bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fungicidal Synergism of Fluconazole and Cyclosporine in
Candida albicans
Is Not Dependent on Multidrug Efflux Transporters Encoded by the
CDR1
,
CDR2
,
CaMDR1
, and
FLU1
Genes
Authors: Marchetti Oscar , Moreillon Philippe , Entenza Josè M. , Vouillamoz Jacques , Glauser Michel P. , Bille Jacques , Sanglard Dominique 
Published: April 2003

ABSTRACT

The combination of fluconazole (FLC) and cyclosporine (CY) is fungicidal in FLC-susceptible
C. albicans
(O. Marchetti, P. Moreillon, M. P. Glauser, J. Bille, and D. Sanglard, Antimicrob. Agents Chemother. 44:2373-2381, 2000). The mechanism of this synergism is unknown. CY has several cellular targets including multidrug efflux transporters. The hypothesis that CY might inhibit FLC efflux was investigated by comparing the effect of FLC-CY in FLC-susceptible parent CAF2-1 (FLC MIC, 0.25 mg/liter) and in FLC-hypersusceptible mutant DSY1024 (FLC MIC, 0.03 mg/liter), in which the
CDR1
,
CDR2
,
CaMDR1
, and
FLU1
transporter genes have been selectively deleted. We postulated that a loss of the fungicidal effect of FLC-CY in DSY1024 would confirm the roles of these efflux pumps. Time-kill curve studies showed a more potent fungistatic effect of FLC (
P
= 0.05 at 48 h with an inoculum of 10
3
CFU/ml) and a more rapid fungicidal effect of FLC-CY (
P
= 0.05 at 24 h with an inoculum of 10
3
CFU/ml) in the FLC-hypersusceptible mutant compared to those in the parent. Rats with experimental endocarditis were treated for 2 or 5 days with high-dose FLC, high-dose CY, or both drugs combined. FLC monotherapy for 5 days was more effective against the hypersusceptible mutant than against the parent. However, the addition of CY to FLC still conferred a therapeutic advantage in animals infected with mutant DSY1024, as indicated by better survival (
P
= 0.04 versus the results obtained with FLC) and sterilization of valves and kidneys after a very short (2-day) treatment (
P
= 0.009 and 0.002, respectively, versus the results obtained with FLC). Both in vitro and in vivo experiments consistently showed that the deletion of the four membrane transporters in DSY1024 did not result in loss of the fungicidal effect of FLC-CY. Yet, the accelerated killing in the mutant suggested a “dual-hit” mechanism involving FLC hypersusceptibility due to the efflux pump elimination and fungicidal activity conferred by CY. Thus, inhibition of multidrug efflux transporters encoded by
CDR1
,
CDR2
,
CaMDR1
, and
FLU1
genes is not responsible for the fungicidal synergism of FLC-CY. Other cellular targets must be considered.
Presence of a
vanA
-Carrying Pheromone Response Plasmid (pBRG1) in a Clinical Isolate of
Enterococcus faecium
Authors: Magi Gloria , Capretti Roberta , Paoletti Claudia , Pietrella Marco , Ferrante Luigi , Biavasco Francesca , Varaldo Pietro Emanuele , Facinelli Bruna 
Published: April 2003

ABSTRACT

Sex pheromone plasmids, frequently found in
Enterococcus faecalis
, have rarely been detected in
Enterococcus faecium
. pBRG1 is an approximately 50-kb
vanA
-carrying conjugative plasmid of an
E. faecium
clinical isolate (LS10) that is transferable to
E. faecalis
laboratory strains. In cell infection experiments,
E. faecium
LS10 exhibited remarkably high invasion efficiency and produced cytopathogenic effects in Caco-2 cell monolayers. Growth in the presence of sex pheromones produced by
E. faecalis
JH2-2 was found to cause self-aggregation of both
E. faecium
LS10 and
E. faecalis
JH-RFV(pBRG1) (a transconjugant obtained by transfer of pBRG1 to
E. faecalis
JH2-2) and to increase the cell adhesion and invasion efficiencies of both
E. faecium
LS10 and
E. faecalis
JH-RFV(pBRG1). Sex pheromone cCF10 caused clumping of
E. faecalis
OG1RF(pBRG1) (a transconjugant obtained by transfer of pBRG1 to
E. faecalis
OG1RF) at a concentration ∼100-fold higher than the one required for the control strain
E. faecalis
OG1RF(pCF10). PCR products of the expected sizes were obtained with primers internal to aggregation substance genes of
E. faecalis
pheromone response plasmids pAD1, pPD1, and pCF10 and primers internal to
ash701
of
E. faecium
pheromone plasmid pHKK701. These findings suggest that pBRG1 of
E. faecium
LS10 is a sex pheromone response plasmid.
Aminoglycoside Resistance Resulting from Tight Drug Binding to an Altered Aminoglycoside Acetyltransferase
Authors: Magnet Sophie , Smith Terry-Ann , Zheng Renjian , Nordmann Patrice , Blanchard John S. 
Published: April 2003

ABSTRACT

The
aacA29b
gene, which confers an atypical aminoglycoside resistance pattern to
Escherichia coli
, was identified on a class 1 integron from a multidrug-resistant isolate of
Pseudomonas aeruginosa
. On the basis of amino acid sequence homology, it was proposed that the gene encoded a 6′-
N
-acetyltransferase. The resistance gene was cloned into the pET23a(+) vector, and overexpression conferred high-level resistance to the usual substrates of the aminoglycoside
N-
acetyltransferase AAC(6′)-I, except netilmicin. The level of resistance conferred by
aacA29b
correlated perfectly with the level of expression of the gene. The corresponding C-terminal six-His-tagged AAC(6′)-29b protein was purified and found to exist as a dimer in solution. With a spectrophotometric assay, an extremely feeble AAC activity was detected with acetyl coenzyme A (acetyl-CoA) as an acetyl donor. Fluorescence titrations of the protein with aminoglycosides demonstrated the very tight binding of tobramycin, dibekacin, kanamycin A, sisomicin (

K
d

, ≤1 μM) and a weaker affinity for amikacin (

K
d

, ≈60 μM). The binding of netilmicin and acetyl-CoA could not be detected by either fluorescence spectroscopy or isothermal titration calorimetry. The inability of AAC(6′)-29b to efficiently bind acetyl-CoA is supported by an alignment analysis of its amino acid sequence compared with those of other AAC(6′)-I family members. AAC(6′)-29b lacks a number of residues involved in acetyl-CoA binding. These results lead to the conclusion that AAC(6′)-29b is able to confer aminoglycoside resistance by sequestering the drug as a result of tight binding.
Aminoglycoside Resistance Gene
ant(4′)-IIb
of
Pseudomonas aeruginosa
BM4492, a Clinical Isolate from Bulgaria
Authors: Sabtcheva Stefana , Galimand Marc , Gerbaud Guy , Courvalin Patrice , Lambert Thierry 
Published: April 2003

ABSTRACT

The
ant(4′)-IIb
gene of
Pseudomonas aeruginosa
BM4492, which encodes an aminoglycoside 4′-
O
-adenylyltransferase, was identified as a coding sequence of 756 bp corresponding to a protein with a calculated mass of 27,219 Da. Analysis of the deduced sequence indicated that the protein was related to aminoglycoside 4′-
O
-adenylyltransferases IIa and Ia found in
P. aeruginosa
and gram-positive bacteria, respectively. The enzyme conferred resistance to amikacin and tobramycin but not to dibekacin, gentamicin, or netilmicin. The
ant(4′)-IIb
gene had a chromosomal location in five of six clinical isolates of
P. aeruginosa
tested and was plasmid borne in the remaining strain. The
ant(4′)-IIb
gene was detected by PCR in some clinical strains of
P. aeruginosa
from the same hospital but not in members of other bacterial genera.
Lysostaphin Cream Eradicates
Staphylococcus aureus
Nasal Colonization in a Cotton Rat Model
Authors: Kokai-Kun John F. , Walsh Scott M. , Chanturiya Tanya , Mond James J. 
Published: April 2003

ABSTRACT

The anterior nares are a primary ecologic niche for
Staphylococcus aureus
, and nasal colonization by this opportunistic pathogen increases the risk of development of
S. aureus
infection. Clearance of
S. aureus
nasal colonization greatly reduces this risk. Mupirocin ointment is the current standard of care for clearance of
S. aureus
nasal colonization, but resistance to this antibiotic is emerging. Lysostaphin is a glycylglycine endopeptidase which specifically cleaves the cross-linking pentaglycine bridges in the cell walls of staphylococci. Lysostaphin is extremely staphylocidal (MIC at which 90% of isolates are inhibited, 0.001 to 0.064 μg/ml) and rapidly lyses both actively growing and quiescent
S. aureus
. This study demonstrates that a single application of 0.5% lysostaphin (actual dose, ∼150 μg of lysostaphin), formulated in a petrolatum-based cream, dramatically reduces
S. aureus
nasal colonization in 100% of animals tested and eradicates
S. aureus
nasal colonization in 93% of animals in a cotton rat model. A single dose of lysostaphin cream is more effective than a single dose of mupirocin ointment in eradicating
S. aureus
nasal colonization in this animal model. The lantibiotic peptide nisin, which has potent in vitro antistaphylococcal activity, was ineffective in reducing staphylococcal nasal carriage in this model. Nasal colonization was not reduced after three treatments with 5% nisin (∼1,500 μg/dose) in any of the treated animals. Lysostaphin formulated in cream may prove to be a superior alternative to mupirocin ointment for clearance of
S. aureus
nasal colonization.
Daptomycin Dose-Effect Relationship against Resistant Gram-Positive Organisms
Authors: Cha Raymond , Grucz Richard G. , Rybak Michael J. 
Published: April 2003

ABSTRACT

Daptomycin exhibits in vitro bactericidal activity against clinically significant gram-positive bacteria. We employed pharmacodynamic modeling to determine a once-daily dosing regimen of daptomycin that correlates to pharmacodynamic endpoints for different resistant gram-positive clinical strains. An in vitro pharmacodynamic model with an initial inoculum of 6 log
10
CFU/ml was used to simulate daptomycin regimens ranging in dose from 0 to 9 mg/kg of body weight/day, with corresponding exposures reflecting free-daptomycin concentrations in serum. Bacterial density was profiled over 48 h for two methicillin-resistant
Staphylococcus aureus
(MRSA-67 and -R515), two glycopeptide intermediate-resistant
S. aureus
(GISA-992 and -147398), and two vancomycin-resistant
Enterococcus faecium
(VREF-12366 and -SF12047) strains. A sigmoid dose-response model was used to estimate the effective dose required to achieve 50% (ED
50
) and 80% (ED
80
) bacterial density reduction at 48 h. Daptomycin MICs for study isolates ranged from 0.125 to 4 μg/ml. Model fitting resulted in an
r
2
of >0.80 for all tested isolates. Control growths at 48 h ranged from 7.3 to 8.5 log
10
CFU/ml. Sigmoid relationships were not superimposable between categorical resistant species: ED
50
and ED
80
values were 1.9 and 3.1, 4.2 and 5.6, and 5.4 and 6.8 mg/kg for MRSA, GISA, and VREF isolates, respectively. Doses required to achieve ED
50
and ED
80
values correlated with MIC differences between tested organisms. Corresponding area under the concentration-time curve from 0 to 24 h/MIC exposure ratios demonstrated a wide range of ED
80
values among the tested isolates. Doses ranging between 3 and 7 mg/kg produced significant bactericidal activity (ED
80
) against these multidrug-resistant
S. aureus
and
E. faecium
isolates.
In Vitro Pharmacodynamic Evaluation of the Mutant Selection Window Hypothesis Using Four Fluoroquinolones against
Staphylococcus aureus
Authors: Firsov Alexander A. , Vostrov Sergey N. , Lubenko Irene Y. , Drlica Karl , Portnoy Yury A. , Zinner Stephen H. 
Published: April 2003

ABSTRACT

To study the hypothesis of the mutant selection window (MSW) in a pharmacodynamic context, the susceptibility of a clinical isolate of methicillin-resistant
Staphylococcus aureus
exposed to moxifloxacin (MOX), gatifloxacin (GAT), levofloxacin (LEV), and ciprofloxacin (CIP) was tested daily by using an in vitro dynamic model that simulates human pharmacokinetics. A series of monoexponential pharmacokinetic profiles that mimic once-daily administration of MOX (half-life, 12 h), GAT (half-life, 7 h), and LEV (half-life, 6.8 h) and twice-daily administration of CIP (half-life, 4 h) provided peak concentrations (
C
max
) that either equaled the MIC, fell between the MIC and the mutant prevention concentration (MPC) (i.e., within or “inside” the MSW), or exceeded the MPC. The respective ratios of the area under the curve (AUC) over a 24-h dosing interval (AUC
24
) to the MIC varied from 13 to 244 h, and the starting inoculum was 10
8
CFU/ml (6 × 10
9
CFU per 60-ml central compartment). With all four quinolones, the greatest increases in MIC were observed at those AUC
24
/MIC values (from 24 to 62 h) that corresponded to quinolone concentrations within the MSW over most of the dosing interval (>20%). Less-pronounced increases in MIC were associated with the smallest simulated AUC
24
/MIC values (15 to 16 h) of GAT and CIP, whose
C
max
exceeded the MICs. No such increases were observed with the smallest AUC
24
/MIC values (13 to 17 h) of MOX and LEV, whose
C
max
were close to the MICs. Also, less pronounced but significant increases in MIC occurred at AUC
24
/MIC values (107 to 123 h) that correspond to quinolone concentrations partly overlapping the MIC-to-MPC range. With all four drugs, no change in MIC was seen at the highest AUC
24
/MIC values (201 to 244 h), where quinolone concentrations exceeded the MPC over most of the dosing interval. These “protective” AUC
24
/MIC ratios correspond to 66% of the usual clinical dose of MOX (400 mg), 190% of a 400-mg dose of GAT, 220% of a 500-mg dose of LEV, and 420% of two 500-mg doses of CIP. Thus, MOX may protect against resistance development at subtherapeutic doses, whereas GAT, LEV, and CIP provide similar effects only at doses that exceed their usual clinical doses. These data support the concept that resistant mutants are selectively enriched when antibiotic concentrations fall inside the MSW and suggest that in vitro dynamic models can be used to predict the relative abilities of quinolones to prevent mutant selection.
Antimicrobial and Immunologic Activities of Clarithromycin in a Murine Model of
Mycoplasma pneumoniae
-Induced Pneumonia
Authors: Hardy Robert D. , Rios Ana Maria , Chavez-Bueno Susana , Jafri Hasan S. , Hatfield Jeanine , Rogers Beverly B. , McCracken George H. , Ramilo Octavio 
Published: April 2003

ABSTRACT

Because macrolide antibiotics are hypothesized to possess immunomodulatory activity independent of their antimicrobial activity, we evaluated the immunomodulatory effect of clarithromycin in a murine model of lung inflammation induced by either live or UV-killed
Mycoplasma pneumoniae
. BALB/c mice were intranasally inoculated once with live or UV-killed
M
.
pneumoniae
. Clarithromycin (25 mg/kg of body weight) or placebo was subcutaneously administered once daily in both groups of mice. In mice infected with live
M
.
pneumoniae
, clarithromycin treatment significantly reduced quantitative
M
.
pneumoniae
bronchoalveolar lavage (BAL) culture, pulmonary histopathologic scores (HPS), and airway resistance-obstruction (as measured by plethysmography) compared with placebo. Concentrations of tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), mouse KC (functional IL-8), JE/MCP-1, and MIP-1α in BAL fluid were also significantly decreased in mice infected with live
M
.
pneumoniae
given clarithromycin. In contrast, mice inoculated with UV-killed
M
.
pneumoniae
had no significant reduction in HPS, airway resistance-obstruction, or BAL cytokine or chemokine concentrations in response to clarithromycin administration. Clarithromycin therapy demonstrated beneficial effects (microbiologic, histologic, respiratory, and immunologic) on pneumonia in the mice infected with live
M
.
pneumoniae
; this was not observed in the mice inoculated with UV-killed
M
.
pneumoniae
.
Moxifloxacin Efficacy and Vitreous Penetration in a Rabbit Model ofStaphylococcus aureusEndophthalmitis and Effect on Gene Expression of Leucotoxins and Virulence Regulator Factors
Authors: Bronner Stéphane , Jehl François , Peter Jean-Daniel , Ploy Marie-Cécile , Renault Corinne , Arvis Pierre , Monteil Henri , Prevost Gilles 
Published: April 2003

ABSTRACTBacterial endophthalmitis is a serious complication of ocular surgery and of eye trauma; the leading causative organisms areStaphylococcus aureusstrains. Tissue damage is due both to the host inflammatory response and to toxin synthesis by bacteria. Systemic treatment remains difficult because most antibiotics show poor ocular penetration. Moxifloxacin (MXF), a novel fluoroquinolone, was evaluated for its penetration into the vitreous of normal rabbit eyes and of eyes of rabbits infected for 24 h with methicillin-susceptible and methicillin-resistantS. aureus(MSSA and MRSA) following a single intravenous administration of 5 or 20 mg/kg. MXF penetration was rapid and efficient regardless of the dose, ranging from 28 to 52%. An inflammatory state of the vitreous significantly increased penetration after the 20-mg/kg dose, with penetration reaching 52%. Concentrations determined in the vitreous cavity following a 20-mg/kg administration showed a 3.5-fold decrease of the bacterial density within 5 h for MSSA (MIC, 0.125 μg/ml) and a 1.6-fold decrease for MRSA (MIC, 4 μg/ml) strains, respectively. By using a semiquantitative reverse transcription-PCR method, the expression ofluk-PVandhlgCB, but nothlgA, encoding staphylococcal leukotoxins, was detected in the vitreous without MXF treatment. A slight decrease in the expression of leucotoxins andsarA,agr, andsigBvirulence regulatory factors was observed 1 h following the administration of 5 mg of MXF per kg.
Pharmacodynamics of a Novel Des-F(6)-Quinolone, BMS-284756, against
Streptococcus
pneumoniae
in the Thigh Infection Model
Authors: Nicolau David P. , Mattoes Holly M. , Banevicius Maryanne , Xuan Dawei , Nightingale Charles H. 
Published: April 2003

ABSTRACT

BMS-284756 is a novel quinolone that lacks the six-position fluorine typical of existing compounds. Despite this structural change, BMS-284756 maintains potent antibacterial activity against gram-negative and gram-positive aerobic and anaerobic pathogens. The objective of this study was to define the pharmacodynamic profile of BMS-284756 against
Streptococcus
pneumoniae
. Protein binding in mice was assessed by the ultrafiltration method. For pharmacodynamic studies, neutropenic ICR mice were used, as well as an immunocompetent mouse species, CBA/J, in order to evaluate the impact of white blood cells on infection outcome. Mice were infected with 10
5
to 10
6
CFU per thigh, and therapy was initiated after 2 h. Animals received BMS-284756 orally over a range of 1.25 to 100 mg/kg/day divided into one to four doses. At 0 and 24 h postinfection, thighs were harvested for bacterial density measurement. Survival was assessed during 96 h of therapy and again at 3 days after therapy. Pharmacokinetic studies were also conducted with infected mice. Protein binding was determined to be 80%. The MICs for clinical isolates (
n
= 8) ranged from 0.03 to 2 μg/ml. The change in bacterial density and survival was correlated with the pharmacodynamic parameters percentage of time that the drug concentration in serum remains above the MIC, AUC (area under the concentration-time curve)/MIC ratio, and peak/MIC ratio, and the best predictor of response was the AUC/MIC ratio for both outcome measures. Total AUC/MIC ratios of 100 to 200 appear to result in maximal bactericidal effects. While a total AUC/MIC ratio exposure value of 100 (free AUC/MIC ratio, ∼20) resulted in nearly 100% survival at the conclusion of therapy, a total AUC/MIC ratio of 200 (free AUC/MIC ratio, ∼40) was required to ensure survival at 3 days posttherapy. These data demonstrate (i) the in vivo bactericidal activity of BMS-284756 against
S
.
pneumoniae
, (ii) that protein binding has a profound impact on the in vivo pharmacodynamic assessment of BMS-284756, and (iii) that an AUC/MIC ratio of 200 (free AUC/MIC ratio, ∼40) appears to best characterize the required dynamic exposure for optimization of bactericidal activity and maximal survival.
Shiga-Like Toxin II Impairs Hepatobiliary Transport of Doxorubicin in Rats by Down-Regulation of Hepatic P Glycoprotein and Multidrug Resistance-Associated Protein Mrp2
Authors: Hidemura Kazuhiko , Zhao Ying Lan , Ito Katsuki , Nakao Akimasa , Tatsumi Yasuaki , Kanazawa Hiroaki , Takagi Kenzo , Ohta Michio , Hasegawa Takaaki 
Published: April 2003

ABSTRACT

We investigated the effect of Shiga-like toxin II (SLT-II), derived from
Escherichia coli
O157:H7, on the hepatobiliary excretion of doxorubicin, a substrate for P glycoprotein and the multidrug resistance-associated protein Mrp2, and on the expression of P glycoprotein and Mrp2 in rats. Histopathological examination did not show any liver injury in SLT-II-treated rats. A significant delay in the disappearance of doxorubicin from plasma after its intravenous administration (5 mg/kg of body weight) was observed in rats treated 24 h earlier with SLT-II (2 μg/animal). When rats received an infusion of doxorubicin (2.6 μg/min) 24 h after intravenous injection of SLT-II, the steady-state concentration of doxorubicin in plasma increased and the bile flow decreased, whereas the concentration in liver did not alter. SLT-II significantly increased the unbound fraction of doxorubicin in plasma but did not alter the concentration in liver tissue. SLT-II significantly decreased the biliary excretion rate and biliary clearance of doxorubicin based on the total concentration and concentration of the unbound fraction in plasma and liver. Western blot analysis revealed that SLT-II down-regulated P glycoprotein and Mrp2 in the liver, which could explain the observed decrease in the biliary excretion of doxorubicin by SLT-II. A tumor necrosis factor alpha (TNF-α) production inhibitor, pentoxifylline, could not protect SLT-II-induced decreases in the biliary clearance of doxorubicin and down-regulation of both transporters. It is unlikely that TNF-α plays a major role in the SLT-II-induced decrease in the hepatobiliary transport of doxorubicin and the down-regulation of both transporters.
Pharmacokinetics-Pharmacodynamics of Cefepime and Piperacillin- Tazobactam against
Escherichia coli
and
Klebsiella pneumoniae
Strains Producing Extended-Spectrum β-Lactamases: Report from the ARREST Program
Authors: Ambrose P. G. , Bhavnani S. M. , Jones R. N. 
Published: April 2003

ABSTRACT

The frequency of resistance to β-lactams among nosocomial isolates has been increasing due to extended-spectrum β-lactamase (ESBL)-producing enteric bacilli. Although clinical outcome data are desirable, assessment of clinical efficacy has been limited due to the lack of a statistically meaningful number of well-documented cases. Since time above the MIC (
T
>MIC) is the pharmacokinetic-pharmacodynamic (PK-PD) measure that best correlates with in vivo activity of β-lactams, a stochastic model was used to predict the probability of PK-PD target attainment ranging from 30 (P30) to 70% (P70)
T
>MIC, for standard dosing regimens of both piperacillin-tazobactam and cefepime against
Escherichia coli
and
Klebsiella pneumoniae
ESBL phenotypes. The P70/30
T
>MIC for cefepime at 2 g every 12 h against
E. coli
and
K. pneumoniae
was 0.99/1.0 and 0.96/1.0 and for a regimen of 1 g every 12 h was 0.96/1.0 and 0.93/0.99, respectively. For piperacillin-tazobactam at 3.375 g every 4 h against
E. coli
and
K. pneumoniae
, the P70/30
T
>MIC was 0.77/0.96 and 0.48/0.77 and for a regimen of 3.375 g every 6 h was 0.28/0.91 and 0.16/0.69, respectively. These data suggest that the probability of achieving
T
>MIC target attainment rates is generally higher with cefepime than with piperacillin-tazobactam for present-day ESBL-producing strains when one uses contemporary dosing regimens.