bluuebunny/crossref_metadata_2025 huggingface dataset:
Potent Anti-Influenza Activity of Cyanovirin-N and Interactions with Viral Hemagglutinin
Authors: O'Keefe Barry R. , Smee Donald F. , Turpin Jim A. , Saucedo Carrie J. , Gustafson Kirk R. , Mori Toshiyuki , Blakeslee Dennis , Buckheit Robert , Boyd Michael R.
Published: July 2003

The novel antiviral protein cyanovirin-N (CV-N) was initially discovered based on its potent activity against the human immunodeficiency virus (HIV). Subsequent studies identified the HIV envelope glycoproteins gp120 and gp41 as molecular targets of CV-N. More recently, mechanistic studies have shown that certain high-mannose oligosaccharides (oligomannose-8 and oligomannose-9) found on the HIV envelope glycoproteins comprise the specific sites to which CV-N binds. Such selective, carbohydrate-dependent interactions may account, at least in part, for the unusual and unexpected spectrum of antiviral activity of CV-N described herein. We screened CV-N against a broad range of respiratory and enteric viruses, as well as flaviviruses and herpesviruses. CV-N was inactive against rhinoviruses, human parainfluenza virus, respiratory syncytial virus, and enteric viruses but was moderately active against some herpesvirus and hepatitis virus (bovine viral diarrhea virus) strains (50% effective concentration [EC
50
] = ∼1 μg/ml) while inactive against others. Remarkably, however, CV-N and related homologs showed highly potent antiviral activity against almost all strains of influenza A and B virus, including clinical isolates and a neuraminidase inhibitor-resistant strain (EC
50
= 0.004 to 0.04 μg/ml). When influenza virus particles were pretreated with CV-N, viral titers were lowered significantly (>1,000-fold). Further studies identified influenza virus hemagglutinin as a target for CV-N, showed that antiviral activity and hemagglutinin binding were correlated, and indicated that CV-N′s interactions with hemagglutinin involved oligosaccharides. These results further reveal new potential avenues for antiviral therapeutics and prophylaxis targeting specific oligosaccharide-comprised sites on certain enveloped viruses, including HIV, influenza virus, and possibly others.
Unique Biological Properties and Molecular Mechanism of 5,6-Bridged Quinolones
Authors: Macinga David R. , Renick Paul J. , Makin Kelly M. , Ellis David H. , Kreiner Allison A. , Li Min , Rupnik Kirk J. , Kincaid Erica M. , Wallace Cynthia D. , Ledoussal Benoit , Morris Timothy W.
Published: July 2003

We have characterized an early series of 5,6-bridged dioxinoquinolones which behaved strikingly different from typical quinolones. The 5,6-bridged dioxinoquinolones inhibited
Escherichia coli
DNA gyrase supercoiling activity but, unlike typical quinolones, failed to stimulate gyrase-dependent cleavable complex formation. Analogous unsubstituted compounds stimulated cleavable complex formation but were considerably less potent than the corresponding 5,6-bridged compounds. Consistent with a previous report (M. Antoine et al., Chim. Ther. 7:434-443, 1972) and contrary to established quinolone SAR trends, a compound with an N-1 methyl substitution (PGE-8367769) was more potent than its analog with an N-1 ethyl substitution (PGE-6596491). PGE-8367769 was shown to antagonize ciprofloxacin-mediated cleavable complex formation in a dose-dependent manner, suggesting an interaction with the gyrase-DNA complex that overlaps that of ciprofloxacin. Resistance to PGE-8367769 in
E. coli
was found to arise through missense mutations in
gyrA
, implicating DNA gyrase as the primary antibacterial target. Notably, only 1 of 15 distinct mutations selected on PGE-8367769 (D87G) has previously been implicated in quinolone resistance in
E. coli.
The remaining 14 mutations (E16V, G31V, R38L, G40A, Y50D, V70A, A84V, I89L, M135T, G173S, T180I, F217C, P218T, and F513C) have not been previously reported, and most were located outside of the traditional quinolone resistance-determining region. These novel GyrA mutations decreased sensitivity to 5,6-bridged dioxinoquinolones by four- to eightfold, whereas they did not confer resistance to other quinolones such as ciprofloxacin, clinafloxacin, or nalidixic acid. These results demonstrate that the 5,6-bridged quinolones act via a mechanism that is related to but qualitatively different from that of typical quinolones.
Correlation of Daptomycin Bactericidal Activity and Membrane Depolarization in
Staphylococcus aureus
Authors: Silverman Jared A. , Perlmutter Nancy G. , Shapiro Howard M.
Published: July 2003

The objective of this study was to further elucidate the role of membrane potential in the mechanism of action of daptomycin, a novel lipopeptide antibiotic. Membrane depolarization was measured by both fluorimetric and flow cytometric assays. Adding daptomycin (5 μg/ml) to
Staphylococcus aureus
gradually dissipated membrane potential. In both assays, cell viability was reduced by >99% and membrane potential was reduced by >90% within 30 min of adding daptomycin. Cell viability decreased in parallel with changes in membrane potential, demonstrating a temporal correlation between bactericidal activity and membrane depolarization. Decreases in viability and potential also showed a dose-dependent correlation. Depolarization is indicative of ion movement across the cytoplasmic membrane. Fluorescent probes were used to demonstrate Ca
2+
-dependent, daptomycin-triggered potassium release from
S. aureus
. Potassium release was also correlated with bactericidal activity. This study demonstrates a clear correlation between dissipation of membrane potential and the bactericidal activity of daptomycin. A multistep model for daptomycin's mechanism of action is proposed.
Subinhibitory Concentrations of the Deformylase Inhibitor Actinonin Increase Bacterial Release of Neutrophil-Activating Peptides: a New Approach to Antimicrobial Chemotherapy
Authors: Fu Huamei , Dahlgren Claes , Bylund Johan
Published: July 2003

Bacterial protein synthesis starts with a formylated methionine residue, and this residue is sequentially cleaved away by a unique peptide deformylase (PDF) and a methionine aminopeptidase to generate mature proteins. The formylation-deformylation of proteins is a unique hallmark of bacterial metabolism and has recently become an attractive target for the development of antimicrobial agents. The innate immune system uses the formylation of bacterial proteins as a target, and professional phagocytes, e.g., neutrophils, express specific receptors for bacterium-derived formylated peptides. Activation of formyl peptide receptors (FPR) mediates neutrophil migration and the release of oxygen radicals and other antimicrobial substances from these cells. We hypothesize that the use of a PDF inhibitor would increase the production of proinflammatory peptides from the bacteria and thus trigger a more pronounced innate immune response. We tested this hypothesis by exposing
Escherichia coli
to subinhibitory doses of the PDF inhibitor actinonin and show that actinonin indeed increases the production and secretion of neutrophil-activating peptides that activate human neutrophils through FPR. These findings could be potentially used as a new approach to antibacterial chemotherapy.
Haemophilus influenzae bla
ROB-1
Mutations in Hypermutagenic Δ
ampC Escherichia coli
Conferring Resistance to Cefotaxime and β-Lactamase Inhibitors and Increased Susceptibility to Cefaclor
Authors: Galán Juan-Carlos , Morosini María-Isabel , Baquero María-Rosario , Reig Milagro , Baquero Fernando
Published: July 2003

The clinical use of cefaclor has been shown to enrich
Haemophilus influenzae
populations harboring cefaclor-hydrolyzing ROB-1 β-lactamase. Such a selective process may lead to the increased use of extended-spectrum cephalosporins or β-lactams plus β-lactamase inhibitors and, eventually, resistance to these agents, which has not previously been observed in
H. influenzae
. In order to establish which
bla
ROB-1
mutations, if any, could confer resistance to extended-spectrum cephalosporins and/or to β-lactamase inhibitors, a plasmid harboring
bla
ROB-1
was transformed into hypermutagenic strain
Escherichia coli
GB20 (Δ
ampC mutS
::Tn
10
), and this construct was used in place of
H. influenzae bla
ROB-1
. Strain GB20 with the cloned gene was submitted to serial passages in tubes containing broth with increasing concentrations of selected β-lactams (cefotaxime or amoxicillin-clavulanate). Different mutations in the
bla
ROB-1
gene were obtained during the passages in the presence of the different concentrations of the selective agents. Mutants resistant to extended-spectrum cephalosporins harbored either the Leu169→Ser169 or the Arg164→Trp164 substitution or the double amino acid change Arg164→Trp164 and Ala237→Thr237. ROB-1 mutants that were resistant to β-lactams plus β-lactamase inhibitors and that harbored the Arg244→Cys244 or the Ser130→Gly130 replacement were also obtained. The cefaclor-hydrolyzing efficiencies of the ROB-1 variants were strongly decreased in all mutants, suggesting that if
bla
ROB-1
mutants were selected by cefaclor, this drug would prevent the further evolution of this β-lactamase toward molecular forms able to resist extended-spectrum cephalosporins or β-lactamase inhibitors.
MsrR, a Putative Cell Envelope-Associated Element Involved in
Staphylococcus aureus sarA
Attenuation
Authors: Rossi Jutta , Bischoff Markus , Wada Akihito , Berger-Bächi Brigitte
Published: July 2003

A novel membrane-associated protein, MsrR, was identified in
Staphylococcus aureus
which affects resistance to methicillin and teicoplanin, as well as the synthesis of virulence factors. MsrR belongs to the LytR-CpsA-Psr family of cell envelope-related transcriptional attenuators and was shown to be inducible by cell wall-active agents, such as β-lactams, glycopeptides, and lysostaphin. The expression of
msrR
peaked in the early exponential growth phase and decreased sharply thereafter.
msrR
mutants showed increased
sarA
transcription and an earlier and higher expression of RNAIII, resulting in altered expression of virulence factors such as alpha-toxin and protein A. These observations suggest that MsrR is a new component involved in
sarA
attenuation and the regulatory network controlling virulence gene expression in
S. aureus
.
Plasmid-Mediated High-Level Resistance to Aminoglycosides in
Enterobacteriaceae
Due to 16S rRNA Methylation
Authors: Galimand Marc , Courvalin Patrice , Lambert Thierry
Published: July 2003

A self-transferable plasmid of ca. 80 kb, pIP1204, conferred multiple-antibiotic resistance to
Klebsiella pneumoniae
BM4536, which was isolated from a urinary tract infection. Resistance to β-lactams was due to the
bla
TEM1
and
bla
CTX-M
genes, resistance to trimethroprim was due to the
dhfrXII
gene, resistance to sulfonamides was due to the
sul1
gene, resistance to streptomycin-spectinomycin was due to the
ant3"9
gene, and resistance to nearly all remaining aminoglycosides was due to the
aac3-II
gene and a new gene designated
armA
(aminoglycoside resistance methylase). The cloning of
armA
into a plasmid in
Escherichia coli
conferred to the new host high-level resistance to 4,6-disubstituted deoxystreptamines and fortimicin. The deduced sequence of ArmA displayed from 37 to 47% similarity to those of 16S rRNA m
7
G methyltransferases from various actinomycetes, which confer resistance to aminoglycoside-producing strains. However, the low guanine-plus-cytosine content of
armA
(30%) does not favor an actinomycete origin for the gene. It therefore appears that posttranscriptional modification of 16S rRNA can confer high-level broad-range resistance to aminoglycosides in gram-negative human pathogens.
Extended-Spectrum β-Lactamases in Ireland, Including a Novel Enzyme, TEM-102
Authors: Morris Dearbháile , O'Hare Colette , Glennon Maura , Maher Majella , Corbett-Feeney Geraldine , Cormican Martin
Published: July 2003

Organisms producing extended-spectrum β-lactamases (ESBLs) have been reported in many countries, but there is no information on the prevalence of ESBL-producing members of the family
Enterobacteriaceae
in Ireland. A total of 925 isolates of ampicillin-resistant members of the
Enterobacteriaceae
were received from six hospitals in Ireland over a 3-year period from September 1996 to September 1999. Isolates were screened for ESBL production by the double-disk diffusion (DDD) method. DDD-positive isolates that were (i) confirmed as ESBL producers by National Committee for Clinical Laboratory Standards (NCCLS) confirmatory testing and (ii) susceptible to cefoxitin by disk diffusion were considered ESBL producers. By these criteria, 27 (3%) of the ampicillin-resistant members of the
Enterobacteriaceae
studied were categorized as ESBL producers. Molecular typing suggested that some intra- and interhospital spread of ESBL-producing isolates had occurred. DNA sequencing of amplified
bla
TEM
and
bla
SHV
genes resulted in the detection of a novel
bla
TEM
ESBL gene,
bla
TEM-102
in two isolates (
Klebsiella pneumoniae
and
Enterobacter cloacae
) received from the same hospital but isolated from different patients. The study suggests dissemination of ESBL-producing bacteria within the health care system in Ireland and emphasizes the need for measures to control such spread.
TransferablevanB2Tn5382-Containing Elements in Fecal Streptococcal Strains from Veal Calves
Authors: Dahl Kristin H. , Sundsfjord Arnfinn
Published: July 2003

Three vancomycin-resistant veal calf fecal streptococci, identified asStreptococcus gallolyticus(n= 2) andStreptococcus lutetiensis, were shown to harborvanB2Tn5382-like elements earlier described in enterococci. OneS. gallolyticusstrain had a 1,495-bp IS256-related element inserted invanSB. ThevanB2Tn5382element present in the plasmid-freeS. lutetiensisstrain was transferable toEnterococcus faeciumBM4105-RF,Enterococcus faecalisJH2-2, and its recombination-deficient derivative, UV202. The transfer frequencies were comparable between recipient strains (from 1 × 10−7to 7 × 10−6). All transconjugants acquired avanB-containing chromosomal insert of approximately 100 kb, apparently by site-specific integration. Secondary transconjugants were not observed in intraspecies retransfer experiments. These observations are consistent with a conjugative, selftransmissible, integrative element that might be involved in the interspecies spread ofvanB2resistance determinants. Two JH2-2-derived transconjugants had also gained additional copies of largevanB-containing chromosomal fragments, a process that involves unexplained mechanisms that seems to require functional host cell-dependent recombination mechanisms.
Heme Binding Contributes to Antimalarial Activity of Bis-Quaternary Ammoniums
Authors: Biagini Giancarlo A. , Richier Eric , Bray Patrick G. , Calas Michèle , Vial Henri , Ward Stephen A.
Published: July 2003

Quaternary ammonium compounds have received recent attention due to their potent in vivo antimalarial activity based on their ability to inhibit de novo phosphatidylcholine synthesis. Here we show that in addition to this, heme binding significantly contributes to the antimalarial activity of these compounds. For the study, we used a recently synthesized bis-quaternary ammonium compound, T16 (1,12-dodecanemethylene bis[4-methyl-5-ethylthiazolium] diodide), which exhibits potent antimalarial activity (50% inhibitory concentration, ∼25 nM). Accumulation assays reveal that this compound is readily concentrated several hundredfold (cellular accumulation ratio, ∼500) into parasitized erythrocytes. Approximately 80% of the drug was shown to be distributed within the parasite, ∼50% of which was located in the parasite food vacuoles. T16 uptake was affected by anion substitution (permeation increasing in the order Cl
−
< Br
−
= NO
3
−
< I
−
< SCN
−
) and was sensitive to furosemide—properties similar to substrates of the induced new permeability pathway in infected erythrocytes. Scatchard plot analysis of in situ T16 binding revealed high-affinity and low-affinity binding sites. The high-affinity binding site

K
d

was similar to that measured in vitro for T16 and ferriprotoporphyrin IX (FPIX) binding. Significantly, the capacity but not the

K
d

of the high-affinity binding site was decreased by reducing the concentration of parasite FPIX. Decreasing the parasite FPIX pool also caused a marked antagonism of T16 antimalarial activity. In addition, T16 was also observed to associate with parasite hemozoin. Binding of T16 to FPIX in the digestive food vacuole is shown to be critical for drug accumulation and antimalarial activity. These data provide additional new mechanisms of antimalarial activity for this promising new class of antimalarial compounds.
Potent Inhibitors of
Plasmodium
Phospholipid Metabolism with a Broad Spectrum of In Vitro Antimalarial Activities
Authors: Ancelin Marie L. , Calas Michèle , Vidal-Sailhan Valérie , Herbuté Serge , Ringwald Pascal , Vial Henri J.
Published: July 2003

We characterized the potent in vitro antimalarial activity and biologic assessment of 13 phospholipid polar head analogs on a comparative basis. There was a positive relationship between the abilities of the drugs to inhibit parasite growth in culture and their abilities to specifically inhibit phosphatidylcholine biosynthesis of
Plasmodium falciparum
-infected erythrocytes. Maximal activity of G25 was observed for the trophozoite stage of the 48-h erythrocytic cycle (50% inhibitory concentration, 0.75 nM), whereas the schizont and ring stages were 12- and 213-fold less susceptible. The compounds exerted a rapid nonreversible cytotoxic effect, with complete clearance of parasitemia after 5 h of contact with the mature stages. The compounds were highly specific against
P. falciparum
, with much lower toxicity against three other mammalian cell lines, and the in vitro therapeutic indices ranged from 300 to 2,500,000. Finally, the monoquaternary ammonium E10 and two bis-ammonium salts, G5 and G25, were similarly active against multiresistant strains and fresh isolates of
P. falciparum
. This impressive selective in vitro toxicity against
P. falciparum
strongly highlights the clinical potential of these quaternary ammonium salts for malarial chemotherapy.
In Vivo Antimalarial Activities of Mono- and Bis Quaternary Ammonium Salts Interfering with
Plasmodium
Phospholipid Metabolism
Authors: Ancelin Marie L. , Calas Michèle , Bonhoure Anne , Herbute Serge , Vial Henri J.
Published: July 2003

We previously showed that quaternary ammonium salts have potent antimalarial activities against the blood stage of drug-resistant
Plasmodium falciparum
. In the present study, 13 compounds of this series were comparatively assessed in murine in vivo malarial models. Mice infected with
Plasmodium berghei
were successfully treated with 11 quaternary ammonium salts in a 4-day suppressive test with a once-daily intraperitoneal administration. The dose required to decrease parasitemia by 50% (ED
50
) ranged from 0.04 to 4.5 mg/kg of body weight. For six mono- and three bis-quaternary ammonium salts, the therapeutic indices (i.e., 50% lethal dose and ED
50
) were higher than 5, and at best, around 20 to 30 for five of them (E6, E8, F4, G5, and G25), which is comparable to that of chloroquine under the same conditions.
Plasmodium chabaudi
was significantly more susceptible to G5, G15, and G25 compounds than
P. berghei
. Similar therapeutic indices were obtained, regardless of the administration mode or initial parasitemia (up to 11.2%). Parasitemia clearance was complete without recrudescence. Subcutaneously administered radioactive compounds had a short elimination half-life in mice (3.5 h) with low bioavailability (17.3%), which was likely due to the permanent cationic charge of the molecule. The high in vivo therapeutic index in the
P. chabaudi
-infected mouse model and the absence of recrudescence highlight the enormous potential of these quaternary ammonium salts for clinical malarial treatment.
Activities of Mutant Prevention Concentration-Targeted Moxifloxacin and Levofloxacin against
Streptococcus pneumoniae
in an In Vitro Pharmacodynamic Model
Authors: Allen George P. , Kaatz Glenn W. , Rybak Michael J.
Published: July 2003

The differential effects of moxifloxacin and levofloxacin on the development of resistance in four
Streptococcus pneumoniae
isolates were examined by using an in vitro pharmacodynamic model. Therapeutic regimens (moxifloxacin: peak, 4.5 μg/ml; half-life [
t
1/2
], 12 h; and levofloxacin: peak, 6 μg/ml;
t
1/2
, 6 h) were tested against two fluoroquinolone-susceptible isolates (strains 79 and ATCC 49619) and KD2138 and KD2139 (
parC
and
gyrA
mutants, respectively, of ATCC 49619). Mutant prevention concentration (MPC)-targeted regimens with modified pharmacokinetics of each drug were simulated to match the area under the concentration-time curve (AUC) above the MPC for the two fluoroquinolones. Moxifloxacin MICs and MPCs (MIC/MPC) for isolates 79, ATCC 49619, KD2138, and KD2139, respectively, were 0.125 and 0.5, 0.125 and 0.5, 0.25 and 8, and 0.25 and 4 μg/ml. Levofloxacin MICs and MPCs for the same isolates were 1 and 4, 0.5 and 2, 1 and 64, and 0.5 and 32 μg/ml, respectively. Therapeutic levofloxacin concentrations led to isolation of mutants of ATCC 49619 (S79Y in ParC), KD2138 (S81Y in GyrA), and KD2139 (S79Y in ParC). Therapeutic moxifloxacin concentrations against the
gyrA
mutant KD2139 resulted in outgrowth of a mutant with a ParC substitution (S79Y) but caused no emergence of mutants of the other three isolates. MPC-targeted moxifloxacin (lower-than-normal peak = 0.75 to 1.5 μg/ml, administered at levofloxacin's
t
1/2
) caused growth of a GyrA variant (S81Y) of KD2138 and a ParC variant (S79Y) of KD2139, while no mutants of ATCC 49619 were recovered. MPC-targeted levofloxacin (higher-than-normal peak = 14.5 to 29.5 μg/ml, administered at moxifloxacin's
t
1/2
) against KD2138 and KD2139 did not prevent the development of the mutations observed in therapeutic regimens, but resistance in the fluoroquinolone-susceptible ATCC 49619 was no longer noted. Normalization of the respective AUC/MPC ratios of moxifloxacin and levofloxacin did not eliminate differences in resistance selectivity of the two agents in all cases. We conclude that the reduced recovery of resistant mutants of
S. pneumoniae
following moxifloxacin exposure compared to levofloxacin may be due to intrinsic differences between the drugs. Increasing the concentration and exposure (
t
1/2
) to exceed the MPC may prevent mutations from occurring in fluoroquinolone-susceptible strains. However, this strategy did not prevent the selection of secondary mutants in strains with preexisting mutations. Further study of the MPC concept to evaluate these relationships is warranted.
In Vitro Activities of Novel Oxapenems, Alone and in Combination with Ceftazidime, against Gram-Positive and Gram-Negative Organisms
Authors: Jamieson Conor E. , Lambert Peter A. , Simpson Iain N.
Published: July 2003

Four novel oxapenem compounds (i.e., AM-112, AM-113, AM-114, and AM-115) were investigated for their β-lactamase inhibitory activity against a panel of isolated class A, C, and D enzymes, which included expanded-spectrum β-lactamase enzymes (ESBLs). The oxapenems were potent β-lactamase inhibitors. Activity varied within the group, with AM-113 and AM-114 proving to be the most active compounds. The 50% inhibitory concentrations for these agents were up to 100,000-fold lower than that of clavulanic acid against class C and D enzymes. As a group, the oxapenems were more potent than clavulanic acid against enzymes from all classes. The ability of these compounds to protect ceftazidime from hydrolysis by β-lactamase-producing strains was evaluated by MIC tests that combined ceftazidime and each oxapenem in a 1:1 or 2:1 ratio. The oxapenems markedly reduced the MICs for ceftazidime against class C hyperproducing strains and strains producing TEM- and SHV-derived ESBLs. There was little difference between the activity of 1:1 and 2:1 combinations of ceftazidime and oxapenem. The oxapenems failed to enhance the activity of ceftazidime against derepressed AmpC-producing
Pseudomonas aeruginosa
strains.
Oral Lactoferrin Treatment of Experimental Oral Candidiasis in Mice
Authors: Takakura Natsuko , Wakabayashi Hiroyuki , Ishibashi Hiroko , Teraguchi Susumu , Tamura Yoshitaka , Yamaguchi Hideyo , Abe Shigeru
Published: July 2003

We assessed the potential of lactoferrin (LF), a multifunctional milk protein, for treatment of oral candidiasis with immunosuppressed mice, which have local symptoms characteristic of oral thrush. Oral administration of bovine LF in drinking water starting 1 day before the infection significantly reduced the number ofCandida albicansin the oral cavity and the score of lesions on the tongue on day 7 after the inoculation. The symptomatic effect of LF was confirmed by macroscopic and microscopic observations of the tongue's surface. Similar effects were also observed upon administration of LF pepsin hydrolysate, but not lactoferricin B, an antimicrobial peptide of LF. The anticandidal activity of LF was evident on administration either in drinking water or by intragastric intubation with a stomach tube. These results suggest that the effect of LF in this oral candidiasis model is not due to direct antifungal action. In conclusion, LF could have potential as a food component supporting antifungal drug treatment.
Entecavir Therapy Combined with DNA Vaccination for Persistent Duck Hepatitis B Virus Infection
Authors: Foster Wendy K. , Miller Darren S. , Marion Patricia L. , Colonno Richard J. , Kotlarski Ieva , Jilbert Allison R.
Published: July 2003

This study was designed to test the efficacy of antiviral treatment with entecavir (ETV) in combination with DNA vaccines expressing duck hepatitis B virus (DHBV) antigens as a therapy for persistent DHBV infection in ducks. Ducks were inoculated with 10
9
DHBV genomes at 7 days of age, leading to widespread infection of the liver and viremia within 7 days, and were then treated orally with either ETV (0.1 mg/kg of body weight/day) or distilled water from 21 days posthatch for 244 days. Treatment with ETV caused a 4-log drop in serum DHBV DNA levels within 80 days and a slower 2- to 3-log drop in serum DHBV surface antigen (DHBsAg) levels within 120 days. Following withdrawal of ETV, levels of serum DHBV DNA and DHBsAg rebounded to match those in the water-treated animals within 40 days. Sequential liver biopsy samples collected throughout the study showed that ETV treatment reduced DHBV DNA replicative intermediates 70-fold in the liver, while the level of the stable, template form, covalently closed circular DNA decreased only 4-fold. ETV treatment reduced both the intensity of antigen staining and the percentage of antigen-positive hepatocytes in the liver, but the intensity of antigen staining in bile duct cells appeared not to be effected. Intramuscular administration of five doses of a DNA vaccine expressing the DHBV presurface, surface, precore, and core antigens, both alone and concurrently with ETV treatment, on days 50, 64, 78, 127, and 141 did not result in any significant effect on viral markers.
In Vitro Activities of 25 Quinolones and Fluoroquinolones against Liver and Blood Stage
Plasmodium
spp
Authors: Mahmoudi Nassira , Ciceron Liliane , Franetich Jean-François , Farhati Khemais , Silvie Olivier , Eling Wijnand , Sauerwein Robert , Danis Martin , Mazier Dominique , Derouin Francis
Published: July 2003

The in vitro activities of 25 quinolones and fluoroquinolones against erythrocytic stages of
Plasmodium falciparum
and against liver stages of
Plasmodium yoelii yoelii
and
P. falciparum
were studied. All compounds were inhibitory for chloroquine-sensitive and chloroquine-resistant
P. falciparum
grown in red blood cells. This inhibitory effect increased with prolonged incubation and according to the logarithm of the drug concentration. Grepafloxacin, trovafloxacin, and ciprofloxacin were the most effective drugs, with 50% inhibitory concentrations of <10 μg/ml against both strains. Only grepafloxacin, piromidic acid, and trovafloxacin had an inhibitory effect against hepatic stages of
P. falciparum
and
P. yoelii yoelii
; this effect combined reductions of the numbers and the sizes of schizonts in treated cultures. Thus, quinolones have a potential for treatment or prevention of malaria through their unique antiparasitic effect against erythrocytic and hepatic stages of
Plasmodium
.
Comparison of Two Methods and Three End Points in Determination of In Vitro Activity of Micafungin against
Aspergillus
spp
Authors: Arikan Sevtap , Yurdakul Pınar , Hascelik Gulsen
Published: July 2003

We investigated the in vitro activity of micafungin against clinical
Aspergillus
isolates (
n
= 37) (
Aspergillusfumigatus
[
n
= 21],
Aspergillusflavus
[
n
= 14], and
Aspergillus niger
[
n
= 2]) by using NCCLS M38A microdilution and an investigational disk diffusion assay. Microdilution assay results were evaluated by using the end points of a MIC-2 (measured in micrograms per milliliter) and minimum effective concentration (MEC, measured in micrograms per milliliter; the lowest concentration of micafungin that produces short and aberrant hyphal branchings microscopically). Disk diffusion results were interpreted by measuring the zone(s) of inhibition (ZOI, measured in millimeters). Micafungin proved to be similarly active against all
Aspergillus
species tested. At 24 h, MIC-2s and MECs were identical. At 48 h, however, MIC-2s increased unpredictably, leading to the loss of a consistent correlation between the two end points. MECs and ZOI remained consistent and correlated at both reading times, suggesting their use as relevant end points in susceptibility testing of micafungin against
Aspergillus
. All
Aspergillus
isolates yielded intrazonal growth on disk diffusion agar plates. The intrazonal colonies contained short, aberrant hyphal branchings microscopically. The in vivo significance of these findings remains to be further investigated.
In Vitro Activities of Tigecycline (GAR-936) and 12 Other Antimicrobial Agents against 90
Eikenella corrodens
Clinical Isolates
Authors: Cercenado Emilia , Cercenado Sonia , Bouza Emilio
Published: July 2003

The activity of tigecycline was compared with those of other antimicrobials against 90 isolates of
Eikenella corrodens
. The MIC at which 90% of the isolates were inhibited was 2 μg/ml for tigecycline and 1, ≤0.5/0.25, 0.5, ≤0.12, ≤2, and 0.5 μg/ml for ampicillin, amoxicillin-clavulanate, cefotaxime, imipenem, chloramphenicol, and ciprofloxacin, respectively.
In Vitro Susceptibilities of SevenLeptospiraSpecies to Traditional and Newer Antibiotics
Authors: Hospenthal Duane R. , Murray Clinton K.
Published: July 2003

Human leptospirosis is generally treated with penicillin or doxycycline. We studied the susceptibilities of 11 serovars (seven species) ofLeptospirato 14 antibiotics. With the exception of chloramphenicol, all tested agents were at least as potent as penicillin and doxycycline, with the macrolide and ketolide drugs producing the lowest MICs (and minimal bactericidal concentrations).
Reduced Release of Pneumolysin by
Streptococcus pneumoniae
In Vitro and In Vivo after Treatment with Nonbacteriolytic Antibiotics in Comparison to Ceftriaxone
Authors: Spreer Annette , Kerstan Holger , Böttcher Tobias , Gerber Joachim , Siemer Alexander , Zysk Gregor , Mitchell Timothy J. , Eiffert Helmut , Nau Roland
Published: July 2003

Pneumolysin, a virulence factor of
Streptococcus pneumoniae
with cytotoxic and proinflammatory activities, occurs at concentrations from 0.85 to 180 ng/ml in cerebrospinal fluid (CSF) of meningitis patients. In pneumococcal cultures and in a rabbit meningitis model, the concentrations of pneumolysin in supernatant and CSF were lower after addition of nonbacteriolytic bactericidal antibiotics (rifampin and clindamycin) than after incubation with ceftriaxone.
Efficacy of Linezolid plus Rifampin in an Experimental Model of Methicillin-Susceptible
Staphylococcus aureus
Endocarditis
Authors: Dailey Charlene F. , Pagano Paul J. , Buchanan Lewis V. , Paquette Jennifer A. , Haas Joseph V. , Gibson John K.
Published: July 2003

The efficacy of linezolid, alone or in combination with rifampin, against methicillin-susceptible
Staphylococcus aureus
in rabbits with experimental endocarditis was investigated. Linezolid (50 or 75 mg/kg of body weight), rifampin, and linezolid (25, 50, or 75 mg/kg) plus rifampin produced statistically significant reductions in bacterial counts compared with those in untreated controls. Plasma or valvular vegetation levels of linezolid in the groups treated with the linezolid-rifampin combination were similar to those in the respective linezolid-only treatment groups. At therapeutic levels of linezolid, rifampin resistance was not observed. The results from this experimental model of endocarditis suggest that while rifampin did not provide synergy to the linezolid dosing, it did not antagonize the efficacy of linezolid.
Polymyxin B Nephrotoxicity and Efficacy against Nosocomial Infections Caused by Multiresistant Gram-Negative Bacteria
Authors: Ouderkirk John P. , Nord Jill A. , Turett Glenn S. , Kislak Jay Ward
Published: July 2003

Reported rates of nephrotoxicity associated with the systemic use of polymyxins have varied widely. The emergence of infections due to multiresistant gram-negative bacteria has necessitated the use of systemic polymyxin B once again for the treatment of such infections. We retrospectively investigated the rate of nephrotoxicity in patients receiving polymyxin B parenterally for the treatment of infections caused by multiresistant gram-negative bacteria from October 1999 to September 2000. Demographic and clinical information was obtained for 60 patients. Outcome measures of interest were renal toxicity and clinical and microbiologic efficacy. Renal failure developed in 14% of the patients, all of whom had normal baseline renal function. Development of renal failure was independent of the daily and cumulative doses of polymyxin B and the length of treatment but was significantly associated with older age (76 versus 59 years,
P
= 0.02). The overall mortality was 20%, but it increased to 57% in those who developed renal failure. The organism was cleared in 88% of the patients from whom repeat specimens were obtained. The use of polymyxin B to treat multiresistant gram-negative infections was highly effective and associated with a lower rate of nephrotoxicity than previously described.
Efficacy of Single-Dose Azithromycin in Treatment of Acute Otitis Media in Children after a Baseline Tympanocentesis
Authors: Dunne Michael W. , Khurana Chandra , Mohs Adriano Arguedas , Rodriguez Adib , Arrieta Antonio , McLinn Samuel , Krogstad Judy A. , Blatter Mark , Schwartz Richard , Vargas Sergio L. , Emparanza Paz , Fernandez Pilar , Gooch Willis M. , Aspin Mary , Podgore John , Roine Irmeli , Blumer Jeffrey L. , Ehrlich Garth D. , Chow Jean
Published: July 2003

Children with acute otitis media underwent tympanocentesis and were given a single dose of 30 mg of azithromycin/kg of body weight. At day 28, the overall clinical cure rate was 206 of 242 (85%). Clinical cure rates for patients infected with
Streptococcus pneumoniae
(67 of 76; 88%) and
Haemophilus influenzae
(28 of 44; 64%) were consistent with historical rates for the 5-day dosing regimen.
α-Defensin 1 (Human Neutrophil Protein 1) as an Antichemotactic Agent for Human Polymorphonuclear Leukocytes
Authors: Grutkoski P. S. , Graeber C. T. , Lim Y. P. , Ayala A. , Simms H. H.
Published: July 2003

Medium conditioned by tumor necrosis factor alpha (TNF-α)-stimulated polymorphonuclear leukocytes (PMN) (CM-TNF) suppresses PMN migration. Therefore, we wished to identify the agent(s) in CM-TNF that mediated antichemotactic activity. CM-TNF was fractionated by high-performance liquid chromatography, and one fraction with antichemotactic activity contained the bactericidal protein human neutrophil protein 1 (HNP-1). We showed that HNP-1 suppresses PMN migration to formyl-methionyl-leucyl-phenylalanine but not to interleukin 8.
Molecular and Biochemical Characterization of a Novel Class A β-Lactamase (HER-1) from
Escherichia hermannii
Authors: Beauchef-Havard Anne , Arlet Guillaume , Gautier Valerie , Labia Roger , Grimont Patrick , Philippon Alain
Published: July 2003

Escherichia hermannii
showed a low level of resistance to amoxicillin and ticarcillin, reversed by clavulanate, and a moderate susceptibility to piperacillin but was susceptible to all cephalosporins. A
bla
gene was cloned and encoded a typical class A β-lactamase (HER-1, pI 7.5), which shares 45, 44, 41, and 40% amino acid identity with other β-lactamases, AER-1 from
Aeromonas hydrophila
, MAL-1/Cko-1 from
Citrobacter koseri
, and TEM-1 and LEN-1, respectively. No
ampR
gene was detected. Only penicillins were efficiently hydrolyzed, and no hydrolysis was observed for cefuroxime and broad-spectrum cephalosporins. Sequencing of the
bla
gene in 12 other strains showed 98 to 100% identity with
bla
HER-1
.
Dinucleotide Analogues as Novel Inhibitors of RNA-Dependent RNA Polymerase of Hepatitis C Virus
Authors: Zhong Weidong , An Haoyun , Barawkar Dinesh , Hong Zhi
Published: July 2003

Replication of hepatitis C virus (HCV) RNA is catalyzed by the virally encoded RNA-dependent RNA polymerase NS5B. It is believed that the viral polymerase utilizes a de novo or primer-independent mechanism for initiation of RNA synthesis. Our previous work has shown that dinucleotides were efficient initiation molecules for NS5B in vitro (W. Zhong, E. Ferrari, C. A. Lesburg, D. Maag, S. K. Ghosh, C. E. Cameron, J. Y. Lau, and Z. Hong, J. Virol.
74:
9134-9143, 2000). In this study, we further demonstrated that dinucleotide analogues could serve as inhibitors of de novo initiation of RNA synthesis directed by HCV NS5B. Both mononucleotide- and dinucleotide-initiated RNA syntheses were affected by dinucleotide analogues. The presence of the 5′-phosphate group in the dinucleotide compounds was required for efficient inhibition of de novo initiation. Optimal inhibitory activity also appeared to be dependent on the base-pairing potential between the compounds and the template terminal bases. Because the initiation process is a rate-limiting step in viral RNA replication, inhibitors that interfere with the initiation process will have advantages in suppressing virus replication. The use of dinucleotide analogues as inhibitor molecules to target viral replication initiation represents a novel approach to antiviral interference.
In Vitro Bactericidal Activities of Daptomycin against
Staphylococcus aureus
and
Enterococcus faecalis
Are Not Mediated by Inhibition of Lipoteichoic Acid Biosynthesis
Authors: Laganas Valerie , Alder Jeffrey , Silverman Jared A.
Published: July 2003

Previous studies have suggested that lipoteichoic acid biosynthesis inhibition is the mechanism of action of daptomycin. In this investigation, daptomycin inhibited all macromolecular synthesis in
Staphylococcus aureus
,
Enterococcus faecalis
, and
Enterococcus hirae
without kinetic or dose specificity for lipoteichoic acid. Daptomycin remained bactericidal in the absence of ongoing lipoteichoic acid synthesis. Inhibition of lipoteichoic acid synthesis is apparently not the mechanism of action of daptomycin in these pathogens.
Thiosemicarbazole (Thiacetazone-Like) Compound with Activity against
Mycobacterium avium
in Mice
Authors: Bermudez Luiz E. , Reynolds Robert , Kolonoski Peter , Aralar Pricilla , Inderlied Clark B. , Young Lowell S.
Published: July 2003

In vitro screening of thiacetazone derivatives indicated that two derivatives, SRI-286 and SRI-224, inhibited a panel of 25
Mycobacterium avium
complex (MAC) isolates at concentrations of 2 μg/ml or lower. In mice, SRI-224 and thiacetazone had no significant activity against the MAC in livers and spleens, but treatment with SRI-286 resulted in significant reduction of bacterial loads in livers and spleens. A combination of SRI-286 and moxifloxacin was significantly more active than single drug regimens in liver and spleen.
Bovine Lactoferrin Inhibits Adenovirus Infection by Interacting with Viral Structural Polypeptides
Authors: Pietrantoni Agostina , Di Biase Assunta Maria , Tinari Antonella , Marchetti Magda , Valenti Piera , Seganti Lucilla , Superti Fabiana
Published: July 2003

We recently demonstrated that lactoferrin, an antimicrobial glycoprotein, can inhibit adenovirus infection by competing for common glycosaminoglycan receptors. This study further characterizes the antiadenovirus activity of the protein, thus demonstrating that lactoferrin neutralizes infection by binding to adenovirus particles and that its targets are viral III and IIIa structural polypeptides.
Fluoroquinolone-Resistant
Streptococcus pneumoniae
in Spain: Activities of Garenoxacin against Clinical Isolates Including Strains with Altered Topoisomerases
Authors: Morosini María-Isabel , Loza Elena , del Campo Rosa , Almaraz Felisa , Baquero Fernando , Cantón Rafael
Published: July 2003

The activity of garenoxacin was assessed against 412
Streptococcus pneumoniae
isolates (49.3% from the adult population). Overall penicillin, erythromycin, and ciprofloxacin (MIC, ≥4 μg/ml) resistance was 51.7, 35.4, and 1.5%, respectively. For all isolates, the garenoxacin MIC was ≤1 μg/ml. Amino acid replacements in GryA (Ser81→Phe or Tyr), ParC (Ser79→Phe or Tyr; Asp83→Gly; Lys137→Asn), and ParE (Ile460→Val; Asp435→Asn), alone or in combination, were ascribed to the reduced garenoxacin susceptibility (MIC range, 0.5 to 1 μg/ml) found in four isolates. The low impact of these mutations on garenoxacin activity envisages the possible coverage of
S. pneumoniae
populations resistant to preexisting quinolones.
Quinupristin-Dalfopristin Resistance in
Streptococcus pneumoniae
: Novel L22 Ribosomal Protein Mutation in Two Clinical Isolates from the SENTRY Antimicrobial Surveillance Program
Authors: Jones Ronald N. , Farrell David J. , Morrissey Ian
Published: July 2003

Resistance to quinupristin-dalfopristin (Q/D) among gram-positive cocci has been very uncommon. Two clinical isolates among 8,837 (0.02%)
Streptococcus pneumoniae
isolates were discovered in 2001 to 2002 with Q/D MICs of 4 μg/ml. Each had a 5-amino-acid tandem duplication (RTAHI) in the L22 ribosomal protein gene (
rplV
) preventing synergistic ribosomal binding of the streptogramin combination. Similar gene duplication has been reported in Q/D-resistant
Staphylococcus aureus
.
Antimicrobial Susceptibility and Macrolide Resistance Inducibility of
Streptococcus pneumoniae
Carrying
erm
(A),
erm
(B), or
mef
(A)
Authors: Syrogiannopoulos George A. , Grivea Ioanna N. , Ednie Lois M. , Bozdogan Bülent , Katopodis George D. , Beratis Nicholas G. , Davies Todd A. , Appelbaum Peter C.
Published: July 2003

Erythromycin-resistant
Streptococcus pneumoniae
isolates from young carriers were tested for their antimicrobial susceptibility; additionally, inducibility of macrolide and clindamycin resistance was investigated in pneumococci carrying
erm
(A),
erm
(B), or
mef
(A). Of 125 strains tested, 101 (81%) were multidrug resistant. Different levels of induction were observed with erythromycin, miocamycin, and clindamycin in
erm
(B) strains; however, in
erm
(A) strains only erythromycin was an inducer. Induction did not affect macrolide MICs in
mef
(A) strains.
In Vitro Activities of Florfenicol against Bovine and Porcine Respiratory Tract Pathogens
Authors: Priebe Saskia , Schwarz Stefan
Published: July 2003

Florfenicol in vitro activities for a total of 756 bacterial isolates from respiratory tract infections of cattle and swine were comparatively investigated by the agar diffusion method and the microdilution broth method. Florfenicol showed high in vitro activity against
Pasteurella multocida
,
Mannheimia haemolytica
,
Actinobacillus pleuropneumoniae
, and
Streptococcus suis
, with all of the isolates inhibited by ≤2 μg of florfenicol per ml.
In Vivo Efficacy of the Ketolide ABT-773 (Cethromycin) against Enterococci in a Mouse Peritonitis Model
Authors: Pai Suresh R. , Singh Kavindra V. , Murray Barbara E.
Published: July 2003

Using six
Enterococcus faecalis
and five
Enterococcus faecium
strains, the ketolide ABT-773 (ABT), now known as cethromycin, was found to have in vivo efficacy against both erythromycin (ERY)-susceptible (Ery
s
) and -intermediate (Ery
i
) enterococci (ABT 50% protective doses [PD
50
s], 0.5 to 4.1 and 10.3 to 16.2 mg/kg of body weight, respectively). Against four highly Ery-resistant (Ery
r
) strains for which ABT MICs were low, ABT showed much greater activity (PD
50
, 6.3 to 32.5 mg/kg) than ERY (PD
50
, >200 mg/kg) but was not protective for strains for which ABT MICs were high. In conclusion, ABT-773 showed in vivo efficacy and considerably greater activity than ERY in a mouse peritonitis model.
Survival, Replication, and Antibody Susceptibility ofEhrlichia chaffeensisoutside of Host Cells
Authors: Li Julia Shu-yi , Winslow Gary M.
Published: July 2003

Ehrlichia chaffeensis, an obligate intracellular, tick-transmitted bacterium, is susceptible to antibody-mediated host defense, but the mechanism by which this occurs is not understood. One possible explanation is that antibodies directly access the bacteria in the extracellular environment of the host, perhaps during bacterial intercellular transfer. Accordingly, we investigated whether bacteria could be found outside of host cells during infection. Host cell-free plasma obtained from infected mice was found to contain ehrlichiae, and the host cell-free ehrlichiae readily transferred disease to susceptible SCID recipients. The host cell-free ehrlichiae were found during infection of both immunocompetent BALB/c and immunocompromised BALB/c-scidmice and reached levels as high as 108/ml in plasma during persistent infection in SCID mice. Approximately 10% of the blood-borne bacteria were found outside of host cells. Although it is generally accepted that replication of ehrlichiae occurs only within host cells, the cell-free bacteria were shown to undergo DNA replication and cell division in vitro for 3 to 5 days when incubated at 37°C in plasma. Paradoxically, both infectivity and virulence were lost after 24 h of ex vivo culture. The data indicate thatE. chaffeensisis exposed to the extracellular milieu during infection, presumably during intercellular transfer, and reveal that these intracellular bacteria do not require the environment of the host cell for replication. Our findings reveal a possible mechanism by which antibodies can access the intracellular bacteria upon their release into the extracellular milieu and mediate host defense and also have implications for understanding the replication and transmission of this vector-borne pathogen.