bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro and In Vivo Activities of Nitazoxanide against
Clostridium difficile
Authors: McVay Catherine S. , Rolfe Rial D. 
Published: July 2002

ABSTRACT

We have used the hamster model of antibiotic-induced
Clostridium difficile
intestinal disease to evaluate nitazoxanide (NTZ), a nitrothiazole benzamide antimicrobial agent. The following in vitro and in vivo activities of NTZ in the adult hamster were examined and compared to those of metronidazole and vancomycin: (i) MICs and minimum bactericidal concentrations (MBCs) against
C. difficile
, (ii) toxicity, (iii) ability to prevent
C. difficile
-associated ileocecitis, and (iv) propensity to induce
C. difficile
-associated ileocecitis. The MICs and MBCs of NTZ against 15 toxigenic strains of
C. difficile
were comparable to those of vancomycin or metronidazole.
C. difficile
-associated ileocecitis was induced with oral clindamycin and toxigenic
C. difficile
in a group of 60 hamsters. Subgroups of 10 hamsters were given six daily intragastric treatments of NTZ (15, 7.5, and 3.0 mg/100 g of body weight [gbw]), metronidazole (15 mg/100 gbw), vancomycin (5 mg/100 gbw), or saline (1 ml/100 gbw). Animals receiving saline died 3 days post-
C. difficile
challenge. During the treatment period, NTZ (≥7.5 mg/100 gbw), like metronidazole and vancomycin, prevented outward manifestations of clindamycin-induced
C. difficile
intestinal disease. Six of ten hamsters on a scheduled dose of 3.0 mg of NTZ/100 gbw survived for the complete treatment period. Of these surviving animals, all but three died of
C. difficile
disease by between 3 and 12 days following discontinuation of antibiotic therapy. Another group of hamsters received six similar daily doses of the three antibiotics, followed by an inoculation with toxigenic
C. difficile
. All of the NTZ-treated animals survived the 15-day postinfection period. Upon necropsy, all hamsters appeared normal: there were no gross signs of toxicity or
C. difficile
intestinal disease, nor was
C. difficile
detected in the cultures of the ceca of these animals. By contrast, vancomycin and metronidazole treatment induced fatal
C. difficile
intestinal disease in 20 and 70% of recipients, respectively.
Characterization of the Extended-Spectrum β-Lactamase Reference Strain,
Klebsiella pneumoniae
K6 (ATCC 700603), Which Produces the Novel Enzyme SHV-18
Authors: Rasheed J. Kamile , Anderson Gregory J. , Yigit Hesna , Queenan Anne Marie , Doménech-Sánchez Antonio , Swenson Jana M. , Biddle James W. , Ferraro Mary Jane , Jacoby George A. , Tenover Fred C. 
Published: July 2002

ABSTRACT

Klebsiella pneumoniae
K6 (ATCC 700603), a clinical isolate, is resistant to ceftazidime and other oxyimino-β-lactams. A consistent reduction in the MICs of oxyimino-β-lactams by at least 3 twofold dilutions in the presence of clavulanic acid confirmed the utility of
K. pneumoniae
K6 as a quality control strain for extended-spectrum β-lactamase (ESBL) detection. Isoelectric-focusing analysis of crude lysates of K6 demonstrated a single β-lactamase with a pI of 7.8 and a substrate profile showing preferential hydrolysis of cefotaxime compared to ceftazidime. PCR analysis of total bacterial DNA from K6 identified the presence of a
bla
SHV
gene. K6 contained two large plasmids with molecular sizes of approximately 160 and 80 kb. Hybridization of plasmid DNA with a
bla
SHV
-specific probe indicated that a
bla
SHV
gene was encoded on the 80-kb plasmid, which was shown to transfer resistance to ceftazidime in conjugal mating experiments with
Escherichia coli
HB101. DNA sequencing of this
bla
SHV
-related gene revealed that it differs from
bla
SHV-1
at nine nucleotides, five of which resulted in amino acid substitutions: Ile to Phe at position 8, Arg to Ser at position 43, Gly to Ala at position 238, and Glu to Lys at position 240. In addition to the production of this novel ESBL, designated SHV-18, analysis of the outer membrane proteins of K6 revealed the loss of the OmpK35 and OmpK37 porins.
Pharmacokinetics of Levofloxacin and Ciprofloxacin during Continuous Renal Replacement Therapy in Critically Ill Patients
Authors: Malone Rebecca S. , Fish Douglas N. , Abraham Edward , Teitelbaum Isaac 
Published: July 2002

ABSTRACTThe pharmacokinetics of intravenously administered levofloxacin and ciprofloxacin were studied in intensive care unit patients during continuous venovenous hemofiltration (CVVH; four patients received levofloxacin, and five received ciprofloxacin) or hemodiafiltration (CVVHDF; six patients received levofloxacin, and five received ciprofloxacin). Levofloxacin clearance was substantially increased during both CVVH and CVVHDF, while ciprofloxacin clearance was affected less. The results of this study suggest that doses of levofloxacin of 250 mg/day and ciprofloxacin of 400 mg/day are sufficient to maintain effective drug concentrations in the plasma of patients undergoing CVVH or CVVHDF.
Rapamycin and Less Immunosuppressive Analogs Are Toxic to
Candida albicans
and
Cryptococcus neoformans
via FKBP12-Dependent Inhibition of TOR
Authors: Cruz M. Cristina , Goldstein Alan L. , Blankenship Jill , Del Poeta Maurizio , Perfect John R. , McCusker John H. , Bennani Youssef L. , Cardenas Maria E. , Heitman Joseph 
Published: July 2002

ABSTRACT

Candida albicans
and
Cryptococcus neoformans
cause both superficial and disseminated infections in humans. Current antifungal therapies for deep-seated infections are limited to amphotericin B, flucytosine, and azoles. A limitation is that commonly used azoles are fungistatic in vitro and in vivo. Our studies address the mechanisms of antifungal activity of the immunosuppressive drug rapamycin (sirolimus) and its analogs with decreased immunosuppressive activity.
C. albicans rbp1/rbp1
mutant strains lacking a homolog of the FK506-rapamycin target protein FKBP12 were found to be viable and resistant to rapamycin and its analogs. Rapamycin and analogs promoted FKBP12 binding to the wild-type Tor1 kinase but not to a rapamycin-resistant Tor1 mutant kinase (S1972R). FKBP12 and TOR mutations conferred resistance to rapamycin and its analogs in
C. albicans
,
C. neoformans
, and
Saccharomyces cerevisiae
. Our findings demonstrate the antifungal activity of rapamycin and rapamycin analogs is mediated via conserved complexes with FKBP12 and Tor kinase homologs in divergent yeasts. Taken together with our observations that rapamycin and its analogs are fungicidal and that spontaneous drug resistance occurs at a low rate, these mechanistic findings support continued investigation of rapamycin analogs as novel antifungal agents.
Sensitive Bioassay for Determination of Fluconazole Concentrations in Plasma Using a
Candida albicans
Mutant Hypersusceptible to Azoles
Authors: Marchetti Oscar , Majcherczyk Paul A. , Glauser Michel P. , Bille Jacques , Moreillon Philippe , Sanglard Dominique 
Published: July 2002

ABSTRACT

The antifungal agent fluconazole (FLC) is widely used in clinical practice. Monitoring FLC levels is useful in complicated clinical settings and in experimental infection models. A bioassay using
Candida pseudotropicalis
, a simple and cost-effective method, is validated only for FLC levels ranging from 5 to 40 mg/liter. An extension of the analytical range is needed to cover most yeast MICs. A new bioassay in RPMI agar containing methylene blue was developed using
C. albicans
DSY1024, a mutant rendered hypersusceptible to FLC constructed by the deletion of the multidrug efflux transporter genes
CDR1, CDR2, CaMDR1
, and
FLU1
. Reproducible standard curves were obtained with FLC concentrations in plasma ranging from 1 to 100 mg/liter (quadratic regression coefficient > 0.997). The absolute sensitivity was 0.026 μg of FLC. The method was internally validated according to current guidelines for analytical method validation. Both accuracy and precision lied in the required ±15% range. FLC levels measured by bioassay and by high-performance liquid chromatography (HPLC) performed with 62 plasma samples from humans and rats showed a strong correlation (coefficients, 0.979 and 0.995, respectively; percent deviations of bioassay from HPLC values, 0.44% ± 15.31% and 2.66% ± 7.54%, respectively). In summary, this newly developed bioassay is sensitive, simple, rapid, and inexpensive. It allows nonspecialized laboratories to determine FLC levels in plasma to within the clinically relevant concentration range and represents a useful tool for experimental treatment models.
In Vitro Pharmacodynamic Properties of Colistin and Colistin Methanesulfonate against
Pseudomonas aeruginosa
Isolates from Patients with Cystic Fibrosis
Authors: Li Jian , Turnidge John , Milne Robert , Nation Roger L. , Coulthard Kingsley 
Published: July 2002

ABSTRACT

The in vitro pharmacodynamic properties of colistin and colistin methanesulfonate were investigated by studying the MICs, time-kill kinetics, and postantibiotic effect (PAE) against mucoid and nonmucoid strains of
Pseudomonas aeruginosa
isolated from patients with cystic fibrosis. Twenty-three clinical strains, including multiresistant strains, and one type strain were selected for MIC determination. Eleven strains were resistant; MICs for these strains were >128 mg/liter. For the susceptible strains, MICs of colistin ranged from 1 to 4 mg/liter, while the MICs of colistin methanesulfonate were significantly higher and ranged from 4 to 16 mg/liter. The time-kill kinetics were investigated with three strains at drug concentrations ranging from 0.5 to 64 times the MIC. Colistin showed extremely rapid killing, resulting in complete elimination at the highest concentrations within 5 min, while colistin methanesulfonate killed more slowly, requiring a concentration of 16 times the MIC to achieve complete killing within 24 h. Colistin exhibited a significant PAE of 2 to 3 h at 16 times the MIC against the three strains after 15 min of exposure. For colistin methanesulfonate, PAEs were shorter at the concentrations tested. Colistin methanesulfonate had lower overall bactericidal and postantibiotic activities than colistin, even when adjusted for differences in MICs. Our data suggest that doses of colistin methanesulfonate higher than the recommended 2 to 3 mg/kg of body weight every 12 h may be required for the effective treatment of
P. aeruginosa
infections in cystic fibrosis patients.
Real-Time PCR and Melting Curve Analysis for Reliable and Rapid Detection of SHV Extended-Spectrum β-Lactamases
Authors: Randegger Corinne C. , Hächler Herbert 
Published: July 2002

ABSTRACT

Extended-spectrum β-lactamases (ESBLs), e.g., ESBLs of the TEM or SHV type, compromise the efficacies of expanded-spectrum cephalosporins. An SHV non-ESBL that hydrolyzes only narrow-spectrum cephalosporins can be converted into an SHV ESBL through substitutions at three amino acid positions, 179, 238, or 238–240. In order to improve detection of SHV ESBLs, a novel method, based on real-time PCR monitored with fluorescently labeled hybridization probes and followed by melting curve analysis, was developed. It is able to (i) detect
bla
SHV
genes with high degrees of sensitivity and specificity, (ii) discriminate between
bla
SHV non-ESBL
and
bla
SHV ESBL
, and (iii) categorize the SHV ESBL producers into three phenotypically relevant subgroups. This method, termed the SHV melting curve mutation detection method, represents a powerful tool for epidemiological studies with SHV ESBLs. It even has the potential to be used in the diagnostic microbiology laboratory, because up to 32 clinical isolates can be processed in less than 1 h by starting with just a few bacterial colonies.
Antimicrobial Activity of Intraurethrally Administered ProbioticLactobacillus caseiin a Murine Model ofEscherichia coliUrinary Tract Infection
Authors: Asahara Takashi , Nomoto Koji , Watanuki Masaaki , Yokokura Teruo 
Published: July 2002

ABSTRACTThe antimicrobial activity of the intraurethrally administered probioticLactobacillus caseistrain Shirota againstEscherichia coliin a murine urinary tract infection (UTI) model was examined. UTI was induced by intraurethral administration ofEscherichia colistrain HU-1 (a clinical isolate from a UTI patient, positive for type 1 and P fimbriae), at a dose of 1 × 106to 2 × 106CFU in 20 μl of saline, into a C3H/HeN mouse bladder which had been traumatized with 0.1 N HCl followed immediately by neutralization with 0.1 N NaOH 24 h before the challenge infection. Chronic infection with the pathogen at 106CFU in the urinary tract (bladder and kidneys) was maintained for more than 3 weeks after the challenge, and the number of polymorphonuclear leukocytes and myeloperoxidase activity in the urine were markedly elevated during the infection period. A single administration ofL. caseiShirota at a dose of 108CFU 24 h before the challenge infection dramatically inhibitedE. coligrowth and inflammatory responses in the urinary tract. Multiple daily treatments withL. caseiShirota during the postinfection period also showed antimicrobial activity in this UTI model. A heat-killed preparation ofL. caseiShirota exerted significant antimicrobial effects not only with a single pretreatment (100 μg/mouse) but also with multiple daily treatments during the postinfection period. The otherLactobacillusstrains tested, i.e.,L. fermentumATCC 14931T,L. jenseniiATCC 25258T,L. plantarumATCC 14917T, andL. reuteriJCM 1112T, had no significant antimicrobial activity. Taken together, these results suggest that the probioticL. caseistrain Shirota is a potent therapeutic agent for UTI.
Type II Topoisomerase Mutations in Fluoroquinolone-Resistant Clinical Strains of
Pseudomonas aeruginosa
Isolated in 1998 and 1999: Role of Target Enzyme in Mechanism of Fluoroquinolone Resistance
Authors: Akasaka Takaaki , Tanaka Mayumi , Yamaguchi Akihito , Sato Kenichi 
Published: July 2002

ABSTRACT

The major mechanism of resistance to fluoroquinolones for
Pseudomonas aeruginosa
is the modification of type II topoisomerases (DNA gyrase and topoisomerase IV). We examined the mutations in quinolone-resistance-determining regions (QRDR) of
gyrA, gyrB, parC
, and
parE
genes of recent clinical isolates. There were 150 isolates with reduced susceptibilities to levofloxacin and 127 with reduced susceptibilities to ciprofloxacin among 513 isolates collected during 1998 and 1999 in Japan. Sequencing results predicted replacement of an amino acid in the QRDR of DNA gyrase (GyrA or GyrB) for 124 of the 150 strains (82.7%); among these, 89 isolates possessed mutations in
parC
or
parE
which lead to amino acid changes. Substitutions of both Ile for Thr-83 in GyrA and Leu for Ser-87 in ParC were the principal changes, being detected in 48 strains. These replacements were obviously associated with reduced susceptibilities to levofloxacin, ciprofloxacin, and sparfloxacin; however, sitafloxacin showed high activity against isolates with these replacements. We purified GyrA (The-83 to Ile) and ParC (Ser-87 to Leu) by site-directed mutagenesis and compared the inhibitory activities of the fluoroquinolones. Sitafloxacin showed the most potent inhibitory activities against both altered topoisomerases among the fluoroquinolones tested. These results indicated that, compared with other available quinolones, sitafloxacin maintained higher activity against recent clinical isolates with multiple mutations in
gyrA
and
parC
, which can be explained by the high inhibitory activities of sitafloxacin against both mutated enzymes.
Novel Synthetic Polyamines Are Effective in the Treatment of Experimental Microsporidiosis, an Opportunistic AIDS-Associated Infection
Authors: Bacchi Cyrus J. , Weiss Louis M. , Lane Schenella , Frydman Benjamin , Valasinas Aldonia , Reddy Venodhar , Sun Jerry S. , Marton Laurence J. , Khan Imitiaz A. , Moretto Magali , Yarlett Nigel , Wittner Murray 
Published: July 2002

ABSTRACTMicrosporidia are eukaryotic obligate intracellular protists that are emerging pathogens in immunocompromised hosts, such as patients with AIDS or patients who have undergone organ transplantation. We have demonstrated in vitro and in vivo that synthetic polyamine analogs are effective antimicrosporidial agents with a broad therapeutic window. CD8-knockout mice or nude mice infected with the microsporidianEncephalitozoon cuniculiwere cured when they were treated with four different novel polyamine analogs at doses ranging from 1.25 to 5 mg/kg of body weight/day for a total of 10 days. Cured animals demonstrated no evidence of parasitemia by either PCR or histologic staining of tissues 30 days after untreated control animals died.
Lack of Effect of Simultaneously Administered Didanosine Encapsulated Enteric Bead Formulation (Videx EC) on Oral Absorption of Indinavir, Ketoconazole, or Ciprofloxacin
Authors: Damle Bharat D. , Mummaneni Vanaja , Kaul Sanjeev , Knupp Catherine 
Published: July 2002

ABSTRACTDidanosine formulation that contains a buffer to prevent it from acid-mediated degradation can result in a significant decrease in the oral absorption of certain drugs because of interactions with antacids. An enteric formulation of didanosine is unlikely to cause such drug interactions because it lacks antacids. This study was undertaken to determine whether the enteric bead formulation of didanosine (Videx EC) influences the bioavailability of indinavir, ketoconazole, and ciprofloxacin, three drugs that are representative of a broader class of drugs affected by interaction with antacids. Healthy subjects of either gender were enrolled in three separate open-label, single-dose, two-way crossover studies. Subjects were randomized to treatment A (800 mg of indinavir, 200 mg of ketoconazole, or 750 mg of ciprofloxacin) or treatment B (same dose of indinavir, ketoconazole, or ciprofloxacin, but with 400 mg of didanosine as an encapsulated enteric bead formulation). A lack of interaction was concluded if the 90% confidence interval (CI) of the ratio of the geometric means of log-transformedCmaxand AUC0-∞values (i.e., values for the area under the concentration-time curve from time zero to infinity) of indinavir, ketoconazole, and ciprofloxacin were contained entirely between 0.75 and 1.33. For indinavir (n= 23), the point estimate (90% CI; minimum, maximum) of the ratios ofCmaxand AUC0-∞values were 0.99 (0.91, 1.06) and 0.96 (0.91, 1.02), respectively. In the ketoconazole study, 3 of 24 subjects showed anomalous absorption of ketoconazole (i.e., an ∼8-fold-lower AUC compared to historical data), which was the reference treatment. A post hoc analysis performed after these three subjects were excluded indicated that the point estimates (90% CI) of the ratios of Cmaxand AUC0-∞values were 0.99 (0.86, 1.14) and 0.97 (0.85, 1.10), respectively. For ciprofloxacin (n= 16), the point estimate (90% CI) of the ratios ofCmaxand AUC0-∞values were 0.92 (0.79, 1.07) and 0.91 (0.76, 1.08), respectively. All three studies clearly indicated a lack of interaction. TheTmaxandt1/2for indinavir, ketoconazole, and ciprofloxacin were similar between treatments. Our results showed that the lack of interaction of didanosine encapsulated enteric bead formulation with indinavir, ketoconazole, and ciprofloxacin indicates that this enteric formulation of didanosine can be concomitantly administered with drugs whose bioavailability is known to be reduced by interaction with antacids.
Selection of
Streptococcus pneumoniae
Mutants Having Reduced Susceptibility to Moxifloxacin and Levofloxacin
Authors: Li Xinying , Zhao Xilin , Drlica Karl 
Published: July 2002

ABSTRACT

With
Streptococcus pneumoniae
, moxifloxacin was 4- and 10-fold more effective than levofloxacin at restricting selection of resistant mutants and at killing resistant mutants, respectively. The selection frequency for first-step topoisomerase mutants was 1,000 times lower for moxifloxacin than for levofloxacin; this difference was lost when second-step mutants were selected.
mar
Operon Involved in Multidrug Resistance of
Enterobacter aerogenes
Authors: Chollet Renaud , Bollet Claude , Chevalier Jacqueline , Malléa Monique , Pagès Jean-Marie , Davin-Regli Anne 
Published: July 2002

ABSTRACT

We determined the sequence of the entire
marRAB
operon in
Enterobacter aerogenes
. It is functionally and structurally analogous to the
Escherichia coli
operon. The overexpression of
E. aerogenes
MarA induces a multidrug resistance phenotype in a susceptible strain, demonstrated by a noticeable resistance to various antibiotics, a decrease in immunodetected porins, and active efflux of norfloxacin.
Inhibitory Activities of Quinolones against DNA Gyrase and Topoisomerase IV of
Enterococcus faecalis
Authors: Onodera Yoshikuni , Okuda Jun , Tanaka Mayumi , Sato Kenichi 
Published: July 2002

ABSTRACT

We have cloned the DNA gyrase and topoisomerase IV genes of
Enterococcus faecalis
to examine the actions of quinolones against
E. faecalis
genetically and enzymatically. We first generated levofloxacin-resistant mutants of
E. faecalis
by stepwise selection with increasing drug concentrations and analyzed the quinolone resistance-determining regions of
gyrA
and
parC
from the resistant mutants. Isogenic mutants with low-level resistance contained a mutation in
gyrA
, whereas those with higher levels of resistance had mutations in both
gyrA
and
parC
. These results suggested that
gyrA
is the primary target for levofloxacin in
E. faecalis
. We then purified the recombinant DNA gyrase and topoisomerase IV enzymes of
E. faecalis
and measured the in vitro inhibitory activities of quinolones against these enzymes. The 50% inhibitory concentrations (IC
50
s) of levofloxacin, ciprofloxacin, sparfloxacin, tosufloxacin, and gatifloxacin for DNA gyrase were found to be higher than those for topoisomerase IV. In conflict with the genetic data, these results indicated that topoisomerase IV would be the primary target for quinolones in
E. faecalis
. Among the quinolones tested, the IC
50
of sitafloxacin (DU-6859a), which shows the greatest potency against enterococci, for DNA gyrase was almost equal to that for topoisomerase IV; its IC
50
s were the lowest among those of all the quinolones tested. These results indicated that other factors can modulate the effect of target affinity to determine the bacterial killing pathway, but the highest inhibitory actions against both enzymes correlated with good antienterococcal activities.
Commensal Interactions in a Dual-Species Biofilm Exposed to Mixed Organic Compounds
Authors: Cowan Stacie E. , Gilbert Eric , Liepmann Dorian , Keasling J. D. 
Published: July 2002

ABSTRACT

There is limited knowledge of interspecies interactions in biofilm communities. In this study,
Pseudomonas
sp. strain GJ1, a 2-chloroethanol (2-CE)-degrading organism, and
Pseudomonas putida
DMP1, a
p
-cresol-degrading organism, produced distinct biofilms in response to model mixed waste streams composed of 2-CE and various
p
-cresol concentrations. The two organisms maintained a commensal relationship, with DMP1 mitigating the inhibitory effects of
p
-cresol on GJ1. A triple-labeling technique compatible with confocal microscopy was used to investigate the influence of toxicant concentrations on biofilm morphology, species distribution, and exopolysaccharide production. Single-species biofilms of GJ1 shifted from loosely associated cell clusters connected by exopolysaccharide to densely packed structures as the
p
-cresol concentrations increased, and biofilm formation was severely inhibited at high
p
-cresol concentrations. In contrast, GJ1 was abundant when associated with DMP1 in a dual-species biofilm at all
p
-cresol concentrations, although at high
p
-cresol concentrations it was present only in regions of the biofilm where it was surrounded by DMP1. Evidence in support of a commensal relationship between DMP1 and GJ1 was obtained by comparing GJ1-DMP1 biofilms with dual-species biofilms containing GJ1 and
Escherichia coli
ATCC 33456, an adhesive strain that does not mineralize
p
-cresol. Additionally, the data indicated that only tower-like cell structures in the GJ1-DMP1 biofilm produced exopolysaccharide, in contrast to the uniform distribution of EPS in the single-species GJ1 biofilm.