bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activities of β-Lactams and Macrolides against
Helicobacter pylori
Authors: Hassan Ibrahim J. , Stark Roger M. , Greenman John , Millar Michael R. 
Published: October 2018

ABSTRACT

A continuous-culture system (chemostat) was used to study the activities of β-lactam antimicrobial agents, clarithromycin, and 14-OH-clarithromycin against slowly growing
Helicobacter pylori
NCTC 11637.
H. pylori
was grown to steady state before exposure to these antimicrobial agents at ×8 the MIC. The bactericidal actions of combinations of amoxicillin and clarithromycin were also studied. Viable counts (numbers of CFU per milliliter) were determined at 2-h intervals for 12 h and at 20 h after the addition of antibiotics. The effects of pH changes (6.5 to 7.4) on the activities of amoxicillin, clarithromycin, and the combination of these against
H. pylori
NCTC 11637 were also studied. Viable counts following exposure to ampicillin, cefixime, ceftazidime, cefuroxime, cefotaxime, azlocillin, and piperacillin at 20 h showed bacteriostatic activity. Imipenem, meropenem, amoxicillin, clarithromycin, and 14-OH-clarithromycin reduced the viable counts by 3 log
10
CFU/ml (≥99.9% killing). Imipenem was the most rapidly bactericidal against
H. pylori
NCTC 11637. Results of the pH experiments showed that amoxicillin was bactericidal at pHs 6.5 to 7.4. Clarithromycin was bactericidal at pH 7.0 to 7.4 but was bacteriostatic at pH 6.5. The combination of amoxicillin and clarithromycin was bactericidal at pHs 6.5 and 7.0. A batch culture (flask system) was also used to investigate 12 strains of
H. pylori
for their susceptibilities to β-lactams, clarithromycin, and/or 14-OH-clarithromycin in order to determine whether results from the chemostat model can be reproduced with batch cultures. Results of the chemostat time-kill kinetic study were reproducible in our batch culture flask system. The role of carbapenems in the eradication of
H. pylori
should be investigated.
Use of Microdilution Panels with and without β-Lactamase Inhibitors as a Phenotypic Test for β-Lactamase Production among
Escherichia coli
,
Klebsiella
spp.,
Enterobacter
spp.,
Citrobacter freundii
, and
Serratia marcescens
Authors: Thomson Kenneth S. , Sanders Christine C. , Moland Ellen Smith 
Published: October 2018

ABSTRACT

Over the past decade, a number of new β-lactamases have appeared in clinical isolates of
Enterobacteriaceae
that, unlike their predecessors, do not confer β-lactam resistance that is readily detected in routine antibiotic susceptibility tests. Because optimal methodologies are needed to detect these important new β-lactamases, a study was designed to evaluate the ability of a panel of various β-lactam antibiotics tested alone and in combination with β-lactamase inhibitors to discriminate between the production of extended-spectrum β-lactamases, AmpC β-lactamases, high levels of K1 β-lactamase, and other β-lactamases in 141 isolates of
Escherichia coli
,
Klebsiella pneumoniae
,
Klebsiella oxytoca
,
Enterobacter cloacae
,
Enterobacter aerogenes
,
Citrobacter freundii
, and
Serratia marcescens
possessing well-characterized β-lactamases. The microdilution panels studied contained aztreonam, cefpodoxime, ceftazidime, cefotaxime, and ceftriaxone, with and without 1, 2, and 4 μg of clavulanate per ml or 8 μg of sulbactam per ml and cefoxitin and cefotetan with and without 8 μg of sulbactam per ml. The results indicated that a minimum panel of five tests would provide maximum separation of extended-spectrum β-lactamase high AmpC, high K1, and other β-lactamase production in
Enterobacteriaceae
. These included cefpodoxime, cefpodoxime plus 4 μg of clavulanate per ml, ceftazidime, ceftriaxone, and ceftriaxone plus 8 μg of sulbactam per ml. Ceftriaxone plus 2 μg of clavulanate per ml could be substituted for cefpodoxime plus 4 μg of clavulanate per ml without altering the accuracy of the tests. This study indicated that tests with key β-lactam drugs, alone and in combination with β-lactamase inhibitors, could provide a convenient approach to the detection of a variety of β-lactamases in members of the family
Enterobacteriaceae.
Species Differences in the Proportion of Plasma Lipoprotein Lipid Carried by High-Density Lipoproteins Influence the Distribution of Free and Liposomal Nystatin in Human, Dog, and Rat Plasma
Authors: Ramaswamy Manisha , Wallace Thomas L. , Cossum Paul A. , Wasan Kishor M. 
Published: October 2018

ABSTRACT
The objective of this study was an interspecies comparison of free nystatin (NYS) and liposomal NYS (Nyotran) distribution in plasma. NYS and liposomal NYS at concentrations of 5, 10, and 20 μg of NYS/ml were incubated in human, dog, and rat plasma for 5, 60, and 180 min at 37°C. Following these incubations, plasma samples were separated into their high-density lipoprotein (HDL), triglyceride-rich lipoprotein, low-density lipoprotein, and lipoprotein-deficient plasma (LPDP) fractions by density-gradient ultracentrifugation, and each fraction was assayed for NYS by high-pressure liquid chromatography. Total plasma and lipoprotein cholesterol, triglyceride, and protein concentrations in each human, dog, or rat plasma sample were determined by enzymatic assays. When NYS and liposomal NYS were incubated in human, dog, or rat plasma, the majority of the NYS was recovered in the LPDP fraction. For the 5- and 60-min incubation times for all plasmas measured, a significantly greater percentage of NYS was recovered in the lipoprotein fraction (primarily HDL) following the incubation of liposomal NYS than following the incubation of NYS. There was a significant correlation between the lipoprotein lipid and protein profiles in human, dog, and rat plasmas and the distribution of NYS and liposomal NYS in plasma. In particular, differences in the proportion of plasma lipoprotein cholesterol, triglyceride, and apolar lipids (cholesteryl ester and triglycerides) carried by HDL influenced the distribution of NYS and liposomal NYS within plasmas of different species. These findings suggest that the distribution of NYS among plasma lipoproteins of different species is defined by the proportion of lipid carried by HDL, and this is possibly an important consideration when evaluating the pharmacokinetics, toxicities, and activities of these compounds following administration to different animal species.
Emergence in France of Multiple Clones of Clinical
Streptococcus pneumoniae
Isolates with High-Level Resistance to Amoxicillin
Authors: Doit Catherine , Loukil Chawki , Fitoussi Frederic , Geslin Pierre , Bingen Edouard 
Published: October 2018

ABSTRACT

The genetic relatedness of French isolates of
Streptococcus pneumoniae
highly resistant to amoxicillin (MIC, ≥4 μg/ml, equal to or exceeding those of penicillin) was investigated by molecular fingerprinting. The results suggest that high-level resistance to amoxicillin has emerged within preexisting penicillin-resistant clones.
Rifampin and Rifabutin Resistance Mechanism in
Helicobacter pylori
Authors: Heep Markus , Beck Daniela , Bayerdörffer Ekkehard , Lehn Norbert 
Published: October 2018

ABSTRACT

Eighty-one clinical isolates of
Helicobacter pylori
showed no resistance to rifampin (MIC range, 0.032 to 2 μg/ml; MIC at which 50% of isolates are inhibited [MIC
50
], 0.25 μg/ml). The MIC
50
of rifabutin was 0.008 μg/ml (
n
= 16). All resistant laboratory mutants of
H. pylori
ATCC 43504 showed amino acid exchanges in codons 524 to 545 or codon 585 of the
rpoB
gene, corresponding to the gene sequences from
Mycobacterium tuberculosis
and
Escherichia coli.
Pharmacokinetics and Inflammatory-Fluid Penetration of Moxifloxacin following Oral or Intravenous Administration
Authors: Wise Richard , Andrews Jennifer M. , Marshall Gill , Hartman Giles 
Published: October 2018

ABSTRACT
A single 400-mg oral or intravenous (i.v.) dose of moxifloxacin was given to each of eight healthy male volunteers, and 6 weeks later the dose was administered by the other route. The concentrations of the drug in plasma, cantharidin-induced inflammatory fluid, and urine were measured over the subsequent 24 h. The mean maximum concentrations observed in plasma were 4.98 μg/ml after oral dosing and 5.09 μg/ml after i.v. dosing. The mean maximum concentrations attained in the inflammatory fluid were 2.62 and 3.23 μg/ml, respectively. The mean elimination half-lives from plasma were 8.32 and 8.17 h, respectively. The overall penetration into the inflammatory fluid was 103.4 and 104.2%. Over 24 h 15% of the drug was recovered in the urine when administered by either route.
In Vitro Antifungal Susceptibilities of
Scopulariopsis
Isolates
Authors: Aguilar C. , Pujol I. , Guarro J. 
Published: October 2018

ABSTRACT

MICs and minimum fungicidal concentrations of amphotericin B, miconazole, itraconazole, ketoconazole, fluconazole, and flucytosine against 17 isolates of
Scopulariopsis
spp. were determined by a broth microdilution method. All the isolates were resistant to itraconazole, fluconazole, and flucytosine, and amphotericin B, miconazole, and ketoconazole MICs were low for only a few.
Identification and Analysis of the Balhimycin Biosynthetic Gene Cluster and Its Use for Manipulating Glycopeptide Biosynthesis in
Amycolatopsis mediterranei
DSM5908
Authors: Pelzer S. , Süßmuth R. , Heckmann D. , Recktenwald J. , Huber P. , Jung G. , Wohlleben W. 
Published: October 2018

ABSTRACT

Seven complete genes and one incomplete gene for the biosynthesis of the glycopeptide antibiotic balhimycin were isolated from the producer,
Amycolatopsis mediterranei
DSM5908, by a reverse-cloning approach and characterized. Using oligonucleotides derived from glycosyltransferase sequences, a 900-bp glycosyltransferase gene fragment was amplified and used to identify a DNA fragment of 9,882 bp. Of the identified open reading frames, three (
oxyA
to -
C
) showed significant sequence similarities to cytochrome P450 monooxygenases and one (
bhaA
) showed similarities to halogenase, and the genes
bgtfA
to -
C
showed similarities to glycosyltransferases. Glycopeptide biosynthetic mutants were created by gene inactivation experiments eliminating oxygenase and glycosyltransferase functions. Inactivation of the oxygenase gene(s) resulted in a balhimycin mutant (SP1-1) which was not able to synthesize an antibiotically active compound. Structural analysis by high-performance liquid chromatography–mass spectrometry, fragmentation studies, and amino acid analysis demonstrated that these oxygenases are involved in the coupling of the aromatic side chains of the unusual heptapeptide. Mutant strain HD1, created by inactivation of the glycosyltransferase gene
bgtfB
, produced at least four different compounds which were not glycosylated but still antibiotically active.
DNA Cleavage Activities of
Staphylococcus aureus
Gyrase and Topoisomerase IV Stimulated by Quinolones and 2-Pyridones
Authors: Saiki Anne Y. C. , Shen Linus L. , Chen Chih-Ming , Baranowski John , Lerner Claude G. 
Published: October 2018

ABSTRACT

We have cloned
Staphylococcus aureus
DNA gyrase and topoisomerase IV and expressed them in
Escherichia coli
as polyhistidine-tagged proteins to facilitate purification and eliminate contamination by host enzymes. The enzyme preparations had specific activities similar to previously reported values. Potassium glutamate (K-Glu) stimulated the drug-induced DNA cleavage activity and was optimal between 100 and 200 mM for gyrase and peaked at 100 mM for topoisomerase IV. Higher concentrations of K-Glu inhibited the cleavage activities of both enzymes. Using a common buffer system containing 100 mM K-Glu, we tested the enzyme-mediated DNA cleavage activities of both gyrase and topoisomerase IV with oxolinic acid, norfloxacin, ciprofloxacin, trovafloxacin, clinafloxacin, and the 2-pyridone ABT-719. As expected, all drugs tested demonstrated greater potency against topoisomerase IV than against gyrase. In addition, cleavage activity was found to correlate well with antibacterial activity.
Topoisomerase Sequences of Coagulase-Negative Staphylococcal Isolates Resistant to Ciprofloxacin or Trovafloxacin
Authors: Dubin Donald T. , Fitzgibbon Joseph E. , Nahvi Massoumeh D. , John Joseph F. 
Published: October 2018

ABSTRACT

Coagulase-negative staphylococcal isolates (
n
= 188) were screened for susceptibility to oxacillin, ciprofloxacin, and trovafloxacin, a new fluoroquinolone. At an oxacillin concentration of ≥4 μg/ml, 43% were methicillin resistant; of these, 70% were ciprofloxacin resistant (MIC, ≥4 μg/ml). Of the methicillin-resistant, ciprofloxacin-resistant isolates, 46% were susceptible to ≤2 μg of trovafloxacin per ml and 32% were susceptible to ≤1 μg of trovafloxacin per ml. Sixteen isolates, including twelve that expressed fluoroquinolone resistance, were chosen for detailed analysis. Identification of species by rRNA sequencing revealed a preponderance of
Staphylococcus haemolyticus
and
S. hominis
among fluoroquinolone-resistant strains. Segments of genes (
gyrA
and
grlA
) encoding DNA gyrase and DNA topoisomerase IV were sequenced. Considerable interspecies variation was noted, mainly involving noncoding nucleotide changes. Intraspecies variation consisted of coding changes associated with fluoroquinolone resistance. As for
S. aureus
, ciprofloxacin resistance (MIC, ≥8 μg/ml) and increased trovafloxacin MICs (0.25 to 2 μg/ml) could be conferred by the combined presence of single mutations in each
gyrA
and
grlA
gene. Trovafloxacin MICs of ≥8 μg/ml also occurred, but these required an additional mutation in
grlA
.
Multiple Mechanisms of Action for Inhibitors of Histidine Protein Kinases from Bacterial Two-Component Systems
Authors: Hilliard Jamese J. , Goldschmidt Raul M. , Licata Lisa , Baum Ellen Z. , Bush Karen 
Published: October 2018

ABSTRACT

Many pathogenic bacteria utilize two-component systems consisting of a histidine protein kinase (HPK) and a response regulator (RR) for signal transduction. During the search for novel inhibitors, several chemical series, including benzoxazines, benzimidazoles, bis-phenols, cyclohexenes, trityls, and salicylanilides, were identified that inhibited the purified HPK-RR pairs KinA-Spo0F and NR
II
-NR
I
, with 50% inhibitory concentrations (IC
50
s) ranging from 1.9 to >500 μM and MICs ranging from 0.5 to >16 μg/ml for gram-positive bacteria. However, additional observations suggested that mechanisms other than HPK inhibition might contribute to antibacterial activity. In the present work, representative compounds from the six different series of inhibitors were analyzed for their effects on membrane integrity and macromolecular synthesis. At 4× MIC, 17 of 24 compounds compromised the integrity of the bacterial cell membrane within 10 min, as measured by uptake of propidium iodide. In this set, compounds with lower IC
50
s tended to cause greater membrane disruption. Eleven of 12 compounds inhibited cellular incorporation of radiolabeled thymidine and uridine >97% in 5 min and amino acids >80% in 15 min. The HPK inhibitor that allowed >25% precursor incorporation had no measurable MIC (>16 μg/ml). Fifteen of 24 compounds also caused hemolysis of equine erythrocytes. Thus, the antibacterial HPK inhibitors caused a rapid decrease in cellular incorporation of RNA, DNA, and protein precursors, possibly as a result of the concomitant disruption of the cytoplasmic membrane. Bacterial killing by these HPK inhibitors may therefore be due to multiple mechanisms, independent of HPK inhibition.
Activities of Sordarins in Murine Histoplasmosis
Authors: Graybill John R. , Najvar Laura , Fothergill Annette , Bocanegra Rosie , de las Heras Federico Gomez 
Published: October 2018

ABSTRACT

Sordarins are new antifungals which inhibit fungal protein synthesis by blocking elongation factor 2. Three compounds were evaluated in a murine model of histoplasmosis. Immune-competent mice were infected intravenously with 10
6
to 10
8
CFU of
Histoplasma capsulatum
yeast cells. Mice were treated either orally with sordarins or fluconazole from day 2 through 8 after infection or intraperitoneally with amphotericin B during the same period. Protection was measured by increased rates of survival for 30 days after infection or reduction of lung or kidney tissue counts 9 days after infection. All three of the antifungal drugs tested were protective compared with controls. Sordarins were effective at doses as low as 2 mg/kg of body weight/day. This novel class of drugs compared favorably with amphotericin B and fluconazole for the treatment of histoplasmosis.
Class C β-Lactamases Operate at the Diffusion Limit for Turnover of Their Preferred Cephalosporin Substrates
Authors: Bulychev Alexey , Mobashery Shahriar 
Published: October 2018

ABSTRACT

It has been suggested that class C β-lactamases have evolved to carry out a metabolic reaction other than hydrolysis of β-lactam antibiotics. It is demonstrated in the present study that the class C β-lactamase from
Enterobacter cloacae
P99 has reached the diffusion limit in its ability to hydrolyze its preferred cephalosporin substrates. The increase in the solution viscosity by addition of a microviscogen (sucrose) caused the decline in the parameter
k
cat
/

K
m

for hydrolysis of cephaloridine and cephalosporin C (approximately 2.5-fold at a relative viscosity of 2.9). A similar increase in viscosity has no effect on the turnover rate of the poorer substrates cefepime and penicillin G. Addition of a macroviscogen (polyethylene glycol) to the reaction mixture did not change the rate of turnover for any of the substrates tested because in this case the viscogen would not interfere with the motion of small molecules, as was expected. Therefore, it would appear that the driving force behind the evolution of this class C β-lactamase and, in principle, other enzymes of this class is indeed the functional reaction of this enzyme as a drug resistance factor.
Effect of Fluoroquinolone Concentration on Selection of Resistant Mutants of
Mycobacterium bovis
BCG and
Staphylococcus aureus
Authors: Dong Yuzhi , Zhao Xilin , Domagala John , Drlica Karl 
Published: October 2018

ABSTRACT

When
Mycobacterium bovis
BCG and
Staphylococcus aureus
were plated on agar containing increasing concentrations of fluoroquinolone, colony numbers exhibited a sharp drop, followed by a plateau and a second sharp drop. The plateau region correlated with the presence of first-step resistant mutants. Mutants were not recovered at concentrations above those required for the second sharp drop, thereby defining a mutant prevention concentration (MPC). A C-8-methoxy group lowered the MPC for an
N
-1-cyclopropyl fluoroquinolone.
Sequence of the MIR-1 β-Lactamase Gene
Authors: Jacoby George A. , Tran John 
Published: October 2018

ABSTRACT

The complete nucleotide sequence of the plasmid-mediated MIR-1 β-lactamase gene confirms its relationship to chromosomally located
ampC
genes of
Enterobacter cloacae
.
bla
MIR-1
is not part of a typical gene cassette but does lie near an element that could be involved in its capture on a plasmid.
pncA
Mutations in Pyrazinamide-Resistant
Mycobacterium tuberculosis
Isolates from Northwestern Russia
Authors: Marttila Harri J. , Marjamäki Merja , Vyshnevskaya Elena , Vyshnevskiy Boris I. , Otten Tatjana F. , Vasilyef Alexandr V. , Viljanen Matti K. 
Published: October 2018

ABSTRACT

Thirty-six pyrazinamide-resistant and eight pyrazinamide-susceptible
Mycobacterium tuberculosis
isolates from Russia were analyzed for their
pncA
mutations. Thirty-one (86.1%) of the resistant isolates had a mutation either in
pncA
or upstream of the gene. Twenty of the 23 different mutations found in this study had not been described earlier.
pncA
genotype correlated well with pyrazinamidase activity and BACTEC 460 susceptibility test results.
Rapid Detection, by PCR and Reverse Hybridization, of Mutations in the
Helicobacter pylori
23S rRNA Gene, Associated with Macrolide Resistance
Authors: van Doorn Leen-Jan , Debets-Ossenkopp Yvette J. , Marais Armelle , Sanna Ricardo , Mégraud Francis , Kusters Johannes G. , Quint Wim G. V. 
Published: October 2018

ABSTRACT

A PCR-based reverse hybridization system (research prototype kit INNO-LiPA for
H. pylori
resistance) was developed and evaluated for simultaneous detection of 23S ribosomal DNA point mutations, associated with macrolide resistance in
Helicobacter pylori
. Fifty-seven
H. pylori
strains (51 natural, 6 laboratory-derived artificial, 52 resistant, and 5 susceptible strains) were tested by PCR-LiPA (detecting mutations A2115→G, G2141→A, A2142→G, A2142→C, A2143→G, A2143→C, and A2143→T), DNA sequencing, restriction fragment length polymorphism, and/or hybridization to oligonucleotide probes. Results were highly concordant, but PCR-LiPA appears to be more sensitive for the simultaneous detection of multiple mutants.
Sensitivity of Amoxicillin-Resistant
Helicobacter pylori
to Other Penicillins
Authors: Dore Maria P. , Graham David Y. , Sepulveda Antonia R. , Realdi Giuseppe , Osato Michael S. 
Published: October 2018

ABSTRACT

The sensitivities to penicillins and to a penicillin and β-lactamase inhibitor combination agent were determined for
Helicobacter pylori
strains that were sensitive, moderately resistant, or highly resistant to amoxicillin. All strains were resistant to nafcillin and oxacillin. Moderately resistant strains showed an intermediate zone of inhibition to ticarcillin, mezlocillin, piperacillin, and amoxicillin-clavulanic acid. High-level resistance was associated with the smallest zone size for all penicillins tested.
Activities of Trovafloxacin Compared with Those of Other Fluoroquinolones against Purified Topoisomerases and
gyrA
and
grlA
Mutants of
Staphylococcus aureus
Authors: Gootz Thomas D. , Zaniewski Richard P. , Haskell Suzanne L. , Kaczmarek Frank S. , Maurice Alison E. 
Published: October 2018

ABSTRACT

Frequencies of mutation to resistance with trovafloxacin and four other quinolones were determined with quinolone-susceptible
Staphylococcus aureus
RN4220 by a direct plating method. First-step mutants were selected less frequently with trovafloxacin (1.1 × 10
−10
at 2 to 4× the MIC) than with levofloxacin or ciprofloxacin (3.0 × 10
−7
to 3.0 × 10
−8
at 2 to 4× the MIC). Mutants with a change in GrlA (Ser80→Phe or Tyr) were most commonly selected with trovafloxacin, ciprofloxacin, levofloxacin, or pefloxacin. First-step mutants were difficult to select with sparfloxacin; however, second-step mutants with mutations in
gyrA
were easily selected when a preexisting mutation in
grlA
was present. Against 29
S. aureus
clinical isolates with known mutations in
gyrA
and/or
grlA
, trovafloxacin was the most active quinolone tested (MIC at which 50% of isolates are inhibited [MIC
50
] and MIC
90
, 1 and 4 μg/ml, respectively); in comparison, MIC
50
s and MIC
90
s were 32 and 128, 16 and 32, 8 and 32, and 128 and 256 μg/ml for ciprofloxacin, sparfloxacin, levofloxacin, and pefloxacin, respectively. Strains with a mutation in
grlA
only were generally susceptible to all of the quinolones tested. For mutants with changes in both
grlA
and
gyrA
MICs were higher and were generally above the susceptibility breakpoint for ciprofloxacin, sparfloxacin, levofloxacin, and pefloxacin. Addition of reserpine (20 μg/ml) lowered the MICs only of ciprofloxacin fourfold or more for 18 of 29 clinical strains. Topoisomerase IV and DNA gyrase genes were cloned from
S. aureus
RN4220 and from two mutants with changes in GrlA (Ser80→Phe and Glu84→Lys). The enzymes were overexpressed in
Escherichia coli
GI724, purified, and used in DNA catalytic and cleavage assays that measured the relative potency of each quinolone. Trovafloxacin was at least five times more potent than ciprofloxacin, sparfloxacin, levofloxacin, or pefloxacin in stimulating topoisomerase IV-mediated DNA cleavage. While all of the quinolones were less potent in cleavage assays with the altered topoisomerase IV, trovafloxacin retained its greater potency relative to those of the other quinolones tested. The greater intrinsic potency of trovafloxacin against the lethal topoisomerase IV target in
S. aureus
contributes to its improved potency against clinical strains of
S. aureus
that are resistant to other quinolones.