bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Antiviral Activity of AG7088, a Potent Inhibitor of Human Rhinovirus 3C Protease
Authors: Patick A. K. , Binford S. L. , Brothers M. A. , Jackson R. L. , Ford C. E. , Diem M. D. , Maldonado F. , Dragovich P. S. , Zhou R. , Prins T. J. , Fuhrman S. A. , Meador J. W. , Zalman L. S. , Matthews D. A. , Worland S. T.
Published: October 2018

AG7088 is a potent, irreversible inhibitor of human rhinovirus (HRV) 3C protease {inactivation rate constant (kobs/[I]} = 1,470,000 ± 440,000 M−1s−1for HRV 14) that was discovered by protein structure-based drug design methodologies. In H1-HeLa and MRC-5 cell protection assays, AG7088 inhibited the replication of all HRV serotypes (48 of 48) tested with a mean 50% effective concentration (EC50) of 0.023 μM (range, 0.003 to 0.081 μM) and a mean EC90of 0.082 μM (range, 0.018 to 0.261 μM) as well as that of related picornaviruses including coxsackieviruses A21 and B3, enterovirus 70, and echovirus 11. No significant reductions in the antiviral activity of AG7088 were observed when assays were performed in the presence of α1-acid glycoprotein or mucin, proteins present in nasal secretions. The 50% cytotoxic concentration of AG7088 was >1,000 μM, yielding a therapeutic index of >12,346 to >333,333. In a single-cycle, time-of-addition assay, AG7088 demonstrated antiviral activity when added up to 6 h after infection. In contrast, a compound targeting viral attachment and/or uncoating was effective only when added at the initiation of virus infection. Direct inhibition of 3C proteolytic activity in infected cells treated with AG7088 was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of radiolabeled proteins, which showed a dose-dependent accumulation of viral precursor polyproteins and reduction of processed protein products. The broad spectrum of antiviral activity of AG7088, combined with its efficacy even when added late in the virus life cycle, highlights the advantages of 3C protease as a target and suggests that AG7088 will be a promising clinical candidate.
Prevalence of Antimicrobial Resistance in Respiratory Tract Isolates of
Streptococcus pneumoniae
: Results of a Canadian National Surveillance Study
Authors: Zhanel George G. , Karlowsky James A. , Palatnick Lorraine , Vercaigne Laverne , Low Donald E. ,   The Canadian Respiratory Infection Study Group, Hoban Daryl J.
Published: October 2018

From October 1997 to November 1998, 1,180 respiratory tract isolates of
Streptococcus pneumoniae
were collected from 18 medical centers in 9 of the 10 Canadian provinces. Penicillin-intermediate and -resistant isolates occurred at rates of 14.8 and 6.4%, respectively, and these rates varied considerably by geographic region. Trimethoprim-sulfamethoxazole, tetracycline, and macrolide rates of nonsusceptibility were 12.2, 10.6, and 8.0 to 9.3%, respectively. The most potent agents studied were newer fluoroquinolones.
Drug Efflux and
parC
Mutations Are Involved in Fluoroquinolone Resistance in Viridans Group Streptococci
Authors: Ferrándiz María José , Oteo Jesús , Aracil Belén , Gómez-Garcés Jose Luis , De La Campa Adela G.
Published: October 2018

Nine ciprofloxacin-resistant viridans group streptococci isolated from asymptomatic carriers were analyzed. Identification to the species level by using three different commercial systems and a PCR-based approach was inconsistent. The nucleotide sequences of fragments of the
parC
,
parE
,
gyrA
, and
gyrB
genes showed considerable intra- and interspecies variations, and these variations mainly involved silent mutations. Three isolates had changes in Ser-79 of ParC (to Phe or Tyr). Phenotypic characterization indicated that eight of the nine isolates had a putative efflux mechanism that would confer low-level resistance to ciprofloxacin.
Treatment of Experimental Staphylococcal Endocarditis Due to a Strain with Reduced Susceptibility In Vitro to Vancomycin: Efficacy of Ampicillin-Sulbactam
Authors: Backo Mirjana , Gaenger Eliza , Burkart Anna , Chai Yin Li , Bayer Arnold S.
Published: October 2018

We evaluated several 3-day antimicrobial regimens in the treatment of experimental endocarditis caused by an oxacillin-resistant
Staphylococcus aureus
strain exhibiting intermediate susceptibility in vitro to vancomycin (VISA). Neither vancomycin alone nor trovafloxacin exhibited in vivo efficacy; addition of amikacin to vancomycin yielded a modest in vivo effect. In contrast, the combination of ampicillin and sulbactam was highly effective in vivo, causing a mean decrease in VISA vegetation densities of >5 log
10
CFU/g versus those of untreated controls.
Antimicrobial Susceptibilities and Serogroups of Clinical Strains of
Clostridium difficile
Isolated in France in 1991 and 1997
Authors: Barbut Frédéric , Decré Dominique , Burghoffer Béatrice , Lesage Danièle , Delisle Françoise , Lalande Valérie , Delmée Michel , Avesani Véronique , Sano Nassita , Coudert Cyril , Petit Jean-Claude
Published: October 2018

Glycopeptides (vancomycin and teicoplanin) and metronidazole are the drugs of choice for the treatment of
Clostridium difficile
infections, but trends in susceptibility patterns have not been assessed in the past few years. The objective was to study the MICs of glycopeptides and metronidazole for unrelated
C. difficile
strains isolated in 1991 (
n
= 100) and in 1997 (
n
= 98) by the agar macrodilution, the E-test, and the disk diffusion methods. Strain susceptibilities to erythromycin, clindamycin, tetracycline, rifampin, and chloramphenicol were also determined by the ATB ANA gallery (bioMérieux, La Balme-les-Grottes, France). The MICs at which 50% of isolates are inhibited (MIC
50
s) and MIC
90
s of glycopeptides and metronidazole remained stable between 1991 and 1997. All the strains were inhibited by concentrations that did not exceed 2 μg/ml for vancomycin and 1 μg/ml for teicoplanin. Comparison of MICs determined by the agar dilution method recommended by the National Committee for Clinical Laboratory Standards and the E test showed correlations (±2 dilutions) of 86.6, 95.9, and 99% for metronidazole, vancomycin, and teicoplanin, respectively. The E test always underestimated the MICs. Strains with decreased susceptibility to metronidazole (MICs, ≥8 μg/ml) were isolated from six patients (
n
= 4 in 1991 and
n
= 2 in 1997). These strains were also detected by the disk diffusion method (zone inhibition diameter, ≤21 mm); they belonged to nontoxigenic serogroup D (
n
= 5) and toxigenic serogroup H (
n
= 1). Decreased susceptibility to erythromycin (MICs, ≥1 μg/ml), clindamycin (MICs, ≥2 μg/ml), tetracycline (MICs, ≥8 μg/ml), rifampin (MICs, ≥4 μg/ml), and chloramphenicol (MICs, ≥16 μg/ml) was observed in 64.2, 80.3, 23.7, 22.7, and 14.6% of strains, respectively. Strains isolated in 1997 were more susceptible than those isolated in 1991, and this trend was correlated to a major change in serogroup distribution. Periodic studies are needed in order to detect changes in serogroups and the emergence of strains with decreased susceptibility to therapeutic drugs.
Kinetics of Antiviral Activity and Intracellular Pharmacokinetics of Human Immunodeficiency Virus Type 1 Protease Inhibitors in Tissue Culture
Authors: Nascimbeni Michelina , Lamotte Claire , Peytavin Gilles , Farinotti Robert , Clavel François
Published: October 2018

We have examined the kinetics of the inhibition of human immunodeficiency virus type 1 (HIV-1) particle infectivity by protease inhibitors (PIs) in cell culture, using either transfected HeLa cells or infected peripheral blood mononuclear cells (PBMCs) as producers of infectious virions. Both the kinetics of the initiation of antiviral activity after addition of the PIs to these cultures and the kinetics of restoration of virion infectivity after removal of the PIs from the treated cultures were examined. We found that the kinetics of initiation of particle infectivity inhibition produced by a high extracellular concentration (5 μM) of the inhibitors were similar for all five inhibitors tested: loss of particle infectivity was perceptible as early as 1 h after the initiation of PI treatment and increased gradually thereafter. By contrast, the durability of this antiviral effect following removal of the drug from the culture varied dramatically according to the drug studied. In transfected HeLa cells, saquinavir and nelfinavir exerted the most prolonged inhibition, with the half-lives of their antiviral activities being greater than 24 h, while ritonavir exerted an intermediate length of inhibition (18 h) and indinavir and amprenavir exerted a reproducibly shorter length of inhibition (5 h). For all five tested PIs, these kinetics were significantly faster in PBMCs than in HeLa cells. The striking differences in antiviral kinetics observed among the different PIs appear mostly due to differences in their intracellular concentrations and/or rates of cellular clearance. Our observations, although limited to tissue culture conditions, may help delineate the cellular parameters of the antiviral activities of HIV-1 PIs and further optimize the efficiencies of these antiretrovirals in vivo.
Diversity of TEM Mutants in
Proteus mirabilis
Authors: Bonnet R. , De Champs C. , Sirot D. , Chanal C. , Labia R. , Sirot J.
Published: October 2018

In a survey of resistance to amoxicillin among clinical isolates of
Proteus mirabilis
, 10 TEM-type β-lactamases were characterized: (i) the well-known penicillinases TEM-1 and TEM-2, the extended-spectrum β-lactamases (ESBLs) TEM-3 and TEM-24, and the inhibitor-resistant TEM (IRT) TEM-44 and (ii) five novel enzymes, a penicillinase TEM-57 similar to TEM-1, an ESBL TEM-66 similar to TEM-3, and three IRTs, TEM-65, TEM-73, and TEM-74. The penicillinase TEM-57 and the ESBL TEM-66 differed from TEM-1 and TEM-3, respectively, by the amino acid substitution Gly-92→Asp (nucleotide mutation G-477→A). This substitution could have accounted for the decrease in pIs (5.2 for TEM-57 and 6.0 for TEM-66) but did not necessarily affect the intrinsic activities of these enzymes. The IRT TEM-65 was an IRT-1-like IRT (Cys-244) related to TEM-2 (Lys-39). The two other IRTs, TEM-73 and TEM-74, were related to IRT-1 (Cys-244) and IRT-2 (Ser-244), respectively, and harbored the amino acid substitutions Leu-21→Phe and Thr-265→Met. In this study, the ESBLs TEM-66, TEM-24, and TEM-3 were encoded by large (170- to 180-kb) conjugative plasmids that exhibited similar patterns after digestion and hybridization with the TEM and AAC(6′)I probes. The three IRTs TEM-65, TEM-73, and TEM-74 were encoded by plasmids that ranged in size from 42 to 70 kb but for which no transfer was obtained. The characterization of five new plasmid-mediated TEM-type β-lactamases and the first report of TEM-24 in
P. mirabilis
are evidence of the wide diversity of β-lactamases produced in this species and of its possible role as a β-lactamase-encoding plasmid reservoir.
Civamide (
cis
-Capsaicin) for Treatment of Primary or Recurrent Experimental Genital Herpes
Authors: Bourne N. , Bernstein D. I. , Stanberry L. R.
Published: October 2018

Neuropharmacologic agents able to disrupt normal virus-neuron interactions may provide an alternative strategy for the treatment of herpes simplex virus (HSV) infections. We have previously shown that prophylactic treatment with capsaicin, a natural compound that alters function in sensory neurons, can protect guinea pigs against cutaneous HSV disease, even though the compound has no direct antiviral activity. Here we have examined the ability of civamide, the
cis
isomer of capsaicin, to interfere with HSV disease. We show that, even when the onset of treatment was delayed until after intravaginal virus challenge, primary genital skin disease severity was significantly reduced. In addition, animals treated during primary infection subsequently experienced a long-lasting reduction in recurrent disease. Civamide treatment during latent infection also significantly reduced recurrent disease, although for a shorter period. Further a single weekly treatment with civamide during latent infection was sufficient to reduce recurrent disease, indicating that an infrequent suppressive maintenance therapy might be possible.
Decreased Antipyrine Clearance following Endotoxin Administration: In Vivo Evidence of the Role of Nitric Oxide
Authors: Kitaichi Kiyoyuki , Wang Li , Takagi Kenji , Iwase Mitsunori , Shibata Eiji , Nadai Masayuki , Takagi Kenzo , Hasegawa Takaaki
Published: October 2018

Klebsiella pneumoniae
endotoxin has been found to decrease hepatic P450-mediated drug-metabolizing enzyme activity in a time-dependent manner. In this study, we investigated the role of nitric oxide (NO) in the decrease in hepatic drug-metabolizing enzyme activity caused by endotoxin in vivo. We measured in vivo pharmacokinetic parameters of antipyrine in rats treated with endotoxin and/or a selective inhibitor of inducible NO synthase (iNOS),
S
-methylisothiourea. Intraperitoneal injection of endotoxin (1 mg/kg of body weight) dramatically decreased the systemic clearance of antipyrine, reflecting reduced hepatic drug-metabolizing enzyme activity, and significantly increased the level of nitrite and nitrate (NOx) in the plasma.
S
-Methylisothiourea (10 mg/kg) reversed this decreasing antipyrine clearance and reduced the level of NOx in plasma. Repeated injections of an NO donor, (±)-(
E
)-4-ethyl-2-[(
E
)-hydroxyimino]-5-nitro-3-hexenamide (FK-409; 10 mg/kg), at a dose which maintained plasma NOx at the same levels as those caused by endotoxin injection, also decreased the systemic clearance of antipyrine. These findings suggest that the overproduction of NO observed in this animal model is at least partially responsible for the significant reduction in the hepatic drug-metabolizing enzyme activity that may happen in a gram-negative bacterial infection.
The ATP Binding Cassette Transporter Gene
CgCDR1
from
Candida glabrata
Is Involved in the Resistance of Clinical Isolates to Azole Antifungal Agents
Authors: Sanglard Dominique , Ischer Françoise , Calabrese David , Majcherczyk Paul A. , Bille Jacques
Published: October 2018

The resistance mechanisms to azole antifungal agents were investigated in this study with two pairs of
Candida glabrata
clinical isolates recovered from two separate AIDS patients. The two pairs each contained a fluconazole-susceptible isolate and a fluconazole-resistant isolate, the latter with cross-resistance to itraconazole and ketoconazole. Since the accumulation of fluconazole and of another unrelated substance, rhodamine 6G, was reduced in the azole-resistant isolates, enhanced drug efflux was considered as a possible resistance mechanism. The expression of multidrug efflux transporter genes was therefore examined in the azole-susceptible and azole-resistant yeast isolates. For this purpose,
C. glabrata
genes conferring resistance to azole antifungals were cloned in a
Saccharomyces cerevisiae
strain in which the ATP binding cassette (ABC) transporter gene
PDR5
was deleted. Three different genes were recovered, and among them, only
C. glabrata CDR1
(
CgCDR1
), a gene similar to the
Candida albicans
ABC transporter
CDR
genes, was upregulated by a factor of 5 to 8 in the azole-resistant isolates. A correlation between upregulation of this gene and azole resistance was thus established. The deletion of
CgCDR1
in an azole-resistant
C. glabrata
clinical isolate rendered the resulting mutant (DSY1041) susceptible to azole derivatives as the azole-susceptible clinical parent, thus providing genetic evidence that a specific mechanism was involved in the azole resistance of a clinical isolate. When
CgCDR1
obtained from an azole-susceptible isolate was reintroduced with the help of a centromeric vector in DSY1041, azole resistance was restored and thus suggested that a
trans
-acting mutation(s) could be made responsible for the increased expression of this ABC transporter gene in the azole-resistant strain. This study demonstrates for the first time the determinant role of an ABC transporter gene in the acquisition of resistance to azole antifungals by
C. glabrata
clinical isolates.
Effects of F171 Mutations in the 6′-
N
-Acetyltransferase Type Ib [AAC(6′)-Ib] Enzyme on Susceptibility to Aminoglycosides
Authors: Chavideh Ramona , Sholly Steven , Panaite Doina , Tolmasky Marcelo E.
Published: October 2018

Substitutions at position F171 of 6′-
N
-acetyltransferase type Ib cause variable loss of aminoglycoside resistance, indicating that this residue plays an important role in the structure and/or function of the enzyme.
Azithromycin as Treatment for Disseminated
Mycobacterium avium
Complex in AIDS Patients
Authors: Koletar Susan L. , Berry Alison J. , Cynamon Michael H. , Jacobson Jeffrey , Currier Judith S. , MacGregor Rob Roy , Dunne Michael W. , Williams Debra J.
Published: October 2018

This multicenter, randomized, dose-ranging study was performed to determine the safety and efficacy of two different doses of azithromycin for treating disseminated
Mycobacterium avium
complex (MAC) in patients with AIDS. Eighty-eight AIDS patients with symptoms and blood cultures consistent with disseminated MAC were treated with 600 or 1,200 mg of azithromycin daily for 6 weeks; 62 patients completed the entire 6 weeks of study. Of note, this study was done prior to the time when combination antiretroviral or anti-MAC regimens were the standard of care. Over the 6-week study period, symptomatic improvement was noted in both dose groups. Microbiological responses were comparable, with mean decreases of 1.5 and 2.0 log CFU/ml in the high- and low-dose groups, respectively. Sterilization of blood cultures occurred in 54% of samples; patients with lower baseline colony counts were more likely to achieve culture negativity. Resistance developed in one patient. Gastrointestinal symptoms were the most common side effects and were more frequent in patients receiving 1,200 mg. Azithromycin is a useful alternative treatment for disseminated MAC infection in AIDS patients. Symptomatic improvement correlates with measurable decreases in mycobacterial load.
Activities of the Oxazolidinones Linezolid and Eperezolid in Experimental Intra-Abdominal Abscess Due to
Enterococcus faecalis
or Vancomycin-Resistant
Enterococcus faecium
Authors: Schülin T. , Thauvin-Eliopoulos C. , Moellering R. C. , Eliopoulos G. M.
Published: October 2018

The in vivo effectiveness of oxazolidinones eperezolid (U-100592) and linezolid (U-100766) against one strain each of
Enterococcus faecalis
and vancomycin-resistant
Enterococcus faecium
was examined in a rat model of intra-abdominal abscess. MICs of both drugs were 2 μg/ml for each strain. At doses of 25 mg/kg of body weight twice daily intravenously or orally, linezolid produced small but statistically significant reductions in abscess bacterial density for
E. faecalis
. The reduction in viable cells observed would not likely be clinically relevant. Eperezolid was ineffective at this dose. At a dosage of 100 mg/kg/day, linezolid treatment led to an approximately 100-fold reduction in viable cells per gram of abscess. Against
E. faecium
infections, intravenous eperezolid and oral linezolid were effective, reducing densities approximately 2 log
10
CFU/g. Both oxazolidinones demonstrated activity against enterococci in this model. However, results were modest with the dosing regimens employed.
Activities of Poloxamer CRL-1072 againstMycobacterium aviumin Macrophage Culture and in Mice
Authors: Jagannath Chinnaswamy , Emanuele Martin R. , Hunter Robert L.
Published: October 2018

Earlier studies reported that certain large hydrophobic poloxamer surfactants were able to inhibit the growth ofMycobacterium avium-M. intracellularecomplex (MAI) in broth and to produce synergistic enhancement of the activity of rifampin. CRL-1072 was synthesized to have an optimal structure for antimicrobic effects and greater purity. Its MIC for MAI in broth was greater than 100 μg/ml. Surprisingly, its MIC for MAI growing in human U937 monocytoid cells was much lower, 5 μg/ml. A still lower concentration, 0.1 μg/ml, produced synergistic enhancement of the activities of clarithromycin, rifampin, amikacin, streptomycin, and clindamycin, but not isoniazid, against MAI infecting monocytoid cells. Mice tolerated injection of doses of CRL-1072 as high as 125 mg/kg of body weight. Pharmacokinetic analysis revealed that the copolymer had an elimination half-life of 60 h and suggested dosing regimens that might produce therapeutic concentrations in tissue. In a mouse model of acute MAI infection, CRL-1072 significantly enhanced the bactericidal activities of clarithromycin and rifampin when it was administered at 1.0 mg/kg intravenously (i.v.) three times per week. CRL-1072 given i.v. or orally also enhanced the bactericidal activity of clindamycin against MAI.
Novel Streptomycin and Spectinomycin Resistance Gene as a Gene Cassette within a Class 1 Integron Isolated from
Escherichia coli
Authors: Sandvang Dorthe
Published: October 2018

The
aadA
genes, encoding resistance to streptomycin and spectinomycin, have been found as gene cassettes in different gram-negative and gram-positive bacterial species. The present study has revealed the sequence of a new gene,
aadA5
, integrated as a gene cassette together with the trimethoprim resistance gene
dfr7
in a class 1 integron. The integron was located on a plasmid and was identified in a pathogenic porcine
Escherichia coli
isolate.
In Vitro Activities of Ketolide HMR3647, Macrolides, and Other Antibiotics against
Lactobacillus
,
Leuconostoc
, and
Pediococcus
Isolates
Authors: Zarazaga M. , Sáenz Y. , Portillo A. , Tenorio C. , Ruiz-Larrea F. , Del Campo R. , Baquero F. , Torres C.
Published: October 2018

Testing of susceptibility to 13 antibiotics was performed with 90 isolates of
Lactobacillus
,
Leuconostoc
, and
Pediococcus
. MICs at which 90% of the isolates tested were inhibited by HMR3647, erythromycin, and ciprofloxacin were 0.015, 0.125 and 32 μg/ml, respectively. The penicillin MIC was ≥16 μg/ml against 26.2% of the studied
Lactobacillus
sp. isolates and 50% of
Lactobacillus plantarum
. HMR3647 showed excellent activity against these genera.
A Rapid Non-Culture-Based Assay for Clinical Monitoring of Phenotypic Resistance of Human Immunodeficiency Virus Type 1 to Lamivudine (3TC)
Authors: García Lerma J. Gerardo , Schinazi Raymond F. , Juodawlkis Amy S. , Soriano Vincent , Lin Yulin , Tatti Kathleen , Rimland David , Folks Thomas M. , Heneine Walid
Published: October 2018

Monitoring for lamivudine (3TC) resistance is important both for the clinical management of human immunodeficiency virus type 1 (HIV-1)-infected patients treated with 3TC and for surveillance of transmission of 3TC-resistant HIV-1. We developed a novel non-culture-based assay for the rapid analysis of phenotypic resistance to 3TC of HIV-1 in plasma. The assay measures the susceptibility of HIV-1 reverse transcriptase (RT) activity to 3TC triphosphate (3TC-TP) in plasma. RT detection was done by the Amp-RT assay, an ultrasensitive PCR-based RT assay. Under our assay conditions, we found that 5 μM 3TC-TP inhibited RT activity from wild-type (WT), zidovudine-resistant, or nevirapine-resistant HIV-1 but not from HIV-1 carrying either the M184V mutation or multidrug (MD) resistance mutations (77L/116Y/151M or 62V/75I/77L/116Y/151M). Mixing experiments showed a detection threshold of 10% 3TC-resistant virus (M184V) in a background of WT HIV-1. To validate the assay for the detection of phenotypic resistance of HIV-1 to 3TC in plasma samples, HIV-1 RT in 30 plasma specimens collected from 15 patients before and during therapy with 3TC was tested for evidence of phenotypic resistance by the Amp-RT assay. The results were compared with those of genotypic analysis. The RT in 12 samples was found to be 3TC sensitive, while the RT in 18 samples had evidence of phenotypic resistance. All 12 samples with 3TC-sensitive RT had WT genotypes at codon 184 and were retrieved before treatment with 3TC. In contrast, all 18 specimens with 3TC-resistant RT were posttherapy samples. This assay provides a simple, rapid, and reliable method for the detection of phenotypic resistance of HIV-1 to 3TC in plasma.
Electrolytic Generation of Oxygen Partially Explains Electrical Enhancement of Tobramycin Efficacy against
Pseudomonas aeruginosa
Biofilm
Authors: Stewart Philip S. , Wattanakaroon Wanida , Goodrum Lu , Fortun Susana M. , McLeod Bruce R.
Published: October 2018

The role of electrolysis products, including protons, hydroxyl ions, reactive oxygen intermediates, oxygen, hydrogen, and heat, in mediating electrical enhancement of killing of
Pseudomonas aeruginosa
biofilms by tobramycin (the bioelectric effect) was investigated. The log reduction in biofilm viable cell numbers compared to the numbers for the untreated positive control effected by antibiotic increased from 2.88 in the absence of electric current to 5.58 in the presence of electric current. No enhancement of antibiotic efficacy was observed when the buffer composition was changed to simulate the reduced pH that prevails during electrolysis. Neither did stabilization of the pH during electrical treatment by increasing the buffer strength eliminate the bioelectric effect. The temperature increase measured in our experiments, less than 0.2°C, was far too small to account for the greatly enhanced antibiotic efficacy. The addition of sodium thiosulfate, an agent capable of rapidly neutralizing reactive oxygen intermediates, did not abolish electrical enhancement of killing. The bioelectric effect persisted when all of the ionic constituents of the medium except the two phosphate buffer components were omitted. This renders the possibility of electrochemical generation of an inhibitory ion, such as nitrite from nitrate, an unlikely explanation for electrical enhancement. The one plausible explanation for the bioelectric effect revealed by this study was the increased delivery of oxygen to the biofilm due to electrolysis. When gaseous oxygen was bubbled into the treatment chamber during exposure to tobramycin (without electric current), a 1.8-log enhancement of killing resulted. The enhancement of antibiotic killing by oxygen was not due simply to physical disturbances caused by sparging the gas because similar delivery of gaseous hydrogen caused no enhancement whatsoever.
Pharmacokinetics of the Antiviral Agent β-
d
-2′,3′-Didehydro-2′,3′-Dideoxy-5-Fluorocytidine in Rhesus Monkeys
Authors: Ma Li , Hurwitz Selwyn J. , Shi Junxing , McAtee Jeffrey J. , Liotta Dennis C. , McClure Harold M. , Schinazi Raymond F.
Published: October 2018

The values of the pharmacokinetic parameters of the nucleoside antiretroviral agent β-
d
-2′,3′-didehydro-2′,3′-dideoxy-5-fluorocytidine (D-D4FC) in rhesus monkeys were determined with a two-compartment model after the administration of a single dose. The average values for the terminal half-life, renal clearance, and total systemic clearance for the intravenous administration route were 3.6 h and 0.31 and 0.43 liter · kg
−1
· h
−1
, respectively. The oral bioavailability of D-D4FC averaged 41%. For the intravenous administration route, 76% of the compound was recovered intact in the urine within 8 h, indicating that D-D4FC was eliminated mainly by renal excretion. D-D4FC was detected in the cerebrospinal fluid (CSF) at similar concentrations after administration by both the intravenous and oral routes. D-D4FC levels in plasma and CSF were higher than the median effective concentration for human immunodeficiency virus type 1 in vitro.
Interplay between Chromosomal β-Lactamase and the MexAB-OprM Efflux System in Intrinsic Resistance to β-Lactams in
Pseudomonas aeruginosa
Authors: Masuda Nobuhisa , Gotoh Naomasa , Ishii Chie , Sakagawa Eiko , Ohya Satoshi , Nishino Takeshi
Published: October 2018

We investigated the role of chromosomal β-lactamase and the MexAB-OprM efflux system in intrinsic resistance to β-lactams in
Pseudomonas aeruginosa
. Determination of the susceptibilities of a series of isogenic mutants with impaired production of the β-lactamase and the efflux system to 16 β-lactams including penicillins, cephems, oxacephems, carbapenems, and a monobactam demonstrated that the intrinsic resistance of
P. aeruginosa
to most of the β-lactams is due to the interplay of both factors.
Carbapenem Activities against
Pseudomonas aeruginosa
: Respective Contributions of OprD and Efflux Systems
Authors: Köhler Thilo , Michea-Hamzehpour Mehri , Epp Simone F. , Pechere Jean-Claude
Published: October 2018

While meropenem MICs were strongly influenced by the presence or absence of the MexAB-OprM efflux pump in both OprD-proficient and -deficient strain backgrounds, MICs of imipenem and of ER-35786 remained unchanged, demonstrating that meropenem is a substrate of MexAB-OprM but not imipenem and ER-35786. In vitro, all three carbapenems selected loss of OprD as a first mechanism of resistance. However, in an OprD-deficient background, meropenem was able to select MexAB-OprM overproducers as a secondary resistance mechanism, while ER-35786 selected a mutant cross-resistant to sparfloxacin and cefpirome.
Inhibition of Human Immunodeficiency Virus Type 1 Replication by Combination of Transcription Inhibitor K-12 and Other Antiretroviral Agents in Acutely and Chronically Infected Cells
Authors: Okamoto Mika , Okamoto Takashi , Baba Masanori
Published: October 2018

8 - Difluoromethoxy - 1 - ethyl - 6 - fluoro - 1,4 - dihydro - 7 - [4 - (2 - methoxyphenyl) - 1 - piperazinyl] - 4 - oxoquinoline - 3 - carboxylic acid (K-12) has recently been identified as a potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) transcription. In this study, we examined several combinations of K-12 and other antiretroviral agents for their inhibitory effects on HIV-1 replication in acutely and chronically infected cell cultures. Combinations of K-12 and a reverse transcriptase (RT) inhibitor, either zidovudine, lamivudine, or nevirapine, synergistically inhibited HIV-1 replication in acutely infected MT-4 cells. The combination of K-12 and the protease inhibitor nelfinavir (NFV) also synergistically inhibited HIV-1, whereas the synergism of this combination was weaker than that of the combinations with the RT inhibitors. K-12 did not enhance the cytotoxicities of RT and protease inhibitors. Synergism of the combinations was also observed in acutely infected peripheral blood mononuclear cells. The combination of K-12 and cepharanthine, a nuclear factor κB inhibitor, synergistically inhibited HIV-1 production in tumor necrosis factor alpha-stimulated U1 cells, a promonocytic cell line chronically infected with the virus. In contrast, additive inhibition was observed for the combination of K-12 and NFV. These results indicate that the combinations of K-12 and clinically available antiretroviral agents may have potential as chemotherapeutic modalities for the treatment of HIV-1 infection.
Effects of the Chinese Traditional Medicine Mao-Bushi-Saishin-To on Therapeutic Efficacy of a New Benzoxazinorifamycin, KRM-1648, againstMycobacterium aviumInfection in Mice
Authors: Shimizu Toshiaki , Tomioka Haruaki , Sato Katsumasa , Sano Chiaki , Akaki Tatsuya , Dekio Satoshi , Yamada Yoshitaka , Kamei Tsutomu , Shibata Hiroki , Higashi Natsumi
Published: October 2018

The Chinese traditional medicine mao-bushi-saishin-to (MBST), which has anti-inflammatory effects and has been used to treat the common cold and nasal allergy in Japan, was examined for its effects on the therapeutic activity of a new benzoxazinorifamycin, KRM-1648 (KRM), againstMycobacterium aviumcomplex (MAC) infection in mice. In addition, we examined the effects of MBST on the anti-MAC activity of murine peritoneal macrophages (Mφs). First, MBST significantly increased the anti-MAC therapeutic activity of KRM when given to mice in combination with KRM, although MBST alone did not exhibit such effects. Second, MBST treatment of Mφs significantly enhanced the KRM-mediated killing of MAC bacteria residing in Mφs, although MBST alone did not potentiate the Mφ anti-MAC activity. MBST-treated Mφs showed decreased levels of reactive nitrogen intermediate (RNI) release, suggesting that RNIs are not decisive in the expression of the anti-MAC activity of such Mφ populations. MBST partially blocked the interleukin-10 (IL-10) production of MAC-infected Mφs without affecting their transforming growth factor β (TGF-β)-producing activity. Reverse transcription-PCR analysis of the lung tissues of MAC-infected mice at weeks 4 and 8 after infection revealed a marked increase in the levels of tumor necrosis factor alpha, gamma interferon (IFN-γ), IL-10, and TGF-β mRNAs. KRM treatment of infected mice tended to decrease the levels of the test cytokine mRNAs, except that it increased TGF-β mRNA expression at week 4. MBST treatment did not affect the levels of any cytokine mRNAs at week 8, while it down-regulated cytokine mRNA expression at week 4. At week 8, treatment of mice with a combination of KRM and MBST caused a marked decrease in the levels of the test cytokines mRNAs, especially IL-10 and IFN-γ mRNAs, although such effects were obscure at week 4. These findings suggest that down-regulation of the expression of IL-10 and TGF-β is related to the combined therapeutic effects of KRM and MBST against MAC infection.
Reduced Pyrazinamidase Activity and the Natural Resistance of
Mycobacterium kansasii
to the Antituberculosis Drug Pyrazinamide
Authors: Sun Zhonghe , Zhang Ying
Published: October 2018

Pyrazinamide (PZA), an analog of nicotinamide, is a prodrug that requires conversion to the bactericidal compound pyrazinoic acid (POA) by the bacterial pyrazinamidase (PZase) activity of nicotinamidase to show activity against
Mycobacterium tuberculosis
. Mutations leading to a loss of PZase activity cause PZA resistance in
M. tuberculosis. M. kansasii
is naturally resistant to PZA and has reduced PZase activity along with an apparently detectable nicotinamidase activity. The role of the reduction in PZase activity in the natural PZA resistance of
M. kansasii
is unknown. The MICs of PZA and POA for
M. kansasii
were determined to be 500 and 125 μg/ml, respectively. Using [
14
C]PZA and [
14
C]nicotinamide, we found that
M. kansasii
had about 5-fold-less PZase activity and about 25-fold-less nicotinamidase activity than
M. tuberculosis
. The
M. kansasii pncA
gene was cloned on a 1.8-kb
Bam
HI DNA fragment, using
M. avium pncA
probe. Sequence analysis showed that the
M. kansasii pncA
gene encoded a protein with homology to its counterparts from
M. tuberculosis
(69.9%),
M. avium
(65.6%), and
Escherichia coli
(28.5%). Transformation of naturally PZA-resistant
M. bovis
BCG with
M. kansasii pncA
conferred partial PZA susceptibility. Transformation of
M. kansasii
with
M. avium pncA
caused functional expression of PZase and high-level susceptibility to PZA, indicating that the natural PZA resistance in
M. kansasii
results from a reduced PZase activity. Like
M. tuberculosis
,
M. kansasii
accumulated POA in the cells at an acidic pH; however, due to its highly active POA efflux pump, the naturally PZA-resistant species
M. smegmatis
did not. These findings suggest the existence of a weak POA efflux mechanism in
M. kansasii
.
Structure-Function Studies of Ser-289 in the Class C β-Lactamase from
Enterobacter cloacae
P99
Authors: Trépanier Sonia , Knox James R. , Clairoux Natalie , Sanschagrin François , Levesque Roger C. , Huletsky Ann
Published: October 2018

Site-directed mutagenesis of Ser-289 of the class C β-lactamase from
Enterobacter cloacae
P99 was performed to investigate the role of this residue in β-lactam hydrolysis. This amino acid lies near the active site of the enzyme, where it can interact with the C-3 substituent of cephalosporins. Kinetic analysis of six mutant β-lactamases with five cephalosporins showed that Ser-289 can be substituted by amino acids with nonpolar or polar uncharged side chains without altering the catalytic efficiency of the enzyme. These data suggest that Ser-289 is not essential in the binding or hydrolytic mechanism of AmpC β-lactamase. However, replacement by Lys or Arg decreased by two- to threefold the
k
cat
of four of the five β-lactams tested, particularly cefoperazone, cephaloridine, and cephalothin. Three-dimensional models of the mutant β-lactamases revealed that the length and positive charge of the side chain of Lys and Arg could create an electrostatic linkage to the C-4 carboxylic acid group of the dihydrothiazine ring of the acyl intermediate which could slow the deacylation step or hinder release of the product.
Comparative Study of the Anti-Human Cytomegalovirus Activities and Toxicities of a Tetrahydrofuran Phosphonate Analogue of Guanosine and Cidofovir
Authors: Bedard Jean , May Suzanne , Lis Martin , Tryphonas Leander , Drach John , Huffman John , Sidwell Robert , Chan Laval , Bowlin Terry , Rando Robert
Published: October 2018

Cidofovir is the first nucleoside monophosphate analogue currently being used for the treatment of human cytomegalovirus (HCMV) retinitis in individuals with AIDS. Unfortunately, the period of therapy with the use of this compound may be limited due to the possible emergence of serious irreversible nephrotoxic effects. New drugs with improved toxicity profiles are needed. The goal of this study was to investigate the anticytomegaloviral properties and drug-induced toxicity of a novel phosphonate analogue, namely, (−)-2-(
R
)-dihydroxyphosphinoyl-5-(
S
)-(guanin-9′-yl-methyl) tetrahydrofuran (compound 1), in comparison with those of cidofovir. The inhibitory activities of both compounds on HCMV propagation in vitro were similar against the AD 169 and Towne strains, with 50% inhibitory concentrations ranging from 0.02 to 0.17 μg/ml for cidofovir and <0.05 to 0.09 μg/ml for compound 1. A clinical HCMV isolate that was resistant to ganciclovir and that had a known mutation within the UL54 DNA polymerase gene and a cidofovir-resistant laboratory strain derived from strain AD 169 remained sensitive to compound 1, whereas their susceptibilities to ganciclovir and cidofovir were reduced by 33- and 10-fold, respectively. Both compound 1 and cidofovir exhibited equal potencies in an experimentally induced murine cytomegalovirus (MCMV) infection in mice, with a prevention or prolongation of mean day to death at dosages of 1.0, 3.2, and 10.0 mg/kg of body weight/day. In cytotoxicity experiments, compound 1 was found to be generally more toxic than cidofovir in cell lines Hs68, HFF, and 3T3-L1 (which are permissive for HCMV or MCMV replication) but less toxic than cidofovir in MRC-5 cells (which are permissive for HCMV replication). Drug-induced toxic side effects were noticed for both compounds in rats and guinea pigs in a 5-day repeated-dose study. In guinea pigs, a greater weight loss was noticed with cidofovir than with compound 1 at dosages of 3.0 and 10.0 mg/kg/day. An opposite effect was detected in rats, which were treated with the compounds at relatively high dosages (up to 100 mg/kg/day). Compound 1 and cidofovir were nephrotoxic in both rats and guinea pigs, with the epithelium lining the proximal convoluted tubules in the renal cortex being the primary target site. The incidence and the severity of the lesions were found to be dose dependent. The lesions observed were characterized by cytoplasm degeneration and nuclear modifications such as karyomegaly, the presence of pseudoinclusions, apoptosis, and degenerative changes. In the guinea pig model, a greater incidence and severity of lesions were observed for cidofovir than for compound 1 (
P
< 0.001) with a drug regimen of 10 mg/kg/day.
A Multiple Drug Interaction Study of Stavudine with Agents for Opportunistic Infections in Human Immunodeficiency Virus-Infected Patients
Authors: Piscitelli Stephen C. , Kelly Grace , Walker Robert E. , Kovacs Joseph , Falloon Judith , Davey Richard T. , Raje Sangita , Masur Henry , Polis Michael A.
Published: October 2018

The effects of multiple opportunistic infection medications on stavudine pharmacokinetics were evaluated. Ten patients with CD4 counts of less than 200 cells/mm
3
received stavudine (40 mg twice daily) in combination with one to three other drugs used to treat opportunistic infections. Serial blood samples for stavudine concentrations were collected after 1 week of therapy on each regimen and assayed for stavudine by using a validated high-pressure liquid chromatography method. Although the maximum concentration of drug in serum was significantly decreased when the drug was given in combination with three opportunistic infection medications, the area under the concentration-time curve did not significantly differ across various treatment regimens. Stavudine exposure was not significantly altered by multiple concomitant medications. Side effects were minor throughout the 3-month study period. The tolerability of stavudine, combined with its lack of drug interactions, makes it an attractive agent for use as part of a combination regimen.
Ketolide Treatment of
Haemophilus influenzae
Experimental Pneumonia
Authors: Piper Kerryl E. , Rouse Mark S. , Steckelberg James M. , Wilson Walter R. , Patel Robin
Published: October 2018

The MICs of HMR 3004 and HMR 3647 at which 90% of beta-lactamase-producing
Haemophilus influenzae
isolates were inhibited were 4 and 2 μg/ml, respectively. Both HMR 3004 and HMR 3647 were active against beta-lactamase-producing
H. influenzae
in a murine model of experimental pneumonia. As assessed by pulmonary clearance of
H. influenzae
, HMR 3004 was more effective (
P
< 0.05) than was azithromycin, ciprofloxacin, clarithromycin, erythromycin A, pristinamycin, or HMR 3647 in this model.
Protection by Short-Chain Fatty Acids against 1-β-
d
-Arabinofuranosylcytosine-Induced Intestinal Lesions in Germfree Mice
Authors: Ramos Mariana Gontijo , Bambirra Eduardo Alves , Nicoli Jacques Robert , Cara Denise Carmona , Vieira Enio Cardillo , Alvarez-Leite Jacqueline
Published: October 2018

In germfree mice, the administration of short-chain fatty acids (SCFA) protected the intestinal mucosa from damage produced by 1-β-
d
-arabinofuranosylcytosine (Ara-C). Animals receiving SCFA and Ara-C had intestinal morphologies closer to normal than the control animals, which had severe intestinal lesions. We concluded that orally administrated SCFA reduce intestinal lesions, improving the mucosa pattern of the small intestine and colon.
Pharmacodynamic Effects of Subinhibitory Concentrations of Rufloxacin on Bacterial Virulence Factors
Authors: Braga Pier Carlo , Sala Maria Teresa , dal Sasso Monica
Published: October 2018

It has been reported that subinhibitory concentrations (sub-MICs) of some fluoroquinolones are still capable of affecting the topological characteristics of DNA (inhibition DNA-gyrase) and that this leads to a reduction in some of the factors responsible for bacterial virulence (by means of the disruption of protein synthesis and alterations in phenotype expression), even though the microorganisms themselves are not killed. The present study investigated the ability of sub-MICs of rufloxacin, an orally absorbed monofluorinated quinolone with a long half-life (28 to 30 h), to interfere with the bacterial virulence parameters of adhesiveness, hemagglutination, hydrophobicity, motility, and filamentation, as well as their interactions with host neutrophilic defenses such as phagocytosis, killing, and oxidative bursts. It was observed that
Escherichia coli
adhesiveness was significantly reduced at rufloxacin concentrations of 1/32 MIC, hemagglutination and hydrophobicity were significantly reduced at concentrations of, respectively, 1/4 MIC and 1/8 MIC, and motility was significantly reduced at concentrations of 1/16 MIC; filamentation was still present at concentrations of 1/4 MIC. Phagocytosis was not affected, but killing significantly increased from 1/2 MIC to 1/8 MIC; oxidative bursts measured by means of chemiluminescence were not affected. The fact that sub-MICs are still effective in interfering with the parameters of bacterial virulence is useful information that needs to be correlated with pharmacokinetic data in order to extend our knowledge of the most effective concentrations that can be used to optimize treatment schedules, for example, single administrations, particularly in noncomplicated lower urinary tract infections.
Effectiveness and Toxicity of Gentamicin in an Experimental Model of Pyelonephritis: Effect of the Time of Administration
Authors: LeBrun Michel , Grenier Louis , Gourde Pierrette , Bergeron Michel G. , Labrecque Gaston , Beauchamp Denis
Published: October 2018

Temporal variations in the renal toxicity of aminoglycosides have been reported for experimental animals as well as for humans. In fact, maximal renal toxicity of aminoglycosides was observed when the drug was given during the rest period, while a lower toxicity was observed when the drug was injected during the activity period. The aim of the present study was to evaluate temporal variations in the effectiveness and renal toxicity of gentamicin in an experimental model of pyelonephritis in rats. The experiments were carried out with female Sprague-Dawley rats (185 to 250 g). They had free access to food and water throughout the study and were maintained on a 14-h light–10-h dark cycle. Animals were divided into four groups corresponding to the respective time of induction of pyelonephritis and treatment: 0700, 1300, 1900, and 0100 h. Pyelonephritis was induced by a direct inoculation of
Escherichia coli
(10
7
to 10
8
CFU) in the left kidney. Animals were treated for 3 and 7 days with a single daily dose of gentamicin (20 and 40 mg/kg of body weight, respectively) or saline (NaCl, 0.9%) at either 0700, 1300, 1900, or 0100 h. Animals treated at 0100 h for 3 days with gentamicin (20 mg/kg) showed a significantly lower number of bacteria in their kidneys than did all other groups (
P
< 0.01). After 7 days of treatment, the efficacy, evaluated by the log CFU per gram of tissue and by the percentage of sterilized kidneys, was also higher when gentamicin was administered at 0100 h. The β-galactosidase and the
N
-acetyl-β-
d
-glucosaminidase activities were significantly higher in urine of rats given gentamicin at 1300 h than in urine of rats treated at another time of day (
P
< 0.05). Gentamicin injected at 1300 h induced a significantly greater increase of [
3
H]thymidine incorporation into DNA of renal cortex (
P
< 0.01), a significantly greater inhibition of sphingomyelinase activity (
P
< 0.05), and significantly more histopathological lesions than the same dose injected at another time of the day. Creatinine and blood urea nitrogen levels in serum were significantly higher (
P
< 0.05) and the creatinine clearance was significantly lower (
P
< 0.05) when gentamicin was injected at 1300 h than when it was injected at another time of day. Our data suggest temporal variations in both the toxicity and the effectiveness of gentamicin, the drug being more effective and less toxic when injected during the activity period of the animals.
Selective Inhibition of Human Papillomavirus-Induced Cell Proliferation by (
S
)-1-[3-Hydroxy-2-(Phosphonylmethoxy)propyl]cytosine
Authors: Johnson J. A. , Gangemi J. D.
Published: October 2018

(
S
)-1-[3-Hydroxy-2-(phosphonylmethoxy)propyl]cytosine (HPMPC) is a nucleoside phosphonate analog which in its active diphosphorylated form is known to inhibit herpesvirus DNA polymerase. In this study, we have demonstrated that, in a dose-dependent manner, this compound irreversibly suppressed proliferation of cells infected with human papillomavirus (HPV), which does not possess a viral DNA polymerase. To elucidate the mechanism of cell growth inhibition, cell cycle indicator-regulator expression, thymidine incorporation, transcript levels of apoptosis factors, and anabolic products of HPMPC following drug treatment were evaluated. HPMPC treatment reduced WAF1 (p21) levels independent of those of p53, while proliferating cell nuclear antigen increased. However, in comparison to controls, HPMPC-treated cells displayed a decrease in thymidine incorporation, indicating an inhibition of host DNA polymerase activity. In normal primary keratinocytes, HPMPC predominantly accumulated in the form of the choline adduct HPMPCp-choline. However, in HPV type 16-transformed keratinocytes, HPMPCpp was the most abundant anabolic product, with little HPMPCp-choline having formed. The data imply that an unrecognized viral factor is modulating the conversion of nucleotides, including HPMPC, to the triphosphorylated form.