bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacokinetics and Absolute Bioavailability of Ribavirin in Healthy Volunteers as Determined by Stable-Isotope Methodology
Authors: Preston Sandra L. , Drusano George L. , Glue Paul , Nash Jacqueline , Gupta S. K. , McNamara P.
Published: October 2018

Ribavirin has recently been demonstrated to have efficacy in combination with alpha interferon for treatment of relapsed hepatitis C. The marked improvement in the response rate after treatment with the combination regimen (10-fold higher versus that from monotherapy with alpha interferon) highlights the importance of determining the absolute bioavailability of ribavirin as a first step in beginning to investigate the pharmacodynamics of the combination. The objective of this study was to determine the absolute bioavailability of ribavirin with an intravenous formulation containing ribavirin labeled with the stable isotope
13
C
3
(
13
C
3
-ribavirin) and unlabeled oral ribavirin. Six healthy volunteers received 150 mg of intravenous
13
C
3
-ribavirin followed 1 h later by a 400-mg oral dose of ribavirin. Samples of blood and urine were collected up to 169 h postdosing. Concentrations of
13
C
3
-ribavirin and unlabeled ribavirin were determined by a high-performance liquid chromatography tandem mass spectrometric method. All plasma and urine data were comodeled for labeled and unlabeled ribavirin by using both the two- and three-compartment models in the program ADAPT II. A three-compartment model was chosen for the pharmacokinetic analysis with the Akaike Information Criterion. The mean maximum concentrations of drug in plasma for intravenous and oral ribavirin were 4,187 and 638 ng/ml, respectively. The mean bioavailability was 51.8% ± 21.8%, and the mean γ-phase half-life was 37.0 ± 14.2 h. The mean renal clearance, metabolic clearance, and volume of distribution of the central compartment were 6.94 liters/h, 18.1 liters/h, and 17.8 liters, respectively. The use of the stable-isotope methodology has provided the best estimate of the absolute bioavailability of ribavirin that is currently available, as there was neither a period bias nor a washout effect to confound the data. The study demonstrated that the mean bioavailability for a 400-mg dose of ribavirin was 52%, which is higher than that previously reported in other investigations.
Patterns of Macrolide Resistance Determinants among Community-Acquired
Streptococcus pneumoniae
Isolates over a 5-Year Period of Decreased Macrolide Susceptibility Rates
Authors: Oster Philipp , Zanchi Alessandra , Cresti Stefania , Lattanzi Maria , Montagnani Francesca , Cellesi Carla , Rossolini Gian Maria
Published: October 2018

Erythromycin resistance rates were found to be increased, from 7.1 in 1993 to 32.8% in 1997, among community-acquired
Streptococcus pneumoniae
isolates from the Siena area of central Italy. Most of the erythromycin-resistant isolates carried
ermAM
determinants and were also resistant to josamycin and clindamycin, whereas a minority (5.8%) carried
mefA
determinants and remained susceptible to the latter drugs.
In Vitro Susceptibilities of
Mycoplasma hominis
to Six Fluoroquinolones as Determined by E Test
Authors: Waites Ken B. , Canupp Kay C. , Kenny George E.
Published: October 2018

Twenty isolates of
Mycoplasma hominis
were tested for their susceptibility to six fluoroquinolones by the E test. The MICs at which 90% of the isolates were inhibited (in micrograms per milliliter) were as follows: sparfloxacin, 0.031; clinafloxacin, moxifloxacin, and trovafloxacin, 0.063; levofloxacin, 0.25; and ciprofloxacin, 0.5. Increasing the amount of inoculum or incubation in CO
2
elevated MICs by ≤1 dilution. E tests produce fluoroquinolone MICs comparable to those obtained by agar and microbroth dilution for
M. hominis.
Drug Tolerance in
Mycobacterium tuberculosis
Authors: Wallis Robert S. , Patil Shripad , Cheon Seon-Hee , Edmonds Kay , Phillips Manijeh , Perkins Mark D. , Joloba Moses , Namale Alice , Johnson John L. , Teixeira Lucileia , Dietze Reynaldo , Siddiqi Salman , Mugerwa Roy D. , Eisenach Kathleen , Ellner Jerrold J.
Published: October 2018

Although
Mycobacterium tuberculosis
is eradicated rapidly during therapy in some patients with pulmonary tuberculosis, it can persist for many months in others. This study examined the relationship between mycobacterial drug tolerance (delayed killing in vitro), persistence, and relapse. It was performed with 39 fully drug-susceptible isolates from a prospective trial of standard short-course antituberculous therapy with sputum smear-positive, human immunodeficiency virus-uninfected subjects with pulmonary tuberculosis in Brazil and Uganda. The rate of killing in vitro was determined by monitoring the growth index (GI) in BACTEC 12B medium after addition of drug to established cultures and was measured as the number of days required for 99% sterilization. Drugs differed significantly in bactericidal activity, in the following order from greatest to least, rifampin > isoniazid-ethambutol > ethambutol (
P
< 0.001). Isolates from subjects who had relapses (
n
= 2) or in whom persistence was prolonged (
n
= 1) were significantly more tolerant of isoniazid-ethambutol and rifampin than isolates from other subjects (
P
< 0.01). More generally, the duration of persistence during therapy was predicted by strain tolerance to isoniazid and rifampin (
P
= 0.012 and 0.026, respectively). Tolerance to isoniazid-ethambutol and tolerance to rifampin were highly correlated (
P
< 0.001). Tolerant isolates did not differ from others with respect to the MIC of isoniazid; the rate of killing of a tolerant isolate by isoniazid-ethambutol was not increased at higher drug concentrations. These observations suggest that tolerance may not be due to drug-specific mechanisms. Tolerance was of the phenotypic type, although increased tolerance appeared to emerge after prolonged drug exposure in vivo. This study suggests that drug tolerance may be an important determinant of the outcome of therapy for tuberculosis.
Isolation of Polymyxin B-Susceptible Mutants of
Burkholderia pseudomallei
and Molecular Characterization of Genetic Loci Involved in Polymyxin B Resistance
Authors: Burtnick Mary N. , Woods Donald E.
Published: October 2018

Burkholderia pseudomallei
is a gram-negative bacterium that causes the disease known as melioidosis. This pathogen is endemic to Southeast Asia and northern Australia and is particularly problematic in northeastern Thailand. It has been previously reported that
B. pseudomallei
is resistant to the killing action of cationic antimicrobial peptides, including human neutrophil peptide, protamine sulfate, poly-
l
-lysine, magainins, and polymyxins. Recently, we have also found that the virulent clinical isolate
B. pseudomallei
1026b is capable of replicating in media containing polymyxin B at concentrations of >100 mg/ml. In order to identify genetic loci that are associated with this particular resistance phenotype, we employed a Tn
5
-OT182 mutagenesis system in coordination with a replica plating screen to isolate polymyxin B-susceptible mutants. Of the 17,000 Tn
5
-OT182 mutants screened via this approach, five polymyxin B-susceptible mutants were obtained. Three of these mutants harbored Tn
5
-OT182 insertions within a genetic locus demonstrating strong homology to the
lytB
gene present in other gram-negative bacteria. Of the remaining two mutants, one contained a transposon insertion in a locus involved in lipopolysaccharide core biosynthesis (
waaF
), while the other contained an insertion in an open reading frame homologous to UDP-glucose dehydrogenase genes. Isogenic mutants were also constructed via allelic exchange and used in complementation analysis studies to further characterize the relative importance of each of the various genetic loci with respect to the polymyxin B resistance phenotype exhibited by
B. pseudomallei
1026b.
Oligonucleotides Tethered to a Short Polyguanylic Acid Stretch Are Targeted to Macrophages: Enhanced Antiviral Activity of a Vesicular Stomatitis Virus-Specific Antisense Oligonucleotide
Authors: Prasad Vikram , Hashim Shehla , Mukhopadhyay Amitabha , Basu Sandip K. , Roy Rajendra P.
Published: October 2018

The poor membrane permeability of oligonucleotides is one of the major problems of antisense technology. Here we report the construction of designer oligonucleotides for targeted delivery to macrophages. The oligonucleotides tethered to a 10-mer poly(G) sequence at their 3′ ends were recognized by scavenger receptors on macrophages and were taken up about 8- to 10-fold as efficiently as those oligonucleotides that either lacked a poly(G) tail or that contained a 10-mer poly(C) tail instead of the poly(G) tail. The enhanced uptake of poly(G) constructs was inhibited in the presence of poly(G) and other known ligands of the scavenger receptor. The bioefficacy of poly(G)-mediated targeting of antisense oligonucleotides (ANS) was demonstrated by using vesicular stomatitis virus (VSV) as a model system. The ability of ANS directed against the translation initiation site of N protein mRNA of VSV to inhibit virus replication was assessed. The ANS with the 10-mer poly(G) sequences (ANS-G) brought about significant inhibition of VSV replication in J774E cells (a murine monocyte/macrophage cell line) and Chinese hamster ovary (CHO) cell transfectants expressing scavenger receptors. The ANS lacking a 10-mer poly(G) stretch were ineffective. The inhibition of VSV replication due to ANS-G was completely abrogated in the presence of 10-mer poly(G), indicating that the antisense effect of the ANS-G molecule was a consequence of scavenger receptor-mediated enhanced uptake. Importantly, antisense molecules linked exclusively by natural phosphodiester bonds were as bioeffective as those synthesized with a mixed backbone of phosphodiester and phosphorothioate. Taken together, these results suggest that macrophage-directed designer ANS against infective agents may simply be obtained by adding a short stretch of guanylic acid sequence to the desired specific ANS during solid-phase synthesis. This nucleic acid-based strategy, which utilizes homogeneous preparation of ANS, may find applications in directed manipulation of macrophage metabolism for a variety of purposes as well as in therapy of a broad spectrum of macrophage-related disorders amenable to the antisense approach.
Activities of Gemifloxacin (SB 265805, LB20304) Compared to Those of Other Oral Antimicrobial Agents against Unusual Anaerobes
Authors: Goldstein Ellie J. C. , Citron Diane M. , Vreni Merriam C. , Tyrrell Kerin , Warren Yumi
Published: October 2018

The activities of gemifloxacin (SB 265805, LB20304) and comparator agents were determined by an agar dilution method against 419 clinical strains of less-commonly identified species of anaerobes. Gemifloxacin was generally more active than trovafloxacin against gram-positive strains by one to two dilutions. Peptostreptococci (
Peptostreptococcus asaccharolyticus
,
Peptostreptococcus magnus
,
Peptostreptococcus micros
, and
Peptostreptococcus prevotii
) and
Porphyromonas
spp. (
Porphyromonas asaccharolytica
,
Porphyromonas canoris
,
Porphyromonas gingivalis
, and
Porphyromonas macacae
) were all susceptible to ≤0.25 μg of gemifloxacin per ml. The MICs of gemifloxacin at which 90% of the following strains were inhibited (MIC
90
s) were ≤2 μg/ml:
Actinomyces israelii
,
Actinomyces odontolyticus
,
Clostridium innocuum
,
Clostridium clostridioforme
,
Anaerobiospirillum
spp.,
Bacteroides tectum
,
Bacteroides ureolyticus
,
Bacteroides gracilis
(now
Campylobacter gracilis
),
Prevotella intermedia
,
Prevotella heparinolytica
, and the
Prevotella oris-buccae
group.
Fusobacterium naviforme
and
Fusobacterium necrophorum
were also susceptible to ≤2 μg of gemifloxacin per ml, while
Fusobacterium varium
strains exhibited a bimodal pattern; the other
Fusobacterium
species, such as
Fusobacterium ulcerans
and
Fusobacterium russii
, as well as
Veillonella
spp., the
Prevotella melaninogenica
group,
Prevotella bivia
,
Clostridium difficile
, and
Bilophila wadsworthia
were relatively resistant to gemifloxacin (MIC
90
s, ≥4 μg/ml).
Emergence and Dissemination of Quinolone-Resistant
Escherichia coli
in the Community
Authors: Garau Javier , Xercavins Mariona , Rodríguez-Carballeira Mónica , Gómez-Vera Josep Ramón , Coll Ignacio , Vidal Dolors , Llovet Teresa , Ruíz-Bremón Ana
Published: October 2018

We studied the evolution of resistance to quinolones in
Escherichia coli
from 1992 to 1997 in Barcelona, Spain. An increasing proportion of quinolone-resistant
E. coli
(QREC) infections was observed. QREC strains were more common in patients with nosocomial infections but also increased in patients with community-acquired infections (9% in 1992 to 17% in 1996). Seventy (12%) of 572 episodes of
E. coli
bacteremia were due to QREC. Factors significantly associated with QREC bacteremia were the presence of underlying disease, recent exposure to antibiotics, and bacteremia of unknown origin. In the multivariate analysis, only prior exposure to antimicrobial agents (
P
< 0.001; odds ratio [OR] = 2), specifically, to quinolones (
P
< 0.001; OR = 14), and the presence of a urinary catheter (
P
< 0.001; OR = 2) were significantly associated with QREC bacteremia. Among 16 QREC isolates from cultures of blood of community origin selected at random, 13 different pulsed-field gel electrophoresis patterns were recognized, showing the genetic diversity of these isolates and in turn indicating the independent emergence of QREC in the community. The prevalence of QREC in the feces of healthy people was unexpectedly high (24% in adults and 26% in children). A survey of the prevalence of QREC of avian and porcine origin revealed a very high proportion of QREC in animal feces (up to 90% of chickens harbored QREC). The high prevalence of QREC in the stools of healthy humans in our area could be linked to the high prevalence of resistant isolates in poultry and pork.
In Vitro Susceptibilities of
Burkholderia mallei
in Comparison to Those of Other Pathogenic
Burkholderia
spp
Authors: Kenny D. J. , Russell P. , Rogers D. , Eley S. M. , Titball R. W.
Published: October 2018

The in vitro antimicrobial susceptibilities of isolates of
Burkholderia mallei
to 16 antibiotics were assessed and compared with the susceptibilities of
Burkholderia pseudomallei
and
Burkholderia cepacia
. The antibiotic susceptibility profile of
B. mallei
resembled that of
B. pseudomallei
more closely than that of
B. cepacia
, which corresponds to their similarities in terms of biochemistry, antigenicity, and pathogenicity. Ceftazidime, imipenem, doxycycline, and ciprofloxacin were active against both
B. mallei
and
B. pseudomallei
. Gentamicin was active against
B. mallei
but not against
B. pseudomallei
. Antibiotics clinically proven to be effective in the treatment of melioidosis may therefore be effective for treating glanders.
Distribution of Insertion Sequence-Like Element IS
1272
and Its Position Relative to Methicillin Resistance Genes in Clinically Important Staphylococci
Authors: Kobayashi Nobumichi , Urasawa Shozo , Uehara Nobuyuki , Watanabe Naoki
Published: October 2018

The distribution of insertion sequence-like element IS
1272
was analyzed for clinical isolates of
Staphylococcus aureus
,
Staphylococcus epidermidis
, and
Staphylococcus haemolyticus
. In each of the staphylococcal species, IS
1272
was detected in both methicillin-resistant (MR) and methicillin-susceptible strains of different genetic types. In MR isolates, IS
1272
was generally located downstream of the truncated
mecR1
gene (Δ
mecR1
), with an identical junction sequence occurring between Δ
mecR1
and IS
1272
, although insertion of an additional gene sequence in the junction sequence was detected in one
S. epidermidis
isolate. These findings suggest that the
mec
element with the rearranged form of
mecR1
(Δ
mecR1
-IS
1272
) has been transmitted to multiple clones of staphylococci.
In Vitro Activities of Gatifloxacin, Two Other Quinolones, and Five Nonquinolone Antimicrobials against Obligately Anaerobic Bacteria
Authors: Schaumann Reiner , Ackermann Grit , Pless Baerbel , Claros Marina C. , Rodloff Arne C.
Published: October 2018

The activity of the new fluoroquinolone gatifloxacin was compared with those of other quinolones and antimicrobial agents of other classes against 294 anaerobes by the broth microdilution technique. For all strains tested, gatifloxacin MICs at which 50 and 90% of the isolates were inhibited were 0.5 and 2 mg/liter, respectively, and were 3 to 4 dilution steps lower than, e.g., ciprofloxacin.
Overexpression of Erg11p by the Regulatable
GAL1
Promoter Confers Fluconazole Resistance in
Saccharomyces cerevisiae
Authors: Kontoyiannis Dimitrios P. , Sagar Namita , Hirschi Kendal D.
Published: October 2018

The contribution of the dosage of target enzyme P-450 14α-demethylase (14αDM) to fluconazole resistance in both
Candida albicans
and
Saccharomyces cerevisiae
remains unclear. Here, we show that overexpression of
Saccharomyces
P-450 14αDM in
S. cerevisiae
, under the control of the regulatable promoter
GAL1
, results in azole resistance.
Activities of Telithromycin (HMR 3647, RU 66647) Compared to Those of Erythromycin, Azithromycin, Clarithromycin, Roxithromycin, and Other Antimicrobial Agents against Unusual Anaerobes
Authors: Goldstein Ellie J. C. , Citron Diane M. , Merriam C. Vreni , Warren Yumi , Tyrrell Kerin
Published: October 2018

The comparative activity of telithromycin (HMR 3647) against 419 human anaerobic isolates was determined by the agar dilution method. At concentrations of ≤0.5 μg/ml, telithromycin was active against
Actinomyces israelii
,
Actinomyces odontolyticus
,
Bacteroides tectum
,
Bacteroides ureolyticus
,
Bacteroides gracilis
(now
Campylobacter gracilis
),
Porphyromonas
spp. (including
Porphyromonas gingivalis
and
Porphyromonas macacae
),
Prevotella intermedia
,
Prevotella heparinolytica
, and almost all
Peptostreptococcus
species. Clostridia showed species and strain variability, often with a biphasic pattern.
Fusobacterium
species, except
Fusobacterium russii
, were relatively resistant.
Distribution of the
cfiA
Gene among
Bacteroides fragilis
Strains in Japan and Relatedness of
cfiA
to Imipenem Resistance
Authors: Yamazoe Kikuo , Kato Naoki , Kato Haru , Tanaka Kaori , Katagiri Yoshihiro , Watanabe Kunitomo
Published: October 2018

The
cfiA
gene, encoding an imipenem-hydrolyzing metallo-β-lactamase produced by
Bacteroides fragilis
, and insertion-like elements were detected by PCR amplification with
B. fragilis
strains isolated in Japan. The
cfiA
gene was found in 1.9 and 4.1% of the imipenem-susceptible
B. fragilis
isolates collected from 1987 to 1988 and from 1992 to 1994, respectively. Insertion-like elements adjacent to the
cfiA
gene were found in all nine metallo-β-lactamase-producing imipenem-resistant strains tested but not in nine
cfiA
-positive strains with no detectable metallo-β-lactamase activity.
Activities of Tobramycin and Six Other Antibiotics against
Pseudomonas aeruginosa
Isolates from Patients with Cystic Fibrosis
Authors: Shawar Ribhi M. , MacLeod David L. , Garber Richard L. , Burns Jane L. , Stapp Jenny R. , Clausen Carla R. , Tanaka S. K.
Published: October 2018

The in vitro activity of tobramycin was compared with those of six other antimicrobial agents against 1,240
Pseudomonas aeruginosa
isolates collected from 508 patients with cystic fibrosis during pretreatment visits as part of the phase III clinical trials of tobramycin solution for inhalation. The tobramycin MIC at which 50% of isolates are inhibited (MIC
50
) and MIC
90
were 1 and 8 μg/ml, respectively. Tobramycin was the most active drug tested and also showed good activity against isolates resistant to multiple antibiotics. The isolates were less frequently resistant to tobramycin (5.4%) than to ceftazidime (11.1%), aztreonam (11.9%), amikacin (13.1%), ticarcillin (16.7%), gentamicin (19.3%), or ciprofloxacin (20.7%). For all antibiotics tested, nonmucoid isolates were more resistant than mucoid isolates. Of 56 isolates for which the tobramycin MIC was ≥16 μg/ml and that were investigated for resistance mechanisms, only 7 (12.5%) were shown to possess known aminoglycoside-modifying enzymes; the remaining were presumably resistant by an incompletely understood mechanism often referred to as “impermeability.”
Activities of a Nitrofurazone-Containing Urinary Catheter and a Silver Hydrogel Catheter against Multidrug-Resistant Bacteria Characteristic of Catheter-Associated Urinary Tract Infection
Authors: Johnson James R. , Delavari Parissa , Azar Miguel
Published: October 2018

The in vitro inhibitory activity of a nitrofurazone-coated urinary catheter (NFC) against 86 recently obtained susceptible and multidrug-resistant (MDR) clinical isolates of
Escherichia coli
,
Klebsiella pneumoniae
,
Citrobacter freundii
,
Staphylococcus aureus
, coagulase-negative
staphylococci
, and
Enterococcus faecium
, which are species implicated in catheter-associated urinary tract infection and which traditionally have been susceptible to nitrofuran derivatives, was determined using an agar diffusion assay. In a subset of these strains, the activity of the NFC was compared with that of a silver hydrogel urinary catheter (SHC), and the durability of each catheter’s inhibitory activity was assessed during serial daily transfers of catheter segments to fresh culture plates. Except for vancomycin-resistant
E. faecium
, the NFC was active against all isolates tested and showed comparable inhibition zones with susceptible and MDR strains of each species. In contrast, the SHC inhibited only certain staphylococci (
P
< 0.01 versus the NFC), and among these strains, the SHC produced smaller inhibition zones than did the NFC (
P
< 0.01). Inhibition was evident for up to 5 days with the NFC, but for only 1 day (if at all) with the SHC (
P
< 0.01). These data document that, for most genera which traditionally have been susceptible to nitrofuran derivatives, the NFC remains active against contemporary MDR isolates. They also demonstrate that the in vitro antibacterial activity of the NFC is markedly superior to that of the SHC in several respects. Thus, the NFC shows promise for clinical use in the current era of MDR bacteria.
Comparative Bacteriostatic and Bactericidal Activities of Cefodizime against
Borrelia burgdorferi
Sensu Lato
Authors: Murgia Rossella , Marchetti Federico , Cinco Marina
Published: October 2018

The MIC and MSC (minimum spirocheticidal concentration) and killing rate for
Borrelia burgdorferi
, the etiological agent of Lyme disease, were assessed for cefodizime in comparison with ceftriaxone, minocycline, azithromycin, roxithromycin, and ciprofloxacin. The range of cefodizime MICs was greater than those of azithromycin and roxithromycin but comparable to those of ceftriaxone and minocycline. The MSCs were 1 to 2 dilutions higher than the MICs of all of the tested compounds. The killing curves of cefodizime and ceftriaxone showed parallel courses. In conclusion, cefodizime exerted an activity comparable to that of ceftriaxone against
B. burgdorferi
.
Variation in the Composition and Pore Function of Major Outer Membrane Pore Protein P2 of
Haemophilus influenzae
from Cystic Fibrosis Patients
Authors: Regelink Annette G. , Dahan David , Möller Lieke V. M. , Coulton James W. , Eijk Paul , Van Ulsen Peter , Dankert Jacob , Van Alphen Loek
Published: October 2018

We investigated the relationship between susceptibility to β-lactam antibiotics and variation in the major outer membrane protein P2 (OmpP2; also called porin) of persistent nonencapsulated
Haemophilus influenzae
isolated from cystic fibrosis patients. Nine OmpP2 variants were selected from two distinct
H. influenzae
strains from two patients extensively treated with β-lactam antibiotics. The variants differed in their susceptibilities to at least two β-lactam antibiotics. By detergent extraction and column chromatography, OmpP2 was purified from two variants that were derived from strain 70 and that differed notably in their susceptibilities to β-lactam antibiotics. The proteins were reconstituted into black lipid membranes for measurement of porin function. OmpP2 from the more resistant isolate (isolate 70b) had a smaller channel conductance than OmpP2 of the more susceptible isolate (isolate 70f). DNA sequencing of
ompP2
of these isolates revealed single nonsynonymous base differences; there were changes in the amino acid sequence corresponding to surface-exposed loops 4, 5, 6, and 8. Changes in loops 4, 5, and 6 were previously shown to result in antigenic differences. Beside these mutations, variants of strain 70 showed additional mutations in loop 1 and nonexposed loop 3. Taken together, our results suggest that in variants of strain 70, nonsynonymous point mutations accumulated both in the sequences of
ompP2
coding for antigen-variable loops and in other loops, notably, loops 1 and 3. The latter changes are suggested to affect the permeability of the porin channel.
Clinical Pharmacokinetics of 1-[((
S
)-2-Hydroxy-2-Oxo-1,4,2-Dioxaphosphorinan-5-yl)methyl]cytosine in Human Immunodeficiency Virus-Infected Patients
Authors: Cundy Kenneth C. , Barditch-Crovo Patricia , Petty Brent G. , Ruby April , Redpath Murphy , Jaffe Howard S. , Lietman Paul S.
Published: October 2018

The pharmacokinetics and bioavailability of 1-[((
S
)-2-hydroxy-2-oxo-1,4,2-dioxaphosphorinan-5-yl)methyl]cytosine (cyclic HPMPC) were examined at four doses in 22 patients with human immunodeficiency virus infection. Two groups of six patients received a single dose of cyclic HPMPC at 1.5 or 3.0 mg/kg of body weight by each of the oral and intravenous routes in a random order with a 2-week washout period between administrations. Additional patients received single intravenous doses of cyclic HPMPC at 5.0 mg/kg (
n
= 6) or 7.5 mg/kg (
n
= 4). Serial serum and urine samples were collected at intervals over 24 h after dosing. The concentrations of cyclic HPMPC and cidofovir in serum and urine samples were determined by validated reverse-phase ion-pairing high-performance liquid chromatography methods with derivatization and fluorescence detection. After intravenous administration of cyclic HPMPC, concentrations of cyclic HPMPC declined in a biexponential manner, with a mean ± standard deviation half-life of 1.09 ± 0.12 h (
n
= 22). The pharmacokinetics of cyclic HPMPC were independent of dose over the dose range of 1.5 to 7.5 mg/kg. The total clearance of cyclic HPMPC from serum and the volume of distribution of intravenous cyclic HPMPC were 198 ± 39.6 ml/h/kg and 338 ± 65.1 ml/kg, respectively (
n
= 22). The renal clearance of cyclic HPMPC (132 ± 27.3 ml/h/kg;
n
= 22) exceeded the creatinine clearance (86.2 ± 16.3 ml/h/kg), indicating active tubular secretion. The cyclic HPMPC excreted in urine in 24 h accounted for 71.3% ± 16.0% of the administered dose. Cidofovir was formed from cyclic HPMPC in vivo with a time to the maximum concentration in serum of 1.64 ± 0.23 h (
n
= 22). Cidofovir levels declined in an apparent monoexponential manner, with a mean terminal half-life of 3.98 ± 1.26 h (
n
= 22). The cidofovir excreted in urine in 24 h accounted for 9.40% ± 2.33% of the administered cyclic HPMPC dose. Exposure to cidofovir after intravenous administration of cyclic HPMPC was dose proportional and was 14.9% of that from an equivalent dose of cidofovir. The present study suggests that intravenous cyclic HPMPC also has a lower potential for nephrotoxicity in humans compared to that of intravenous cidofovir. The oral bioavailabilities of cyclic HPMPC were 1.76% ± 1.48% and 3.10% ± 1.16% with the administration of doses of 1.5 and 3.0 mg/kg, respectively (
n
= 6 per dose). The maximum concentrations of cyclic HPMPC in serum were 0.036 ± 0.021 and 0.082 ± 0.038 μg/ml after the oral administration of doses of 1.5 and 3.0 mg/kg, respectively. Cidofovir reached quantifiable levels in the serum of only one patient for each of the 1.5- and 3.0-mg/kg oral cyclic HPMPC doses.
Characterization and Nucleotide Sequence of CARB-6, a New Carbenicillin-Hydrolyzing β-Lactamase from
Vibrio cholerae
Authors: Choury Danièle , Aubert Gérald , Szajnert Marie-France , Azibi Kemal , Delpech Marc , Paul Gérard
Published: October 2018

A clinical strain of
Vibrio cholerae
non-O1 non-O139 isolated in France produced a new β-lactamase with a pI of 5.35. The purified enzyme, with a molecular mass of 33,000 Da, was characterized. Its kinetic constants show it to be a carbenicillin-hydrolyzing enzyme comparable to the five previously reported CARB β-lactamases and to SAR-1, another carbenicillin-hydrolyzing β-lactamase that has a pI of 4.9 and that is produced by a
V. cholerae
strain from Tanzania. This β-lactamase is designated CARB-6, and the gene for CARB-6 could not be transferred to
Escherichia coli
K-12 by conjugation. The nucleotide sequence of the structural gene was determined by direct sequencing of PCR-generated fragments from plasmid DNA with four pairs of primers covering the whole sequence of the reference CARB-3 gene. The gene encodes a 288-amino-acid protein that shares 94% homology with the CARB-1, CARB-2, and CARB-3 enzymes, 93% homology with the
Proteus mirabilis
N29 enzyme, and 86.5% homology with the CARB-4 enzyme. The sequence of CARB-6 differs from those of CARB-3, CARB-2, CARB-1, N29, and CARB-4 at 15, 16, 17, 19, and 37 amino acid positions, respectively. All these mutations are located in the C-terminal region of the sequence and at the surface of the molecule, according to the crystal structure of the
Staphylococcus aureus
PC-1 β-lactamase.
Efflux Pump-Mediated Quinolone Resistance in
Staphylococcus aureus
Strains Wild Type for
gyrA
,
gyrB
,
grlA
, and
norA
Authors: Muñoz-Bellido Juan Luis , Manzanares M. A. Alonso , Andrés J. A. Martínez , Zufiaurre M. N. Gutiérrez , Ortiz G. , Hernández M. Segovia , García-Rodríguez J. A.
Published: October 2018

Fluoroquinolone efflux was studied in 47
Staphylococcus aureus
clinical strains with MICs of ciprofloxacin (CFX) of ≤2 μg/ml. Forty-three strains were wild type for
gyrA
,
gyrB
, and
grlA
quinolone resistance-determining regions and for
norA
and its promoter region. Forty of these strains (MICs of CFX, 0.1 to 0.2 μg/ml) did not show efflux of fluoroquinolones. Three strains (MICs of CFX, 1 to 2 μg/ml) showed efflux. These results suggest that efflux can appear in
S. aureus
clinical strains in the absence of mutations in
norA
and its promoter.
Activity of a Heat-Induced Reformulation of Amphotericin B Deoxycholate (Fungizone) against
Leishmania donovani
Authors: Petit C. , Yardley V. , Gaboriau F. , Bolard J. , Croft S. L.
Published: October 2018

The heat treatment of amphotericin B deoxycholate (Fungizone), which was previously shown to induce superaggregation and decrease the toxicity of the drug to mammalian cells, increased its activity against
Leishmania donovani
in BALB/c mice, whereas it reduced its toxicity. Heat treatment preserved the activity of Fungizone against
L. donovani
HU3-infected mouse peritoneal macrophages.
Diversification of
Escherichia coli
Expressing an SHV-Type Extended-Spectrum β-Lactamase (ESBL) during a Hospital Outbreak: Emergence of an ESBL-Hyperproducing Strain Resistant to Expanded-Spectrum Cephalosporins
Authors: Pałucha Andrzej , Mikiewicz Barbara , Gniadkowski Marek
Published: October 2018

Twelve SHV-type extended-spectrum β-lactamase (ESBL)-producing
Escherichia coli lac
mutant isolates were recovered in October 1997 from 11 patients of the neonatal ward in a Warsaw hospital. The outbreak was clonal; however, some of the isolates expressed a much higher level of resistance to several β-lactam antibiotics, including expanded-spectrum cephalosporins. This phenotype has been attributed to β-lactamase hyperproduction correlating with the multiplication of ESBL gene copies, as was demonstrated for representative isolates.
Prediction of the Effects of Inoculum Size on the Antimicrobial Action of Trovafloxacin and Ciprofloxacin against
Staphylococcus aureus
and
Escherichia coli
in an In Vitro Dynamic Model
Authors: Firsov Alexander A. , Vostrov Sergey N. , Kononenko Olga V. , Zinner Stephen H. , Portnoy Yury A.
Published: October 2018

The effect of inoculum size (
N
0
) on antimicrobial action has not been extensively studied in in vitro dynamic models. To investigate this effect and its predictability, killing and regrowth kinetics of
Staphylococcus aureus
and
Escherichia coli
exposed to monoexponentially decreasing concentrations of trovafloxacin (as a single dose) and ciprofloxacin (two doses at a 12-h interval) were compared at
N
0
= 10
6
and 10
9
CFU/ml (
S. aureus
) and at
N
0
= 10
6
, 10
7
, and 10
9
CFU/ml (
E. coli
). A series of pharmacokinetic profiles of trovafloxacin and ciprofloxacin with respective half-lives of 9.2 and 4 h were simulated at different ratios of area under the concentration-time curve (AUC) to MIC (in [micrograms × hours/milliliter]/[micrograms/milliliter]): 58 to 466 with trovafloxacin and 116 to 932 with ciprofloxacin for
S. aureus
and 58 to 233 and 116 to 466 for
E. coli
, respectively. Although the effect of
N
0
was more pronounced for
E. coli
than for
S. aureus
, only a minor increase in minimum numbers of surviving bacteria and an almost negligible delay in their regrowth were associated with an increase of the
N
0
for both organisms. The
N
0
-induced reductions of the intensity of the antimicrobial effect (

I
E

, area between control growth and the killing-regrowth curves) were also relatively small. However, the
N
0
effect could not be eliminated either by simple shifting of the time-kill curves obtained at higher
N
0
s by the difference between the higher and lowest
N
0
or by operating with

I
E

s determined within the
N
0
-adopted upper limits of bacterial numbers (

I
E

′s). By using multivariate correlation and regression analyses, linear relationships between

I
E

and log AUC/MIC and log
N
0
related to the respective mean values [(log AUC/MIC)
average
and (log
N
0
)
average
] were established for both trovafloxacin and ciprofloxacin against each of the strains (
r
2
= 0.97 to 0.99). The antimicrobial effect may be accurately predicted at a given AUC/MIC of trovafloxacin or ciprofloxacin and at a given
N
0
based on the relationship

I
E
= a + b

[(log AUC/MIC)/(log AUC/MIC)
average
] −
c
[(log
N
0
)/(log
N
0
)
average
]. Moreover, the relative impacts of AUC/MIC and
N
0
on

I
E

may be evaluated. Since the
c/b
ratios for trovafloxacin and ciprofloxacin against
E. coli
were much lower (0.3 to 0.4) than that for ampicillin-sulbactam as examined previously (1.9), the inoculum effect with the quinolones may be much less pronounced than with the β-lactams. The described approach to the analysis of the inoculum effect in in vitro dynamic models might be useful in studies with other antibiotic classes.
Pharmacokinetics of Ethambutol under Fasting Conditions, with Food, and with Antacids
Authors: Peloquin Charles A. , Bulpitt Amy E. , Jaresko George S. , Jelliffe Roger W. , Childs James M. , Nix David E.
Published: October 2018

Ethambutol (EMB) is the most frequent “fourth drug” used for the empiric treatment of
Mycobacterium tuberculosis
and a frequently used drug for infections caused by
Mycobacterium avium
complex. The pharmacokinetics of EMB in serum were studied with 14 healthy males and females in a randomized, four-period crossover study. Subjects ingested single doses of EMB of 25 mg/kg of body weight under fasting conditions twice, with a high-fat meal, and with aluminum-magnesium antacid. Serum was collected for 48 h and assayed by gas chromatography-mass spectrometry. Data were analyzed by noncompartmental methods and by a two-compartment pharmacokinetic model with zero-order absorption and first-order elimination. Both fasting conditions produced similar results: a mean (± standard deviation) EMB maximum concentration of drug in serum (
C
max
) of 4.5 ± 1.0 μg/ml, time to maximum concentration of drug in serum (
T
max
) of 2.5 ± 0.9 h, and area under the concentration-time curve from 0 h to infinity (AUC
0–∞
) of 28.9 ± 4.7 μg · h/ml. In the presence of antacids, subjects had a mean
C
max
of 3.3 ± 0.5 μg/ml,
T
max
of 2.9 ± 1.2 h, and AUC
0–∞
of 27.5 ± 5.9 μg · h/ml. In the presence of the Food and Drug Administration high-fat meal, subjects had a mean
C
max
of 3.8 ± 0.8 μg/ml,
T
max
of 3.2 ± 1.3 h, and AUC
0–∞
of 29.6 ± 4.7 μg · h/ml. These reductions in
C
max
, delays in
T
max
, and modest reductions in AUC
0–∞
can be avoided by giving EMB on an empty stomach whenever possible.
Antimicrobial Activities of Synthetic Bismuth Compounds against
Clostridium difficile
Authors: Mahony D. E. , Lim-Morrison S. , Bryden L. , Faulkner G. , Hoffman P. S. , Agocs L. , Briand G. G. , Burford N. , Maguire H.
Published: October 2018

Clostridium difficile
is a major nosocomial pathogen responsible for pseudomembranous colitis and many cases of antibiotic-associated diarrhea. Because of potential relapse of disease with current antimicrobial therapy protocols, there is a need for additional and/or alternative antimicrobial agents for the treatment of disease caused by
C. difficile
. We have synthesized a systematic series of 14 structurally simple bismuth compounds and assessed their biological activities against
C. difficile
and four other gastrointestinal species, including
Helicobacter pylori
. Here, we report on the activities of six compounds that exhibit antibacterial activities against
C. difficile
, and some of the compounds have MICs of less than 1 μg/ml. Also tested, for comparison, were the activities of bismuth subcitrate and ranitidine bismuth citrate obtained from commercial sources.
C. difficile
and
H. pylori
were more sensitive both to the synthetic bismuth compounds and to the commercial products than were
Escherichia coli
,
Pseudomonas aeruginosa
, and
Proteus mirabilis
, and the last three species were markedly resistant to the commercial bismuth salts. Testing with human foreskin fibroblast cells revealed that some of the synthetic compounds were more cytotoxic than others. Killing curves for
C. difficile
treated with the more active compounds revealed rapid death, and electron microscopy showed that the bismuth of these compounds was rapidly incorporated by
C. difficile
. Energy dispersive spectroscopy X-ray microanalysis of
C. difficile
cells containing electron-dense material confirmed the presence of internalized bismuth. Internalized bismuth was not observed in
C. difficile
treated with synthetic bismuth compounds that lacked antimicrobial activity, which suggests that the uptake of the metal is required for killing activity. The nature of the carrier would seem to determine whether bismuth is transported into susceptible bacteria like
C. difficile
.
Clindamycin Suppresses Endotoxin Released by Ceftazidime-Treated
Escherichia coli
O55:B5 and Subsequent Production of Tumor Necrosis Factor Alpha and Interleukin-1β
Authors: Kishi Kenji , Hirai Kazuhiro , Hiramatsu Kazufumi , Yamasaki Tohru , Nasu Masaru
Published: October 2018

Treatment of septicemia caused by
Escherichia coli
with ceftazidime (CAZ) may be associated with the development of septic shock due to the release of bacterial lipopolysaccharide. We examined the suppressive effect of clindamycin (CLDM) on CAZ-induced release of endotoxin by cultured
E. coli
and the subsequent production of inflammatory cytokines (tumor necrosis factor alpha [TNF-α] and interleukin-1β [IL-1β]).
E. coli
ATCC 12014 was incubated in inactivated horse serum with or without CLDM for 1, 4, or 18 h, followed by the addition of CAZ and collection of the culture supernatant at 0, 1, and 2 h. The concentration of endotoxin in each sample was measured by a chromogenic
Limulus
test. Another portion of the culture supernatant was added to THP-1 cell culture and incubated for 4 h, and the concentrations of TNF-α and IL-1β in the supernatant were measured by an enzyme-linked immunosorbent assay. In the control group (no CLDM), CAZ administration resulted in significant increases in endotoxin, TNF-α, and IL-1β concentrations. Pretreatment of
E. coli
with CLDM for 4 or 18 h before the addition of CAZ significantly suppressed the concentrations of endotoxin, TNF-α, and IL-1β in a time-dependent manner. In addition, CAZ treatment transformed
E. coli
from rod-shaped bacteria to filament-like structures, as determined by electron microscopy, while pretreatment with CLDM prevented these morphological changes. Our in vitro studies showed that CAZ-induced release of large quantities of endotoxin by
E. coli
could be suppressed by prior administration of CLDM.
Single-Dose Pharmacokinetics of a Pleconaril (VP63843) Oral Solution in Children and Adolescents
Authors: Kearns Gregory L. , Abdel-Rahman Susan M. , James Laura P. , Blowey Douglas L. , Marshall James D. , Wells Thomas G. , Jacobs Richard F. ,   The Pediatric Pharmacology Research Unit Network
Published: October 2018

Pleconaril is an orally active, broad-spectrum antipicornaviral agent which demonstrates excellent penetration into the central nervous system, liver, and nasal epithelium. In view of the potential pediatric use of pleconaril, we conducted a single-dose, open-label study to characterize the pharmacokinetics of this antiviral agent in pediatric patients. Following an 8- to 10-h period of fasting, 18 children ranging in age from 2 to 12 years (7.5 ± 3.1 years) received a single 5-mg/kg of body weight oral dose of pleconaril solution administered with a breakfast of age-appropriate composition. Repeated blood samples (
n
= 10) were obtained over 24 h postdose, and pleconaril was quantified from plasma by gas chromatography. Plasma drug concentration-time data for each subject were fitted to the curve by using a nonlinear, weighted (weight = 1/
Y
calc
) least-squares algorithm, and model-dependent pharmacokinetic parameters were determined from the polyexponential parameter estimates. Pleconaril was well tolerated by all subjects. A one-compartment open-model with first-order absorption best described the plasma pleconaril concentration-time profile in 13 of the subjects over a 24-h postdose period. Pleconaril pharmacokinetic parameters (means ± standard deviations) for these 13 patients were as follows. The maximum concentration of the drug in serum (
C
max
) was 1,272.5 ± 622.1 ng/ml. The time to
C
max
was 4.1 ± 1.5 h, and the lag time was 0.75 ± 0.56 h. The apparent absorption rate constant was 0.75 ± 0.48 1/h, and the elimination rate constant was 0.16 ± 0.07 1/h. The area under the concentration-time curve from 0 to 24 h was 8,131.15 ± 3,411.82 ng · h/ml. The apparent total plasma clearance was 0.81 ± 0.86 liters/h/kg, and the apparent steady-state volume of distribution was 4.68 ± 2.02 liters/kg. The mean elimination half-life of pleconaril was 5.7 h. The mean plasma pleconaril concentrations at both 12 h (250.4 ± 148.2 ng/ml) and 24 h (137.9 ± 92.2 ng/ml) after the single 5-mg/kg oral dose in children were higher than that from in vitro studies reported to inhibit >90% of nonpolio enterovirus serotypes (i.e., 70 ng/ml). Thus, our data support the evaluation of a 5-mg/kg twice-daily oral dose of pleconaril for therapeutic trials in pediatric patients with enteroviral infections.
Genetic Evidence that InhA of
Mycobacterium smegmatis
Is a Target for Triclosan
Authors: McMurry Laura M. , McDermott Patrick F. , Levy Stuart B.
Published: October 2018

Three
Mycobacterium smegmatis
mutants selected for resistance to triclosan each had a different mutation in InhA, an enoyl reductase involved in fatty acid synthesis. Two expressed some isoniazid resistance. A mutation originally selected on isoniazid also mediated triclosan resistance, as did the wild-type
inhA
gene on a multicopy plasmid. Replacement of the mutant chromosomal
inhA
genes with wild-type
inhA
eliminated resistance. These results suggest that
M. smegmatis
InhA, like its
Escherichia coli
homolog FabI, is a target for triclosan.
Lactic Acid Polymers as Biodegradable Carriers of Fluoroquinolones: An In Vitro Study
Authors: Kanellakopoulou Kyriaki , Kolia Maria , Anastassiadis Antonios , Korakis Themistoklis , Giamarellos-Bourboulis Evangelos J. , Andreopoulos Andreas , Dounis Eleftherios , Giamarellou Helen
Published: October 2018

A biodegradable polymer of
dl
-dilactide that facilitates release of ciprofloxacin or pefloxacin at levels exceeding MICs for the causative microorganisms of chronic osteomyelitis is described. Duration and peak of release were found to depend on the molecular weight of the polymer. Its characteristics make it promising for treating chronic bone infections.
Exposure to Metronidazole In Vivo Readily Induces Resistance in
Helicobacter pylori
and Reduces the Efficacy of Eradication Therapy in Mice
Authors: Jenks Peter J. , Labigne Agnes , Ferrero Richard L.
Published: October 2018

The
Helicobacter pylori
SS1 mouse model was used to characterize the development of resistance in
H. pylori
after treatment with metronidazole monotherapy and to examine the effect of prior exposure to metronidazole on the efficacy of a metronidazole-containing eradication regimen. Mice colonized with the metronidazole-sensitive
H. pylori
SS1 strain were treated for 7 days with either peptone trypsin broth or the mouse equivalent of 400 mg of metronidazole once a day or three times per day (TID). In a separate experiment,
H. pylori
-infected mice were administered either peptone trypsin broth or the mouse equivalent of 400 mg of metronidazole TID for 7 days, followed 1 month later by either peptone trypsin broth or the mouse equivalent of 20 mg of omeprazole, 250 mg of clarithromycin, and 400 mg of metronidazole twice a day for 7 days. At least 1 month after the completion of treatment, the mice were sacrificed and their stomachs were cultured for
H. pylori
. The susceptibilities of isolates to metronidazole were assessed by agar dilution determination of the MICs. Mixed populations of metronidazole-resistant and -sensitive strains were isolated from 70% of mice treated with 400 mg of metronidazole TID. The ratio of resistant to sensitive strains was 1:100, and the MICs for the resistant strains varied from 8 to 64 μg/ml. In the second experiment,
H. pylori
was eradicated from 70% of mice treated with eradication therapy alone, compared to 25% of mice pretreated with metronidazole (
P
< 0.01). Mice still infected after treatment with metronidazole and eradication therapy contained mixed populations of metronidazole-resistant and -sensitive isolates in a ratio of 1:25. These results demonstrate that
H. pylori
readily acquires resistance to metronidazole in vivo and that prior exposure of the organism to metronidazole is associated with failure of eradication therapy.
H. pylori
-infected mice provide a suitable model for the study of resistance mechanisms in
H. pylori
and will be useful in determining optimal regimens for the eradication of resistant strains.
Development of Resistance during Antimicrobial Therapy Caused by Insertion Sequence Interruption of Porin Genes
Authors: Hernández-Allés Santiago , Benedí Vicente J. , Martínez-Martínez Luis , Pascual Álvaro , Aguilar Alicia , Tomás Juan M. , Albertí Sebastián
Published: October 2018

We have demonstrated by using an in vitro approach that interruption of the OmpK36 porin gene by insertion sequences (ISs) is a common type of mutation that causes loss of porin expression and increased resistance to cefoxitin in
Klebsiella pneumoniae
. This mechanism also operates in vivo: of 13 porin-deficient cefoxitin-resistant clinical isolates of
K. pneumoniae
, 4 presented ISs in their
ompK36
gene.
Mutations in the
gyrA
,
parC
, and
parE
Genes Associated with Fluoroquinolone Resistance in Clinical Isolates of
Mycoplasma hominis
Authors: Bebear Cécile M. , Renaudin Joel , Charron Alain , Renaudin Hélène , de Barbeyrac Bertille , Schaeverbeke Thierry , Bebear Christiane
Published: October 2018

Five clinical isolates of
Mycoplasma hominis
from three different patients were examined for resistance to fluoroquinolones; some of these isolates were probably identical. All five isolates harbored amino acid substitutions in the quinolone resistance-determining regions of both DNA gyrase (GyrA) and topoisomerase IV (ParC or ParE). Furthermore, the novobiocin MIC for three isolates showed a significant increase. This is the first characterization of fluoroquinolone-resistant clinical mycoplasma isolates from humans.