bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic Structure Associated withblaOXA-18, Encoding a Clavulanic Acid-Inhibited Extended-Spectrum Oxacillinase
Authors: Naas Thierry , Namdari Fatemeh , Bogaerts Pierre , Huang Te-Din , Glupczynski Youri , Nordmann Patrice 
Published: July 2008

ABSTRACTThe genetic environment of theblaOXA-18gene encoding a peculiar clavulanic acid-inhibitable Ambler class D extended-spectrum β-lactamase was determined from the prototype OXA-18-producingPseudomonas aeruginosaMUS clinical isolate. An 8.2-kb genomic DNA fragment containingblaOXA-18was cloned fromP. aeruginosaMUS. Although most oxacillinases are located in integrons,blaOXA-18lacked gene cassette-specific features. It was bracketed by two duplicated sequences containing ISCR19, a novel insertion sequence of the ISCRfamily of mobile elements; ΔintI1, a truncated integrase gene; and a truncated Δaac6′-Ibgene cassette. It is likely that ISCR19was at the origin of theblaOXA-18gene mobilization by a rolling-circle transposition event followed by homologous recombination. Furthermore, analysis of the cloned genomic DNA fragment revealed the presence of the integron-containingblaOXA-20gene. Concomitantly, threeP. aeruginosaclinical isolates, displaying a synergy image as determined by double-disk diffusion tests on cloxacillin-containing plates, were isolated from three patients hospitalized in different wards over a 9-month period at the Saint-Luc University hospital (Brussels, Belgium). These isolates were positive by PCR forblaOXA-18andblaOXA-20genes, genetically related toP. aeruginosaMUS as determined by pulsed-field gel electrophoresis, and carried the sameblaOXA-18/blaOXA-20-associated genetic structures. This report characterized the genetic elements likely at the origin ofblaOXA-18gene mobilization inP. aeruginosaand suggests the spread of oxacillin-type extended-spectrum β-lactamases inP. aeruginosaat the Saint-Luc University hospital of Brussels, Belgium.
Evolution of the IS
CR3
Group of IS
CR
Elements
Authors: Toleman Mark A. , Walsh Timothy R. 
Published: July 2008

ABSTRACT

The IS
CR
elements IS
CR3
, IS
CR4
, IS
CR5
, IS
CR14
, and IS
CR16
all share a percent G+C of 68 to 69%. They also share between 75% and 97% identity in their transposase open reading frames. Furthermore, with the exception of IS
CR5
, they are all found adjacent to sections of
groEL
that display the highest identity to the same gene from
Xanthomonas
spp. The combined information is consistent with the descent from an ancestral IS
CR
element in a
Xanthomonas
-like organism.
Microbial Growth Inhibition by Alternating Electric Fields
Authors: Giladi Moshe , Porat Yaara , Blatt Alexandra , Wasserman Yoram , Kirson Eilon D. , Dekel Erez , Palti Yoram 
Published: July 2008

ABSTRACT

Weak electric currents generated using conductive electrodes have been shown to increase the efficacy of antibiotics against bacterial biofilms, a phenomenon termed “the bioelectric effect.” The purposes of the present study were (i) to find out whether insulated electrodes that generate electric fields without “ohmic” electric currents, and thus are not associated with the formation of metal ions and free radicals, can inhibit the growth of planktonic bacteria and (ii) to define the parameters that are most effective against bacterial growth. The results obtained indicate that electric fields generated using insulated electrodes can inhibit the growth of planktonic
Staphylococcus aureus
and
Pseudomonas aeruginosa
and that the effect is amplitude and frequency dependent, with a maximum at 10 MHz. The combined effect of the electric field and chloramphenicol was found to be additive. Several possible mechanisms underlying the observed effect, as well as its potential clinical uses, are discussed.
Surveillance of Community-Based Reservoirs Reveals the Presence of CTX-M, Imported AmpC, and OXA-30 β-Lactamases in Urine Isolates of
Klebsiella pneumoniae
and
Escherichia coli
in a U.S. Community
Authors: Hanson Nancy D. , Moland Ellen Smith , Hong S. G. , Propst Katie , Novak Deborah J. , Cavalieri Stephen J. 
Published: July 2008

ABSTRACT

β-Lactamases produced by urine isolates from patients in long-term care facilities (LTCFs), outpatient, clinics, and one hospital in a U.S. community were characterized. A total of 1.3% of all
Escherichia coli
and
Klebsiella pneumoniae
isolates collected from patients in 30 LTCFs and various outpatient clinics produced extended-spectrum β-lactamases (ESBLs) and/or imported AmpC β-lactamases.
Rχ-01, a New Family of Oxazolidinones That Overcome Ribosome-Based Linezolid Resistance
Authors: Skripkin Eugene , McConnell Timothy S. , DeVito Joseph , Lawrence Laura , Ippolito Joseph A. , Duffy Erin M. , Sutcliffe Joyce , Franceschi François 
Published: July 2008

ABSTRACTNew and improved antibiotics are urgently needed to combat the ever-increasing number of multidrug-resistant bacteria. In this study, we characterized several members of a new oxazolidinone family, Rχ-01. This antibiotic family is distinguished by having in vitro and in vivo activity against hospital-acquired, as well as community-acquired, pathogens. We compared the 50S ribosome binding affinity of this family to that of the only marketed oxazolidinone antibiotic, linezolid, using chloramphenicol and puromycin competition binding assays. The competition assays demonstrated that several members of the Rχ-01 family displace, more effectively than linezolid, compounds known to bind to the ribosomal A site. We also monitored binding by assessing whether Rχ-01 compounds protect U2585 (Escherichia colinumbering), a nucleotide that influences peptide bond formation and peptide release, from chemical modification by carbodiimide. The Rχ-01 oxazolidinones were able to inhibit translation of ribosomes isolated from linezolid-resistantStaphylococcus aureusat submicromolar concentrations. This improved binding corresponds to greater antibacterial activity against linezolid-resistant enterococci. Consistent with their ribosomal A-site targeting and greater potency, the Rχ-01 compounds promote nonsense suppression and frameshifting to a greater extent than linezolid. Importantly, the gain in potency does not impact prokaryotic specificity as, like linezolid, the members of the Rχ-01 family show translation 50% inhibitory concentrations that are at least 100-fold higher for eukaryotic than for prokaryotic ribosomes. This new family of oxazolidinones distinguishes itself from linezolid by having greater intrinsic activity against linezolid-resistant isolates and may therefore offer clinicians an alternative to overcome linezolid resistance. A member of the Rχ-01 family of compounds is currently undergoing clinical trials.
Type I Interferon Signaling ExacerbatesChlamydia muridarumGenital Infection in a Murine Model
Authors: Nagarajan Uma M. , Prantner Daniel , Sikes James D. , Andrews Charles W. , Goodwin Anna M. , Nagarajan Shanmugam , Darville Toni 
Published: July 2008

ABSTRACTType I interferons (IFNs) induced during in vitro chlamydial infection exert bactericidal and immunomodulatory functions. To determine the precise role of type I IFNs during in vivo chlamydial genital infection, we examined the course and outcome ofChlamydia muridarumgenital infection in mice genetically deficient in the receptor for type I IFNs (IFNAR−/−mice). A significant reduction in chlamydial shedding and duration of lower genital tract infection was observed in IFNAR−/−mice in comparison to the level of chlamydial shedding and duration of infection in wild-type (WT) mice. Furthermore, IFNAR−/−mice developed less chronic oviduct pathology in comparison to that in WT mice. Compared to the WT, IFNAR−/−mice had a greater number of chlamydial-specific T cells in their iliac lymph nodes 21 days postinfection. IFNAR−/−mice also exhibited earlier and enhanced CD4 T-cell recruitment to the cervical tissues, which was associated with increased expression of CXCL9 in the genital secretions of IFNAR−/−mice, but not with expression of CXCL10, which was reduced in the genital secretions of IFNAR−/−mice. These data suggest that type I IFNs exacerbateC. muridarumgenital infection through an inhibition of the chlamydial-specific CD4 T-cell response.
Chloroplast DNA diversity reveals the contribution of two wild species to the origin and evolution of diploid safflower (Carthamus tinctorius L.)
Authors: Sehgal Deepmala , Rajpal Vijay Rani , Raina Soom Nath 
Published: July 2008

The identity of the wild progenitor of one of the most important oil crop species, Carthamus tinctorius (2n = 2x = 24), commonly known as safflower, has been the subject of numerous studies at morphological, biochemical, cytogenetic, and biosystematic levels, but no definitive conclusions have been made. The nuclear, mitochondrial, and chloroplast genomes of the two botanical varieties of C. tinctorius, C. tinctorius var. tinctorius and C. tinctorius var. inermis, and two wild species, C. palaestinus and C. oxyacantha , were assayed at the nucleotide sequence level and by DNA markers. The nuclear and mitochondrial DNA assays were not helpful in conclusively identifying the diploid ancestor of C. tinctorius. The chloroplast DNA diversity, on the other hand, unambiguously provided new and novel evidence that C. palaestinus and C. oxyacantha contributed their plastomes to the evolution of C. tinctorius var. inermis and C. tinctorius var. tinctorius, respectively. This study, therefore, affirms a startling revelation of a rare event of two wild species contributing to the origin and evolution of safflower, a major world oilseed crop about whose genetics very little is known.
Variation in the seasonal selection of resources by woodland caribou in northern British Columbia
Authors: Gustine D. D. , Parker K. L. 
Published: July 2008

Conservation planning for species of concern or importance can be aided by resource selection functions (RSFs) that identify important areas or attributes. Models that can be interpreted biologically and provide reasonable predictive capacity may best be based on data from individuals grouped into seasonal selection strategies for particular geographical areas or similarities in topographical and vegetative associations. We used logistic regression, the information–theoretic approach, satellite imagery, and locational data (n = 31 females; 16 803 locations) from global positioning system (GPS) collared woodland caribou ( Rangifer tarandus caribou (Gmelin, 1788)) to model resource selection by animals during calving, summer, fall, breeding, winter, and late-winter seasons. Higher variation in resource use corresponded to times when caribou and their young were most susceptible to predation or when food resources were limited. Even with multiple selection strategies, caribou followed a general progression from higher to lower elevation habitats from calving and summer to late winter. Caribou selected against or completely avoided the burned–disturbed vegetation class in every season except summer. We incorporated RSFs with a raster geographic information system to create selection landscapes. We validated selection landscapes using withheld GPS data (n = 6077), 50 known calving sites, and Spearman’s rank correlation coefficient. Selection models and final selection landscapes performed well in validating use locations of woodland caribou in all seasons (all P < 0.003) and in predicting known calving sites (P < 0.001). When seasonal selection strategies are identified and models are coupled with validation, RSFs are effective tools to assist in conservation planning.
Effect of seasonal changes in upwelling activity on the foraging locations of a wide-ranging central-place forager, the New Zealand fur seal
Authors: Baylis A. M.M. , Page B. , Goldsworthy S. D. 
Published: July 2008

Lactating New Zealand fur seals ( Arctocephalus forsteri (Lesson, 1828)) that breed at Cape Gantheaume, South Australia, experience broad-scale seasonal changes in ocean productivity. To assess how seasonal changes in ocean productivity influenced foraging behaviour, 18 lactating New Zealand fur seals were fitted with satellite transmitters and time–depth recorders (TDRs). Using temperature and depth data from TDRs, we used the presence of thermoclines as a surrogate measure of upwelling activity in continental-shelf waters. During the austral autumn 80% of lactating fur seals foraged on the continental shelf (114 ± 44 km from the colony), in a region associated with the Bonney upwelling. In contrast, during winter months seals predominantly foraged in oceanic waters (62%), in a region associated with the Subtropical Front (460 ± 138 km from the colony). Our results indicate that lactating New Zealand fur seals shift their foraging location from continental-shelf to oceanic waters in response to a seasonal decline in productivity over the continental shelf, attributed to the cessation of the Bonney upwelling. This study identified two regions used by lactating New Zealand fur seals: (1) a nearby and seasonally productive upwelling system and (2) a distant and permanent oceanic front.
Expanding the horizon: the Red Queen and potential alternatives
Authors: Tobler M. , Schlupp I. 
Published: July 2008

The Red Queen hypothesis (RQH) is one of the most widely accepted hypotheses explaining the persistence of sexual reproduction despite its costs. It posits that sexual species, compared with asexuals, are more adept at countering parasites, because their per-generation recombination rate is higher. Despite theoretical support, current empirical studies have failed to provide unanimous support. Here, we suggest that future tests of the RQH should more thoroughly elucidate its underlying assumptions and potential alternative hypotheses. While the RQH predicts that negative frequency-dependent selection shapes host–parasite interactions, differences between sexuals and asexuals are potentially important. Key assumptions about asexual species and their sexual close relatives include (i) ecological and behavioral traits are similar, (ii) among-individual genetic diversity is greater in sexuals than in asexuals, and (iii) within-individual genetic diversity is similar in asexuals and sexuals. We review current evidence for the RQH, highlight differences between asexual and sexual species and how those differences might translate into differential responses to parasite infections, and discuss how they can influence the results and interpretation of empirical studies. Considering differences between asexual and sexual species in future tests of the RQH will help to refine predictions and eliminate alternative hypotheses.
Pupping-site fidelity among individual Steller sea lions (Eumetopias jubatus) at Chiswell Island, Alaska
Authors: Parker P. , Harvey J. T. , Maniscalco J. M. , Atkinson S. 
Published: July 2008

Pupping-site fidelity (defined as pupping within 5.8 m of a previous location in ≥2 years) in Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) was investigated during the breeding seasons from 2001 to 2005 at Chiswell Island, a small rookery in the Gulf of Alaska. Density of females was minimal with 54–80 pups born. Photo-identification of individuals and GPS points, including elevation of the rookery, were used to determine locations of 297 births. Sixty-four percentage (35/55) of the females exhibited pupping-site fidelity, and mean frequency of site fidelity was greater for females that gave birth >3 times. Fifty percentage of the births occurred at 22% of the locations for all years, indicating that multiple births occurred at some locations throughout the breeding season. Competition or aggression among females for specific pupping locations before birth was not observed, and there was no temporal order of pupping locations used, indicating that the rookery was not overcrowded and that many suitable pupping locations existed. Multiparous females gave birth at significantly greater distances from the surf zone than primiparous females. Long-term monitoring of pupping-site fidelity in combination with other measures of maternal care will ultimately determine which factors have the greatest effect on pup survival.
Cyclic dynamics of sympatric lemming populations on Bylot Island, Nunavut, Canada
Authors: Gruyer Nicolas , Gauthier Gilles , Berteaux Dominique 
Published: July 2008

We characterized the fluctuations (amplitude, periodicity) of two sympatric species, the brown lemming ( Lemmus sibiricus (Kerr, 1792)) and the northern collared lemming ( Dicrostonyx groenlandicus (Traill, 1823)), in a High Arctic area. Our objective was to determine if these populations were cyclic, and if fluctuations in numbers were synchronized between the two species temporally and spatially. An annual index of lemming abundance was obtained using snap-traps at two sites 30 km apart on Bylot Island (Nunavut, Canada) over 13 years (1993–2005) and 9 years (1997–2005), respectively. The time series were analyzed by spectral analyses and autoregressive modelling. At the site with the longest record, brown lemming showed regular population fluctuations of large amplitude (>40-fold), but collared lemming fluctuations were of much smaller amplitude (4-fold). At the other site, the collared lemming population was higher than at the main site, but brown lemmings were still most abundant in the peak year. Models with a second-order function obtained from a spectral analysis were highly correlated with the observed abundance index in both species at the site with the longest time series, and provide evidence of cyclic dynamic. The periods of the cycles were estimated at 3.69 ± 0.04 (SE) years for brown lemmings and 3.92 ± 0.24 (SE) years for collared lemmings, but the amplitude of the cycle was weak in the latter species. Fluctuations in abundance at the same site were relatively well synchronized between the two species, but the evidence for synchrony between sites was equivocal.
Genetic diversity and structure in Canadian northern leopard frog (Rana pipiens) populations: implications for reintroduction programs
Authors: Wilson G. A. , Fulton T. L. , Kendell K. , Scrimgeour G. , Paszkowski C. A. , Coltman D. W. 
Published: July 2008

The northern leopard frog ( Rana pipiens Schreber, 1782) underwent a large decline in the western portion of its range and only occurs in 20% of historically occupied sites in Alberta. Its absence may reflect an inability to disperse to these sites because of habitat fragmentation, and human-mediated translocation has been proposed. In this study, we used three criteria to examine the genetic suitability of potential translocation sources: diversity, similarity to area of reintroduction, and evolutionary history. We genotyped 187 samples and sequenced 812 bp of the mitochondrial NADH dehydrogenase 1 gene from 14 Canadian northern leopard frog populations. Nuclear and mitochondrial diversity were highest in Manitoba and western Ontario and declined westward. There was no significant relationship between genetic and geographic distance, suggesting that genetic drift is a driving force affecting the genetic relationships between populations. Regions separated by more than ~50 km were quite differentiated. Therefore, source populations similar to the original inhabitants of an area for reintroduction may be uncommon. Mitochondrial analyses revealed that all populations share a close evolutionary history, belonging to the western haplotype group. While genetic criteria support the use of Manitoba and Ontario as sources, the desirability of environmental similarity to the reintroduction site suggests that ecologically exchangeable Alberta populations should also be considered.
The effect of constant and fluctuating incubation temperatures on the phenotype of black ratsnakes (Elaphe obsoleta)
Authors: Patterson L. D. , Blouin-Demers G. 
Published: July 2008

According to the maternal manipulation hypothesis, females manipulate the phenotypes of their offspring by selecting favourable incubation conditions. In oviparous black ratsnakes ( Elaphe obsoleta Say in James, 1823), females manipulate offspring phenotype through nest-site selection. This study aimed to determine whether the thermal mean and variance of the incubation regime affect fitness-related traits in hatchlings. We incubated 136 eggs in a split-clutch design at two thermal means (26 and 29 °C) and variances (constant and ±3 °C). Hatchlings incubated at higher temperatures hatched earlier, were longer, faster, and less defensive. Hatchlings incubated at constant temperatures hatched earlier and were longer. For athletic performance, there was a significant interaction between temperature mean and variance: hatchlings incubated at 29 °C swam faster, had a lower muscular strength, and righted themselves equally fast when incubated at constant temperatures, whereas hatchlings incubated at 26 °C were stronger, swam faster, and righted themselves more slowly. Overall, constant incubation temperatures produced hatchlings with phenotypes favouring higher survival than fluctuating temperatures, but the effect of thermal variance was not as pronounced as the effect of thermal mean. Therefore, we found some support for the hypothesis that black ratsnakes prefer communal over single-female nests because communal nests have higher, more constant temperatures.
Correlates of postfledging survival, the timing of dispersal, and local recruitment in American Dippers
Authors: Middleton Holly A. , Green David J. 
Published: July 2008

Natal dispersal is a complex process that involves decisions about when to leave the natal territory, how to move through the landscape, and where to settle. We investigated what factors influence the timing of dispersal and local recruitment of American Dippers ( Cinclus mexicanus Swainson, 1827) in Chilliwack, British Columbia. We monitored 102 fledglings from 30 broods between 2003 and 2005. Survival to 5 days after fledging was high (>80%), but individuals fledging early in the season and at an older age had higher survival than those fledging later and younger. Fifty-four percentage of surviving fledglings dispersed within 14 days of nest departure. Females and individuals that spent more time foraging were more likely to disperse within 14 days than males and individuals that foraged less. For those that dispersed, individuals that fledged early in the season and at older ages spent less time in their natal territory. Approximately 10% (10/82) of dispersing individuals were known to recruit locally. Local recruitment of individuals that delayed dispersal was higher than local recruitment of individuals dispersing early. Our study demonstrates that fitness benefits associated with extended natal philopatry are not restricted to cooperatively breeding birds.