bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antibiotic Resistance in the ECOR Collection: Integrons and Identification of a Novel
aad
Gene
Authors: Mazel Didier , Dychinco Broderick , Webb Vera A. , Davies Julian 
Published: July 2002

ABSTRACT

The 72
Escherichia coli
strains of the ECOR collection were examined for resistance to 10 different antimicrobial agents including ampicillin, tetracycline, mercury, trimethoprim, and sulfonamides. Eighteen strains were resistant to at least one of the antibiotics tested, and nearly 20% (14 of 72) were resistant to two or more. Several of the resistance determinants were shown to be carried on conjugative elements. The collection was screened for the presence of the three classes of integrons and for the
sul1
gene, which is generally associated with class 1 integrons. The four strains found to carry a class 1 integron also had Tn
21
-encoded mercury resistance. One of the integrons encoded a novel streptomycin resistance gene,
aadA7
, with an
attC
site (or 59-base element) nearly identical to the
attC
site associated with the
qacF
gene cassette found in In40 (M.-C. Ploy, P. Courvalin, and T. Lambert, Antimicrob. Agents Chemother. 42:2557–2563, 1998). The conservation of associated
attC
sites among unrelated resistance cassettes is similar to arrangements found in the
Vibrio cholerae
superintegrons (D. Mazel, B. Dychinco, V. A. Webb, and J. Davies, Science 280:605–608, 1998) and supports the hypothesis that resistance cassettes are picked up from superintegron pools and independently assembled from unrelated genes and related
attC
sites.
Unusual Susceptibility of a Multidrug-Resistant Yeast Strain to Peptidic Antifungals
Authors: Milewski Sławomir , Mignini Fiorenzo , Prasad Rajendra , Borowski Edward 
Published: July 2002

ABSTRACT

The susceptibility of
Saccharomyces cerevisiae
JG436 multidrug transporter deletion mutant, Δ
pdr5
, to several antifungal agents was compared to that of JG436-derived JGCDR1 and JGCaMDR1 transformants, harboring the
CDR1
and
CaMDR1
genes, encoding the main drug-extruding membrane proteins of
Candida albicans
. The JGCDR1 and JGCaMDR1 yeasts demonstrated markedly diminished susceptibility to the azole antifungals, terbinafine and cycloheximide, while that to amphotericin B was unchanged. Surprisingly, JGCDR1 but not JGCaMDR1 cells showed enhanced susceptibility to peptidic antifungals, rationally designed compounds containing inhibitors of glucosamine-6-phosphate synthase. It was found that these antifungal oligopeptides, as well as model oligopeptides built of proteinogenic amino acids, were not effluxed from JGCDR1 cells. Moreover, they were taken up by these cells at rates two to three times higher than by JG436. The tested oligopeptides were rapidly cleaved to constitutive amino acids by cytoplasmic peptidases. Studies on the mechanism of the observed phenomenon suggested that an additive proton motive force generated by Cdr1p stimulated uptake of oligopeptides into JGCDR1 cells, thus giving rise to the higher antifungal activity of FMDP [
N
3
-(4-methoxyfumaroyl)-
l
-2,3-diaminopropanoic acid]-peptides.
Pharmacokinetics of Stavudine and Didanosine Coadministered with Nelfinavir in Human Immunodeficiency Virus-Exposed Neonates
Authors: Rongkavilit Chokechai , Thaithumyanon Pimolrat , Chuenyam Theshinee , Damle Bharat D. , Limpongsanurak Sompop , Boonrod Chantana , Srigritsanapol Aeumporn , Hassink Elly A. M. , Hoetelmans Richard M. W. , Cooper David A. , Lange Joep M. A. , Ruxrungtham Kiat , Phanuphak Praphan 
Published: July 2002

ABSTRACT

We evaluated the pharmacokinetics of stavudine (d4T) and didanosine (ddI) in neonates. Eight neonates born to human immunodeficiency virus-infected mothers were enrolled to receive 1 mg of d4T per kg of body weight twice daily and 100 mg of ddI per m
2
once daily in combination with nelfinavir for 4 weeks after birth. Pharmacokinetic evaluations were performed at 14 and 28 days of age. For d4T, on days 14 and 28, the median areas under the concentration-time curves from 0 to 12 h (AUC
0–12
s) were 1,866 and 1,603, ng · h/ml, respectively, and the median peak concentrations (
C
max
s) were 463 and 507 ng/ml, respectively. For ddI, on days 14 and 28, the median AUC
0–10
s were 1,573 and 1,562 h · ng/ml, respectively, and the median
C
max
s were 627 and 687 ng/ml, respectively. Systemic levels of exposure to d4T were comparable to those seen in children, suggesting that the pediatric dose of 1 mg/kg twice daily is appropriate for neonates at 2 to 4 weeks of age. Levels of exposure to ddI were modestly higher than those seen in children. Whether this observation warrants a reduction of the ddI dose in neonates is unclear.
Nonculture Prediction of
Neisseria meningitidis
Susceptibility to Penicillin
Authors: Antignac Aude , Alonso Jean-Michel , Taha Muhamed-Kheir 
Published: July 2002

ABSTRACT

We developed a nonculture method to predict the susceptibility of
Neisseria meningitidis
to penicillin G. The
penA
gene was amplified and submitted to restriction fragment length polymorphism analysis. This approach was first validated with a collection of 75 meningococcal strains of known phenotypes. It was next successfully applied to 29 clinical samples.
Apoptosis Contributes to Amphotericin B- Induced Nephrotoxicity
Authors: Varlam Despina E. , Siddiq Mustafa M. , Parton Lance A. , Rüssmann Holger 
Published: July 2002

ABSTRACT

The aim of this study was to investigate whether apoptosis contributes to nephrotoxicity caused by amphotericin B (AmB). By detecting apoptosis-specific DNA fragmentation, it is demonstrated that proximal tubular cells (LLC-PK
1
) and medullary interstitial cells (RMIC) respond with programmed cell death when treated with therapeutic doses of AmB. Concomitant application of AmB and recombinant human insulin-like growth factor-1 (rhIGF-1), a known antiapoptotic agent, abrogated apoptosis in vitro. To validate that the observed apoptotic effects on renal tissue culture cells are applicable to an in vivo setting, an animal model was used for verification. Therefore, Sprague-Dawley rats were treated with AmB. The drug caused hypokalemia, decreased weight gain, loss of renal concentrating ability, and dehydration in a dose-dependent fashion. Microscopic examination of renal tissue sections revealed apoptotic alterations predominantly in proximal and distal tubular epithelial cells. To verify that the observed clinical side effects were linked to apoptosis, rhIGF-1 was applied concomitantly with AmB. In all animals, rhIGF-1 prevented the above-mentioned clinical side effects. Moreover, significantly reduced apoptosis was observed in renal tissue sections of these animals, indicating the relevance of apoptosis in nephrotoxicity. This is the first report to demonstrate that AmB induces apoptosis in the rat kidney in a dose-dependent fashion. The incidence of apoptosis correlates with renal toxicity and can be abrogated by concomitant treatment with rhIGF-1.
Prolonged Antimicrobial Activity of a Catheter Containing Chlorhexidine-Silver Sulfadiazine Extends Protection against Catheter Infections In Vivo
Authors: Bassetti Stefano , Hu Jean , D'Agostino Ralph B. , Sherertz Robert J. 
Published: July 2002

ABSTRACT

The present study evaluated in vitro and in vivo a new chlorhexidine (C)-silver sulfadiazine (S) vascular catheter (the CS2 catheter) characterized by a higher C content and by the extended release of the surface-bound antimicrobials. The CS2 catheter was compared with a first-generation, commercially available CS catheter (the CS1 catheter). The CS2 catheter produced slightly smaller zones of inhibition (mean difference, 0.9 mm [
P
< 0.001]) at 24 h against
Staphylococcus aureus
and five other microorganisms by several different methodologies. However, in a rabbit model, both CS catheters were similarly efficacious in preventing a catheter infection when the rabbits were inoculated with 10
4
to 10
7
CFU of
S. aureus
at the time of catheter insertion. The CS2 catheter retained its antimicrobial activity significantly longer in vitro and in vivo (half-lifes exceeded 34 and 7 days, respectively) and was also significantly more efficacious in preventing a catheter infection when 10
6
CFU of
S. aureus
was inoculated 2 days after catheter implantation (
P
< 0.001). These results suggest that prolonged anti-infective activity on the external catheter surface provides improved efficacy in the prevention of infection.
Effect of Abolishment of the Use of Antimicrobial Agents for Growth Promotion on Occurrence of Antimicrobial Resistance in Fecal Enterococci from Food Animals in Denmark
Authors: Aarestrup Frank Møller , Seyfarth Anne Mette , Emborg Hanne-Dorthe , Pedersen Karl , Hendriksen René S. , Bager Flemming 
Published: July 2002

ABSTRACT

From 1995 to 2000, a total of 673
Enterococcus faecium
and 1,088
Enterococcus faecalis
isolates from pigs together with 856
E. faecium
isolates from broilers were isolated and tested for susceptibility to four classes of antimicrobial agents used for growth promotion as part of the Danish program of monitoring for antimicrobial resistance. The four antimicrobials were avilamycin, erythromycin, vancomycin, and virginiamycin. Major changes in the use of antimicrobial agents for growth promotion have occurred during the last 6 years in Denmark. The government banned the use of avoparcin in 1995 and of virginiamycin in 1998. Furthermore, the producers have voluntarily stopped all use beginning in 1999. The avoparcin ban in 1995 was followed by a decrease in the occurrence of glycopeptide-resistant
E. faecium
(GRE) in broilers, from 72.7% in 1995 to 5.8% in 2000. The occurrence of glycopeptide resistance among isolates from pigs remained constant at around 20% from 1995 to 1997. It was shown that, in GRE from pigs, the genes encoding macrolide and glycopeptide resistance were genetically linked and that, following the decrease in the use of tylosin during 1998 and 1999, the occurrence of GRE in pigs decreased to 6.0% in 2000. From 1995 to 1997 the occurrence of erythromycin resistance among
E. faecium
and
E. faecalis
isolates from pigs was almost 90%. Use of tylosin decreased considerably during 1998 and 1999, and this decrease was followed by decreases in the occurrence of resistance to 46.7 and 28.1% among
E. faecium
and
E. faecalis
isolates from pigs, respectively. Erythromycin resistance among
E. faecium
isolates from broilers reached a maximum of 76.3% in 1997 but decreased to 12.7% in 2000 concomitantly with more limited use of virginiamycin. Use of virginiamycin increased from 1995 to 1997 and was followed by an increased occurrence of virginiamycin resistance among
E. faecium
isolates in broilers, from 27.3% in 1995 to 66.2% in 1997. In January 1998 the use of virginiamycin was banned in Denmark, and the occurrence of virginiamycin resistance decreased to 33.9% in 2000. Use of avilamycin increased from 1995 to 1996 and was followed by an increase in avilamycin resistance among
E. faecium
isolates from broilers, from 63.6% in 1995 to 77.4% in 1996. Since 1996 avilamycin usage has decreased, followed by a decrease in resistance to 4.8% in 2000. Our observations show that it is possible to reduce the occurrence of antimicrobial resistance in a national population of food animals when the selective pressure is removed. Cases in which resistance to vancomycin was linked to resistance to erythromycin were exceptions. In such cases resistance did not decrease until the use of both avoparcin and tylosin was limited.
Virtual Screening of Combinatorial Libraries across a Gene Family: in Search of Inhibitors of
Giardia lamblia
Guanine Phosphoribosyltransferase
Authors: Aronov Alex M. , Munagala Narsimha R. , Kuntz Irwin D. , Wang Ching C. 
Published: July 2002

ABSTRACT

Parasitic protozoa lack the ability to synthesize purine nucleotides de novo, relying instead on purine salvage enzymes for their survival. Guanine phosphoribosyltransferase (GPRT) from the protozoan parasite
Giardia lamblia
is a potential target for rational antiparasitic drug design, based on the experimental evidence, which indicates the lack of interconversion between adenine and guanine nucleotide pools. The present study is a continuation of our efforts to use three-dimensional structures of parasitic phosphoribosyltransferases (PRTs) to design novel antiparasitic agents. Two micromolar phthalimide-based GPRT inhibitors were identified by screening the in-house phthalimide library. A combination of structure-based scaffold selection using virtual library screening across the PRT gene family and solid phase library synthesis led to identification of smaller (molecular weight, <300) ligands with moderate to low specificity for GPRT; the best inhibitors, GP3 and GP5, had
K

i

values in the 23 to 25 μM range. These results represent significant progress toward the goal of designing potent inhibitors of purine salvage in
Giardia
parasites. As a second step in this process, altering the phthalimide moiety to optimize interactions in the guanine-binding pocket of GPRT is expected to lead to compounds with promising activity against
G. lamblia
PRT.
Gatifloxacin Efficacy in Treatment of Experimental Methicillin-Sensitive
Staphylococcus aureus
-Induced Osteomyelitis in Rabbits
Authors: Shirtliff Mark E. , Calhoun Jason H. , Mader Jon T. 
Published: July 2002

ABSTRACT

The effectiveness of oral gatifloxacin was compared to that of standard parenteral antibiotic therapy (nafcillin) for the treatment of experimental methicillin-sensitive
Staphylococcus aureus
-induced osteomyelitis in a rabbit model. Gatifloxacin was as effective as nafcillin in clearing the infection. Therefore, oral gatifloxacin treatment of osteomyelitis may be an effective alternative to intravenous nafcillin treatment.
Efficacy of Minocycline and EDTA Lock Solution in Preventing Catheter-Related Bacteremia, Septic Phlebitis, and Endocarditis in Rabbits
Authors: Raad Issam , Hachem Ray , Tcholakian Robert K. , Sherertz Robert 
Published: July 2002

ABSTRACT

To determine the efficacy of antibiotic catheter lock solution in preventing catheter-related infections, silicone catheters were tunneled and inserted into the jugular veins of 18 rabbits. The catheters were challenged with an intraluminal injection of 10
5
CFU of slime-producing
Staphylococcus epidermidis
in 0.1 ml of water. The catheters were maintained on heparin (100 IU/ml) flush for the first 3 days. On day 3, quantitative blood samples for culture were obtained from the catheters and ear veins, which documented catheter-related bacteremia, and the rabbits were randomized to have their catheters flushed as follows: five animals were continued on heparin (100 IU/ml), five animals received vancomycin (3 mg/ml) with heparin (100 IU/ml), and eight animals received 3 mg of minocycline per ml with 30 mg of EDTA per ml (M-EDTA). All animals were killed at day 7. Blood, catheters, jugular veins, and heart valves were cultured quantitatively. Animals maintained on heparin developed catheter-related colonization, bacteremia, septic phlebitis, and endocarditis. Vancomycin-heparin partially prevented catheter colonization, bacteremia, and phlebitis (
P
= 0.2). M-EDTA completely prevented catheter colonization, catheter-related bacteremia, and phlebitis in all of the animals (
P
< 0.01). Tricuspid endocarditis was equally prevented by vancomycin-heparin and M-EDTA (
P
≤ 0.06). In conclusion, the M-EDTA catheter flush solution was highly efficacious in preventing catheter-related colonization, bacteremia, septic phlebitis, and endocarditis in rabbits.
Impact of Trimethoprim-Sulfamethoxazole Prophylaxis on Etiology and Susceptibilities of Pathogens Causing Human Immunodeficiency Virus-Associated Bacteremia
Authors: Wininger David A. , Fass Robert J. 
Published: July 2002

ABSTRACT

The impact of chronic prophylactic administration of trimethoprim-sulfamethoxazole (SXT) on the ecology and the antimicrobial susceptibilities of bloodstream pathogens in human immunodeficiency virus (HIV)-infected patients was studied using a retrospective chart review. Eighty-nine patients with advanced HIV infection developed 124 episodes of bacteremia with 156 pathogenic isolates.
Staphylococcus aureus
and
Enterobacteriaceae
tended to be less common among patients receiving SXT. Isolates from patients receiving SXT were likelier (75%) to be resistant to 20 μg of SXT/ml than those from patients not receiving SXT (33%) (
P
< 0.001).
Involvement of an Extracellular Protease in Algicidal Activity of the Marine Bacterium
Pseudoalteromonas
sp. Strain A28
Authors: Lee Sun-og , Kato Junichi , Takiguchi Noboru , Kuroda Akio , Ikeda Tsukasa , Mitsutani Atsushi , Ohtake Hisao 
Published: July 2002

ABSTRACT

The marine bacterium
Pseudoalteromonas
sp. strain A28 was able to kill the diatom
Skeletonema costatum
strain NIES-324. The culture supernatant of strain A28 showed potent algicidal activity when it was applied to a paper disk placed on a lawn of
S. costatum
NIES-324. The condensed supernatant, which was prepared by subjecting the A28 culture supernatant to ultrafiltration with a 10,000-
M
w
-cutoff membrane, showed algicidal activity, suggesting that strain A28 produced extracellular substances capable of killing
S. costatum
cells. The condensed supernatant was then found to have protease and DNase activities. Two
Pseudoalteromonas
mutants lacking algicidal activity, designated NH1 and NH2, were selected after
N
-methyl-
N
′-nitrosoguanidine mutagenesis. The culture supernatants of NH1 and NH2 showed less than 15% of the protease activity detected with the parental strain, A28. The protease was purified to homogeneity from A28 culture supernatants by using ion-exchange chromatography followed by preparative gel electrophoresis. Paper-disk assays revealed that the purified protease had potent algicidal activity. The purified protease had a molecular mass for 50 kDa, and the N-terminal amino acid sequence was determined to be Ala-Thr-Pro-Asn-Asp-Pro. The optimum pH and temperature of the protease were found to be 8.8 and 30°C, respectively, by using succinyl-Ala-Ala-Pro-Phe-
p
-nitroanilide as a substrate. The protease activity was strongly inhibited by phenylmethylsulfonyl fluoride, diisopropyl fluorophosphate, antipain, chymostatin, and leupeptin. No significant inhibition was detected with EDTA, EGTA, phenanthroline or tetraethylenepentamine. These results suggest that
Pseudoalteromonas
sp. strain A28 produced an extracellular serine protease which was responsible for the algicidal activity of this marine bacterium.
Detection and Identification of Bacterial Endosymbionts in Arbuscular Mycorrhizal Fungi Belonging to the Family Gigasporaceae
Authors: Bianciotto Valeria , Lumini Erica , Lanfranco Luisa , Minerdi Daniela , Bonfante Paola , Perotto Silvia 
Published: July 2002

ABSTRACT

Intracellular bacteria have been found previously in one isolate of the arbuscular mycorrhizal (AM) fungus
Gigaspora margarita
BEG 34. In this study, we extended our investigation to 11 fungal isolates obtained from different geographic areas and belonging to six different species of the family Gigasporaceae. With the exception of
Gigaspora rosea
, isolates of all of the AM species harbored bacteria, and their DNA could be PCR amplified with universal bacterial primers. Primers specific for the endosymbiotic bacteria of BEG 34 could also amplify spore DNA from four species. These specific primers were successfully used as probes for in situ hybridization of endobacteria in
G. margarita
spores. Neighbor-joining analysis of the 16S ribosomal DNA sequences obtained from isolates of
Scutellospora persica
,
Scutellospora castanea
, and
G. margarita
revealed a single, strongly supported branch nested in the genus
Burkholderia
.
A Homokaryotic Derivative of a
Phanerochaete chrysosporium
Strain and Its Use in Genomic Analysis of Repetitive Elements
Authors: Stewart Philip , Gaskell Jill , Cullen Daniel 
Published: July 2002

ABSTRACT

Analysis of complex gene families in the lignin-degrading basidiomycete
Phanerochaete chrysosporium
has been hampered by the dikaryotic nuclear condition. To facilitate genetic investigations in
P. chrysosporium
strain BKM-F-1767, we isolated a homokaryon from regenerated protoplasts. The nuclear condition was established by PCR amplification of five unlinked genes followed by probing with allele-specific oligonucleotides. Under standard nitrogen-limited culture conditions, lignin peroxidase, manganese peroxidase, and glyoxal oxidase activities of the homokaryon were equivalent to those of the parental dikaryon. We used the homokaryon to determine the genomic organization and to assess transcriptional effects of a family of repetitive elements. Previous studies had identified an insertional mutation,
Pce1
, within lignin peroxidase allele
lipI2
. The element resembled nonautonomous class II transposons and was present in multiple copies in strain BKM-F-1767. In the present study, three additional copies of the
Pce1
-like element were cloned and sequenced. The distribution of elements was nonrandom; all localized to the same 3.7-Mb chromosome, as assessed by segregation analysis and Southern blot analysis of the homokaryon. Reverse transcription-PCR (RT-PCR) showed that
Pce1
was not spliced from the
lipI2
transcript in either the homokaryon or the parental dikaryon. However, both strains had equivalent lignin peroxidase activity, suggesting that some
lip
genes may be redundant.
Effect of Sample Holding Time on Recovery of
Cryptosporidium
Oocysts and
Giardia
Cysts from Water Samples
Authors: Robertson L. J. , Gjerde B. 
Published: July 2002

ABSTRACT

U.S. Environmental Protection Agency methods for analysis of water for
Cryptosporidium
and
Giardia
stipulate maximum sample holding times which are not always practical to comply with. A spiking experiment indicated that holding times of up to 2 weeks had no significant effect on recovery of these parasites from 10-liter samples of raw water in plastic carboys.
Molecular Analyses of Novel Methanotrophic Communities in Forest Soil That Oxidize Atmospheric Methane
Authors: Henckel Thilo , Jäckel Udo , Schnell Sylvia , Conrad Ralf 
Published: July 2002

ABSTRACTForest and other upland soils are important sinks for atmospheric CH4, consuming 20 to 60 Tg of CH4per year. Consumption of atmospheric CH4by soil is a microbiological process. However, little is known about the methanotrophic bacterial community in forest soils. We measured vertical profiles of atmospheric CH4oxidation rates in a German forest soil and characterized the methanotrophic populations by PCR and denaturing gradient gel electrophoresis (DGGE) with primer sets targeting thepmoAgene, coding for the α subunit of the particulate methane monooxygenase, and the small-subunit rRNA gene (SSU rDNA) of all life. The forest soil was a sink for atmospheric CH4in situ and in vitro at all times. In winter, atmospheric CH4was oxidized in a well-defined subsurface soil layer (6 to 14 cm deep), whereas in summer, the complete soil core was active (0 cm to 26 cm deep). The content of total extractable DNA was about 10-fold higher in summer than in winter. It decreased with soil depth (0 to 28 cm deep) from about 40 to 1 μg DNA per g (dry weight) of soil. The PCR product concentration of SSU rDNA of all life was constant both in winter and in summer. However, the PCR product concentration ofpmoAchanged with depth and season.pmoAwas detected only in soil layers with active CH4oxidation, i.e., 6 to 16 cm deep in winter and throughout the soil core in summer. The same methanotrophic populations were present in winter and summer. Layers with high CH4consumption rates also exhibited more bands ofpmoAin DGGE, indicating that high CH4oxidation activity was positively correlated with the number of methanotrophic populations present. ThepmoAsequences derived from excised DGGE bands were only distantly related to those of known methanotrophs, indicating the existence of unknown methanotrophs involved in atmospheric CH4consumption.