bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Characterization of Chromosomal Class C β-Lactamase and Its Regulatory Gene in
Ochrobactrum anthropi
Authors: Nadjar David , Labia Roger , Cerceau Claude , Bizet Chantal , Philippon Alain , Arlet Guillaume 
Published: July 2002

ABSTRACT

Ochrobactrum anthropi
, formerly known as CDC group Vd, is an oxidase-producing, gram-negative, obligately aerobic, non-lactose-fermenting bacillus of low virulence that occasionally causes human infections. It is highly resistant to all β-lactams except imipenem. A clinical isolate, SLO74, and six reference strains were tested. MICs of penicillins, aztreonam, and most cephalosporins tested, including cefotaxime and ceftazidime, were >128 μg/ml and of cefepime were 64 to >128 μg/ml. Clavulanic acid was ineffective and tazobactam had a weak effect in association with piperacillin. Two genes,
ampR
and
ampC
, were cloned by inserting restriction fragments of genomic DNA from the clinical strain
O. anthropi
SLO74 into pBK-CMV to give the recombinant plasmid pBK-OA1. The pattern of resistance to β-lactams of this clone was similar to that of the parental strain, except for its resistance to cefepime (MIC, 0.5 μg/ml). The deduced amino acid sequence of the AmpC β-lactamase (pI, 8.9) was only 41 to 52% identical to the sequence of other chromosomally encoded and plasmid-encoded class C β-lactamases. The kinetic properties of this β-lactamase were typical for this class of β-lactamases. Upstream from the
ampC
gene, the
ampR
gene encodes a protein with a sequence that is 46 to 62% identical to those of other AmpR proteins and with an amino-terminal DNA-binding domain typical of transcriptional activators of the Lys-R family. The deduced amino acid sequences of the
ampC
genes of the six reference strains were 96 to 99% identical to the sequence of the clinical strain. The β-lactamase characterized from strain SLO74 was named OCH-1 (gene,
bla
OCH-I
).
Mutation in
Serratia marcescens
AmpC β-Lactamase Producing High-Level Resistance to Ceftazidime and Cefpirome
Authors: Raimondi Alessandro , Sisto Francesca , Nikaido Hiroshi 
Published: July 2002

ABSTRACT

Starting from a clinical isolate of
Serratia marcescens
that produced a chromosomally encoded AmpC β-lactamase inducibly, we isolated by stepwise selection two laboratory mutants that showed high levels of resistance to some cephalosporins. The 98R mutant apparently overproduced the unaltered β-lactamase constitutively, but the 520R mutant produced an altered enzyme, also constitutively. Ceftazidime and cefpirome MICs for the 520R mutant were much higher (512 and 64 μg/ml, respectively) than those for the 98R mutant (16 and 16 μg/ml, respectively). Yet the MICs of cephaloridine and piperacillin for the 520R mutant were four- to eightfold lower than those for the 98R mutant. Cloning and sequencing of the
ampC
alleles showed that in the 520R mutant enzyme, the Thr64 residue, about two turns away from the active-site serine, was mutated to isoleucine. This resulted in a >1,000-fold increase in the catalytic efficiency (
k
cat
/
K

m

) of the mutated AmpC enzyme toward ceftazidime, whereas there was a >10-fold decrease in the efficiency of the mutant enzyme toward cefazolin and cephaloridine. The outer membrane permeability of the 520R strain to cephalosporins was also less than in the 98R strain, and the alteration of the kinetic properties of the AmpC enzyme together with this difference in permeability explained quantitatively the resistance levels of both mutant strains to most agents studied.
In Vitro and In Vivo Antibacterial Activities of TAK-083, an Agent for Treatment of
Helicobacter pylori
Infection
Authors: Kanamaru Tsuneo , Nakano Yoshitaka , Toyoda Yukio , Miyagawa Ken-Ichiro , Tada Mayumi , Kaisho Tomoko , Nakao Masafumi 
Published: July 2002

ABSTRACT

The antibacterial activity of TAK-083 was tested against 54 clinical isolates of
Helicobacter pylori
and was compared with those of amoxicillin, clarithromycin, and metronidazole. The growth-inhibitory activity of TAK-083 was more potent than that of amoxicillin, clarithromycin, or metronidazole (the MICs at which 90% of the strains are inhibited were 0.031, 0.125, 64, and 8 μg/ml, respectively). The antibacterial activity of TAK-083 was highly selective against
H. pylori
; there was a >30-fold difference between the concentration of TAK-083 required to inhibit the growth of
H. pylori
and that required to inhibit the growth of common aerobic and anaerobic bacteria. Exposure of
H. pylori
strains to TAK-083 at the MIC or at a greater concentration resulted in an extensive loss of viability. When four
H. pylori
strains were successively subcultured in the medium containing subinhibitory concentrations of TAK-083, no significant change in the MICs of this compound was observed. TAK-083 strongly inhibited the formation of tryptophanyl-tRNA in
H. pylori
while exhibiting little effect on the same system in eukaryotes. TAK-083 was efficacious in the treatment of gastric infection caused by
H. pylori
in Mongolian gerbils. The results presented here indicate that TAK-083 is a promising candidate for the treatment of
H. pylori
infection.
Carrier-Mediated Partitioning of Artemisinin into
Plasmodium falciparum
-Infected Erythrocytes
Authors: Vyas Nehal , Avery Bonnie A. , Avery Mitchell A. , Wyandt Christy M. 
Published: July 2002

ABSTRACT

The purpose of the present study was to characterize the partitioning of artemisinin into both uninfected and
Plasmodium falciparum
-infected red blood cells (RBCs). The partitioning of [
14
C](+)-artemisinin into RBCs was studied at four different hematocrit levels and eight time periods. At the optimum time of 2 h, the partitioning process was investigated with eight different drug concentrations ranging from 0.88 to 3.52 μM at 37 and 4°C. The effect of the presence of unlabeled artemisinin on the partitioning of the same concentration of [
14
C]artemisinin was studied. About 35 to 40% of the drug was seen to partition into uninfected RBCs at a hematocrit of 33%, irrespective of the incubation period or the drug concentration used. In contrast, infected RBCs showed an increase in partitioning of the drug with time until saturation was achieved at 1 h. While the partitioning of artemisinin into parasitized RBCs at 37°C was found to be significantly higher than that in nonparasitized RBCs, at 4°C both parasitized and nonparasitized RBCs showed identical partitioning of the drug. The partitioning of [
14
C]artemisinin into parasitized RBCs was completely inhibited in the presence of the same concentration of unlabeled artemisinin. However, no such effect was observed in nonparasitized cells, and no evidence suggesting that binding of the drug in parasitized RBCs is reversible was found. The partitioning of artemisinin into parasitized RBCs was found to be rapid, saturable, temperature dependent, irreversible, and subject to competitive inhibition with unlabeled artemisinin. The results obtained suggest the involvement of carrier mediation in the partitioning of artemisinin across the parasitized RBC membrane. In contrast, simple passive diffusion of artemisinin was seen in nonparasitized RBCs.
Vancomycin-Resistant Enterococci from Humans and Retail Chickens in Taiwan with Unique VanB Phenotype-
vanA
Genotype Incongruence
Authors: Lauderdale Tsai-Ling , McDonald L. Clifford , Shiau Yih-Ru , Chen Pei-Chen , Wang Hui-Yin , Lai Jui-Fen , Ho Monto 
Published: July 2002

ABSTRACT

Vancomycin resistant enterococci (VRE) with VanB phenotype-
vanA
genotype incongruence were found in all 39 VRE isolated from chicken carcasses and four human VRE isolates in Taiwan. Three identical mutations in the
vanS
gene were found in the VanB phenotype-
vanA
genotype VRE sequenced. This finding indicates possible transmission of glycopeptide resistance among different hosts.
Potato Dextrose Agar Antifungal Susceptibility Testing for Yeasts and Molds: Evaluation of Phosphate Effect on Antifungal Activity of CMT-3
Authors: Liu Yu , Tortora George , Ryan Maria E. , Lee Hsi-Ming , Golub Lorne M. 
Published: July 2002

ABSTRACT

The broth macrodilution method (BMM) for antifungal susceptibility testing, approved by the National Committee for Clinical Laboratory Standards (NCCLS), was found to have deficiencies in testing of the antifungal activity of a new type of antifungal agent, a nonantibacterial chemically modified tetracycline (CMT-3). The high content of phosphate in the medium was found to greatly increase the MICs of CMT-3. To avoid the interference of phosphate in the test, a new method using potato dextrose agar (PDA) as a culture medium was developed. Eight strains of fungi, including five American Type Culture Collection strains and three clinical isolates, were used to determine the MICs of amphotericin B and itraconazole with both the BMM and the PDA methods. The MICs of the two antifungal agents determined with the PDA method showed 99% agreement with those determined with the BMM method within 1 log
2
dilution. Similarly, the overall reproducibility of the MICs with the PDA method was above 97%. Three other antifungal agents, fluconazole, ketoconazole, and CMT-3, were also tested in parallel against yeasts and molds with both the BMM and the PDA methods. The MICs of fluconazole and ketoconazole determined with the PDA method showed 100% agreement within 1 log
2
dilution of those obtained with the BMM method. However, the MICs of CMT-3 determined with the BMM method were as high as 128 times those determined with the PDA method. The effect of phosphate on the antifungal activity of CMT-3 was evaluated by adding Na
2
HPO
4
to PDA in the new method. It was found that the MIC of CMT-3 against a
Penicillium
sp. increased from 0.5 μg/ml (control) to 2.0 μg/ml when the added phosphate was used at a concentration of 0.8 mg/ml, indicating a strong interference of Na
2
HPO
4
with the antifungal activity of CMT-3. Except for fluconazole, all the other antifungal agents demonstrated clear end points among the yeasts and molds tested. Nevertheless, with its high reproducibility, good agreement with NCCLS proposed MIC ranges, and lack of interference of phosphate, the PDA method shows promise as a useful assay for antifungal susceptibility testing and screening for new antifungal agents, especially for drugs that may be affected by high (supraphysiologic) phosphate concentrations.
Antimicrobial Activity of a Novel Catheter Lock Solution
Authors: Shah Chirag B. , Mittelman Marc W. , Costerton J. W. , Parenteau Stephen , Pelak Michael , Arsenault Richard , Mermel Leonard A. 
Published: July 2002

ABSTRACT

Intravascular catheter-associated bloodstream infections significantly increase rates of morbidity and hospital costs. Microbial colonization and development of biofilms, which are known to be recalcitrant to antibiotic therapy, often lead to the loss of otherwise patent vascular access systems. We evaluated a new taurolidine- and citrate-based catheter lock solution (Neutrolin; Biolink Corporation, Norwell, Mass.) for its activity against planktonic microbes, antimicrobial activity in a catheter model, and biofilm eradication activity. In studies of planktonic microbes, after 24 h of contact, 675 mg of taurolidine-citrate solution per liter caused >99% reductions in the initial counts of
Staphylococcus aureus
,
Staphylococcus epidermidis
,
Pseudomonas aeruginosa
, and
Entercoccus faecalis.
A solution of 13,500 mg/liter was cidal for
Candida albicans
. Ports and attached catheters inoculated with 50 to 600 CFU of these bloodstream isolates per ml were locked with heparin or the taurolidine-citrate solution. After 72 h, there was no growth in the taurolidine-citrate-treated devices but the heparin-treated devices exhibited growth in the range of 6 × 10
2
to 5 × 10
6
CFU/ml. Biofilms were developed on silicone disks in modified Robbins devices with broth containing 6% serum (initial counts, 10
6
to 10
8
CFU/cm
2
). The axenic biofilms were treated for 24 h with taurolidine-citrate or heparin. Taurolidine-citrate exposure resulted in a median reduction of 4.8 logs, whereas heparin treatment resulted in a median reduction of 1.7 logs (
P
< 0.01). No significant differences in the effects of the two treatments against
P. aeruginosa
and
C. albicans
were observed. These findings suggest that taurolidine-citrate is a promising combination agent for the prevention and treatment of intravascular catheter-related infections.
Antibacterial Activities and Characterization of Novel Inhibitors of LpxC
Authors: Clements John M. , Coignard Fanny , Johnson Ian , Chandler Stephen , Palan Shilpa , Waller Andrew , Wijkmans Jac , Hunter Michael G. 
Published: July 2002

ABSTRACT

Lipid A is the hydrophobic anchor of lipopolysaccharide (LPS) and forms the major lipid component of the outer monolayer of the outer membrane of gram-negative bacteria. Lipid A is required for bacterial growth and virulence, and inhibition of its biosynthesis is lethal to bacteria. UDP-3-
O
-(
R
-3-hydroxymyristoyl)-
N
-acetylglucosamine deacetylase (LpxC) is a metalloenzyme that catalyzes the second step in the biosynthesis of lipid A. Inhibitors of LpxC have previously been shown to have antibiotic activities. We have screened a metalloenzyme inhibitor library for antibacterial activities against an
Escherichia coli
strain with reduced LpxC activity. From this screen, a series of sulfonamide derivatives of the α-(
R
)-amino hydroxamic acids, exemplified by BB-78484 and BB-78485, have been identified as having potent inhibitory activities against LpxC in an in vitro assay. Leads from this series showed gram-negative selective activities against members of the
Enterobacteriaceae
,
Serratia marcescens
,
Morganella morganii
,
Haemophilus influenzae
,
Moraxella catarrhalis
, and
Burkholderia cepacia
. BB-78484 was bactericidal against
E. coli
, achieving 3-log killing in 4 h at a concentration 4 times above the MIC, as would be predicted for an inhibitor of lipid A biosynthesis.
E. coli
mutants with decreased susceptibility to BB-78484 were selected. Analysis of these mutants revealed that resistance arose as a consequence of mutations in the
fabZ
or
lpxC
genes. These data confirm the antibacterial target of BB-78484 and BB-78485 and validate LpxC as a target for gram-negative selective antibacterials.
PCR-Based Identification of
MAT-1
and
MAT-2
in the
Gibberella fujikuroi
Species Complex
Authors: Steenkamp Emma T. , Wingfield Brenda D. , Coutinho Teresa A. , Zeller Kurt A. , Wingfield Michael J. , Marasas Walter F. O. , Leslie John F. 
Published: July 2002

ABSTRACT

All sexually fertile strains in the
Gibberella fujikuroi
species complex are heterothallic, with individual mating types conferred by the broadly conserved ascomycete idiomorphs
MAT-1
and
MAT-2
. We sequenced both alleles from all eight mating populations, developed a multiplex PCR technique to distinguish these idiomorphs, and tested it with representative strains from all eight biological species and 22 additional species or phylogenetic lineages from this species complex. In most cases, either an ∼800-bp fragment from
MAT-2
or an ∼200-bp fragment from
MAT-1
is amplified. The amplified fragments cosegregate with mating type, as defined by sexual cross-fertility, in a cross of
Fusarium moniliforme
(
Fusarium verticillioides
). Neither of the primer pairs amplify fragments from
Fusarium
species such as
Fusarium graminearum
,
Fusarium pseudograminearum
, and
Fusarium culmorum
, which have, or are expected to have,
Gibberella
sexual stages but are thought to be relatively distant from the species in the
G. fujikuroi
species complex. Our results suggest that
MAT
allele sequences are useful indicators of phylogenetic relatedness in these and other
Fusarium
species.
Development of a Vital Fluorescent Staining Method for Monitoring Bacterial Transport in Subsurface Environments
Authors: Fuller Mark E. , Streger Sheryl H. , Rothmel Randi K. , Mailloux Brian J. , Hall James A. , Onstott Tullis C. , Fredrickson James K. , Balkwill David L. , DeFlaun Mary F. 
Published: July 2002

ABSTRACT

Previous bacterial transport studies have utilized fluorophores which have been shown to adversely affect the physiology of stained cells. This research was undertaken to identify alternative fluorescent stains that do not adversely affect the transport or viability of bacteria. Initial work was performed with a groundwater isolate,
Comamonas
sp. strain DA001. Potential compounds were first screened to determine staining efficiencies and adverse side effects. 5-(And 6-)-carboxyfluorescein diacetate, succinimidyl ester (CFDA/SE) efficiently stained DA001 without causing undesirable effects on cell adhesion or viability. Members of many other gram-negative and gram-positive bacterial genera were also effectively stained with CFDA/SE. More than 95% of CFDA/SE-stained
Comamonas
sp. strain DA001 cells incubated in artificial groundwater (under no-growth conditions) remained fluorescent for at least 28 days as determined by epifluorescent microscopy and flow cytometry. No differences in the survival and culturability of CFDA/SE-stained and unstained DA001 cells in groundwater or saturated sediment microcosms were detected. The bright, yellow-green cells were readily distinguished from autofluorescing sediment particles by epifluorescence microscopy. A high throughput method using microplate spectrofluorometry was developed, which had a detection limit of mid-10
5
CFDA-stained cells/ml; the detection limit for flow cytometry was on the order of 1,000 cells/ml. The results of laboratory-scale bacterial transport experiments performed with intact sediment cores and nondividing DA001 cells revealed good agreement between the aqueous cell concentrations determined by the microplate assay and those determined by other enumeration methods. This research indicates that CFDA/SE is very efficient for labeling cells for bacterial transport experiments and that it may be useful for other microbial ecology research as well.
Natural Antibiotic Resistance of Bacteria Isolated from Larvae of the Oil Fly,
Helaeomyia petrolei
Authors: Kadavy Dana R. , Hornby Jacob M. , Haverkost Terry , Nickerson Kenneth W. 
Published: July 2002

ABSTRACT

Helaeomyia petrolei
(oil fly) larvae inhabit the asphalt seeps of Rancho La Brea in Los Angeles, Calif. The culturable microbial gut contents of larvae collected from the viscous oil were recently examined, and the majority (9 of 14) of the strains were identified as
Providencia
spp. Subsequently, 12 of the bacterial strains isolated were tested for their resistance or sensitivity to 23 commonly used antibiotics. All nine strains classified as
Providencia rettgeri
exhibited dramatic resistance to tetracycline, vancomycin, bacitracin, erythromycin, novobiocin, polymyxin, colistin, and nitrofurantoin. Eight of nine
Providencia
strains showed resistance to spectinomycin, six of nine showed resistance to chloramphenicol, and five of nine showed resistance to neomycin. All 12 isolates were sensitive to nalidixic acid, streptomycin, norfloxacin, aztreonam, cipericillin, pipericillin, and cefotaxime, and all but OF008 (
Morganella morganii
) were sensitive to ampicillin and cefoxitin. The oil fly bacteria were not resistant to multiple antibiotics due to an elevated mutation rate. For each bacterium, the number of resistant mutants per 10
8
cells was determined separately on rifampin, nalidixic acid, and spectinomycin. In each case, the average frequencies of resistant colonies were at least 50-fold lower than those established for known mutator strain ECOR 48. In addition, the oil fly bacteria do not appear to excrete antimicrobial agents. When tested, none of the oil fly bacteria produced detectable zones of inhibition on
Pseudomonas aeruginosa
,
Escherichia coli
,
Staphylococcus aureus
, or
Candida albicans
cultures. Furthermore, the resistance properties of oil fly bacteria extended to organic solvents as well as antibiotics. When pre-exposed to 20 μg of tetracycline per ml, seven of nine oil fly bacteria tolerated overlays of 100% cyclohexane, six of nine tolerated 10% xylene, benzene, or toluene (10:90 in cyclohexane), and three of nine (OF007, OF010, and OF011) tolerated overlays of 50% xylene–50% cyclohexane. The observed correlation between antibiotic resistance and organic solvent tolerance is likely explained by an active efflux pump that is maintained in oil fly bacteria by the constant selective pressure of La Brea's solvent-rich environment. We suggest that the oil fly bacteria and their genes for solvent tolerance may provide a microbial reservoir of antibiotic resistance genes.
Application of Siderotyping for Characterization of
Pseudomonas tolaasii
and “
Pseudomonas reactans
” Isolates Associated with Brown Blotch Disease of Cultivated Mushrooms
Authors: Munsch Patricia , Geoffroy Valerie A. , Alatossava Tapani , Meyer Jean-Marie 
Published: July 2002

ABSTRACT

Pyoverdine isoelectric focusing analysis and pyoverdine-mediated iron uptake were used as siderotyping methods to analyze a collection of 57 northern and central European isolates of
P. tolaasii
and “
P. reactans
.” The bacteria, isolated from cultivated
Agaricus bisporus
or
Pleurotus ostreatus
mushroom sporophores presenting brown blotch disease symptoms, were identified according to the white line test (W. C. Wong and T. F. Preece, J. Appl. Bacteriol. 47:401–407, 1979) and their pathogenicity towards
A. bisporus
and were grouped into siderovars according to the type of pyoverdine they produced. Seventeen
P. tolaasii
isolates were recognized, which divided into two siderovars, with the first one containing reference strains and isolates of various geographical origins while the second one contained Finnish isolates exclusively. The 40 “
P. reactans
” isolates divided into eight siderovars. Pyoverdine isoelectric focusing profiles and cross-uptake studies demonstrated an identity for some “
P. reactans
” isolates, with reference strains belonging to the
P. fluorescens
biovars II, III, or V. Thus, the easy and rapid methods of siderotyping proved to be reliable by supporting and strengthening previous taxonomical data. Moreover, two potentially novel pyoverdines characterizing one
P. tolaasii
siderovar and one “
P. reactans
” siderovar were found.
Occurrence of Antimicrobial Resistance in Fish-Pathogenic and Environmental Bacteria Associated with Four Danish Rainbow Trout Farms
Authors: Schmidt Anja S. , Bruun Morten S. , Dalsgaard Inger , Pedersen Karl , Larsen Jens L. 
Published: July 2002

ABSTRACT

Surveillance of bacterial susceptibility to five antimicrobial agents was performed during a 1-year period in and around four freshwater fish farms situated along a stream in western Denmark. Besides assessing the levels of antibiotic resistance among the culturable fraction of microorganisms in fish, water, and sediment samples, two major fish pathogens (88
Flavobacterium psychrophilum
isolates and 134
Yersinia ruckeri
isolates) and 313 motile
Aeromonas
isolates, representing a group of ubiquitous aquatic bacteria, were isolated from the same samples. MICs were obtained applying a standardized agar dilution method. A markedly decreased susceptibility of
F. psychrophilum
isolates to most antimicrobial agents presently available for use in Danish aquaculture was detected, while the collected
Y. ruckeri
isolates remained largely sensitive to all therapeutic substances. Comparing the inlet and outlet samples, the increase of the antibiotic-resistant proportions observed among the culturable microflora was more pronounced and statistically significant among the motile aeromonads. High levels of individual and multiple antimicrobial resistances were demonstrated within the collected flavobacteria and aeromonads, thus indicating a substantial impact of fish farming on several groups of bacteria associated with aquacultural environments.