bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Activity of Caspofungin Combined with Sulfamethoxazole against Clinical Isolates of
Aspergillus
spp
Authors: Yekutiel Aya , Shalit Itamar , Shadkchan Yona , Osherov Nir 
Published: August 2004

ABSTRACT

Caspofungin (CAS) inhibits fungal cell wall synthesis. Sulfamethoxazole (SMX) inhibits folate biosynthesis and is active in vitro against
Aspergillus
spp. We studied the activities of the combination of CAS and SMX against 31
Aspergillus
isolates and compared them with that of SMX combined with amphotericin B (AMB) or itraconazole (ITC). MICs and minimal effective concentrations (MECs) were determined by the NCCLS broth microdilution method. With MIC endpoints, the combination of SMX and CAS showed synergy or synergy to additivity against 29 of 31 isolates. With MEC endpoints, synergy to additivity was found against 12 of 31 isolates and indifference was displayed against the rest of them. SMX in combination with AMB or ITC was not truly synergistic, while synergy to additivity was found for SMX-AMB and SMX-ITC against 17 of 31 and 3 of 12 isolates, respectively. No antagonism was found with any of the drug combinations. Further analysis of the synergy of CAS and SMX was performed by detailed measurement of hyphal length by microscopy and time-dependent 2,3-bis(2-methoxy-4-nitro-5-[(sulfenylamino)carbonyl]-2
H
-tetrazolium hydroxide (XTT)-based hyphal damage experiments. With MEC endpoints, the combination of CAS and SMX was characterized by a greater than 50% decrease in hyphal length compared to the hyphal lengths achieved with double the concentration of each drug alone. The XTT-based hyphal damage studies showed a statistically significant (
P
< 0.05) reduction in viability with CAS and SMX in combination compared to the viabilities achieved with double the concentration of each drug alone. These findings support the synergy results found by using MIC endpoints and suggest that visual MEC measurements may not be sufficient to identify the synergistic interactions seen by more sensitive, quantitative methods. Animal models are required to validate the significance of the synergy of CAS and SMX against
Aspergillus
spp. observed in vitro.
Functional and Structural Characterization of the Genetic Environment of an Extended-Spectrum β-Lactamase
bla
VEB
Gene from a
Pseudomonas aeruginosa
Isolate Obtained in India
Authors: Aubert Daniel , Girlich Delphine , Naas Thierry , Nagarajan Shanta , Nordmann Patrice 
Published: August 2004

ABSTRACT

A
Pseudomonas aeruginosa
clinical strain isolated from a patient hospitalized in a New Delhi, India, hospital was resistant to expanded-spectrum cephalosporins, imipenem, and aztreonam. A
bla
VEB-1
-like gene named
bla
VEB-1a
, which codes for the extended-spectrum β-lactamase VEB-1a, was identified. The genetic environment of
bla
VEB-1a
was peculiar: (i) no 5′ conserved sequence (5′-CS) region was present upstream of the β-lactamase gene, whereas
bla
VEB-1
-like genes are usually associated with class 1 integrons; (ii)
bla
VEB-1a
was inserted between two truncated 3′-CS regions in a direct repeat; and (iii) four 135-bp repeated DNA sequences (repeated elements) were located on each side of the
bla
VEB-1a
gene. Expression of the
bla
VEB-1a
gene was driven by a strong promoter located in one of these repeated sequences. In addition, cloning of the β-lactamase content of this
P. aeruginosa
isolate followed by expression in
Escherichia coli
identified the naturally occurring AmpC β-lactamase and a gene encoding an OXA-2-like β-lactamase located in a class 1 integron, In78, in which an insertion sequence, IS
pa7
, was inserted within its 5′-CS region.
Penetration of
Candida
Biofilms by Antifungal Agents
Authors: Al-Fattani Mohammed A. , Douglas L. Julia 
Published: August 2004

ABSTRACT

A filter disk assay was used to investigate the penetration of antifungal agents through biofilms containing single and mixed-species biofilms containing
Candida
. Fluconazole permeated all single-species
Candida
biofilms more rapidly than flucytosine. The rates of diffusion of either drug through biofilms of three strains of
Candida albicans
were similar. However, the rates of drug diffusion through biofilms of
C. glabrata
or
C. krusei
were faster than those through biofilms of
C. parapsilosis
or
C. tropicalis
. In all cases, after 3 to 6 h the drug concentration at the distal edge of the biofilm was very high (many times the MIC). Nevertheless, drug penetration failed to produce complete killing of biofilm cells. These results indicate that poor antifungal penetration is not a major drug resistance mechanism for
Candida
biofilms. The abilities of flucytosine, fluconazole, amphotericin B, and voriconazole to penetrate mixed-species biofilms containing
C. albicans
and
Staphylococcus epidermidis
(a slime-producing wild-type strain, RP62A, and a slime-negative mutant, M7) were also investigated. All four antifungal agents diffused very slowly through these mixed-species biofilms. In most cases, diffusion was slower with biofilms containing
S. epidermidis
RP62A, but amphotericin B penetrated biofilms containing the M7 mutant more slowly. However, the drug concentrations reaching the distal edges of the biofilms always substantially exceeded the MIC. Thus, although the presence of bacteria and bacterial matrix material undoubtedly retarded the diffusion of the antifungal agents, poor penetration does not account for the drug resistance of
Candida
biofilm cells, even in these mixed-species biofilms.
Expression of the RND-Type Efflux Pump AdeABC in
Acinetobacter baumannii
Is Regulated by the AdeRS Two-Component System
Authors: Marchand Isabelle , Damier-Piolle Laurence , Courvalin Patrice , Lambert Thierry 
Published: August 2004

ABSTRACT

The AdeABC pump of
Acinetobacter baumannii
BM4454, which confers resistance to various antibiotic classes including aminoglycosides, is composed of the AdeA, AdeB, and AdeC proteins; AdeB is a member of the RND superfamily. The
adeA
,
adeB
, and
adeC
genes are contiguous and adjacent to
adeS
and
adeR
, which are transcribed in the opposite direction and which specify proteins homologous to sensors and regulators of two-component systems, respectively (S. Magnet, P. Courvalin, and T. Lambert, Antimicrob. Agents Chemother. 45:3375-3380, 2001). Analysis by Northern hybridization indicated that the three genes were cotranscribed, although mRNAs corresponding to
adeAB
and
adeC
were also present. Cotranscription of the two regulatory genes was demonstrated by reverse transcription-PCR. Inactivation of
adeS
led to aminoglycoside susceptibility. Transcripts corresponding to
adeAB
were not detected in susceptible
A. baumannii
CIP 70-10 but were present in spontaneous gentamicin-resistant mutants obtained in vitro. Analysis of these mutants revealed the substitutions Thr153→Met in AdeS downstream from the putative His-149 site of autophosphorylation, which is presumably responsible for the loss of phosphorylase activity by the sensor, and Pro116→Leu in AdeR at the first residue of the α
5
helix of the receiver domain, which is involved in interactions that control the output domain of response regulators. These mutations led to constitutive expression of the pump and, thus, to antibiotic resistance. These data indicate that the AdeABC pump is cryptic in wild
A. baumannii
due to stringent control by the AdeRS two-component system.
In Vitro Antimicrobial Susceptibilities of
Streptococcus pneumoniae
Clinical Isolates Obtained in Canada in 2002
Authors: Powis Jeff , McGeer Allison , Green Karen , Vanderkooi Otto , Weiss Karl , Zhanel George , Mazzulli Tony , Kuhn Magdalena , Church Deirdre , Davidson Ross , Forward Kevin , Hoban Daryl , Simor Andrew , Low Donald E. 
Published: August 2004

ABSTRACT

Empirical treatment is best guided by current surveillance of local resistance patterns. The goal of this study is to characterize the prevalence of antimicrobial nonsusceptibility within pneumococcal isolates from Canada. The Canadian Bacterial Surveillance Network is comprised of laboratories from across Canada. Laboratories collected a defined number of consecutive clinical and all sterile site isolates of
S. pneumoniae
in 2002. In vitro susceptibility testing was performed by broth microdilution with NCCLS guidelines. Rates of nonsusceptibility were compared to previously published reports from the same network. A total of 2,539 isolates were tested. Penicillin nonsusceptibility increased to 15% (8.5% intermediate, 6.5% resistant) compared to 12.4% in 2000 (
P
≤ 0.025, χ
2
). Only 32 (1.3%) isolates had an amoxicillin MIC of ≥4 μg/ml and only 2 of 32 cerebrospinal fluid isolates had an intermediate susceptibility to ceftriaxone by meningeal interpretive criteria (MIC = 1 μg/ml). A total of 354 (13.9%) isolates were macrolide nonsusceptible (46.3% MLS
B
, 56.7% M phenotype), increasing from 11.4% in 2000 (
P
≤ 0.0075, χ
2
). Only 13 (<1%) isolates had a telithromycin MIC of >1 μg/ml. Ciprofloxacin nonsusceptibility (defined as an MIC of ≥4 μg/ml) increased to 2.7% compared to 1.4% in 2000 (
P
≤ 0.0025, χ
2
) and was primarily found in persons ≥18 years old (98.5%). Nonsusceptibility to penicillin, macrolides, and fluoroquinolones is increasing in Canada. Nonsusceptibility to amoxicillin and ceftriaxone remains uncommon. Newer antimicrobials such as telithromycin and respiratory fluoroquinolones have excellent in vitro activity.
Posaconazole and Amphotericin B Combination Therapy against
Cryptococcus neoformans
Infection
Authors: Barchiesi Francesco , Spreghini Elisabetta , Schimizzi Anna M. , Maracci Monia , Giannini Daniele , Carle Flavia , Scalise Giorgio 
Published: August 2004

ABSTRACT

To investigate the effects of posaconazole (POS) and amphotericin B (AMB) combination therapy in cryptococcal infection, we established an experimental model of systemic cryptococcosis in CD1 mice by intravenous injection of three distinct clinical isolates of
Cryptococcus neoformans
. Therapy was started 24 h after the infection and continued for 10 consecutive days. POS was given at 3 and 10 mg/kg of body weight/day, while AMB was given at 0.3 mg/kg/day. Combination therapy consisted of POS given at a low (combo 3) or at a high (combo 10) dose plus AMB. Survival studies showed that combo 3 was significantly more effective than POS at 3 mg/kg for two isolates tested (
P
value, ≤0.001), while combo 10 was significantly more effective than POS at 10 mg/kg for all three isolates (
P
values ranging from <0.001 to 0.005). However, neither combination regimen was more effective than AMB alone. For two isolates, combination therapy was significantly more effective than each single drug at reducing the fungal burden in the brain (
P
values ranging from 0.001 to 0.015) but not in the lungs. This study demonstrates that the major impact of POS and AMB combination therapy is on brain fungal burden rather than on survival.
In Vitro Activities of Voriconazole in Combination with Three Other Antifungal Agents against
Candida glabrata
Authors: Barchiesi Francesco , Spreghini Elisabetta , Maracci Monia , Fothergill Annette W. , Baldassarri Isabella , Rinaldi Michael G. , Scalise Giorgio 
Published: August 2004

ABSTRACT

Candida glabrata
has recently emerged as a significant pathogen involved in both superficial and deep-seated infections. In the present study, a checkerboard broth microdilution method was performed to investigate the in vitro activities of voriconazole (VOR) in combination with terbinafine (TRB), amphotericin B (AMB), and flucytosine (5FC) against 20 clinical isolates of
C. glabrata
. Synergy, defined as a fractional inhibitory concentration (FIC) index of ≤0.50, was observed in 75% of VOR-TRB, 10% of VOR-AMB, and 5% of VOR-5FC interactions. None of these combinations yielded antagonistic interactions (FIC index > 4). When synergy was not achieved, there was still a decrease in the MIC of one or both drugs used in the combination. In particular, the MICs were reduced to ≤1.0 μg/ml as a result of the combination for all isolates for which the AMB MIC at the baseline was ≥2.0 μg/ml. By a disk diffusion assay, the halo diameters produced by antifungal agents in combination were greater that those produced by each drug alone. Finally, killing curves showed that VOR-AMB exhibited synergistic interactions, while VOR-5FC sustained fungicidal activities against
C. glabrata
. These studies demonstrate that the in vitro activity of VOR against this important yeast pathogen can be enhanced upon combination with other drugs that have different modes of action or that target a different step in the ergosterol pathway. Further studies are warranted to elucidate the potential beneficial effects of such combination regimens in vivo.
Double-Blind, Randomized Study of the Efficacy and Safety of Oral Pharmacokinetically Enhanced Amoxicillin-Clavulanate (2,000/125 Milligrams) versus Those of Amoxicillin-Clavulanate (875/125 Milligrams), Both Given Twice Daily for 7 Days, in Treatment of Bacterial Community-Acquired Pneumonia in Adults
Authors: File T. M. , Lode H. , Kurz H. , Kozak R. , Xie H. , Berkowitz E. 
Published: August 2004

ABSTRACT

This randomized, double-blind, noninferiority trial was designed to demonstrate that pharmacokinetically enhanced amoxicillin-clavulanate (2,000/125 mg) was at least as effective clinically as amoxicillin-clavulanate 875/125 mg, both given twice daily for 7 days, in the treatment of community-acquired pneumonia in adults. In total, 633 clinically and radiologically confirmed community-acquired pneumonia patients (intent-to-treat population) were randomized to receive either oral amoxicillin-clavulanate 2,000/125 mg (
n
= 322) or oral amoxicillin-clavulanate 875/125 mg (
n
= 311). At screening, 160 of 633 (25.3%) patients had at least one typical pathogen isolated from expectorated or invasive sputum samples or blood culture (bacteriology intent-to-treat population).
Streptococcus pneumoniae
(58 of 160, 36.3%), methicillin-susceptible
Staphylococcus aureus
(34 of 160, 21.3%), and
Haemophilus influenzae
(33 of 160, 20.6%) were the most common typical causative pathogens isolated in both groups in the bacteriology intent-to-treat population. Clinical success in the clinical per protocol population at test of cure (days 16 to 37), the primary efficacy endpoint, was 90.3% (223 of 247) for amoxicillin-clavulanate 2,000/125 mg and 87.6% (198 of 226) for amoxicillin-clavulanate 875/125 mg (treatment difference, 2.7; 95% confidence interval, −3.0, 8.3). Bacteriological success at test of cure in the bacteriology per protocol population was 86.6% (58 of 67) for amoxicillin-clavulanate 2,000/125 mg and 78.4% (40 of 51) for amoxicillin-clavulanate 875/125 mg (treatment difference, 8.1%; 95% confidence interval, −5.8, 22.1). Both therapies were well tolerated. Amoxicillin-clavulanate 2,000/125 mg twice daily was shown to be as clinically effective as amoxicillin-clavulanate 875/125 mg twice daily for 7 days in the treatment of adult patients with community-acquired pneumonia, without a noted increase in the reported rate of adverse events.
Plasmid-Encoded Multidrug Efflux Pump Conferring Resistance to Olaquindox in
Escherichia coli
Authors: Hansen Lars Hestbjerg , Johannesen Elsebetta , Burmølle Mette , Sørensen Anders Hay , Sørensen Søren J. 
Published: August 2004

ABSTRACT

We report here the first gene-encoded resistance mechanism to the swine growth enhancer olaquindox. The genetic elements involved in resistance to olaquindox were subcloned and sequenced from a conjugative plasmid isolated from
Escherichia coli
. The subcloned fragment contained two open reading frames,
oqxA
and
oqxB
, that are homologous to several resistance-nodulation-cell-division family efflux systems from different species. The putative protein sequences were aligned to both experimentally verified and putative efflux pumps. We show that
oqxA
and
oqxB
are expressed in
E. coli
. Plasmids containing the
oqxAB
genes yielded high (>128 μg/ml) resistance to olaquindox in
E. coli
, whereas strains containing the control plasmid showed low resistance to the drug (8 μg/ml). The
oqxAB
-encoded pump also conferred high (>64 μg/ml) resistance to chloramphenicol. We demonstrate that the subcloned fragment conferred H
+
-dependent ethidium efflux abilities to
E. coli
strain N43. In addition, we show that the efflux system is dependent on the host TolC outer membrane protein when expressed in
E. coli
.
In Vitro Activity of the New Quinolone WCK 771 against Staphylococci
Authors: Jacobs Michael R. , Bajaksouzian Saralee , Windau Anne , Appelbaum Peter C. , Patel Mahesh V. , Gupte Shrikant V. , Bhagwat Sachin S. , De Souza Noel J. , Khorakiwala Habil F. 
Published: August 2004

ABSTRACT

The activity of WCK 771, an experimental quinolone developed to overcome quinolone resistance in staphylococci and other bacteria, was determined against quinolone-susceptible and -resistant
Staphylococcus aureus
and
S. epidermidis
. WCK 771 MICs for 50 and 90% of the strains tested (MIC
50
and MIC
90
, respectively) were 0.008 and 0.015 μg/ml for
S. aureus
(
n
= 43) and 0.015 and 0.03 μg/ml for
S. epidermidis
(
n
= 44) for quinolone-susceptible isolates, compared to ciprofloxacin values of 0.12 and 0.25 μg/ml and 0.25 and 0.5 μg/ml, respectively. Values for levofloxacin were 0.12 and 0.25 μg/ml and 0.12 and 0.25 μg/ml, those for clinafloxacin were 0.015 and 0.03 μg/ml and 0.015 and 0.03 μg/ml, those for moxifloxacin were 0.03 and 0.06 μg/ml and 0.06 and 0.12 μg/ml, and those for gatifloxacin were 0.06 and 0.12 μg/ml and 0.12 and 0.25 μg/ml, respectively. The WCK 771 MIC
50
and MIC
90
, respectively, were 0.5 and 1 μg/ml for both species of staphylococci (
n
= 73 for
S. aureus
,
n
= 70 for
S. epidermidis
) for isolates highly resistant to ciprofloxacin (MIC
50
and MIC
90
, >32 and >32 μg/ml, respectively). Values for levofloxacin were 8 and 32 μg/ml and 8 and 32 μg/ml, those for clinafloxacin were 1 and 2 μg/ml and 0.5 and 2 μg/ml, those for moxifloxacin 4 and >4 μg/ml and 4 and >4 μg/ml, and those for gatifloxacin were 4 and >4 μg/ml and 2 and >4 μg/ml, respectively. WCK 771 and clinafloxacin demonstrated MICs of 1 μg/ml against three vancomycin-intermediate strains. WCK 771 showed concentration-independent killing for up to 24 h at 2, 4, and 8 times the MICs against quinolone-resistant staphylococci and was also bactericidal after 8 h for high-density inocula (10
8
CFU/ml) of quinolone-resistant strains at 5 μg/ml, whereas moxifloxacin at 7.5 μg/ml was bacteriostatic. WCK 771 was not a substrate of the NorA efflux pump as evident from the similar MICs against both an efflux-positive and an efflux-negative strain. Overall, WCK 771 was the most potent quinolone tested against the staphylococci tested, regardless of quinolone susceptibility.
Novel Murine Model of Pneumococcal Pneumonia: Use of Temperature as a Measure of Disease Severity To Compare the Efficacies of Moxifloxacin and Levofloxacin
Authors: Bast Darrin J. , Yue M. , Chen X. , Bell D. , Dresser L. , Saskin R. , Mandell L. A. , Low D. E. , de Azavedo Joyce C. S. 
Published: August 2004

ABSTRACT
Surface temperature measured by an infrared temperature-scanning thermometer was used to evaluate disease severity and predict imminent death in a murine model of pneumococcal pneumonia. We showed that a decrease in temperature was associated with increasing severity of disease and concomitant histological changes and also that a temperature of 30°C or less was a predictor of death. Furthermore, viable bacterial counts in the lungs of mice euthanized at a temperature of ≤ 30°C were not significantly different from those seen in the lungs of mice allowed to die without intervention. These data support temperature change as a more subtle indicator of outcome than death and demonstrate that this could be used as a reliable end point for euthanasia. To test the utility of our model in a drug trial, we examined the efficacies of moxifloxacin and levofloxacin by using temperature as a measure of disease severity prior to and during treatment. Regardless of the antibiotic used, mice assessed as moderately ill (temperature ≥ 32°C) at the start of treatment had better clinical and bacteriological outcomes than mice assessed as severely ill (temperature < 32°C). However, moxifloxacin offered better protection and greater bacterial clearance than did levofloxacin in all infected mice independent of disease severity. This model not only allows a more subtle evaluation of drug efficacy but also ensures a better degree of standardization and a more humane approach to drug efficacy studies involving animals.
Adherence of
Candida albicans
to Silicone Induces Immediate Enhanced Tolerance to Fluconazole
Authors: Mateus Carolina , Crow Sidney A. , Ahearn Donald G. 
Published: August 2004

ABSTRACT

Wild-type and efflux pump-deficient cells of
Candida albicans
adhering to silicone were compared with planktonic cells by flow cytometry for their relative resistance to fluconazole (FCZ). Flow cytometry data on cells carrying a fusion of green fluorescent protein to efflux pump promoters confirmed that enhanced tolerance of attached cells to FCZ was due in part to increased expression of
CaMDR1
and
CDR1
promoters. Within 2 h of their attachment to silicone, the adherent cells demonstrated levels of FCZ tolerance shown by cells from 24-h biofilms. Following their mechanical detachment, this subset of cells retained a four- to eightfold increase in tolerance compared with the tolerance of planktonic cells for at least two generations. Enhanced efflux pump tolerance to FCZ appeared to be induced within the initial 15 min of attachment in a subset of cells that were firmly attached to the substrata.
Human Tear Lipocalin Exhibits Antimicrobial Activity by Scavenging Microbial Siderophores
Authors: Fluckinger Maria , Haas Hubertus , Merschak Petra , Glasgow Ben J. , Redl Bernhard 
Published: August 2004

ABSTRACT
Human tear lipocalin (TL; also known as Lcn1) is a secretory protein present in large amounts in fluids that cover epithelial surfaces such as tears and respiratory secretions. It is supposed to act as a physiological scavenger of hydrophobic, potentially harmful molecules, but there is evidence that it also inhibits bacterial growth. In the present study, we reconsidered the possibility that TL might interfere with microbial growth by scavenging of siderophores, as described for human neutrophil gelatinase-associated lipocalin (NGAL). Indeed, our experiments revealed that TL binds to microbial siderophores with high affinities. In contrast to NGAL, which was shown to have some specificity for bacterial catecholate-type siderophores, TL binds to a broad array of siderophores, including bacterial catecholate-type enterobactin and hydroxamate-type desferrioxamine B, and all major classes of fungal siderophores. By adding exogenous TL, bacterial and fungal growth could be inhibited under iron-limiting conditions. Thus, TL might be a novel member of the innate immune system especially involved in mucosal defense against fungal infections.