bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of antimicrobial activities of clarithromycin and 14-hydroxyclarithromycin against three strains of Haemophilus influenzae by using an in vitro pharmacodynamic model
Authors: Walker K J , Larsson A J , Zabinski R A , Rotschafer J C
Published: June 2012

An in vitro pharmacodynamic model was used to simulate the in vivo pharmacokinetics of clarithromycin and 14-hydroxyclarithromycin in order to generate time-kill curves for three clinical isolates of Haemophilus influenzae (isolates 2019, 91-183, and 1746). Representative concentrations in serum or lung tissue and the pharmacokinetic parameters of clarithromycin and the 14-hydroxy metabolite, separately and in combination, were simulated for the time-kill studies. Amoxicillin-clavulanic acid was used as a control drug. The simulation of typical concentrations of the macrolides in serum in time-kill studies resulted in magnitudes of bacterial killing that were less than (for strains 2019 and 91-183, MICs = 4 mg/liter for clarithromycin and 14-hydroxy-clarithromycin) or equal to (for strain 1746, MIC = 1 mg/liter for clarithromycin and 14-hydroxyclarithromycin) those observed in amoxicillin-clavulanic acid studies. When typical concentrations in lung tissue were simulated, total log decreases in bacterial counts were greater than those achieved with typical concentrations in serum and, in the case of strain 1746, exceeded the magnitude observed with the control drug. In each case, the time to 3-log-unit killing was longer for the macrolides than for amoxicillin-clavulanic acid. Time-kill curve analyses demonstrated the presence of synergy (defined as a 2-log-unit decrease in the CFU per milliliter between the combination and the most active constituent at any time point) for the combination of clarithromycin and 14-hydroxyclarithromycin at simulated concentrations in serum for one strain of H. influenzae (isolate 91-183). Synergism is likely bacterial strain specific, and the presence of synergy may be dependent on the antibiotic concentrations that are tested. Evaluation of the kill curve kinetics in terms of bactericidal rate for the various starting concentrations of clarithromycin did not result in a clear demonstration of either concentration-dependent or concentration-independent bactericidal activity.
Biochemical properties of inducible beta-lactamases produced from Xanthomonas maltophilia
Authors: Paton R , Miles R S , Amyes S G
Published: June 2012

Four different beta-lactamases have been found in several strains of Xanthomonas maltophilia isolated from blood cultures during 1984 to 1991 at the Edinburgh Royal Infirmary. One was a metallo-beta-lactamase with predominantly penicillinase activity and an isoelectric point of 6.8. Its molecular size as determined by gel filtration was 96 kDa but was only 26 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), suggesting a tetramer of four equal subunits. The enzyme hydrolyzed all classes of beta-lactams except the monobactam aztreonam. This enzyme was not inhibited by potassium clavulanate or BRL 42715 but was inhibited by p-chloromercuribenzoate, mercuric chloride, and EDTA. The beta-lactamase was unstable in 50 mM sodium phosphate buffer (pH 8.0) but stable in 50 mM Tris HCl (pH 8.0). The other beta-lactamases focused as a series of different isoelectric points, ranging from pI 5.2 to 6.6. Together, these enzymes exhibited a broad spectrum of activity, hydrolyzing most classes of beta-lactams but not imipenem or aztreonam. Their molecular size was 48 kDa by Sephadex gel filtration and 24 kDa by SDS-PAGE, indicating that they were enzymes consisting of two equal subunits. They were inhibited by p-chloromercuribenzoate, mercuric chloride, potassium clavulanate, and BRL 42715 but not EDTA. This study demonstrated that X. maltophilia produces more than just the L1 and L2 beta-lactamases.
Concentrations in serum and distribution in tissue of free and liposomal amphotericin B in rats during continuous intralipid infusion
Authors: Wasan K M , Grossie V B , Lopez-Berestein G
Published: June 2012

The influences of Intralipid (IL) and 0.45% normal-saline infusions on the concentration in serum and distribution in tissue of amphotericin B (AmpB) and liposomal amphotericin B (L-AmpB) in rats were compared. In animals receiving a continuous IL infusion, concentrations of AmpB in kidneys and lungs were significantly higher, but the concentration of AmpB in serum was significantly lower in animals administered AmpB versus those given L-AmpB. In animals receiving a continuous normal-saline infusion concentrations of AmpB in kidneys and the spleen were significantly higher, but the concentration of AmpB in serum was significantly lower in animals administered AmpB versus those given L-AmpB. These results suggest that the increased total serum cholesterol and high-density lipoprotein cholesterol during the IL infusion decreased the clearance of AmpB from the bloodstream and decreased the L-AmpB concentration in the kidney and lung.
Transport of 9-(2-phosphonomethoxyethyl)adenine across plasma membrane of HeLa S3 cells is protein mediated
Authors: Cihlár T , Rosenberg I , Votruba I , Holý A
Published: June 2012

9-(2-Phosphonomethoxyethyl)adenine (PMEA) is an acyclic adenine nucleotide analog which exhibits potent and selective antiviral activity against herpesviruses and retroviruses. The study of [14C]PMEA uptake in HeLa S3 cells has shown that intracellular levels of the drug plateau after 1 h. Transport across the plasma membrane is saturable (concentration at half-maximal saturation [Kt], 0.39 microM; maximum rate of uptake [Vmax], 1.72 pmol/min.10(6) cells), and it can operate against the concentration gradient. Its significant dependence on temperature and on cellular density has been demonstrated. Following the treatment of cells with proteases, PMEA uptake strongly decreases. The transport process is considerably specific, since only a few phosphonate analogs act effectively as competitive inhibitors. Of these, 9-(2-phosphonomethoxyethyl)-2,6-diaminopurine (Ki = 0.24 microM) is the most efficient. Also, natural nucleotides competitively inhibit PMEA transport, depending on the nature of the nucleobase (thymine = adenine > guanine > cytosine < uracil) and on the position and number of phosphate groups. Nucleosides and nucleobases do not interfere with PMEA uptake. Cellular transport of adenosine and thymidine or uptake of AMP and ATP via conjugated activity of ectonucleotidases and nucleoside transporters is not affected by PMEA. By using vectorial labeling of plasma membrane proteins with Na125I combined with affinity chromatography, a 50-kDa protein which may mediate cellular transport of PMEA has been identified.
Modification of immune response in mice by ciprofloxacin
Authors: Jimenez-Valera M , Sampedro A , Moreno E , Ruiz-Bravo A
Published: June 2012

Some studies have suggested that the addition of ciprofloxacin to in vitro cultures of mitogen-stimulated lymphocytes exerts inhibitory effects on cell cycle progression and immunoglobulin (Ig) secretion. We tested the effects of this drug on some immunity parameters in BALB/c mice. Mice treated intraperitoneally with ciprofloxacin (10 mg/kg of body weight per day) for 3 consecutive days and immunized with sheep erythrocytes 24 h after the last injection showed significant suppression of hemolytic IgG-forming cells, whereas the response of IgM-forming cells remained unchanged. When treatment lasted 7 days the response of antibody-forming cells was not modified. When the 3-day treatment was started at 24 h after immunization with sheep erythrocytes, the response of IgM-forming cells was increased, whereas the response of IgG-forming cells was suppressed. Delayed-type hypersensitivity to sheep erythrocytes was significantly suppressed in animals that received the 3-day treatment with ciprofloxacin and were immunized subcutaneously 24 h after the last injection. In vitro proliferation of lymphocytes from ciprofloxacin-treated mice in response to either lipopolysaccharide or concanavalin A was also suppressed. Leukopenia and an increase in the level of granulocyte-macrophage colony-forming cells in bone marrow were also observed in ciprofloxacin-treated mice. These results, together with those from other reports, suggest that modification of the biological responses by ciprofloxacin is a complex phenomenon that may be influenced by several factors.
Effect of pyrimido[1,6-a]benzimidazoles, quinolones, and Ca2+ on the DNA gyrase-mediated cleavage reaction
Authors: Gmünder H , Kuratli K , Keck W
Published: June 2012

The quinolones inhibit the A subunit of DNA gyrase in the presence of Mg2+ by interrupting the DNA breakage and resealing steps, and the latter step is also retarded without quinolones if Mg2+ is replaced by Ca2+. Pyrimido[1,6-a]benzimidazoles have been found to represent a new class of potent DNA gyrase inhibitors which also act at the A subunit. To determine alterations in the DNA sequence specificity of DNA gyrase for cleavage sites in the presence of inhibitors of both classes or in the presence of Ca2+, we used DNA restriction fragments of 164, 85, and 71 bp from the pBR322 plasmid as model substrates. Each contained, at a different position, the 20-bp pBR322 sequence around position 990, where DNA gyrase preferentially cleaves in the presence of quinolones. Our results show that pyrimido[1,6-a]benzimidazoles have a mode of action similar to that of quinolones; they inhibit the resealing step and influence the DNA sequence specificity of DNA gyrase in the same way. Differences between inhibitors of both classes could be observed only in the preferences of DNA gyrase for these cleavage sites. The 20-bp sequence appeared to have some properties that induced DNA gyrase to cleave all three DNA fragments in the presence of inhibitors within this sequence, whereas cleavage in the presence of Ca2+ was in addition dependent on the length of the DNA fragments.
Kinetic analysis of extension of substrate specificity with Xanthomonas maltophilia, Aeromonas hydrophila, and Bacillus cereus metallo-beta-lactamases
Authors: Felici A , Amicosante G
Published: June 2012

Twenty beta-lactam molecules, including penicillins, cephalosporins, penems, carbapenems, and monobactams, were investigated as potential substrates for Xanthomonas maltophilia ULA-511, Aeromonas hydrophila AE036, and Bacillus cereus 5/B/6 metallo-beta-lactamases. A detailed analysis of the kinetic parameters examined confirmed these enzymes to be broad-spectrum beta-lactamases with different ranges of catalytic efficiency. Cefoxitin and moxalactam, substrates for the beta-lactamases from X. maltophilia ULA-511 and B. cereus 5/B/6, behaved as inactivators of the A. hydrophila AE036 metallo-beta-lactamase, which appeared to be unique among the enzymes tested in this study. In addition, we report a new, faster, and reliable purification procedure for the B. cereus 5/B/6 metallo-beta-lactamase, cloned in Escherichia coli HB101.
Biliary and renal excretions of cefpiramide in Eisai hyperbilirubinemic rats
Authors: Muraoka I , Hasegawa T , Nadai M , Wang L , Haghgoo S , Tagaya O , Nabeshima T
Published: June 2012

Eisai hyperbilirubinemic mutant rats (EHBRs) with conjugated hyperbilirubinemia were recently derived from Sprague-Dawley rats (SDRs). The pharmacokinetic characteristics of the beta-lactam antibiotic cefpiramide (CPM), which is mainly excreted into bile, were investigated in 10- and 20-week-old EHBRs and were compared with those in 20-week-old healthy SDRs. The pharmacokinetic parameters of CPM after an intravenous administration of 20 mg/kg of body weight were estimated for each rat by noncompartmental methods. When compared with age-matched healthy SDRs, significant decreases (by approximately 30%) in the systemic clearance of CPM were observed in 20-week-old EHBRs. The biliary clearance of CPM in 20-week-old EHBRs markedly decreased to less than 10% of that in age-matched healthy SDRs, while total urinary recovery of unchanged CPM increased to threefold and renal clearance doubled. However, no significant differences in any of the pharmacokinetic parameters of CPM were observed between the two groups of EHBRs. There were no significant differences among the three groups in the steady-state volume of distribution of CPM. The present study indicates that hyperbilirubinemia induces an increase in the urinary excretion ability of CPM in return for a reduction in the biliary excretion.
Frequency and mechanism of resistance to antibacterial action of ZM 240401, (6S)-6-fluoro-shikimic acid
Authors: Ewart C D , Jude D A , Thain J L , Nichols W W
Published: June 2012

Spontaneous resistance to (6S)-6-fluoro-shikimic acid arose in Escherichia coli and other enterobacteria at high frequencies, between 10(-5) and 10(-4). Two resistant variants of E. coli were tested for their susceptibilities to the diastereomeric compound, (6R)-6-fluoro-shikimate, and both of them had become resistant to this compound as well. (6S)-6-Fluoro-shikimate-resistant variants of E. coli generally failed to transport [14C]shikimate. In E. coli K-12, (6S)-6-fluoro-shikimate resistance cotransduced with his at the same frequency as shiA, a gene locus that governs shikimate transport phenotypes. We propose that the loss of susceptibility to (6S)-6-fluoro-shikimic acid in spontaneous resistant variants is due to the loss of activity of the transport system by which it enters the bacterial cytoplasm.
SC-52151, a novel inhibitor of the human immunodeficiency virus protease
Authors: Bryant M , Getman D , Smidt M , Marr J , Clare M , Dillard R , Lansky D , DeCrescenzo G , Heintz R , Houseman K
Published: June 2012

SC-52151 is a potent, selective, tight-binding human immunodeficiency virus (HIV) protease inhibitor containing the novel (R)-(hydroxyethyl) urea isostere. The mean 50% effective concentration for lymphotropic, monocytotropic strains and field isolates of HIV type 1 (HIV-1), HIV-2, and simian immunodeficiency virus is 26 ng/ml (43 nM). The combination of SC-52151 and nucleoside reverse transcriptase inhibitors synergistically inhibited HIV-1 replication without additive toxicity. An extended postantiviral effect correlates with inhibition of gag and gag-pol polyprotein processing. SC-52151 is highly protein bound ( >90%) in human plasma, and the level of partitioning into erythrocytes is low. Physiological concentrations of alpha-1-acid glycoprotein, but not albumin, substantially affect the antiviral potency of SC-52151. The oral bioavailability of [14C]SC-52151 is 17% when it is administered as an elixir to the rat, dog, or monkey. Oxidation of the t-butyl moiety is the major route of biotransformation, and elimination is mainly by biliary excretion. No toxicologically significant effects have been observed in animals. Pharmacokinetic and metabolism studies in multiple animal species predict 20 to 30% systemic bioavailability, an elimination half-life of 1 to 2 h, and a volume of distribution of greater than 3 liters/kg in humans.
Decreased activity of erythromycin against Streptococcus pyogenes in Taiwan
Authors: Hsueh P R , Chen H M , Huang A H , Wu J J
Published: June 2012

A total of 78 clinical isolates of Streptococcus pyogenes were collected from January 1992 through December 1993 from patients in southern Taiwan. The in vitro activities of 10 antimicrobial agents were determined by the agar dilution method. Penicillin, cephalothin, cefotaxime, vancomycin, and ofloxacin were shown to be active against S. pyogenes isolates, with MICs at which 90% of isolates are inhibited (MIC90s) being < or = 0.03, < or = 0.13, < or = 0.13, < or = 0.13, and < or = 0.25 microgram/ml, respectively. Erythromycin and azithromycin both had poor activities (MIC50s, 16 and >128 micrograms/ml, respectively; MIC90s, >128 and >128 micrograms/ml, respectively). The activities of tetracycline, clindamycin, and chloramphenicol against a significant number of these isolates were also limited. As the MICs of clindamycin and chloramphenicol for the isolates increased, the MICs of the two macrolides also increased. Clindamycin, chloramphenicol, and the two macrolides were less potent against isolates recovered form throat swab samples than against those from blood or other sources. Isolates of the T12 and T1 serotypes accounted for 53.8% of all isolates. The majority (87.5%) of the isolates recovered from throat swab samples were of the T12 serotype, whereas 19.2% of the isolates recovered from blood were of the T12 serotype. In contrast, 66.7% of the isolates of the T1 serotype were derived from blood but none were derived from throat swab samples. Of the 33 T12 serotype isolates, erythromycin MICs for 78.8% of the isolates were >128 micrograms/ml. Because of the poor activities of erythromycin and azithromycin against S. pyogenes isolates from patients in southern Taiwan, these drugs should no longer be considered the drugs of choice for the management of group A streptococcal infections among patients who live in this area.
The outer membrane protein OprM of Pseudomonas aeruginosa is encoded by oprK of the mexA-mexB-oprK multidrug resistance operon
Authors: Gotoh N , Tsujimoto H , Poole K , Yamagishi J , Nishino T
Published: June 2012

An outer membrane protein (OprK) overproduced in a multiply antibiotic-resistant strain of Pseudomonas aeruginosa was previously identified as the product of the third gene of a multidrug resistance operon, mexA-mexB-oprK (K. Poole, K. Krebes, C. McNally, and S. Neshat, J. Bacteriol. 175:7363-7372, 1993). To determine whether this protein was identical to another outer membrane protein (OprM) also overproduced in some multiply resistant strains, attempts were made to map the transposon insertion site of several OprM-deficient mutants to the mex operon. Amplification of chromosomal DNA of several Tn5 insertion OprM-deficient mutants with primers specific to each gene of the mex operon revealed that the transposon had inserted into mexB in one instance and into oprK in two others. Furthermore, introduction of the cloned mexA-mexB-oprK operon into these mutants restored expression of multidrug resistance, concomitant with OprM production. These data demonstrated that OprM is encoded by the mex operon. OprM and OprK were not, however, immunologically cross-reactive, indicating that they are distinct proteins and that OprK is, in fact, not encoded by the mex operon. This operon is thus renamed mexA-mexB-oprM.
GG167 (4-guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid) is a potent inhibitor of influenza virus in ferrets
Authors: Ryan D M , Ticehurst J , Dempsey M H
Published: June 2012

GG167 (4-guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid) is a novel viral neuraminidase (sialidase) inhibitor which, following intranasal administration in ferrets, is at least 100 to 1,000 times more effective than ribavirin and amantadine against influenza A and B viruses. It retains its activity even when treatments are delayed until 24 h postinfection and has no effect on the serum antibody response to infection.
L-743, 726 (DMP-266): a novel, highly potent nonnucleoside inhibitor of the human immunodeficiency virus type 1 reverse transcriptase
Authors: Young S D , Britcher S F , Tran L O , Payne L S , Lumma W C , Lyle T A , Huff J R , Anderson P S , Olsen D B , Carroll S S
Published: June 2012

The clinical benefit of the human immunodeficiency virus type 1 (HIV-1) nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) is limited by the rapid selection of inhibitor-resistant viral variants. However, it may be possible to enhance the clinical utility of this inhibitor class by deriving compounds that express both high levels of antiviral activity and an augmented pharmacokinetic profile. Accordingly, we developed a new class of NNRTIs, the 1, 4-dihydro-2H-3, 1-benzoxazin-2-ones. L-743, 726 (DMP-266), a member of this class, was chosen for clinical evaluation because of its in vitro properties. The compound was a potent inhibitor of the wild-type HIV-1 RT (Ki = 2.93 nM) and exhibited a 95% inhibitory concentration of 1.5 nM for the inhibition of HIV-1 replicative spread in cell culture. In addition, L-7743, 7726 was found to be capable of inhibiting, with 95% inhibitory concentrations of < or = 1.5 microM, a panel of NNRTI-resistant mutant viruses, each of which expressed a single RT amino acid substitution. Derivation of virus with notably reduced susceptibility to the inhibitor required prolonged cell culture selection and was mediated by a combination of at least two RT amino acid substitutions. Studies of L-743, 726 in rats, monkeys, and a chimpanzee demonstrated the compound's potential for good oral bioavailability and pharmacokinetics in humans.
Inducible NorA-mediated multidrug resistance in Staphylococcus aureus
Authors: Kaatz G W , Seo S M
Published: June 2012

The NorA protein of Staphylococcus aureus mediates the active efflux of hydrophilic fluoroquinolones from the cell, conferring low-level resistance upon the organism. The protein also is capable of transporting additional structurally diverse compounds, indicating that it has a broad substrate specificity. Increased transcription of the norA gene, leading to a greater quantity of the NorA protein within the cytoplasmic membrane, is felt to be the mechanism by which strains possessing such changes resist fluoroquinolones. S. aureus SA-1199 and its in vivo-selected derivative SA-1199B are fluoroquinolone-susceptible and -resistant isolates, respectively; SA-1199B resists hydrophilic fluoroquinolones via a NorA-mediated mediated mechanism in a constitutive manner. SA-1199-3 is an in vitro-produced derivative of SA-1199 in which NorA-mediated multidrug resistance is expressed inducibly. Compared with organisms exposed to subinhibitory concentrations of a NorA substrate for the first time, preexposure of SA-1199-3 to such a compound followed by growth in the presence of that substrate results in the elimination of a 2- to 6-h period of organism killing that occurs prior to the onset of logarithmic growth. The uptake of radiolabeled fluoroquinolone is markedly reduced by preexposure of SA-1199-3 to NorA substrates: such prior exposure also results in a dramatic increase in RNa transcripts that hybridize with a norA probe. Preexposure of SA-1199 and SA-1199B to such substrates results in small increases or no increases in these transcripts. No sequence differences between SA-1199 and SA-1199-3 within the norA gene or flanking DNA were found. It appears likely that the regulation of norA in SA-1193, which may be effected by one or more genetic loci outside the norA region of the chromosome, differs from that of SA-1199 and SA-1199B.
Antituberculosis activity of clarithromycin
Authors: Luna-Herrera J , Reddy V M , Daneluzzi D , Gangadharam P R
Published: June 2012

Antituberculosis activity of clarithromycin (CLA), a macrolide antibiotic, was investigated in vitro, in macrophages, and in C57BL/6 mice, CLA showed high in vitro MICs (4 to > 16 micrograms/ml) for several strains of Mycobacterium tuberculosis and caused slight enhancement of activity of rifampin (RIF) against H37Rv but failed to increase the activity of either RIF or isoniazid (INH) against other strains. However, inside J774A.1 macrophages, CLA showed high activity and was synergistic with RIF against some strains of tubercle bacilli susceptible or resistant to INH and RIF. In the in vivo studies with a drug-susceptible strain (H37Rv), CLA protected mice from mortality due to tuberculosis for up to 8 weeks of observation. The CFU data for lungs and spleens revealed that the antituberculosis activity of CLA is inferior to those of INH and streptomycin. However, the activity of CLA when used alone or in combination was comparable to that of thiacetazone, indicating its potential usefulness as a secondary drug for the treatment of tuberculosis.
Deletion of the Candida glabrata ERG3 and ERG11 genes: effect on cell viability, cell growth, sterol composition, and antifungal susceptibility
Authors: Geber A , Hitchcock C A , Swartz J E , Pullen F S , Marsden K E , Kwon-Chung K J , Bennett J E
Published: June 2012

We have cloned and sequenced the structural genes encoding the delta 5,6 sterol desaturase (ERG3 gene) and the 14 alpha-methyl sterol demethylase (ERG11 gene) from Candida glabrata L5 (leu2). Single and double mutants of these genes were created by gene deletion. The phenotypes of these mutants, including sterol profiles, aerobic viabilities, antifungal susceptibilities, and generation times, were studied. Strain L5D (erg3 delta::LEU2) accumulated mainly ergosta-7,22-dien-3 beta-ol, was aerobically viable, and remained susceptible to antifungal agents but had a slower generation time than its parent strain. L5LUD (LEU2 erg11 delta::URA3) strains required medium supplemented with ergosterol and an anaerobic environment for growth. A spontaneous aerobically viable mutant, L5LUD40R (LEU erg11 delta::URA3), obtained from L5LUD (LEU2 erg11 delta::URA3), was found to accumulate lanosterol and obtusifoliol, was resistant to azole antifungal agents, demonstrated some increase in resistance to amphotericin B, and exhibited a 1.86-fold increase in generation time in comparison with L5 (leu2). The double-deletion mutant L5DUD61 (erg3 delta::LEU2 erg11 delta::URA3) was aerobically viable, produced mainly 14 alpha-methyl fecosterol, and had the same antifungal susceptibility pattern as L5LUD40R (LEU2 erg11 delta::URA3), and its generation time was threefold greater than that of L5 (leu2). Northern (RNA) analysis revealed that the single-deletion mutants had a marked increase in message for the undeleted ERG3 and ERG11 genes. These results indicate that differences in antifungal susceptibilities and the restoration of aerobic viability exist between the C. glabrata ergosterol mutants created in this study and those sterol mutants with similar genetic lesions previously reported for Saccharomyces cerevisiae.
In vitro antibacterial properties of T-5575 and T-5578 novel parenteral 2-carboxypenams
Authors: Watanabe Y , Minami S , Hayashi T , Araki H , Kitayama R , Ochiai H
Published: June 2012

T-5575 and T-5578, novel 2-carboxypenams in which a carboxyl group has been introduced into the C-2 beta position of the nucleus, were evaluated for their in vitro antibacterial properties. The spectrum of activity of T-5575 was similar to that of aztreonam. However, it showed stronger activities than those of aztreonam against most gram-negative bacteria. T-5575 also showed potent activities against isolates of Enterobacter cloacae, Citrobacter freundii, and Pseudomonas aeruginosa resistant to ceftazidime, with MICs at which 90% of the isolates were inhibited of 0.39, 0.39, and 3.13 microgram/ml, respectively. T-5578 showed moderate levels of activity against gram-negative bacteria, compared with those of T-5575. Its activity against P. aeruginosa, however, was superior to those of T-5575 and the reference drugs tested. The most characteristic feature of T-5578 was its potent activities against ceftazidime-, imipenem-, and gentamicin-resistant P. aeruginosa isolates, with MICs at which 90% of the isolates were inhibited at 0.39, 3.13, and 3.13 microgram/ml, respectively. These two compounds were unfortunately poorly active against gram-positive bacteria, such as Staphylococcus aureus and streptococci. Both compounds were found to be stable for hydrolysis by various kinds of beta-lactamases and to have low affinities for these enzymes, with Ki values of > 100 microM. These novel penams bound most tightly to penicillin-binding protein 3 of Escherichia coli and P. aeruginosa. These results indicate that T-5575 and T-5578 can be regarded as promising 2-carboxypenams specially targeted against gram-negative pathogens.
Pharmacokinetics and dose proportionality of ceftibuten in men
Authors: Lin C , Lim J , Radwanski E , Marco A , Affrime M
Published: June 2012

The pharmacokinetics and dose proportionality of ceftibuten were evaluated in healthy male volunteers receiving single oral doses of 200, 400, and 800 mg of ceftibuten. The drug was absorbed with similar times to the maximum concentration of drug in plasma for all three doses. Concentrations of ceftibuten in plasma increased with increasing dose. Analysis of variance was carried out on the dose-adjusted values for the maximum concentration of drug in plasma and the area under the plasma concentration-time curve; the results indicated that the concentrations in plasma after the 200- and 400-mg doses were dose proportional, and after the 800-mg of dose they were less than dose proportional. The elimination half-life from plasma ranged from 2.0 to 2.3 h and was independent of dose. The total excretion of unchanged ceftibuten in urine accounted for 53 to 68% of the dose, and the renal clearance was estimated to be 53 to 61 ml/min after all doses. The amount of ceftibuten-trans, the major in vitro and in vivo conversion product of ceftibuten, was low in both plasma and urine.
Michellamine B, a novel plant alkaloid, inhibits human immunodeficiency virus-induced cell killing by at least two distinct mechanisms
Authors: McMahon J B , Currens M J , Gulakowski R J , Buckheit R W , Lackman-Smith C , Hallock Y F , Boyd M R
Published: June 2012

Studies of the mechanism of action of michellamine B, a novel anti-human immunodeficiency virus (HIV) alkaloid from the tropical plant Ancistrocladus korupensis, have revealed that the compound acts at two distinct stages of the HIV life cycle. The compound had no direct effect on HIV virions and did not block the initial binding of HIV to target cells. Postinfection time course studies revealed that the agent partially inhibited HIV-induced cell killing and syncytium formation when added up to 48 h following acute infection; however, viral reproduction was fully inhibited only when the compound was added immediately after infection. Time-limited treatments of HIV-infected cells revealed that michellamine B had to be present continuously to provide maximum antiviral protection. HIV replication in cells in which infection was already fully established or in chronically infected cells was unaffected by michellamine B. Biochemical studies showed that michellamine B inhibited the enzymatic activities of reverse transcriptases (RTs) from both HIV type 1 and HIV type 2 as well as two different nonnucleoside drug-resistant RTs with specific amino acid substitutions. In addition, human DNA polymerases alpha and beta were inhibited by the alkaloid. Michellamine B exerted a potent dose-dependent inhibition of cell fusion in two independent cell-based fusion assays. Thus, michellamine B acts both at an early stage of the HIV life cycle by inhibiting RT as well as at later stages by inhibiting cellular fusion and syncytium formation.
Comparative efficacies of ciprofloxacin and pefloxacin alone or in combination with fosfomycin in experimental endocarditis induced by multidrug-susceptible and -resistant Pseudomonas aeruginosa
Authors: Xiong Y Q , Potel G , Caillon J , Stephant G , Jehl F , Bugnon D , Le Conte P , Baron D , Drugeon H
Published: June 2012

The in vivo efficacy of ciprofloxacin or pefloxacin alone or in combination with fosfomycin was evaluated in experimental aortic valve endocarditis induced in 133 rabbits by a multidrug-susceptible or multidrug-resistant strain of Pseudomonas aeruginosa. Therapy was initiated early (12 h after infection), when bacterial counts in aortic valve vegetations were relatively low, or late (48 h after infection), when vegetations contained a larger inoculum. Antibodies were administered as a continuous 24-h intravenous infusion. Mean steady-state levels of ciprofloxacin (64 mg/kg), pefloxacin (64 mg/kg), and fosfomycin (300 mg/kg) in serum were 2.5, 4.2, and 63.9 mg/liter, respectively. For the multidrug-susceptible strain, all regimens except pefloxacin alone significantly reduced the number of CFU per gram of vegetation versus controls, whether treatment was performed early or late. For the multidrug-resistant strain, none of the regimens showed differences from untreated controls, except ciprofloxacin-fosfomycin, which significantly reduced bacterial counts in vegetations compared with controls when therapy was begun early (4.1 +/- 1.1 log10 CFU/g of vegetation; P < 0.001 versus the control). These data suggest that combination of fosfomycin with ciprofloxacin or pefloxacin is more effective than ciprofloxacin or pefloxacin alone for the therapy of severe infections caused by multidrug-susceptible P. aeruginosa.
Conjugative transposition of Tn916-related elements from Enterococcus faecalis to Escherichia coli and Pseudomonas fluorescens
Authors: Poyart C , Celli J , Trieu-Cuot P
Published: June 2012

We studied the ability of transposons Tn916, Tn1545, and Tn916-Km, a Tn916 derivative expressing kanamycin resistance, to be conjugatively transferred from Enterococcus faecalis to various gram-negative bacteria. Our results demonstrate that these types of elements can carry out conjugative transposition from the chromosome of E. faecalis to those of Escherichia coli and Pseudomonas fluorescens and that the accomplishment of this event depends on the donor potential of the E. faecalis transposon delivery strain. Since the tet(M) gene does not confer a selectable level of tetracycline resistance to gram-negative bacteria such as E. coli, the presence of another marker(s) readily expressed in these recipients is required for the detection of this type of transfer. Conjugal transfer of Tn916-Km from E. faecalis to E. coli is not restricted by the EcoK restriction system, nor does it depend on the presence of functional homologous recombination system and integration host factor proteins in the recipient bacteria.
Antibacterial activities of cefprozil compared with those of 13 oral cephems and 3 macrolides
Authors: Fung-Tomc J C , Huczko E , Stickle T , Minassian B , Kolek B , Denbleyker K , Bonner D , Kessler R
Published: June 2012

Thirteen oral cephems (cefprozil, loracarbef, cefaclor, cefuroxime axetil, cefpodoxime proxetil, cefetamet pivoxil, cefixime, cefdinir, cefadroxil, cephradine, cephalexin, cefatrizine, and cefroxadine), the cephalosporin class representative cephalothin, cefazolin, and the macrolides erythromycin, clarithromycin, and azithromycin were compared for their antibacterial activities against 790 recent clinical isolates. These oral agents differed in their spectra and antibacterial potencies against community-acquired pathogens.
Identification of the aminocatechol A-3253 as an in vitro poison of DNA topoisomerase I from Candida albicans
Authors: Fostel J , Montgomery D
Published: June 2012

The aminocatechol A-3253 is active against several pathogenic fungi, including Candida albicans, Cryptococcus albidus, and Aspergillus niger. A-3253 interferes with both the in vitro biosynthesis of (1,3)-beta-glucan and the activity of topoisomerases I isolated from Candida spp. It is likely that one or more of the enzymes involved in glucan biosynthesis rather than topoisomerase I is the primary intracellular target of A-3253, since a strain of Saccharomyces cerevisiae lacking topoisomerase I is as susceptible to A-3253 as cells containing wild-type levels of topoisomerase I. However, the interaction of A-3253 with topoisomerase I in vitro is of interest since the Candida topoisomerase is more susceptible to A-3253 than is the topoisomerase I isolated from human HeLa cells. A-3253 is both a reversible inhibitor of topoisomerase I catalysis and a reversible poison of topoisomerase I, and in both reactions the fungal topoisomerase I is more susceptible than the human topoisomerase I to A-3253. In contrast, an earlier study found that the human topoisomerase I is more susceptible than the fungal topoisomerase to camptothecin (J. M. Fostel, D. A. Montgomery, and L. L. Shen, Antimicrob. Agents Chemother. 36:2131-2138, 1992). Taken together with the response to camptothecin, the greater susceptibility of the Candida topoisomerase I to A-3253 suggests that there are structural differences between the human and fungal type I topoisomerases which can likely be exploited to allow for the development of antifungal agents which act against the fungal topoisomerase and which have minimal activity against the human enzyme.
Outer membrane proteins responsible for multiple drug resistance in Pseudomonas aeruginosa
Authors: Masuda N , Sakagawa E , Ohya S
Published: June 2012

Three types of multiple-drug-resistant mutants which were phenotypically similar to previously described nalB, nfxB, and nfxC mutants were isolated from Pseudomonas aeruginosa PAO1 and two clinical isolates. Type 1 (nalB-type) mutants showed cross-resistance to meropenem, cephems, and quinolones. They overproduced an outer membrane protein with an apparent molecular mass of 50 kDa (OprM). Type 2 (nfxB-type) mutants showed cross-resistance to quinolones and new cephems, i.e., cefpirome and cefozopran, concomitant with overproduction of an outer membrane protein with an apparent molecular mass of 54 kDa (OprJ). Type 3 (nfxC-type) mutants showed cross-resistance to carbapenems and quinolones. They produced decreased amounts of OprD and increased amounts of a 50-kDa protein (OprN), which was almost the same molecular weight as that of OprM, but it was distinguishable from OprM by its heat modifiability on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the presence of salicylate, the parent strains showed an increased level of resistance to carbapenems and quinolones and produced decreased amounts of OprD and increased amounts of OprN. Salicylate caused the repression of OprJ production and the loss of resistance to cefpirome and cefozopran in two of the three OprJ-overproducing mutants, although salicylate slightly increased the level of resistance in the parent strains. The changes in susceptibilities were transient in the presence of salicylate. These data suggest that at least three different outer membrane proteins, OprM, OprJ, and OprN, are associated with multiple drug resistance in P. aeruginosa.
Successful treatment of Pneumocystis carinii Pneumonia in mice with benanomicin A (ME1451)
Authors: Yasuoka A , Oka S , Komuro K , Shimizu H , Kitada K , Nakamura Y , Shibahara S , Takeuchi T , Kondo S , Shimada K
Published: June 2012

Benanomicin A (BNM-A) has antimycotic activities via binding to mannan in the cell walls of fungi. Anti-Pneumocystis carinii activity of the agent was examined in the P. carinii-infected BALB/c nu/nu female mouse model because P. carinii also possesses mannan in the membranes. The infected mice were treated with intraperitoneal injections of six doses of BNM-A (1, 2.5, 5, 10, 30, and 100 mg/kg of body weight), 4 mg of pentamidine isethionate per kg, 100 mg of sulfamethoxazole per kg combined with 20 mg of trimethoprim per kg (co-trimoxazole), or saline for 21 days. Each dosage group consisted of 10 mice. During treatment, five mice in the control group (saline) died, whereas 8 to 10 mice in all treatment groups survived. Almost the same efficacies were obtained for the groups treated with 5 mg or more and 10 mg or more of BNM-A per kg regarding the weight and number, respectively, of cysts found in the lungs as were obtained for the groups treated with pentamidine isethionate and co-trimoxazole. Overall, a dose of 10 mg of BNM-A per kg was effective against P. carinii pneumonia infection in the mice. Thus, BNM-A is a good candidate for a novel treatment for P. carinii pneumonia as a compound with a new mechanism of action against P. carinii.
In vitro effects of sulfadiazine and its metabolites alone and in combination with pyrimethamine on Toxoplasma gondii
Authors: Schoondermark-van de Ven E , Vree T , Melchers W , Camps W , Galama J
Published: June 2012

Sulfadiazine and the metabolites N4-acetyl-sulfadiazine, 4-OH-sulfadiazine, 5-OH-sulfadiazine, 5-OH-glucuronide-sulfadiazine, and 5-OH-sulfate-sulfadiazine were tested separately and in combination with pyrimethamine for the inhibitory activity on Toxoplasma gondii growth in vitro. Except for N4-acetyl-sulfadiazine, all sulfa compounds possessed anti-Toxoplasma activity. The addition of 0.05 micrograms of pyrimethamine per ml, a concentration which in itself is not inhibitory, potentiated the microbial activity of sulfadiazine and its metabolites 100 fold.
nfxC-type quinolone resistance in a clinical isolate of Pseudomonas aeruginosa
Authors: Fukuda H , Hosaka M , Iyobe S , Gotoh N , Nishino T , Hirai K
Published: June 2012

Quinolone resistance gene nqr-T91 in a clinical isolate of Pseudomonas aeruginosa P1481 was cotransducible with catA1 in P. aeruginosa PAO. The nqr-T91 transductant, PKH-T91, was resistant to norfloxacin, imipenem, and chloramphenicol and showed less norfloxacin accumulation than the parent strain did. Loss of the 46-kDa outer membrane protein (D2) and an increase in the 50-kDa outer membrane protein in PKH-T91 were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Lipopolysaccharides in the transductant were also changed. These alterations were considered to be related to lower levels of norfloxacin accumulation in PKH-T91. These genetic and biochemical properties suggested that an nfxC type of quinolone-resistant mutation occurred in a clinical isolate of P. aeruginosa P1481.
Fluconazole, D0870, and flucytosine treatment of disseminated Candida tropicalis infections in mice
Authors: Graybill J R , Najvar L K , Holmberg J D , Luther M F
Published: June 2012

D0870 is a recently developed triazole with characteristics of a broad spectrum of activity and slow clearance by nonrenal mechanisms. Herein we have evaluated the efficacy of D0870, alone and combined with flucytosine, in a murine model of disseminated Candida tropicalis infection. Four isolates of C. tropicalis were evaluated. Two were highly susceptible in vitro to fluconazole, and two were resistant to fluconazole. All were highly susceptible to flucytosine and D0870. Animals were pretreated with 5-fluorouracil 1 day before infection because C. tropicalis has reduced virulence in immunocompetent mice. This was done to render them neutropenic for > 10 days. Mice were infected intravenously and treated orally with D0870 or fluconazole, alone or combined with flucytosine. Survival and tissue burden of the spleen and kidneys were used to evaluate the efficacy of antifungal therapy. Fluconazole was less effective for treatment of resistant C. tropicalis than susceptible C. tropicalis. D0870 was more potent than fluconazole and was effective in fluconazole-resistant isolates. Flucytosine was consistently effective when used alone but did not consistently add to the benefit of D0870 or fluconazole. D0870 has potential in treatment of candidiasis caused by C. tropicalis, including fluconazole-resistant isolates.
Use of 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil as a novel antiviral agent for hepatitis B virus and Epstein-Barr virus
Authors: Chu C K , Ma T , Shanmuganathan K , Wang C , Xiang Y , Pai S B , Yao G Q , Sommadossi J P , Cheng Y C
Published: June 2012

A novel anti-hepatitis B virus (anti-HBV) agent, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), was synthesized and found to be a potent anti-HBV and anti-Epstein-Barr virus agent. Its in vitro potency was evaluated in 2.2.15 and H1 cells for anti-HBV and anti-Epstein-Barr virus activities, respectively. In vitro cytotoxicity in MT2, CEM, 2.2.15, and H1 cells was also assessed, and the results indicated high antiviral selectivities of L-FMAU in these cells.
In vivo verification of in vitro model of antibiotic treatment of device-related infection
Authors: Blaser J , Vergères P , Widmer A F , Zimmerli W
Published: June 2012

Device-related infections are difficult to treat with antibiotics alone. Standard susceptibility tests do not correlate with treatment success. Therefore, the utility of a pharmacokinetic in vitro model has been evaluated in comparison with the tissue-cage infection model in guinea pigs. The bactericidal activity of 28 treatment regimens has been studied by using three different test strains. In vitro efficacy was defined as reduction in the number of suspended or adherent bacteria, and in vivo efficacy was defined as reduction in the number of bacteria in tissue-cage fluid. Test results between the two models (in vivo and in vitro) correlated well, with correlation coefficients of 0.85 for in vivo efficacy versus in vitro efficacy against suspended bacteria and 0.72 for in vivo efficacy versus in vitro efficacy against adherent bacteria (P < 0.05) for Staphylococcus aureus, 0.96 and 0.82 (P < 0.05) for Staphylococcus epidermidis, and 0.89 and 0.97 for Escherichia coli, respectively. In contrast, standard susceptibility tests, ratios of MICs to trough or peak levels, ratios of the area under the curve to the MIC, or time above the MIC were not predictive for therapeutic outcome in either the in vitro or in vivo model. In both models, the bactericidal activity levels with combination regimens were significantly higher than those with single-drug regimens (P < 0.001). Furthermore, rifampin combinations with either vancomycin, teicoplanin, fleroxacin, or ciprofloxacin were significantly more bactericidal against adherent bacteria than netilmicin combinations with vancomycin or daptomycin (P < 0.01). Thus, in vivo verification of the pharmacokinetic in vitro model correlated well with the animal model. The in vitro model offers an alternative to ther animal model in experiments that screen and assess antibiotic regimens against device-related infections.
Fluconazole penetration in cerebral parenchyma in humans at steady state
Authors: Thaler F , Bernard B , Tod M , Jedynak C P , Petitjean O , Derome P , Loirat P
Published: June 2012

We studied fluconazole penetration in the brain in five patients who had a deep cerebral tumor whose removal required the excision of healthy brain tissue. Plasma and brain samples were simultaneously obtained after oral ingestion of 400 mg of fluconazole daily for 4 days (90% of steady state). Fluconazole penetration in healthy cerebral parenchyma was determined. Plasma and brain samples were assayed by high-pressure liquid chromatography. Concentrations in plasma and brain tissue were 13.5 +/- 5.5 micrograms/ml and 17.6 +/- 6.6 micrograms/g, respectively. The average ratio of concentrations in the brain and plasma (four patients) was 1.33 (range, 0.70 to 2.39). Despite the lack of data concerning the penetration of fluconazole in brain abscesses, these results should permit the use of a daily dose of 400 mg of fluconazole in prospective clinical studies that evaluate the effectiveness of this drug in the treatment of brain abscesses due to susceptible species of fungi.