bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid Depletion of Free Vancomycin in Medium in the Presence of β-Lactam Antibiotics and Growth Restoration in
Staphylococcus aureus
Strains with β-Lactam-Induced Vancomycin Resistance
Authors: Yanagisawa Chie , Hanaki Hideaki , Matsui Hidehito , Ikeda Shinsuke , Nakae Taiji , Sunakawa Keisuke 
Published: October 2008

ABSTRACT

A class of methicillin-resistant
Staphylococcus aureus
strains shows vancomycin resistance in the presence of β-lactam antibiotics (β-lactam-induced VAN-resistant methicillin-resistant
S. aureus
[BIVR]). Two possible explanations may be offered: (i) vancomycin in culture medium is depleted, and (ii) the
d
-Ala-
d
-Ala terminal of the peptidoglycan network is replaced with
d
-Ala-
d
-lactate. We tested these hypotheses by quantifying free vancomycin in the medium through the course of cell growth and by PCR amplification of the
van
genes. Growth of the BIVR cells to an absorption level of ∼0.3 at 578 nm required about 24 h in the presence of vancomycin alone at the MIC (4.0 μg/ml). However, growth was achieved in only about 10 h when 1/1,000 to 1/2,000 the MIC of β-lactam antibiotic was added 2 h prior to the addition of vancomycin, suggesting that the β-lactams shortened the time to recovery from vancomycin-mediated growth inhibition. Free vancomycin in the culture medium decreased to 2.3 μg/ml in the first 8 h in the culture containing vancomycin alone, yet cell growth was undetectable. When the vancomycin concentration dropped below ∼1.5 μg/ml at 24 h, the cells began to grow. In the culture supplemented with the β-lactam 2 h prior to the addition of vancomycin, the drug concentration continuously dropped from 4 to 0.5 μg/ml in the first 8 h, and the cells began to grow at a vancomycin concentration of ∼1.7 μg/ml or at 4 h of incubation. The gene encoding the enzyme involved in
d
-Ala-
d
-lactate synthesis was undetectable. Based on these results, we concluded that BIVR is attributable mainly to a rapid depletion of vancomycin in the medium triggered or promoted by β-lactam antibiotics.
Widespread Dissemination of Aminoglycoside Resistance Genes
armA
and
rmtB
in
Klebsiella pneumoniae
Isolates in Taiwan Producing CTX-M-Type Extended-Spectrum β-Lactamases
Authors: Ma Ling , Lin Chi-Jan , Chen Jiun-Han , Fung Chang-Phone , Chang Feng-Yee , Lai Yiu-Kay , Lin Jung-Chung , Siu L. K. 
Published: October 2008

ABSTRACT

Among 235 extended-spectrum β-lactamase-producing
Klebsiella pneumoniae
(ESBL) isolates collected from a nationwide surveillance performed in Taiwan, 102 (43.4%) were resistant to amikacin. Ninety-two of these 102 (90.2%) isolates were carrying CTX-M-type β-lactamases individually or concomitantly with SHV-type or CMY-2 β-lactamases. The
armA
and
rmtB
alleles were individually detected in 44 and 37 of these 92 isolates, respectively. One isolate contained both
armA
and
rmtB
. The coexistence of the
aac(6′)-Il
and
rmtB
genes was detected in three isolates. CTX-M-type β-lactamase genes belonging to either group 1 (CTX-M-3 and CTX-M-15) or group 9 (CTX-M-14) were found in all
armA-
or
rmtB
-bearing ESBL-producing
K. pneumoniae
isolates, and all were conjugatively transferable. All except one of the isolates bearing
armA
produced CTX-M enzymes of group 1, and the remaining isolate bearing
armA
produced a group 9 CTX-M-type β-lactamase. On the contrary, in the majority of
rmtB
carriers, the CTX-M-type β-lactamase belonged to group 9 (62.2%). Molecular typing revealed that the amikacin-resistant ESBL-producing
K. pneumoniae
isolates were epidemiologically unrelated, indicating that the acquisition of resistance was not through the spread of a resistant clone or a resistance plasmid. A tandem repeat or multiple copies of
bla
CTX-M-3
were found in some
armA
-bearing isolates. An IS
Ecp1
insert was found in all CTX-M ESBL-producing
K. pneumoniae
isolates carrying
armA
or
rmtB
. In conclusion, the concomitant presence of a 16S rRNA methylase gene (
armA
or
rmtB
) and
bla
CTX-M
among amikacin-resistant ESBL-producing
K. pneumoniae
isolates is widespread in Taiwan.
High Prevalence of Plasmid-Mediated Quinolone Resistance Determinants
qnr
,
aac(6
′
)
-
Ib-cr
, and
qepA
among Ceftiofur-Resistant
Enterobacteriaceae
Isolates from Companion and Food-Producing Animals
Authors: Ma Junying , Zeng Zhenling , Chen Zhangliu , Xu Xiaogang , Wang Xiaoying , Deng Yuting , Lü Dianhong , Huang Liangzong , Zhang Yunyuan , Liu Jianhua , Wang Minggui 
Published: October 2008

ABSTRACT

Three kinds of plasmid-mediated quinolone resistance (PMQR) determinants have been discovered and have been shown to be widely distributed among clinical isolates:
qnr
genes,
aac(6
′
)-Ib-cr
, and
qepA
. Few data on the prevalence of these determinants in strains from animals are available. The presence of PMQR genes in isolates from animals was determined by PCR amplification and DNA sequencing. The production of extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases in the strains was detected, and their genotypes were determined. The genetic environment of PMQR determinants in selected plasmids was analyzed. All samples of ceftiofur-resistant (MICs ≥ 8 μg/ml) isolates of the family
Enterobacteriaceae
were selected from 36 companion animals and 65 food-producing animals in Guangdong Province, China, between November 2003 and April 2007, including 89
Escherichia coli
isolates, 9
Klebsiella pneumoniae
isolates, and isolates of three other genera. A total of 68.3% (69/101) of the isolates produced ESBLs and/or AmpC β-lactamases, mainly those of the CTX-M and CMY types. Of the 101 strains, PMQR determinants were present in 35 (34.7%) isolates, with
qnr, aac(6
′
)-Ib
-
cr
, and
qepA
detected alone or in combination in 8 (7.9%), 19 (18.8%), and 16 (15.8%) strains, respectively. The
qnr
genes detected included one
qnrB4
gene, four
qnrB6
genes, and three
qnrS1
genes. Five strains were positive for both
aac(6
′
)-Ib
-
cr
and
qepA
, while one strain was positive for
qnrS1, aac(6
′
)-Ib
-
cr
, and
qepA. qnrB6
was flanked by two copies of IS
CR1
with an intervening
dfr
gene downstream and
sul1
and
qacE
Δ
1
genes upstream. In another plasmid,
aac(6
′
)-Ib-cr
followed
intI1
and
arr-3
was downstream. PMQR determinants are highly prevalent in ceftiofur-resistant
Enterobacteriaceae
strains isolated from animals in China. This is the first report of the occurrence of PMQR determinants among isolates from companion animals.
Posaconazole Mono- or Combination Therapy for Treatment of Murine Zygomycosis
Authors: Ibrahim Ashraf S. , Gebremariam Teclegiorgis , Schwartz Julie A. , Edwards John E. , Spellberg Brad 
Published: October 2008

ABSTRACT

We compared the efficacy of combination posaconazole-liposomal amphotericin B (LAmB) therapy to monotherapy with either drug in diabetic ketoacidotic or neutropenic mice with disseminated zygomycosis caused by
Rhizopus oryzae
. Combination therapy was no better than LAmB alone, and posaconazole monotherapy did not improve survival or reduce fungal burden versus placebo.
Abelson Tyrosine Kinase Facilitates
Salmonella enterica
Serovar Typhimurium Entry into Epithelial Cells
Authors: Ly Kim Thien , Casanova James E. 
Published: October 2008

ABSTRACT

The intracellular gram-negative bacterial pathogen
Salmonella enterica
serovar Typhimurium gains entry into nonphagocytic cells by manipulating the assembly of the host actin cytoskeleton.
S. enterica
serovar Typhimurium entry requires a functional type III secretion system, a conduit through which bacterial effector proteins are directly translocated into the host cytosol. We and others have previously reported the enhancement of tyrosine kinase activities during
Salmonella
serovar Typhimurium infection; however, neither specific kinases nor their targets have been well characterized. In this study, we investigated the roles of the cellular Abelson tyrosine kinase (c-Abl) and the related protein Arg in the context of serovar Typhimurium infection. We found that bacterial internalization was inhibited by more than 70% in cells lacking both c-Abl and Arg and that treatment of wild-type cells with a pharmaceutical inhibitor of the c-Abl kinase, STI571 (imatinib), reduced serovar Typhimurium invasion efficiency to a similar extent. Bacterial infection led to enhanced phosphorylation of two previously identified c-Abl substrates, the adaptor protein CT10 regulator of kinase (CrkII) and the Abelson-interacting protein Abi1, a component of the WAVE2 complex. Furthermore, overexpression of the nonphosphorylatable form of CrkII resulted in decreased invasion. Taken together, these findings indicate that c-Abl is activated during
S. enterica
serovar Typhimurium infection and that its phosphorylation of multiple downstream targets is functionally important in bacterial internalization.
T-Cell Responses to the Trypanosome Variant Surface Glycoprotein Are Not Limited to Hypervariable Subregions
Authors: Dagenais Taylor R. , Demick Karen P. , Bangs James D. , Forest Katrina T. , Paulnock Donna M. , Mansfield John M. 
Published: October 2008

ABSTRACTVariable subregions within the variant surface glycoprotein (VSG) coat displayed by African trypanosomes are predicted sites for T- and B-cell recognition. Hypervariable subregion 1 (HV-1) is localized to an internal amphipathic alpha helix in VSG monomers and may have evolved due to selective pressure by host T-cell responses to epitopes within this subregion. The prediction of T-cell receptor-reactive sites and major histocompatibility complex class II binding motifs within the HV-1 subregion, coupled with the conservation of amino acid residues in other regions of the molecule sufficient to maintain secondary and tertiary VSG structure, prompted us to test the hypothesis that Th cells may preferentially recognize HV-1 subregion peptides. Thus, we examined the fine specificity of VSG-specific T-cell lines, T-cell hybridomas, and Th cells activated during infection. Our results demonstrate that T-cell epitopes are distributed throughout the N-terminal domain of VSG but are not clustered exclusively within HV-1 or other hypervariable subregions. In contrast, T-cell-reactive sites were not detected within the relatively conserved C-terminal domain of VSG. Overall, this study is the first to dissect the fine specificity of T-cell responses to the trypanosome VSG and suggests that evolution of a conserved HV-1 region may be unrelated to selective pressures exerted by host T-cell responses. This study also demonstrates that T cells do not recognize the relatively invariant C-terminal region of the VSG molecule during infection, suggesting that it could serve as a potential subunit vaccine to provide variant cross-specific immunity for African trypanosomiasis.
Identification of Meningococcal Genes Necessary for Colonization of Human Upper Airway Tissue
Authors: Exley Rachel M. , Sim Richard , Goodwin Linda , Winterbotham Megan , Schneider Muriel C. , Read Robert C. , Tang Christoph M. 
Published: October 2008

ABSTRACT

Neisseria meningitidis
is an exclusively human pathogen that has evolved primarily to colonize the nasopharynx rather than to cause systemic disease. Colonization is the most frequent outcome following meningococcal infection and a prerequisite for invasive disease. The mechanism of colonization involves attachment of the organism to epithelial cells via bacterial type IV pili (Tfp), but subsequent events during colonization remain largely unknown. We analyzed 576
N. meningitidis
mutants for their capacity to colonize human nasopharyngeal tissue in an organ culture model to identify bacterial genes required for colonization. Eight colonization-defective mutants were isolated. Two mutants were unable to express Tfp and were defective for adhesion to epithelial cells, which is likely to be the basis of their attenuation in nasopharyngeal tissue. Three other mutants are predicted to have lost previously uncharacterized surface molecules, while the remaining mutants have transposon insertions in genes of unknown function. We have identified novel meningococcal colonization factors, and this should provide insights into the survival of this important pathogen in its natural habitat.
Evidence of a Role for Monocytes in Dissemination and Brain Invasion byCryptococcus neoformans
Authors: Charlier Caroline , Nielsen Kirsten , Daou Samira , Brigitte Madly , Chretien Fabrice , Dromer Françoise 
Published: October 2008

ABSTRACTThe pathogenesis of cryptococcosis, including the events leading to the production of meningoencephalitis, is still largely unknown. Evidence of a transcellular passage ofCryptococcus neoformansacross the blood-brain barrier (BBB) and subsequent BBB disruption exists, but the paracellular passage of free yeasts and the role of monocytes in yeast dissemination and brain invasion (Trojan horse method) remain uncertain. We used our model of disseminated cryptococcosis, in which crossing of the BBB starts 6 h after intravenous inoculation, to study paracellular passage of the BBB. We prepared bone marrow-derived monocytes (BMDM) infected in vitro withC. neoformans(BMDM yeasts) and free yeasts and measured fungal loads in tissues. (i) Spleen and lung CFU were >2-fold higher in mice treated with BMDM yeasts than in those treated with free yeasts for 1 and 24 h (P< 0.05), while brain CFU were increased (3.9 times) only at 24 h (P< 0.05). (ii) By comparing the kinetics of brain invasion in naïve mice and in mice with preestablished cryptococcosis, we found that CFU were lower in the latter case, except at 6 h, when CFU from mice inoculated with BMDM yeasts were comparable to those measured in naïve mice and 2.5-fold higher than those in mice with preestablished cryptococcosis who were inoculated with free yeasts. (iii) Late phagocyte depletion obtained by clodronate injection reduced disease severity and lowered the fungal burden by 40% in all organs studied. These results provide evidence for Trojan horse crossing of the BBB byC. neoformans, together with mechanisms involving free yeasts, and overall for a role of phagocytes in fungal dissemination.
The Cytoplasmic Domain of Anthrax Toxin Receptor 1 Affects Binding of the Protective Antigen
Authors: Go Mandy Y. , Chow Edith M. C. , Mogridge Jeremy 
Published: October 2008

ABSTRACTThe protective antigen (PA) component of anthrax toxin binds the I domain of the receptor ANTXR1. Integrin I domains convert between open and closed conformations that bind ligand with high and low affinities, respectively; this process is regulated by signaling from the cytoplasmic domains. To assess whether intracellular signals might influence the interaction between ANTXR1 and PA, we compared two splice variants of ANTXR1 that differ only in their cytoplasmic domains. We found that cells expressing ANTXR1 splice variant 1 (ANTXR1-sv1) bound markedly less PA than did cells expressing a similar level of the shorter splice variant ANTXR1-sv2. ANTXR1-sv1 but not ANTXR1-sv2 associated with the actin cytoskeleton, although disruption of the cytoskeleton did not affect binding of ANTXR-sv1 to PA. Introduction of a cytoplasmic domain missense mutation found in the related receptor ANTXR2 in a patient with juvenile hyaline fibromatosis impaired actin association and increased binding of PA to ANTXR1-sv1. These results suggest that ANTXR1 has two affinity states that may be modulated by cytoplasmic signals.
EnterotoxigenicEscherichia coliModulates Host Intestinal Cell Membrane Asymmetry and Metabolic Activity
Authors: Johnson Amber M. , Kaushik Radhey S. , Rotella Nicholas J. , Hardwidge Philip R. 
Published: October 2008

ABSTRACTEnterotoxigenicEscherichia coli(ETEC) is a common cause of travelers' and postweaning diarrhea in humans and swine, respectively. The extent to which ETEC damages host cells is unclear. Experiments are presented that probe the ability of porcine ETEC isolates to induce apoptosis and cell death in porcine intestinal epithelial cells. Quantification of host phosphatidylserine exposure following ETEC infection suggested that ETEC induced changes in plasma membrane asymmetry, independent of the expression of the heat-labile enterotoxin. Significant host cell death was not observed. ETEC infection also caused a drastic inhibition of host esterase activity, as measured by calcein fluorescence. While ETEC infection resulted in activation of host caspase 3, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling of DNA double-strand breakage, indicative of late stages of apoptosis, was not observed. Camptothecin-induced apoptosis markedly increased subsequent ETEC adherence. Transfer of cell-free supernatants from apoptotic cells to bacterial inocula prior to infection of naïve cells increased the transcriptional activity of the regulatory region upstream of the K88ac operon and promoted subsequent adherence to host cells.
Urinary 1-hydroxypyrene and malondialdehyde in male workers in Chinese restaurants
Authors: Pan C-H , Chan C-C , Huang Y-L , Wu K-Y 
Published: October 2008

Objectives:To assess internal dose and oxidative stress in male restaurant workers exposed to polycyclic aromatic hydrocarbons (PAHs) from cooking oil fumes (COFs) in Chinese restaurants.Methods:The study participants included 288 male restaurant workers (171 kitchen and 117 service staff) in Chinese restaurants in Taiwan. Airborne particulate PAHs were measured over 12 h on each of two consecutive work days and then identified using high performance liquid chromatography. Urinary 1-hydroxypyrene (1-OHP) measurements were used to indicate COF exposure, and urinary malondialdehyde (MDA) was adopted as an oxidative stress marker. Multiple regression models were used to assess the relationship between MDA and 1-OHP levels after adjusting for key personal covariates.Results:Summed particulate PAH levels in kitchens (median 23.9 ng/m3) were significantly higher than those in dining areas (median 4.9 ng/m3). For non-smoking kitchen staff, mean MDA and 1-OHP levels were 344.2 (SD 243.7) and 6.0 (SD 8.0) μmol/mol creatinine, respectively. These levels were significantly higher than those for non-smoking service staff, which were 244.2 (SD 164.4) and 2.4 (SD 4.3) μmol/mol creatinine, respectively. Urinary 1-OHP levels were significantly associated with work in kitchens (p<0.05). Furthermore, urinary MDA levels were significantly associated with urinary 1-OHP levels (p<0.001) and working hours per day (p<0.05).Conclusions:These findings indicate that urinary 1-OHP and MDA levels reflect occupational exposure to PAHs from COFs and oxidative stress in workers in Chinese restaurants.
The risk of asthma mortality with inhaled long acting β-agonists
Authors: Wijesinghe M , Perrin K , Harwood M , Weatherall M , Beasley R 
Published: October 2008

Abstract
This article reviews the available evidence as to whether inhaled long acting β-agonists (LABA) increase the risk of asthma mortality and considers the implications for the use of this treatment in the management of asthma. Randomised controlled trials suggest that LABAs prescribed as monotherapy may increase the risk of asthma death in certain circumstances, such as the unsupervised “off-label” use without concomitant inhaled corticosteroid (ICS) treatment in patients with unstable asthma. However, there is also evidence that the use of LABAs in conjunction with ICS treatment in adult asthma as recommended in current guidelines is not associated with an increased risk of asthma mortality. The only way in which a prescriber can ensure that a patient with asthma takes LABA treatment in conjunction with ICS is through a combination ICS/LABA product, an approach which may have additional therapeutic advantages. We propose that in the management of asthma, a case can now be made to limit the availability of LABAs to combination LABA/ICS therapy.
Primary care research and clinical practice: gastroenterology
Authors: Jones R 
Published: October 2008

AbstractGastrointestinal problems account for a significant proportion of general practitioners' workload, and gastrointestinal cancers, taken together, make up the largest group of malignancies. Approximately 10% of consultations in general practice in the UK are for gastrointestinal symptoms or problems, split roughly equally between the upper and lower gastrointestinal tract. Gastroenterology represents about 10% of the work of hospital specialists and the prescribing costs involved in the management of gastrointestinal disorders in general practice are around 14% of the drug budget. These disorders range from relatively minor and self limiting conditions such as acute gastritis and acute gastroenteritis, through the more significant, chronic digestive disorders such as gastro-oesophageal reflux disease (GORD), irritable bowel syndrome (IBS) and coeliac disease, to much more serious problems including inflammatory bowel disease (IBD) and upper gastrointestinal and colorectal cancer.
Explaining the social gradient in smoking cessation: it’s not in the trying, but in the succeeding: Table 1
Authors: Kotz D , West R 
Published: October 2008

Objective:Smokers from more deprived socioeconomic groups are less likely to become ex-smokers. This study examined how far this is attributable in England to a social gradient in quit attempts, use of aids to cessation and/or the success of quit attempts.Design:Cross-sectional household survey.Setting:England.Participants:6950 respondents aged 16+ who had smoked in the past year, of whom 2983 had tried to stop in the past year and 469 reported having stopped at the time of the survey.Main outcome measures:Reported attempts to stop smoking in the past year; the use of stop-smoking medications (nicotine replacement therapy, bupropion or varenicline); use of behavioural support offered by the National Health Service Stop Smoking Services; current smoking status.Results:There was a large difference in success rates of quit attempts: 20.4% in social grade AB versus 11.4% in social grade E of those who made attempts were still not smoking by the time of the survey (p<0.001). However, there was no difference across social grades in the rate of attempts to stop (42.7% in social grade AB to 41.3% in E), use of medications to aid cessation (46.7% of those making quit attempts in AB to 50.9% in E) or use of NHS Stop Smoking Services (7.0% of those making quit attempts in AB to 4.8% in E).Conclusions:Smokers in more deprived socioeconomic groups are just as likely as those in higher groups to try to stop and use aids to cessation but there is a strong gradient across socioeconomic groups in success, with those in the lowest group being half as likely to succeed compared with the highest. Determining the cause of, and counteracting, this gradient is paramount in reducing health inequalities.