bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Synergistic Effects of Double and Triple Combinations of β-Lactams, Vancomycin, and Netilmicin against Methicillin-Resistant
Staphylococcus aureus
Strains
Authors: Rochon-Edouard Stéphanie , Pestel-Caron Martine , Lemeland Jean-François , Caron François 
Published: July 2002

ABSTRACT

Several studies have previously reported synergistic effects between vancomycin and a given β-lactam or a given aminoglycoside against methicillin-resistant
Staphylococcus aureus
(MRSA) strains. The aim of our study was to exhaustively compare the effects of different combinations of a β-lactam, vancomycin, and/or an aminoglycoside against 32 clinical MRSA strains with different aminoglycoside susceptibility patterns. The effects of 26 different β-lactam–vancomycin and 8 different aminoglycoside-vancomycin combinations were first studied using a disk diffusion screening method. The best interactions with vancomycin were observed with either imipenem, cefazolin, or netilmicin. By checkerboard studies, imipenem-vancomycin and cefazolin-vancomycin each provided a synergistic bacteriostatic effect against 22 strains; the mean fractional inhibitory concentration (FIC) indexes were 0.35 and 0.46 for imipenem-vancomycin and cefazolin-vancomycin, respectively. The vancomycin-netilmicin combination provided an indifferent effect against all of the 32 strains tested; the mean of FIC index was 1.096. The mean concentrations of imipenem, cefazolin, netilmicin, and vancomycin at which FIC indexes were calculated were clinically achievable. Killing experiments were then performed using imipenem, cefazolin, netilmicin, and vancomycin at one-half of the MIC, alone and in different combinations, against 10 strains. The vancomycin-netilmicin regimen was rarely bactericidal, even against strains susceptible to netilmicin. The imipenem-vancomycin and cefazolin-vancomycin combinations were strongly bactericidal against six and five strains, respectively. The addition of netilmicin markedly enhanced the killing activity of the combination of cefazolin or imipenem plus vancomycin, but only for the MRSA strains against which the β-lactam–vancomycin combinations had no bactericidal effect. It is noteworthy that the latter strains were both susceptible to netilmicin and heterogeneously resistant to methicillin.
High-Level Fluoroquinolone-Resistant Clinical Isolates of
Escherichia coli
Overproduce Multidrug Efflux Protein AcrA
Authors: Mazzariol Annarita , Tokue Yutaka , Kanegawa Tiffany M. , Cornaglia Giuseppe , Nikaido Hiroshi 
Published: July 2002

ABSTRACT

Immunoblotting with antibody against AcrA, an obligatory component of the AcrAB multidrug efflux system, showed that this protein was overexpressed by ≥170% in 9 of 10 clinical isolates of
Esherichia coli
with high-level ciprofloxacin resistance (MICs, ≥32 μg/ml) but not in any of the 15 isolates for which the MIC was ≤1 μg/ml.
OXA-24, a Novel Class D β-Lactamase with Carbapenemase Activity in an
Acinetobacter baumannii
Clinical Strain
Authors: Bou Germán , Oliver Antonio , Martínez-Beltrán Jesús 
Published: July 2002

ABSTRACT

Acinetobacter baumannii
RYC 52763/97, a clinical isolate involved in a prolonged nosocomial outbreak at our hospital, was resistant to all β-lactams tested, including imipenem and meropenem, which had MICs of 128 and 256 μg/ml, respectively. This strain synthesized three β-lactamases: a plasmid-mediated TEM-1 β-lactamase (pI 5.4), an AmpC-type chromosomal cephalosporinase (pI 9.4), and a novel, presumptively chromosomally mediated OXA-related enzyme (pI 9.0) named OXA-24. After cloning and sequencing, the deduced amino acid sequence of the OXA-24 β-lactamase showed 40% homology with the OXA-10 (PSE-2) and OXA-7 β-lactamases, 39% homology with the OXA-11 and OXA-5 enzymes, and 33% homology with the LCR-1 β-lactamase. The amino acid sequence of the OXA-24 β-lactamase contained the STFK motif found in serine β-lactamases, but the typical class D triad KTG was replaced by KSG and the motif YGN was replaced by FGN. The OXA-24 β-lactamase hydrolyzed benzylpenicillin and cephaloridine but lacked activity against oxacillin, cloxacillin, and methicillin. The enzymatic activity was inhibited by chloride ions and by tazobactam (50% inhibitory concentration [IC
50
], 0.5 μM), sulbactam (IC
50
, 40 μM), and clavulanic acid (IC
50
, 50 μM). Carbapenem MICs for an
Escherichia coli
transformant (pBMB-1) expressing the cloned OXA-24 enzyme had a fourfold increase. Relative
V
max
/

K
m

values of 13 and 6 were obtained with imipenem and meropenem, respectively, and a positive microbiological assay result with imipenem was obtained with a purified enzymatic extract of this transformant strain. Therefore, we consider this new β-lactamase to be involved in the carbapenem resistance of
A. baumannii
RYC 52763/97.
Pharmacokinetics of Zidovudine Phosphorylation in Human Immunodeficiency Virus-Positive Thai Patients and Healthy Volunteers
Authors: Wattanagoon Yupaporn , Na Bangchang Kesara , Hoggard Patrick G. , Khoo Saye H. , Gibbons Sara E. , Phiboonbhanakit Danabhand , Karbwang Juntra , Back David J. 
Published: July 2002

ABSTRACT

We assessed the pharmacokinetics of zidovudine (ZDV) in plasma and intracellular ZDV phosphate anabolites in peripheral blood mononuclear cells in Thai human immunodeficiency virus (HIV) type 1-infected patients and healthy volunteers. The plasma ZDV area under the concentration-time curve from 0 to 6 h (AUC
0–6
) was similar in patients and healthy volunteers (32.77 and 22.77 μmol/liter · h, respectively; confidence interval, −3.37 to 19.92). Although the concentration of ZDV triphosphate (ZDVTP) was similar in the two groups, the ZDV monophosphate (ZDVMP) AUC
0–6
was significantly greater in HIV patients (1.12 pmol/10
6
cells) than in healthy volunteers (0.15 pmol/10
6
cells). In agreement with previously published data obtained with Caucasians, the significant difference in intracellular phosphorylation in Thai volunteers and HIV patients is primarily due to ZDVMP. Comparing the data from this study with the data obtained with Caucasians suggests no marked ethnic differences in ZDV phosphorylation.
Activity of Moxifloxacin by Itself and in Combination with Ethambutol, Rifabutin, and Azithromycin In Vitro and In Vivo against
Mycobacterium avium
Authors: Bermudez Luiz E. , Inderlied Clark B. , Kolonoski Peter , Petrofsky Mary , Aralar Priscilla , Wu Martin , Young Lowell S. 
Published: July 2002

ABSTRACT

Moxifloxacin activity against
Mycobacterium avium
complex (MAC) was evaluated in vitro against 25 strains. The MIC was determined to range from 0.125 to 2.0 μg/ml. In addition, U937 macrophage monolayers infected with MAC strain 101 (serovar 1) were treated with moxifloxacin (0.25 to 8 μg/ml) daily, and the number of intracellular bacteria was quantitated after 4 days. Moxifloxacin showed inhibitory activity at 0.5 μg/ml and higher. To assess the activity of moxifloxacin containing regimens in vivo, we infected C57BL
bg
+
/
bg
+
mice with 3 × 10
7
MAC strain 101 bacteria intravenously. One week later treatment was begun with the following: (i) moxifloxacin (50 mg/kg/day or 100 mg/kg/day), ethambutol (100 mg/kg/day), or a combination of moxifloxacin and ethambutol; or (ii) moxifloxacin (100 mg/kg/day), azithromycin (200 mg/kg/day), or rifabutin (40 mg/kg/day) as oral monotherapy; or (iii) all permutations of two-drug therapy or all three drugs in combination. All groups contained at least 14 animals, and the control group received the drug vehicle. After 4 weeks, quantitative blood cultures were obtained and the number of bacteria in liver and spleen was quantitated. Moxifloxacin, ethambutol, and azithromycin were active as single agents in liver, spleen, and blood. Rifabutin showed inhibitory activity only in the blood. Two-drug combinations containing azithromycin were no more active than azithromycin alone. Similarly, the three-drug combination was not more active than azithromycin alone in the spleen. Rifabutin did not add to the activity of any other single agent or two-drug combination. Moxifloxacin at both concentrations in combination with ethambutol was significantly more active than each drug alone.
Antimalarial Drugs Clear Resistant Parasites from Partially Immune Hosts
Authors: Cravo Pedro , Culleton Richard , Hunt Paul , Walliker David , Mackinnon Margaret J. 
Published: July 2002

ABSTRACT

Circumstantial evidence in human malaria suggests that elimination of parasites by drug treatment meets higher success rates in individuals having some background immunity. In this study, using the rodent malaria model
Plasmodium chabaudi
, we show that drug-resistant parasites can be cleared by drugs when the host is partially immune.
Streptococcus pneumoniae
Isolates with Reduced Susceptibility to Ciprofloxacin in Spain: Clonal Diversity and Appearance of Ciprofloxacin-Resistant Epidemic Clones
Authors: Alou Luis , Ramirez Mario , Garcı́a-Rey César , Prieto José , de Lencastre Hermı́nia 
Published: July 2002

ABSTRACT
Analysis of the pulsed-field gel electrophoretic profiles of 82 pneumococcal isolates with reduced susceptibility to ciprofloxacin (RSC) and of 90 co-occurring susceptible isolates indicates a considerable genetic diversity among isolates with RCS and points to a close relation between the two groups. This finding suggests that pneumococci with RCS emerge through independent mutational events.
Circulating Metabolites of the Human Immunodeficiency Virus Protease Inhibitor Nelfinavir in Humans: Structural Identification, Levels in Plasma, and Antiviral Activities
Authors: Zhang Kanyin E. , Wu Ellen , Patick Amy K. , Kerr Bradley , Zorbas Mark , Lankford Angela , Kobayashi Takuo , Maeda Yuki , Shetty Bhasker , Webber Stephanie 
Published: July 2002

ABSTRACT

Nelfinavir mesylate (Viracept, formally AG1343) is a potent and orally bioavailable human immunodeficiency virus (HIV) type 1 (HIV-1) protease inhibitor (
K

i

= 2 nM) and is being widely prescribed in combination with HIV reverse transcriptase inhibitors for the treatment of HIV infection. The current studies evaluated the presence of metabolites circulating in plasma following the oral administration of nelfinavir to healthy volunteers and HIV-infected patients, as well as the levels in plasma and antiviral activities of these metabolites. The results showed that the parent drug was the major circulating chemical species, followed in decreasing abundance by its hydroxy-
t
-butylamide metabolite (M8) and 3′-methoxy-4′-hydroxynelfinavir (M1). Antiviral assays with HIV-1 strain RF-infected CEM-SS cells showed that the 50% effective concentrations (EC
50
) of nelfinavir, M8, and M1 were 30, 34, and 151 nM, respectively, and that the corresponding EC
50
against another HIV-1 strain, IIIB, in MT-2 cells were 60, 86, and 653 nM. Therefore, apparently similar in vitro antiviral activities were demonstrated for nelfinavir and M8, whereas an approximately 5- to 11-fold-lower level of antiviral activity was observed for M1. The active metabolite, M8, showed a degree of binding to human plasma proteins similar to that of nelfinavir (ca
.
98%). Concentrations in plasma of nelfinavir and its metabolites in 10 HIV-positive patients receiving nelfinavir therapy (750 mg three times per day) were determined by a liquid chromatography tandem mass spectrometry assay. At steady state (day 28), the mean plasma nelfinavir concentrations ranged from 1.73 to 4.96 μM and the M8 concentrations ranged from 0.55 to 1.96 μM, whereas the M1 concentrations were low and ranged from 0.09 to 0.19 μM. In conclusion, the findings from the current studies suggest that, in humans, nelfinavir forms an active metabolite circulating at appreciable levels in plasma. The active metabolite M8 may account for some of the antiviral activity associated with nelfinavir in the treatment of HIV disease.
In Vitro Activity of Clarithromycin against Intracellular
Helicobacter pylori
Authors: Piccolomini Raffaele , Di Bonaventura Giovanni , Picciani Carla , Laterza Francesco , Vecchiet Jacopo , Neri Matteo 
Published: July 2002

ABSTRACT

The in vitro intracellular effect of clarithromycin, amoxicillin, metronidazole, lansoprazole, and rifabutin, tested at concentrations corresponding to one times the MIC, two times the MIC, and four times the MIC, was evaluated against an invasive
Helicobacter pylori
strain. At four times the MIC, clarithromycin showed an early bactericidal effect within 4 h of incubation and, in determining the complete killing within a 16 h-incubation period, lansoprazole and rifabutin showed comparable activity, yielding bactericidal activities within 4 and 8 h of incubation, respectively. Amoxicillin and metronidazole showed bacteriostatic activity only.
PCR Assays That Identify the Grapevine Dieback FungusEutypa lata
Authors: Lecomte Pascal , Péros Jean-Pierre , Blancard Dominique , Bastien Nicolas , Délye Christophe 
Published: July 2002

ABSTRACTEutypa latais the causal fungal agent ofEutypadieback, a serious grapevine necrotic disease. The erratic and delayed (1 to 2 months) appearance of characteristic conidia on culture media and the presence of numerous microorganisms in decaying wood make it difficult either to identify or to detectE. latain grapevine wood samples. We designed six pairs of PCR primers for diagnosis ofE. lata. Three primer pairs were derived from ribosomal DNA internal transcribed spacer sequences, and three pairs were derived from randomly amplified polymorphic DNA fragments. The six primer pairs could be used to amplify DNAs extracted from all of theE. lataisolates tested. They did not amplify DNAs from fungi and bacteria representing more than 50 different species of microorganisms associated with grapevine. We developed a simple protocol, leading to a rapid release of DNA, that enabled us to identifyE. latafrom pure or mixed cultures as well as from grapevine wood samples. Identification ofE. latain wood was achieved within a few hours, instead of the several weeks required for classical cultures on agar medium. We believe that the procedure described here can be adapted to detect other microorganisms involved in woody plant diseases.
Expression of the
Staphylococcus hyicus
Lipase in
Lactococcus lactis
Authors: Drouault Sophie , Corthier Gerard , Ehrlich S. Dusko , Renault Pierre 
Published: July 2002

ABSTRACT

The extracellular
Staphylococcus hyicus
lipase was expressed under the control of different promoters in
Lactococcus lactis
and
Bacillus subtilis
. Its expression at high and moderate levels is toxic for the former and the latter hosts, respectively. In
L. lactis
, the lipase was expressed at a high level, up to 30% of the total cellular proteins, under the control of the inducible promoter P
nisA
. About 80% of the lipase remained associated with the cells. Close to half of this amount remained associated with the inner side of the cytoplasmic membrane as unprocessed pre-pro-lipase. The other half was trapped by the cell wall and partially degraded at the N-terminal end. This result suggests that extracellular proteases degrade the lipase. Surprisingly, the kinetics and the pattern of lipase degradation were different in the two
L. lactis
subspecies,
L. lactis
subsp.
cremoris
and
L. lactis
subsp.
lactis
. The extracellular proteolytic systems that degrade lipase are thus different in these closely related subspecies. The incorrect export of the lipase is not due to an inappropriate leader peptide but may be due to an inefficiency of several steps of lipase secretion. We propose that (i) the
S. hyicus
lipase may require a special accessory system to be correctly exported or (ii) the kinetics of lipase synthesis may be a critical factor for proper folding.
Quantification of
Hyphomicrobium
Populations in Activated Sludge from an Industrial Wastewater Treatment System as Determined by 16S rRNA Analysis
Authors: Layton A. C. , Karanth P. N. , Lajoie C. A. , Meyers A. J. , Gregory I. R. , Stapleton R. D. , Taylor D. E. , Sayler G. S. 
Published: July 2002

ABSTRACT

The bacterial community structure of the activated sludge from a 25 million-gal-per-day industrial wastewater treatment plant was investigated using rRNA analysis. 16S ribosomal DNA (rDNA) libraries were created from three sludge samples taken on different dates. Partial rRNA gene sequences were obtained for 46 rDNA clones, and nearly complete 16S rRNA sequences were obtained for 18 clones. Seventeen of these clones were members of the beta subdivision, and their sequences showed high homology to sequences of known bacterial species as well as published 16S rDNA sequences from other activated sludge sources. Sixteen clones belonged to the alpha subdivision, 7 of which showed similarity to
Hyphomicrobium
species. This cluster was chosen for further studies due to earlier work on
Hyphomicrobium
sp. strain M3 isolated from this treatment plant. A nearly full-length 16S rDNA sequence was obtained from
Hyphomicrobium
sp. strain M3. Phylogenetic analysis revealed that
Hyphomicrobium
sp. strain M3 was 99% similar to
Hyphomicrobium denitrificans
DSM 1869
T
in
Hyphomicrobium
cluster II. Three of the cloned sequences from the activated sludge samples also grouped with those of
Hyphomicrobium
cluster II, with a 96% sequence similarity to that of
Hyphomicrobium
sp. strain M3. The other four cloned sequences from the activated sludge sample were more closely related to those of the
Hyphomicrobium
cluster I organisms (95 to 97% similarity). Whole-cell fluorescence hybridization of microorganisms in the activated sludge with genus-specific
Hyphomicrobium
probe S-G-Hypho-1241-a-A-19 enhanced the visualization of
Hyphomicrobium
and revealed that
Hyphomicrobium
appears to be abundant both on the outside of flocs and within the floc structure. Dot blot hybridization of activated sludge samples from 1995 with probes designed for
Hyphomicrobium
cluster I and
Hyphomicrobium
cluster II indicated that
Hyphomicrobium
cluster II-positive 16S rRNA dominated over
Hyphomicrobium
cluster I-positive 16S rRNA by 3- to 12-fold.
Hyphomicrobium
16S rRNA comprised approximately 5% of the 16S rRNA in the activated sludge.
Comparison of
Cryptosporidium parvum
Viability and Infectivity Assays following Ozone Treatment of Oocysts
Authors: Bukhari Z. , Marshall M. M. , Korich D. G. , Fricker C. R. , Smith H. V. , Rosen J. , Clancy J. L. 
Published: July 2002

ABSTRACT

Several in vitro surrogates have been developed as convenient, user-friendly alternatives to mouse infectivity assays for determining the viability of
Cryptosporidium parvum
oocysts. Such viability assays have been used increasingly to determine oocyst inactivation following treatment with chemical, physical, or environmental stresses. Defining the relationship between in vitro viability assays and oocyst infectivity in susceptible hosts is critical for determining the significance of existing oocyst inactivation data for these in vitro assays and their suitability in future studies. In this study, four viability assays were compared with mouse infectivity assays, using neonatal CD-1 mice. Studies were conducted in the United States and United Kingdom using fresh (<1 month) or environmentally aged (3 months at 4°C) oocysts, which were partially inactivated by ozonation before viability and/or infectivity analyses. High levels of variability were noted within and between the viability and infectivity assays in the U.S. and United Kingdom studies despite rigorous control over oocyst conditions and disinfection experiments. Based on the viability analysis of oocyst subsamples from each ozonation experiment, SYTO-59 assays demonstrated minimal change in oocyst viability, whereas 4′,6′-diamidino-2-phenylindole–propidium iodide assays, in vitro excystation, and SYTO-9 assays showed a marginal reduction in oocyst viability. In contrast, the neonatal mouse infectivity assay demonstrated significantly higher levels of oocyst inactivation in the U.S. and United Kingdom experiments. These comparisons illustrate that four in vitro viability assays cannot be used to reliably predict oocyst inactivation following treatment with low levels of ozone. Neonatal mouse infectivity assays should continue to be regarded as a “gold standard” until suitable alternative viability surrogates are identified for disinfection studies.
Glucose Uptake in
Clostridium beijerinckii
NCIMB 8052 and the Solvent-Hyperproducing Mutant BA101
Authors: Lee Jieun , Blaschek H. P. 
Published: July 2002

ABSTRACT

Glucose uptake and accumulation by
Clostridium beijerinckii
BA101, a butanol hyperproducing mutant, were examined during various stages of growth. Glucose uptake in
C. beijerinckii
BA101 was repressed 20% by 2-deoxyglucose and 25% by mannose, while glucose uptake in
C. beijerinckii
8052 was repressed 52 and 28% by these sugars, respectively. We confirmed the presence of a phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) associated with cell extracts of
C. beijerinckii
BA101 by glucose phosphorylation by PEP. The PTS activity associated with
C. beijerinckii
BA101 was 50% of that observed for
C. beijerinckii
8052.
C. beijerinckii
BA101 also demonstrated lower PTS activity for fructose and glucitol. Glucose phosphorylation by cell extracts derived from both
C. beijerinckii
BA101 and 8052 was also dependent on the presence of ATP, a finding consistent with the presence of glucokinase activity in
C. beijerinckii
extracts. ATP-dependent glucose phosphorylation was predominant during the solventogenic stage, when PEP-dependent glucose phosphorylation was dramatically repressed. A nearly twofold-greater ATP-dependent phosphorylation rate was observed for solventogenic stage
C. beijerinckii
BA101 than for solventogenic stage
C. beijerinckii
8052. These results suggest that
C. beijerinckii
BA101 is defective in PTS activity and that
C. beijerinckii
BA101 compensates for this defect with enhanced glucokinase activity, resulting in an ability to transport and utilize glucose during the solventogenic stage.
Oxidative Transformation of Aminodinitrotoluene Isomers by Multicomponent Dioxygenases
Authors: Johnson Glenn R. , Smets Barth F. , Spain Jim C. 
Published: July 2002

ABSTRACT
The electron-withdrawing nitro substituents of 2,4,6-trinitrotoluene (TNT) make the aromatic ring highly resistant to oxidative transformation. The typical biological transformation of TNT involves reduction of one or more of the nitro groups of the ring to produce the corresponding amine. Reduction of a single nitro substituent of TNT to an amino substituent increases the electron density of the aromatic nucleus considerably. The comparatively electron-dense nuclei of the aminodinitrotoluene (ADNT) isomers would be expected to be more susceptible to oxygenase attack than TNT. The hypothesis was tested by evaluating three nitroarene dioxygenases for the ability to hydroxylate the ADNT isomers. The predominant reaction was dioxygenation of the ring to yield nitrite and the corresponding aminomethylnitrocatechol. A secondary reaction was benzylic monooxygenation to form aminodinitrobenzyl alcohol. The substrate preferences and catalytic specificities of the three enzymes differed considerably. The discovery that the ADNT isomers are substrates for the nitroarene dioxygenases reveals the potential for extensive bacterial transformation of TNT under aerobic conditions.