bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Effects of Age and Sex on the Postnatal Responsiveness of Brown Adipose Tissue to Prolactin Administration in Rats
Authors: Pearce Sarah , Dieguez Carlos , Gualillo Oreste , Symonds Michael E. , Stephenson Terence
Published: June 2003

Previous studies have shown that prolactin administration to pregnant rats results in offspring with enhanced abundance of the brown adipose tissue‐specific uncoupling protein (UCP) 1. The present study therefore aimed to determine whether a similar effect was observed after birth and if the sex of the animal further influenced the responsiveness of brown adipose tissue mitochondria to prolactin administration. Daily prolactin injections were therefore commenced at 15, 35 or 60 days of age and continued for 4 days. The abundance of UCP1 was unchanged with age in females but decreased between 15 and 35 days in males and was lower in males than females by 60 days of age. Cytochrome c abundance remained unchanged with postnatal age in both males and females and was consistently higher in males at each sampling age. Prolactin decreased the abundance of UCP1 and cytochrome c when administered to female rats at 35 and 60 days of age, but had no effect at 15 days. In contrast, prolactin had no effect on UCP1 in male rats at any age, but did stimulate the abundance of cytochrome c at 15 days of age. In conclusion, the administration of prolactin to postnatal rats over the period in which maturation of the hypothalamic‐pituitary axis and brown adipose tissue function is occurring did not enhance UCP1 abundance. In females, prolactin actually caused a reduction in UCP1 suggesting that in rats it is only prior to birth that prolactin has a stimulatory role on brown adipose tissue development.
Endothelial‐Independent Prevention of High Blood Pressure in L‐Name‐Treated Rats by Angiotensin II type I Receptor Antisense Gene Therapy
Authors: Reaves Phyllis Y. , Beck Caren R. , Wang Hong‐Wei , Raizada Mohan K. , Katovich Michael J.
Published: June 2003

It has previously been established that a single systemic administration of retroviral vector containing angiotensin II type I receptor antisense (AT1R‐AS) in the neonatal spontaneously hypertensive rat (SHR) prevents development of hypertension, and in addition cardiac hypertrophy and endothelial dysfunction. However, these studies could not determine whether the effects of AT1R‐AS on high blood pressure (BP) and endothelial function were independent. Angiotensin receptor blockers have been shown to reduce BP in the L‐NAME (N ω‐nitro‐L‐arginine methyl ester hydrochloride)‐induced rat model of hypertension. Our objective in the present study was to use the L‐NAME model of hypertension to determine whether AT1R‐AS treatment would lower high BP and attenuate cardiac hypertrophy under conditions of permanent endothelial damage. A single bolus of LNSV‐AT1R‐AS viral particles in neonatal Wistar‐Kyoto (WKY) rats was without affect on basal BP. Efficacy of the transgene incorporation was assessed by observing a significant reduction in angiotensin‐induced dipsogenic response in the AT1R‐AS‐treated animals. Introduction of L‐NAME in the drinking water for 10 weeks resulted in the establishment of hypertension only in the WKY rats treated with vector alone. These hypertensive (BP, 179 ± 4 mmHg) animals showed a 17% increase in heart weight/body weight ratio and a 60% reduction in ACh‐induced vasorelaxation in phenylephrine‐preconstricted arteries. The L‐NAME‐induced high BP and cardiac hypertrophy were attenuated in rats expressing AT1R‐AS. However, endothelial dysfunction could not be prevented with the antisense therapy. These observations demonstrate that attenuation of endothelial dysfunction is not a prerequisite for the antihypertensive effects of AT1R‐AS treatment.
Origins of Agriculture at Kuk Swamp in the Highlands of New Guinea
Authors: Denham T. P. , Haberle S. G. , Lentfer C. , Fullagar R. , Field J. , Therin M. , Porch N. , Winsborough B.
Published: June 2003

Multidisciplinary investigations at Kuk Swamp in the Highlands of Papua New Guinea show that agriculture arose independently in New Guinea by at least 6950 to 6440 calibrated years before the present (cal yr B.P.). Plant exploitation and some cultivation occurred on the wetland margin at 10,220 to 9910 cal yr B.P. (phase 1), mounding cultivation began by 6950 to 6440 cal yr B.P. (phase 2), and ditched cultivation began by 4350 to 3980 cal yr B.P. (phase 3). Clearance of lower montane rainforests began in the early Holocene, with modification to grassland at 6950 to 6440 cal yr B.P. Taro (
Colocasia esculenta
) was utilized in the early Holocene, and bananas (
Musa
spp.) were intensively cultivated by at least 6950 to 6440 cal yr B.P.
Long-Distance Free-Space Distribution of Quantum Entanglement
Authors: Aspelmeyer Markus , Böhm Hannes R. , Gyatso Tsewang , Jennewein Thomas , Kaltenbaek Rainer , Lindenthal Michael , Molina-Terriza Gabriel , Poppe Andreas , Resch Kevin , Taraba Michael , Ursin Rupert , Walther Philip , Zeilinger Anton
Published: June 2003

We demonstrate the distribution of quantum entanglement via optical free-space links to independent receivers separated by 600 m, with no line of sight between each other. A Bell inequality between those receivers is violated by more than four standard deviations, confirming the quality of the entanglement. This outdoor experiment represents a step toward satellite-based distributed quantum entanglement.
Cannibalism by Sporulating Bacteria
Authors: González-Pastor José E. , Hobbs Errett C. , Losick Richard
Published: June 2003

Spore formation by the bacterium
Bacillus subtilis
is an elaborate developmental process that is triggered by nutrient limitation. Here we report that cells that have entered the pathway to sporulate produce and export a killing factor and a signaling protein that act cooperatively to block sister cells from sporulating and to cause them to lyse. The sporulating cells feed on the nutrients thereby released, which allows them to keep growing rather than to complete morphogenesis. We propose that sporulation is a stress-response pathway of last resort and that
B. subtilis
delays a commitment to spore formation by cannibalizing its siblings.
Coupling Gating with Ion Permeation in ClC Channels
Authors: Chen Tsung-Yu
Published: June 2003

In ClC chloride (Cl
–
) channels, unlike cation-selective ion channels, ion permeation is intimately coupled to fast gating. Recent research comparing the crystallographic structure of a bacterial ClC channel with functional studies of a
Torpedo
ClC channel suggests that gating depends on the negatively charged carboxyl group on a glutamate residue, which blocks the channel pore. In this model, the permeating Cl
–
competes with the carboxyl group for an anion-binding site in the channel pore. This model of Cl
–
competition with a glutamate gate helps explain the effect of intracellular Cl
–
on channel gating; the mechanism underlying the effects of extracellular Cl
–
, however, remains to be determined, as does the nature of the Cl
–
channel slow gate.
Voltage-Gated K Channels
Authors: Armstrong Clay M.
Published: June 2003

Ion channels and the electrical properties they confer on cells are involved in every human characteristic that distinguishes us from the stones in a field. Every perception, thought, movement, and heartbeat depends on electrical signals generated by the activity of ion channels. Early views of the relationship between channel structure and function have undergone substantial modification following the cloning of various ion channels and the determination of the structure of a simple bacterial K channel, the KcsA channel. This review focuses on the relationship between the structure and function of voltage-dependent K channels, covering the molecular bases of channel selectivity, conduction, and gating. The evolution of ion channels in bacteria is discussed, as well as the basis of channel selectivity and conduction in the KcsA channel. More complex channels have evolved molecular "gatekeepers," allowing them to respond to appropriate stimuli by opening, closing, and inactivating.
Life at the Top: The Transition State of AChR Gating
Authors: Auerbach Anthony
Published: June 2003

Most neurotransmitter receptors belong to either the pentameric nicotinoid receptor family or the tetrameric glutamatergic receptor family. The muscle nicotinic acetylcholine receptor (AChR), the prototype of the nicotinoid receptor family, gates by switching between a closed configuration (in which ion permeation is forbidden) and an open configuration (which allows ions to pass through). Rate-equilibrium linear free energy relationship analysis has allowed us to explore the transition state that links these two stable conformations. A series of point mutations were made to individual AChR residues, and the ensuing changes in the rate constants of channel opening and closing for the fully liganded receptor were determined. These experiments suggest that gating occurs approximately as a reversible, solitary conformational wave that propagates between the neurotransmitter binding site and the membrane domain, along the long axis of the receptor. A detailed knowledge of the gating mechanism can serve as a basis for understanding the shape of the postsynaptic ion current and for the differences in synaptic responses among different ligand-gated channels.
Biosynthetic Origin of Hygromycin A
Authors: Habib El-Sayed E. , Scarsdale J. Neel , Reynolds Kevin A.
Published: June 2003

Hygromycin A, an antibiotic produced byStreptomyces hygroscopicus, is an inhibitor of bacterial ribosomal peptidyl transferase. The antibiotic binds to the ribosome in a distinct but overlapping manner with other antibiotics and offers a different template for generation of new agents effective against multidrug-resistant pathogens. Reported herein are the results from a series of stable-isotope-incorporation studies demonstrating the biosynthetic origins of the three distinct structural moieties which comprise hygromycin A. Incorporation of [1-13C]mannose and intact incorporation ofd-[1,2-13C2]glucose into the 6-deoxy-5-keto-d-arabino-hexofuranose moiety are consistent with a pathway in which mannose is converted to an activatedl-fucose, via a 4-keto-6-deoxy-d-mannose intermediate, with a subsequent unusual mutation of the pyranose to the corresponding furanose. The aminocyclitol moiety was labeled byd-[1,2-13C2]glucose in a manner consistent with formation ofmyo-inositol and a subsequent unprecedented oxidation and transamination of the C-2 hydroxyl group to generateneo-inosamine-2. Incorporation of [carboxy-13C]-4-hydroxybenzoic acid and intact incorporation of [2,3-13C2]propionate are consistent with a polyketide synthase-type decarboxylation condensation to generate the 3,4-dihydroxy-α-methylcinnamic acid moiety of hygromycin A. No labeling of hygromycin A was observed when [3-13C]tyrosine, [3-13C]phenylalanine, or [carboxy-13C]benzoic acid was used, suggesting that the 4-hydroxybenzoic acid is derived directly from chorismic acid. Consistent with this hypothesis was the observation that hygromycin A titers could be reduced by addition ofN-(phosphonomethyl)-glycine (an inhibitor of chorismic acid biosynthesis) and restored by coaddition of 4-hydroxybenzoic acid. The convergent biosynthetic pathway established for hygromycin A offers significant versatility for applying the techniques of combinatorial and directed biosynthesis to production of new antibiotics which target the ribosomal peptidyl transferase activity.
Viridans Group Streptococci Are Donors in Horizontal Transfer of Topoisomerase IV Genes to
Streptococcus pneumoniae
Authors: Balsalobre Luz , Ferrándiz María José , Liñares Josefina , Tubau Fe , de la Campa Adela G.
Published: June 2003

A total of 46 ciprofloxacin-resistant (Cip
r
)
Streptococcus pneumoniae
strains were isolated from 1991 to 2001 at the Hospital of Bellvitge. Five of these strains showed unexpectedly high rates of nucleotide variations in the quinolone resistance-determining regions (QRDRs) of their
parC
,
parE
, and
gyrA
genes. The nucleotide sequence of the full-length
parC
,
parE
, and
gyrA
genes of one of these isolates revealed a mosaic structure compatible with an interspecific recombination origin. Southern blot analysis and nucleotide sequence determinations showed the presence of an
ant
-like gene in the intergenic
parE
-
parC
regions of the
S. pneumoniae
Cip
r
isolates with high rates of variations in their
parE
and
parC
QRDRs. The
ant
-like gene was absent from typical
S. pneumoniae
strains, whereas it was present in the intergenic
parE
-
parC
regions of the viridans group streptococci (
Streptococcus mitis
and
Streptococcus oralis
). These results suggest that the viridans group streptococci are acting as donors in the horizontal transfer of fluoroquinolone resistance genes to
S. pneumoniae
.
Burkholderia pseudomallei
Class A β-Lactamase Mutations That Confer Selective Resistance against Ceftazidime or Clavulanic Acid Inhibition
Authors: Tribuddharat Chanwit , Moore Richard A. , Baker Patricia , Woods Donald E.
Published: June 2003

Burkholderia pseudomallei
, the causative agent of melioidosis, is inherently resistant to a variety of antibiotics including aminoglycosides, macrolides, polymyxins, and β-lactam antibiotics. Despite resistance to many β-lactams, ceftazidime and β-lactamase inhibitor-β-lactam combinations are commonly used for treatment of melioidosis. Here, we examine the enzyme kinetics of β-lactamase isolated from mutants resistant to ceftazidime and clavulanic acid inhibition and describe specific mutations within conserved motifs of the β-lactamase enzyme which account for these resistance patterns. Sequence analysis of regions flanking the
B. pseudomallei penA
gene revealed a putative regulator gene located downstream of
penA
. We have cloned and sequenced the
penA
gene from
B. mallei
and found it to be identical to
penA
from
B. pseudomallei
.
Extended-Spectrum Cephalosporin Compared to Cefazolin for Treatment of
Klebsiella pneumoniae
-Caused Liver Abscess
Authors: Cheng Hsiao-Pei , Siu L. K. , Chang Feng-Yee
Published: June 2003

From January 1995 to May 2000, a total of 107 adults with liver abscess due to
Klebsiella pneumoniae
admitted at a large medical center in northern Taiwan were reviewed. Patients were considered to have received cefazolin or an extended-spectrum cephalosporin if they received at least 3 days of that antibiotic within the first 5 days of hospitalization. Fifty-nine (55.1%) patients received cefazolin, and 48 (44.9%) patients received an extended-spectrum cephalosporin. The demographic data, clinical features, severities of illness, and rates of early drainage for the two groups were comparable. However, the rates of developing complications for the two groups were significantly different (37.3 versus 6.3%, respectively;
P
< 0.001). Furthermore, six independent factors preventing severe complications following liver abscess due to
K. pneumoniae
were identified: normal platelet count, alkaline phosphatase less than 300 U/liter, no gas formation in the abscess, APACHE III score less than 40, use of an extended-spectrum cephalosporin, and early drainage. In conclusion, cefazolin therapy may be suboptimal for patients with liver abscess due to
K. pneumoniae
despite active in vitro susceptibility. Use of an extended-spectrum cephalosporin and early drainage for patients with liver abscess due to
K. pneumoniae
are suggested.
Correlation between Resistance ofPseudomonas aeruginosato Quaternary Ammonium Compounds and Expression of Outer Membrane Protein OprR
Authors: Tabata Atsushi , Nagamune Hideaki , Maeda Takuya , Murakami Keiji , Miyake Yoichiro , Kourai Hiroki
Published: June 2003

The adaptation mechanism ofPseudomonas aeruginosaATCC 10145 to quaternary ammonium compounds (QACs) was investigated. AP. aeruginosastrain with adapted resistance to QACs was developed by a standard broth dilution method. It was revealed thatP. aeruginosaexhibited remarkable resistance toN-dodecylpyridinium iodide (P-12), whose structure is similar to that of a common disinfectant, cetylpyridinium chloride. Adapted resistance to benzalkonium chloride (BAC), which is commonly used as a disinfectant, was also observed inP. aeruginosa. Moreover, the P-12-resistant strain exhibited cross-resistance to BAC. Analysis of the outer membrane protein of the P-12-resistant strain by two-dimensional polyacrylamide gel electrophoresis showed a significant increase in the level of expression of a protein (named OprR) whose molecular mass was approximately 26 kDa. The actual function of OprR is not yet clear; however, OprR was expected to be an outer membrane-associated protein with homology to lipoproteins of other bacterial species, according to a search of the National Center for Biotechnology Information website with the BLAST program by use of the N-terminal sequence of OprR. A correlation between the level of expression of OprR and the level of resistance ofP. aeruginosato QACs was observed by using a PA2800 gene knockout mutant derived from the P-12-resistant strain. The knockout mutant recovered susceptibility not only to P-12 but also to BAC. These results suggested that OprR significantly participated in the adaptation ofP. aeruginosato QACs, such as P-12 and BAC.
Influences of Methodological Variables on Susceptibility Testing of Caspofungin against
Candida
Species and
Aspergillus fumigatus
Authors: Bartizal C. , Odds F. C.
Published: June 2003

The influences of test variables on the outcome of susceptibility testing with caspofungin were tested with isolates of
Candida
spp. and
Aspergillus fumigatus
. Among six growth conditions tested with a range of inoculum sizes, the highest control growth yields were obtained in Sabouraud broth for all fungi, followed by RPMI 1640 (pH 7) for
Candida
spp. and antibiotic medium 3 (AM3) for
A. fumigatus
. RPMI 1640 gave unacceptably low growth yields with
A. fumigatus
. The caspofungin MICs under these various conditions ranged over more than 4 twofold dilutions for 7 of 16 fungi tested when a 50% inhibition (50% inhibitory concentration [IC
50
]) endpoint was used and for 12 of 16 fungi tested when an 80% inhibition (IC
80
) endpoint was used. A multifactorial design to study the influences of six test variables on control growth and the MIC showed that, for 14 isolates of
Candida
spp., the glucose concentration and the medium composition were the most common factors significantly influencing both control growth yields and the MIC. For eight
A. fumigatus
isolates, incubation time (24 versus 48 h) and temperature (30 versus 35°C) significantly affected control optical density (OD) values, while growth medium (AM3 versus Sabouraud broth) was the most common process variable affecting the MICs. Tests with AM3 from three suppliers showed significant variations in control OD values related to supplier, but IC
50
s fell within a 2- or 3-dilution range for 19 (86%) of the 22 isolates tested. We recommend that, at present, AM3 is superior to RPMI 1640 for testing of the susceptibilities of both yeasts and filamentous fungi to caspofungin and that a minimum incubation time of 48 h is necessary to test
A. fumigatus
adequately.
Chemosensitization of
Plasmodium falciparum
by Probenecid In Vitro
Authors: Nzila Alexis , Mberu Eddy , Bray Pat , Kokwaro Gilbert , Winstanley Peter , Marsh Kevin , Ward Steve
Published: June 2003

Resistance to drugs can result from changes in drug transport, and this resistance can sometimes be overcome by a second drug that modifies the transport mechanisms of the cell. This strategy has been exploited to partly reverse resistance to chloroquine in
Plasmodium falciparum
. Studies with human tumor cells have shown that probenecid can reverse resistance to the antifolate methotrexate, but the potential for reversal of antifolate resistance has not been studied in
P. falciparum.
In the present study we tested the ability of probenecid to reverse antifolate resistance in
P. falciparum
in vitro. Probenecid, at concentrations that had no effect on parasite viability alone (50 μM), was shown to increase the sensitivity of a highly resistant parasite isolate to the antifolates pyrimethamine, sulfadoxine, chlorcycloguanil, and dapsone by seven-, five-, three-, and threefold, respectively. The equivalent effects against an antifolate-sensitive isolate were activity enhancements of approximately 3-, 6-, 1.2-, and 19-fold, respectively. Probenecid decreased the level of uptake of radiolabeled folic acid, suggesting a transport-based mechanism linked to folate salvage. When probenecid was tested with chloroquine, it chemosensitized the resistant isolate to chloroquine (i.e., enhanced the activity of chloroquine). This enhancement of activity was associated with increased levels of chloroquine accumulation. In conclusion, we have shown that probenecid can chemosensitize malaria parasites to antifolate compounds via a mechanism linked to reduced folate uptake. Notably, this effect is observed in both folate-sensitive and -resistant parasites. In contrast to the activities of antifolate compounds, the effect of probenecid on chloroquine sensitivity was selective for chloroquine-resistant parasites (patent P407595GB [W. P. Thompson & Co., Liverpool, United Kingdom] has been filed to protect this intellectual property).
Synergistic Antimicrobial Activity of Metabolites Produced by a Nonobligate Bacterial Predator
Authors: Cain Cody C. , Lee Dongho , Waldo Robert H. , Henry Alexis T. , Casida Earl J. , Wani Mansukh C. , Wall Monroe E. , Oberlies Nicholas H. , Falkinham Joseph O.
Published: June 2003

A naturally occurring, gram-negative, nonobligate predator bacterial strain 679-2, exhibits broad-spectrum antimicrobial activity that is due, in part, to the production of three extracellular compounds. Antimicrobial-activity-directed fractionation of a culture of strain 679-2 against a panel of microorganisms has led to the isolation of three compounds: pyrrolnitrin, maculosin, and a new compound, which we have named banegasine. Although pyrrolnitrin is well known in the literature, it has not been found in cells with the herbicide maculosin. Further, this is the first report of production of maculosin by a prokaryote. Both maculosin and banegasine, which displayed no antimicrobial activities alone, were found to potentiate the antimicrobial activity of pyrrolnitrin. Based on 16S rRNA sequence, cellular fatty acid composition, and biochemical and cultural characteristics, strain 679-2 appears to represent a new genus and species of eubacteria,
Aristabacter necator
. The potent, broad-spectrum antimicrobial activity of predator strain 679-2 may be due to synergism between metabolites.
Persistent Bacteremia in Rabbit Fetuses despite Maternal Antibiotic Therapy in a Novel Intrauterine-Infection Model
Authors: Gras-Le Guen C. , Debillon T. , Toquet C. , Jarry A. , Winer N. , Jacqueline C. , Kergueris M. F. , Bingen E. , Roze J. C. , Potel G. , Bugnon D.
Published: June 2003

The effect of optimized maternal therapy by bactericidal agents was evaluated in a reproducible rabbit model ofEscherichia colimaternofetal infection simulating human pharmacokinetics. Intravenous antibiotic therapy was begun in the pregnant rabbit 12 h after bacterial intrauterine inoculation, using a computer-controlled pump to simulate human pharmacokinetics of ceftriaxone (1 g/day) associated or not with gentamicin (3 mg/kg of body weight/day). Data were compared for fetal survival, quantitative blood cultures, fetal histology in treated versus untreated groups, and maternal and fetal antibiotic concentrations in plasma in treated animals. Antibiotic therapy led to dramatic improvement in maternal outcome (100% survival versus 100% death in the untreated group in association with maternal septicemia). Fetal survival also improved, with the two-drug combination providing a more potent effect. After 3 days of treatment, 32% of fetuses survived with one-drug therapy and 62% with two-drug therapy (Yates corrected χ2,P< 0.05). In untreated animals, bacterial counts in blood cultures increased rapidly during the first 24 h up to 8.1 ± 0.5 log CFU/ml, but remained relatively constant at all times with antibiotic treatment: 4.5 ± 0.7 log CFU/ml at the start of treatment and 6.2 ± 0.4 and 5.2 ± 0.9 log CFU/ml after 72 h for one- and two-drug therapy, respectively (data are means ± standard deviations). The failure of animals to be cured after 3 days of treatment was not due to an inadequate concentration of ceftriaxone, as the residual level in fetal serum at sacrifice was more than 1,000 times the MIC of the microbe. Unexpectedly, inflammation in fetal lung decreased in the treated group after as little as 24 h of antibiotic therapy, despite persistent bacteremia. Although maternal outcome improved and drug concentrations were above the MIC, the treatment did not achieve sterilization of fetuses in utero for this rabbitE. colimaternofetal infection. However, fetal survival showed some improvement, and the histologic features of lung inflammation were reduced.
Effects of Ritonavir on Indinavir Pharmacokinetics in Cerebrospinal Fluid and Plasma
Authors: Haas David W. , Johnson Benjamin , Nicotera Janet , Bailey Vicki L. , Harris Victoria L. , Bowles Farideh B. , Raffanti Stephen , Schranz Jennifer , Finn Tyler S. , Saah Alfred J. , Stone Julie
Published: June 2003

Therapeutic control of human immunodeficiency virus type 1 (HIV-1) in peripheral compartments does not assure control in the central nervous system. Inadequate drug penetration may provide a sanctuary from which resistant virus can emerge or allow development of psychomotor abnormalities. To characterize the effect of ritonavir on indinavir disposition into cerebrospinal fluid, seven HIV-infected adults underwent intensive sampling at steady-state while receiving twice-daily indinavir (800 mg) and ritonavir (100 mg). Serial cerebrospinal fluid and plasma samples were obtained at 10 time points from each subject. Free indinavir accounted for 98.6% of drug in cerebrospinal fluid and 55.9% in plasma. Mean cerebrospinal fluid
C
max
,
C
min
, and area under the concentration-time curve from 0 to 12 h (AUC
0-12
) values for free indinavir were 735 nM, 280 nM, and 6,502 nM h
−1
, respectively, and the free levels exceeded 100 nM in every sample. The cerebrospinal fluid/plasma AUC
0-12
ratio for free indinavir was 17.5% ± 6.4%. This ratio was remarkably similar to results obtained in a previous study in which subjects received indinavir without ritonavir, indicating that ritonavir did not have a substantial direct effect on the barrier to indinavir penetration into cerebrospinal fluid. Low-dose ritonavir increases cerebrospinal fluid indinavir concentrations substantially more than 800 mg of indinavir given thrice daily without concomitant ritonavir, despite a lower total daily indinavir dose.
Telithromycin- and Fluoroquinolone-Resistant
Streptococcus pneumoniae
in Taiwan with High Prevalence of Resistance to Macrolides and β-Lactams: SMART Program 2001 Data
Authors: Hsueh Po-Ren , Teng Lee-Jene , Wu Tsu-Lan , Yang Dine , Huang Wen-Kuei , Shyr Jainn-Ming , Chuang Yin-Ching , Wan Jen-Hsien , Yan Jing-Jou , Lu Jang-Jih , Wu Jiunn-Jong , Ko Wen-Chien , Chang Feng-Yee , Yang Yi-Chueh , Lau Yeu-Jun , Liu Yung-Ching , Lee Chun-Ming , Leu Hsieh-Shong , Liu Cheng-Yi , Luh Kwen-Tay
Published: June 2003

There is a high prevalence of β-lactam- and macrolide-resistant
Streptococcus pneumoniae
in Taiwan. To understand the in vitro susceptibilities of recent isolates of
S. pneumoniae
to fluoroquinolones and telithromycin (which is not available in Taiwan), the MICs of 23 antimicrobial agents for 936 clinical isolates of
S. pneumoniae
isolated from different parts of Taiwan from 2000 to 2001 were determined by the agar dilution method. Overall, 72% of isolates were not susceptible to penicillin (with 61% being intermediate and 11% being resistant) and 92% were resistant to erythromycin. Telithromycin MICs were ≥1 μg/ml for 16% of the isolates, and for 99% of these isolates the MICs of all macrolides tested were ≥256 μg/ml; all of these isolates had the constitutive macrolide-lincosamide-streptogramin B phenotype. Eighty-eight percent of the isolates were resistant to three or more classes of drugs. The ciprofloxacin MICs were ≥4 μg/ml for six (0.6%) isolates from five patients collected in 2000 and 2001, and the levofloxacin MICs were ≥8 μg/ml for five of these isolates. Seven isolates for which ciprofloxacin MICs were ≥4 μg/ml, including one isolate recovered in 1999, belonged to three serotypes (serotype 19F, five isolates; serotype 23A, one isolate; and serotype 23B, one isolate). The isolates from the six patients for which ciprofloxacin MICs were ≥4 μg/ml had different pulsed-field gel electrophoresis profiles and random amplified polymorphic DNA patterns, indicating that no clonal dissemination occurred over this time period. Despite the increased rate of fluoroquinolone use, the proportion of pneumococcal isolates for which ciprofloxacin MICs were elevated (≥4 μg/ml) remained low. However, the occurrence of telithromycin resistance is impressive and raises concerns for the future.
Telithromycin and Quinupristin-Dalfopristin Resistance in Clinical Isolates of
Streptococcus pyogenes
: SMART Program 2001 Data
Authors: Hsueh Po-Ren , Teng Lee-Jene , Lee Chun-Ming , Huang Wen-Kuei , Wu Tsu-Lan , Wan Jen-Hsien , Yang Dine , Shyr Jainn-Ming , Chuang Yin-Ching , Yan Jing-Jou , Lu Jang-Jih , Wu Jiunn-Jong , Ko Wen-Chien , Chang Feng-Yee , Yang Yi-Chueh , Lau Yeu-Jun , Liu Yung-Ching , Leu Hsieh-Shong , Liu Cheng-Yi , Luh Kwen-Tay
Published: June 2003

This study evaluated the current status of antimicrobial resistance in clinical isolates of
Streptococcus pyogenes
in Taiwan as part of the SMART (Surveillance from Multicenter Antimicrobial Resistance in Taiwan) program. In 2001, 419 different isolates of
S. pyogenes
, including 275 from respiratory secretions, 87 from wound pus, and 31 from blood, were collected from nine hospitals in different parts of Taiwan. MICs of 23 antimicrobial agents were determined at a central location by the agar dilution method. All of the isolates were susceptible to penicillin (MIC at which 90% of the isolates were inhibited [MIC
90
], ≤0.03 μg/ml), cefotaxime (MIC
90
, ≤0.03 μg/ml), cefepime (MIC
90
, 0.06 μg/ml), meropenem (MIC
90
, ≤0.03 μg/ml), moxifloxacin (MIC
90
, 0.25 μg/ml), vancomycin (MIC
90
, 0.5 μg/ml), and linezolid (MIC
90
, 1 μg/ml). Overall, 78% of isolates were not susceptible to erythromycin (54% were intermediate, and 24% were resistant), and 5% were not susceptible to clindamycin. Of the 101 erythromycin-resistant isolates, 80.2% exhibited the M phenotype (
mefA
gene positive), 18.9% exhibited the cMLS (constitutive resistance to macrolides-lincosamides-streptogramin B [MLS]) phenotype (
ermB
gene positive), and 1% exhibited the iMLS (inducible resistance to MLS) phenotype (
ermB
gene positive). Fluoroquinolones (sitafloxacin > moxifloxacin > ciprofloxacin = levofloxacin = gatifloxacin > gemifloxacin) demonstrated potent activity against nearly all of the isolates of
S. pyogenes
tested. Thirty-two isolates (8%) were not susceptible to quinupristin-dalfopristin. Seventeen percent of isolates had telithromycin MICs of ≥1 μg/ml, and all of these isolates exhibited erythromycin MICs of ≥32 μg/ml. The high prevalence of resistance to telithromycin (which is not available in Taiwan) limits its potential use in the treatment of
S. pyogenes
infections, particularly in areas with high rates of macrolide resistance.
Effect of Calcium Carbonate on Bioavailability of Orally Administered Gemifloxacin
Authors: Pletz M. W. , Petzold P. , Allen A. , Burkhardt O. , Lode H.
Published: June 2003

We investigated the effect of calcium carbonate on the oral bioavailability of gemifloxacin. Gemifloxacin was administered alone, 2 h before, simultaneously, or 2 h after calcium carbonate in 16 volunteers. Data for 320 mg of gemifloxacin alone were as follows: maximum concentration of drug in serum (
C
max
),13 μg/ml; half-life, 7.33 h; and area under the concentration-time curve from 0 h to infinity (AUC
∞
), 6.79 μg · h/ml. Only simultaneous coadministration of calcium carbonate reduced
C
max
(−17%) and AUC
∞
(−21%) significantly.
Isolation and Molecular Characterization of Nalidixic Acid-Resistant Extraintestinal Pathogenic
Escherichia coli
from Retail Chicken Products
Authors: Johnson James R. , Murray Andrew C. , Gajewski Abby , Sullivan Maureen , Snippes Paula , Kuskowski Michael A. , Smith Kirk E.
Published: June 2003

Fluoroquinolone use in poultry production may select for resistant
Escherichia coli
that can be transmitted to humans. To define the prevalence and virulence potential of poultry-associated, quinolone-resistant
E. coli
in the United States, 169 retail chicken products from the Minneapolis-St. Paul area (1999 to 2000) were screened for nalidixic acid (Nal)-resistant
E. coli
. Sixty-two (37%) products yielded Nal-resistant
E. coli
. From 55 products that yielded both Nal-resistant and susceptible
E. coli
, two isolates (one resistant, one susceptible) per sample were further characterized. Twenty-three (21%) of the 110
E. coli
isolates (13 resistant, 10 susceptible) satisfied criteria for extraintestinal pathogenic
E. coli
(ExPEC), i.e., exhibited ≥2 of
pap
(P fimbriae),
sfa/foc
(S/F1C fimbriae),
afa/dra
(Dr binding adhesins),
iutA
(aerobactin receptor), and
kpsMT
II (group 2 capsule synthesis). Compared with other isolates, ExPEC isolates more often derived from virulence-associated
E. coli
phylogenetic groups B2 or D (74% versus 32%;
P
< 0.001) and exhibited more ExPEC-associated virulence markers (median, 10.0 versus 4.0;
P
< 0.001). In contrast, the Nal-resistant and -susceptible populations were indistinguishable according to all characteristics analyzed, including pulsed-field gel electrophoresis profiles. These findings indicate that Nal-resistant
E. coli
is prevalent in retail poultry products and that a substantial minority of such strains represent potential human pathogens. The similarity of the Nal-resistant and -susceptible populations suggests that they derive from the same source population, presumably the avian fecal flora, with Nal resistance emerging by spontaneous mutation as a result of fluoroquinolone exposure.
High-Level β-Lactam Resistance Associated with Acquired Multidrug Resistance in
Helicobacter pylori
Authors: Kwon Dong H. , Dore M. P. , Kim J. J. , Kato M. , Lee M. , Wu J. Y. , Graham D. Y.
Published: June 2003

Four clinical
Helicobacter pylori
isolates with high-level resistance to β-lactams exhibited low- to moderate-level resistance to the structurally and functionally unrelated antibiotics ciprofloxacin, chloramphenicol, metronidazole, rifampin, and tetracycline. This pattern of multidrug resistance was transferable to susceptible
H. pylori
by natural transformation using naked genomic DNA from a clinical multidrug-resistant isolate. Acquisition of the multidrug resistance was also associated with a change in the genotype of the transformed multidrug-resistant
H. pylori
. DNA sequence analyses of the gene encoding penicillin binding protein 1A (PBP 1A) showed 36 nucleotide substitutions resulting in 10 amino acid changes in the C-terminal portion (the putative penicillin binding domain). Acquisition of β-lactam resistance was consistently associated with transfer of a mosaic block containing the C-terminal portion of PBP 1A. No changes of genes
gyrA
,
rpoB
,
rrn16S
,
rdxA
, and
frxA,
and nine other genes (
ftsI
,
hcpA
,
llm
,
lytB
,
mreB
,
mreC
,
pbp2
,
pbp4
, and
rodA1
) encoding putative PBPs or involved in cell wall synthesis were found among the transformed resistant
H. pylori
. Antibiotic accumulations of chloramphenicol, penicillin, and tetracycline were all significantly decreased in the natural and transformed resistant
H. pylori
compared to what was seen with susceptible
H. pylori.
Natural transformation also resulted in the outer membrane protein profiles of the transformed resistant
H. pylori
becoming similar to that of the clinical resistant
H. pylori
isolates. Overall, these results demonstrate that high-level β-lactam resistance associated with acquired multidrug resistance in clinical
H. pylori
is mediated by combination strategies including alterations of PBP 1A and decreased membrane permeability.
Survey of Plasmid-Associated Genetic Markers in
Enterobacteriaceae
with Reduced Susceptibilities to Cephalosporins
Authors: Preston Karen E. , Graffunder Eileen M. , Evans Ann M. , Venezia Richard A.
Published: June 2003

Clinical isolates of
Enterobacteriaceae
with reduced susceptibilities to cephalosporins were collected from 1993 to 2000. The organisms were screened for the extended-spectrum β-lactamase (ESBL) phenotype, and plasmid extracts were screened for genetic markers by hybridization. A
bla
TEM
probe was derived from pUC19; other probes were derived from pACM1, the plasmid responsible for the first known appearance of an ESBL in our institution. These probes included
bla
SHV
,
int
,
aac(3)-Ia
,
dfrA1
, IS
6100
,
tetA
, IncM markers, and Anon 13, a marker for the
Klebsiella pneumoniae
chromosomal sequences that flank
bla
SHV-5
. There were 42 hybridization patterns among 237 isolates. Patterns designated pACM1-like occurred in 44% of the isolates (eight species) and were always associated with the clavulanic acid (CA)-susceptible ESBL phenotype. The TEM marker was not predictive of the ESBL phenotype. Mapping indicated the presence of an SHV marker and up to 7.5 kb of its flanking chromosomal sequences in three non-IncM plasmids obtained in transformation experiments. We theorize that this DNA segment spread to other plasmids from pACM1-like sources. CA insensitivity became more frequent with time and was usually associated with either the TEM marker or the absence of both
bla
markers. One plasmid-encoded enzyme with characteristics of an AmpC β-lactamase was observed in a transformant lacking both TEM and SHV markers. Although SHV type ESBLs were a continuing source of reduced susceptibility to cephalosporins in our institution, organisms with different resistance mechanisms were added to the hospital microflora in later years. These changes might be related, in part, to ESBL control strategies implemented in 1995.
In Vitro Activities of Benzimidazole
d
- and
l
-Ribonucleosides against Herpesviruses
Authors: Williams Stephanie L. , Hartline Caroll B. , Kushner Nicole L. , Harden Emma A. , Bidanset Deborah J. , Drach John C. , Townsend Leroy B. , Underwood Mark R. , Biron Karen K. , Kern Earl R.
Published: June 2003

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), and human herpesvirus 8 (HHV-8) are responsible for a number of clinical manifestations in both normal and immunocompromised individuals. The parent benzimidazole ribonucleosides evaluated in this series, 2-bromo-5,6-dichloro-1-(β-
d
-ribofuranosyl)benzimidazole (BDCRB) and maribavir (1263W94), are potent and selective inhibitors of human CMV replication. These nucleosides act by two different mechanisms. BDCRB blocks the processing and maturation of viral DNA, whereas 1263W94 inhibits the viral enzyme pUL97 and interferes with DNA synthesis. In the present study, we have evaluated the in vitro antiviral activity of BDCRB, an analog, GW275175X (175X), and 1263W94 against the replication of HSV-1, HSV-2, VZV, CMV, EBV, HHV-6, and HHV-8. By using various methodologies, significant activity was observed against human CMV and EBV but not against HSV-1, HSV-2, VZV, HHV-6, or HHV-8. Plaque reduction assays performed on a variety of laboratory and clinical isolates of human CMV indicated that all strains, including those resistant to ganciclovir (GCV) and foscarnet, were sensitive to all three benzimidazole ribonucleosides, with mean 50% effective concentration values of about 1 to 5 μM compared to that of GCV at 6 μM. The toxicity of these compounds in tissue culture cells appeared to be similar to that observed with GCV. These results demonstrate that the benzimidazole ribonucleosides are active against human CMV and EBV and suggest that they may be useful for the treatment of infections caused by these herpesviruses.
Evaluation of Nucleoside Phosphonates and Their Analogs and Prodrugs for Inhibition of Orthopoxvirus Replication
Authors: Keith Kathy A. , Hitchcock Michael J. M. , Lee William A. , Holý Antonin , Kern Earl R.
Published: June 2003

In the event of a bioterrorism attack using smallpox virus, there currently is no approved drug for the treatment of infections with this virus. We have reported previously that (
S
)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC) (also known as cidofovir [CDV]) has good activity against poxvirus infections; however, a major limitation is the requirement for intravenous administration. Two related acyclic nucleoside phosphonates (ANPs), adefovir (PMEA) and tenofovir (PMPA), are active against human immunodeficiency virus or hepatitis B virus but do not have activity against the orthopoxviruses. Therefore, we have evaluated a number of analogs and potential oral prodrugs of these three compounds for their ability to inhibit the replication of vaccinia virus or cowpox virus in tissue culture cells. The most-active compounds within the CDV series were (
S
)-HPMPA and (butyl
l
-alaninyl) cyclic HPMPC, with 50% effective concentrations (EC
50
s) from 4 to 8 μM, compared with 33 to 43 μM for CDV. Although PMEA itself was not active, adefovir dipivoxil {bis[(pivaloyl)oxymethyl] PMEA} and bis(butyl
l
-alaninyl) PMEA were active against both viruses, and bis(butyl
l
-alaninyl) PME-N6-(cyclopropyl)DAP and (isopropyl
l
-alaninyl)phenyl PME-N6-(cyclopropyl)DAP were the most active compounds tested, with EC
50
s of 0.1 to 2.6 μM. In the PMPA series, none of the analogs tested had significantly better activity than PMPA itself. These data indicate that a number of these ANP derivatives have activity against vaccinia virus and cowpox virus in vitro and should be evaluated for their efficacies in animal models.
Tolerability of Azithromycin as Malaria Prophylaxis in Adults in Northeast Papua, Indonesia
Authors: Taylor Walter R. , Richie Thomas L. , Fryauff David J. , Ohrt Colin , Picarima Helena , Tang Douglas , Murphy Gerald S. , Widjaja Hendra , Braitman David , Tjitra Emiliana , Ganjar Asep , Jones Trevor R. , Basri Hasan , Berman Josh
Published: June 2003

Drug tolerability affects compliance. We evaluated the tolerability levels of azithromycin (750-mg loading dose plus 250 mg/day;
n
= 148 subjects), doxycycline (100 mg/day;
n
= 75), and placebo (
n
= 77) as prophylaxis against malaria in Indonesian adults over 20 weeks. Self-reported and elicited symptoms, health perception, hearing, hematology, and biochemistry were assessed. The loading dose was well tolerated. The frequencies (number per person-years [p-yr]) of all daily reported symptoms were similar in the three arms of the study: 40.2/p-yr for azithromycin, 39.7/p-yr for doxycycline, and 38.2/p-yr for placebo. Relative to those who received placebo, azithromycin recipients complained more often of heartburn (rate ratio = 10.5 [95% confidence interval, 2.8 to 88.1]), paresthesia (2.03 [1.08 to 4.24]), and mild (1.55 [1.01 to 2.48]) and severe (11.2 [1.34 to ∞]) itching but less often of fever (0.21 [0.09 to 0.49]) and tinnitus (0.09 [0.04 to 0.21]). Azithromycin recipients showed no evidence of clinical hearing loss or hematologic, hepatic, or renal toxicity. One azithromycin recipient developed an erythematous rash. Daily azithromycin was well tolerated by these Indonesian adults during 20 weeks of treatment.
Preclinical Assessment of the Efficacy of Mycograb, a Human Recombinant Antibody against Fungal HSP90
Authors: Matthews Ruth C. , Rigg Gordon , Hodgetts Samantha , Carter Tracey , Chapman Caroline , Gregory Carl , Illidge Chris , Burnie James
Published: June 2003

Mycograb (
Neu
Tec Pharma plc) is a human genetically recombinant antibody against fungal heat shock protein 90 (HSP90). Antibody to HSP90 is closely associated with recovery in patients with invasive candidiasis who are receiving amphotericin B (AMB). Using in vitro assays developed for efficacy assessment of chemotherapeutic antifungal drugs, Mycograb showed activity against a wide range of yeast species (MICs against
Candida albicans
[fluconazole {FLC}-sensitive and FLC-resistant strains],
Candida krusei
,
Candida tropicalis
,
Candida glabrata
, and
Candida parapsilosis
, 128 to 256 μg/ml). Mycograb (4 or 8 μg/ml) showed synergy with AMB, the fractional inhibitory index being 0.09 to 0.31. Synergy was not evident with FLC, except for FLC-sensitive
C. albicans.
Murine kinetics showed that Mycograb at 2 mg/kg produced a maximum concentration of drug in serum of 4.7 μg/ml, a half-life at alpha phase of 3.75 min, a half-life at beta phase of 2.34 h, and an area under the concentration-time curve from 0 to
t
h of 155 μg · min/ml. Mycograb (2 mg/kg) alone produced significant improvement in murine candidiasis caused by each species: (i) a reduction (Scheffe's test,
P
< 0.05) in the mean organ colony count for the FLC-resistant strain of
C. albicans
(kidney, liver, and spleen),
C. krusei
(liver and spleen),
C. glabrata
(liver and spleen),
C. tropicalis
(kidney), and
C. parapsilosis
(kidney, liver, and spleen) and (ii) a statistically significant increase in the number of negative biopsy specimens (Fisher's exact test,
P
< 0.05) for
C. glabrata
(kidney),
C. tropicalis
(liver and spleen), and
C. parapsilosis
(liver). AMB (0.6 mg/kg) alone cleared the
C. tropicalis
infection but failed to clear infections caused by
C. albicans
,
C. krusei
,
C. glabrata
, or
C. parapsilosis.
Synergy with AMB, defined as an increase (Fisher's exact test,
P
< 0.05) in the number of negative biopsy specimens compared with those obtained using AMB alone, occurred with the FLC-resistant strain of
C. albicans
(kidney),
C. krusei
(spleen),
C. glabrata
(spleen), and
C. parapsilosis
(liver and spleen). Only by combining Mycograb with AMB was complete resolution of infection achieved for
C. albicans
,
C. krusei
, and
C. glabrata.
In Vitro and In Vivo Activities of Fluoroquinolones against
Aeromonas hydrophila
Authors: Ko Wen-Chien , Chiang Shyh-Ren , Lee Hsin-Chun , Tang Hung-Jen , Wang Yin-Yi , Chuang Yin-Ching
Published: June 2003

Aeromonas hydrophila
, an uncommon human pathogen, can cause invasive infections in immunocompromised individuals. As the fluoroquinolones have been shown to be active in vitro against mesophilic aeromonads and clinical experience with the use of fluoroquinolones to treat aeromonads infections is limited, the antimicrobial activities of five selected drugs (ciprofloxacin, gatifloxacin, levofloxacin, lomefloxacin, and moxifloxacin) against
A. hydrophila
were studied in vitro and in mice. The MICs of the fluoroquinolones (except lomefloxacin), cefotaxime, and minocycline for 90% of 64 clinical isolates of
A. hydrophila
tested by the agar dilution method were ≤1 μg/ml. With a clinical cefotaxime-resistant strain, Ah 2743, in an in vitro time-kill study, at an inoculum of 7 × 10
5
CFU/ml incubated with fluoroquinolones, cefotaxime, or minocycline at concentrations equal to twice the MICs, the inhibitory effect lasted for less than 6 h and regrowth occurred thereafter. In an animal model with female BALB/c mice intraperitoneally infected with an inoculum of 1.1 × 10
7
CFU of Ah 2743, more mice in the ciprofloxacin-treated group survived (72.2%) than in the cefotaxime-, minocycline-, or cefotaxime-minocycline-treated group (
P
< 0.00001, log rank test). However, there were similar fatality rates, ranging from 71.4 to 87.5%, among mice treated with any of five fluoroquinolones. With a larger inoculum, 4.9 × 10
7
CFU, mice in the ciprofloxacin-treated group survived longer than those in the minocycline-, cefotaxime-, or cefotaxime-minocycline-treated group (30 h versus 18, 12, and 12 h, respectively [
P
< 0.002, log rank test]). However, in mice infected with cefotaxime-susceptible Ah 2556, ciprofloxacin was as effective as cefotaxime-minocycline. Thus, our results suggest that ciprofloxacin is at least as effective as cefotaxime-minocycline against murine
A. hydrophila
infections, which warrants clinical studies to delineate its role in human infections.