bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prospective Multicenter Study of Carbapenemase-Producing Enterobacteriaceae from 83 Hospitals in Spain Reveals High
In Vitro
Susceptibility to Colistin and Meropenem
Authors: Oteo Jesús , Ortega Adriana , Bartolomé Rosa , Bou Germán , Conejo Carmen , Fernández-Martínez Marta , González-López Juan José , Martínez-García Laura , Martínez-Martínez Luis , Merino María , Miró Elisenda , Mora Marta , Navarro Ferran , Oliver Antonio , Pascual Álvaro , Rodríguez-Baño Jesús , Ruiz-Carrascoso Guillermo , Ruiz-Garbajosa Patricia , Zamorano Laura , Bautista Verónica , Pérez-Vázquez María , Campos José 
Published: April 2015

ABSTRACT

The aim of this study was to determine the impact of carbapenemase-producing
Enterobacteriaceae
(CPE) in Spain in 2013 by describing the prevalence, dissemination, and geographic distribution of CPE clones, and their population structure and antibiotic susceptibility. From February 2013 to May 2013, 83 hospitals (about 40,000 hospital beds) prospectively collected nonduplicate
Enterobacteriaceae
using the screening cutoff recommended by EUCAST. Carbapenemase characterization was performed by phenotypic methods and confirmed by PCR and sequencing. Multilocus sequencing types (MLST) were determined for
Klebsiella pneumoniae
and
Escherichia coli
. A total of 702
Enterobacteriaceae
isolates met the inclusion criteria; 379 (54%) were CPE. OXA-48 (71.5%) and VIM-1 (25.3%) were the most frequent carbapenemases, and
K. pneumoniae
(74.4%),
Enterobacter cloacae
(10.3%), and
E. coli
(8.4%) were the species most affected. Susceptibility to colistin, amikacin, and meropenem was 95.5%, 81.3%, and 74.7%, respectively. The most prevalent sequence types (STs) were ST11 and ST405 for
K. pneumoniae
and ST131 for
E. coli
. Forty-five (54.1%) of the hospitals had at least one CPE case. For
K. pneumoniae
, ST11/OXA-48, ST15/OXA-48, ST405/OXA-48, and ST11/VIM-1 were detected in two or more Spanish provinces. ST11 isolates carried four carbapenemases (VIM-1, OXA-48, KPC-2, and OXA-245), but ST405 isolates carried OXA-48 only. A wide interregional spread of CPE in Spain was observed, mainly due to a few successful clones of OXA-48-producing
K. pneumoniae
(e.g., ST11 and ST405). The dissemination of OXA-48-producing
E. coli
is a new finding of public health concern. According to the susceptibilities determined
in vitro
, most of the CPE (94.5%) had three or more options for antibiotic treatment.
Polymorphic Variation in Susceptibility and Metabolism of Triclosan-Resistant Mutants of Escherichia coli and Klebsiella pneumoniae Clinical Strains Obtained after Exposure to Biocides and Antibiotics
Authors: Curiao Tânia , Marchi Emmanuela , Viti Carlo , Oggioni Marco R. , Baquero Fernando , Martinez José Luis , Coque Teresa M. 
Published: April 2015

ABSTRACT

Exposure to biocides may result in cross-resistance to other antimicrobials. Changes in biocide and antibiotic susceptibilities, metabolism, and fitness costs were studied here in biocide-selected
Escherichia coli
and
Klebsiella pneumoniae
mutants.
E. coli
and
K. pneumoniae
mutants with various degrees of triclosan susceptibility were obtained after exposure to triclosan (TRI), benzalkonium chloride (BKC), chlorhexidine (CHX) or sodium hypochlorite (SHC), and ampicillin or ciprofloxacin. Alterations in antimicrobial susceptibility and metabolism in mutants were tested using Phenotype MicroArrays. The expression of AcrAB pump and global regulators (SoxR, MarA, and RamA) was measured by quantitative reverse transcription-PCR (qRT-PCR), and the central part of the
fabI
gene was sequenced. The fitness costs of resistance were assessed by a comparison of relative growth rates. Triclosan-resistant (TRI
r
) and triclosan-hypersusceptible (TRI
hs
) mutants of
E. coli
and
K. pneumoniae
were obtained after selection with biocides and/or antibiotics.
E. coli
TRI
r
mutants, including those with mutations in the
fabI
gene or in the expression of
acrB
,
acrF
, and
marA
, exhibited changes in susceptibility to TRI, CHX, and antibiotics. TRI
r
mutants for which the TRI MIC was high presented improved metabolism of carboxylic acids, amino acids, and carbohydrates. In TRI
r
mutants, resistance to one antimicrobial provoked hypersusceptibility to another one(s). TRI
r
mutants had fitness costs, particularly
marA
-overexpressing (
E. coli
) or
ramA
-overexpressing (
K. pneumoniae
) mutants. TRI, BKC, and CIP exposure frequently yielded TRI
r
mutants exhibiting alterations in AraC-like global regulators (MarA, SoxR, and RamA), AcrAB-TolC, and/or FabI, and influencing antimicrobial susceptibility, fitness, and metabolism. These various phenotypes suggest a trade-off of different selective processes shaping the evolution toward antibiotic/biocide resistance and influencing other adaptive traits.
Small-Plasmid-Mediated Antibiotic Resistance Is Enhanced by Increases in Plasmid Copy Number and Bacterial Fitness
Authors: San Millan Alvaro , Santos-Lopez Alfonso , Ortega-Huedo Rafael , Bernabe-Balas Cristina , Kennedy Sean P. , Gonzalez-Zorn Bruno 
Published: April 2015

ABSTRACT

Plasmids play a key role in the horizontal spread of antibiotic resistance determinants among bacterial pathogens. When an antibiotic resistance plasmid arrives in a new bacterial host, it produces a fitness cost, causing a competitive disadvantage for the plasmid-bearing bacterium in the absence of antibiotics. On the other hand, in the presence of antibiotics, the plasmid promotes the survival of the clone. The adaptations experienced by plasmid and bacterium in the presence of antibiotics during the first generations of coexistence will be crucial for the progress of the infection and the maintenance of plasmid-mediated resistance once the treatment is over. Here we developed a model system using the human pathogen
Haemophilus influenzae
carrying the small plasmid pB1000 conferring resistance to β-lactam antibiotics to investigate host and plasmid adaptations in the course of a simulated ampicillin therapy. Our results proved that plasmid-bearing clones compensated for the fitness disadvantage during the first 100 generations of plasmid-host adaptation. In addition, ampicillin treatment was associated with an increase in pB1000 copy number. The augmentation in both bacterial fitness and plasmid copy number gave rise to
H. influenzae
populations with higher ampicillin resistance levels. In conclusion, we show here that the modulations in bacterial fitness and plasmid copy number help a plasmid-bearing bacterium to adapt during antibiotic therapy, promoting both the survival of the host and the spread of the plasmid.
Identification of Multiresistance Gene
cfr
in Methicillin-Resistant Staphylococcus aureus from Pigs: Plasmid Location and Integration into a Staphylococcal Cassette Chromosome
mec
Complex
Authors: Li Dexi , Wu Congming , Wang Yang , Fan Run , Schwarz Stefan , Zhang Suxia 
Published: April 2015

ABSTRACT

The multiresistance gene
cfr
was found in 8/231 porcine methicillin-resistant
Staphylococcus aureus
isolates. They were characterized by multilocus sequence typing,
spa
typing,
dru
typing, and staphylococcal cassette chromosome
mec
(SCC
mec
) typing as ST627-t002-dt12w-IVb, ST6-t304-dt12w-IVb, ST9-t899-dt12w-IVb, ST9-t899-dt12ae-IVb, or ST63-t899-dt12v-IVb. Different
cfr
gene regions were detected on plasmids of ca. 35 kb in seven isolates. For the first time, an IS
Enfa4-cfr
-IS
256
fragment was found to be inserted upstream of the
ccr
genes in a chromosomal SCC
mec
IVb element of the remaining isolate.
PBP1a/LpoA but Not PBP1b/LpoB Are Involved in Regulation of the Major β-Lactamase GeneblaAin Shewanella oneidensis
Authors: Yin Jianhua , Sun Yiyang , Mao Yinting , Jin Miao , Gao Haichun 
Published: April 2015

ABSTRACTβ-Lactamase production is one of the most important strategies for Gram-negative bacteria to combat β-lactam antibiotics. Studies of the regulation of β-lactamase expression have largely been focused on the class C β-lactamase AmpC, whose induction by β-lactams requires LysR-type regulator AmpR and permease AmpG-dependent peptidoglycan recycling intermediates. InShewanella, which is ubiquitous in aquatic environments and is a reservoir for antibiotic resistance, production of the class D β-lactamase BlaA confers bacteria with natural resistance to many β-lactams. Expression of theblaAgene in the genus representativeShewanella oneidensisis distinct from the AmpC paradigm because of the lack of an AmpR homologue and the presence of an additional AmpG-independent regulatory pathway. In this study, using transposon mutagenesis, we identify proteins that are involved inblaAregulation. Inactivation ofmrcAandlpoA, which encode penicillin binding protein 1a (PBP1a) and its lipoprotein cofactor, LpoA, respectively, drastically enhancesblaAexpression in the absence of β-lactams. Although PBP1b and its cognate, LpoB, also exist inS. oneidensis, their roles inblaAinduction are dispensable. We further show that themrcA-mediatedblaAexpression is independent of AmpG.
Activity of Clarithromycin or Rifampin Alone or in Combination against Experimental Rhodococcus equi Infection in Mice
Authors: Burton Alexandra J. , Giguère Steeve , Berghaus Londa J. , Hondalus Mary K. 
Published: April 2015

ABSTRACT

Treatment of mice with the combination of clarithromycin with rifampin resulted in a significantly lower number of
Rhodococcus equi
CFU in the organs of mice than treatment with either drug alone or placebo. There was no significant difference in the number of
R. equi
CFU between mice treated with clarithromycin monotherapy, rifampin monotherapy, or placebo. The combination of clarithromycin with rifampin conferred a clear advantage over either drug as monotherapy in this model of chronic
R. equi
infection.
In VitroAntibacterial Activity of AZD0914 against Human Mycoplasmas and Ureaplasmas
Authors: Waites Ken B. , Crabb Donna M. , Duffy Lynn B. , Huband Michael D. 
Published: April 2015

ABSTRACTIn this study, susceptibilities were determined for AZD0914, a spiropyrimidinetrione DNA gyrase inhibitor, azithromycin, doxycycline, and levofloxacin againstMycoplasmaandUreaplasmaspecies. The activity of AZD0914 was comparable to that of levofloxacin and doxycycline againstMycoplasma genitaliumandMycoplasma pneumoniae. The AZD0914 MIC90againstMycoplasma hominiswas 8-fold greater than that for levofloxacin. The AZD0914 MIC90againstUreaplasmaspecies was 4-fold less than that for azithromycin and 8-fold less than that for levofloxacin and doxycycline.
The CpAL Quorum Sensing System Regulates Production of Hemolysins CPA and PFO To Build Clostridium perfringens Biofilms
Authors: Vidal Jorge E. , Shak Joshua R. , Canizalez-Roman Adrian 
Published: April 2015

ABSTRACTClostridium perfringensstrains produce severe diseases, including myonecrosis and enteritis necroticans, in humans and animals. Diseases are mediated by the production of potent toxins that often damage the site of infection, e.g., skin epithelium during myonecrosis. In planktonic cultures, the regulation of important toxins, such as CPA, CPB, and PFO, is controlled by theC. perfringensAgr-like (CpAL) quorum sensing (QS) system. Strains also encode a functional LuxS/AI-2 system. AlthoughC. perfringensstrains form biofilm-like structures, the regulation of biofilm formation is poorly understood. Therefore, our studies investigated the role of CpAL and LuxS/AI-2 QS systems and of QS-regulated factors in controlling the formation of biofilms. We first demonstrate that biofilm production by reference strains differs depending on the culture medium. Increased biomass correlated with the presence of extracellular DNA in the supernatant, which was released by lysis of a fraction of the biofilm population and planktonic cells. Whereas ΔagrBmutant strains were not able to produce biofilms, a ΔluxSmutant produced wild-type levels. The transcript levels of CpAL-regulatedcpaandpfoAgenes, but notcpb, were upregulated in biofilms compared to planktonic cultures. Accordingly, Δcpaand ΔpfoAmutants, in type A (S13) or type C (CN3685) backgrounds, were unable to produce biofilms, whereas CN3685Δcpbmade wild-type levels. Biofilm formation was restored in complemented Δcpa/cpaand ΔpfoA/pfoAstrains. Confocal microscopy studies further detected CPA partially colocalizing with eDNA on the biofilm structure. Thus, CpAL regulates biofilm formation inC. perfringensby increasing levels of certain toxins required to build biofilms.
The Human P-Glycoprotein Transporter Enhances the Type I Interferon Response to Listeria monocytogenes Infection
Authors: Sigal Nadejda , Kaplan Zeevi Millie , Weinstein Shiri , Peer Dan , Herskovits Anat A. 
Published: April 2015

ABSTRACT

Human multidrug efflux transporters are known for their ability to extrude antibiotics and toxic compounds out of cells, yet accumulating data indicate they have additional functions in diverse physiological processes not related to drug efflux. Here, we show that the human multidrug transporter P-glycoprotein (P-gp) (also named MDR1 and ABCB1) is transcriptionally induced in the monocytic cell line THP-1 upon infection with the human intracellular bacterial pathogen
Listeria monocytogenes
. Notably, we found that P-gp is important for full activation of the type I interferon response elicited against
L. monocytogenes
bacteria. Both inhibition of P-gp function by verapamil and inhibition of its transcription using mRNA silencing led to a reduction in the magnitude of the type I response in infected cells. This function of P-gp was specific to type I interferon cytokines elicited against cytosolic replicating bacteria and was not observed in response to cyclic di-AMP (c-di-AMP), a molecule that was shown to be secreted by
L. monocytogenes
during infection and to trigger type I interferons. Moreover, P-gp was not involved in activation of other proinflammatory cytokines, such as those triggered by vacuolar-restricted
L. monocytogenes
or lipopolysaccharide (LPS). Taken together, these findings demonstrate a role for P-gp in proper development of an innate immune response against intracellular pathogens, highlighting the complexity in employing therapeutic strategies that involve inhibition of multidrug resistance (MDR) efflux pumps.
The Cpx System Regulates Virulence Gene Expression in Vibrio cholerae
Authors: Acosta Nicole , Pukatzki Stefan , Raivio Tracy L. 
Published: April 2015

ABSTRACT

Bacteria possess signal transduction pathways capable of sensing and responding to a wide variety of signals. The Cpx envelope stress response, composed of the sensor histidine kinase CpxA and the response regulator CpxR, senses and mediates adaptation to insults to the bacterial envelope. The Cpx response has been implicated in the regulation of a number of envelope-localized virulence determinants across bacterial species. Here, we show that activation of the Cpx pathway in
Vibrio cholerae
El Tor strain C6706 leads to a decrease in expression of the major virulence factors in this organism, cholera toxin (CT) and the toxin-coregulated pilus (TCP). Our results indicate that this occurs through the repression of production of the ToxT regulator and an additional upstream transcription factor, TcpP. The effect of the Cpx response on CT and TCP expression is mostly abrogated in a cyclic AMP receptor protein (CRP) mutant, although expression of the
crp
gene is unaltered. Since TcpP production is controlled by CRP, our data suggest a model whereby the Cpx response affects CRP function, which leads to diminished TcpP, ToxT, CT, and TCP production.
Characterization of Clostridium perfringens TpeL Toxin Gene Carriage, Production, Cytotoxic Contributions, and Trypsin Sensitivity
Authors: Chen Jianming , McClane Bruce A. 
Published: April 2015

ABSTRACT

Large clostridial toxins (LCTs) are produced by at least four pathogenic clostridial species, and several LCTs are proven pivotal virulence factors for both human and veterinary diseases. TpeL is a recently identified LCT produced by
Clostridium perfringens
that has received relatively limited study. In response, the current study surveyed carriage of the
tpeL
gene among different
C. perfringens
strains, detecting this toxin gene in some type A, B, and C strains but not in any type D or E strains. This study also determined that all tested strains maximally produce, and extracellularly release, TpeL at the late-log or early-stationary growth stage during
in vitro
culture, which is different from the maximal late-stationary-phase production reported previously for other LCTs and for TpeL production by
C. perfringens
strain JIR12688. In addition, the present study found that TpeL levels in culture supernatants can be repressed by either glucose or sucrose. It was also shown that, at natural production levels, TpeL is a significant contributor to the cytotoxic activity of supernatants from cultures of
tpeL
-positive strain CN3685. Lastly, this study identified TpeL, which presumably is produced in the intestines during diseases caused by TpeL-positive type B and C strains, as a toxin whose cytotoxicity decreases after treatment with trypsin; this finding may have pathophysiologic relevance by suggesting that, like beta toxin, TpeL contributes to type B and C infections in hosts with decreased trypsin levels due to disease, diet, or age.
A Homology Model Reveals Novel Structural Features and an Immunodominant Surface Loop/Opsonic Target in the Treponema pallidum BamA Ortholog TP_0326
Authors: Luthra Amit , Anand Arvind , Hawley Kelly L. , LeDoyt Morgan , La Vake Carson J. , Caimano Melissa J. , Cruz Adriana R. , Salazar Juan C. , Radolf Justin D. 
Published: April 2015

ABSTRACTWe recently demonstrated that TP_0326 is a bona fide rare outer membrane protein (OMP) inTreponema pallidumand that it possesses characteristic BamA bipartite topology. Herein, we used immunofluorescence analysis (IFA) to show that only the β-barrel domain of TP_0326 contains surface-exposed epitopes in intactT. pallidum. Using the solved structure ofNeisseria gonorrhoeaeBamA, we generated a homology model of full-length TP_0326. Although the model predicts a typical BamA fold, the β-barrel harbors features not described in other BamAs. Structural modeling predicted that a dome comprised of three large extracellular loops, loop 4 (L4), L6, and L7, covers the barrel's extracellular opening. L4, the dome's major surface-accessible loop, contains mainly charged residues, while L7 is largely neutral and contains a polyserine tract in a two-tiered conformation. L6 projects into the β-barrel but lacks the VRGF/Y motif that anchors L6 within other BamAs. IFA and opsonophagocytosis assay revealed that L4 is surface exposed and an opsonic target. Consistent with B cell epitope predictions, immunoblotting and enzyme-linked immunosorbent assay (ELISA) confirmed that L4 is an immunodominant loop inT. pallidum-infected rabbits and humans with secondary syphilis. Antibody capture experiments usingEscherichia coliexpressing OM-localized TP_0326 as aT. pallidumsurrogate further established the surface accessibility of L4. Lastly, we found that a naturally occurring substitution (Leu593→ Gln593) in the L4 sequences ofT. pallidumstrains affects antibody binding in sera from syphilitic patients. Ours is the first study to employ a “structure-to-pathogenesis” approach to map the surface topology of aT. pallidumOMP within the context of syphilitic infection.IMPORTANCEPreviously, we reported that TP_0326 is a bona fide rare outer membrane protein (OMP) inTreponema pallidumand that it possesses the bipartite topology characteristic of a BamA ortholog. Using a homology model as a guide, we found that TP_0326 displays unique features which presumably relate to its function(s) in the biogenesis ofT. pallidum's unorthodox OM. The model also enabled us to identify an immunodominant epitope in a large extracellular loop that is both an opsonic target and subject to immune pressure in a human population. Ours is the first study to follow a structure-to-pathogenesis approach to map the surface topology of aT. pallidumrare OMP within the context of syphilitic infection.
Genome Modification in Enterococcus faecalis OG1RF Assessed by Bisulfite Sequencing and Single-Molecule Real-Time Sequencing
Authors: Huo Wenwen , Adams Hannah M. , Zhang Michael Q. , Palmer Kelli L. 
Published: April 2015

ABSTRACT

Enterococcus faecalis
is a Gram-positive bacterium that natively colonizes the human gastrointestinal tract and opportunistically causes life-threatening infections. Multidrug-resistant (MDR)
E. faecalis
strains have emerged, reducing treatment options for these infections. MDR
E. faecalis
strains have large genomes containing mobile genetic elements (MGEs) that harbor genes for antibiotic resistance and virulence determinants. Bacteria commonly possess genome defense mechanisms to block MGE acquisition, and we hypothesize that these mechanisms have been compromised in MDR
E. faecalis
. In restriction-modification (R-M) defense, the bacterial genome is methylated at cytosine (C) or adenine (A) residues by a methyltransferase (MTase), such that nonself DNA can be distinguished from self DNA. A cognate restriction endonuclease digests improperly modified nonself DNA. Little is known about R-M in
E. faecalis
. Here, we use genome resequencing to identify DNA modifications occurring in the oral isolate OG1RF. OG1RF has one of the smallest
E. faecalis
genomes sequenced to date and possesses few MGEs. Single-molecule real-time (SMRT) and bisulfite sequencing revealed that OG1RF has global 5-methylcytosine (m5C) methylation at 5′-GCWGC-3′ motifs. A type II R-M system confers the m5C modification, and disruption of this system impacts OG1RF electrotransformability and conjugative transfer of an antibiotic resistance plasmid. A second DNA MTase was poorly expressed under laboratory conditions but conferred global
N
4
-methylcytosine (m4C) methylation at 5′-CCGG-3′ motifs when expressed in
Escherichia coli
. Based on our results, we conclude that R-M can act as a barrier to MGE acquisition and likely influences antibiotic resistance gene dissemination in the
E. faecalis
species.

IMPORTANCE
The horizontal transfer of antibiotic resistance genes among bacteria is a critical public health concern.
Enterococcus faecalis
is an opportunistic pathogen that causes life-threatening infections in humans. Multidrug resistance acquired by horizontal gene transfer limits treatment options for these infections. In this study, we used innovative DNA sequencing methodologies to investigate how a model strain of
E. faecalis
discriminates its own DNA from foreign DNA, i.e., self versus nonself discrimination. We also assess the role of an
E. faecalis
genome modification system in modulating conjugative transfer of an antibiotic resistance plasmid. These results are significant because they demonstrate that differential genome modification impacts horizontal gene transfer frequencies in
E. faecalis
.