bluuebunny/crossref_metadata_2025 huggingface dataset:
Teicoplanin and daptomycin bactericidal activities in the presence of albumin or serum under controlled conditions of pH and ionized calcium
Authors: Lamp K C , Rybak M J
Published: June 2012

Teicoplanin and daptomycin bactericidal rates (BRs) were measured from standard kill curves in supplemented Mueller-Hinton broth (B), B with 3 g of albumin per dl (BA), B with 50% pooled human serum (BS), and in broth to simulate free concentrations (BF) under controlled physiologic conditions of pH (7.4) and ionized calcium (1.15 to 1.17 mM) against two clinical Staphylococcus aureus strains. Total concentrations of teicoplanin and daptomycin, respectively, were 45 and 12.5 micrograms/ml in B, BA, and BS and 4.5 and 1.25 micrograms/ml in BF. All BRs are reported as log10 CFU per milliliter per hour. There was a trend for the teicoplanin BR to be inhibited by serum for strain 67 (BR in B was -0.26 +/- 0.08 versus a BR in BS of -0.19 +/- 0.08 [P > 0.05]). The teicoplanin BRs for strain 135 were unaffected by the type of medium used (range, -0.17 to -0.20). For both strains, daptomycin BRs were adversely affected by lower concentrations, albumin, and serum. The BR of daptomycin was significantly faster in B (-4.53 +/- 1.92) (P < 0.05) than it was in BF (-0.58 +/- 0.04), BA (-1.68 +/- 0.28), or BS (-1.02 +/- 0.16) against strain 67. BA and BS resulted in BRs more than twice that in BF (P > 0.05). Against strain 135, daptomycin again produced the highest BR in B; however, the BRs in BF, BA, and BS were almost identical, indicating that only free daptomycin was active. After correcting for the influence of protein binding, pH, and ionized calcium, teicoplanin appeared to be inhibited by serum, and daptomycin demonstrated enhanced BRs against different S. aureus strains in the presence of albumin or serum.
Susceptibility of Staphylococcus aureus growing on fibronectin-coated surfaces to bactericidal antibiotics
Authors: Chuard C , Vaudaux P , Waldvogel F A , Lew D P
Published: June 2012

Several recent studies have shown that bacteria either grown in vitro as adherent biofilms or recovered from infected prosthetic devices have decreased susceptibilities to antimicrobial killing. To further study the microbial and environmental factors responsible for this decreased antibiotic susceptibility, we developed an in vitro model of surface-adherent Staphylococcus aureus growing on polymethylmethacrylate coverslips coated with pure fibronectin. After exponential growth for 4 h, the population of fibronectin-attached S. aureus remained constant for a further 48-h period, as evaluated by CFU counts of organisms quantitatively removed from the coverslips. At selected time points, surface-bound organisms were exposed to bactericidal concentrations of either oxacillin, vancomycin, fleroxacin, or gentamicin in short-term (0.5 to 2 h) or long-term (24 h) killing assays. Whereas at 2 h surface-growing organisms were still optimally killed by all antimicrobial agents, at 4 and 24 h attached bacteria expressed markedly altered susceptibilities to these agents. The decrease in susceptibility was moderate for fleroxacin, more important for oxacillin and vancomycin, and extensive for gentamicin. When surface-attached S. aureus was compared with bacteria grown in a fluid phase, both populations showed a parallel time-dependent decrease in their susceptibilities to either oxacillin, vancomycin, or fleroxacin. In contrast, attached organisms became considerably more resistance to gentamicin than suspended bacteria did. Subpopulations of organisms spontaneously released from coverslips during antibiotic exposure also showed markedly reduced susceptibilities to antimicrobial killing. This simple model of S. aureus colonization of in vitro fibronectin-coated surfaces might represent a useful approach to the study of the physiological and biochemical changes that underlie the decreased antibiotic susceptibilities of biomaterial-attached organisms.
Antimicrobial susceptibility of Acinetobacter species
Authors: Seifert H , Baginski R , Schulze A , Pulverer G
Published: June 2012

The in vitro activities of 16 antimicrobial agents against 180 Acinetobacter strains isolated from blood cultures (n = 162), central venous catheters (n = 11), and cerebrospinal fluids (n = 7) were studied. MICs were determined by a microtiter broth dilution method. Considerable differences in antimicrobial drug susceptibility against strains belonging to different species could be demonstrated. Acinetobacter baumannii isolates (n = 108) were generally more resistant than isolates identified as species other than A. baumannii. Multidrug resistance was common among A. baumannii isolates. Of the antimicrobial agents tested, imipenem was highly active against all A. baumannii isolates, and the other agents tested were only moderately active or inactive. Good activity against Acinetobacter species strain 3 was demonstrated for imipenem, amikacin, and ciprofloxacin. Most of the strains belonging to other species were susceptible to imipenem, ciprofloxacin, expanded-spectrum cephalosporins, amoxicillin-clavulanate, and the aminoglycosides but were resistant to ampicillin and older cephalosporins.
Antimicrobial susceptibility of Pediococcus spp. and genetic basis of macrolide resistance in Pediococcus acidilactici HM3020
Authors: Tankovic J , Leclercq R , Duval J
Published: June 2012

We determined the MICs of 28 antimicrobial agents against 36 clinical strains of Pediococcus spp. (25 P. acidilactici, 9 P. pentosaceus, and 2 P. urinaeequi strains). Penicillin G, imipenem, gentamicin, netilmicin, erythromycin, clindamycin, rifampin, chloramphenicol, daptomycin, and ramoplanin were the most active. All strains of P. acidilactici were susceptible to novobiocin, whereas all isolates of P. pentosaceus were resistant. Novobiocin could therefore be helpful for differentiation of these two closely related species. P. acidilactici HM3020 was inducibly resistant to macrolide, lincosamide, and streptogramin B-type (MLS) antibiotics. Resistance was due to a determinant homologous to ermAM and carried by a nontransferable 46-kb plasmid, pVM20. This plasmid was structurally distinct from two enterococcal MLS resistance plasmids, pIP819 and pAM beta 1. The 34 strains of P. acidilactici and P. pentosaceus were resistant to tetracycline, and total DNA of these strains did not hybridize to probes specific for tetK, tetL, tetM, and tetO.
In vitro and in vivo antichlamydial activities of newly developed quinolone antimicrobial agents
Authors: Kimura M , Kishimoto T , Niki Y , Soejima R
Published: June 2012

The in vitro and in vivo activities of three newly developed quinolone antimicrobial agents (sparfloxacin, tosufloxacin, and OPC-17116) were investigated. All three agents showed potent in vitro activities against Chlamydia psittaci, C. trachomatis, and C. pneumoniae with MICs that ranged from 0.031 to 0.125 micrograms/ml. These values were higher than those of minocycline (0.0075 to 0.015 micrograms/ml) but lower than those of erythromycin (0.25 to 0.5 micrograms/ml) and ofloxacin and ciprofloxacin (0.5 to 1.0 micrograms/ml). Mice were challenged with 10(5) inclusion-forming units of C. psittaci each by nasal instillation. All untreated control animals died within 7 days. The survival rates of mice treated with 40 mg of sparfloxacin, OPC-17116, or tosufloxacin per kg of body weight every 12 h for 7 days were 73, 73, and 60%, respectively, 7 days after the challenge. The survival rate of mice treated with ofloxacin at the same dosage was 53%. On the basis of the above results, we concluded that these three new quinolones might be useful in the treatment of chlamydial respiratory infections.
Mechanism of action of quinolones against Escherichia coli DNA gyrase
Authors: Yoshida H , Nakamura M , Bogaki M , Ito H , Kojima T , Hattori H , Nakamura S
Published: June 2012

The mechanism of action of quinolones was investigated by use of various DNA gyrases reconstituted from wild-type and mutant GyrA and GyrB proteins of Escherichia coli. The quinolone sensitivities of the DNA supercoiling activity of the gyrases were generally parallel to the quinolone susceptibilities of strains having the corresponding enzymes and depended on gyrase subunits but not on substrate DNA. [3H]Enoxacin did not bind to gyrase alone or DNA alone but bound to gyrase-DNA complexes when measured by a gel filtration method. There appeared to be two enoxacin binding phases, at low and high enoxacin concentrations, for the wild-type gyrase-DNA and type 2 GyrB (Lys-447 to Glu) mutant gyrase-DNA complexes but only one enoxacin binding phase at the concentrations used for the GyrA (Ser-83 to Leu) mutant gyrase-DNA and type 1 GyrB (Asp-426 to Asn) mutant gyrase-DNA complexes. New enoxacin binding sites appeared in the presence of enoxacin, and the enoxacin binding affinities for the sites, especially at low enoxacin concentrations, near the MICs for the strains having the corresponding gyrases, correlated well with the enoxacin sensitivities of the gyrases and the MICs. From the results obtained, we propose a quinolone pocket model as the mechanism of action of quinolones, in which quinolones exert their action through binding to a gyrase-DNA complex and the quinolone binding affinities for the complex are determined by both GyrA and GyrB subunits in concert.
2-substituted quinoline alkaloids as potential antileishmanial drugs
Authors: Fournet A , Barrios A A , Muñoz V , Hocquemiller R , Cavé A , Bruneton J
Published: June 2012

Ten 2-substituted quinoline alkaloids isolated from a plant used for treatment of New World cutaneous leishmaniasis have antileishmanial in vitro activities against the extracellular forms of Leishmania spp. BALB/c mice infected with Leishmania amazonensis PH8 or H-142 or Leishmania venezuelensis were treated 1 day after the parasitic infection with a quinoline alkaloid (100 mg/kg of body weight per day) or with reference drug N-methylglucamine antimonate (Glucantime) (56 mg of pentavalent antimony [Sbv] per kg per day) for 14 days. Lesion development was the criterium used to assess disease severity. Two three-carbon chain quinolines [2-n-propylquinoline and 2-(1',2'-trans-epoxypropyl)quinoline (chimanine D)] were more potent than N-methylglucamine antimonate against L. amazonensis PH8, and five quinoline alkaloids [2-(3,4-methylenedioxyphenylethyl)quinoline, cusparine, 2-(3,4-dimethoxyphenylethyl)quinoline, 2-(E)-prop-1'-enylquinoline (chimanine B), and skimmianine] were as effective as the reference drug. Single treatment near the site of infection, 14 days after infection with L. amazonensis, with 2-n-propylquinoline or chimanine B reduced the severity of lesions but less notably than N-methylglucamine antimonate. 2-n-Propylquinoline exhibited significant activity against the virulent strain L. venezuelensis. The active products did not show any apparent toxicities during the experiment. This study is, to our knowledge, the first to show the activity of 2-substituted quinoline alkaloids for experimental treatment of New World cutaneous leishmaniasis. Further investigations of these compounds might yet prove helpful for the development of new antileishmanial drugs.
Characterization of human immunodeficiency viruses resistant to oxathiolane-cytosine nucleosides
Authors: Schinazi R F , Lloyd R M , Nguyen M H , Cannon D L , McMillan A , Ilksoy N , Chu C K , Liotta D C , Bazmi H Z , Mellors J W
Published: June 2012

The (-) enantiomers of 2',3'-dideoxy-5-fluoro-3'-thiacytidine [(-)-FTC] and 2',3'-dideoxy-3'-thiacytidine [(-)-BCH-189] were recently shown to inhibit selectively human immunodeficiency viruses (HIV) and hepatitis B virus in vitro. In the current study, the potential for HIV type 1 (HIV-1) resistance to these compounds was evaluated by serial passage of the virus in human peripheral blood mononuclear cells and MT-2 cells in the presence of increasing drug concentrations. Highly drug-resistant HIV-1 variants dominated the replicating virus population after two or more cycles of infection. The resistant variants were cross-resistant to (-)-FTC, (-)-BCH-189, and their (+) congeners but remained susceptible to 2',3'-dideoxycytidine, 3'-azido-3'-deoxythymidine, 3'-fluoro-3'-deoxythymidine, 2',3'-dideoxyinosine, phosphonoformate, the TIBO compound R82150, and the bis(heteroaryl)piperazine derivative U-87201E. Reverse transcriptase derived from drug-resistant viral particles was 15- to 50-fold less susceptible to the 5'-triphosphates of FTC and BCH-189 compared with enzyme from parental drug-susceptible virus. DNA sequence analysis of the reverse transcriptase gene amplified from resistant viruses consistently identified mutations at codon 184 from Met (ATG) to Val (GTG or GTA) or Ile (ATA). Sequence analysis of amplified reverse transcriptase from a patient who had received (-)-BCH-189 therapy for 4 months demonstrated a mixture of the Met-184-to-Val (GTG) mutation and the parental genotype, indicating that the Met-184 mutation can occur in vivo.
Antimicrobial activity and disk diffusion susceptibility testing of Ro 40-6890, the active metabolite of the new cephalosporin ester, Ro 41-3399
Authors: Pfaller M A , Barry A L , Fuchs P C
Published: June 2012

Ro 40-6890, the active metabolite of Ro 41-3399, was tested against 391 gram-negative and gram-positive clinical isolates. Ro 40-6890 was active against members of the family Enterobacteriaceae, Moraxella catarrhalis, pneumococci, other Streptococcus spp., and methicillin-susceptible staphylococci. Preliminary disk diffusion interpretive zone criteria were calculated for 5-, 10-, and 30-micrograms Ro 40-6890 disks and several possible MIC susceptibility breakpoints. We recommend the use of the 5-micrograms disk and suggest that the following zone diameters be used as breakpoints in clinical trials: susceptible, > or = 21 mm (MIC, < or = 1 microgram/ml); intermediate, 18 to 20 mm (MIC, 2 micrograms/ml); and resistant, < or = 17 mm (MIC, > or = 4 micrograms/ml).
Antimicrobial effects of a new carboxyquinolone drug, Q-35, on five serogroups of Leptospira interrogans
Authors: Takashima I , Ngoma M , Hashimoto N
Published: June 2012

New carboxyquinolone drugs, including the recently developed Q-35, were evaluated for their in vitro potency against five serogroups of Leptospira interrogans. Q-35, ofloxacin, ciprofloxacin, and tosufloxacin showed MICs (0.05 to 0.20 microgram/ml) comparable to those of tetracycline. However, MBCs of these drugs varied between 10- and 100-fold above the MIC for most strains tested. Q-35 was shown to be active against L. interrogans in vitro as judged by the MICs obtained.
In vitro susceptibilities of tropical strains of Aeromonas species from Queensland, Australia, to 22 antimicrobial agents
Authors: Koehler J M , Ashdown L R
Published: June 2012

Greater than 90% of 131 strains of Aeromonas species were susceptible to the aminoglycosides, ureidopenicillins, extended-spectrum cephalosporins, aztreonam, quinolones, tetracycline, and chloramphenicol, and all were uniformly resistant to ampicillin. Except for amoxicillin-clavulanate, sulfonamide, trimethoprim, and trimethoprim-sulfamethoxazole, there was good correlation between the results obtained by the agar dilution and disk diffusion techniques.
Comparative pharmacokinetics of diminazene in noninfected Boran (Bos indicus) cattle and Boran cattle infected with Trypanosoma congolense
Authors: Mamman M , Aliu Y O , Peregrine A S
Published: June 2012

The pharmacokinetics of diminazene in five female Boran (Bos indicus) cattle before and then during acute and chronic phases of experimental infections with Trypanosoma congolense were investigated. A 7.0% (wt/vol) solution of diminazene aceturate (Berenil) was used in all three phases of the study and administered as a single intramuscular dose of 3.5 mg of diminazene base per kg of body weight. There were no significant differences between the values of pharmacokinetic parameters for the noninfected cattle and the values for cattle with a chronic T. congolense infection. However, the maximum concentration of the drug in plasma during the acute phase of infection (8.25 +/- 1.72 micrograms/ml) was significantly (P < 0.01) greater than that during chronic infection (5.04 +/- 0.26 micrograms/ml) and that in the noninfected state (4.76 +/- 0.76 micrograms/ml). Similarly, the time to maximum concentration of the drug in plasma when diminazene was administered during the acute phase of infection (18.00 +/- 6.71 min) was significantly (P < 0.02) shorter than that for noninfected cattle (36.00 +/- 8.22 min) and that during chronic infection (33.75 +/- 7.50 min). The volume of distribution at steady state during acute infection (1.01 +/- 0.31 liter/kg) was significantly (P < 0.01) smaller than that in the noninfected state (1.37 +/- 0.17 liter/kg) and that in chronic infection (1.51 +/- 0.24 liter/kg). Eight hours after the drug had been administered, the concentration-time data profiles for each of the three study phases were very similar. Mean concentrations of diminazene in plasma 48 h after administration of the drug were 0.43 +/- 0.07 microgram/ml in noninfected cattle, 0.43 +/- 0.11 microgram/ml during the acute phase of trypanosome infection, and 0.44 +/- 0.09 microgram/ml during the chronic phase of the infection. Results of the present study indicate that the area under the concentration-time curve for diminazene in trypanosome-infected cattle did not differ significantly for noninfected cattle. It, therefore, appears that the total amount of diminazene attained and maintained in the plasma of cattle is not significantly altered during infection with T. congolense.
N-n-alkyl-3,4-dihydroxybenzamides as inhibitors of the trypanosome alternative oxidase: activity in vitro and in vivo
Authors: Grady R W , Bienen E J , Dieck H A , Saric M , Clarkson A B
Published: June 2012

On the basis of our previous demonstration of the high inhibitory activity of a series of p-n-alkyloxybenzhydroxamic acids and n-alkyl esters of 3,4-dihydroxybenzoic acid against the trypanosome alternative oxidase in a cell-free mitochondrial preparation of Trypanosoma brucei brucei, we synthesized a series of N-n-alkyl-3,4-dihydroxybenzamides for evaluation as inhibitors of this enzyme. This class of compounds was selected with the expectation of their having similar inhibitory activity to but greater solubility than the esters and hydroxamic acids noted above and greater resistance to serum hydrolases in vivo. We predicted that such properties would allow an inhibitor of the trypanosome alternative oxidase to be coadministered with glycerol as a means of providing treatment for infections by African trypanosomes. As expected, such benzamides were both more soluble and more stable, some being more active against the target enzyme than the corresponding ester. One, N-n-butyl-3,4-dihydroxybenzamide, was selected for evaluation in vivo against T. brucei brucei. When combined with glycerol, this benzamide was found to be curative. A regimen wherein 450 mg of N-n-butyl-3,4-dihydroxybenzamide per kg and 15 g of glycerol per kg were given hourly in three divided doses cured 17 of 19 mice with established T. brucei brucei infections. This combination is more active in vivo than any other designed to block simultaneously both the unique respiratory electron transport system and the anaerobic glycolytic pathways of these pathogenic protozoa.
Efflux-mediated fluoroquinolone resistance in Staphylococcus aureus
Authors: Kaatz G W , Seo S M , Ruble C A
Published: June 2012

Transport processes are used by all organisms to obtain essential nutrients and to expel wastes and other potentially harmful substances from cells. Such processes are important means by which resistance to selected antimicrobial agents in bacteria is achieved. The recently described Staphylococcus aureus norA gene encodes a membrane-associated protein that mediates active efflux of fluoroquinolones from cells. SA-1199B is a fluoroquinolone-resistant strain of S. aureus from which we cloned an allele of norA (norA1199). Similar to that of norA, the protein product of norA1199 preferentially mediates efflux of hydrophilic fluoroquinolones in both S. aureus and an Escherichia coli host, a process driven by the proton motive force. Determination of the nucleotide sequence of norA1199 revealed an encoded 388-amino-acid hydrophobic polypeptide 95% homologous with the norA-encoded protein. Significant homology with other proteins involved in transport processes also exists, but especially with tetracycline efflux proteins and with the Bacillus subtilis Bmr protein that mediates active efflux of structurally unrelated compounds, including fluoroquinolones. In S. aureus, the norA1199-encoded protein also appears to function as a multidrug efflux transporter. Southern hybridization studies indicated that norA1199 (or an allele of it) is a naturally occurring S. aureus gene and that related sequences are present in the S. epidermidis genome. The nucleotide sequence of the wild-type allele of norA1199, cloned from the fluoroquinolone-susceptible parent strain of SA-1199B, did not differ from that of norA1199 throughout the coding region. Northern (RNA) and Southern hybridization studies showed that increased transcription, and not gene amplification, of norA1199 is the basis for fluoroquinolone resistance in SA-1199B.
In vitro activity of vancomycin against the spirochete Borrelia burgdorferi
Authors: Dever L L , Jorgensen J H , Barbour A G
Published: June 2012

Borrelia burgdorferi, a spirochete and the causative agent of Lyme disease, has been reported to be susceptible to a variety of antimicrobial agents. In this investigation, the action of vancomycin, a glycopeptide antibiotic not previously known to have activity against spirochetes, against borrelias was examined. The in vitro activity of vancomycin against a variety of strains of B. burgdorferi and one strain of Borrelia hermsii was determined by use of a microdilution MIC method (L.L. Dever, J.H. Jorgensen, and A.G. Barbour, J. Clin. Microbiol. 30:2692-2697, 1992). MICs ranged from 0.5 to 2 micrograms/ml. MICs of the glycopeptides ristocetin and teicoplanin and the lipopeptide daptomycin against strain B31 of B. burgdorferi were all > or = 8 micrograms/ml. Subsurface plating, time-kill studies, synergy studies, and electron microscopy were used to investigate further the activity of vancomycin against B31. The MBC of vancomycin was 2 micrograms/ml. Time-kill curves demonstrated > or = 3-log10-unit (99.9%) killing of the final inoculum after 72 h by vancomycin concentrations twice the MIC. Synergy between vancomycin and penicillin was demonstrated at concentrations one-fourth the MIC of each drug. In electron microscopy, B31 cells exposed to vancomycin showed a disruption of cellular integrity and were indistinguishable from those exposed to penicillin. These studies demonstrate another class of microorganisms susceptible in vitro to vancomycin.
Susceptibilities of beta-lactamase-positive and -negative strains of Campylobacter coli to beta-lactam agents
Authors: Lachance N , Gaudreau C , Lamothe F , Turgeon F
Published: June 2012

The percentages of susceptibility of 28 strains of Campylobacter coli to beta-lactam agents were 96% for amoxicillin and ampicillin, 57% for ticarcillin, 4% for cefoxitin and cefuroxime, 61% for cefotaxime, and 11% for ceftazidime. None of the strains were susceptible to penicillin G, piperacillin, cefazolin, cephalothin, cefamandole, and cefoperazone. All strains were susceptible to imipenem and ciprofloxacin, and 21% were susceptible to erythromycin. A beta-lactamase was detected in 68% of the strains by cefinase disks and by the nitrocefin method. The beta-lactamase-positive strains were significantly less susceptible to amoxicillin, ampicillin, and ticarcillin than the beta-lactamase-negative strains (P < or = 0.003). Clavulanic acid (0.25 microgram/ml) but not sulbactam and tazobactam (2 micrograms/ml) lowered to susceptible levels the amoxicillin and ampicillin MICs of the only strain of C. coli resistant to amoxicillin, ampicillin, and ticarcillin.
Bleomycin affects cell wall anchorage of mannoproteins in Saccharomyces cerevisiae
Authors: Beaudouin R , Lim S T , Steide J A , Powell M , McKoy J , Pramanik A J , Johnson E , Moore C W , Lipke P N
Published: June 2012

Bleomycin induces strand breakage in DNA through disruption of glycosidic linkages. We investigated the ability of bleomycin to damage yeast cell walls, which are composed primarily of carbohydrate. Bleomycin treatment of intact yeast cells facilitated enzymatic conversion of yeasts to spheroplasts. Bleomycin treatment also altered anchorage of mannoproteins to the cell wall matrix in intact cells or isolated cell walls. Cell surface mannoproteins were labelled with 125I, and their solubilization was monitored. Seventeen hour treatments with bleomycin released some of the label directly into treatment supernatants and facilitated extraction of mannoproteins by dithiothreitol and lytic enzymes. Bleomycin treatments as short as 10 min caused changes in extraction of mannoproteins from intact cells. Specifically, cell wall anchorage of several mannoproteins was affected by the drug. There were drug-induced changes in extractability of mannoproteins with apparent molecular weights of 96,000, 80,000, 61,000, 41,000, 31,500, and 21,000 (determined after deglycosylation with endo-N-acetylglucosaminidase H). The similarity of results obtained in the presence and absence of cycloheximide, the appearance of cell wall effects after only 10 min of treatment, and the similarity of effects in intact cells and isolated cell walls are consistent with direct drug-induced damage and inconsistent with a mechanism dependent on expression of bleomycin-damaged genes or other intracellular mediators. The results are consistent with bleomycin-mediated increases in cell wall permeability through disruption of glycosidic cross-linking structures in the cell wall.
Functional studies of truncated soluble intercellular adhesion molecule 1 expressed in Escherichia coli
Authors: Martin S , Martin A , Staunton D E , Springer T A
Published: June 2012

We have expressed in Escherichia coli the two N-terminal immunoglobulin (Ig)-like domains of the intercellular adhesion molecule 1 (ICAM-1). The first 188 residues of ICAM-1 were expressed with an N-terminal methionine (MP188) or as a maltose-binding fusion protein which was cleaved with factor Xa (XP188). After refolding, both MP188 and XP188 were active in binding to the leukocyte integrin lymphocyte function-associated antigen 1, which has previously been shown to bind to the N-terminal Ig domain of ICAM-1. The major group of rhinoviruses and malaria-infected erythrocytes bind to distinct sites within the first Ig-like domain of ICAM-1. Both MP188 and XP188 bound to malaria-infected erythrocytes; however, only XP188 inhibited human rhinovirus plaque formation. A product (MdQ1P188) with the initiation methionine fused to residue 2, i.e., with glutamine 1 deleted, inhibited plaque formation. MdQ1P188 was able to induce a conformational change of the virus capsid as shown by conversion of 149S particles to 85S particles, whereas MP188 had no effect. These results show that functionally active fragments of ICAM-1 can be produced in E. coli, that glycosylation is not required for ligand binding, and that the N-terminal residue of ICAM-1 is proximal to or part of the human rhinovirus-binding site.
Inactivation of rifampin by Nocardia brasiliensis
Authors: Yazawa K , Mikami Y , Maeda A , Akao M , Morisaki N , Iwasaki S
Published: June 2012

Rifampin was glycosylated by a pathogenic species of Nocardia, i.e., Nocardia brasiliensis. The structures of two glycosylated compounds (RIP-1 and RIP-2) isolated from the culture broth of the bacterium were determined to be 3-formyl-23-(O-[beta-D-glucopyranosyl])rifamycin SV and 23-(O-[beta-D-glucopyranosyl])rifampin, respectively. Both compounds lacked antimicrobial activity against other gram-positive bacteria as well as the Nocardia species.
Efficacy of clarithromycin for treatment of experimental Lyme disease in vivo
Authors: Alder J , Mitten M , Jarvis K , Gupta P , Clement J
Published: June 2012

Clarithromycin provided effective therapy against arthritis induced by Borrelia burgdorferi infection in the hamster. In vitro, clarithromycin was at least 1 log more potent than tetracycline against two isolates of B. burgdorferi from human sources, as measured by MICs and 50% inhibitory concentrations. Clarithromycin was effective in preventing the onset of B. burgdorferi-induced arthritis, as determined by several parameters of paw swelling. When administered after the onset of arthritis, clarithromycin therapy reduced the degree of swelling and decreased recovery time. These results suggest that clarithromycin has potential as an effective therapy for Lyme disease.
In vitro activity of ramoplanin against vancomycin-resistant gram-positive organisms
Authors: Collins L A , Eliopoulos G M , Wennersten C B , Ferraro M J , Moellering R C
Published: June 2012

In vitro activity of ramoplanin, a cyclic lipoglycopeptide, against 92 vancomycin-resistant gram-positive organisms was evaluated. Ramoplanin demonstrated potent activity against many highly vancomycin-resistant organisms including enterococci (MICs for 90% of strains tested of 0.5 micrograms/ml) and against Lactobacillus spp., Leuconostoc spp., and Pediococcus spp., all of which were inhibited at concentrations of < or = 0.25 micrograms/ml. This drug or a derivative compound merits further investigation as a potential therapeutic agent for infections due to vancomycin-resistant enterococci.
Efficacy of (-)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine in African green monkeys infected with simian varicella virus
Authors: Soike K F , Bohm R , Huang J L , Oberg B
Published: June 2012

(-)-9-[4-Hydroxy-2-(hydroxymethyl)butyl]guanine was evaluated for its efficacy in African green monkeys infected with simian varicella virus. Treatment by intramuscular injection was initiated 48 h after virus inoculation and was continued for 10 days; the treatment showed therapeutic effects on rash and viremia at dosages down to 1 mg/kg of body weight per day.
Comparison of spiramycin and doxycycline for treatment of Chlamydia trachomatis genital infections
Authors: Dylewski J , Clecner B , Dubois J , St-Pierre C , Murray G , Bouchard C , Phillips R
Published: June 2012

We performed a single blind controlled multicenter study in which we compared the efficacy and safety of 100 mg of doxycycline versus those of 1 g (3 x 10(6) IU) of spiramycin given orally twice daily for 14 days in the treatment of culture-positive Chlamydia trachomatis genitourinary tract infections. A total of 367 patients were enrolled in the study, and 364 patients were evaluable for safety and 265 patients were evaluable for efficacy. The cure rate between treatment groups was not statistically significant, being 98% (125 of 128 patients) in the spiramycin group and 100% (133 of 133 patients) in the doxycycline group. Female patients who received spiramycin were more likely to report dysethesias that resolved after the completion of therapy. The results of the study show that spiramycin is an effective drug for the treatment of C. trachomatis infection and warrants further assessment over a shorter treatment period (7 days) and during pregnancy.
Elimination of quinolone antibiotic carryover through use of antibiotic-removal beads
Authors: Zabinski R A , Larsson A J , Walker K J , Gilliland S S , Rotschafer J C
Published: June 2012

To prove the utility of antibiotic-removal beads in separating antibiotics from bacterial samples, Escherichia coli ATCC 25922 was exposed to five separate quinolones before and after each was exposed to antibiotic-removal beads. Plates treated with antibiotic solutions that were exposed to beads demonstrated antibiotic removal, and plates treated with antibiotic solutions that were not exposed to beads demonstrated antibiotic carryover. After exposure to beads, fluoroquinolone concentrations decreased from 5 micrograms/ml to 0.14 micrograms/ml (ciprofloxacin), 0.04 micrograms/ml (temafloxacin), < 0.01 microgram/ml (ofloxacin), < 0.01 microgram/ml (sparfloxacin), and 0.02 micrograms/ml (clinafloxacin). These data indicate that antibiotic carryover can be successfully circumvented through the use of antibiotic-removal beads.
The same mutation that encodes low-level human immunodeficiency virus type 1 resistance to 2',3'-dideoxyinosine and 2',3'-dideoxycytidine confers high-level resistance to the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine
Authors: Gao Q , Gu Z , Parniak M A , Cameron J , Cammack N , Boucher C , Wainberg M A
Published: June 2012

Variants of human immunodeficiency virus type 1 that display 500- to 1,000-fold resistance to the (-) enantiomer of 2'-deoxy-3'-thiacytidine and approximately 4- to 8-fold resistance to 2',3'-dideoxycytidine and 2',3'-dideoxyinosine have been generated through in vitro selection with the former compound. The polymerase regions of several of these resistant viruses shared a codon alteration at site 184 (ATG-->GTG; methionine-->valine), a mutation previously associated with low-level resistance to 2',3'-dideoxycytidine. The biological relevance of this mutation for the (-) enantiomer of 2'-deoxy-3'-thiacytidine was confirmed by site-directed mutagenesis with the HXB2-D clone of human immunodeficiency virus type 1.
Penicillin-binding proteins of Rhodococcus equi: potential role in resistance to imipenem
Authors: Nordmann P , Nicolas M H , Gutmann L
Published: June 2012

Rhodococcus equi is a gram-positive coccobacillus which, like other members of the order Actinomycetales, is increasingly reported as an opportunistic pathogen in patients with AIDS. The use of combinations of antibiotics that include imipenem (IMP) has been suggested for the treatment of patients infected with R. equi. An antagonism between IMP, meropenem, cefoxitin, ceftriaxone, moxalactam, and oxacillin and other beta-lactams, such as penicillin, amoxicillin, cephalothin, and ticarcillin, was detected in vitro both on Mueller-Hinton agar and in broth for all 10 IMP-susceptible R. equi strains examined. To study the mechanism of the antagonism between beta-lactams, a mutant with decreased susceptibility to IMP (isolate IpR) was selected in vitro from a susceptible clinical isolate of R. equi (isolate IpS). IpR exhibited decreased susceptibility to IMP, meropenem, cefoxitin, ceftriaxone, moxalactam, and oxacillin but not to penicillin, amoxicillin, cephalothin, or ticarcillin. No beta-lactamase was found in IpS, IpS cultured with antagonistic beta-lactams, or IpR strains. Labeling of penicillin-binding proteins (PBPs) revealed four PBPs with molecular masses of ca. 59, 56, 43, and 26 kDa in IpS. In IpR, PBP 3 disappeared and was replaced by PBP 3a of 40 kDa. The 50% saturation of PBP 3 and PBP 3a by the carbapenems correlated with the MICs of these antibiotics, respectively, for IpS and IpR strains. However, PBP 3a was not detected in IpS when IpS was cultured in the presence of beta-lactams, with which antagonism was observed. The present work describes the PBPs of R. equi and reports that IMP resistance in R. equi is related to an altered PBP pattern.
Pharmacokinetics of cefepime in cystic fibrosis patients
Authors: Huls C E , Prince R A , Seilheimer D K , Bosso J A
Published: June 2012

The purposes of this study were to determine and compare the single- and multiple-dose pharmacokinetics of cefepime in patients with and without cystic fibrosis. Twelve patients with cystic fibrosis hospitalized for treatment of acute pulmonary exacerbations were studied. In addition, pharmacokinetic data for seven of the patients with cystic fibrosis were compared with those for seven age-matched control patients. The cefepime dose was 50 mg/kg of body weight (maximum, 2 g) administered as a 30-min intravenous infusion every 8 h for a minimum of 8 days. Serial plasma and urine samples, obtained after the first and last doses, were analyzed for cefepime content by a validated high-pressure liquid chromatographic assay. By standard noncompartmental analysis, the pharmacokinetic parameters ascertained were area under the concentration in plasma-time curve, elimination half-life, total body clearance, renal clearance, and volume of distribution at steady state. In addition, the maximum concentration in plasma was recorded. Mean (+/- standard deviation) results of the first dose analysis in patients with cystic fibrosis were as follows: maximum concentration in plasma, 142.6 (+/- 26.07) micrograms/ml; area under the concentration in plasma-time curve, 265.3 (+/- 114.31) micrograms.h/ml; elimination half-life, 1.8 (+/- 0.53) h; total body clearance, 127.2 (+/- 50.94) ml/min; renal clearance, 91.1 (+/- 38.86) ml/min/kg; volume of distribution at steady state, 14.1 (+/- 4.31) liters. Analysis for the last dose in patients with cystic fibrosis did not vary appreciably from these values, nor did those from the controls. Thus, it appears that the first-dose pharmacokinetics of cefepime are predictive of those at steady state. In order to consistently exceed the MIC for Pseudomonas aeruginosa for the entire dosing interval in patients with cystic fibrosis, a higher dose and/or different dosing interval compared with those used in this study may be necessary.
Synergistic combinations of Ro 11-8958 and other dihydrofolate reductase inhibitors with sulfamethoxazole and dapsone for therapy of experimental pneumocystosis
Authors: Walzer P D , Foy J , Steele P , White M
Published: June 2012

We compared Ro 11-8958, an analog of trimethoprim (TMP) with improved antimicrobial and pharmacokinetic properties, other dihydrofolate reductase (DHFR) inhibitors, sulfamethoxazole (SMX), and dapsone (DAP) in the treatment of Pneumocystis carinii pneumonia in an immunosuppressed rat model. In contrast to previous reports, high dosages of the DHFR inhibitors were used in combination with fixed, low dosages of SMX (3 mg/kg of body weight per day) or DAP (25 mg/kg/day). When administered alone at these dosages, SMX and DAP reduced the median P. carinii cyst count about 5- to 15-fold. Ro 11-8958, TMP, and diaveridine used at a dosage of 20 mg/kg/day with SMX were only slightly more effective than SMX used alone. However, administration of these DHFR inhibitors at a dosage of 100 mg/kg/day with SMX lowered the cyst count about 500- to 1,000-fold, indicating a synergistic effect. Little or no synergism was found when other DHFR inhibitors (pyrimethamine, cycloguanil, and tetroxoprim) were combined with SMX. Regimens of Ro 11-8958 at a dosage of 20 mg/kg/day with DAP and of TMP or diaveridine used at a dosage of 100 mg/kg/day with DAP showed comparable anti-P. carinii activity, lowering the cyst count 100- to 200-fold. By contrast, Ro 11-8958 administered at a dosage of 100 mg/kg/day with DAP reduced the cyst count > 1,000-fold. Thus, the experimental approach used here enables the rat model of pneumocystosis to be used to compare synergistic combinations of antifolate drugs. The favorable results achieved with Ro 11-8958 indicate that it should be considered for clinical trials.
Activity of bilobalide, a sesquiterpene from Ginkgo biloba, on Pneumocystis carinii
Authors: Atzori C , Bruno A , Chichino G , Bombardelli E , Scaglia M , Ghione M
Published: June 2012

The sesquiterpene bilobalide, extracted from Ginkgo biloba leaves, was tested in vitro and in vivo for the ability to inhibit Pneumocystis carinii growth. Bilobalide was inhibitory to trophozoites cultured on human embryonic lung fibroblasts (HEL 299) at approximately the same concentration as trimethoprim plus sulfamethoxazole (lowest effective concentration, 50 micrograms of bilobalide per ml versus 9/45 microgram of trimethoprim-sulfamethoxazole per ml), inducing microscopically detectable morphological changes in the cytoplasm of the parasite. In pharmacologically immunosuppressed Sprague-Dawley rats transtracheally infected with a suspension of about 5 x 10(6) P. carinii trophozoites per ml, the daily intraperitoneal administration of bilobalide (10 mg/kg of body weight for 8 days) lowered the number of organisms by approximately 2 logs (that is, about 99%). There was no apparent toxicity either in uninfected HEL 299 feeder cells or in infected and uninfected animals. These studies suggest that the sesquiterpene bilobalide might be useful for therapy of and prophylaxis against P. carinii infections in humans.
Treatment of experimental visceral leishmaniasis in a T-cell-deficient host: response to amphotericin B and pentamidine
Authors: Murray H W , Hariprashad J , Fichtl R E
Published: June 2012

In experimental visceral leishmaniasis, euthymic but not athymic (nude) BALB/c mice respond to conventional treatment with pentavalent antimony, indicating that the in vivo efficacy of antimony is T cell dependent. This finding correlates with frequent antimony treatment failures for T-cell-deficient patients with visceral leishmaniasis. To determine whether the in vivo efficacies of alternative antileishmanial agents also require T cells, Leishmania donovani-infected euthymic and nude BALB/c mice were treated with pentamidine or amphotericin B. Pentamidine induced leishmanistatic activity in euthymic mice but had little effect in nude mice. In contrast, amphotericin B exerted potent leishmanicidal activities in both euthymic and nude animals. These results suggest that amphotericin B may be of particular use for T-cell-deficient patients with visceral leishmaniasis.
Effects of discontinuation of zidovudine treatment on zidovudine sensitivity of human immunodeficiency virus type 1 isolates
Authors: Boucher C A , van Leeuwen R , Kellam P , Schipper P , Tijnagel J , Lange J M , Larder B A
Published: June 2012

Zidovudine treatment of individuals infected with human immunodeficiency virus type 1 (HIV-1) results in HIV-1 isolates with a reduced zidovudine sensitivity in vitro. This reduction is due to mutations causing amino acid substitutions at five codons (41, 67, 70, 215, and 219) on the reverse transcriptase enzyme of HIV. HIV-1 isolates were obtained 8 to 69 weeks after therapy discontinuation from 10 patients at different stages of disease. Zidovudine sensitivity was determined by the HeLa CD4+ plaque assay. The presence of the resistance-conferring mutations was determined by using a selective polymerase chain reaction. Sensitivity could be determined for six isolate pairs: one showed a decline in the 50% inhibitory zidovudine concentration after therapy discontinuation; four pairs did not show a change. The majority of changes in the five codons in isolates from all 10 patients were the result of a relative increase in the wild-type sequence. Complete changes from mutant to the wild type were seen for only two codons in isolates from two patients. This study of isolates from a small group of individuals at different stages of disease, who had been taking zidovudine for 1 to 2 years, shows that a period of 1 year without zidovudine may be required to achieve a change from a mutant or mixed virus population to a wild-type virus population.
Ethambutol inhibition of glucose metabolism in mycobacteria: a possible target of the drug
Authors: Silve G , Valero-Guillen P , Quemard A , Dupont M A , Daffe M , Laneelle G
Published: June 2012

The addition of D-arabinose, D-galactose, D-glucosamine, or D-mannose to the growth medium of Mycobacterium smegmatis suppressed the inhibitory effects of ethambutol both on acetate labeling of cell wall-linked mycolic acids and on the increase in the delipidated cell dry weight. The addition of D-glucose or D-fructose had no effect. It is proposed that ethambutol inhibits an early step of glucose conversion into the monosaccharides used for the biosynthesis of structurally and biologically important cell wall polysaccharides: arabinogalactan, arabinomannan, and peptidoglycan.
Activity of topoisomerase inhibitors against Pneumocystis carinii in vitro and in an inoculated mouse model
Authors: Fishman J A , Queener S F , Roth R S , Bartlett M S
Published: June 2012

Five topoisomerase II inhibitors (amsacrine [m-AMSA], two epipodophyllotoxins, and two quinolones) and the alkaloid camptothecin (a topoisomerase I inhibitor) were evaluated to assess their activities against Pneumocystis carinii. In vitro, both etoposide (VP-16) and teniposide (VM-26) at 1 microgram/ml suppressed P. carinii growth. Amsacrine was toxic to P. carinii and to the feeder cells in vitro. Camptothecin suppressed the growth of P. carinii in vitro only at 100 micrograms/ml. Studies in immunosuppressed mice demonstrated the efficacy of teniposide against P. carinii pneumonia, but successful administration of teniposide was schedule dependent with significant toxicity at therapeutic dosages.
In vitro activity of roxithromycin against 16 species of atypical mycobacteria and effect of pH on its radiometric MICs
Authors: Rastogi N , Goh K S , Bryskier A
Published: June 2012

The antimycobacterial spectrum of roxithromycin, a semisynthetic 14-membered ring macrolide, was determined against 28 strains belonging to 16 species of atypical mycobacteria by measuring radiometric MICs by BACTEC methodology at two different pH values, i.e., 6.8 and 7.4. The MICs obtained at pH 7.4 were 1 to 2 dilutions lower or more than those obtained at pH 6.8 for some of the species. Roxithromycin possessed promising MICs against such potential pathogens as the Mycobacterium avium complex, M. scrofulaceum, M. szulgai, M. malmoense, M. xenopi, M. marinum, M. kansasii, and rare pathogens like M. chelonei subsp. chelonei and M. chelonei subsp. abscessus but not against M. simiae. Roxithromycin showed lower MICs against M. fortuitum var. peregrinum than M. fortuitum var. fortuitum.
WIN 54954 treatment of mice infected with a diabetogenic strain of group B coxsackievirus
Authors: See D M , Tilles J G
Published: June 2012

The therapeutic efficacy of an experimental antiviral agent, WIN 54954, was evaluated in a mouse model in which infection by coxsackievirus B4 (CVB4) strain E2 was followed by diabetes mellitus. Male CD1 mice (age, 5 weeks) were inoculated with 10(4) PFU of CVB4. WIN 54954 was administered orally via gavage tube in a dose of either 5 or 50 mg/kg of body weight per day. Treatment was initiated on the day of inoculation and was continued for 10 days. Control animals received the xanthan gum carrier only. At 3 days postinoculation (p.i.), the mean titer of virus in the pancreas was found to be significantly lower in both the high-dose (P < 0.001) and low-dose (P < 0.05) treatment groups compared with that in the controls. Furthermore, islet histologic abnormalities were significantly less common in the high-dose group (P < 0.02) than in the controls. At 7 weeks p.i., both fasting and 1-h postprandial glucose levels in blood were significantly lower for both the high-dose (P < 0.001) and the low-dose (P < 0.01) treatment groups than in controls. The proportion of mice with persistent viral RNA in the pancreas at this time, as detected by polymerase chain reaction, was significantly reduced in the high-dose treatment group (4 of 11 mice) compared with that in the controls (7 of 8 mice). When mice received 50 mg of WIN 54954 per kg daily beginning at either 48 or 72 h postinoculation, the titers in the pancreas were again significantly reduced at 3 days p.i. compared with those in the controls (P < 0.01 and P < 0.05, respectively). Thus, WIN 54954 effectively reduces virus replication and islet histologic changes acutely and decreases, at 7 weeks, both the metabolic alteration associated with diabetes mellitus and the incidence of detectable viral RNA in the pancreas.