bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Induction of Bacterial Resistance to the Antimicrobial Peptide Tachyplesin I and Investigation of the Resistance Mechanisms
Authors: Hong Jun , Hu Jianye , Ke Fei 
Published: August 2016

ABSTRACT

Tachyplesin I is a 17-amino-acid cationic antimicrobial peptide (AMP) with a typical cyclic antiparallel β-sheet structure that is a promising therapeutic for infections, tumors, and viruses. To date, no bacterial resistance to tachyplesin I has been reported. To explore the safety of tachyplesin I as an antibacterial drug for wide clinical application, we experimentally induced bacterial resistance to tachyplesin I by using two selection procedures and studied the preliminary resistance mechanisms.
Aeromonas hydrophila
XS91-4-1,
Pseudomonas aeruginosa
CGMCC1.2620, and
Escherichia coli
ATCC 25922 and F41 showed resistance to tachyplesin I under long-term selection pressure with continuously increasing concentrations of tachyplesin I. In addition,
P. aeruginosa
and
E. coli
exhibited resistance to tachyplesin I under UV mutagenesis selection conditions. Cell growth and colony morphology were slightly different between control strains and strains with induced resistance. Cross-resistance to tachyplesin I and antimicrobial agents (cefoperazone and amikacin) or other AMPs (pexiganan, tachyplesin III, and polyphemusin I) was observed in some resistant mutants. Previous studies showed that extracellular protease-mediated degradation of AMPs induced bacterial resistance to AMPs. Our results indicated that the resistance mechanism of
P. aeruginosa
was not entirely dependent on extracellular proteolytic degradation of tachyplesin I; however, tachyplesin I could induce increased proteolytic activity in
P. aeruginosa
. Most importantly, our findings raise serious concerns about the long-term risks associated with the development and clinical use of tachyplesin I.
The
RTA3
Gene, Encoding a Putative Lipid Translocase, Influences the Susceptibility of Candida albicans to Fluconazole
Authors: Whaley Sarah G. , Tsao Sarah , Weber Sandra , Zhang Qing , Barker Katherine S. , Raymond Martine , Rogers P. David 
Published: August 2016

ABSTRACT

The
RTA3
gene, coding for a member of the Rta1p-like lipid-translocating exporter family, is coordinately upregulated with the ATP-binding cassette transporter genes
CDR1
and
CDR2
in azole-resistant clinical isolates of
Candida albicans
that carry activating mutations in the transcription factor Tac1p. We show here that deleting
RTA3
in an azole-resistant clinical isolate carrying a Tac1p-activating mutation lowered fluconazole resistance by 2-fold, while overexpressing
RTA3
in an azole-susceptible clinical isolate resulted in enhanced fluconazole tolerance associated with trailing growth in a liquid microtiter plate assay. We also demonstrate that an Rta3p-green fluorescent protein (GFP) fusion protein localizes predominantly to the plasma membrane, consistent with a putative function for Rta3p as a lipid translocase.
Rare Spontaneous Loss of Multiresistance Gene Carrying IncI/ST12 Plasmid in Escherichia coli in Pig Microbiota
Authors: Mourand Gwenaelle , Touzain Fabrice , Jouy Eric , Fleury Mickael Alain , Denamur Erick , Kempf Isabelle 
Published: August 2016

ABSTRACT

Resistance to extended-spectrum cephalosporins (ESCs) is a matter of considerable concern for public health. Here, we studied the spontaneous loss of an extended-spectrum beta-lactamase (ESBL)-encoding plasmid from a rifampin-resistant
Escherichia coli
isolate orally inoculated into pigs under controlled conditions. Fecal samples were collected and cultured on rifampin-supplemented medium, and the resistance of the
E. coli
isolates to ESCs was studied by phenotypic tests, PCR detection of plasmid genes, and complete sequencing. The results showed that only 3 out of 353 rifampin-resistant
E. coli
isolates were ESC susceptible, and PCR and bioinformatics analysis confirmed the loss of the plasmid. These
in vivo
experiments indicate that the loss of an ESBL-encoding plasmid seems a rare event in gut microbiota.
In Vitro
Evaluation of the Activity of Imipenem-Relebactam against 451 Recent Clinical Isolates of Bacteroides Group and Related Species
Authors: Snydman David R. , Jacobus Nilda V. , McDermott Laura A. 
Published: August 2016

ABSTRACT

We evaluated the
in vitro
activity of imipenem-relebactam (imipenem-MK7655) against 451 recent clinical isolates within the
Bacteroides
group and related species. Relebactam did not enhance or inhibit the activity of imipenem against
Bacteroides fragilis
or other
Bacteroides
species. No synergistic or antagonistic effect was observed. The MICs of imipenem-relebactam were equal to or within one dilution of the MICs of these isolates to imipenem.
High Prevalence of Hypervirulent Klebsiella pneumoniae Infection in China: Geographic Distribution, Clinical Characteristics, and Antimicrobial Resistance
Authors: Zhang Yawei , Zhao Chunjiang , Wang Qi , Wang Xiaojuan , Chen Hongbin , Li Henan , Zhang Feifei , Li Shuguang , Wang Ruobing , Wang Hui 
Published: August 2016

ABSTRACT

Hypervirulent
Klebsiella pneumoniae
(hvKP) is traditionally defined by hypermucoviscosity, but data based on genetic background are limited. Antimicrobial-resistant hvKP has been increasingly reported but has not yet been systematically studied.
K. pneumoniae
isolates from bloodstream infections, hospital-acquired pneumonia, and intra-abdominal infections were collected from 10 cities in China during February to July 2013. Clinical data were collected from medical records. All
K. pneumoniae
isolates were investigated by antimicrobial susceptibility testing, string test, extended-spectrum β-lactamase (ESBL) gene detection, capsular serotypes, virulence gene profiles, and multilocus sequence typing. hvKP was defined by aerobactin detection. Of 230
K. pneumoniae
isolates, 37.8% were hvKP. The prevalence of hvKP varied among different cities, with the highest rate in Wuhan (73.9%) and the lowest in Zhejiang (8.3%). Hypermucoviscosity and the presence of K1, K2, K20, and
rmpA
genes were strongly associated with hvKP (
P
< 0.001). A significantly higher incidence of liver abscess (
P
= 0.026), sepsis (
P
= 0.038), and invasive infections (
P
= 0.043) was caused by hvKP. Cancer (odds ratio [OR], 2.285) and diabetes mellitus (OR, 2.256) appeared to be independent variables associated with hvKP infections by multivariate analysis. Importantly, 12.6% of hvKP isolates produced ESBLs, and most of them carried
bla
CTX-M
genes. Patients with neutropenia (37.5% versus 5.6%;
P
= 0.020), history of systemic steroid therapy (37.5% versus 5.6%;
P
= 0.020), and combination therapy (62.5% versus 16.7%;
P
= 0.009) were more likely to be infected with ESBL-producing hvKP. The prevalence of hvKP is high in China and has a varied geographic distribution. ESBL-producing hvKP is emerging, suggesting an urgent need to enhance clinical awareness, especially for immunocompromised patients receiving combination therapy.
Glutamate Racemase Is the Primary Target of β-Chloro-
d
-Alanine in Mycobacterium tuberculosis
Authors: Prosser Gareth A. , Rodenburg Anne , Khoury Hania , de Chiara Cesira , Howell Steve , Snijders Ambrosius P. , de Carvalho Luiz Pedro S. 
Published: August 2016

ABSTRACT

The increasing global prevalence of drug resistance among many leading human pathogens necessitates both the development of antibiotics with novel mechanisms of action and a better understanding of the physiological activities of preexisting clinically effective drugs. Inhibition of peptidoglycan (PG) biosynthesis and cross-linking has traditionally enjoyed immense success as an antibiotic target in multiple bacterial pathogens, except in
Mycobacterium tuberculosis
, where it has so far been underexploited.
d
-Cycloserine, a clinically approved antituberculosis therapeutic, inhibits enzymes within the
d
-alanine subbranch of the PG-biosynthetic pathway and has been a focus in our laboratory for understanding peptidoglycan biosynthesis inhibition and for drug development in studies of
M. tuberculosis
. During our studies on alternative inhibitors of the
d
-alanine pathway, we discovered that the canonical alanine racemase (Alr) inhibitor β-chloro–
d
-alanine (BCDA) is a very poor inhibitor of recombinant
M. tuberculosis
Alr, despite having potent antituberculosis activity. Through a combination of enzymology, microbiology, metabolomics, and proteomics, we show here that BCDA does not inhibit the
d
-alanine pathway in intact cells, consistent with its poor
in vitro
activity, and that it is instead a mechanism-based inactivator of glutamate racemase (MurI), an upstream enzyme in the same early stage of PG biosynthesis. This is the first report to our knowledge of inhibition of MurI in
M. tuberculosis
and thus provides a valuable tool for studying this essential and enigmatic enzyme and a starting point for future MurI-targeted antibacterial development.
MgtC as a Host-Induced Factor and Vaccine Candidate against Mycobacterium abscessus Infection
Authors: Le Moigne Vincent , Belon Claudine , Goulard Céline , Accard Geoffrey , Bernut Audrey , Pitard Bruno , Gaillard Jean-Louis , Kremer Laurent , Herrmann Jean-Louis , Blanc-Potard Anne-Béatrice 
Published: August 2016

ABSTRACT

Mycobacterium abscessus
is an emerging pathogenic mycobacterium involved in pulmonary and mucocutaneous infections, presenting a serious threat for patients with cystic fibrosis (CF). The lack of an efficient treatment regimen and the emergence of multidrug resistance in clinical isolates require the development of new therapeutic strategies against this pathogen. Reverse genetics has revealed genes that are present in
M. abscessus
but absent from saprophytic mycobacteria and that are potentially involved in pathogenicity. Among them,
MAB_3593
encodes MgtC, a known virulence factor involved in intramacrophage survival and adaptation to Mg
2+
deprivation in several major bacterial pathogens. Here, we demonstrated a strong induction of
M. abscessus
MgtC at both the transcriptional and translational levels when bacteria reside inside macrophages or upon Mg
2+
deprivation. Moreover, we showed that
M. abscessus
MgtC was recognized by sera from
M. abscessus
-infected CF patients. The intramacrophage growth (J774 or THP1 cells) of a
M. abscessus
knockout
mgtC
mutant was, however, not significantly impeded. Importantly, our results indicated that inhibition of MgtC
in vivo
through immunization with
M. abscessus
mgtC
DNA, formulated with a tetrafunctional amphiphilic block copolymer, exerted a protective effect against an aerosolized
M. abscessus
challenge in CF (ΔF508 FVB) mice. The formulated DNA immunization was likely associated with the production of specific MgtC antibodies, which may stimulate a protective effect by counteracting MgtC activity during
M. abscessus
infection. These results emphasize the importance of
M. abscessus
MgtC
in vivo
and provide a basis for the development of novel therapeutic tools against pulmonary
M. abscessus
infections in CF patients.
Use of a Multiplex Transcript Method for Analysis of Pseudomonas aeruginosa Gene Expression Profiles in the Cystic Fibrosis Lung
Authors: Gifford Alex H. , Willger Sven D. , Dolben Emily L. , Moulton Lisa A. , Dorman Dana B. , Bean Heather , Hill Jane E. , Hampton Thomas H. , Ashare Alix , Hogan Deborah A. 
Published: August 2016

ABSTRACTThe discovery of therapies that modulatePseudomonas aeruginosavirulence or that can eradicate chronicP. aeruginosalung infections associated with cystic fibrosis (CF) will be advanced by an improved understanding ofP. aeruginosabehaviorin vivo. We demonstrate the use of multiplexed Nanostring technology to monitor relative abundances ofP. aeruginosatranscripts across clinical isolates, in serial samples, and for the purposes of comparing microbial physiologyin vitroandin vivo. The expression of 75 transcripts encoded by genes implicated in CF lung disease was measured in a variety ofP. aeruginosastrains as well as RNA serial sputum samples from fourP. aeruginosa-colonized subjects with CF collected over 6 months. We present data on reproducibility, the results from different methods of normalization, and demonstrate high concordance between transcript relative abundance data obtained by Nanostring or transcriptome sequencing (RNA-Seq) analysis. Furthermore, we address considerations regarding sequence variation between strains during probe design. Analysis ofP. aeruginosagrownin vitroidentified transcripts that correlated with the different phenotypes commonly observed in CF clinical isolates.P. aeruginosatranscript profiles in RNA from CF sputum indicated alginate productionin vivo, and transcripts involved in quorum-sensing regulation were less abundant in sputum than strains grown in the laboratory.P. aeruginosagene expression patterns from sputum clustered closely together relative to patterns for laboratory-grown cultures; in contrast, laboratory-grownP. aeruginosashowed much greater transcriptional variation with only loose clustering of strains with different phenotypes. The clustering within and between subjects was surprising in light of differences in inhaled antibiotic and respiratory symptoms, suggesting that the pathways represented by these 75 transcripts are stable in chronic CFP. aeruginosalung infections.
Attachment of Actinobacillus suis H91-0380 and Its Isogenic Adhesin Mutants to Extracellular Matrix Components of the Tonsils of the Soft Palate of Swine
Authors: Bujold Adina R. , MacInnes Janet I. 
Published: August 2016

ABSTRACT

Tonsils conduct immune surveillance of antigens entering the upper respiratory tract. Despite their immunological function, they are also sites of persistence and invasion of bacterial pathogens.
Actinobacillus suis
is a common resident of the tonsils of the soft palate in pigs, but under certain circumstances it can invade, causing septicemia and related sequelae. Twenty-four putative adhesins are predicted in the
A. suis
genome, but to date, little is known about how they might participate in colonization or invasion. To better understand these processes, swine tonsil lysates were characterized by mass spectrometry. Fifty-nine extracellular matrix (ECM) proteins were identified, including small leucine-rich proteoglycans, integrins, and other cell surface receptors. Additionally, attachment of the wild type and 3 adhesin mutants to 5 ECM components was evaluated. Exponential cultures of wild-type
A. suis
adhered significantly more than stationary cultures to all ECM components studied except collagen I. During exponential growth, the
A. suis
Δ
flp1
mutant attached less to collagen IV while the Δ
ompA
mutant attached less to all ECMs. The Δ
comE1
strain attached less to collagen IV, fibronectin, and vitronectin during exponential growth and exhibited differential attachment to collagen I over short adherence time points. These results suggest that Flp1, OmpA, and ComE1 are important during early stages of attachment to ECM components found in tonsils, which supports the notion that other adhesins have compensatory effects during later stages of attachment.
Resistance of Mice of the 129 Background to Yersinia pestis Maps to Multiple Loci on Chromosome 1
Authors: Tencati Michael , Tapping Richard I. 
Published: August 2016

ABSTRACTYersinia pestisis a Gram-negative bacterium that is the causative agent of bubonic and pneumonic plague. It is commonly acquired by mammals such as rodents and humans via the bite of an infected flea. We previously reported that multiple substrains of the 129 mouse background are resistant to pigmentation locus-negative (pgm−)Yersinia pestisand that this phenotype maps to a 30-centimorgan (cM) region located on chromosome 1. In this study, we have further delineated this plague resistance locus to a region of less than 20 cM through the creation and phenotyping of recombinant offspring arising from novel crossovers in this region. Furthermore, our experiments have revealed that there are at least two alleles in this initial locus, both of which are required for resistance on a susceptible C57BL/6 background. These two alleles work intranssince resistance is restored in offspring possessing one allele contributed by each parent. Our studies also indicated that the Slc11a1 gene (formerly known as Nramp1) located within the chromosome1 locus is not responsible for conferring resistance to 129 mice.
Leishmania donovani-Induced Prostaglandin E2 Generation Is Critically Dependent on Host Toll-Like Receptor 2–Cytosolic Phospholipase A2 Signaling
Authors: Bhattacharjee Amrita , Majumder Saikat , Das Shibali , Ghosh Sweta , Biswas Satabdi , Majumdar Subrata 
Published: August 2016

ABSTRACT

Visceral leishmaniasis (VL) is the second-largest parasitic killer disease after malaria. During VL, the protozoan
Leishmania donovani
induces prostaglandin E2 (PGE2) generation within host macrophages to aid parasite survival. PGE2 significantly influences leishmanial pathogenesis, as
L. donovani
proliferation is known to be attenuated in PGE2-inhibited macrophages. Here, we report for the first time that signaling via macrophage Toll-like receptor 2 (TLR2) plays an instrumental role in inducing PGE2 release from
L. donovani
-infected macrophages. This signaling cascade, mediated via the TLR2–phosphatidylinositol 3-kinase (PI3K)–phospholipase C (PLC) signaling pathway, was found to be indispensable for activation of two major enzymes required for PGE2 generation: cytosolic phospholipase A2 (cPLA2) and cyclooxygenase 2 (Cox2). Inhibition of cPLA2, but not secreted phospholipase A2 (sPLA2) or calcium-independent phospholipase A2 (iPLA2), arrested
L. donovani
infection. During infection, cPLA2 activity increased >7-fold in a calcium-dependent and extracellular signal-regulated kinase (ERK)-dependent manner, indicating that elevation of intracellular calcium and ERK-mediated phosphorylation was necessary for
L. donovani
-induced cPLA2 activation. For transcriptional upregulation of cyclooxygenase 2, activation of the calcium-calcineurin-nuclear factor of activated T cells (NFAT) signaling was required in addition to the TLR2-PI3K-PLC pathway. Detailed studies by site-directed mutagenesis of potential NFAT binding sites and chromatin immunoprecipitation (ChIP) analysis revealed that the binding of macrophage NFATc2, at the −73/−77 site on the
cox2
promoter, induced
L. donovani
-driven
cox2
transcriptional activation. Collectively, these findings highlight the contribution of TLR2 downstream signaling toward activation of cPLA2 and Cox2 and illustrate how the TLR2-PI3K-PLC pathway acts in a concerted manner with calcium-calcineurin-NFATc2 signaling to modulate PGE2 release from
L. donovani
-infected macrophages.
Neonatal Fc Receptor Regulation of Lung Immunoglobulin and CD103
+
Dendritic Cells Confers Transient Susceptibility to Tuberculosis
Authors: Vogelzang Alexis , Lozza Laura , Reece Stephen T. , Perdomo Carolina , Zedler Ulrike , Hahnke Karin , Oberbeck-Mueller Dagmar , Dorhoi Anca , Kaufmann Stefan H. E. 
Published: August 2016

ABSTRACT

The neonatal Fc receptor (FcRn) extends the systemic half-life of IgG antibodies by chaperoning bound Fc away from lysosomal degradation inside stromal and hematopoietic cells. FcRn also transports IgG across mucosal barriers into the lumen, and yet little is known about how FcRn modulates immunity in the lung during homeostasis or infection. We infected wild-type (WT) and FcRn-deficient (
fcgrt
−/−
) mice with
Pseudomonas aeruginosa
or
Mycobacterium tuberculosis
to investigate whether recycling and transport of IgG via FcRn influences innate and adaptive immunity in the lung in response to bacterial infection. We found that FcRn expression maintains homeostatic IgG levels in lung and leads to preferential secretion of low-affinity IgG ligands into the lumen.
Fcgrt
−/−
animals exhibited no evidence of developmental impairment of innate immunity in the lung and were able to efficiently recruit neutrophils in a model of acute bacterial pneumonia. Although local humoral immunity in lung increased independently of the presence of FcRn during tuberculosis, there was nonetheless a strong impact of FcRn deficiency on local adaptive immunity. We show that the quantity and quality of IgG in airways, as well as the abundance of dendritic cells in the lung, are maintained by FcRn. FcRn ablation transiently enhanced local T cell immunity and neutrophil recruitment during tuberculosis, leading to a lower bacterial burden in lung. This novel understanding of tissue-specific modulation of mucosal IgG isotypes in the lung by FcRn sheds light on the role of mucosal IgG in immune responses in the lung during homeostasis and bacterial disease.
The Aryl Hydrocarbon Receptor Modulates Production of Cytokines and Reactive Oxygen Species and Development of Myocarditis during Trypanosoma cruzi Infection
Authors: Barroso Andréia , Gualdrón-López Melisa , Esper Lísia , Brant Fátima , Araújo Ronan R. S. , Carneiro Matheus B. H. , Ávila Thiago V. , Souza Danielle G. , Vieira Leda Q. , Rachid Milene A. , Tanowitz Herbert B. , Teixeira Mauro M. , Machado Fabiana S. 
Published: August 2016

ABSTRACT

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor involved in controlling several aspects of immune responses, including the activation and differentiation of specific T cell subsets and antigen-presenting cells, thought to be relevant in the context of experimental
Trypanosoma cruzi
infection. The relevance of AhR for the outcome of
T. cruzi
infection is not known and was investigated here. We infected wild-type (WT) mice and AhR knockout (AhR KO) mice with
T. cruzi
(Y strain) and determined levels of parasitemia, myocardial inflammation and fibrosis, expression of AhR/cytokines/suppressor of cytokine signaling (SOCS) (spleen/heart), and production of nitric oxide (NO), reactive oxygen species (ROS), and peroxynitrite (ONOO
−
) (spleen). AhR expression was increased in the heart of infected WT mice. Infected AhR KO mice displayed significantly reduced parasitemia, inflammation, and fibrosis of the myocardium. This was associated with an anticipated increased immune response characterized by increased levels of inflammatory cytokines and reduced expression of SOCS2 and SOCS3 in the heart.
In vitro
, AhR deficiency caused impairment in parasite replication and decreased levels of ROS production. In conclusion, AhR influences the development of murine Chagas disease by modulating ROS production and regulating the expression of key physiological regulators of inflammation, SOCS1 to -3, associated with the production of cytokines during experimental
T. cruzi
infection.