bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extended-Spectrum β-Lactamases in
Enterobacteriaceae
in Buenos Aires, Argentina, Public Hospitals
Authors: Quinteros M. , Radice M. , Gardella N. , Rodriguez M. M. , Costa N. , Korbenfeld D. , Couto E. , Gutkind G. 
Published: August 2003

ABSTRACT

Resistance to extended-spectrum cephalosporins is often associated with plasmid encoded extended spectrum β-lactamases (ESBL). In order to evaluate the prevalence and diversity of ESBLs in enterobacteria in our city, a 1-month-period survey was carried out from April to May 2000. Extended-spectrum-cephalosporin-resistant strains, isolated from inpatient clinical specimens other than stools, were collected among 17 participating hospitals. From a total of 427 enterobacterial strains that were collected during this period, 39 were extended-spectrum cephalosporin resistant. The National Committee for Clinical Laboratory Standards' Screening and Confirmatory Tests for ESBL production were performed using cefotaxime and ceftazidime; cefepime and cefepime-clavulanic acid-containing disks were included. β-Lactamases were characterized by isoelectric focusing and PCR amplification using specific primers. Three different ESBLs were detected: SHV-related (4 isolates), PER-2-type (9 isolates), and CTX-M-2-related (26 isolates). Sequencing of the corresponding genes confirmed CTX-M-2 in 19 of 21 and CTX-M-31 (an allelic variant) in the remaining 2 of 21. CTX-M-2 (or its variant) was detected in all
Escherichia coli
,
Enterobacter aerogenes
,
Serratia marcescens
,
Proteus mirabilis
, and
Providencia stuartii
strains, while PER-2 was detected in
Enterobacter cloacae
,
E. aerogenes
, and
Klebsiella pneumoniae
; SHV-related ESBL were found only in
K. pneumoniae
. These results clearly show that CTX-M-2 is the most prevalent ESBL produced by enterobacterial species isolated from public hospitals in Buenos Aires.
Microcin C51 Plasmid Genes: Possible Source of Horizontal Gene Transfer
Authors: Fomenko Dmitri E. , Metlitskaya Anastazia Z. , Péduzzi Jean , Goulard Christophe , Katrukha Genrikh S. , Gening Leonid V. , Rebuffat Sylvie , Khmel Inessa A. 
Published: August 2003

ABSTRACT

Microcin C51 (MccC51) is an antimicrobial nucleotide-heptapeptide produced by a natural
Escherichia coli
strain. A 5.7-kb fragment of the pC51 plasmid carrying the genes involved in MccC51 production, secretion, and self-immunity was sequenced, and the genes were characterized. The sequence of the MccC51 gene cluster is highly similar to that of the MccC7 gene. Recombinant plasmids carrying different combinations of the
mcc
genes involved in the MccC51 production or immunity were constructed to characterize their functional roles. The
mccA
,
mccB
,
mccD
, and
mccE
genes are involved in MccC51 production, while the
mccC
and
mccE
genes are responsible for immunity to MccC51. The
mcc
gene cluster is flanked by 44-bp direct repeats. Amino acid sequence comparisons allowed us to propose functions for each Mcc polypeptide in MccC51 biosynthesis. Plasmid pUHN containing the cloned
mccA
,
mccB
,
mccC
, and
mccE
genes, but lacking
mccD
, directed the synthesis of MccC51p, a substance chemically related to MccC51. MccC51p exhibited weak antibiotic activity against
E. coli
and was toxic to the producing cells. The immunity to exogenous MccC51 determined by the
mccC
and
mccE
genes did not overcome the toxic action of MccC51p on the producing cells. The G+C content of the MccC51 operon, markedly lower than that of the
E. coli
genome, and the presence of direct repeats suggest the possibility of horizontal transfer of this gene cluster.
Intracellular Expression of Peptide Fusions for Demonstration of Protein Essentiality in Bacteria
Authors: Benson R. Edward , Gottlin Elizabeth B. , Christensen Dale J. , Hamilton Paul T. 
Published: August 2003

ABSTRACT

We describe a “protein knockout” technique that can be used to identify essential proteins in bacteria. This technique uses phage display to select peptides that bind specifically to purified target proteins. The peptides are expressed intracellularly and cause inhibition of growth when the protein is essential. In this study, peptides that each specifically bind to one of seven essential proteins were identified by phage display and then expressed as fusions to glutathione
S
-transferase in
Escherichia coli.
Expression of peptide fusions directed against
E. coli
DnaN, LpxA, RpoD, ProRS, SecA, GyrA, and Era each dramatically inhibited cell growth. Under the same conditions, a fusion with a randomized peptide sequence did not inhibit cell growth. In growth-inhibited cells, inhibition could be relieved by concurrent overexpression of the relevant target protein but not by coexpression of an irrelevant protein, indicating that growth inhibition was due to a specific interaction of the expressed peptide with its target. The protein knockout technique can be used to assess the essentiality of genes of unknown function emerging from the sequencing of microbial genomes. This technique can also be used to validate proteins as drug targets, and their corresponding peptides as screening tools, for discovery of new antimicrobial agents.
Epidemiological Risk Factors for Isolation of Ceftriaxone-Resistant versus -Susceptible
Citrobacter freundii
in Hospitalized Patients
Authors: Kim Peter W. , Harris Anthony D. , Roghmann Mary-Claire , Morris J. Glenn , Strinivasan Arjun , Perencevich Eli N. 
Published: August 2003

ABSTRACT

Antimicrobial resistance is an emerging problem among nosocomial bacteria. Risk factors for the recovery of ceftriaxone-resistant (CRCF) or -susceptible (CSCF)
Citrobacter freundii
in clinical cultures from hospitalized patients were determined by using a case-case-control study design. CRCF was isolated from 43 patients (case group 1) and CSCF was isolated from 87 patients (case group 2) over a 3-year period. Risk factors for CRCF were exposure to imipenem (odds ratio [OR], 7.5; 95% confidence interval [CI], 1.2 to 45.4), broad-spectrum cephalosporins (OR, 6.9; 95% CI, 1.8 to 26.7), vancomycin (OR, 3.0; 95% CI, 1.2 to 7.4), or piperacillin-tazobactam (OR, 2.6; 95% CI, 1.1 to 6.2), as well as hospital length of stay ≥1 week (OR, 3.6; 95% CI, 1.3 to 10.2) and intensive care unit (ICU) stay (OR, 2.6; 95% CI, 1.1 to 6.2). Risk factors for CSCF were peripheral vascular disease (OR, 23.2; 95% CI, 4.3 to 124.6), AIDS (OR, 9.5; 95% CI, 1.6 to 55.5), cerebrovascular disease (OR, 4.2; 95% CI, 1.6 to 10.8), and ICU stay (OR, 3.1; 95% CI, 1.8 to 5.4).
Optimal Sampling Schedule Design for Populations of Patients
Authors: Tam Vincent H. , Preston Sandra L. , Drusano G. L. 
Published: August 2003

ABSTRACTGeneration of pharmacodynamic relationships in the clinical arena requires estimation of pharmacokinetic parameter values for individual patients. When the target population is severely ill, the ability to obtain traditional intensive blood sampling schedules is curtailed. Population modeling guided by optimal sampling theory has provided robust estimates of individual patient pharmacokinetic parameter values. Because of the wide range of parameter values seen in this circumstance, it is important to know how the range of parameter values in the population affects the timing of the optimal samples. We describe a new, simple technique to obtain optimal samples for a population of patients. This technique uses the nonparametric distribution associated with a nonparametric adaptive grid population pharmacokinetic analysis. We used the distribution from an analysis of 58 patients receiving levofloxacin for nosocomial pneumonia at a dose of 750 mg. The collection of parameter vectors and their associated probabilities were entered into a D-optimal design evaluation by using ADAPT II. The sampling times, weighted for their probabilities, were displayed in a frequency histogram (an expression of how system information varies with time for the population). Such an explicit expression of the time distribution of information allows rational sampling design that is robust not only for the population mean vector, as in traditional D-optimal design theory, but also for large portions of the total population. For levofloxacin, one reasonable six-sample design would be 1.5, 2, 2.25, 4, 4.75, and 24 h after starting a 90-min infusion. Such sampling designs allow informative population pharmacokinetic analysis with precise and unbiased estimates after the maximal a posteriori probability Bayesian step. This allows the highest probability of delineating a pharmacodynamic relationship.
Resistance to the Peptidyl Transferase Inhibitor Tiamulin Caused by Mutation of Ribosomal Protein L3
Authors: Bøsling Jacob , Poulsen Susan M. , Vester Birte , Long Katherine S. 
Published: August 2003

ABSTRACTThe antibiotic tiamulin targets the 50S subunit of the bacterial ribosome and interacts at the peptidyl transferase center. Tiamulin-resistantEscherichia colimutants were isolated in order to elucidate mechanisms of resistance to the drug. No mutations in the rRNA were selected as resistance determinants using a strain expressing only a plasmid-encoded rRNA operon. Selection in a strain with all seven chromosomal rRNA operons yielded a mutant with an A445G mutation in the gene coding for ribosomal protein L3, resulting in an Asn149Asp alteration. Complementation experiments and sequencing of transductants demonstrate that the mutation is responsible for the resistance phenotype. Chemical footprinting experiments show a reduced binding of tiamulin to mutant ribosomes. It is inferred that the L3 mutation, which points into the peptidyl transferase cleft, causes tiamulin resistance by alteration of the drug-binding site. This is the first report of a mechanism of resistance to tiamulin unveiled in molecular detail.
The Aminoglycoside 6′-
N
-Acetyltransferase Type Ib Encoded by Tn
1331
Is Evenly Distributed within the Cell's Cytoplasm
Authors: Dery Ken J. , Søballe Britta , Witherspoon Mavee S. L. , Bui Duyen , Koch Robert , Sherratt David J. , Tolmasky Marcelo E. 
Published: August 2003

ABSTRACT

The multiresistance transposon Tn
1331
, which mediates resistance to several aminoglycosides and β-lactams, includes the
aac(6′)-Ib
,
aadA1
,
bla
OXA-9
, and
bla
TEM-1
genes. The nucleotide sequence of
aac(6′)-Ib
includes a region identical to that of the
bla
TEM-1
gene. This region encompasses the promoter and the initiation codon followed by 15 nucleotides. Since there were three possible translation initiation sites, the amino acid sequence at the N terminus of the aminoglycoside 6′-
N
-acetyltransferase type Ib [AAC(6′)-Ib] was determined and was found to be SIQHF. This result indicated that
aac(6′)-Ib
includes a translational fusion: the first five amino acids of the leader peptide of the TEM β-lactamase are fused to the rest of the AAC(6′)-Ib protein. This gene fusion could have formed during the genesis of Tn
1331
as a consequence of the generation of a 520-nucleotide duplication (M. E. Tolmasky, Plasmid
24:
218-226, 1990). An identical gene isolated from a
Serratia marcescens
strain has been previously described (G. Tran van Nhieu and E. Collatz, J. Bacteriol.
169:
5708-5714, 1987). Extraction of the periplasmic proteins of
E. coli
harboring
aac(6′)-Ib
by spheroplast formation showed that most of the AAC(6′)-Ib protein is present in the cytoplasm. A genetic fusion to
phoA
confirmed these results. AAC(6′)-Ib was shown to be evenly distributed inside the cell's cytoplasm by fluorescent microscopy with an AAC(6′)-Ib-cyan fluorescent protein fusion.
Signature Gene Expression Profiles Discriminate between Isoniazid-, Thiolactomycin-, and Triclosan-Treated
Mycobacterium tuberculosis
Authors: Betts Joanna C. , McLaren Alistair , Lennon Mark G. , Kelly Fiona M. , Lukey Pauline T. , Blakemore Steve J. , Duncan Ken 
Published: August 2003

ABSTRACT

Genomic technologies have the potential to greatly increase the efficiency of the drug development process. As part of our tuberculosis drug discovery program, we used DNA microarray technology to profile drug-induced effects in
Mycobacterium tuberculosis
. Expression profiles of
M. tuberculosis
treated with compounds that inhibit key metabolic pathways are required as references for the assessment of novel antimycobacterial agents. We have studied the response of
M. tuberculosis
to treatment with the mycolic acid biosynthesis inhibitors isoniazid, thiolactomycin, and triclosan. Thiolactomycin targets the β-ketoacyl-acyl carrier protein (ACP) synthases KasA and KasB, while triclosan inhibits the enoyl-ACP reductase InhA. However, controversy surrounds the precise mode of action of isoniazid, with both InhA and KasA having been proposed as the primary target. We have shown that although the global response profiles of isoniazid and thiolactomycin are more closely related to each other than to that of triclosan, there are differences that distinguish the mode of action of these two drugs. In addition, we have identified two groups of genes, possibly forming efflux and detoxification systems, through which
M. tuberculosis
may limit the effects of triclosan. We have developed a mathematical model, based on the expression of 21 genes, which is able to perfectly discriminate between isoniazid-, thiolactomycin-, or triclosan-treated
M. tuberculosis
. This model is likely to prove invaluable as a tool to improve the efficiency of our drug development programs by providing a means to rapidly confirm the mode of action of thiolactomycin analogues or novel InhA inhibitors as well as helping to translate enzyme activity into whole-cell activity.
Antiviral Effects of Geranylgeranylacetone: Enhancement of MxA Expression and Phosphorylation of PKR during Influenza Virus Infection
Authors: Unoshima Masako , Iwasaka Hideo , Eto Junko , Takita-Sonoda Yoshiko , Noguchi Takayuki , Nishizono Akira 
Published: August 2003

ABSTRACTA cyclic polyisoprenoid compound, geranylgeranylacetone (GGA), has been used as antiulcer drug. GGA is also a potent inducer of heat shock proteins (HSPs). HSPs are considered to induce an antiviral effect; however, the detailed mechanism is unknown. To determine whether GGA might show antiviral activity and what the mechanism is, the effect of GGA against influenza virus (strain PR8) infection in vivo and in vitro was investigated. The results demonstrated that GGA treatment strongly suppressed the deleterious consequences of PR8 replication and was accompanied by an increase in HSP70 gene expression in mice. Results from in vitro analyses demonstrated that GGA significantly inhibited the synthesis of PR8-associated proteins and prominently enhanced expression of human myxovirus resistance 1 (MxA) followed by increased HSP70 transcription. Moreover, GGA augmented the expression of an interferon-inducible double-strand RNA-activated protein kinase (PKR) gene and promoted PKR autophosphorylation and concomitantly α subunit of eukaryotic initiation factor 2 phosphorylation during PR8 infection. It is proposed that GGA-induced HSP70 has potent antiviral activity by enhancement of antiviral factors and can clinically achieve protection from influenza virus infection.
New
Klebsiella oxytoca
β-Lactamase Genes
bla
OXY-3
and
bla
OXY-4
and a Third Genetic Group of
K. oxytoca
Based on
bla
OXY-3
Authors: Granier Sophie A. , Leflon-Guibout Véronique , Goldstein Fred W. , Nicolas-Chanoine Marie-Hélène 
Published: August 2003

ABSTRACT

The two genetic groups (oxy-1 and oxy-2) previously identified in the
Klebsiella oxytoca
taxon are recognizable by four independent molecular markers: (i) ERIC-1R profiles, (ii) 16S ribosomal DNA (rDNA) signature sequences, (iii) singular nucleotides in a defined fragment of the
rpoB
gene, and (iv) the type of the strain's
bla
OXY
gene (i.e.,
bla
OXY-1
or
bla
OXY-2
).
K. oxytoca
strains SG266 and SG271 could not be classified into these genetic groups based on their ERIC-1R profile and
bla
OXY
gene sequence. With regard to the gene identity percentages between the
bla
OXY-1
and
bla
OXY-2
gene groups (86.8% ± 0.4%) and within a
bla
OXY
gene group (>99%), it was concluded that the
bla
OXY
gene of strain SG271 was representative of a new
bla
OXY
gene group (
bla
OXY-3
), since the mean identity percentages between it and the two
bla
OXY
gene groups were 85.5% ± 0.2% and 84.4% ± 0.4%, respectively. Since the corresponding percentages were 95.0% ± 0.4% and 86.2% ± 0.3% for strain SG266, it was impossible to classify its
bla
OXY
gene, which was therefore named
bla
OXY-4
. The 16S rDNA signature sequences of the two strains could be determined only after cloning experiments. The SG266 clones displayed the same signature sequence as that of the genetic group oxy-1, whereas the SG271 clones displayed three different 16S rDNA signature sequences that also differed from those of the two genetic groups. Singular nucleotides were found within the
rpoB
sequence of the two strains, allowing for their distinction from the two genetic groups. All of these results, combined with those previously obtained by the ERIC-1R PCR method, indicate that strain SG271 is representative of a new
K. oxytoca
genetic group (oxy-3), whereas strain SG266 could not be classified.
Sulfadoxine-Pyrimethamine in Treatment of Malaria in Western Kenya: Increasing Resistance and Underdosing
Authors: Terlouw Dianne J. , Nahlen Bernard L. , Courval Jeanne M. , Kariuki Simon K. , Rosenberg Oren S. , Oloo Aggrey J. , Kolczak Margarette S. , Hawley William A. , Lal Altaf A. , Kuile Feiko O. ter 
Published: August 2003

ABSTRACT

Between 1993 and 1999, we monitored the efficacy of sulfadoxine-pyrimethamine in 1,175 children aged <24 months receiving 2,789 treatments for falciparum malaria in western Kenya using a widely deployed age-based dose regimen: infants, 125 plus 6.25 mg (sulfadoxine plus pyrimethamine); children aged 12 to 23 months; 250 plus 12.5 mg. Cumulative treatment failure by day 7, defined as early clinical failure by day 3 or presence of parasitemia on day 7, increased from 18% in 1993 to 1994 to 22% in 1997 to 1998 (
P
-trend test = 0.20). Based on body weight, the median dose received was 20 plus 1.00 mg/kg, and 73% of the treatments were given at lower than the recommended target dose of 25 plus 1.25 mg/kg. Underdosing accounted for 26% of cumulative treatment failures. After the dose was increased in 1998 (median, 36 plus 1.8 mg/kg), only 4.2% of patients received less than 25 plus 1.25 mg/kg and there was no association with treatment failure. However, the proportion of cumulative treatment failure continued to increase to 27% by 1999 (
P
-trend test = 0.03). These results raise concern about the longevity of sulfadoxine-pyrimethamine in these settings. Underdosing may have contributed to the rate at which sulfadoxine-pyrimethamine resistance developed in this area. Treatment guidelines should ensure that adequate doses are given from the initial deployment of antimalarials onward.
Aerosolized Cidofovir Is Retained in the Respiratory Tract and Protects Mice against Intranasal Cowpox Virus Challenge
Authors: Roy Chad J. , Baker Robert , Washburn Kenneth , Bray Mike 
Published: August 2003

ABSTRACT

We employed a murine model to test the concept of using an aerosolized, long-acting antiviral drug to protect humans against smallpox. We previously showed that a low dose of aerosolized cidofovir (HPMPC [Vistide]) was highly protective against subsequent aerosolized cowpox virus challenge and was more effective than a much larger dose of drug given by injection, suggesting that aerosolized cidofovir is retained in the lung. Because the nephrotoxicity of cidofovir is a major concern in therapy, delivering the drug directly to the respiratory tract might be an effective prophylactic strategy that maximizes the tissue concentration at the site of initial viral replication, while minimizing its accumulation in the kidneys. In the present study, we found that treating mice with aerosolized
14
C-labeled cidofovir (
14
C-cidofovir) resulted in the prolonged retention of radiolabeled drug in the lungs at levels greatly exceeding those in the kidneys. In contrast, subcutaneous injection produced much higher concentrations of
14
C-cidofovir in the kidneys than in the lungs over the 96-h time course of the study. As further evidence of the protective efficacy of aerosolized cidofovir, we found that aerosol treatment before or after infection was highly protective in mice challenged intranasally with cowpox virus. All or nearly all mice that were treated once by aerosol, from 2 days before to 2 days after challenge, survived intranasal infection, whereas all placebo-treated animals died.
Insertion Sequence IS
Ecp1B
Is Involved in Expression and Mobilization of a
bla
CTX-M
β-Lactamase Gene
Authors: Poirel Laurent , Decousser Jean-Winoc , Nordmann Patrice 
Published: August 2003

ABSTRACT

The genetic structures (ca. 10-kb DNA fragment) surrounding the plasmid-borne extended-spectrum β-lactamase
bla
CTX-M-19
gene in a
Klebsiella pneumoniae
clinical isolate were determined. This β-lactamase gene was part of a 4,797-bp transposon inserted inside
orf1
of Tn
1721.
Inside this transposon,
bla
CTX-M-19
was bracketed upstream and downstream by insertion sequences IS
E cp1B
and IS
903D,
respectively, and further downstream by a truncated gene encoding an outer membrane protein for iron transport. The single-copy IS
Ecp1B
element was probably involved alone in the mobilization process that led to a 5-bp duplication at the target site of the transposed fragment. This mobilization event probably involved one inverted repeat of IS
E cp1B
and a second sequence farther away, resembling its second inverted repeat. Additionally, IS
Ecp1B
provided −35 and −10 promoter sequences, contributing to the high-level expression of the
bla
CTX-M-19
gene. Southern blot analysis failed to identify a reservoir of IS
Ecp1
-like sequences among a series of gram-negative and gram-positive bacterial species usually found in the skin and intestinal human floras. The ability of IS
Ecp1
-like elements to mobilize and to promote the expression of β-lactamase genes may explain, in part, the current spread of CTX-M-type enzymes worldwide.
In Vitro Activities of New Fluoroquinolones against
Campylobacter jejuni
and
Campylobacter coli
Isolates Obtained from Humans in 1980 to 1982 and 1997 to 2001
Authors: Krausse Rea , Ullmann Uwe 
Published: August 2003

ABSTRACT

The antibacterial activities of three newly developed fluoroquinolones (gatifloxacin, levofloxacin, and moxifloxacin) against a total of 307 gastrointestinal human isolates of
Campylobacter jejuni
and
Campylobacter coli
collected during 1980 to 1982 and 1997 to 2001 were examined and compared to those of ciprofloxacin and the unrelated antibacterial agents, clarithromycin, erythromycin, and tetracycline by using the agar plate dilution method. All of the fluoroquinolones exhibited a good activity against
Campylobacter
, and some of them were more active than ciprofloxacin, the macrolides, and tetracycline. Among the fluoroquinolones, gatifloxacin and moxifloxacin showed the highest anticampylobacter activity, with MICs at which 50% of the isolates tested are inhibited (MIC
50
s) and MIC
90
s of 0.125 and 4 μg/ml, respectively; the MIC
50
for both levofloxacin and ciprofloxacin was 0.25, and the MIC
90
s were 16 and 32 μg/ml, respectively. About 30% of the strains were found to be resistant to at least one fluoroquinolone. Resistance to gatifloxacin occurred in 9.8% of the isolates tested, and resistance to the other fluoroquinolones occurred in 19.9 to 27.4% of the isolates tested; the frequency of cross-resistance was 35.7 to 100%. An increase in fluoroquinolone resistance from 0% in 1980 to 1982 to 11.8 to 29% in 1997 and 1998, 8.2 to 31.8% in 1999 and 2000, and 12.1 to 30.3% in 2001 was found. A total of 61.4 to 73.2% of the
C. jenuni
strains resistant to erythromycin, clarithromycin, and/or tetracycline were susceptible to fluoroquinolones; gatifloxacin showed the highest percentage of inhibition. These results show that the newer fluoroquinolones with their potent activity could be used to treat infections with
C. jejuni
and
C. coli.
However, when these drugs are used, one must consider the increase in resistance and the high cross-resistance to these antimicrobial agents.