bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antipneumococcal Activities of Gemifloxacin Compared to Those of Nine Other Agents
Authors: Davies Todd A. , Kelly Linda M. , Pankuch Glenn A. , Credito Kim L. , Jacobs Michael R. , Appelbaum Peter C. 
Published: July 2002

ABSTRACT

The activities of gemifloxacin compared to those of nine other agents was tested against a range of penicillin-susceptible and -resistant pneumococci by agar dilution, microdilution, time-kill, and post-antibiotic effect (PAE) methods. Against 64 penicillin-susceptible, 68 penicillin-intermediate, and 75 penicillin-resistant pneumococci (all quinolone susceptible), agar dilution MIC
50
s (MICs at which 50% of isolates are inhibited)/MIC
90
s (in micrograms per milliliter) were as follows: gemifloxacin, 0.03/0.06; ciprofloxacin, 1.0/4.0; levofloxacin, 1.0/2.0; sparfloxacin, 0.5/1.0; grepafloxacin, 0.125/0.5; trovafloxacin, 0.125/0.25; amoxicillin, 0.016/0.06 (penicillin-susceptible isolates), 0.125/1.0 (penicillin-intermediate isolates), and 2.0/4.0 (penicillin-resistant isolates); cefuroxime, 0.03/0.25 (penicillin-susceptible isolates), 0.5/2.0 (penicillin-intermediate isolates), and 8.0/16.0 (penicillin-resistant isolates); azithromycin, 0.125/0.5 (penicillin-susceptible isolates), 0.125/>128.0 (penicillin-intermediate isolates), and 4.0/>128.0 (penicillin-resistant isolates); and clarithromycin, 0.03/0.06 (penicillin-susceptible isolates), 0.03/32.0 (penicillin-intermediate isolates), and 2.0/>128.0 (penicillin-resistant isolates). Against 28 strains with ciprofloxacin MICs of ≥8 μg/ml, gemifloxacin had the lowest MICs (0.03 to 1.0 μg/ml; MIC
90
, 0.5 μg/ml), compared with MICs ranging between 0.25 and >32.0 μg/ml (MIC
90
s of 4.0 to >32.0 μg/ml) for other quinolones. Resistance in these 28 strains was associated with mutations in
parC
,
gyrA
,
parE
, and/or
gyrB
or efflux, with some strains having multiple resistance mechanisms. For 12 penicillin-susceptible and -resistant pneumococcal strains (2 quinolone resistant), time-kill results showed that levofloxacin at the MIC, gemifloxacin and sparfloxacin at two times the MIC, and ciprofloxacin, grepafloxacin, and trovafloxacin at four times the MIC were bactericidal for all strains after 24 h. Gemifloxacin was uniformly bactericidal after 24 h at ≤0.5 μg/ml. Various degrees of 90 and 99% killing by all quinolones were detected after 3 h. Gemifloxacin and trovafloxacin were both bactericidal at two times the MIC for the two quinolone-resistant pneumococci. Amoxicillin at two times the MIC and cefuroxime at four times the MIC were uniformly bactericidal after 24 h, with some degree of killing at earlier time points. Macrolides gave slower killing against the seven susceptible strains tested, with 99.9% killing of all strains at two to four times the MIC after 24 h. PAEs for five quinolone-susceptible strains were similar (0.3 to 3.0 h) for all quinolones, and significant quinolone PAEs were found for the quinolone-resistant strain.
Characterization of TEM-56, a Novel β-Lactamase Produced by a
Klebsiella pneumoniae
Clinical Isolate
Authors: Neuwirth Catherine , Labia Roger , Siebor Eliane , Pechinot Andre , Madec Stephanie , Chaibi El Bachir , Kazmierczak Antoine 
Published: July 2002

ABSTRACT

TEM-56 produced by a
Klebsiella pneumoniae
clinical isolate is a novel β-lactamase of isoelectric point 6.4 that confers a moderate resistance level to expanded-spectrum cephalosporins. The amino acid sequence deduced from the corresponding
bla
gene showed two amino acid replacements with respect to the TEM-2 sequence: Glu-104 to Lys and His-153 to Arg. This enzyme showed catalytic properties close to those of TEM-18. Thus, TEM-56 appears as a new TEM mutant, an intermediary between TEM-18 and the extended-spectrum β-lactamase TEM-21.
Mechanism of Uptake of a Cationic Water-Soluble Pyridinium Zinc Phthalocyanine across the Outer Membrane of
Escherichia coli
Authors: Minnock Andrew , Vernon David I. , Schofield Jack , Griffiths John , Parish J. Howard , Brown Stanley B. 
Published: July 2002

ABSTRACT

Previous studies have shown that a cationic water-soluble pyridinium zinc phthalocyanine (PPC) is a powerful photosensitizer that is able to inactivate
Escherichia coli
. In the current work incubation of
E. coli
cells with PPC in the dark caused alterations in the outer membrane permeability barrier of the cells, rendering the bacteria much more sensitive to hydrophobic compounds, with little effect seen with hydrophilic compounds. Addition of Mg
2+
to the medium prior to incubation of the cells with PPC prevented these alterations in the outer membrane permeability barrier. The presence of Mg
2+
in the medium also prevented the photoinactivation of
E. coli
cells with PPC. These results are consistent with the hypothesis that PPC gains access across the outer membrane of
E. coli
cells via the self-promoted uptake pathway, a mechanism of uptake postulated for the uptake of other cationic compounds across the outer membranes of gram-negative bacteria.
Role of Antibiotic Penetration Limitation in
Klebsiella pneumoniae
Biofilm Resistance to Ampicillin and Ciprofloxacin
Authors: Anderl Jeff N. , Franklin Michael J. , Stewart Philip S. 
Published: July 2002

ABSTRACT

The penetration of two antibiotics, ampicillin and ciprofloxacin, through biofilms developed in an in vitro model system was investigated. The susceptibilities of biofilms and corresponding freely suspended bacteria to killing by the antibiotics were also measured. Biofilms of
Klebsiella pneumoniae
were developed on microporous membranes resting on agar nutrient medium. The susceptibilities of planktonic cultures and biofilms to 10 times the MIC were determined. Antibiotic penetration through biofilms was measured by assaying the concentration of antibiotic that diffused through the biofilm to an overlying filter disk. Parallel experiments were performed with a mutant
K. pneumoniae
strain in which β-lactamase activity was eliminated. For wild-type
K. pneumoniae
grown in suspension culture, ampicillin and ciprofloxacin MICs were 500 and 0.18 μg/ml, respectively. The log reductions in the number of CFU of planktonic wild-type bacteria after 4 h of treatment at 10 times the MIC were 4.43 ± 0.33 and 4.14 ± 0.33 for ampicillin and ciprofloxacin, respectively. Biofilms of the same strain were much less susceptible, yielding log reductions in the number of CFU of −0.06 ± 0.06 and 1.02 ± 0.04 for ampicillin and ciprofloxacin, respectively, for the same treatment. The number of CFU in the biofilms after 24 h of antibiotic exposure was not statistically different from the number after 4 h of treatment. Ampicillin did not penetrate wild-type
K. pneumoniae
biofilms, whereas ciprofloxacin and a nonreactive tracer (chloride ion) penetrated the biofilms quickly. The concentration of ciprofloxacin reached the MIC throughout the biofilm within 20 min. Ampicillin penetrated biofilms formed by a β-lactamase-deficient mutant. However, the biofilms formed by this mutant were resistant to ampicillin treatment, exhibiting a 0.18 ± 0.07 log reduction in the number of CFU after 4 h of exposure and a 1.64 ± 0.33 log reduction in the number of CFU after 24 h of exposure. Poor penetration contributed to wild-type biofilm resistance to ampicillin but not to ciprofloxacin. The increased resistance of the wild-type strain to ciprofloxacin and the mutant strain to ampicillin and ciprofloxacin could not be accounted for by antibiotic inactivation or slow diffusion since these antibiotics fully penetrated the biofilms. These results suggest that some other resistance mechanism is involved for both agents.
Itraconazole Oral Solution for Primary Prophylaxis of Fungal Infections in Patients with Hematological Malignancy and Profound Neutropenia: a Randomized, Double-Blind, Double-Placebo, Multicenter Trial Comparing Itraconazole and Amphotericin B
Authors: Harousseau J. L. , Dekker A. W. , Stamatoullas-Bastard A. , Fassas A. , Linkesch W. , Gouveia J. , De Bock R. , Rovira M. , Seifert W. F. , Joosen H. , Peeters M. , De Beule K. 
Published: July 2002

ABSTRACTSystemic and superficial fungal infections are a major problem among immunocompromised patients with hematological malignancy. A double-blind, double-placebo, randomized, multicenter trial was performed to compare the efficacy and safety of itraconazole oral solution (2.5 mg/kg of body weight twice a day) with amphotericin B capsules (500 mg orally four times a day) for prophylaxis of systemic and superficial fungal infection. Prophylactic treatment was initiated on the first day of chemotherapy and was continued until the end of the neutropenic period (>0.5 × 109neutrophils/liter) or up to a maximum of 3 days following the end of neutropenia, unless a systemic fungal infection was documented or suspected. The maximum treatment duration was 56 days. In the intent-to-treat population, invasive aspergillosis was noted in 5 (1.8%) of the 281 patients assigned to itraconazole oral solution and in 9 (3.3%) of the 276 patients assigned to oral amphotericin B; of these, 1 and 4 patients died, respectively. Proven systemic fungal infection (including invasive aspergillosis) occurred in 8 patients (2.8%) who received itraconazole, compared with 13 (4.7%) who received oral amphotericin B. Itraconazole significantly reduced the incidence of superficial fungal infections as compared to oral amphotericin B (2 [1%] versus 13 [5%];P= 0.004). Although the incidences of suspected fungal infection (including fever of unknown origin) were not different between the groups, fewer patients were administered intravenous systemic antifungals (mainly intravenous amphotericin B) in the group receiving itraconazole than in the group receiving oral amphotericin B (114 [41%] versus 132 [48%];P= 0.066). Adequate plasma itraconazole levels were achieved in about 80% of the patients from 1 week after the start of treatment. In both groups, the trial medication was safe and well tolerated. Prophylactic administration of itraconazole oral solution significantly reduces superficial fungal infection in patients with hematological malignancies and neutropenia. The incidence of proven systemic fungal infections, the number of deaths due to deep fungal infections, and the use of systemic antifungals tended to be lower in the itraconazole-treated group than in the amphotericin B-treated group, without statistical significance. Itraconazole oral solution is a broad-spectrum systemic antifungal agent with prophylactic activity in neutropenic patients, especially for those at high risk of prolonged neutropenia.
Anti-
Toxoplasma
Activities of Antiretroviral Drugs and Interactions with Pyrimethamine and Sulfadiazine In Vitro
Authors: Derouin Francis , Santillana-Hayat Maud 
Published: July 2002

ABSTRACT

The anti-
Toxoplasma
activities of nine antiretroviral drugs were examined in vitro. Nucleoside analogs had no effect on parasite growth, whereas ritonavir and nelfinavir were inhibitory for
Toxoplasma
, with 50% inhibitory concentrations of 5.4 and 4.0 μg/ml, respectively. None of the antiviral drugs affected the anti-
Toxoplasma
activity of pyrimethamine or sulfadiazine.
Effectiveness of Once-Weekly Rifapentine and Moxifloxacin Regimens against
Mycobacterium tuberculosis
in Mice
Authors: Lounis Nacer , Bentoucha Abdelhalim , Truffot-Pernot Chantal , Ji Baohong , O'Brien Richard J. , Vernon Andrew , Roscigno Giorgio , Grosset Jacques 
Published: July 2002

ABSTRACT

Mice infected with 1.6 × 10
7
CFU of
Mycobacterium tuberculosis
were treated 14 days later for 6 months with a regimen of once-weekly 10 mg of rifapentine and 75 mg of isoniazid per kg of body weight supplemented with either 150 mg of streptomycin per kg or 100 mg of moxifloxacin per kg during either both the 2-week daily initial and once-weekly continuation phases or only in the daily 2-week initial phase. On completion of treatment, all lung cultures were negative, except for three mice, each with a single colony: two whose rifapentine-isoniazid regimen was supplemented with streptomycin during the whole course of therapy and one whose rifapentine-isoniazid regimen had no initial daily phase, but was supplemented with streptomycin and moxifloxacin during the whole course of therapy. After 3 months of follow-up, positive lung cultures were obtained from 61 and 56% of mice supplemented with streptomycin during either the full course of therapy or only the daily 2-week initial phase, respectively, and 15 and 50% of mice supplemented with moxifloxacin during either the full course of therapy or only the daily 2-week initial phase, respectively. These results suggest that moxifloxacin has sterilizing activity against
M. tuberculosis
.
Safety, Tolerance, and Pharmacokinetics of High-Dose Liposomal Amphotericin B (AmBisome) in Patients Infected withAspergillusSpecies and Other Filamentous Fungi: Maximum Tolerated Dose Study
Authors: Walsh Thomas J. , Goodman Jesse L. , Pappas Peter , Bekersky Ihor , Buell Donald N. , Roden Maureen , Barrett John , Anaissie Elias J. 
Published: July 2002

ABSTRACTWe conducted a phase I-II study of the safety, tolerance, and plasma pharmacokinetics of liposomal amphotericin B (L-AMB; AmBisome) in order to determine its maximally tolerated dosage (MTD) in patients with infections due toAspergillusspp. and other filamentous fungi. Dosage cohorts consisted of 7.5, 10.0, 12.5, and 15.0 mg/kg of body weight/day; a total of 44 patients were enrolled, of which 21 had a proven or probable infection (13 aspergillosis, 5 zygomycosis, 3 fusariosis). The MTD of L-AMB was at least 15 mg/kg/day. Infusion-related reactions of fever occurred in 8 (19%) and chills and/or rigors occurred in 5 (12%) of 43 patients. Three patients developed a syndrome of substernal chest tightness, dyspnea, and flank pain, which was relieved by diphenhydramine. Serum creatinine increased two times above baseline in 32% of the patients, but this was not dose related. Hepatotoxicity developed in one patient. Steady-state plasma pharmacokinetics were achieved by day 7. The maximum concentration of drug in plasma (Cmax) of L-AMB in the dosage cohorts of 7.5, 10.0, 12.5, and 15.0 mg/kg/day changed to 76, 120, 116, and 105 μg/ml, respectively, and the mean area under the concentration-time curve at 24 h (AUC24) changed to 692, 1,062, 860, and 554 μg · h/ml, respectively, while mean CL changed to 23, 18, 16, and 25 ml/h/kg, respectively. These data indicate that L-AMB follows dose-related changes in disposition processing (e.g., clearance) at dosages of ≥7.5 mg/kg/day. Because several extremely ill patients had early death, success was determined for both the modified intent-to-treat and evaluable (7 days of therapy) populations. Response rates (defined as complete response and partial response) were similar for proven and probable infections. Response and stabilization, respectively, were achieved in 36 and 16% of the patients in the modified intent-to-treat population (n= 43) and in 52 and 13% of the patients in the 7-day evaluable population (n= 31). These findings indicate that L-AMB at dosages as high as 15 mg/kg/day follows nonlinear saturation-like kinetics, is well tolerated, and can provide effective therapy for aspergillosis and other filamentous fungal infections.
Plasmid Location and Molecular Heterogeneity of the L1 and L2 β-Lactamase Genes of
Stenotrophomonas maltophilia
Authors: Avison Matthew B. , Higgins Catherine S. , von Heldreich Charlotte J. , Bennett Peter M. , Walsh Timothy R. 
Published: July 2002

ABSTRACT

An approximately 200-kb plasmid has been purified from clinical isolates of
Stenotrophomonas maltophilia
. This plasmid was found in all of the 10 isolates examined and contains both the L1 and the L2 β-lactamase genes. The location of
L1
and
L2
on a plasmid makes it more likely that they could spread to other gram-negative bacteria, potentially causing clinical problems. Sequence analysis of the 10 L1 genes revealed three novel genes,
L1c, L1d
, and
L1e
, with 8, 12, and 20% divergence from the published strain IID 1275
L1
(
L1a
), respectively. The most unusual L1 enzyme (L1e) displayed markedly different kinetic properties, with respect to hydrolysis of nitrocefin and imipenem, compared to those of L1a (250- and 100-fold lower
k
cat
/

K
m

ratios respectively). L1c and L1d, in contrast, displayed levels of hydrolysis very similar to that of L1a. Several nonconservative amino acid differences with respect to L1a, L1b, L1c, and L1d were observed in the substrate binding-catalytic regions of L1e, and this could explain the kinetic differences. Three novel L2 genes (
L2b, L2c
, and
L2d
) were sequenced from the same isolates, and their sequences diverge from the published sequence of strain IID 1275
L2
(
L2a
) by 4, 9, and 25%, respectively. Differences in L1 and L2 gene sequences were not accompanied by similar divergences in 16S rRNA gene sequences, for which differences of <1% were found. It is therefore apparent that the L1 and L2 genes have evolved relatively quickly, perhaps because of their presence on a plasmid.
Drug Targeting
Mycobacterium tuberculosis
Cell Wall Synthesis: Genetics of dTDP-Rhamnose Synthetic Enzymes and Development of a Microtiter Plate-Based Screen for Inhibitors of Conversion of dTDP-Glucose to dTDP-Rhamnose
Authors: Ma Yufang , Stern Richard J. , Scherman Michael S. , Vissa Varalakshmi D. , Yan Wenxin , Jones Victoria Cox , Zhang Fangqiu , Franzblau Scott G. , Lewis Walter H. , McNeil Michael R. 
Published: July 2002

ABSTRACT

An
l
-rhamnosyl residue plays an essential structural role in the cell wall of
Mycobacterium tuberculosis
. Therefore, the four enzymes (RmlA to RmlD) that form dTDP-rhamnose from dTTP and glucose-1-phosphate are important targets for the development of new tuberculosis therapeutics.
M. tuberculosis
genes encoding RmlA, RmlC, and RmlD have been identified and expressed in
Escherichia coli
. It is shown here that genes for only one isotype each of RmlA to RmlD are present in the
M. tuberculosis
genome. The gene for RmlB is Rv3464. Rv3264c was shown to encode ManB, not a second isotype of RmlA. Using recombinant RmlB, -C, and -D enzymes, a microtiter plate assay was developed to screen for inhibitors of the formation of dTDP-rhamnose. The three enzymes were incubated with dTDP-glucose and NADPH to form dTDP-rhamnose and NADP
+
with a concomitant decrease in optical density at 340 nm (OD
340
). Inhibitor candidates were monitored for their ability to lower the rate of OD
340
change. To test the robustness and practicality of the assay, a chemical library of 8,000 compounds was screened. Eleven inhibitors active at 10 μM were identified; four of these showed activities against whole
M. tuberculosis
cells, with MICs from 128 to 16 μg/ml. A rhodanine structural motif was present in three of the enzyme inhibitors, and two of these showed activity against whole
M. tuberculosis
cells. The enzyme assay was used to screen 60 Peruvian plant extracts known to inhibit the growth of
M. tuberculosis
in culture; two extracts were active inhibitors in the enzyme assay at concentrations of less than 2 μg/ml.
Effect of Drug Concentration on Emergence of Macrolide Resistance in
Mycobacterium avium
Authors: Nash Kevin A. 
Published: July 2002

ABSTRACT

The emergence of antibiotic resistance in mycobacteria involves the selection of mutant variants within a susceptible bacterial population. However, it is unclear whether antimycobacterial drugs act just as selective agents or can influence the rate of appearance of resistant mutants. The present study was initiated to address this issue by monitoring the effects of antimicrobial agents on the appearance and growth of clarithromycin (CLR)-resistant (CLR
r
) bacilli in broth cultures of
Mycobacterium avium
. Preexposure of
M. avium
to CLR had a significant dose effect on the emergence of resistance, with concentrations of 4 to 8 μg/ml resulting in a maximal (∼10
4
-fold) increase in the number of CLR
r
bacilli after a 4-day incubation. In addition, a dose effect was found with azithromycin. The use of combinations of CLR with either ethambutol (EMB) or rifabutin (RFB) resulted in fewer resistant bacilli compared to the use of CLR alone. The lowest active concentration of EMB (4 μg/ml) was equivalent to the EMB MIC (4 to 8 μg/ml) for the parental CLR
s
strain and the emergent CLR
r
variants, and thus, the antiresistance effect was probably the result of the bacteriostatic effect of EMB on CLR
r
bacilli. However, RFB was an order of magnitude more active (0.05 μg/ml) at reducing resistance than suggested by the MIC of this agent (0.5 to 1 μg/ml). These results indicate that the emergence of resistance was not simply the selection of a preexisting subpopulation of resistant bacilli. Further analysis suggested that early events in the emergence of resistance involved organisms (progenitors) that acquired a resistance phenotype. In addition, the progenitors appeared to be in a transient state, able to develop into a stable resistant lineage in the presence of CLR, or able to revert to the wild type in nonselective conditions.
Expression of Multidrug Efflux Pump SmeDEF by Clinical Isolates of
Stenotrophomonas maltophilia
Authors: Alonso Ana , Martinez Jose L. 
Published: July 2002

ABSTRACT

The presence of the multidrug efflux pump SmeDEF was assessed in a collection of clinical isolates of
Stenotrophomonas maltophilia
. All isolates encoded this pump, as demonstrated by PCR. Forty-seven percent of the strains overproduced a protein of the same size that was immunoreactive against an anti-SmeF antibody, and 33% overexpressed the gene
semD
when they were tested by reverse transcription-PCR. A correlation between
smeDEF
overexpression and antibiotic resistance was observed.
Mutational Replacement of Leu-293 in the Class C
Enterobacter cloacae
P99 β-Lactamase Confers Increased MIC of Cefepime
Authors: Vakulenko Sergei B. , Golemi Dasantila , Geryk Bruce , Suvorov Maxim , Knox James R. , Mobashery Shahriar , Lerner Stephen A. 
Published: July 2002

ABSTRACT

The class C β-lactamase from
Enterobacter cloacae
P99 confers resistance to a wide range of broad-spectrum β-lactams but not to the newer cephalosporin cefepime. Using PCR mutagenesis of the
E. cloacae
P99
ampC
gene, we obtained a Leu-293-Pro mutant of the P99 β-lactamase conferring a higher MIC of cefepime (MIC, 8 μg/ml, compared with 0.5 μg/ml conferred by the wild-type enzyme). In addition, the mutant enzyme produced higher resistance to ceftazidime but not to the other β-lactams tested. Mutants with 15 other replacements of Leu-293 were prepared by site-directed random mutagenesis. None of these mutant enzymes conferred MICs of cefepime higher than that conferred by Leu-293-Pro. We determined the kinetic parameters of the purified
E. cloacae
P99 β-lactamase and the Leu-293-Pro mutant enzyme. The catalytic efficiencies (
k
cat
/

K
m

) of the Leu-293-Pro mutant β-lactamase for cefepime and ceftazidime were increased relative to the respective catalytic efficiencies of the wild-type P99 β-lactamase. These differences likely contribute to the higher MICs of cefepime and ceftazidime conferred by this mutant β-lactamase.