bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Disruption of a Gene Encoding an Autolysin of
Enterococcus faecalis
OG1RF
Authors: Qin Xiang , Singh Kavindra V. , Xu Yi , Weinstock George M. , Murray Barbara E. 
Published: October 2018

ABSTRACT

A mutant (TX5127) of
Enterococcus faecalis
OG1RF was generated by disruption mutagenesis of a previously described autolysin gene. TX5127 formed longer chains (2 to 10 cells per chain) than wild-type OG1RF (mainly single cells) during growth in broth even though it had a growth rate similar to that of the parental strain as measured by turbidity and cell count. Autolysin activity, as defined by the ability to lyse heat-killed
Micrococcus lysodeikticus
cells, was absent in TX5127, while this activity was easily detectable in OG1RF. However, disruption of this autolysin gene did not block the ability of TX5127 to hydrolyze
E. faecalis
cell walls compared to that of OG1RF. The autolysis rate of cells of TX5127 in 10 mM sodium phosphate buffer (pH 6.8) was slower than that of wild-type OG1RF. TX5127 also showed a decreased rate of lysis in the presence of penicillin, as measured by changes in the turbidity of the culture during 24 h of incubation at 37°C and a slightly decreased effect of penicillin as measured by time-kill curves. The virulence of TX5127 was similar to that of OG1RF in the mouse peritonitis model, indicating that the autolysin of
E. faecalis
is not important for infection in this model.
Diversity of Structures Carrying the High-Level Gentamicin Resistance Gene
(aac6-aph2)
in
Enterococcus faecalis
Strains Isolated in France
Authors: Casetta Anne , Hoï Annie Buu , de Cespédès Gilda , Horaud Thea 
Published: October 2018

ABSTRACT

Of 24 high-level gentamicin-resistant clinical isolates of
Enterococcus faecalis
, 20 carried gentamicin resistance (Gm
r
) plasmids. The plasmids ranged from 65.0 to 80.0 kb in size. Three of these plasmids were nonconjugative, and 17 transferred by conjugation to an
E. faecalis
recipient at low frequency (10
−5
to 10
−6
transconjugants per donor). The remaining four strains had a nonconjugative chromosomal Gm
r
determinant. On the basis of restriction enzyme and DNA-DNA hybridization profiles, Tn
4001
-like α elements were located on the chromosome and three types of Tn
4001
-truncated structures, I, II, and III, were found to be carried by the Gm
r
plasmids. Structure I lacked IS
256
in the right-hand flanking extremity of Tn
4001
. Structure II was the same as structure I except that it also had a partial deletion of IS
256
in the left-hand flanking extremity of Tn
4001
. Structure III lacked both the right- and left-hand flanking extremities of Tn
4001
. One of the wild-type strains carried the Gm
r
determinant both on the chromosome, as a Tn
4001
-like α element, and on a conjugative plasmid, as a Tn
4001
-truncated type I structure.
Antifungal Efficacy, Safety, and Single-Dose Pharmacokinetics of LY303366, a Novel Echinocandin B, in Experimental Pulmonary Aspergillosis in Persistently Neutropenic Rabbits
Authors: Petraitis Vidmantas , Petraitiene Ruta , Groll Andreas H. , Bell Aaron , Callender Diana P. , Sein Tin , Schaufele Robert L. , McMillian Carl L. , Bacher John , Walsh Thomas J. 
Published: October 2018

ABSTRACT

LY303366 is a novel semisynthetic derivative of echinocandin B and a potent inhibitor of fungal (1,3)-β-
d
-glucan synthase. The antifungal efficacy and safety of LY303366 were investigated in treatment and prophylaxis of primary pulmonary aspergillosis due to
Aspergillus fumigatus
in persistently neutropenic rabbits. Treatment study groups were either not treated (controls) or treated with amphotericin B (AmB) at 1 mg/kg of body weight per day or with LY303366 at 1, 5, 10, and 20 mg/kg/day. In rabbits treated with LY303366, there was a significant improvement in survival and a reduction in organism-mediated pulmonary injury measured by the number of infarcts, total lung weight, and ultrafast computerized tomography scan pulmonary lesion score. Rabbits receiving prophylactic LY303366 also demonstrated significant improvement in survival and reduction in organism-mediated pulmonary injury. AmB and LY303366 had comparable therapeutic efficacies by all parameters with the exception of reduction in tissue burden of
A. fumigatus
, where AmB was superior to LY303366. LY303366 demonstrated a dose-dependent effect on hyphal injury with progressive truncation, swelling, and vacuolization. LY303366 administered in single doses of 1, 5, 10, and 20 mg/kg demonstrated dose-proportional increases in the maximum concentration of drug in plasma and the area under the concentration-time curve from 0 to 72 h with no changes in plasma drug clearance. The 1-mg/kg dosage maintained plasma drug levels above the MIC for 18 h, and dosages of ≥5 mg/kg maintained plasma drug levels above the MIC for the entire 24-h dosing interval. There was no significant elevation of the concentrations of hepatic transaminases or creatinine in serum in LY303366-treated rabbits. In summary, LY303366 improved survival and decreased pulmonary injury with no apparent toxicity in the treatment and prevention of invasive pulmonary aspergillosis in persistently neutropenic rabbits.
Specific Activities of Dolastatin 10 and Peptide Derivatives against
Cryptococcus neoformans
Authors: Pettit Robin K. , Pettit George R. , Hazen Kevin C. 
Published: October 2018

ABSTRACT

The biosynthetic peptide dolastatin 10 is currently in phase I and II cancer clinical trials. We evaluated the antifungal spectrum of dolastatin 10 and four structural modifications. In broth macrodilution assays, the peptides were fungicidal for American Type Culture Collection strains and clinical isolates (including fluconazole-resistant strains) of
Cryptococcus neoformans
but no other yeasts or filamentous fungi examined. Specificity for
C. neoformans
was also demonstrated in the solid-phase disk diffusion assay, and fungicidal activity was confirmed in time-kill experiments. For a methyl ester modification, the MICs at which 50 and 90% of 19 clinical isolates were inhibited (MIC
50
and MIC
90
, respectively) were 0.195 and 0.39 μg/ml, respectively. The MFC
50
(50% minimum fungicidal concentration) for this peptide was 0.39 μg/ml, and the MFC
90
was 0.78 μg/ml. MICs and MFCs were identical or lower in the presence of human serum but increased with lowered pH. These peptides should be pursued as potential chemotherapeutics for
C. neoformans
, a leading cause of infection and mortality in immunocompromised patients.
Purification and Characterization of Virginiamycin M
1
Reductase from
Streptomyces virginiae
Authors: Suzuki Naoyoshi , Lee Chang-Kwon , Nihira Takuya , Yamada Yasuhiro 
Published: October 2018

ABSTRACT

Virginiamycin M
1
(VM
1
), produced by
Streptomyces virginiae
, is a polyunsaturated macrocyclic lactone antibiotic belonging to the virginiamycin A group.
S. virginiae
possesses an activity which stereospecifically reduces a 16-carbonyl group of VM
1
, resulting in antibiotically inactive 16
R
-dihydroVM
1
. The corresponding VM
1
reductase was purified to homogeneity from crude extracts of
S. virginiae
in five steps, with 5,650-fold purification and 23% overall yield. The N-terminal amino acid sequence was determined to be MAIKLVIA. The purified enzyme showed an apparent
M
r
of 73,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an
M
r
of 280,000 by native molecular sieve high-performance liquid chromatography, indicating the tetrameric nature of the native enzyme. NADPH served as a coenzyme for the reduction, with a

K
m

value of 0.13 mM, but NADH did not support the reaction, even at a concentration of 5 mM, indicating the NADPH-specific nature of the enzyme. The

K
m

for VM
1
was determined to be 1.5 mM in the presence of 2 mM NADPH. In the reverse reaction, only 16
R
-dihydroVM
1
, not the 16
S
-epimer, served as a substrate, with a less than 0.1% overall reaction rate compared to that of the forward reaction, confirming that the VM
1
reductase participates solely in VM
1
inactivation in vivo.
Pulsed-Exposure and Postantibiotic Leukocyte Enhancement Effects of Amikacin, Clarithromycin, Clofazimine, and Rifampin against Intracellular
Mycobacterium avium
Authors: Horgen Lionel , Jerome Arnaud , Rastogi Nalin 
Published: October 2018

ABSTRACT

We investigated the postantibiotic effects (PAEs) of four agents against
Mycobacterium avium
in a human macrophage model under two different experimental conditions. For postantibiotic leukocyte enhancement (PALE), bacteria were exposed to antibiotics prior to their phagocytosis, whereas for pulsed exposure (PE), antibiotics were added after phagocytosis. In both cases, the drugs were used at their peak concentrations in serum (
C
max
) for 2 h. The results showed two different patterns: one for the drug for which results under PE and PALE test conditions did not significantly differ (amikacin) and one for drugs for which PAE values were significantly higher under PE test conditions (clarithromycin, clofazimine, and rifampin). These data suggest that even a brief exposure of
M. avium
to peak concentrations of certain drugs in serum may result in prolonged and persistent suppression of bacterial growth inside human macrophages.
Comparison of Ceftriaxone, Amikacin, and Ciprofloxacin in Treatment of Experimental
Yersinia enterocolitica
O9 Infection in Mice
Authors: Jiménez-Valera Maria , Gonzalez-Torres Concepción , Moreno Encarnación , Ruiz-Bravo Alfonso 
Published: October 2018

ABSTRACT

Ceftriaxone and ciprofloxacin were effective in the treatment of
Yersinia enterocolitica
O9 intestinal infection in mice. Amikacin was less effective. The impact of these drugs on indigenous bacteria from the intestinal microbiota was studied.
Multiple Molecular Mechanisms Contribute to a Stepwise Development of Fluconazole Resistance in Clinical
Candida albicans
Strains
Authors: Franz Renate , Kelly Steven L. , Lamb David C. , Kelly Diane E. , Ruhnke Markus , Morschhäuser Joachim 
Published: October 2018

ABSTRACT

From each of two AIDS patients with oropharyngeal candidiasis, five
Candida albicans
isolates from recurrent episodes of infection which became gradually resistant against fluconazole during antimycotic treatment were analyzed for molecular changes responsible for drug resistance. In both patients, a single
C. albicans
strain was responsible for the recurrent infections, but the
CARE-2
fingerprint pattern of the isolates exhibited minor genetic alterations, indicating that microevolution of the strains took place during fluconazole therapy. In the isolates from patient 1, enhanced mRNA levels of the
MDR1
gene, encoding a multiple drug resistance protein from the superfamily of major facilitators, and constitutive high expression of the
ERG11
gene, coding for the drug target enzyme sterol 14α-demethylase, correlated with a stepwise development of fluconazole resistance. The resistant strains exhibited reduced accumulation of fluconazole and, for the last in the series, a slight increase in drug needed to inhibit sterol 14α-demethylation in vitro. In the isolates from patient 2, increased
MDR1
mRNA levels and the change from heterozygosity to homozygosity for a mutant form of the
ERG11
gene correlated with continuously decreased drug susceptibility. In this series, reduced drug accumulation and increased resistance in the target enzyme activity, sterol 14α-demethylase, were observed. These results demonstrate that different molecular mechanisms contribute to a gradual development of fluconazole resistance in
C. albicans.
Inhibition of Duck Hepatitis B Virus Replication by 9-(2-Phosphonylmethoxyethyl)adenine, an Acyclic Phosphonate Nucleoside Analogue
Authors: Nicoll A. J. , Colledge D. L. , Toole J. J. , Angus P. W. , Smallwood R. A. , Locarnini S. A. 
Published: October 2018

ABSTRACT
The use of regimens that use nucleoside analogues for the treatment of chronic hepatitis B virus infection is often limited because of their high relapse rates. This is thought to be due to the persistence of virus in nonhepatocyte reservoirs and/or the viral covalently closed circular (CCC) DNA species in the nucleus of infected hepatocytes. We have evaluated the novel nucleoside analogue 9-(2-phosphonylmethoxyethyl)adenine (PMEA) in the duck model of hepatitis B. Eight Pekin-Aylesbury ducks congenitally infected with the duck hepatitis B virus (DHBV) were treated with PMEA at a dosage of 15 mg/kg of body weight/day via the intraperitoneal route for 4 weeks. At the end of the treatment period, four animals were killed and the remainder were monitored for a further 4-week drug-free period before analysis. The results were compared with those for eight age-matched, untreated controls. The levels of viremia, the total intrahepatic DHBV load, and CCC DNA, viral RNA, and protein levels were measured by Southern hybridization, Northern hybridization, and immunoblotting of the appropriate specimen, respectively. Viral proteins and DNA were also measured by immunohistochemistry (IHC) and in situ hybridization (ISH) of sections of liver and pancreatic tissue. PMEA treatment reduced the viremia to undetectable levels, while the total viral DNA load in the liver was reduced by 95% compared to the control level. Viral RNA and protein levels decreased by approximately 30%. ISH and IHC confirmed the PMEA-related intrahepatic changes and established that the amount of virus in bile duct epithelial cells (BDEC) was reduced by 70% during therapy. During the follow-up period all parameters of active virological replication returned to those for the age-matched controls. PMEA had no significant effect upon the number of virus-infected islet or acinar cells in the pancreas. PMEA at a dosage of 15 mg/kg/day has potent activity against DHBV found within hepatocytes and BDEC and inhibits DHBV replication in BDEC.
Inhibition of Human Hepatitis B Virus Replication by AT-61, a Phenylpropenamide Derivative, Alone and in Combination with (−)β-
l
-2′,3′-Dideoxy-3′-Thiacytidine
Authors: King Robert W. , Ladner Stephanie K. , Miller Thomas J. , Zaifert Katie , Perni Robert B. , Conway Sameul C. , Otto Michael J. 
Published: October 2018

ABSTRACT

AT-61, a member of a novel class of phenylpropenamide derivatives, was found to be a highly selective and potent inhibitor of human hepatitis B virus (HBV) replication in four different human hepatoblastoma cell lines which support the replication of HBV (i.e., HepAD38, HepAD79, 2.2.15, and transiently transfected HepG2 cells). This compound was equally effective at inhibiting both the formation of intracellular immature core particles and the release of extracellular virions, with 50% effective concentrations ranging from 0.6 to 5.7 μM. AT-61 (27 μM) was able to reduce the amount of HBV covalently closed circular DNA found in the nuclei of HepAD38 cells by >99%. AT-61 at concentrations of >27 μM had little effect on the amount of viral RNA found within the cytoplasms of induced HepAD38 cells but reduced the number of immature virions which contained pregenomic RNA by >99%. The potency of AT-61 was not affected by one of the mutations responsible for (−)-β-
l
-2′,3′-dideoxy-3′ thiacytidine (3TC) resistance in HBV, and AT-61 acted synergistic with 3TC to inhibit HBV replication. AT-61 (81 μM) was not cytotoxic or antiproliferative to several cell lines and had no antiviral effect on woodchuck or duck HBV, human immunodeficiency virus type 1, herpes simplex virus type 1, vesicular stomatitis virus, or Newcastle disease virus. Therefore, we concluded that the antiviral activity of AT-61 is specific for HBV replication and most likely occurs at one of the steps between the synthesis of viral RNA and the packaging of pregenomic RNA into immature core particles.
In Vitro Susceptibilities of
Candida
Bloodstream Isolates to the New Triazole Antifungal Agents BMS-207147, Sch 56592, and Voriconazole
Authors: Pfaller M. A. , Messer S. A. , Hollis R. J. , Jones R. N. , Doern G. V. , Brandt M. E. , Hajjeh R. A. 
Published: October 2018

ABSTRACT

BMS-207147, Sch 56592, and voriconazole are three new investigational triazoles with broad-spectrum antifungal activity. The in vitro activities of these three agents were compared with those of itraconazole and fluconazole against 1,300 bloodstream isolates of
Candida
species obtained from over 50 different medical centers in the United States. The MICs of all of the antifungal drugs were determined by broth microdilution tests performed according to the National Committee for Clinical Laboratory Standards method using RPMI 1640 as a test medium. BMS-207147, Sch 56592, and voriconazole were all quite active against all
Candida
sp. isolates (MICs for 90% of the isolates tested [MIC
90
s], 0.5, 1.0, and 0.5 μg/ml, respectively).
Candida albicans
was the most susceptible species (MIC
90
s, 0.03, 0.06, and 0.06 μg/ml, respectively), and
C. glabrata
was the least susceptible (MIC
90
s, 4.0, 4.0, and 2.0 μg/ml, respectively). BMS-207147, Sch 56592, and voriconazole were all more active than itraconazole and fluconazole against
C. albicans
,
C. parapsilosis
,
C. tropicalis
, and
C. krusei
. There existed a clear rank order of in vitro activity of the five azoles examined in this study when they were tested versus
C. glabrata
: voriconazole > BMS-207147 = Sch 56592 = itraconazole > fluconazole (MIC
90
s, 2.0, 4.0, 4.0, 4.0, and 64 μg/ml, respectively). For isolates of
Candida
spp. with decreased susceptibility to both itraconazole and fluconazole, the MICs of BMS-207147, Sch 56592, and voriconazole were also elevated. These results suggest that BMS-207147, Sch 56592, and voriconazole all possess promising antifungal activity and that further in vitro and in vivo investigations are warranted to establish the clinical value of this improved potency.
Induction of Resistance to Azole Drugs in
Trypanosoma cruzi
Authors: Buckner Frederick S. , Wilson Aaron J. , White Theodore C. , Van Voorhis Wesley C. 
Published: October 2018

ABSTRACT

Trypanosoma cruzi
is the protozoan parasite that causes Chagas’ disease, a frequently fatal illness affecting the heart and gastrointestinal systems. An estimated 16 million to 18 million people in Latin America and 50,000 to 100,000 people in the United States are infected with this pathogen. Treatment options for
T. cruzi
infections are suboptimal due to the toxicities and limited effectiveness of the available drugs. Azole antimicrobial agents have been discovered to have antitrypanosomal activity by inhibition of ergosterol synthesis. The triazole itraconazole was recently shown to produce a parasitologic cure rate of 53% in chronically infected patients (W. Apt et al., Am. J. Trop. Med. Hyg. 59:133–138, 1998), a result which may lead to more use of this family of drugs for the treatment of
T. cruzi
infections. In the experiments reported on here, resistance to azoles was induced in vitro by serial passage of mammalian-stage parasites in the presence of fluconazole for 4 months. These parasites were cross resistant to the other azoles, ketoconazole, miconazole, and itraconazole. They remained susceptible to benznidazole and amphotericin B. The azole-resistant phenotype was stable for more than 2 months of in vitro serial passage without fluconazole. In addition, the parasites resisted treatment in mice receiving ketoconazole. The rapid development of azole resistance in
T. cruzi
in vitro suggests that resistance to azole drugs has the potential to occur in patients and may pose an impediment to the progress being made in the treatment of
T. cruzi
infection.
Ceftazidime-Resistant
Enterobacteriaceae
Isolates from Three Polish Hospitals: Identification of Three Novel TEM- and SHV-5-Type Extended-Spectrum β-Lactamases
Authors: Gniadkowski Marek , Schneider Ines , Jungwirth Renate , Hryniewicz Waleria , Bauernfeind Adolf 
Published: October 2018

ABSTRACT

Twelve ceftazidime-resistant isolates of the family
Enterobacteriaceae
(11
Klebsiella pneumoniae
isolates and 1
Escherichia coli
isolate) were collected in 1995 from three Polish hospitals located in different cities. All were identified as producers of extended-spectrum β-lactamases (ESBLs). Detailed analysis of their β-lactamase contents revealed that six of them expressed SHV-5-like ESBLs. The remaining six were found to produce three different TEM enzymes, each characterized by a pI value of 6.0 and specified by new combinations of amino acid substitutions. The amino acid substitutions compared to the TEM-1 β-lactamase sequence were Gly238Ser, Glu240Lys, and Thr265Met for TEM-47; Leu21Phe, Gly238Ser, Glu240Lys, and Thr265Met for TEM-48; and Leu21Phe, Gly238Ser, Glu240Lys, Thr265Met, and Ser268Gly for TEM-49. The new TEM β-lactamases, TEM-47, TEM-48, and TEM-49, belong to a subfamily of TEM-2-related enzymes. Genes coding for TEM-47 and TEM-49 could have originated from the TEM-48-encoding sequence by various single genetic events. The new TEM derivatives probably document the already advanced microevolution of ESBLs ongoing in Polish hospitals, in a majority of which no monitoring of ESBL producers was performed before 1996.
Anti-Human Immunodeficiency Virus Activity and Cellular Metabolism of a Potential Prodrug of the Acyclic Nucleoside Phosphonate 9-
R
-(2-Phosphonomethoxypropyl)adenine (PMPA), Bis(isopropyloxymethylcarbonyl)PMPA
Authors: Robbins Brian L. , Srinivas Ranga V. , Kim Choung , Bischofberger Norbert , Fridland Arnold 
Published: October 2018

ABSTRACT

Bis(isopropyloxymethylcarbonyl) 9-
R
-(2-phosphonomethoxypropyl)adenine [bis(POC)PMPA] has been identified as a novel prodrug of PMPA. The anti-human immunodeficiency virus activity of bis(POC)PMPA was >100-fold greater than that of PMPA in both an established T-cell line and primary peripheral blood lymphocytes. This improved efficacy was shown to be due to a rapid intracellular uptake of the prodrug resulting in an increased intracellular accumulation of PMPA diphosphate (PMPApp), the pharmacologically active metabolite. PMPApp levels in bis(POC)PMPA-treated cells exceeded by >1,000-fold the levels seen in cells treated with unmodified PMPA in both resting and activated peripheral blood lymphocytes. Significant differences in the intracellular catabolism of PMPA metabolites were noted between the resting and activated lymphocytes. The half-life for the disappearance of PMPApp, derived from either bis(POC)PMPA or PMPA, was 12 to 15 h in the activated lymphocytes and 33 to 50 h in the resting lymphocytes. This long persistence of PMPApp, particularly in resting lymphocytes, may be unique to the nucleoside phosphonate analogs and indicates that effective levels of the active metabolite can be achieved and maintained with relatively infrequent administration of the parent drug.