bluuebunny/crossref_metadata_2025 huggingface dataset:
Monotherapy versus beta-lactam-aminoglycoside combination treatment for gram-negative bacteremia: a prospective, observational study
Authors: Leibovici L , Paul M , Poznanski O , Drucker M , Samra Z , Konigsberger H , Pitlik S D
Published: October 2018

The aim of the present study was to test whether the combination of a beta-lactam drug plus an aminoglycoside has advantage over monotherapy for severe gram-negative infections. Of 2,124 patients with gram-negative bacteremia surveyed prospectively, 670 were given inappropriate empirical antibiotic treatment and the mortality rate in this group was 34%, whereas the mortality rate was 18% for 1,454 patients given appropriate empirical antibiotic treatment (P = 0.0001). The mortality rates for patients given appropriate empirical antibiotic treatment were 17% for 789 patients given a single beta-lactam drug, 19% for 327 patients given combination treatment, 24% for 249 patients given a single aminoglycoside, and 29% for 89 patients given other antibiotics (P = 0.0001). When patients were stratified according to risk factors for mortality other than antibiotic treatment, combination therapy showed no advantage over treatment with a single beta-lactam drug except for neutropenic patients (odds ratio [OR] for mortality, 0.5; 95% confidence interval [95% CI], 0.2 to 1.3) and patients with Pseudomonas aeruginosa bacteremia (OR, 0.7; 95% CI, 0.3 to 1.8). On multivariable logistic regression analysis including all risk factors for mortality, combination therapy had no advantage over therapy with a single beta-lactam drug. The mortality rate for patients treated with a single appropriate aminoglycoside was higher than that for patients given a beta-lactam drug in all strata except for patients with urinary tract infections. When the results of blood cultures were known, 1,878 patients were available for follow-up. Of these, 816 patients were given a single beta-lactam drug, 442 were given combination treatment, and 193 were given a single aminoglycoside. The mortality rates were 13, 15, and 23%, respectively (P = 0.0001). Both on stratified and on multivariable logistic regression analyses, combination treatment showed a benefit over treatment with a single beta-lactam drug only for neutropenic patients (OR, 0.2; 95% CI, 0.05 to 0.7). In summary, combination treatment showed no advantage over treatment with an appropriate beta-lactam drug in nonneutropenic patients with gram-negative bacteremia.
Overexpression and characterization of the chromosomal aminoglycoside 6'-N-acetyltransferase from Enterococcus faecium
Authors: Wright G D , Ladak P
Published: October 2018

The chromosomal gene aac(6')-Ii, encoding an aminoglycoside 6'-N-acetyltransferase in Enterococcus faecium, renders this organism resistant to moderate levels of many aminoglycoside antibiotics. The ubiquitous presence of aac(6')-Ii in E. faecium complicates the selection of antibiotics for treatment of infections caused by this organism. In view of the importance of this enzyme, we have initiated studies to gain an understanding of its molecular mechanism of acetyl transfer. The AAC(6')-Ii enzyme was overexpressed in Escherichia coli and purified in a simple three-step procedure which yields 55 mg of pure dimeric protein per liter of cell culture. Steady-state kinetic analyses revealed a broad substrate specificity and demonstrated that acetylation occurs exclusively at position N-6'. k(cat)/Km values were on the order of 10(4) M(-1) s(-1), which is relatively low compared to other aminoglycoside-modifying enzymes. In addition, MIC values were positively correlated with k(cat), the rate when the enzyme is saturated with the aminoglycoside substrate, and not with k(cat)/Km, the rate at low aminoglycoside (sub-Km) concentrations. These results describe an enzyme which is not optimally evolved for aminoglycoside inactivation and suggest that this chromosomally encoded enzyme may have an alternate physiological function.
Glycosylated flavones as selective inhibitors of topoisomerase IV
Authors: Bernard F X , Sablé S , Cameron B , Provost J , Desnottes J F , Crouzet J , Blanche F
Published: October 2018

Three flavonoids which promoted Escherichia coli topoisomerase IV-dependent DNA cleavage were isolated from cottonseed flour and identified as quercetin 3-O-beta-D-glucose-[1,6]-O-alpha-L-rhamnose (rutin), quercetin 3-O-beta-D-galactose-[1,6]-O-alpha-L-rhamnose, and quercetin 3-O-beta-D-glucose (isoquercitrin). The most active one (rutin) also inhibited topoisomerase IV-dependent decatenation activity (50% inhibitory concentration, 64 microg/ml) and induced the SOS response of a permeable E. coli strain. Derivatives of quercetin glycosylated at position C-3 were shown to induce two site-specific DNA cleavages of pBR322 DNA, which were mapped by DNA sequence analysis to the gene encoding resistance to tetracycline. Cleavage at these sites was hardly detectable in cleavage reactions with quercetin or fluoroquinolones. None of the three flavonoids isolated from cottonseeds had any stimulatory activity on E. coli DNA gyrase-dependent or calf thymus topoisomerase II-dependent DNA cleavage, and they were therefore specific to topoisomerase IV. These results show that selective inhibitors of topoisomerase IV can be derived from the flavone structure. This is the first report on a DNA topoisomerase inhibitor specific for topoisomerase IV.
Time-restricted feeding schedules modify temporal variation of gentamicin experimental nephrotoxicity
Authors: Beauchamp D , Guimont C , Grenier L , LeBrun M , Tardif D , Gourde P , Bergeron M G , Thibault L , Labrecque G
Published: October 2018

The effect of timing of gentamicin dosing relative to food access periods was evaluated in experimental animals. Female Sprague-Dawley rats were treated for 4 and 10 days with gentamicin (40 mg/kg of body weight/day) intraperitoneally at either 0700, 1300, 1900, or 0100 h according to three food presentation schedules: food was available from 0800 to 1600 h in the first group, from 1600 to 0000 h in the second group, and from 0000 to 0800 h in the last group. Animals were thus subjected to a restricted feeding period. Results indicate that time-restricted feeding schedules displace the peak and the trough of gentamicin-induced renal toxicity, as evaluated by changes in the inhibition of sphingomyelinase activity, cellular regeneration (incorporation of [3H]thymidine into DNA of renal cortex), and blood urea nitrogen and serum creatinine levels, as well as histopathological lesions observed after 10 days of treatment. In fact, the toxicity was minimal when gentamicin was injected during the feeding period, while the maximal toxicity was found when gentamicin was administered during the fasting period. It is concluded that the feeding period can modulate aminoglycoside nephrotoxicity. The time of dosing of gentamicin relative to the time of feeding seems to be a more important modulator of gentamicin nephrotoxicity than the light-dark cycle.
Metabolism of a 5-nitroimidazole in susceptible and resistant isogenic strains of Bacteroides fragilis
Authors: Carlier J P , Sellier N , Rager M N , Reysset G
Published: October 2018

We investigated the metabolism of dimetridazole (1,2-dimethyl-5-nitroimidazole) (DMZ) by the resting cell method in a susceptible strain of Bacteroides fragilis and in the same strain containing the nimA gene, which conferred resistance to 5-nitroimidazole drugs. In both cases, under strict anaerobic conditions DMZ was metabolized without major ring cleavage or nitrate formation. However, one of two distinct metabolic pathways is involved, depending on the susceptibility of the strain. In the susceptible strain, the classical reduction pathway of nitroaromatic compounds is followed at least as far as the nitroso-radical anion, with further formation of the azo-dimer: 5,5'-azobis-(1,2-dimethylimidazole). In the resistant strain, DMZ is reduced to the amine derivative, namely, 5-amino-1,2-dimethylimidazole, preventing the formation of the toxic form of the drug. The specificity of the six-electron reduction of the nitro group, which is restricted to 4- and 5-nitroimidazole, suggests an enzymatic reaction. We thus conclude that nimA and related genes may encode a 5-nitroimidazole reductase.
Pharmacokinetics and safety of oral levofloxacin in human immunodeficiency virus-infected individuals receiving concomitant zidovudine
Authors: Chien S C , Chow A T , Rogge M C , Williams R R , Hendrix C W
Published: October 2018

This phase I, double-blind, randomized, placebo-controlled, parallel-design study was conducted to evaluate the safety and pharmacokinetics of levofloxacin in human immunodeficiency virus (HIV)-infected subjects concomitantly receiving a stable regimen of zidovudine (AZT). Sixteen HIV-infected males with CD4-cell counts ranging from 100 to 550 and not experiencing significant AZT intolerance were enrolled. Subjects received levofloxacin (350 mg of levofloxacin hemihydrate) or a placebo (eight subjects per treatment group) as a single oral dose on day 1, multiple doses every 8 h from days 3 to 9, and a single dose on day 10. On days 1 and 10, an AZT dose (100 mg) was administered concurrently with the study drug. In between these doses, AZT was administered according to the regimen used by the subject prior to entering the study up to a maximum of 500 mg/day. Plasma levofloxacin concentrations were monitored for 36 h after levofloxacin dosing on day 1, immediately prior to the morning doses on days 3 to 9, and for 72 h after dosing on day 10. Plasma AZT concentrations were monitored on day 0 for baseline (for 6 h after the AZT dose) and for 4 h after the AZT doses on days 1 and 10. Levofloxacin was rapidly absorbed (time to maximum plasma concentration, approximately 1.0 h) and extensively distributed in the body with an apparent volume of distribution of approximately 104 liters (approximately 1.34 liters/kg). Steady-state conditions on day 10 were confirmed. Pharmacokinetic profiles of levofloxacin from single doses and multiple (three-times-daily) doses were similar, with a moderate accumulation (observed day 10-to-day 1 ratio of the maximum plasma concentration, approximately 185% versus expected 169%; for the corresponding ratio of the area under the concentration-time curve from 0 to 8 h [AUC(0-8)], the values were observed 217% versus expected 169%) at steady state. Mean average steady-state peak plasma concentration, plasma levofloxacin concentration at the end of the dosing interval, AUC(0-8), terminal half-life, and total body clearance were 7.06 microg/ml, 3.62 microg/ml, 37.4 microg x h/ml, 7.2 h, and 9.4 liters/h (0.12 liters/h/kg), respectively. Pharmacokinetic profiles of levofloxacin in HIV-infected patients did not appear to be affected by the concomitant administration of AZT; nor were AZT pharmacokinetics altered by levofloxacin. Oral administration of 350 mg of levofloxacin hemihydrate every 8 h appeared to be well tolerated by the subjects. There were no apparent differences in adverse events between the two treatment groups. There were no clinically significant changes from baseline in any laboratory parameter or vital sign following treatments observed in this study. The study results suggest that there is no need for levofloxacin dosage adjustment in HIV-seropositive subjects who concomitantly receive AZT.
Enhancement of nitric oxide synthesis by macrophages represents an additional mechanism of action for amphotericin B
Authors: Mozaffarian N , Berman J W , Casadevall A
Published: October 2018

Amphotericin B (AmB) enhanced nitrite synthesis by murine macrophage-like J774.16 cells in a dose-dependent fashion. This effect was retained in the presence of Cryptococcus neoformans capsular polysaccharide, a known virulence factor. AmB and anticapsular antibody increased nitrite synergistically. In all cases, AmB required gamma interferon; C. neoformans cells were unable to elicit nitrite, with or without AmB.
Efficacy and Safety of a 10-Day Course of 400 or 600 Milligrams of Grepafloxacin Once Daily for Treatment of Acute Bacterial Exacerbations of Chronic Bronchitis: Comparison with a 10-Day Course of 500 Milligrams of Ciprofloxacin Twice Daily
Authors: Chodosh S. , Lakshminarayan S. , Swarz H. , Breisch S.
Published: October 2018

A randomized, prospective, double-blind, double-dummy, multicenter study investigated the efficacy and safety of 10 days of oral therapy with grepafloxacin at 400 mg once daily, grepafloxacin at 600 mg once daily, or ciprofloxacin at 500 mg twice daily in 624 patients with acute bacterial exacerbations of chronic bronchitis. At the end of treatment, clinical success (cure or improvement) was achieved for 93% (140 of 151), 88% (137 of 156), and 91% (145 of 160) of patients in the groups receiving grepafloxacin at 400 mg, grepafloxacin at 600 mg, and ciprofloxacin, respectively (clinically evaluable population). At follow-up (14 to 28 days posttreatment), the clinical success rates were 87% (124 of 143), 81% (122 of 151), and 80% (123 of 154) in the groups receiving grepafloxacin at 400 mg and 600 mg and ciprofloxacin, respectively. A total of 379 pathogens were isolated from 290 patients, with the most common isolates being
Moraxella catarrhalis
(21%),
Staphylococcus aureus
(20%),
Haemophilus influenzae
(18%), and
Streptococcus pneumoniae
(7%). For the evaluable population, successful bacteriologic response was obtained at the end of treatment for 96% (92 of 96), 98% (87 of 89), and 92% (82 of 90) of patients receiving grepafloxacin at 400 mg, grepafloxacin at 600 mg, and ciprofloxacin, respectively, and was maintained in 86% (82 of 95), 88% (78 of 89), and 82% (69 of 84) of patients, respectively, at follow-up. All pretreatment
S. pneumoniae
isolates were susceptible to grepafloxacin, but two strains were resistant to ciprofloxacin. All treatments were well tolerated, with the most frequently reported drug-related adverse events being nausea, taste perversion, and headache. All drug-related adverse events in the grepafloxacin groups were mild or moderate in severity. This study demonstrates that 10-day courses of grepafloxacin given at 400 or 600 mg once daily were as effective, clinically and bacteriologically, as ciprofloxacin given at 500 mg twice daily for the treatment of acute bacterial exacerbations of chronic bronchitis.
Antibacterial Efficacy against an In Vivo
Salmonella typhimurium
Infection Model and Pharmacokinetics of a Liposomal Ciprofloxacin Formulation
Authors: Webb Murray S. , Boman Nancy L. , Wiseman David J. , Saxon Dawn , Sutton Kym , Wong Kim F. , Logan Patricia , Hope Michael J.
Published: October 2018

The fluoroquinolone antibiotic ciprofloxacin has been encapsulated into large unilamellar vesicles (LUV) at efficiencies approaching 100%. Drug accumulation proceeded in response to a transmembrane gradient of methylammonium sulfate and occurred concomitantly with the efflux of methylamine. A mechanism for the encapsulation process is described. LUV composed of dipalmitoylphosphatidylcholine-cholesterol (DPPC/chol), distearoylphosphatidylcholine-cholesterol (DSPC/chol), or sphingomyelin-cholesterol (SM/chol) increased the circulation lifetime of ciprofloxacin after intravenous (i.v.) administration by >15-fold. The retention of ciprofloxacin in liposomes in the circulation decreased in the sequence SM/chol > DSPC/chol > DPPC/chol. Increased circulation lifetimes were associated with enhanced delivery of the drug to the livers, spleens, kidneys, and lungs of mice. Encapsulation of ciprofloxacin also conferred significant increases in the longevity of the drug in the plasma after intraperitoneal administration and in the lungs after intratracheal administration in comparison to free ciprofloxacin. The efficacy of a single i.v. administration of an SM/chol formulation of ciprofloxacin was measured in a
Salmonella typhimurium
infection model. At 20 mg of ciprofloxacin per kg of body weight, the encapsulated formulation resulted in 10
3
- to 10
4
-fold fewer viable bacteria in the livers and spleens of infected mice than was observed for animals treated with free ciprofloxacin. These results show the utility of liposomal encapsulation of ciprofloxacin in improving the pharmacokinetics, biodistribution, and antibacterial efficacy of the antibiotic. In addition, these formulations are well suited for i.v., intraperitoneal, and intratracheal or aerosol administration.
Sequencing of Gyrase and Topoisomerase IV Quinolone-Resistance-Determining Regions of
Chlamydia trachomatis
and Characterization of Quinolone-Resistant Mutants Obtained In Vitro
Authors: Dessus-Babus Sophie , Bébéar Cécile M. , Charron Alain , Bébéar Christiane , de Barbeyrac Bertille
Published: October 2018

The L2 reference strain of
Chlamydia trachomatis
was exposed to subinhibitory concentrations of ofloxacin (0.5 μg/ml) and sparfloxacin (0.015 μg/ml) to select fluoroquinolone-resistant mutants. In this study, two resistant strains were isolated after four rounds of selection. The
C. trachomatis
mutants presented with high-level resistance to various fluoroquinolones, particularly to sparfloxacin, for which a 1,000-fold increase in the MICs for the mutant strains compared to the MIC for the susceptible strain was found. The MICs of unrelated antibiotics (doxycycline and erythromycin) for the mutant strains were identical to those for the reference strain. The gyrase (
gyrA
,
gyrB
) and topoisomerase IV (
parC
,
parE
) genes of the susceptible and resistant strains of
C. trachomatis
were partially sequenced. A point mutation was found in the
gyrA
quinolone-resistance-determining region (QRDR) of both resistant strains, leading to a Ser83→Ile substitution (
Escherichia coli
numbering) in the corresponding protein. The
gyrB
,
parC
, and
parE
QRDRs of the resistant strains were identical to those of the reference strain. These results suggest that in
C. trachomatis
, DNA gyrase is the primary target of ofloxacin and sparfloxacin.
Structure-In Vitro Activity Relationships of Pentamidine Analogues and Dication-Substituted Bis-Benzimidazoles as New Antifungal Agents
Authors: Del Poeta Maurizio , Schell Wiley A. , Dykstra Christine C. , Jones Susan , Tidwell Richard R. , Czarny Agnieszka , Bajic Miroslav , Bajic Marina , Kumar Arvind , Boykin David , Perfect John R.
Published: October 2018

Twenty analogues of pentamidine, 7 primary metabolites of pentamidine, and 30 dicationic substituted bis-benzimidazoles were screened for their inhibitory and fungicidal activities against
Candida albicans
and
Cryptococcus neoformans
. A majority of the compounds had MICs at which 80% of the strains were inhibited (MIC
80
s) comparable to those of amphotericin B and fluconazole. Unlike fluconazole, many of these compounds were found to have potent fungicidal activity. The most potent compound against
C. albicans
had an MIC
80
of ≤0.09 μg/ml, and the most potent compound against
C. neoformans
had an MIC
80
of 0.19 μg/ml. Selected compounds were also found to be active against
Aspergillus fumigatus
,
Fusarium solani
,
Candida
species other than
C. albicans
, and fluconazole-resistant strains of
C. albicans
and
C. neoformans
. It is clear from the data presented here that further studies on the structure-activity relationships, mechanisms of action and toxicities, and in vivo efficacies of these compounds are warranted to determine their clinical potential.
Rifampin Concentrations in Various Compartments of the Human Brain: A Novel Method for Determining Drug Levels in the Cerebral Extracellular Space
Authors: Mindermann Thomas , Zimmerli Werner , Gratzl Otmar
Published: October 2018

Antimicrobial therapy for brain infections is notoriously difficult because of the limited extent of knowledge about drug penetration into the brain. Therefore, we determined the penetration of rifampin into various compartments of the human brain, including the cerebral extracellular space (CES). Patients undergoing craniotomy for resection of primary brain tumors were given a standard dose of 600 mg of rifampin intravenously before the operation. A microdialysis probe (10 by 0.5 mm) was inserted into the cortex distantly from the resection and was perfused with two different rifampin solutions. Rifampin concentrations in the CES were calculated by the no-net-flux method. Intraoperatively, samples were taken from brain tumor tissue, perifocal tissue, and normal brain tissue in the case of pole resections. Rifampin concentrations in the various samples were determined by using a bioassay with
Sarcinea lutea
. In the various compartments, rifampin concentrations were highest within tumors (1.37 ± 1.34 μg/ml;
n
= 8), followed by the perifocal region (0.62 ± 0.67 μg/ml;
n
= 8), the CES (0.32 ± 0.11 μg/ml;
n
= 6), and normal brain tissue (0.29 ± 0.15 μg/ml;
n
= 7). Rifampin concentrations in brain tumors do not adequately reflect concentrations in normal brain tissue or in the CES. Rifampin concentrations in the CES, as determined by microdialysis, are the most reproducible, and the least scattered, of the values for all compartments evaluated. Rifampin concentrations in all compartments exceed the MIC for staphylococci and streptococci. However, CES concentrations may be below the MICs for some mycobacterial strains.
Mechanism of Fluconazole Resistance in
Candida krusei
Authors: Orozco Alison S. , Higginbotham Lindsey M. , Hitchcock Christopher A. , Parkinson Tanya , Falconer Derek , Ibrahim Ashraf S. , Ghannoum Mahmoud A. , Filler Scott G.
Published: October 2018

The mechanisms of fluconazole resistance in three clinical isolates of
Candida krusei
were investigated. Analysis of sterols of organisms grown in the absence and presence of fluconazole demonstrated that the predominant sterol of
C. krusei
is ergosterol and that fluconazole inhibits 14α-demethylase in this organism. The 14α-demethylase activity in cell extracts of
C. krusei
was 16- to 46-fold more resistant to inhibition by fluconazole than was 14α-demethylase activity in cell extracts of two fluconazole-susceptible strains of
Candida albicans
. Comparing the carbon monoxide difference spectra of microsomes from
C. krusei
with those of microsomes from
C. albicans
indicated that the total cytochrome P-450 content of
C. krusei
is similar to that of
C. albicans
. The Soret absorption maximum in these spectra was located at 448 nm for
C. krusei
and at 450 nm for
C. albicans
. Finally, the fluconazole accumulation of two of the
C. krusei
isolates was similar to if not greater than that of
C. albicans
. Thus, there are significant qualitative differences between the 14α-demethylase of
C. albicans
and
C. krusei
. In addition, fluconazole resistance in these strains of
C. krusei
appears to be mediated predominantly by a reduced susceptibility of 14α-demethylase to inhibition by this drug.
Structure-Based Design of Novel Dihydroalkoxybenzyloxopyrimidine Derivatives as Potent Nonnucleoside Inhibitors of the Human Immunodeficiency Virus Reverse Transcriptase
Authors: Sudbeck Elise A. , Mao Chen , Vig Rakesh , Venkatachalam T. K. , Tuel-Ahlgren Lisa , Uckun Fatih M.
Published: October 2018

Two highly potent dihydroalkoxybenzyloxopyrimidine (DABO) derivatives targeting the nonnucleoside inhibitor (NNI) binding site of human immunodeficiency virus (HIV) reverse transcriptase (RT) have been designed based on the structure of the NNI binding pocket and tested for anti-HIV activity. Our lead DABO derivative, 5-isopropyl-2-[(methylthiomethyl)thio]-6-(benzyl)-pyrimidin-4-(1
H
)-one, elicited potent inhibitory activity against purified recombinant HIV RT and abrogated HIV replication in peripheral blood mononuclear cells at nanomolar concentrations (50% inhibitory concentration, <1 nM) but showed no detectable cytotoxicity at concentrations as high as 100 μM.
Pharmacodynamic Evaluation of Factors Associated with the Development of Bacterial Resistance in Acutely Ill Patients during Therapy
Authors: Thomas Jennifer K. , Forrest Alan , Bhavnani Sujata M. , Hyatt Judith M. , Cheng Angela , Ballow Charles H. , Schentag Jerome J.
Published: October 2018

The selection of bacterial resistance was examined in relationship to antibiotic pharmacokinetics (PK) and organism MICs in the patients from four nosocomial lower respiratory tract infection clinical trials. The evaluable database included 107 acutely ill patients, 128 pathogens, and five antimicrobial regimens. Antimicrobial pharmacokinetics were characterized by using serum concentrations, and culture and sensitivity tests were performed daily on tracheal aspirates to examine resistance. Pharmacodynamic (PD) models were developed to identify factors associated with the probability of developing bacterial resistance. Overall, in 32 of 128 (25%) initially susceptible cases resistance developed during therapy. An initial univariate screen and a classification and regression tree analysis identified the ratio of the area under the concentration-time curve from 0 to 24 h to the MIC (AUC0–24/MIC) as a significant predictor of the development of resistance (P< 0.001). The final PK/PD model, a variant of the Hill equation, demonstrated that the probability of developing resistance during therapy increased significantly when antimicrobial exposure was at an AUC0–24/MIC ratio of less than 100. This relationship was observed across all treatments and within all organism groupings, with the exception of β-lactamase-producing gram-negative organisms (consistent with type I β-lactamase producers) treated with β-lactam monotherapy. Combination therapy resulted in much lower rates of resistance than monotherapy, probably because all of the combination regimens examined had an AUC0–24/MIC ratio in excess of 100. In summary, the selection of antimicrobial resistance appears to be strongly associated with suboptimal antimicrobial exposure, defined as an AUC0–24/MIC ratio of less than 100.
Comparative In Vitro Activities and Postantibiotic Effects of the Oxazolidinone Compounds Eperezolid (PNU-100592) and Linezolid (PNU-100766) versus Vancomycin against
Staphylococcus aureus
, Coagulase-Negative Staphylococci,
Enterococcus faecalis
, and
Enterococcus faecium
Authors: Rybak Michael J. , Cappelletty Diane M. , Moldovan Tabitha , Aeschlimann Jeffrey R. , Kaatz Glenn W.
Published: October 2018

The activities of the oxazolidinone antibacterial agents eperezolid (PNU-100592) and linezolid (PNU-100766) were compared with that of vancomycin against clinical isolates of methicillin-susceptible and -resistant
Staphylococcus aureus
(
n
= 200), coagulase-negative staphylococci (
n
= 100), and vancomycin-susceptible and -resistant
Enterococcus faecalis
and
Enterococcus faecium
(
n
= 50). Eperezolid and linezolid demonstrated good in vitro inhibitory activity, regardless of methicillin susceptibility for staphylococci (MIC at which 90% of the isolates are inhibited [MIC
90
] range, 1 to 4 μg/ml) or vancomycin susceptibility for enterococci (MIC
90
range, 1 to 4 μg/ml). In time-kill studies, eperezolid and linezolid were bacteriostatic in action. A postantibiotic effect of 0.8 ± 0.5 h was demonstrated for both eperezolid and linezolid against
S. aureus
,
S. epidermidis
,
E. faecalis
, and
E. faecium.
Role of ABC Transporters in Aureobasidin A Resistance
Authors: Ogawa Atsuko , Hashida-Okado Takashi , Endo Masahiro , Yoshioka Hirofumi , Tsuruo Takashi , Takesako Kazutoh , Kato Ikunoshin
Published: October 2018

Aureobasidin A (AbA) has strong antifungal effects arising from an unusual mechanism. We show that AbA interacts with ATP-binding cassette (ABC) transporters in yeast and mammalian cells. We isolated a gene of
Saccharomyces cerevisiae
that conferred resistance to AbA when the gene was present in multiple copies. The gene was identical to
YOR1/YRS1
, which confers resistance to oligomycin, reveromycin, and organic anions, none of which have structures similar to that of AbA. We also isolated an
aur3
R
recessive mutant of
S. cerevisiae
with increased resistance to AbA. Northern hybridization showed that the
aur3
R
mutant expressed not only
YOR1
but also the ABC transporter-encoding gene
PDR5
at high levels. Genetic studies showed that the
aur3
R
mutant had a mutation in the
PDR1
gene, which encodes a transcriptional regulator of
PDR5
and
YOR1
. Analysis of a
yor1
disruptant of the
aur3/pdr1
mutant showed that both the functional
YOR1
gene and the mutation in
PDR1
were necessary for AbA resistance. These results suggest that
YOR1
is more important than
PDR5
for AbA resistance. We found in
Candida albicans
a novel gene whose sequence was similar to the sequence of
YOR1
in
S. cerevisiae
. The amino acid sequence of the
C. albicans YOR1
homolog showed no significant similarity to the sequences of
CDR1
and
CDR2
, which are ABC transporters of
C. albicans
. Furthermore, AbA inhibited the efflux of the anticancer agent vincristine through P glycoproteins in cancer cells with multidrug resistance.
In Vitro and In Vivo Antifungal Activity of Amphotericin B Lipid Complex: Are Phospholipases Important?
Authors: Swenson Christine E. , Perkins Walter R. , Roberts Patricia , Ahmad Imran , Stevens Rachel , Stevens David A. , Janoff Andrew S.
Published: October 2018

Amphotericin B lipid complex for injection (ABLC) is a suspension of amphotericin B complexed with the lipids
l
-α-dimyristoylphosphatidylcholine (DMPC) and
l
-α-dimyristoylphosphatidylglycerol. ABLC is less toxic than amphotericin B deoxycholate (AmB-d), while it maintains the antifungal activity of AmB-d. Active amphotericin B can be released from ABLC by exogenously added (snake venom, bacteria, or
Candida
-derived) phospholipases or by phospholipases derived from activated mammalian vascular tissue (rat arteries). Such extracellular phospholipases are capable of hydrolyzing the major lipid in ABLC. Mutants of
C. albicans
that were resistant to ABLC but not AmB-d in vitro were deficient in extracellular phospholipase activity, as measured on egg yolk agar or as measured by their ability to hydrolyze DMPC in ABLC. ABLC was nevertheless effective in the treatment of experimental murine infections produced by these mutants. Isolates of
Aspergillus
species, apparently resistant to ABLC in vitro (but susceptible to AmB-d), were also susceptible to ABLC in vivo. We suggest that routine in vitro susceptibility tests with ABLC itself as the test material may not accurately predict the in vivo activity of ABLC and that the enhanced therapeutic index of ABLC relative to that of AmB-d in vivo may be due, in part, to the selective release of active amphotericin B from the complex at sites of fungal infection through the action of fungal or host cell-derived phospholipases.
Characterization of the Antimonial Antileishmanial Agent Meglumine Antimonate (Glucantime)
Authors: Roberts William L. , McMurray Walter J. , Rainey Petrie M.
Published: October 2018

Meglumine antimonate (Glucantime), a drug of choice for the treatment of leishmaniasis, is produced by the reaction of pentavalent antimony with
N
-methyl-
d
-glucamine, a carbohydrate derivative. We investigated the structure and composition of meglumine antimonate, which remain poorly understood, despite 50 years of use. Measurement of the antimony content of meglumine antimonate powder indicated a 1:1.37 molar ratio of antimony to
N
-methyl-
d
-glucamine. Osmolality measurements performed with meglumine antimonate solutions demonstrated an average of 1.43 antimony atoms per molecule of meglumine antimonate. The osmolality of a 1:10 dilution of stock meglumine antimonate increased by 45% over 8 days, suggesting hydrolysis to less complex species. A comparison of the proton nuclear magnetic resonance spectra of
N
-methyl-
d
-glucamine and meglumine antimonate revealed an increase in complexity in the latter but with all of the resonances of the former still being evident, consistent with the presence of coordination complexes between antimony and each of the
N
-methyl-
d
-glucamine hydroxyls. Fast atom bombardment and electrospray ionization mass spectrometry coupled with several derivatization procedures provided evidence that up to four
N
-methyl-
d
-glucamine hydroxyls are coordinated with each antimony. A series of oligomers were observed. The major moiety has a molecular mass of 507 atomic mass units and consists of NMG-Sb-NMG, where Sb represents antimony and NMG represents
N
-methyl-
d
-glucamine. Additional species containing up to four antimony atoms and five
N
-methyl-
d
-glucamine moieties and corresponding to the general form (NMG-Sb)

n

-NMG are also present. These results suggest that this agent is a complex mixture that exists in equilibrium in aqueous solution.
A New High-Level Gentamicin Resistance Gene,
aph(2")-Id
, in
Enterococcus
spp
Authors: Tsai Shane F. , Zervos Marcus J. , Clewell Don B. , Donabedian Susan M. , Sahm Daniel F. , Chow Joseph W.
Published: October 2018

Enterococcus casseliflavus
UC73 is a clinical blood isolate with high-level resistance to gentamicin. DNA preparations from UC73 failed to hybridize with intragenic probes for
aac(6′)-Ie-aph(2")-Ia
and
aph(2")-Ic
. A 4-kb fragment from UC73 was cloned and found to confer resistance to gentamicin in
Escherichia coli
DH5α transformants. Nucleotide sequence analysis revealed the presence of a 906-bp open reading frame whose deduced amino acid sequence had a region with homology to the aminoglycoside-modifying enzyme APH(2")-Ic and to the C-terminal domain of the bifunctional enzyme AAC(6′)-APH(2"). The gene is designated
aph(2")-Id
, and its observed phosphotransferase activity is designated APH(2")-Id. A PCR-generated intragenic probe hybridized to the genomic DNA from 17 of 118 enterococcal clinical isolates (108 with high-level gentamicin resistance) from five hospitals. All 17 were vancomycin-resistant
Enterococcus faecium
isolates, and pulsed-field typing revealed three distinct clones. The combination of ampicillin plus either amikacin or neomycin exhibited synergistic killing against
E. casseliflavus
UC73. Screening and interpretation of high-level aminoglycoside resistance in enterococci may need to be modified to include detection of APH(2")-Id.
Tetracycline Resistance in
Salmonella enterica
subsp.
enterica
Serovar Dublin
Authors: Frech Gabriele , Schwarz Stefan
Published: October 2018

The 47-kbp plasmid pGFT1 from
Salmonella enterica
subsp.
enterica
serovar Dublin mediated tetracycline resistance via a
tet
(A) gene located on an integrated copy of a Tn
1721
-analogous transposon. The integration site of the transposon was located within the reading frame of a
fip
gene. Plasmid pGFT1 was shown to be conjugative and to be able to replicate and express tetracycline resistance in
Escherichia coli.
S-1153 Inhibits Replication of Known Drug-Resistant Strains of Human Immunodeficiency Virus Type 1
Authors: Fujiwara Tamio , Sato Akihiko , El-Farrash Mohamed , Miki Shigeru , Abe Kenji , Isaka Yoshitaka , Kodama Makoto , Wu Yaming , Chen Lan Bo , Harada Hiroshi , Sugimoto Hirohiko , Hatanaka Masakazu , Hinuma Yorio
Published: October 2018

S-1153 is a new imidazole compound that inhibits human immunodeficiency virus (HIV) type 1 (HIV-1) replication by acting as a nonnucleoside reverse transcriptase inhibitor (NNRTI). This compound inhibits replication of HIV-1 strains that are resistant to nucleoside and nonnucleoside reverse transcriptase inhibitors. S-1153 has a 50% effective concentration in the range of 0.3 to 7 ng/ml for strains with single amino acid substitutions that cause NNRTI resistance, including the Y181C mutant, and also has potent activity against clinical isolates. The emergence of S-1153-resistant variants is slower than that for nevirapine, and S-1153-resistant variants contained at least two amino acid substitutions, including F227L or L234I. S-1153-resistant variants are still sensitive to the nucleoside reverse transcriptase inhibitors zidovudine (AZT) and lamivudine. In a mouse and MT-4 (human T-cell line) in vivo HIV replication model, S-1153 and AZT administered orally showed a marked synergy for the inhibition of HIV-1 replication. S-1153 shows a significant accumulation in lymph nodes, where most HIV-1 infection is thought to occur. S-1153 may be an appropriate candidate for two- to three-drug combination therapy for HIV infection.
Pharmacokinetics of Sparfloxacin in the Serum and Vitreous Humor of Rabbits: Physicochemical Properties That Regulate Penetration of Quinolone Antimicrobials
Authors: Liu Weiguo , Liu Qing Feng , Perkins Ruth , Drusano George , Louie Arnold , Madu Assumpta , Mian Umar , Mayers Martin , Miller Michael H.
Published: October 2018

We have used a recently described animal model to characterize the ocular pharmacokinetics of sparfloxacin in vitreous humor of uninfected albino rabbits following systemic administration and direct intraocular injection. The relationships of lipophilicity, protein binding, and molecular weight to the penetration and elimination of sparfloxacin were compared to those of ciprofloxacin, fleroxacin, and ofloxacin. To determine whether elimination was active, elimination rates following direct injection with and without probenecid or heat-killed bacteria were compared. Sparfloxacin concentrations were measured in the serum and vitreous humor by a biological assay. Protein binding and lipophilicity were determined, respectively, by ultrafiltration and oil-water partitioning. Pharmacokinetic parameters were characterized with RSTRIP, an iterative, nonlinear, weighted, least-squares-regression program. The relationship between each independent variable and mean quinolone concentration or elimination rate in the vitreous humor was determined by multiple linear regression. The mean concentration of sparfloxacin in the vitreous humor was 59.4% ± 12.2% of that in serum. Penetration of sparfloxacin, ciprofloxacin, fleroxacin, and ofloxacin into, and elimination from, the vitreous humor correlated with lipophilicity (
r
2
> 0.999). The linear-regression equation describing this relationship was not improved by including the inverse of the square root of the molecular weight and/or the degree of protein binding. Elimination rates for each quinolone were decreased by the intraocular administration of probenecid. Heat-killed
Staphylococcus epidermidis
decreased the rate of elimination of fleroxacin. Penetration of sparfloxacin into the noninflamed vitreous humor was greater than that of any quinolone previously examined. There was an excellent correlation between lipophilicity and vitreous entry or elimination for sparfloxacin as well as ciprofloxacin, fleroxacin, and ofloxacin. There are two modes of quinolone translocation into and out of the vitreous humor: diffusion into the eye and both diffusion and carrier-mediated elimination out of the vitreous humor.
Different Erythromycin Resistance Mechanisms in Group C and Group G Streptococci
Authors: Kataja Janne , Seppälä Helena , Skurnik Mikael , Sarkkinen Hannu , Huovinen Pentti
Published: October 2018

Different mechanisms of erythromycin resistance predominate in group C and G streptococcus (GCS and GGS, respectively) isolates collected from 1992 to 1995 in Finland. Of the 21 erythromycin-resistant GCS and 32 erythromycin-resistant GGS isolates, 95% had the
mefA
or
mefE
drug efflux gene and 94% had the
ermTR
methylase gene, respectively.
Mode of Action of Sulfanilyl Fluoroquinolones
Authors: Alovero Fabiana , Nieto Marcelo , Mazzieri Maria Rosa , Then Rudolf , Manzo Ruben H.
Published: October 2018

The mode of action of sulfanilyl fluoroquinolones (NSFQs) was investigated with NSFQ-104, NSFQ-105, and some structurally related compounds. Evidence arising from interactions with
p
-aminobenzoic acid and trimethoprim suggested that a sulfonamidelike mechanism of action makes little or no contribution to the in vitro activity of NSFQs. NSFQ-105 showed an activity that inhibits gyrase-catalyzed DNA supercoiling that is similar to the activity of other fluoroquinolones. Also, NSFQ-105 uptake was decreased by the presence of Mg
2+
and increased by a lower pH. These results indicate that NSFQs having only one ionizable group could exhibit more favorable kinetics of access to the bacterial cell than zwitterionic fluoroquinolones.
Susceptibilities of
Legionella
spp. to Newer Antimicrobials In Vitro
Authors: Schülin T. , Wennersten C. B. , Ferraro M. J. , Moellering R. C. , Eliopoulos G. M.
Published: October 2018

The in vitro activities of 13 antimicrobial agents against 30 strains of
Legionella
spp. were determined. Rifapentine, rifampin, and clarithromycin were the most potent agents (MICs at which 90% of isolates are inhibited [MIC
90
s], ≤0.008 μg/ml). The ketolide HMR 3647 and the fluoroquinolones levofloxacin and BAY 12-8039 (MIC
90
s, 0.03 to 0.06 μg/ml) were more active than erythromycin A or roxithromycin. The MIC
90
s of dalfopristin-quinupristin and linezolid were 0.5 and 8 μg/ml, respectively. Based on class characteristics and in vitro activities, several of these agents may have potential roles in the treatment of
Legionella
infections.
Entry of Sanfetrinem into Human Polymorphonuclear Granulocytes and Its Cell-Associated Activity against Intracellular, Penicillin-Resistant
Streptococcus pneumoniae
Authors: Cuffini Anna Maria , Tullio Vivian , Bonino Alessandro , Allocco Alessandra , Palarchio Angela Ianni , Carlone Nicola A.
Published: October 2018

The entry of antibiotics into phagocytes is necessary for activity against intracellular pathogens. The ability of sanfetrinem, the first member of a new class of antibiotics, to penetrate human polymorphonuclear granulocytes and its consequences upon subsequent phagocytosis and killing of ingested penicillin-resistant
Streptococcus pneumoniae
have been evaluated. Sanfetrinem penetrated into human polymorphonuclear leukocytes (PMNs) at all concentrations tested, with cellular concentration/extracellular concentration ratios of 6.6 to 5.03 and 4.21 when sanfetrinem was used at 0.25 to 0.5 and 1 μg/ml, respectively, within 30 min of incubation. The uptake was complete within 5 min and was not energy dependent, since it was not affected by cell viability, environmental temperature, or the addition of a metabolic inhibitor. At a concentration of one-half the MIC, sanfetrinem significantly enhanced human PMN phagocytosis and increased intracellular bactericidal activity against penicillin-resistant
S. pneumoniae
. Following preexposure of PMNs to a concentration of one-half the MIC of sanfetrinem, there was a significant increase in both phagocytosis and killing compared with that for the controls, indicating the ability of sanfetrinem to interact with biological membranes and remain active within PMNs. Preexposure of streptococci to sanfetrinem made penicillin-resistant
S. pneumoniae
more susceptible to the bactericidal mechanisms of human PMNs than untreated organisms.
Ciprofloxacin Induces an Immunomodulatory Stress Response in Human T Lymphocytes
Authors: Riesbeck Kristian , Forsgren Arne , Henriksson Agnethe , Bredberg Anders
Published: October 2018

Exposure of cells to adverse environmental conditions invokes a genetically programmed series of events resulting in the induction of specific genes. The fluoroquinolone antibiotic ciprofloxacin has recently been reported to upregulate interleukin-2 (IL-2) gene induction. In the present investigation, the effect of ciprofloxacin at supratherapeutic concentrations on immediate-early (<2 h) gene expression in primary human peripheral blood lymphocytes was studied with Northern blots. In addition, transcriptional activity of IL-2 and metallothionein enhancer and promoter regions and transcription factors AP-1, NF-κB, and NF-AT were analyzed by chloramphenicol acetyltransferase (CAT) and electrophoretic mobility shift assays, respectively. The concentration of c-fos, c-jun, c-myc,junB, andfra-1 mRNAs was increased in activated peripheral blood lymphocytes incubated with ciprofloxacin compared to that in untreated controls. Ciprofloxacin increased CAT activity in stimulated lymphocytes transfected with plasmids containing either the IL-2 or metallothionein enhancer. Furthermore, among the transcription factors tested, AP-1 activity was increased in stimulated purified T helper lymphocytes incubated with ciprofloxacin compared to drug-free controls. Taken together, ciprofloxacin increased the levels of immediate-early transcripts, enhanced IL-2 and metallothionein promoter induction, and upregulated AP-1 concentrations in primary lymphocytes, reflecting a program commonly observed in mammalian stress responses.
vanA
Gene Cluster in a Vancomycin-Resistant Clinical Isolate of
Bacillus circulans
Authors: Ligozzi Marco , Lo Cascio Giuliana , Fontana Roberta
Published: October 2018

We report on the cloning and sequencing of the
vanA
gene cluster present in the glycopeptide-resistant clinical isolate
Bacillus circulans
VR0709 (R. Fontana, M. Ligozzi, C. Pedrotti, E. M. Padovani, and G. Cornaglia, Eur. J. Clin. Microbiol. Infect. Dis. 16:473–474, 1997). The presence of a
vanA
-related gene in VR0709 was demonstrated in a PCR assay which permitted the specific amplification of an internal segment of
vanA
. Southern blotting suggested that the
vanA
gene was located in the chromosome in a 7.6-kb
Eco
RI fragment. DNA sequence analysis revealed the presence of all seven genes of the
vanA
cluster (
vanR
,
vanS
,
vanH
,
vanA
,
vanX
,
vanY
, and
vanZ
). The degree of identity between homologous proteins encoded by Tn
1546
and the chromosome of
B. circulans
VR0709 ranged from 87 to 95%. Neither PCR nor Southern blotting with specific primers and probes, respectively, showed the presence of open reading frames (ORFs) 1 and 2 which encode the transposase and the resolvase of Tn
1546
, respectively, the transposon found to carry the
vanA
gene cluster in enterococci. Determination of the sequences of the flanking regions of the
van
gene cluster of
B. circulans
revealed perfect inverted repeats of 10 bp which delineated a 9.2-kb region containing the
van
gene cluster and an ORF which encoded a putative protein (178 residues) which displayed a low level of identity (28%) to the resolvase of Tn
1546
. These results suggest that glycopeptide resistance in
B. circulans
VR0709 is associated with the acquisition of a
vanA
gene cluster which shows a high degree of homology with that of enterococci. In
B. circulans
, however, the cluster is not carried by Tn
1546
and is borne by the chromosome.
Detection of Tn
917
-Like Sequences within a Tn
916
-like Conjugative Transposon (Tn
3872
) in Erythromycin-Resistant Isolates of
Streptococcus pneumoniae
Authors: McDougal Linda K. , Tenover Fred C. , Lee Linda N. , Rasheed J. Kamile , Patterson Jan E. , Jorgensen James H. , LeBlanc Donald J.
Published: October 2018

A series of macrolide-lincosamide-streptogramin B (MLS)-resistant pneumococcal isolates of a variety of serotypes was examined and was found to contain Tn
917
-like elements by DNA-DNA hybridization. Like Tn
1545
, Tn
917
also encodes an
ermAM
gene but does not mediate resistance to other antimicrobial agents. Furthermore, nucleotide sequence analyses of the DNAs flanking three of the Tn
917
-like elements revealed that they were inserted into
orf9
of a Tn
916
-like element in a composite transposon-like structure (Tn
3872
). Other MLS-resistant strains appeared to contain Tn
1545
-like elements that had suffered a deletion of sequences including the
aphA-3
sequences responsible for kanamycin resistance. Thus, the MLS resistance phenotype in pneumococci appears to be mediated by the
ermAM
present on a much wider variety of genetic elements than was previously appreciated.