bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacokinetics of Dapsone Administered Daily and Weekly in Human Immunodeficiency Virus-Infected Children
Authors: Mirochnick Mark , Cooper Ellen , McIntosh Ken , Xu Jing , Lindsey Jane , Jacobus David , Mofenson Lynne , Sullivan John L. , Dankner Wayne , Frenkel Lisa M. , Nachman Sharon , Wara Diane W. , Johnson Daniel , Bonagura Vincent R. , Rathore Mobeen H. , Cunningham Coleen K. , McNamara James
Published: October 2018

Although dapsone is a commonly used alternative agent for prophylaxis againstPneumocystis cariniipneumonia in children intolerant to trimethoprim-sulfamethoxazole, there are few data that describe dapsone pharmacokinetics in children. We studied dapsone pharmacokinetics in 30 children (median age, 2.8 years; age range, 0.3 to 12 years) receiving a new proprietary liquid preparation by three dosing regimens (1 mg/kg of body weight daily, 2 mg/kg daily, or 4 mg/kg weekly). Dosing of children with 2 mg/kg daily or 4 mg/kg weekly resulted in peak concentrations equivalent to those reached in adults receiving 100-mg tablets daily. For the entire population, the median half-life was 22.2 h (range, 7.1 to 40.3 h), the median oral clearance was 0.0365 liter/kg/h (range, 0.0104 to 0.1021 liter/kg/h), and the median oral apparent volume of distribution was 1.13 liters/kg (range, 0.50 to 2.32 liters/kg). The median dapsone oral clearance was significantly increased in those infants less than 2 years of age compared to the oral clearance in those over 2 years of age (0.0484 versus 0.0278 liter/kg/h;P= 0.011). These data suggest that absorption of this liquid preparation is adequate and that the concentrations in the sera of children receiving 2 mg/kg daily or 4 mg/kg weekly are equivalent to those seen in adults receiving standard dapsone dosing. Dapsone oral clearance appears to be increased in children under 2 years of age.
Accumulation of 3-Ketosteroids Induced by Itraconazole in Azole-Resistant ClinicalCandida albicansIsolates
Authors: Marichal Patrick , Gorrens Jos , Laurijssens Leen , Vermuyten Karen , Van Hove Carl , Le Jeune Ludo , Verhasselt Peter , Sanglard Dominique , Borgers Marcel , Ramaekers Frans C. S. , Odds Frank , Vanden Bossche Hugo
Published: October 2018

The effects of itraconazole on ergosterol biosynthesis were investigated in a series of 16 matched clinicalCandida albicansisolates which had been previously analyzed for mechanisms of resistance to azoles (D. Sanglard, K. Kuchler, F. Ischer, J. L. Pagani, M. Monod, and J. Bille, Antimicrob. Agents Chemother., 39:2378–2386, 1995). Under control conditions, all isolates contained ergosterol as the predominant sterol, except two strains (C48 and C56). In isolates C48 and C56, both less susceptible to azoles than their parent, C43, substantial concentrations (20 to 30%) of 14α-methyl-ergosta-8,24(28)-diene-3β,6α-diol (3,6-diol) were found. Itraconazole treatment of C43 resulted in a dose-dependent inhibition of ergosterol biosynthesis (50% inhibitory concentration, 2 nM) and accumulation of 3,6-diol (up to 60% of the total sterols) together with eburicol, lanosterol, obtusifoliol, 14α-methyl-ergosta-5,7,22,24(28)-tetraene-3βol, and 14α-methyl-fecosterol. In strains C48 and C56, no further increase of 3,6-diol was observed after exposure to itraconazole. Ergosterol synthesis was less sensitive to itraconazole inhibition, as was expected for these azole-resistant isolates which overexpress ATP-binding cassette transporter genesCDR1andCDR2. In addition to 3,6-diol, substantial amounts of obtusifolione were found after exposure to itraconazole. This toxic 3-ketosteroid was demonstrated previously to accumulate after itraconazole treatment inCryptococcus neoformansandHistoplasma capsulatumbut has not been reported inCandidaisolates. Accumulation of obtusifolione correlated with nearly complete growth inhibition in these azole-resistant strains compared to that found in the susceptible parent strain, although the onset of growth inhibition only occurred at higher concentrations of itraconazole.ERG25andERG26are the only genes assigned to the 4-demethylation process, of which the 3-ketoreductase is part. To verify whether mutations in theseERG25genes contributed to obtusifolione accumulation, their nucleotide sequences were determined in all three related isolates. No mutations inERG25alleles of isolates C48 and C56 were found, suggesting that this gene is not involved in obtusifolione accumulation. The molecular basis for the accumulation of this sterol in these two strains remains to be established.
Genetic Analysis of Azole Resistance by Transposon Mutagenesis in
Saccharomyces cerevisiae
Authors: Kontoyiannis D. P.
Published: October 2018

The increasing resistance of
Candida
species to fluconazole is cause for concern. To determine the molecular mechanisms involved in resistance to fluconazole, I used a scheme of transposon mutagenesis in
Saccharomyces cerevisiae
, a genetically tractable yeast that is closely related to
Candida albicans
. This technique, which permits the generation and analysis of multiple random Tn
3
::
LEU2
::
lacZ
fusions, can be used as a disruption mutagen (N. B. Burns et al., Genes Dev. 8:1087–1105, 1994). By using the Tn
3
::
LEU2
::
lacZ
library as a disruption mutagen, I found recessive mutations in genes that were previously found to be involved in azole resistance, e.g.,
PDR5
and
CPR1
, and in genes previously found to be involved in azole sensitivity, e.g.,
ERG3
. This approach also enabled me to identify recessive mutations in three genes not previously known to be involved in azole sensitivity. Two of the genes,
ADA3
and
SPT7
, are general transcriptional regulators; the third,
YMR034c
, is a putative sterol transporter. Finally, by screening the Tn
3
::
LEU2
::
lacZ
library for
lacZ
fusions induced by a low concentration of fluconazole, I identified genes known to be induced by azoles as well as a variety of other genes not previously known to be induced by the drug. In conclusion, transposon mutagenesis is a promising screening tool for use in identifying novel drug targets and in uncovering the mechanisms involved in the response of
S. cerevisiae
to antifungal drugs.
Pharmacokinetics of [
14
C]Abacavir, a Human Immunodeficiency Virus Type 1 (HIV-1) Reverse Transcriptase Inhibitor, Administered in a Single Oral Dose to HIV-1-Infected Adults: a Mass Balance Study
Authors: McDowell James A. , Chittick Gregory E. , Ravitch Joshua R. , Polk Ronald E. , Kerkering Thomas M. , Stein Daniel S.
Published: October 2018

Abacavir (1592U89) {(−)-(1
S
, 4
R
)-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol} is a 2′-deoxyguanosine analogue with potent activity against human immunodeficiency virus (HIV) type 1. To determine the metabolic profile, routes of elimination, and total recovery of abacavir and metabolites in humans, we undertook a phase I mass balance study in which six HIV-infected male volunteers ingested a single 600-mg oral dose of abacavir including 100 μCi of [
14
C]abacavir. The metabolic disposition of the drug was determined through analyses of whole-blood, plasma, urine, and stool samples, collected for a period of up to 10 days postdosing, and of cerebrospinal fluid (CSF), collected up to 6 h postdosing. The radioactivity from abacavir and its two major metabolites, a 5′-carboxylate (2269W93) and a 5′-glucuronide (361W94), accounted for the majority (92%) of radioactivity detected in plasma. Virtually all of the administered dose of radioactivity (99%) was recovered, with 83% eliminated in urine and 16% eliminated in feces. Of the 83% radioactivity dose eliminated in the urine, 36% was identified as 361W94, 30% was identified as 2269W93, and 1.2% was identified as abacavir; the remaining 15.8% was attributed to numerous trace metabolites, of which <1% of the administered radioactivity was 1144U88, a minor metabolite. The peak concentration of abacavir in CSF ranged from 0.6 to 1.4 μg/ml, which is 8 to 20 times the mean 50% inhibitory concentration for HIV clinical isolates in vitro (0.07 μg/ml). In conclusion, the main route of elimination for oral abacavir in humans is metabolism, with <2% of a dose recovered in urine as unchanged drug. The main route of metabolite excretion is renal, with 83% of a dose recovered in urine. Two major metabolites, the 5′-carboxylate and the 5′-glucuronide, were identified in urine and, combined, accounted for 66% of the dose. Abacavir showed significant penetration into CSF.
Incidence and Characterization of Integrons, Genetic Elements Mediating Multiple-Drug Resistance, in Avian
Escherichia coli
Authors: Bass Lydia , Liebert Cynthia A. , Lee Margie D. , Summers Anne O. , White David G. , Thayer Stephan G. , Maurer John J.
Published: October 2018

Antibiotic resistance among avian bacterial isolates is common and is of great concern to the poultry industry. Approximately 36% (
n
= 100) of avian, pathogenic
Escherichia coli
isolates obtained from diseased poultry exhibited multiple-antibiotic resistance to tetracycline, oxytetracycline, streptomycin, sulfonamides, and gentamicin. Clinical avian
E. coli
isolates were further screened for the presence of markers for class 1 integrons, the integron recombinase
intI1
and the quaternary ammonium resistance gene
qacEΔ1
, in order to determine the contribution of integrons to the observed multiple-antibiotic resistance phenotypes. Sixty-three percent of the clinical isolates were positive for the class 1 integron markers
intI1
and
qacEΔ1
. PCR analysis with the conserved class 1 integron primers yielded amplicons of approximately 1 kb from
E. coli
isolates positive for
intI1
and
qacEΔ1
. These PCR amplicons contained the spectinomycin-streptomycin resistance gene
aadA1
. Further characterization of the identified integrons revealed that many were part of the transposon Tn
21
, a genetic element that encodes both antibiotic resistance and heavy-metal resistance to mercuric compounds. Fifty percent of the clinical isolates positive for the integron marker gene
intI1
as well as for the
qacEΔ1
and
aadA1
cassettes also contained the mercury reductase gene
merA
. The correlation between the presence of the
merA
gene with that of the integrase and antibiotic resistance genes suggests that these integrons are located in Tn
21
. The presence of these elements among avian
E. coli
isolates of diverse genetic makeup as well as in
Salmonella
suggests the mobility of Tn
21
among pathogens in humans as well as poultry.
A New Method for Assessing Metronidazole Susceptibility of
Giardia lamblia
Trophozoites
Authors: Sousa M. Céu , Poiares-da-Silva J.
Published: October 2018

A quantitative, simple, and rapid assay has been developed to assess
Giardia lamblia
trophozoite sensitivity to metronidazole [1-(2-hydroxyetyl)-2-methyl-5-nitroimidazole] (MTZ). This new assay utilizes the ability of live (surviving) trophozoites to take up oxygen after have been exposed to MTZ. The effect of MTZ on oxygen uptake was compared with its effect on viability as evaluated by a culture method and morphological assays. Oxygen uptake rates decreased in trophozoites treated with MTZ, and this effect was drug concentration dependent: O
2
uptake rates went from 3.04 μM O
2
min
−1
per 10
6
cells to 0.72 μM O
2
min
−1
per 10
6
cells with increasing drug concentration (0.15 to 0.6 mM) in the preincubation. Concentrations of the drug which inhibited oxygen uptake by 28 to 76% in trophozoites killed from 39 to 82% of trophozoites, as evaluated by the culture method, and altered the morphology of 21 to 86% of the trophozoites. Thus, the trophozoites killed by MTZ are nonmotile cells and do not take up oxygen. A good correlation was found between the inhibitory effects of MTZ, as evaluated by oxygen uptake, and cellular viability. Similar 50% inhibitory concentrations were obtained: 0.33 mM by oxygen uptake, 0.26 mM by the culture method, and 0.35 mM by morphological criteria. Oxygen uptake appears to be a good indicator of parasite viability. Therefore, this new method can provide a convenient means to assess MTZ susceptibility in
G. lamblia
and can be applied for screening potential antigiardial agents.
In Vitro Activities of SCH27899 Alone and in Combination with 17 Other Antimicrobial Agents
Authors: Fuchs Peter C. , Barry Arthur L. , Brown Steven D.
Published: October 2018

SCH27899, an everninomicin antibiotic, was tested for its in vitro activity against 718 bacterial isolates representing 27 species. The
Enterobacteriaceae
and nonenteric gram-negative bacilli were resistant to ≥8.0 μg/ml, but all others were inhibited by ≤1.0 μg/ml. When tested in combination with 17 other antimicrobial agents against 110 strains, SCH27899 demonstrated no significant antagonism or synergy. Consequently, combination therapy is not contraindicated.
Exposure to Antibiotics Induces Expression of the
Mycobacterium tuberculosis sigF
Gene: Implications for Chemotherapy against Mycobacterial Persistors
Authors: Michele Theresa M. , Ko Chiew , Bishai William R.
Published: October 2018

The
sigF
gene encodes an alternate sigma factor found in
Mycobacterium tuberculosis
and related pathogenic mycobacteria. Determination of conditions of
sigF
expression is an important step in understanding the conditional gene regulation which may govern such processes as virulence and dormancy in mycobacteria. We constructed an in-frame translational
lacZ-kan
fusion within the
sigF
gene to determine the conditions of
sigF
expression. This reporter construct was expressed from a multicopy plasmid in a strain of BCG harboring an integrated luciferase reporter gene under the control of the mycobacteriophage L5 gp71 promoter. Antibiotic exposure, in particular, ethambutol, rifampin, streptomycin, and cycloserine treatment, increased the level of SigF reporter specific expression in a dose-dependent fashion. The level of SigF reporter specific expression increased over 100-fold in late-stationary-phase growth compared to that in exponential growth. During the exponential phase, SigF specific expression could be induced by a number of other stresses. Anaerobic metabolism induced SigF by greater than 150-fold, particularly in the presence of metronidazole. Cold shock increased the level of SigF specific expression, while heat shock decreased it. Oxidative stress was also an important inducer of SigF specific expression; a greater induction was seen with cumene hydroperoxide than with hydrogen peroxide. Comparisons of bacterial viability as determined by the luciferase assay or by plating serial dilutions revealed that luciferase gp71-dependent activity was an unreliable predictor of the numbers of CFU during stationary-phase growth and anaerobic metabolism. The induction of
sigF
following antibiotic exposure suggests that this bacterial transcription factor may control genes which are important for mycobacterial persistence in the host during chemotherapy.
Expression in
Escherichia coli
of a New Multidrug Efflux Pump, MexXY, from
Pseudomonas aeruginosa
Authors: Mine Tomoyuki , Morita Yuji , Kataoka Atsuko , Mizushima Tohru , Tsuchiya Tomofusa
Published: October 2018

Two new genes (
mexXY
) similar to
mexAB
,
mexCD
, and
mexEF
and mediating multidrug resistance were cloned from the chromosome of
Pseudomonas aeruginosa
. Elevated ethidium extrusion was observed with
Escherichia coli
cells harboring the plasmid carrying
mexXY
. This MexXY system confers higher resistance to fluoroquinolones than the MexAB and MexCD systems, and
E. coli
TolC or
P. aeruginosa
OprM is necessary for the function of the MexXY system.
Comparative Activities of Clinafloxacin, Grepafloxacin, Levofloxacin, Moxifloxacin, Ofloxacin, Sparfloxacin, and Trovafloxacin and Nonquinolones Linozelid, Quinupristin-Dalfopristin, Gentamicin, and Vancomycin against Clinical Isolates of Ciprofloxacin-Resistant and -Susceptible
Staphylococcus aureus
Strains
Authors: Jones Mark E. , Visser Maarten R. , Klootwijk Miriam , Heisig Peter , Verhoef Jan , Schmitz Franz-Josef
Published: October 2018

The activities of eight fluoroquinolones and linezolid, quinupristin-dalfopristin (Synercid), gentamicin, and vancomycin were tested against 96 ciprofloxacin-susceptible and 205 ciprofloxacin-resistant
Staphylococcus aureus
strains. Overall, clinafloxacin, followed by moxifloxacin and trovafloxacin, was the most active quinolone tested. For all isolates, linezolid and quinupristin-dalfopristin showed activities that were at least comparable to vancomycin, with no cross-resistance to any other test compound.
Metabolic Characterization of a Tripeptide Human Immunodeficiency Virus Type 1 Protease Inhibitor, KNI-272, in Rat Liver Microsomes
Authors: Kiriyama Akiko , Nishiura Tomoyuki , Yamaji Hirokazu , Takada Kanji
Published: October 2018

KNI-272 is a tripeptide protease inhibitor for treating human immunodeficiency virus type 1 (HIV-1). In in vitro stability studies using rat tissue homogenates, KNI-272 concentrations in the liver, kidney, and brain decreased significantly with time. Moreover, in tissue distribution studies, KNI-272 distributed highly to the liver, kidney, and small intestine in vivo. From these results and reported physiological parameters such as the tissue volume and tissue blood flow rate, we considered the liver to be the main organ which takes part in the metabolic elimination of KNI-272. Then the hepatic metabolism of KNI-272 was more thoroughly investigated by using rat liver microsomes. KNI-272 was metabolized in the rat liver microsomes, and five metabolites were found. The initial metabolic rate constant (
k
metabolism
) tended to decrease when the KNI-272 concentration in microsomal suspensions increased. The calculated Michaelis-Menten constant

(K
m
)

and the maximum velocity of KNI-272 metabolism (
V
max
), after correction for the unbound drug concentration, were 1.12 ± 0.09 μg/ml (1.68 ± 0.13 μM) and 0.372 ± 0.008 μg/mg of protein/min (0.558 ± 0.012 nmol/mg of protein per min), respectively. The metabolic clearance (CL
int,metabo
), calculated as
V
max
/

K
m

, was 0.332 ml/mg of protein per min. Moreover, by using selective cytochrome P-450 inhibitors and recombinant human CYP3A4 fractions, KNI-272 was determined to be metabolized mainly by the CYP3A isoform. In addition, ketoconazole, a representative CYP3A inhibitor, inhibited KNI-272 metabolism competitively, and the inhibition constant

(K
i
)

was 4.32 μM.
Efficacy of Ampicillin plus Ceftriaxone in Treatment of Experimental Endocarditis Due to
Enterococcus faecalis
Strains Highly Resistant to Aminoglycosides
Authors: Gavaldà Joan , Torres Carmen , Tenorio Carmen , López Pedro , Zaragoza Myriam , Capdevila Josep A. , Almirante Benito , Ruiz Fernanda , Borrell Nuria , Gomis Xavier , Pigrau Carles , Baquero Fernando , Pahissa Albert
Published: October 2018

The purpose of this work was to evaluate the in vitro possibilities of ampicillin-ceftriaxone combinations for 10
Enterococcus faecalis
strains with high-level resistance to aminoglycosides (HLRAg) and to assess the efficacy of ampicillin plus ceftriaxone, both administered with humanlike pharmacokinetics, for the treatment of experimental endocarditis due to HLRAg
E. faecalis
. A reduction of 1 to 4 dilutions in MICs of ampicillin was obtained when ampicillin was combined with a fixed subinhibitory ceftriaxone concentration of 4 μg/ml. This potentiating effect was also observed by the double disk method with all 10 strains. Time-kill studies performed with 1 and 2 μg of ampicillin alone per ml or in combination with 5, 10, 20, 40, and 60 μg of ceftriaxone per ml showed a ≥2 log
10
reduction in CFU per milliliter with respect to ampicillin alone and to the initial inoculum for all 10
E. faecalis
strains studied. This effect was obtained for seven strains with the combination of 2 μg of ampicillin per ml plus 10 μg of ceftriaxone per ml and for six strains with 5 μg of ceftriaxone per ml. Animals with catheter-induced endocarditis were infected intravenously with 10
8
CFU of
E. faecalis
V48 or 10
5
CFU of
E. faecalis
V45 and were treated for 3 days with humanlike pharmacokinetics of 2 g of ampicillin every 4 h, alone or combined with 2 g of ceftriaxone every 12 h. The levels in serum and the pharmacokinetic parameters of the humanlike pharmacokinetics of ampicillin or ceftriaxone in rabbits were similar to those found in humans treated with 2 g of ampicillin or ceftriaxone intravenously. Results of the therapy for experimental endocarditis caused by
E. faecalis
V48 or V45 showed that the residual bacterial titers in aortic valve vegetations were significantly lower in the animals treated with the combinations of ampicillin plus ceftriaxone than in those treated with ampicillin alone (
P
< 0.001). The combination of ampicillin and ceftriaxone showed in vitro and in vivo synergism against HLRAg
E. faecalis
.
Fluoroquinolone Action against Clinical Isolates of
Mycobacterium tuberculosis
: Effects of a C-8 Methoxyl Group on Survival in Liquid Media and in Human Macrophages
Authors: Zhao Ben Yang , Pine Richard , Domagala John , Drlica Karl
Published: October 2018

When the lethal action of a C-8 methoxyl fluoroquinolone against clinical isolates of
Mycobacterium tuberculosis
in liquid medium was measured, the compound was found to be three to four times more effective (as determined by measuring the 90% lethal dose) than a C-8-H control fluoroquinolone or ciprofloxacin against cells having a wild-type
gyrA
(gyrase) gene. Against ciprofloxacin-resistant strains, the C-8 methoxyl group enhanced lethality when alanine was replaced by valine at position 90 of the GyrA protein or when aspartic acid 94 was replaced by glycine, histidine, or tyrosine. During infection of a human macrophage model by wild-type
Mycobacterium bovis
BCG, the C-8 methoxyl group lowered survival 20- to 100-fold compared with the same concentration of a C-8-H fluoroquinolone. The C-8 methoxyl fluoroquinolone was also more effective than ciprofloxacin against a
gyrA
Asn94 mutant of
M. bovis
BCG. In an
M. tuberculosis
-macrophage system the C-8 methoxyl group improved fluoroquinolone action against both quinolone-susceptible and quinolone-resistant clinical isolates. Thus, a C-8 methoxyl group enhances the bactericidal activity of quinolones with N1-cyclopropyl substitutions; these data encourage further refinement of fluoroquinolones as antituberculosis agents.
Comparison of Efficacies of Oral Levofloxacin and Oral Ciprofloxacin in a Rabbit Model of a Staphylococcal Abscess
Authors: Fernandez Jeffrey , Barrett John F. , Licata Lisa , Amaratunga Dhammika , Frosco Marybeth
Published: October 2018

Oral levofloxacin was compared to oral ciprofloxacin in a
Staphylococcus aureus
subcutaneous abscess model in rabbits. Rabbits were surgically prepared with subcutaneous wiffle balls (43 mm in diameter) and allowed to recover for 4 to 6 weeks. Rabbits were infected by direct injection into the capsule with
S. aureus
ATCC 29213 (5 × 10
5
CFU) and were allowed to remain infected for 8 days before the initiation of anti-infective treatment. Efficacy was determined by assessing the bacterial load within the capsule over a 10-day treatment period. In single-dose pharmacokinetic studies in infected rabbits, similar area under the concentration-time curve/MIC ratios were obtained in the plasma and abscess fluid for levofloxacin at 45 mg/kg of body weight and ciprofloxacin at 200 mg/kg of body weight. Similar efficacies were seen with levofloxacin at 45 mg/kg/day and ciprofloxacin 400 mg/kg/day by day 10. In this model, levofloxacin was significantly more efficacious than ciprofloxacin (
P
< 0.01).
In Vitro and In Vivo Antibacterial Activities of a Novel Glycylcycline, the 9-
t
-Butylglycylamido Derivative of Minocycline (GAR-936)
Authors: Petersen P. J. , Jacobus N. V. , Weiss W. J. , Sum P. E. , Testa R. T.
Published: October 2018

The 9-
t
-butylglycylamido derivative of minocycline (TBG-MINO) is a recently synthesized member of a novel group of antibiotics, the glycylcyclines. This new derivative, like the first glycylcyclines, the
N
,
N
-dimethylglycylamido derivative of minocycline and 6-demethyl-6-deoxytetracycline, possesses activity against bacterial isolates containing the two major determinants responsible for tetracycline resistance: ribosomal protection and active efflux. The in vitro activities of TBG-MINO and the comparative agents were evaluated against strains with characterized tetracycline resistance as well as a spectrum of recent clinical aerobic and anaerobic gram-positive and gram-negative bacteria. TBG-MINO, with an MIC range of 0.25 to 0.5 μg/ml, showed good activity against strains expressing
tet
(M) (ribosomal protection),
tet
(A),
tet
(B),
tet
(C),
tet
(D), and
tet
(K) (efflux resistance determinants). TBG-MINO exhibited similar activity against methicillin-resistant
Staphylococcus aureus
(MRSA), penicillin-resistant streptococci, and vancomycin-resistant enterococci (MICs at which 90% of strains are inhibited, ≤0.5 μg/ml). TBG-MINO exhibited activity against a wide diversity of gram-negative aerobic and anaerobic bacteria, most of which were less susceptible to tetracycline and minocycline. The in vivo protective effects of TBG-MINO were examined against acute lethal infections in mice caused by
Escherichia coli
,
S. aureus
, and
Streptococcus pneumoniae
isolates. TBG-MINO, administered intravenously, demonstrated efficacy against infections caused by
S. aureus
including MRSA strains and strains containing
tet
(K) or
tet
(M) resistance determinants (median effective doses [ED
50
s], 0.79 to 2.3 mg/kg of body weight). TBG-MINO demonstrated efficacy against infections caused by tetracycline-sensitive
E. coli
strains as well as
E. coli
strains containing either
tet
(M) or the efflux determinant
tet
(A),
tet
(B), or
tet
(C) (ED
50
s, 1.5 to 3.5 mg/kg). Overall, TBG-MINO shows antibacterial activity against a wide spectrum of gram-positive and gram-negative aerobic and anaerobic bacteria including strains resistant to other chemotherapeutic agents. The in vivo protective effects, especially against infections caused by resistant bacteria, corresponded with the in vitro activity of TBG-MINO.
Bile Salts: Natural Detergents for the Prevention of Sexually Transmitted Diseases
Authors: Herold Betsy C. , Kirkpatrick Risa , Marcellino Daniel , Travelstead Anna , Pilipenko Valentina , Krasa Holly , Bremer James , Dong Li Jin , Cooper Morris D.
Published: October 2018

The development of new, safe, topical microbicides for intravaginal use for the prevention of sexually transmitted diseases is imperative. Previous studies have suggested that bile salts may inhibit human immunodeficiency virus infection; however, their activities against other sexually transmitted pathogens have not been reported. To further explore the potential role of bile salts in preventing sexually transmitted diseases, we examined the in vitro activities and cytotoxicities of select bile salts againstChlamydia trachomatis, herpes simplex virus (types 1 and 2),Neisseria gonorrhoeae, and human immunodeficiency virus in comparison to those of nonoxynol-9 and benzalkonium chloride using both primary cells and cell lines derived from the human female genital tract. We found that taurolithocholic acid 3-sulfate and a combination of glycocholic acid and taurolithocholic acid 3-sulfate showed excellent activity against all of the pathogens assayed. Moreover, taurolithocholic acid 3-sulfate alone or in combination was less cytotoxic than nonoxynol-9 and benzalkonium chloride. Thus, taurolithocholic acid 3-sulfate alone or in combination warrants further evaluation as a candidate topical microbicidal agent.
Efficacy of Doxycycline, Azithromycin, or Trovafloxacin for Treatment of Experimental Rocky Mountain Spotted Fever in Dogs
Authors: Breitschwerdt E. B. , Papich M. G. , Hegarty B. C. , Gilger B. , Hancock S. I. , Davidson M. G.
Published: October 2018

Dogs were experimentally inoculated withRickettsia rickettsii(canine origin) in order to compare the efficacies of azithromycin and trovafloxacin to that of the current antibiotic standard, doxycycline, for the treatment of Rocky Mountain spotted fever. Clinicopathologic parameters, isolation of rickettsiae in tissue culture, and PCR amplification of rickettsial DNA were used to evaluate the response to therapy or duration of illness (untreated infection control group) in the four groups. Concentrations of the three antibiotics in plasma and blood cells were measured by high-performance liquid chromatography. Doxycycline and trovafloxacin treatments resulted in more-rapid defervescence, whereas all three antibiotics caused rapid improvement in attitudinal scores, blood platelet numbers, and the albumin/total-protein ratio. Based upon detection of retinal vascular lesions by fluorescein angiography, trovafloxacin and doxycycline substantially decreased rickettsia-induced vascular injury to the eye, whereas the number of ocular lesions in the azithromycin group did not differ from that in the infection control group. As assessed by tissue culture isolation, doxycycline resulted in the earliest apparent clearance of viable circulating rickettsiae; however, rickettsial DNA could still be detected in the blood of some dogs from all four groups on day 21 postinfection, despite our inability to isolate viable rickettsiae at that point. As administered in this study, trovafloxacin was as efficacious as doxycycline but azithromycin proved less efficacious, possibly due to the short duration of administration.
LY303366 Exhibits Rapid and Potent Fungicidal Activity in Flow Cytometric Assays of Yeast Viability
Authors: Green Lisa J. , Marder Philip , Mann Larry L. , Chio Li-Chun , Current William L.
Published: October 2018

LY303366 is a semisynthetic analog of the antifungal lipopeptide echinocandin B that inhibits (1,3)-β-
d
-glucan synthase and exhibits efficacy in animal models of human fungal infections. In this study, we utilized flow cytometric analysis of propidium iodide uptake, single-cell sorting, and standard microbiological plating methods to study the antifungal effect of LY303366 on
Saccharomyces cerevisiae
and
Candida albicans
. Our data indicate that an initial 5-min pulse treatment with LY303366 caused yeasts to take up propidium iodide and lose their ability to grow. Amphotericin B and cilofungin required longer exposure periods (30 and 180 min, respectively) and higher concentrations to elicit these fungicidal effects. These two measurements of fungicidal activity by LY303366 were highly correlated (
r
> 0.99) in concentration response and time course experiments. As further validation, LY303366-treated yeasts that stained with propidium iodide were unable to grow in single-cell-sorted cultures. Our data indicate that LY303366 is potent and rapidly fungicidal for actively growing yeasts. The potency and rapid action of this new fungicidal compound suggest that LY303366 may be useful for antifungal therapy.
Clavulanate Induces Expression of the
Pseudomonas aeruginosa
AmpC Cephalosporinase at Physiologically Relevant Concentrations and Antagonizes the Antibacterial Activity of Ticarcillin
Authors: Lister Philip D. , Gardner Victoria M. , Sanders Christine C.
Published: October 2018

Although previous studies have indicated that clavulanate may induce AmpC expression in isolates of
Pseudomonas aeruginosa
, the impact of this inducer activity on the antibacterial activity of ticarcillin at clinically relevant concentrations has not been investigated. Therefore, a study was designed to determine if the inducer activity of clavulanate was associated with in vitro antagonism of ticarcillin at pharmacokinetically relevant concentrations. By the disk approximation methodology, clavulanate induction of AmpC expression was observed with 8 of 10 clinical isolates of
P. aeruginosa
. Quantitative studies demonstrated a significant induction of AmpC when clavulanate-inducible strains were exposed to the peak concentrations of clavulanate achieved in human serum with the 3.2- and 3.1-g doses of ticarcillin-clavulanate. In studies with three clavulanate-inducible strains in an in vitro pharmacodynamic model, antagonism of the bactericidal effect of ticarcillin was observed in some tests with regimens simulating a 3.1-g dose of ticarcillin-clavulanate and in all tests with regimens simulating a 3.2-g dose of ticarcillin-clavulanate. No antagonism was observed in studies with two clavulanate-noninducible strains. In contrast to clavulanate, tazobactam failed to induce AmpC expression in any strains, and the pharmacodynamics of piperacillin-tazobactam were somewhat enhanced over those of piperacillin alone against all strains studied. Overall, the data collected from the pharmacodynamic model suggested that induction per se was not always associated with reduced killing but that a certain minimal level of induction by clavulanate was required before antagonism of the antibacterial activity of its companion drug occurred. Nevertheless, since clinically relevant concentrations of clavulanate can antagonize the bactericidal activity of ticarcillin, the combination of ticarcillin-clavulanate should be avoided when selecting an antipseudomonal β-lactam for the treatment of
P. aeruginosa
infections, particularly in immunocompromised patients. For piperacillin-tazobactam, induction is not an issue in the context of treating this pathogen.
Fourteen-Member Macrolides Inhibit Interleukin-8 Release by Human Eosinophils from Atopic Donors
Authors: Kohyama Tadashi , Takizawa Hajime , Kawasaki Shin , Akiyama Norihisa , Sato Makoto , Ito Koji
Published: October 2018

Macrolide antibiotics such as erythromycin have been reported to be effective for asthma. However, the precise mechanisms of this effect remain unclear. We studied the effect of erythromycin, clarithromycin, josamycin, and other antibiotics on the release by eosinophils of interleukin-8 (IL-8), a potent chemokine for inflammatory cells, including eosinophils themselves. Human eosinophils were isolated from atopic patients, and the effects of the drugs on IL-8 release were evaluated. Only 14-member macrolides (erythromycin and clarithromycin) showed a concentration-dependent suppressive effect on IL-8 release (control, 100%; erythromycin at 1 μg/ml, 67.82% ± 3.45% [P< 0.01]; clarithromycin at 5 μg/ml, 56.81% ± 9.61% [P< 0.01]). The effect was found at therapeutic concentrations and appeared to occur at the posttranscriprtional level. In contrast, a 16-member macrolide (josamycin) had no significant effect. We suggest that 14-member macrolides inhibit IL-8 release by eosinophils and may thereby prevent the autocrine cycle necessary for the recruitment of these cells into the airways.
Integron-Mediated Rifampin Resistance in
Pseudomonas aeruginosa
Authors: Tribuddharat Chanwit , Fennewald Michael
Published: October 2018

A new rifampin resistance gene,
arr-2
, has been found in
Pseudomonas aeruginosa
. The ARR-2 protein shows 54% amino acid identity to the rifampin ADP-ribosylating transferase encoded by the
arr
gene from
Mycobacterium smegmatis
. This
arr-2
gene is located on a gene cassette within a class I integron.
Pharmacokinetics of Oral Zidovudine Entrapped in Biodegradable Nanospheres in Rabbits
Authors: Callender Diana P. , Jayaprakash Nalini , Bell Aaron , Petraitis Vidmantas , Petratienes Ruta , Candelario Myrna , Schaufele Robert , Dunn James M. , Sei Shizuko , Walsh Thomas J. , Balis Frank M.
Published: October 2018

The pharmacokinetic profile of oral zidovudine entrapped in a 50:50 polyactide-coglycolide matrix (nanospheres) was compared to those of standard oral and parenteral zidovudine formulations in rabbits. The bioavailability of zidovudine nanospheres at 50 mg/kg of body weight was 76%, and this dose achieved prolonged exposure to zidovudine compared to standard formulations without an increase in the drug’s peak concentration.
Assessment of the Effect of Amphotericin B on the Vitality of
Candida albicans
Authors: Liao Robert S. , Rennie Robert P. , Talbot James A.
Published: October 2018

The processes involved in cell death are complex, and individual techniques measure specific fractions of the total population. The interaction of
Candida albicans
with amphotericin B was measured with fluorescent probes with different cellular affinities. These were used to provide qualitative and quantitative information of physiological parameters which contribute to fungal cell viability. SYBR Green I and 5,(6)-carboxyfluorescein were used to assess membrane integrity, and bis-(1,3-dibutylbarbituric acid)trimethine oxonol and 3,3-dihexyloxacarbocyanine iodide were used to evaluate alterations in membrane potential. The fluorescent indicators were compared with replication competency, the conventional indicator of viability. By using these tools, the evaluation of the response of
C. albicans
to amphotericin B time-kill curves delineated four categories which may represent a continuum between alive and dead. The data showed that replication competency (CFU per milliliter) as determined by conventional antifungal susceptibility techniques provided only an estimate of inhibition. Interpretation of fluorescent staining characteristics indicated that
C. albicans
cells which were replication incompetent after exposure to greater than 0.5 μg of amphotericin B per ml still maintained degrees of physiological function.
Negative Regulation of the
Pseudomonas aeruginosa
Outer Membrane Porin OprD Selective for Imipenem and Basic Amino Acids
Authors: Ochs Martina M. , McCusker Matthew P. , Bains Manjeet , Hancock Robert E. W.
Published: October 2018

Pseudomonas aeruginosa
OprD is a specific porin which facilitates the uptake of basic amino acids and imipenem, a carbapenem antibiotic. Resistance to imipenem due to the loss of OprD is an important mechanism for the loss of clinical effectiveness. To investigate the negative regulatory mechanisms influencing
oprD
expression, a gene upstream of the coregulated
mexEF-oprN
efflux operon, designated
mexT
, was cloned. The predicted 304-amino-acid mature MexT protein showed strong homology to LysR-type regulators. When overexpressed it induced the expression of the
mexEF-oprN
efflux operon while decreasing the level of expression of OprD. The use of an
oprD
::
xylE
transcriptional fusion indicated that it acted by repressing the transcription of
oprD
. Salicylate, a weak aromatic acid known to reduce porin expression and induce low levels of multiple antibiotic resistance in
Escherichia coli
, was able to induce imipenem resistance and reduce the expression of OprD but not multiple antibiotic resistance or OprN expression in
P. aeruginosa
. This was also demonstrated to occur at the level of transcription. Acetyl salicylate and benzoate, but not catechol, were also able to reduce the levels of OprD in the
P. aeruginosa
outer membranes. These OprD-suppressing compounds increased imipenem resistance even in a
mexT
-overexpressing and
nfxC
mutant backgrounds, suggesting that such resistance is independent of the MexT repressor and that
oprD
is influenced by more than a single mechanism of repression.
Streptococcus pneumoniae
DNA Gyrase and Topoisomerase IV: Overexpression, Purification, and Differential Inhibition by Fluoroquinolones
Authors: Pan Xiao-Su , Fisher L. Mark
Published: October 2018

Streptococcus pneumoniae gyrA
and
gyrB
genes specifying the DNA gyrase subunits have been cloned into pET plasmid vectors under the control of an inducible T7 promoter and have been separately expressed in
Escherichia coli
. Soluble 97-kDa GyrA and 72-kDa GyrB proteins bearing polyhistidine tags at their respective C-terminal and N-terminal ends were purified to apparent homogeneity by one-step nickel chelate column chromatography and were free of host
E. coli
topoisomerase activity. Equimolar amounts of the gyrase subunits reconstituted ATP-dependent DNA supercoiling with comparable activity to gyrase of
E. coli
and
Staphylococcus aureus
. In parallel,
S. pneumoniae
topoisomerase IV ParC and ParE subunits were similarly expressed in
E. coli
, purified to near homogeneity as 93- and 73-kDa proteins, and shown to generate efficient ATP-dependent DNA relaxation and DNA decatenation activities. Using the purified enzymes, we examined the inhibitory effects of three paradigm fluoroquinolones—ciprofloxacin, sparfloxacin, and clinafloxacin—which previous genetic studies with
S. pneumoniae
suggested act preferentially through topoisomerase IV, through gyrase, and through both enzymes, respectively. Surprisingly, all three quinolones were more active in inhibiting purified topoisomerase IV than gyrase, with clinafloxacin showing the greatest inhibitory potency. Moreover, the tested agents were at least 25-fold more effective in stabilizing a cleavable complex (the relevant cytotoxic lesion) with topoisomerase IV than with gyrase, with clinafloxacin some 10- to 32-fold more potent against either enzyme, in line with its superior activity against
S. pneumoniae
. The uniform target preference of the three fluoroquinolones for topoisomerase IV in vitro is in apparent contrast to the genetic data. We interpret these results in terms of a model for bacterial killing by quinolones in which cellular factors can modulate the effects of target affinity to determine the cytotoxic pathway.
Intravenous Penciclovir for Treatment of Herpes Simplex Infections in Immunocompromised Patients: Results of a Multicenter, Acyclovir-Controlled Trial
Authors: Lazarus Hillard M. , Belanger Robert , Candoni Anna , Aoun Mickaël , Jurewicz Regina , Marks Lynn ,   The Penciclovir Immunocompromised Study Group
Published: October 2018

The efficacy and safety of penciclovir (PCV) for the treatment of herpes simplex virus (HSV) infections in immunocompromised (IC) patients were studied in a double-blind, acyclovir (ACV)-controlled, multicenter study. A total of 342 patients with mucocutaneous HSV infections received 5 mg of PCV per kg every 12 or 8 h (q12h or q8h) or 5 mg of ACV per kg q8h, beginning within 72 h of lesion onset and continuing for up to 7 days. The mean age of the patients was 49 years; 94% were white and 52% were female. The main reasons for their IC states were hematologic disorder (63%) and transplant plus hematologic disorder (16%). Clinical and virological assessments were performed daily during the 7-day treatment and then every other day until lesion healing. The primary efficacy parameter addressed new lesion formation. Secondary end points focused on viral shedding, healing, and pain. Approximately 20% of patients in each treatment group developed new lesions during therapy; thus, equivalence with ACV (defined prospectively) was demonstrated for both q12h and q8h PCV regimens. For all three treatment groups, the median time to the cessation of viral shedding was 4 days and the median time to complete healing was 8 days; there were no statistically significant differences in the rates of complete healing or the cessation of viral shedding when the results for PCV q12h and q8h were compared with those for ACV q8h. In addition, there was no statistically significant difference between PCV q12h or q8h, compared with ACV q8h, for the resolution of pain. PCV was well tolerated, with an adverse event profile comparable to that of ACV. In conclusion, PCV q12h is a well-tolerated and effective therapy for mucocutaneous HSV infection in IC patients and offers a reduced frequency of dosing compared with ACV q8h.
Ultrasonic Enhancement of Antibiotic Action on
Escherichia coli
Biofilms: an In Vivo Model
Authors: Rediske Andrea M. , Roeder Beverly L. , Brown Maren K. , Nelson Jared L. , Robison Rachel L. , Draper David O. , Schaalje G. Bruce , Robison Richard A. , Pitt William G.
Published: October 2018

Biofilm infections are a common complication of prosthetic devices in humans. Previous in vitro research has determined that low-frequency ultrasound combined with aminoglycoside antibiotics is an effective method of killing biofilms. We report the development of an in vivo model to determine if ultrasound enhances antibiotic action. Two 24-h-old
Escherichia coli
(ATCC 10798) biofilms grown on polyethylene disks were implanted subcutaneously on the backs of New Zealand White female rabbits, one on each side of the spine. Low-frequency (28.48-kHz) and low-power-density (100- and 300-mW/cm
2
) continuous ultrasound treatment was applied for 24 h with and without systemic administration of gentamicin. The disks were then removed, and the number of viable bacteria on each disk was determined. At the low ultrasonic power used in this study, exposure to ultrasound only (no gentamicin) caused no significant difference in bacterial viability. In the presence of antibiotic, there was a significant reduction due to 300-mW/cm
2
ultrasound (
P
= 0.0485) but no significant reduction due to 100-mW/cm
2
ultrasound. Tissue damage to the skin was noted at the 300-mW/cm
2
treatment level. Further development of this technique has promise in treatment of clinical implant infections.
N-Acylated and
d
Enantiomer Derivatives of a Nonamer Core Peptide of Lactoferricin B Showing Improved Antimicrobial Activity
Authors: Wakabayashi Hiroyuki , Matsumoto Hiroshi , Hashimoto Koichi , Teraguchi Susumu , Takase Mitsunori , Hayasawa Hirotoshi
Published: October 2018

N-acylated or
d
enantiomer peptide derivatives based on the sequence RRWQWRMKK in lactoferricin B demonstrated antimicrobial activities greater than those of lactoferricin B against bacteria and fungi. The most potent peptide, conjugated with an 11-carbon-chain acyl group, showed two to eight times lower MIC than lactoferricin B.
Metronidazole Therapy in Mice Infected with Tuberculosis
Authors: Brooks Jason V. , Furney Synthia K. , Orme Ian M.
Published: October 2018

The capacity of metronidazole to inhibit the growth ofMycobacterium tuberculosiswas tested in in vitro and in vivo mouse models. In vitro addition of metronidazole to cultures of infected bone marrow-derived macrophages had no effect, nor did it increase the reduction in bacterial load due to isoniazid. In vivo, metronidazole did not reduce bacterial numbers in the lungs of aerosol-infected mice during the active stage of the disease, during a phase of containment, or after prolonged isoniazid therapy (Cornell model). A small but significant reduction was seen if metronidazole therapy was given during an established chronic disease state 100 days after aerosol administration. These data indicate that under most conditionsM. tuberculosisorganisms are not in a metabolic state in which they are susceptible to the action of metronidazole and, hence, that this drug would be of limited clinical value.
Resistance to β-Lactam Antibiotics in
Pseudomonas aeruginosa
Due to Interplay between the MexAB-OprM Efflux Pump and β-Lactamase
Authors: Nakae Taiji , Nakajima Akira , Ono Toshihisa , Saito Kohjiro , Yoneyama Hiroshi
Published: October 2018

We evaluated the roles of the MexAB-OprM efflux pump and β-lactamase in β-lactam resistance in
Pseudomonas aeruginosa
by constructing OprM-deficient, OprM basal level, and OprM fully expressed mutants from β-lactamase-negative, -inducible, and -overexpressed strains. We conclude that, with the notable exception of imipenem, the MexAB-OprM pump contributes significantly to β-lactam resistance in both β-lactamase-negative and β-lactamase-inducible strains, while the contribution of the MexAB-OprM efflux system is negligible in strains with overexpressed β-lactamase. Overexpression of the efflux pump alone contributes to the high level of β-lactam resistance in the absence of β-lactamase.
Synergistic In Vitro Antimalarial Activity of Omeprazole and Quinine
Authors: Skinner-Adams T. , Davis T. M. E.
Published: October 2018

Previous studies have shown that the proton pump inhibitor omeprazole has antimalarial activity in vitro. The interactions of omeprazole with commonly used antimalarial drugs were assessed in vitro. Omeprazole and quinine combinations were synergistic; however, chloroquine and omeprazole combinations were antagonistic. Artemisinin drugs had additive antimalarial activities with omeprazole.
Emergence of Fluoroquinolone Resistance among Multiply Resistant Strains of
Streptococcus pneumoniae
in Hong Kong
Authors: Ho Pak-Leung , Que Tak-Lun , Tsang Dominic Ngai-Chong , Ng Tak-Keung , Chow Kin-Hung , Seto Wing-Hon
Published: October 2018

The MICs of 17 antimicrobial agents for 181
Streptococcus pneumoniae
strains were determined by the E-test. Overall, 69.1% were penicillin resistant (MIC > 0.06 μg/ml). Resistance to ciprofloxacin (MIC > 2 μg/ml), levofloxacin (MIC > 2 μg/ml), or trovafloxacin (MIC > 1 μg/ml) was found in 12.1, 5.5, or 2.2% of the strains, respectively. These high rates of resistance raise concerns for the future.