bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model for the growth and reactivity of metal films on oxide surfaces: Cu on ZnO(0001̄)–O
Authors: Campbell C. T. , Ludviksson A. 
Published: July 2002

In the many studies of vapor deposition of late transition metals on single-crystal oxide surfaces, never has a low-energy electron diffraction superstructure been observed in the first layer. Although layer-by-layer behavior is often reported at ≤300 K, annealing the films generally leads to irreversible clustering into thick islands that cover a tiny part of the oxide. We discuss here a growth model that explains these general observations and is also consistent with the expected energetics for metal atom diffusion over oxide and metal terraces and up and down over the edges of metal islands. We briefly review our recent studies which led to this model, in which the structural, electronic, and chemical properties of Cu films on the oxygen-terminated ZnO(0001̄)–O surface were examined. At coverages beyond a few percent, vapor-deposited Cu adatoms become nearly neutral. Their chemical behavior indicates that they form two-dimensional (2D) islands with metal-like Cu–Cu distances, much shorter than the substrate lattice parameter. Further deposition of Cu leads to spreading of these 2D islands without forming thicker layers, until about 55% of the surface is covered. Thereafter, these Cu islands grow thicker without filling the voids between islands, except at a rate much slower than the rate at which Cu vapor strikes in these voids. Our new model shows that a large fraction of an oxide surface will first be covered by 2D islands during metal deposition at low temperatures due to a kinetic effect.
This occurs even when the metal’s adsorption energy on itself significantly exceeds its adsorption energy on the oxide (i.e., when 3D clustering is thermodynamically favored), provided the difference in these energies does not exceed the energy of 2D evaporation from island edges onto terraces. As soon as islands nucleate in the second layer, 2D spreading ceases and energetic pathways open that allow metal atoms to migrate up from the oxide terrace into this new layer. This can lead to thick, flat-topped islands. Atom-thin (2D) Cu islands on ZnO(0001̄)–O react with CO, O2, H2O, HCOOH, and CH3OH very much like Cu(110), although there are some differences: The transiently adsorbed H and CO2 products of HCOOH dissociation migrate off or under the Cu islands and interact strongly with ZnO sites, and Oa is not as good a Bro/nsted base as on Cu(110). Annealed 3D islands behave much like Cu(111). We present here new results for methyl iodide adsorption and methyl dissociation on these Cu islands which further support this general picture.
Antibody-Targeted Lethal Photosensitization ofPorphyromonas gingivalis
Authors: Bhatti M. , MacRobert A. , Henderson B. , Shepherd P. , Cridland J. , Wilson M. 
Published: July 2002

ABSTRACTWe have previously demonstrated thatPorphyromonas gingivalisis susceptible to killing by toluidine blue O (TBO) when irradiated with light from a helium-neon (HeNe) laser. The aim of this study was to determine whether a TBO-antibody conjugate (Ab-TBO) could be used to specifically targetP. gingivalisto lethal photosensitization in the presence ofStreptococcus sanguisor human gingival fibroblasts (HGFs). When a mixture ofP. gingivalisandS. sanguiswas exposed to 4 μg of TBO/ml and irradiated with HeNe laser light, there were 1.5- and 4.0-log10-unit reductions in the viable counts, respectively. In contrast, when TBO was conjugated with a murine monoclonal antibody againstP. gingivalislipopolysaccharide, the reductions in viable counts ofP. gingivalisandS. sanguisamounted to 5.0 and 0.1 log10units, respectively. Lethal photosensitization ofP. gingivalisin the presence of HGFs using unconjugated TBO resulted in a 0.7-log10-unit reduction inP. gingivalisviable counts and a 99% reduction in the incorporation of tritiated thymidine ([3H]Tdr) by the HGFs. In contrast, when the Ab-TBO conjugate was used, there was a 100% reduction inP. gingivalisviable counts but no significant reduction in the incorporation of [3H]Tdr by HGFs. These results demonstrate that specific targeting ofP. gingivaliscan be achieved using TBO conjugated to a monoclonal antibody raised against a cell surface component of this organism.
Activities of Trovafloxacin, Gatifloxacin, Clinafloxacin, Sparfloxacin, Levofloxacin, and Ciprofloxacin against Penicillin-Resistant
Streptococcus pneumoniae
in an In Vitro Infection Model
Authors: Hershberger Ellie , Rybak Michael J. 
Published: July 2002

ABSTRACT

We adapted an in vitro pharmacodynamic model of infection to incorporate infected fibrin clots. The bactericidal activities of various fluoroquinolones against two strains of penicillin-resistant
Streptococcus pneumoniae
were studied over a 48-h period. Bacteria were prepared in Muller-Hinton broth by using colonies from a 24-h tryptic soy agar plus 5% sheep blood plate and were added to a mixture of cryoprecipitate (80%) and thrombin (10%) to achieve approximately 10
6
CFU of organism per fibrin clot. The fibrin clots were suspended into the models and removed, in triplicate, at various time points over 48 h. Control models were also conducted to characterize the growth of
S. pneumoniae
in the growth medium without antibiotic. Trovafloxacin, gatifloxacin, clinafloxacin, sparfloxacin, levofloxacin, and ciprofloxacin were administered to simulate their pharmacokinetic profiles in humans. Fibrin clot samples were also plated onto antibiotic-containing tryptic soy agar plus 5% lysed horse blood to detect resistance. The newer fluoroquinolones demonstrated better activity than ciprofloxacin against both isolates. In conclusion, the newer quinolones demonstrated significant activity against penicillin-resistant
S. pneumoniae
, with standard dosing resulting in area under the concentration-time curve/MIC ratios and peak concentration/MIC ratios that resulted in 99.9% killing against these isolates.
Pulsed Ultrasound Enhances the Killing of
Escherichia coli
Biofilms by Aminoglycoside Antibiotics In Vivo
Authors: Rediske Andrea M. , Roeder Beverly L. , Nelson Jared L. , Robison Rachel L. , Schaalje G. Bruce , Robison Richard A. , Pitt William G. 
Published: July 2002

ABSTRACT

Escherichia coli
biofilms on two polyethylene disks were implanted subcutaneously into rabbits receiving systemic gentamicin. Ultrasound was applied for 24 h to one disk. Both disks were removed, and viable bacteria were counted. Pulsed ultrasound significantly reduced bacterial viability below that of nontreated biofilms without damage to the skin.
In Vitro Activity of ABT 773, a New Ketolide Antibiotic, against
Chlamydia pneumoniae
Authors: Strigl Sebastian , Roblin Patricia M. , Reznik Tamara , Hammerschlag Margaret R. 
Published: July 2002

ABSTRACT

The in vitro activities of ABT 773, telithromycin (HMR 3647), azithromycin, clarithromycin, erythromycin, and levofloxacin were tested against 20 strains of
Chlamydia pneumoniae
. The MIC at which 90% of the isolates were inhibited and the minimal bactericidal concentration at which 90% of the isolates were killed by ABT 773 were 0.015 μg/ml (range, 0.008 to 0.015 μg/ml). ABT 773 was the most active antibiotic tested in this study.
In Vitro Pharmacodynamic Parameters of Sordarin Derivatives in Comparison with Those of Marketed Compounds against
Pneumocystis carinii
Isolated from Rats
Authors: Aviles Pablo , Aliouat El-Moukhtar , Martinez Antonio , Dei-Cas Eduardo , Herreros Esperanza , Dujardin Lucien , Gargallo-Viola Domingo 
Published: July 2002

ABSTRACT

Pneumocystis carinii
pneumonia remains one of the most serious complications of immunosuppressed patients. In this study, the in vitro pharmacodynamic parameters of four sordarin derivatives (GM 191519, GM 237354, GM 193663, and GM 219771) have been evaluated by a new quantitative approach and compared with the commercially available drugs pentamidine, atovaquone, and trimethoprim-sulfamethoxazole (TMP-SMX). In vitro activities and in vivo therapeutic efficacies of sordarin derivatives against
P. carinii
were also evaluated. In vitro activity was determined by the broth microdilution technique, comparing the total number of microorganisms in treated and drug-free cultures by using Giemsa staining. The in vitro maximum effect (
E
max
), the drug concentrations to reach 50% of
E
max
(EC
50
), and the slope of the dose-response curve were then estimated by the Hill equation (
E
max
sigmoid model). Sordarin derivatives were the most potent agents against
P. carinii
, with EC
50
s of 0.00025, 0.0007, 0.0043, and 0.025 μg/ml for GM 191519, GM 237354, GM 193663, and GM 219771, respectively. The EC
50
s of pentamidine, atovaquone, and TMP-SMX were 0.025, 0.16, and 26.7/133.5 μg/ml, respectively. The results obtained with this approach showed GM 237354 and GM 191519 to be approximately 35- and 100-fold more active in vitro than pentamidine, the most active marketed compound. All sordarin derivatives tested were at least 5,000-fold more active in vitro than TMP-SMX. The three sordarin derivatives tested in vivo—GM 191519, GM 237354, and GM 219771—showed a marked therapeutic efficacy, defined as reduction of cyst forms per gram of lung. GM 191519 was the most potent (daily dose reducing 50% of the
P. carinii
burden in the lungs [ED
50
], 0.05 mg/kg/day) followed by GM 237354 and GM 219771 (ED
50
s, 0.30 and 0.49 mg/kg/day, respectively). Good agreement between in vitro parameters and in vivo outcome was obtained when
P. carinii
pneumonia in rats was treated with sordarin derivatives.
Prevalence of SHV-12 among Clinical Isolates of
Klebsiella pneumoniae
Producing Extended-Spectrum β-Lactamases and Identification of a Novel AmpC Enzyme (CMY-8) in Southern Taiwan
Authors: Yan Jing-Jou , Wu Shiou-Mei , Tsai Shu-Huei , Wu Jiunn-Jong , Su Ih-Jen 
Published: July 2002

ABSTRACT

Twenty (8.5%) of 234 nonrepetitive clinical isolates of
Klebsiella pneumoniae
from southern Taiwan were found to produce extended-spectrum β-lactamases (ESBLs): 10 strains produced SHV-12, 4 produced SHV-5, 2 produced a non-TEM non-SHV ESBL with a pI of 8.3, 3 produced a novel AmpC β-lactamase designated CMY-8 with a pI of 8.25, and 1 produced SHV-12 and an unidentified AmpC enzyme with a pI of 8.2. The CMY-8 enzyme confers a resistance phenotype similar to CMY-1 and MOX-1, and sequence comparisons showed high homologies (>95%) of nucleotide and amino acid sequences among these three enzymes. Plasmid and pulse-field gel electrophoresis analyses revealed that all isolates harboring an SHV-derived ESBL were genetically unrelated, indicating that dissemination of resistance plasmids is responsible for the spread of SHV ESBLs among
K. pneumoniae
in this area. All three isolates carrying CMY-8 had identical genotypic patterns, suggesting the presence of an epidemic strain.
Increasing Bacterial Resistance in Pediatric Acute Conjunctivitis (1997–1998)
Authors: Block Stan L. , Hedrick James , Tyler Ron , Smith Alan , Findlay Rebecca , Keegan Eileen , Stroman Dave W. 
Published: July 2002

ABSTRACT

We sought to determine the current level of resistance in
Haemophilus influenzae
and
Streptococcus pneumoniae
, the primary pathogens of pediatric conjunctivitis. Between January 1997 and March 1998, we prospectively cultured acute conjunctivitis in 250 ambulatory pediatric patients from rural Kentucky whose average age was 24.3 months. In those 250 cases, 106
H. influenzae
(42% of the total) and 75
S. pneumoniae
(30% of the total) pathogens were isolated, with no growth or no pathogen resulting in 79 cases (32% of the total). Beta-lactamase was detected in 60 (69%) of 87 tested strains of
H. influenzae
. Among 65 isolates of
S. pneumoniae
tested for penicillin susceptibility, 44 (68%) were susceptible, 17 (26%) were resistant, and 4 (6%) were intermediate. Conjunctivitis with acute otitis media was observed in 97 patients (39%), and
H. influenzae
was recovered in 57% of these 97 cases. As for in vitro activity, ciprofloxacin, ofloxacin, and tetracycline were the most active; and gentamicin, tobramycin, polymyxin B-trimethoprim, and polymyxin B-neomycin were intermediately active. Sulfamethoxazole possessed no activity against either pathogen. Beta-lactamase production was detected in 69% of
H. influenzae
strains, which still remains the primary causative pathogen of both conjunctivitis and conjunctivitis-otitis syndrome. Penicillin-nonsusceptible
S. pneumoniae
was observed in 32% of 65 patients with
S. pneumoniae
conjunctivitis, with most strains being penicillin resistant.
Postantibiotic Suppression of Growth of Erythromycin A-Susceptible and -Resistant Gram-Positive Bacteria by the Ketolides Telithromycin (HMR 3647) and HMR 3004
Authors: Munckhof Wendy J. , Borlace Glenn , Turnidge John D. 
Published: July 2002

ABSTRACT

We investigated the in vitro postantibiotic effects (PAEs) of the ketolides telithromycin (HMR 3647) and HMR 3004 and analyzed the results using the sigmoid
E
max
model. Mean maximum telithromycin PAEs against erythromycin A-susceptible strains of
Staphylococcus aureus
,
Streptococcus pyogenes
, and
Streptococcus pneumoniae
were 3.7, 8.9, and 9.7 h, respectively, while maximum PAEs for erythromycin A-resistant strains were much shorter. Mean maximum HMR 3004 PAEs were 3.2 to 4.4 h for all species.
Rapid Discriminatory Detection of Genes Coding for SHV β-Lactamases by Ligase Chain Reaction
Authors: Kim Jungmin , Lee Hoan-Jong 
Published: July 2002

ABSTRACT

Ligase chain reaction (LCR) is a recently developed technique that employs a thermostable ligase and allows for the discrimination of DNA sequences differing in only a single base pair. The method has been adapted and applied to differentiation of
bla
SHV
genes. We have developed an LCR typing method to characterize point mutations in genes for SHV-derived extended-spectrum β-lactamases with four different sets of biotinylated LCR primers. To evaluate the applicability of the current technique, we tested seven
Escherichia coli
strains producing SHV-1, SHV-2, SHV-2a, SHV-3, SHV-4, SHV-5, and SHV-12. With the LCR typing, seven SHV genes can be distinguished according to their incorporating point mutations. In an attempt to characterize SHV β-lactamases by LCR typing in clinical isolates, 46 strains carrying
bla
SHV
genes (32
Klebsiella pneumoniae
, 10
Enterobacter cloacae
, and 4
E. coli
) were subjected to antibiotic susceptibility testing, isoelectric focusing, and LCR typing. LCR typing allowed the characterization of β-lactamases, and genotypes obtained by LCR typing were in accordance with phenotypes such as antibiotic resistance profile and pI value of β-lactamase. Therefore, we concluded that LCR typing may permit defining the SHV families with simplicity and reliability and can be applied to the detailed characterization and molecular epidemiology of SHV-type β-lactamases.
Genetic Organization of the Downstream Region of the
mecA
Element in Methicillin-Resistant
Staphylococcus aureus
Isolates Carrying Different Polymorphisms of This Region
Authors: Oliveira Duarte C. , Wu Shang W. , de Lencastre Hermínia 
Published: July 2002

ABSTRACT

We describe here the genetic organization of the
mec
element downstream of the
mecA
gene in 34 different methicillin-resistant
Staphylococcus aureus
(MRSA) clinical isolates carrying 13 of the most frequent polymorphisms of
mecA
and representing the major epidemic clones of MRSA. All polymorphisms carried three common genetic elements: the hypervariable region, a copy of IS
431
, and a unique 2-kb sequence (downstream constant segment, or
dcs
) for which no homologous sequences are found in data banks. Polymorphisms of the downstream region were shown to be caused by the presence of linearized plasmids flanked by insertion sequences (pUB110, pT181, and pI258) and the autonomous insertion sequence IS
256
.
A Novel CTX-M β-Lactamase (CTX-M-8) in Cefotaxime-Resistant
Enterobacteriaceae
Isolated in Brazil
Authors: Bonnet R. , Sampaio J. L. M. , Labia R. , De Champs C. , Sirot D. , Chanal C. , Sirot J. 
Published: July 2002

ABSTRACT

To estimate the diversity of extended-spectrum β-lactamases in Brazil, 18 strains from different species of the family
Enterobacteriaceae
exhibiting a positive double-disk synergy test were collected by a clinical laboratory from several hospitals in Rio de Janeiro, Brazil, in 1996 and 1997. Four strains (
Proteus mirabilis
,
Enterobacter cloacae
,
Enterobacter aerogenes
, and
Citrobacter amalonaticus
) hybridized with a 550-bp CTX-M probe. The
P. mirabilis
strain produced a CTX-M-2 enzyme. The
E. cloacae
,
E. aerogenes
, and
C. amalonaticus
isolates harbored a
bla
gene which was identified by cloning and sequencing as a
bla
CTX-M
gene.
E. coli
HB101 transconjugants and the
E. coli
DH5α transformant harboring a recombinant plasmid produced a CTX-M β-lactamase with an isoelectric point of 7.6 conferring a resistance phenotype characterized by a higher level of resistance to cefotaxime than to ceftazidime, as observed with the other CTX-M enzymes. The deduced protein sequence showed a novel Ambler class A CTX-M enzyme, named CTX-M-8, which had 83 to 88% identity with the previously described CTX-M enzymes. The phylogenic study of the CTX-M family including CTX-M-8 revealed four CTX-M types, CTX-M-8 being the first member of a new phylum of CTX-M enzymes. The evolutionary distances between the four types of CTX-M were large, suggesting that the four clusters branched off early from a distant unknown enzyme and that intermediate enzymes probably existed.
In Vitro Activities of Linezolid Alone and in Combination with Amoxicillin, Clarithromycin, and Metronidazole againstHelicobacter pylori
Authors: Hirschl Alexander M. , Apfalter Petra , Makristathis Athanasios , Rotter Manfred L. , Wimmer Margit 
Published: July 2002

ABSTRACTLinezolid was tested against 70 strains ofHelicobacter pyloriby the agar dilution method. The MIC range and MICs at which 50 and 90% of strains were inhibited were 8 to 64, 16, and 32 μg/ml, respectively. With minimum and maximum fractional inhibitory concentration summation values of 0.31 and 2.50, respectively, the combination of linezolid with amoxicillin, clarithromycin, or metronidazole showed either partial synergy or indifference for the majority of strains.
Comparative Activities of Telithromycin (HMR 3647), Levofloxacin, and Other Antimicrobial Agents against Human Mycoplasmas
Authors: Bebear C. M. , Renaudin H. , Bryskier A. , Bebear C. 
Published: July 2002

ABSTRACT

The activities of telithromycin and levofloxacin against 99 mycoplasma strains were compared to those of several macrolides, ofloxacin, and doxycycline. Telithromycin MICs of ≤0.25 μg/ml were found for all isolates, except for
Mycoplasma hominis
, while levofloxacin was active at concentrations of ≤1 μg/ml against all species studied.
Multiple-Dose Pharmacokinetics and Pharmacodynamics of Abacavir Alone and in Combination with Zidovudine in Human Immunodeficiency Virus-Infected Adults
Authors: McDowell James A. , Lou Yu , Symonds William S. , Stein Daniel S. 
Published: July 2002

ABSTRACT

Abacavir (1592U89) is a nucleoside reverse transcriptase inhibitor with potent activity against human immunodeficiency virus type 1 (HIV-1) when used alone or in combination with other antiretroviral agents. The present study was conducted to determine the multiple-dose pharmacokinetics and pharmacodynamics of abacavir in HIV-1-infected subjects following oral administration of daily doses that ranged from 600 to 1,800 mg, with and without zidovudine. Seventy-nine subjects received abacavir monotherapy for 4 weeks (200, 400, or 600 mg every 8 hours [TID] and 300 mg every 12 h [BID]) and thereafter received either zidovudine (200 mg TID or 300 mg BID) or matching placebo with abacavir for 8 additional weeks. Pharmacokinetic parameters were calculated for abacavir after administration of the first dose and at week 4 and for abacavir, zidovudine, and its glucuronide metabolite at week 12. The concentrations of abacavir in cerebrospinal fluid were determined in a subset of subjects. Steady-state plasma abacavir concentrations were achieved by week 4 of monotherapy and persisted to week 12. At steady state, abacavir pharmacokinetic parameters (area under the plasma concentration-time curve for a dosing interval [AUC
tau
] and peak concentration [
C
max
]) were generally proportional to dose over the range of a 600- to 1,200-mg total daily dose. Coadministration of zidovudine with abacavir produced a small and inconsistent effect on abacavir pharmacokinetic parameters across the different doses. At the clinical abacavir dose (300 mg BID) zidovudine coadministration had no effect on the abacavir AUC
tau
, which is most closely associated with efficacy. Zidovudine pharmacokinetics appeared to be unaffected by abacavir. Statistically significant but weak relationships were found for the change in the log
10
HIV-1 RNA load from the baseline to week 4 versus total daily AUC
tau
and
C
tau
(
P
< 0.05). The incidence of nausea was significantly associated with total daily AUC
tau
and
C
max
. In conclusion, abacavir has predictable pharmacokinetic characteristics following the administration of multiple doses.
Urinary Excretion and Bactericidal Activities of Gemifloxacin and Ofloxacin after a Single Oral Dose in Healthy Volunteers
Authors: Naber Christoph K. , Hammer Michaela , Kinzig-Schippers Martina , Sauber Christian , Sörgel Fritz , Bygate Elizabeth A. , Fairless Amanda J. , Machka Konstanze , Naber Kurt G. 
Published: July 2002

ABSTRACT

In a randomized crossover study, 16 volunteers (8 men, 8 women) received single oral doses of 320 mg of gemifloxacin and 400 mg of ofloxacin on two separate occasions in the fasting state to assess the urinary excretion and urinary bactericidal titers (UBTs) at intervals for up to 144 h. Ofloxacin showed higher concentrations in urine compared with those of gemifloxacin. The median (range) cumulative excretion of gemifloxacin was 29.7% (8.4 to 48.7%) of the parent drug administered, and median (range) cumulative excretion of ofloxacin was 84.3% (46.5 to 95.2%) of the parent drug administered. The UBTs, i.e., the highest twofold dilutions (with antibiotic-free urine as the diluent) of urine that were still bactericidal, were determined for a reference strain and nine uropathogens for which the MICs of gemifloxacin and ofloxacin were as follows:
Escherichia coli
ATCC 25922, 0.016 and 0.06 μg/ml, respectively;
Klebsiella pneumoniae
, 0.03 and 0.06 μg/ml, respectively;
Proteus mirabilis
, 0.125 and 0.125 μg/ml, respectively;
Escherichia coli
, 0.06 and 0.5 μg/ml, respectively;
Pseudomonas aeruginosa
, 1 and 4 μg/ml, respectively;
Staphylococcus aureus
, 0.008 and 0.25 μg/ml, respectively;
Enterococcus faecalis
, 0.06 and 2 μg/ml, respectively;
Staphylococcus aureus
, 0.25 and 4 μg/ml, respectively;
Enterococcus faecalis
, 0.5 and 32 μg/ml, respectively; and
Staphylococcus aureus
, 2 and 32 μg/ml, respectively. Generally, the UBTs for gram-positive uropathogens were higher for gemifloxacin than for ofloxacin and the UBTs for gram-negative uropathogens were higher for ofloxacin than for gemifloxacin. According to the UBTs, ofloxacin-resistant uropathogens (MICs, ≥4 mg/liter) should also be considered gemifloxacin resistant. Although clinical trials have shown that gemifloxacin is effective for the treatment of uncomplicated urinary tract infections, whether an oral dosage of 320 mg of gemifloxacin once daily is also adequate for the treatment of complicated urinary tract infections has yet to be confirmed.