methylated amine and phenylalanine, respectively. By using degenerate oligonucleotide probes derived from internal sequences of the purified S. pristinaespiralis SnbD and SnbE proteins, the genes from two streptogramin B producers, S. pristinaespiralis and S. virginiae, encoding the peptide synthetase involved in the activation and incorporation of the last four precursors (proline, 4-dimethylparaaminophenylalanine [for pristinamycin I(A)] or phenylalanine [for virginiamycin S], pipecolic acid, and phenylglycine) were cloned. Analysis of the sequence revealed that SnbD and SnbE are encoded by a unique snbDE gene. SnbDE (4,849 amino acids [aa]) contains four amino acid activation domains, four condensation domains, an N-methylation domain, and a C-terminal thioesterase domain. Comparison of the sequences of 55 amino acid-activating modules from different origins confirmed that these sequences contain enough information for the performance of legitimate predictions of their substrate specificity. Partial sequencing (1,993 aa) of the SnbDE protein of S. virginiae allowed comparison of the proline and aromatic acid activation domains of the two species and the identification of coupled frameshift mutations.
High relapse rate among lepromatous leprosy patients treated with rifampin plus ofloxacin daily for 4 weeks
Authors: Ji B , Jamet P , Sow S , Perani E G , Traore I , Grosset J H
Published: October 2018

Fifty-one lepromatous leprosy patients, all of whom had relapsed after previous dapsone (DDS) monotherapy, were treated between 1990 and 1991 with 600 mg of rifampin (RMP) plus 400 mg of ofloxacin (OFLO) daily for 4 weeks, and the great majority of the patients were followed up at least once a year after completion of the treatment. After only 173 patient-years of follow-up, 5 relapses had been detected; the overall relapse rate was 10.0% (confidence limits, 1.7 and 18.3%), or 2.9 relapses (confidence limits, 0.4 and 5.4) per 100 patient-years. The unacceptably high relapse rate indicated that 4 weeks of treatment with daily RMP-OFLO was unable to reduce the number of viable Mycobacterium leprae organisms to a negligible level. In addition, the M. leprae from one of the relapses were proved to have multiple resistance to DDS, RMP, and OFLO. To avoid further relapses, the follow-up was terminated and the great majority of the patients were retreated with the standard 2-year multidrug therapy from 1994. No further relapse has been diagnosed since the beginning of retreatment.
Effect of foscarnet cream on experimental UV radiation-induced herpes labialis
Authors: Bernstein D I , Schleupner C J , Evans T G , Blumberg D A , Bryson Y , Grafford K , Broberg P , Martin-Munley S , Spruance S L
Published: October 2018

A topical 3% foscarnet cream formulation was evaluated for its ability to treat experimental UV radiation (UVR)-induced herpes labialis in a double-blind study. Healthy adult volunteers with a history of sunlight-induced herpes labialis were randomly assigned at four centers to receive either foscarnet cream (n = 152) or a vehicle control (n = 150). Following measurement of the minimal erythematous dose (MED), the subjects' lips were exposed to 4 MEDs of UV light. Subjects applied the cream on the UVR-exposed area approximately eight times daily beginning immediately after UVR exposure and continuing for 7 days, or until all lesions had a minimum of 4 days of treatment. There were no significant differences between groups in the percentages of subjects that developed any lesion, aborted lesions (did not progress beyond a papule), immediate lesions (developed within 48 h of UVR), or delayed classic lesions (developed 48 h to 7 days after UVR). Treatment with foscarnet significantly reduced the mean lesion area (49 versus 81 mm2; P = 0.01), the maximum lesion area (80 versus 141 mm2; P = 0.01), and the time to healing (P = 0.03) of the delayed classic lesions (n = 78). There was also a trend for a decrease in the mean duration of these lesions (156 versus 191 h; P = 0.08) and the duration of pain (3.9 versus 4.3 days; P = 0.06) in foscarnet-treated subjects. There were no clinically significant adverse reactions. These data suggest that topical foscarnet can be efficacious and deserves further evaluation for the treatment of herpes labialis.
Synergistic anticryptosporidial potential of the combination alpha-1-antitrypsin and paromomycin
Authors: Forney J R , Yang S , Healey M C
Published: October 2018

The combined effect of the serine protease inhibitor alpha-1-antitrypsin (AAT) and the aminoglycoside paromomycin on Cryptosporidium parvum infection in vitro was investigated. AAT and paromomycin were mixed with C. parvum oocysts as either single or combined treatments and used to inoculate epithelial cell cultures. Single- and combined-treatment groups had significantly lower (P < 0.01) parasite numbers than untreated controls. The mean fractional inhibitory concentration indices suggested significant synergistic activity.