bluuebunny/crossref_metadata_2025 huggingface dataset:
Tissue Factor, Its Inhibitor, and the Thrombogenicity of Two New Synthetic Membranes
Authors: Zemanova Pavlina , Opatrny Karel , Vit Ladislav , Sefrna Frantisek
Published: July 2005

Abstract:  Background:  The aim of the study was to compare the effect of new high‐flux hemodialysis membranes made from polyacrylonitrile (AN69ST) and polysulfone (Helixone) on the plasma levels of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) playing a key role in hemostasis. Established thrombogenicity markers were also determined.

Methods:  In a clinical prospective randomized study, 10 patients were examined using either membrane at the start and at minutes 15, 60, and 240 of hemodialysis.

Results:  Increases in the plasma TF levels reached significance at the end of hemodialysis with both membranes, with the Helixone also after 15 min. TFPI levels tended to rise significantly from minute 15 onward while not differing from baseline at the end of the procedure. Judging by the increase in thrombin–antithrombin III complexes, both membranes significantly activated coagulation at the end of hemodialysis. Platelet factor 4 levels, released during thrombocyte and endothelial stimulation, were elevated from the start of procedures. There were no significant differences between the AN69ST and the Helixone in any of the assessed markers.

Conclusions:  The AN69ST and Helixone membranes do not differ in their effects on TF and TFPI or even in established thrombogenicity markers.
Image Processing Strategies Dedicated to Visual Cortical Stimulators: A Survey
Authors: Buffoni Louis‐Xavier , Coulombe Jonathan , Sawan Mohamad
Published: July 2005

Abstract: Multi‐electrode devices are constantly evolving toward a state where complexity and reliability are adequate for providing a breakthrough in visual cortical stimulation allowing the blind to recover partial vision. Yet few research teams have focused on the development of the front‐end subsystem that transforms an input image from a camera into stimulation commands. This article collects state‐of‐the‐art knowledge about the appearance and organization of phosphenes, and previous work in image processing dedicated to visual cortical stimulation. Observations and hypothesis about important issues are highlighted, and six image processing strategies that could be used in such a subsystem are presented, from the most optimistic that use brightness modulation to emulate grayscale to the most conservative that use only on/off phosphene evocation.
Computational Simulation of the Blood Separation Process
Authors: De Gruttola Sandro , Boomsma Kevin , Poulikakos Dimos , Ventikos Yiannis
Published: July 2005

Abstract:  The aim of this work is to construct a computational fluid dynamics model capable of simulating the quasitransient process of apheresis. To this end a Lagrangian–Eulerian model has been developed which tracks the blood particles within a delineated two‐dimensional flow domain. Within the Eulerian method, the fluid flow conservation equations within the separator are solved. Taking the calculated values of the flow field and using a Lagrangian method, the displacement of the blood particles is calculated. Thus, the local blood density within the separator at a given time step is known. Subsequently, the flow field in the separator is recalculated. This process continues until a quasisteady behavior is reached. The simulations show good agreement with experimental results. They shows a complete separation of plasma and red blood cells, as well as nearly complete separation of red blood cells and platelets. The white blood cells build clusters in the low concentrate cell bed.
The Japanese Artificial Organs Scene: Current Status
Authors: Mitamura Yoshinori , Murabayashi Shun
Published: July 2005

Abstract:  Artificial organs and regenerative medicine are the subjects of very active research and development (R&D) in Japan and various artificial organs are widely used in patients. Results of the R&D are presented at the annual conference of the Japanese Society for Artificial Organs (JSAO). Progress in the fields of artificial organs and regenerative medicine are reviewed annually in the Japanese Journal of Artificial Organs. The official English‐language journal of JSAO, Journal of Artificial Organs, also publishes many original articles by Japanese researchers. Although the annual conference and the publications of JSAO provide the world with update information on artificial organs and regenerative medicine in Japan, the information is not always understood appropriately in the rest of the world, mainly due to language problems. This article therefore introduces the current status of artificial organs and regenerative medicine in Japan. Artificial hearts and metabolic support systems are reviewed here and other interesting areas such as regenerative medicine can be found elsewhere.
The Bioreactor With CYP3A4‐ and Glutamine Synthetase‐Introduced HepG2 Cells: Treatment of Hepatic Failure Dog With Diazepam Overdosage
Authors: Wang Ning , Tsuruoka Shuichi , Yamamoto Hisashi , Enosawa Shin , Omasa Takeshi , Sata Naohiro , Matsumura Toshiharu , Nagai Hideo , Fujimura Akio
Published: July 2005

Abstract:  A novel recombinant human hepatic cell line, CYP3A4‐ and glutamine synthetase (GS, an enzyme which converts ammonium ion and glutamate to glutamine)‐introduced HepG2 (HepG2‐GS‐CYP3A4), was established. Its usefulness in a large‐scale culture with a circulatory bioreactor in vitro and in dog models of ischemic hepatic failure with acute diazepam (DZP, a substrate of CYP3A4) overdosage was further examined. HepG2‐GS‐CYP3A4 expressed about 9 times larger amounts of CYP3A4 protein than a control. After incubation with HepG2‐GS‐3A4 cells in a circulatory bioreactor for 24 h, ammonia and DZP concentrations in the culture medium significantly decreased by about 40%. Furthermore, this system improved the survival time and decreased serum concentrations of DZP, ammonia, and transaminase in dogs with ischemic hepatic failure plus acute DZP overdosage. The mean survival time with bioreactor with HepG2‐GS‐3A4 was 42.7 ± 3.6 h, which was significantly longer than that without reactor, with reactor (no cells), and with HepG2‐GS (23.4 ± 2.8, 22.1 ± 2.4, and 31 ± 3.7 h, respectively). Therefore, it is concluded that this bioartificial liver could be a good tool for the treatment of dogs with hepatic failure and that it could potentially be a bridging procedure to liver transplantation.
Activation of the Notch signaling pathway in response to pulp capping of rat molars
Authors: Løvschall H. , Tummers M. , Thesleff I. , Füchtbauer E. ‐M. , Poulsen K.
Published: July 2005

Notch signaling is an evolutionarily conserved pathway that controls the developmental choices made by individual cells. Cells communicate via Notch receptors and their ligands, which direct decisions on the fate of stem cells according to the states of their neighbors. In this study we explored Notch signaling after the pulp capping of adult first upper rat molars. The wound was capped with calcium hydroxide. In situ hybridization revealed an increased expression of Notch signaling genes on day 1, which showed a tendency to decrease on day 3. Notch1 increased in the subodontoblast zone and close to the lesion limited to a few cells. Notch2 increased in pulp stroma surrounded by coronal odontoblasts. Notch1 and, especially, Notch3 expression increased, corresponding to perivascular cell groups. A low increase of ligand expression was observed near the injury with Delta1 expression along the dentin wall and Jagged1 in the stroma. Expression of the downstream target, Hes1, was observed along the lesion and adjacent dentin walls. Hes5 expression was not observed. The results indicate that Notch signaling is activated in response to injury and associated with the differentiation of pulp cells into perivascular cells and odontoblasts. The findings are consistent with the concept that the Notch pathway controls stem cell fate during pulp regeneration.
In vivo degradation of resin–dentin bonds produced by a self‐etch and an etch‐and‐rinse adhesive
Authors: Koshiro Kenichi , Inoue Satoshi , Sano Hidehiko , De Munck Jan , Van Meerbeek Bart
Published: July 2005

Resin–dentin bonds are known to degrade in the relatively aggressive oral environment. In order to obtain greater insight into the interfacial degradation process, we examined, by using transmission electron microscopy (TEM), the interfacial ultrastructure of two adhesives bonded to dentin after 1 yr in vivo. Class V cavities were prepared on the buccal surfaces of 14 intact teeth of two monkeys and then restored by using either the two‐step self‐etch adhesive, Unifil Bond, or the two‐step etch‐and‐rinse adhesive, Single Bond, in combination with the restorative microhybrid composite, Z250. After 1 yr, 10 other teeth were restored by using the same materials (controls). One day later, the monkeys were killed, following which the microtensile bond strength to dentin was determined and the interfacial ultrastructure was examined by TEM. Whereas no noticeable changes in the morphology of the resin–dentin interface were observed between the 1‐d and 1‐yr specimens for Unifil Bond, Single Bond exhibited signs of interfacial degradation, in particular at the bottom of the 3 µm‐deep hybrid layer. In conclusion, the adhesive interface produced by the etch‐and‐rinse adhesive was less resistant to degradation than that produced by the self‐etch system.
Morphological appearance and chemical composition of enamel in primary teeth from patients with 22q11 deletion syndrome
Authors: Klingberg Gunilla , Dietz Wolfram , Óskarsdóttir Sólveig , Odelius Hans , Gelander Lars , Norén Jörgen G.
Published: July 2005

Patients with 22q11 deletion syndrome have many and complex medical problems, including hypocalcemia and/or hypoparathyroidism. Odontological findings include enamel aberrations in both dentitions. In order to describe enamel morphology, chemical composition in primary teeth, and to investigate the relationship between medical history and morphological appearance, dental enamel was investigated in 38 exfoliated primary teeth from 15 children and adolescents. Morphology was studied by the use of a polarized light microscope, microradiography, scanning electron microscopy, X‐ray microanalysis, and secondary ion mass spectrometry. The morphological findings were compared with medical history. The teeth showed, in principle, a normal morphological appearance with regard to prism structure. A high frequency of aberrations, such as hypomineralization, hypoplasia and extra incremental lines, were found. The majority of the aberrations were found around the neonatal line. There was a relationship between high numbers of medical problems in the patients and enamel deviations. The result supports the hypothesis of under‐reporting of both hypocalcemia and hypoparathyroidism in patients with 22q11 deletion syndrome.
Biogeneric tooth: a new mathematical representation for tooth morphology in lower first molars
Authors: Mehl Albert , Blanz Volker , Hickel Reinhard
Published: July 2005

A mathematical representation of tooth morphology may help to improve and automate restorative computer‐aided design processes, virtual dental education, and parametric morphology. However, to date, no quantitative formulation has been identified for the description of dental features. The aim of this study was to establish and to validate a mathematical process for describing the morphology of first lower molars. Stone replicas of 170 caries‐free first lower molars from young patients were measured three‐dimensionally with a resolution of about 100,000 points. First, the average tooth was computed, which captures the common features of the molar's surface quantitatively. For this, the crucial step was to establish a dense point‐to‐point correspondence between all teeth. The algorithm did not involve any prior knowledge about teeth. In a second step, principal component analysis was carried out. Repeated for 3 different reference teeth, the procedure yielded average teeth that were nearly independent of the reference (less than ± 40 µm). Additionally, the results indicate that only a few principal components determine a high percentage of the three‐dimensional shape variability of first lower molars (e.g. the first five principal components describe 52% of the total variance, the first 10 principal components 72% and the first 20 principal components 83%). With the novel approach presented in this paper, surfaces of teeth can be described efficiently in terms of only a few parameters. This mathematical representation is called the ‘biogeneric tooth’.
Oral Impacts on Daily Performance in Norwegian adults: validity, reliability and prevalence estimates
Authors: Åstrøm A. N. , Haugejorden O. , Skaret E. , Trovik T. A. , Klock K. S.
Published: July 2005

The Oral Impacts on Daily Performance (OIDP) instrument was translated into Norwegian and reviewed for cultural and conceptual equivalence by a group of bilingual academics. A sample of employees from the University of Bergen completed the Norwegian OIDP frequency questionnaire twice. A total of 173 and 108 subjects participated in the first and the second administration, respectively, of this questionnaire. A two‐stage proportionate random sample, comprising 2,000 residents (age‐range 16–79 yr), was drawn from the national population register by the Central Bureau of Statistics. Information became available for 1,309 persons who completed telephone interviews. The Norwegian OIDP preserved the overall concept of the English version. Test–retest reliability, in terms of Cohen's kappa, was 0.65, and Cronbach's alpha was high (≥ 0.80). In both samples, variations in the OIDP scores were apparent in relation to self‐reported oral health and number of remaining teeth, supporting construct and criterion validity of the inventory. Only three of the OIDP interviews were discarded, which supports face validity. A total of 18.3% confirmed that they had at least one oral impact. Age‐specific rates were 17.5%, 19.0%, 17.9% and 18.4% among 16–24, 24–44, 45–66 and 67–79‐yr‐old participants. The satisfactory psychometric properties provide evidence for the cross‐cultural use of the OIDP. The presence of a distinct floor effect indicates poor sensitivity of the OIDP to detect improvements of oral health‐related quality of life at a population level. Prevalence estimates were low, suggesting that the current oral health status has little impact on the daily performance of the Norwegian adult population.
Dental fear, regularity of dental attendance and subjective evaluation of dental erosion in women with eating disorders
Authors: Willumsen Tiril , Graugaard Peter K.
Published: July 2005

This questionnaire study, with a response rate of 53%, examined self‐induced vomiting, erosions and dental attendance in women with eating disorders (EDs) as well as dental fear and its effect on attendance and communication with the dentist. A survey of 371 responding women with EDs, who were recruited from a self‐help organization, revealed that dental fear was higher in women with EDs compared to the general population. Dental fear was present in 32.1% of women with EDs, and very high dental fear was present in 16.5% of women with EDs. Of those with very high dental fear, 32.3% had not visited a dental clinic at all in the preceding 2 yr, and 43.5% only initiated contact when they had symptoms. Self‐induced vomiting was especially frequent in women with bulimia nervosa (87.9%) and in those with more than one ED (the ‘mixed group’) (80.6%). Among those with self‐induced vomiting, 45.3% thought that they had erosions, although only 28.4% had erosions diagnosed by a dentist. Of women with EDs, 61.4% failed to disclose their condition. High dental fear did not affect willingness to disclose the ED. We conclude that dentists should examine ED patients carefully for dental erosions. Moreover, they should realize that most ED patients avoid disclosing their disorder and that dental fear further complicates dental treatment in these patients.
Functional Interrelationships between Cell Membrane and Cell Wall in Antimicrobial Peptide-Mediated Killing of
Staphylococcus aureus
Authors: Xiong Yan Q. , Mukhopadhyay Kasturi , Yeaman Michael R. , Adler-Moore Jill , Bayer Arnold S.
Published: July 2005

Perturbation of the
Staphylococcus aureus
cytoplasmic membrane (CM) is felt to play a key role in the microbicidal mechanism of many antimicrobial peptides (APs). However, it is not established whether membrane permeabilization (MP) alone is sufficient to kill susceptible staphylococci or if the cell wall (CW) and/or intracellular targets contribute to AP-induced lethality. We hypothesized that the relationships between MP and killing may differ for distinct APs. In this study, we investigated the association between AP-induced MP and lethality in
S. aureus
whole cells versus CW-free protoplasts, and in comparison to the MP of liposomes modeled after whole CMs in terms of phospholipid composition, fluidity and charge. Four APs with different structure-activity relationships were examined: thrombin-induced platelet microbicidal protein 1 (tPMP-1), human neutrophil protein 1 (hNP-1), gramicidin D, and polymyxin B. MP was quantified fluorometrically by calcein release. All APs tested, except polymyxin B, caused concentration-dependent MP and killing of whole cells, but not of protoplasts. The reduced AP susceptibility of protoplasts was associated with increased cardiolipin and lysyl-phosphatidylglycerol content and reduced fluidity of their CMs. However, liposomal MP induced by tPMP-1, hNP-1, and gramicidin D paralleled that of whole cells. Collectively, these results indicate that (i) structurally distinct APs likely exert their staphylocidal effects by differing mechanisms, (ii) MP is not the sole event leading to AP-induced staphylocidal activity, (iii) a complex interrelationship exists between the CM and CW in AP-induced killing, and (iv) liposomes modeled upon whole cell or protoplast CMs can recapitulate the respective susceptibilities to killing by distinct APs.
Neopeptide Antibiotics That Function as Opsonins and Membrane-Permeabilizing Agents for Gram-Negative Bacteria
Authors: Tsubery Haim , Yaakov Hertzig , Cohen Sofia , Giterman Tal , Matityahou Ariella , Fridkin Mati , Ofek Itzhak
Published: July 2005

We suggest a novel approach to enhancing antimicrobial drug action by utilizing engineered peptide conjugates. Our most potent conjugates, [fMLF]PMBN and [fMLF]PMEN, are nonapeptides derived from polymyxin B's (PMB's) cyclic moiety (Thr-Dab-cyclo[Dab-Dab-d-Phe-Leu-Dab-Dab-Thr], where Dab is 2,4-diaminobutyric acid) and polymyxin E's (PME's) cyclic moiety (Thr-Dab-cyclo[Dab-Dab-d-Leu-Leu-Dab-Dab-Thr]), respectively, attached to a linear tail comprised of formyl-Met-Leu-Phe (fMLF). The cyclic part binds to gram-negative lipopolysaccharides, rendering the bacterial outer membrane permeable to hydrophobic antibiotics. The tail confers chemotactic and opsonic activities upon the conjugates. These two activities appear to be the basis for the conjugates' antibacterial activities. The conjugates are 8 to 10 times less toxic than the parent PMB or PME antibiotics. Fourteen of 18 mice lethally challenged with erythromycin-resistantKlebsiella pneumoniaesurvived following intraperitoneal administration of erythromycin and [fMLF]PMBN, whereas erythromycin or the peptide conjugate alone had no effect. Moreover, the clearance ofKlebsiellafrom blood was markedly enhanced by intravenous injection of the [fMLF]PMEN peptide conjugate compared to the clearance of the organism from the mice treated with buffer alone as a control and was similar to that achieved by the PME antibiotic. Blood clearance was also significantly enhanced by administration of PMEN either alone or in a mixture with fMLF, although the effect was less than that produced by the peptide conjugate. Since resistance to polymyxins, the parent molecules of the synthetic cyclic peptides, is rare, the emergence of bacteria resistant to the antimicrobial properties of the peptide conjugates may be precluded as well.
Combination Therapy with Intravenous Colistin for Management of Infections Due to Multidrug-Resistant Gram-Negative Bacteria in Patients without Cystic Fibrosis
Authors: Kasiakou Sofia K. , Michalopoulos Argyris , Soteriades Elpidoforos S. , Samonis George , Sermaides George J. , Falagas Matthew E.
Published: July 2005

Colistin,
an antibiotic almost abandoned for intravenous administration for many
years due to its reported toxicity, has been recently reintroduced in
clinical practice due to the emergence of multidrug-resistant
gram-negative bacteria and the lack of development of new antibiotics
to combat them. To assess the safety and effectiveness of intravenous
colistin, in combination with other antimicrobial agents, in the
treatment of serious infections in patients without cystic fibrosis, a
retrospective cohort study in a 450-bed tertiary-care hospital in
Athens, Greece, was performed. Patients who were hospitalized from 1
October 2000 to 31 January 2004 and received intravenous colistin for
more than 72 h were further analyzed. The primary outcome
measure was the in-hospital mortality; secondary end points were the
clinical outcome of the infections and the occurrence of colistin
toxicity. Fifty patients received intravenous colistin with a median
(mean) daily dose of 3 (4.5) million IU for 16.5 (21.3) days for the
management of 54 episodes of infections due to multidrug-resistant
gram-negative bacteria. The predominant infections were pneumonia
(33.3%), bacteremia (27.8%), urinary tract infection (11.1%), and
intra-abdominal infection (11.1%). The responsible pathogens were
Acinetobacter baumannii
(51.9%),
Pseudomonas
aeruginosa
(42.6%), and
Klebsiella pneumoniae
(3.7%)
strains (no pathogen was isolated from one case). In-hospital mortality
was 24% (12/50 patients). Clinical response (cure or improvement) of
the infection was observed in 66.7% of episodes (36/54). In the studied
group, serum creatinine levels were decreased, at the end of colistin
treatment, by an average of 0.2 ± 1.3 mg/dl compared to
baseline levels. Deterioration of renal function during colistin
therapy was observed in 4/50 patients (8%). Coadministration of other
antimicrobial agents with spectrum against gram-negative microorganisms
and the absence of a control group constitute the major limitations of
this study. The use of intravenous colistin for the treatment of
infections due to multidrug-resistant gram-negative bacteria appears to
be safe and
effective.
Countrywide Survey Shows Very High Prevalence of
Plasmodium falciparum
Multilocus Resistance Genotypes in Cambodia
Authors: Khim Nimol , Bouchier Christiane , Ekala Marie-Thérèse , Incardona Sandra , Lim Pharath , Legrand Eric , Jambou Ronan , Doung Socheat , Puijalon Odile Mercereau , Fandeur Thierry
Published: July 2005

Cambodia is located in an area of resistance to multiple antimalarials and has been the first country to implement the systematic use of an artesunate-mefloquine combination as first-line treatment for
Plasmodium falciparum
malaria. Little is known, however, about the prevalence of resistance mutations within the natural parasite populations, impeding rational drug policy in this context. Using direct sequencing of PCR products, we have analyzed sequence polymorphism of the dihydrofolate reductase-thymidylate synthase, dihydropteroate synthetase, and multidrug resistance 1 genes in a large number of clinical
P. falciparum
isolates collected in various areas of Cambodia. This highlighted a 100% prevalence of haplotypes with multiple mutations in the target genes of antifolates after more than a decade without use of antifolates for malaria therapy. A high prevalence of mutations in
Pfmdr1
, including mutations associated with decreased in vitro susceptibility to mefloquine and quinine, was also observed. In addition, novel, low-frequency mutations were detected in
Pfmdr1
. Our findings show an alarming rate of multilocus resistance genotypes in Cambodia, requiring diligent surveillance and imposing limitations on possible future drug combinations.
Mechanism of Inhibition of Vaccinia Virus DNA Polymerase by Cidofovir Diphosphate
Authors: Magee Wendy C. , Hostetler Karl Y. , Evans David H.
Published: July 2005

Cidofovir (CDV) is a broad-spectrum antiviral agent that has been approved for clinical use in the treatment of cytomegalovirus retinitis. It has also been used off label to treat a variety of other viral infections, including those caused by orf and molluscum contagiosum poxviruses. Because it is a dCMP analog, CDV is thought to act by inhibiting viral DNA polymerases. However, the details of the inhibitory mechanism are not well established and nothing is known about the mechanism by which the drug inhibits poxvirus DNA polymerases. To address this concern, we have studied the effect of the active intracellular metabolite of CDV, CDV diphosphate (CDVpp), on reactions catalyzed by vaccinia virus DNA polymerase. Using different primer-template pairs and purified vaccinia virus polymerase, we observed that CDV is incorporated into the growing DNA strand opposite template G's but the enzyme exhibits a lower catalytic efficiency compared with dCTP. CDV-terminated primers are also good substrates for the next deoxynucleoside monophosphate addition step, but these CDV + 1 reaction products are poor substrates for further rounds of synthesis. We also noted that although CDV can be excised from the primer 3′ terminus by the 3′-to-5′ proofreading exonuclease activity of vaccinia virus polymerase, DNAs bearing CDV as the penultimate 3′ residue are completely resistant to exonuclease attack. These results show that vaccinia virus DNA polymerase can use CDVpp as a dCTP analog, albeit one that slows the rate of primer extension. By inhibiting the activity of the proofreading exonuclease, the misincorporation of CDV could also promote error-prone DNA synthesis during poxvirus replication.
Real-Time PCR Screening for 16S rRNA Mutations Associated with Resistance to Tetracycline in
Helicobacter pylori
Authors: Glocker Erik , Berning Marco , Gerrits Monique M. , Kusters Johannes G. , Kist Manfred
Published: July 2005

The effectiveness of recommended first-line therapies for
Helicobacter pylori
infections is decreasing due to the occurrence of resistance to metronidazole and/or clarithromycin. Quadruple therapies, which include tetracycline and a bismuth salt, are useful alternative regimens. However, resistance to tetracycline, mainly caused by mutations in the 16S rRNA genes (
rrnA
and
rrnB
) affecting nucleotides 926 to 928, are already emerging and can impair the efficacies of such second-line regimens. Here, we describe a novel real-time PCR for the detection of 16S rRNA gene mutations associated with tetracycline resistance. Our PCR method was able to distinguish between wild-type strains and resistant strains exhibiting single-, double, or triple-base-pair mutations. The method was applicable both to DNA extracted from pure cultures and to DNA extracted from fresh or frozen
H. pylori
-infected gastric biopsy samples. We therefore conclude that this real-time PCR is an excellent method for determination of
H. pylori
tetracycline resistance even when live bacteria are no longer available.
Efficacy of the Combination Rifampin-Streptomycin in Preventing Growth of
Mycobacterium ulcerans
in Early Lesions of Buruli Ulcer in Humans
Authors: Etuaful S. , Carbonnelle B. , Grosset J. , Lucas S. , Horsfield C. , Phillips R. , Evans M. , Ofori-Adjei D. , Klustse E. , Owusu-Boateng J. , Amedofu G. K. , Awuah P. , Ampadu E. , Amofah G. , Asiedu K. , Wansbrough-Jones M.
Published: July 2005

Mycobacterium ulcerans
disease is common in some humid tropical areas, particularly in parts of West Africa, and current management is by surgical excision of skin lesions ranging from early nodules to extensive ulcers (Buruli ulcer). Antibiotic therapy would be more accessible to patients in areas of Buruli ulcer endemicity. We report a study of the efficacy of antibiotics in converting early lesions (nodules and plaques) from culture positive to culture negative. Lesions were excised either immediately or after treatment with rifampin orally at 10 mg/kg of body weight and streptomycin intramuscularly at 15 mg/kg of body weight daily for 2, 4, 8, or 12 weeks and examined by quantitative bacterial culture, PCR, and histopathology for
M. ulcerans
. Lesions were measured during treatment. Five lesions excised without antibiotic treatment and five lesions treated with antibiotics for 2 weeks were culture positive, whereas three lesions treated for 4 weeks, five treated for 8 weeks, and three treated for 12 weeks were culture negative. No lesions became enlarged during antibiotic treatment, and most became smaller. Treatment with rifampin and streptomycin for 4 weeks or more inhibited growth of
M. ulcerans
in human tissue, and it provides a basis for proceeding to a trial of antibiotic therapy as an alternative to surgery for early
M. ulcerans
disease.
Contribution of Acquired Carbapenem-Hydrolyzing Oxacillinases to Carbapenem Resistance in
Acinetobacter baumannii
Authors: Héritier Claire , Poirel Laurent , Lambert Thierry , Nordmann Patrice
Published: July 2005

Carbapenem-hydrolyzing oxacillinases are reported increasingly in
Acinetobacter baumannii
. Since they hydrolyze carbapenems at low levels, the roles of carbapenem-hydrolyzing oxacillinases OXA-23, OXA-40, and OXA-58 in
A. baumannii
were determined. The
bla
OXA-23
,
bla
OXA-40
, and
bla
OXA-58
genes were inserted in broad-host-range plasmid pAT801 and transformed in
Escherichia coli
DH10B and in
A. baumannii
CIP 70.10 and its point mutant derivative
A. baumannii
BM4547, which overexpresses the efflux pump AdeABC. Natural plasmids harboring the
bla
OXA-23
and
bla
OXA-58
genes were also transformed in
A. baumannii
CIP 70.10. In addition, the
bla
OXA-40
gene was inactivated at its chromosome location in
A. baumannii
CLA-1. Intermediate levels of resistance or reduced susceptibilities to carbapenems were observed for
A. baumannii
transformants expressing OXA-23, OXA-40, and OXA-58. The inactivation of
bla
OXA-40
in
A. baumannii
CLA-1 yielded reduced susceptibilities to carbapenems. Carbapenem-hydrolyzing oxacillinases OXA-23, OXA-40, and to a lesser extent OXA-58 play a role in carbapenem resistance in
A. baumannii
, and overexpression of efflux pump AdeABC may also contribute to higher levels of resistance to β-lactams, including carbapenems.
Acquisition of Resistant Bowel Flora during a Double-Blind Randomized Clinical Trial of Ertapenem versus Piperacillin-Tazobactam Therapy for Intraabdominal Infections
Authors: DiNubile Mark J. , Chow Joseph W. , Satishchandran Vilas , Polis Adam , Motyl Mary R. , Abramson Murray A. , Teppler Hedy
Published: July 2005

Bowel colonization with resistant bacteria can develop in patients receiving broad-spectrum antimicrobial therapy. We compared the impact of two antimicrobial regimens often used to treat intraabdominal infections on susceptibility patterns of bowel flora at the end of therapy. In a double-blind clinical trial, adults with complicated intraabdominal infection requiring surgery were randomized to receive piperacillin-tazobactam (3.375 g every 6 h) or ertapenem (1 g once a day) for 4 to 14 days. Rectal swabs were obtained at baseline and at the end of study therapy to determine the acquisition rates of
Enterobacteriaceae
resistant to the study drug, extended-spectrum β-lactamase (ESBL)-producing
Escherichia coli
or
Klebsiella
species,
Pseudomonas aeruginosa
resistant to imipenem or piperacillin-tazobactam, and vancomycin-resistant
Enterococcus faecalis
or
Enterococcus faecium
. Treated patients were assessable for the acquisition of resistant bacteria if appropriate specimens were obtained at both time points.
Enterobacteriaceae
resistant to the treatment received were acquired during study therapy by 8/122 assessable piperacillin-tazobactam recipients (6.6%) compared to 0/122 assessable ertapenem recipients (
P
= 0.007). Neither ESBL-producing
E. coli
or
Klebsiella
species nor
P. aeruginosa
resistant to piperacillin-tazobactam was isolated from patients in either treatment group. Imipenem-resistant
P. aeruginosa
was acquired by two of the ertapenem recipients (1.6%) versus zero of the piperacillin-tazobactam recipients (
P
= 0.50). Vancomycin-resistant enterococci were acquired during therapy by 8/125 assessable ertapenem recipients (6.4%) versus 2/123 assessable piperacillin-tazobactam recipients (1.6%;
P
= 0.10). In this study, the acquisition of resistant
Enterobacteriaceae
occurred significantly more often in patients treated with piperacillin-tazobactam than in those treated with ertapenem.
Lipophilic Antifolate Trimetrexate Is a Potent Inhibitor of
Trypanosoma cruzi
: Prospect for Chemotherapy of Chagas' Disease
Authors: Senkovich Olga , Bhatia Vandanajay , Garg Nisha , Chattopadhyay Debasish
Published: July 2005

Trypanosoma cruzi
, a protozoan parasite, is the causative agent for Chagas' disease, which poses serious public health problem in Latin America. The two drugs available for the treatment of this disease are effective only against recent infections and are toxic. Dihydrofolate reductase (DHFR) has a proven track record as a drug target. The lipophilic antifolate trimetrexate (TMQ), which is an FDA-approved drug for the treatment of
Pneumocystis carinii
infection in AIDS patients, is a potent inhibitor of
T. cruzi
DHFR activity, with an inhibitory constant of 6.6 nM. The compound is also highly effective in killing
T. cruzi
parasites. The 50 and 90% lethal dose values against the trypomastigote are 19 and 36 nM, and the corresponding values for the amastigote form are 26 and 72 nM, respectively. However, as TMQ is also a good inhibitor of human DHFR, further improvement of the selectivity of this drug would be preferable. Identification of a novel antifolate selective against
T. cruzi
would open up new therapeutic avenues for treatment of Chagas' disease.
Mitochondrial Ribosome as the Target for the Macrolide Antibiotic Clarithromycin in the Helminth
Echinococcus multilocularis
Authors: Mathis Alexander , Wild Peter , Boettger Erik C. , Kapel Christian M. O. , Deplazes Peter
Published: July 2005

The mitochondrial rRNA of the tapeworm species
Echinococcus multilocularis
carries an adenine at sequence position 2058 (numbering according to that for
Escherichia coli
) of the large-subunit rRNA (lsrRNA), while the nucleus-encoded rRNA, as determined in this study, is characterized by 2058G. This indicates a dichotomy in the drug susceptibilities of ribosomes: cytoplasmic ribosomes are predicted to be resistant to macrolide antibiotics, while mitochondrial ribosomes lack the most common chromosomal resistance determinant, lsrRNA 2058G. Upon incubation with the macrolide clarithromycin, the formation of vesicles from metacestode tissue was reduced in a dose-dependent manner. Electron microscopy revealed distinct morphological alterations both of the mitochondria and of the vesicle wall (e.g., loss of microtriches) in drug-treated vesicles. Adult worms lost their motility and displayed morphological changes (shortening and constriction of proglottids and the presence of vacuoles) upon incubation with clarithromycin. Our findings demonstrate that macrolides have distinct in vitro effects on
E. multilocularis
, endorsing the use of sequence-based in silico approaches for exploitation of available ribosomal drugs as anthelmintic agents.
Specific Substitutions in the Echinocandin Target Fks1p Account for Reduced Susceptibility of Rare Laboratory and Clinical
Candida
sp. Isolates
Authors: Park S. , Kelly R. , Kahn J. Nielsen , Robles J. , Hsu M.-J. , Register E. , Li W. , Vyas V. , Fan H. , Abruzzo G. , Flattery A. , Gill C. , Chrebet G. , Parent S. A. , Kurtz M. , Teppler H. , Douglas C. M. , Perlin D. S.
Published: July 2005

An association between reduced susceptibility to echinocandins and changes in the 1,3-β-
d
-glucan synthase (GS) subunit Fks1p was investigated. Specific mutations in
fks1
genes from
Saccharomyces cerevisiae
and
Candida albicans
mutants are described that are necessary and sufficient for reduced susceptibility to the echinocandin drug caspofungin. One group of amino acid changes in ScFks1p, ScFks2p, and CaFks1p defines a conserved region (Phe 641 to Asp 648 of CaFks1p) in the Fks1 family of proteins. The relationship between several of these
fks1
mutations and the phenotype of reduced caspofungin susceptibility was confirmed using site-directed mutagenesis or integrative transformation. Glucan synthase activity from these mutants was less susceptible to caspofungin inhibition, and heterozygous and homozygous Ca
fks1 C. albicans
mutants could be distinguished based on the shape of inhibition curves. The
C. albicans
mutants were less susceptible to caspofungin than wild-type strains in a murine model of disseminated candidiasis. Five
Candida
isolates with reduced susceptibility to caspofungin were recovered from three patients enrolled in a clinical trial. Four
C. albicans
strains showed amino acid changes at Ser 645 of CaFks1p, while a single
Candida krusei
isolate had a deduced R1361G substitution. The clinical
C. albicans
mutants were less susceptible to caspofungin in the disseminated candidiasis model, and GS inhibition profiles and DNA sequence analyses were consistent with a homozygous
fks1
mutation. Our results indicate that substitutions in the Fks1p subunit of GS are sufficient to confer reduced susceptibility to echinocandins in
S. cerevisiae
and the pathogens
C. albicans
and
C. krusei
.
Production and Characterization of Stable Amphotericin-Resistant Amastigotes and Promastigotes of
Leishmania mexicana
Authors: Al-Mohammed Hamdan I. , Chance Michael L. , Bates Paul A.
Published: July 2005

The sensitivities of
Leishmania mexicana
amastigote and promastigote forms to amphotericin B were investigated in vitro and found to be strongly influenced by the culture media used. When differences in culture media were minimized, there was no significant difference in the 50% inhibitory concentration values between the two life cycle stages. Stable amphotericin B-resistant amastigote and promastigote lines were produced by the application of increasing drug pressure to long-term cultures. Lines capable of growth in concentrations of amphotericin B lethal to normal parasites were produced. Compared to normal parasites, these amphotericin-resistant lines showed marked differences in membrane sterol compositions, with very high levels of 4,14,dimethyl-cholesta-8,24-dienol and other methyl sterols. They also showed a consistent morphological feature, the presence of multilamellar membrane-like material in the flagellar pocket, revealed by transmission electron microscopy. Amphotericin-resistant parasites were capable of infecting BALB/c mice, but the resulting lesion growth was slower than that after infection with normal parasites. However, unlike normal parasites, the amphotericin-resistant parasites were unaffected by experimental chemotherapy with amphotericin B. These results show that amphotericin B resistance could arise as a result of increased clinical use of amphotericin B therapy.
Tn
5393
d, a Complex Tn
5393
Derivative Carrying the PER-1 Extended-Spectrum β-Lactamase Gene and Other Resistance Determinants
Authors: Mantengoli Elisabetta , Rossolini Gian Maria
Published: July 2005

In
Alcaligenes faecalis
FL-424/98, a clinical isolate that produces the PER-1 extended-spectrum β-lactamase, the
bla
PER-1
gene was found to be carried on a 44-kb nonconjugative plasmid, named pFL424, that was transferred to
Escherichia coli
by electroporation. Investigation of the genetic context of the
bla
PER-1
gene in pFL424 by means of a combined cloning and PCR mapping approach revealed that the gene is associated with a transposonlike element of the Tn
3
family. This 14-kb element is a Tn
5393
derivative of original structure, named Tn
5393
d, which contains the transposition module and the
strAB
genes typical of other members of the Tn
5393
lineage plus additional resistance determinants, including the
bla
PER-1
gene and a new allelic variant of the
aphA6
aminoglycoside phosphotransferase gene, named
aphA6b
, whose product is active against kanamycin, streptomycin, and amikacin. Tn
5393
d apparently originated from the consecutive insertion of two composite transposons into a Tn
5393
backbone carrying the
aphA6b
and the
bla
PER-1
genes, respectively. The putative composite transposon carrying
bla
PER-1
, named Tn
4176
, is made of two original and nonidentical insertion sequences of the IS
4
family, named IS
1387
a and IS
1387
b, of which one is interrupted by the insertion of an original insertion sequence of the IS
30
family, named IS
1066
. In pFL424, Tn
5393
d is inserted into a Tn
501
-like mercury resistance transposon. Transposition of Tn
5393
d or modules thereof containing the
bla
PER-1
gene from pFL424 to small multicopy plasmids or to a bacterial artificial chromosome was not detected in an
E. coli
host harboring both replicons.
Efficacy of Cefepime and Imipenem in Experimental Murine Pneumonia Caused by Porin-Deficient
Klebsiella pneumoniae
Producing CMY-2 β-Lactamase
Authors: Pichardo Cristina , Rodríguez-Martínez José Manuel , Pachón-Ibañez María E. , Conejo Carmen , Ibáñez-Martínez José , Martínez-Martínez Luis , Pachón Jerónimo , Pascual Álvaro
Published: July 2005

Previous studies have shown decreased in vitro activity of zwitterionic cephalosporins and carbapenems against porin-deficient
Klebsiella pneumoniae
expressing a plasmid-mediated AmpC-type β-lactamase (PACBL). The in vitro and in vivo activities of cefepime and imipenem were evaluated against the porin-deficient strain
K. pneumoniae
C2 and its CMY-2-producing derivative [
K. pneumoniae
C2(pMG248)]. The MICs (in micrograms/milliliter) of cefepime and imipenem against
K. pneumoniae
C2 were 0.125 and 0.25, respectively, while the corresponding values against
K. pneumoniae
C2(pMG248) were 8 and 16. Cefepime showed a greater inoculum effect than imipenem against both strains. Imipenem showed a significant postantibiotic effect (>2 h) against
K. pneumoniae
C2(pMG248) at 1×, 2×, 4×, 6×, and 8× MIC. The maximum concentrations of drug in serum of cefepime and imipenem in a pneumonia model using mice were 124.1 and 16.9 μg/ml, respectively. ΔT/MIC for
K. pneumoniae
C2 and C2(pMG248) were 1.29 h and 0.34 h for imipenem and 2.96 h and 1.27 h for cefepime. Both imipenem (30 mg/kg of body weight every 3 h) and cefepime (60 mg/kg every 4 h), administered for 72 h, increased the survival rate (86.6% and 100%) compared with untreated control animals (26.6%,
P
< 0.003) infected with
K. pneumoniae
C2. For the CMY-2-producing strain, imipenem, but not cefepime, increased the survival rate compared to the controls (86.6% and 40% versus 40%,
P
< 0.01). Bacterial concentration of the lungs was significantly decreased by both antimicrobials. In conclusion, imipenem was more active in terms of survival than cefepime for the treatment of murine pneumonia caused by a porin-deficient
K. pneumoniae
expressing PACBL CMY-2.
Antistaphylococcal Activity of DX-619, a New Des-F(6)-Quinolone, Compared to Those of Other Agents
Authors: Bogdanovich Tatiana , Esel Duygu , Kelly Linda M. , Bozdogan Bülent , Credito Kim , Lin Gengrong , Smith Kathy , Ednie Lois M. , Hoellman Dianne B. , Appelbaum Peter C.
Published: July 2005

The in vitro activity of DX-619, a new des-F(6)-quinolone, was tested against staphylococci and compared to those of other antimicrobials. DX-619 had the lowest MIC ranges/MIC
50
s/MIC
90
s (μg/ml) against 131
Staphylococcus aureus
strains (≤0.002 to 2.0/0.06/0.5) and 128 coagulase-negative staphylococci (0.004 to 0.25/0.016/0.125). Among strains tested, 76
S. aureus
strains and 51 coagulase-negative staphylococci were resistant to ciprofloxacin. DX-619 had the lowest MIC
50
/MIC
90
values against 127 quinolone-resistant staphylococci (0.125/0.5), followed by sitafloxacin (0.5/4), moxifloxacin (2/8), gatifloxacin (4/16), levofloxacin (16/>32), and ciprofloxacin (>32/>32). Raised quinolone MICs were associated with mutations in GyrA (S84L) and single or double mutations in GrlA (S80F or Y; E84K, G, or V) in all
S. aureus
strains tested. A recent vancomycin-resistant
S.
aureus
(VRSA) strain (Hershey) was resistant to available quinolones and was inhibited by DX-619 at 0.25 μg/ml and
sitafloxacin at 1.0 μg/ml. Vancomycin (except VRSA), linezolid,
ranbezolid, tigecycline, and quinupristin-dalfopristin were active
against all strains, and teicoplanin was active against
S.
aureus
but less active against coagulase-negative staphylococci.
DX-619 produced resistant mutants with MICs of 1 to >32μ
g/ml after <50 days of selection compared to 16 to>
32 μg/ml for ciprofloxacin, sitafloxacin,
moxifloxacin, and gatifloxacin. DX-619 and sitafloxacin were also more
active than other tested drugs against selected mutants and had the
lowest mutation frequencies in single-step resistance selection. DX-619
and sitafloxacin were bactericidal against six quinolone-resistant
(including the VRSA) and seven quinolone-susceptible strains tested,
whereas gatifloxacin, moxifloxacin, levofloxacin, and ciprofloxacin
were bactericidal against 11, 10, 7, and 5 strains at 4× MIC
after 24 h, respectively. DX-619 was also bactericidal
against one other VRSA strain, five vancomycin-intermediate
S.
aureus
strains, and four vancomycin-intermediate
coagulase-negative staphylococci. Linezolid, ranbezolid, and
tigecycline were bacteriostatic and quinupristin-dalfopristin,
teicoplanin, and vancomycin were bactericidal against two, eight, and
nine strains, and daptomycin and oritavancin were rapidly bactericidal
against all strains, including the VRSA. DX-619 has potent in vitro
activity against staphylococci, including methicillin-, ciprofloxacin-,
and vancomycin-resistant
strains.
Quantifying Mixed Populations of Drug-Resistant Human Immunodeficiency Virus Type 1
Authors: Moser Michael J. , Ruckstuhl Meta , Larsen Christine A. , Swearingen Amanda J. , Kozlowski Miroslaw , Bassit Leda , Sharma Prem L. , Schinazi Raymond F. , Prudent James R.
Published: July 2005

In order to survive prolonged treatment with antiretroviral nucleoside analogs, the human immunodeficiency virus type 1 (HIV-1) is selectively forced to acquire mutations in the reverse transcriptase (RT) gene. Some of these mutations are more common than others and have become markers for antiretroviral resistance. For the early detection of these markers, a novel MultiCode-RTx one-step testing system to rapidly and simultaneously characterize mixtures of HIV-1 targets was designed. For cDNA, nucleotide polymorphisms for codon M184V (ATG to GTG) and K65R (AAA to AGA) could be differentiated and quantified even when the population mixture varied as much as 1 to 10,000. Standard mixed-population curves using 1 to 100% of the mutant or wild type generated over 4 logs of total viral particle input did not affect the overall curves, making the method robust. The system was also applied to a small set of samples extracted from infected individuals on nucleoside reverse transcriptase inhibitor therapy. Of 13 samples tested, all were positive for HIV and 10 of the 13 genotypes determined were concordant with the line probe assay. MultiCode-RTx could be applied to other drug-selected mutations in the viral genome or for applications where single-base changes in DNA or RNA occur at frequencies reaching 0.01% to 1%, respectively.