bluuebunny/crossref_metadata_2025 huggingface dataset:
CNS Synaptogenesis Promoted by Glia-Derived Cholesterol
Authors: Mauch Daniela H. , Nägler Karl , Schumacher Stefan , Göritz Christian , Müller Eva-Christina , Otto Albrecht , Pfrieger Frank W.
Published: July 2002

The molecular mechanisms controlling synaptogenesis in the central nervous system (CNS) are poorly understood. Previous reports showed that a glia-derived factor strongly promotes synapse development in cultures of purified CNS neurons. Here, we identify this factor as cholesterol complexed to apolipoprotein E–containing lipoproteins. CNS neurons produce enough cholesterol to survive and grow, but the formation of numerous mature synapses demands additional amounts that must be provided by glia. Thus, the availability of cholesterol appears to limit synapse development. This may explain the delayed onset of CNS synaptogenesis after glia differentiation and neurobehavioral manifestations of defects in cholesterol or lipoprotein homeostasis.
Antimycobacterial Activities of 2,4-Diamino-5-Deazapteridine Derivatives and Effects on Mycobacterial Dihydrofolate Reductase
Authors: Suling William J. , Seitz Lainne E. , Pathak Vibha , Westbrook Louise , Barrow Esther W. , Zywno-van-Ginkel Sabrina , Reynolds Robert C. , Piper J. Robert , Barrow William W.
Published: July 2002

Development of new antimycobacterial agents for
Mycobacterium avium
complex (MAC) infections is important particularly for persons coinfected with human immunodeficiency virus. The objectives of this study were to evaluate the in vitro activity of 2,4-diamino-5-methyl-5-deazapteridines (DMDPs) against MAC and to assess their activities against MAC dihydrofolate reductase recombinant enzyme (rDHFR). Seventy-seven DMDP derivatives were evaluated initially for in vitro activity against one to three strains of MAC (NJ168, NJ211, and/or NJ3404). MICs were determined with 10-fold dilutions of drug and a colorimetric (Alamar Blue) microdilution broth assay. MAC rDHFR 50% inhibitory concentrations versus those of human rDHFR were also determined. Substitutions at position 5 of the pteridine moiety included -CH
3
, -CH
2
CH
3
, and -CH
2
OCH
3
groups. Additionally, different substituted and unsubstituted aryl groups were linked at position 6 through a two-atom bridge of either -CH
2
NH, -CH
2
N(CH
3
), -CH
2
CH
2
, or -CH
2
S. All but 4 of the 77 derivatives were active against MAC NJ168 at concentrations of ≤13 μg/ml. Depending on the MAC strain used, 81 to 87% had MICs of ≤1.3 μg/ml. Twenty-one derivatives were >100-fold more active against MAC rDHFR than against human rDHFR. In general, selectivity was dependent on the composition of the two-atom bridge at position 6 and the attached aryl group with substitutions at the 2′ and 5′ positions on the phenyl ring. Using this assessment, a rational synthetic approach was implemented that resulted in a DMDP derivative that had significant intracellular activity against a MAC-infected Mono Mac 6 monocytic cell line. These results demonstrate that it is possible to synthesize pteridine derivatives that have selective activity against MAC.
Detection of the High-Level Aminoglycoside Resistance Gene
aph(2")-Ib
in
Enterococcus faecium
Authors: Kao Susan J. , You Il , Clewell Don B. , Donabedian Susan M. , Zervos Marcus J. , Petrin Joanne , Shaw Karen J. , Chow Joseph W.
Published: July 2002

A new high-level gentamicin resistance gene, designated
aph(2")-Ib
, was cloned from
Enterococcus faecium
SF11770. The deduced amino acid sequence of the 897-bp open reading frame of
aph(2")-Ib
shares homology with the aminoglycoside-modifying enzymes AAC(6′)-APH(2"), APH(2")-Ic, and APH(2")-Id. The observed phosphotransferase activity is designated APH(2")-Ib.
Multiple-Antibiotic Resistance Mediated by Structurally Related IncL/M Plasmids Carrying an Extended-Spectrum β-Lactamase Gene and a Class 1 Integron
Authors: Villa Laura , Pezzella Cristina , Tosini Fabio , Visca Paolo , Petrucca Andrea , Carattoli Alessandra
Published: July 2002

A conjugative IncL/M plasmid (pSEM) conferring resistance to gentamicin, amikacin, kanamycin, sulfonamides, and expanded-spectrum cephalosporins was found in pathogenic strains of
Salmonella enterica
serotype Typhimurium. Resistance to aminoglycosides was encoded by a
sul1
-type class 1 integron (In-t3). An extended-spectrum beta-lactamase gene,
bla
SHV-5
, was identified 3.5 kb downstream of the integrase (
intI1
) gene of In-t3. Nucleotide sequence analysis of the 5.3-kb
bla
SHV-5
–In-t3 region of pSEM highlighted striking similarities with IncL/M plasmids isolated from nosocomial gram-negative pathogens, conferring resistance to expanded-spectrum cephalosporins and aminoglycosides.
Activity of LY333328 Combined with Gentamicin In Vitro and in Rabbit Experimental Endocarditis Due to Vancomycin-Susceptible or -Resistant
Enterococcus faecalis
Authors: Lefort Agnès , Saleh-Mghir Azzam , Garry Louis , Carbon Claude , Fantin Bruno
Published: July 2002

We investigated the activity of LY333328 alone and combined with gentamicin, both in vitro and in a rabbit model of experimental endocarditis, against the susceptible strain
Enterococcus faecalis
JH2-2 and its two glycopeptide-resistant transconjugants, BM4316 (VanA) and BM4275 (VanB). MICs of LY333328 and gentamicin were 2 and 16 μg/ml, respectively, for the three strains. In vitro, LY333328 alone was bactericidal at 24 h against JH2-2 at a concentration of 2 μg/ml and against BM4316 and BM4275 at a concentration of 30 μg/ml. The combination of LY333328 and gentamicin (4 μg/ml) was synergistic and bactericidal after 24 h of incubation against the three strains at LY333328 concentrations of 2 μg/ml for JH2-2 and 8 μg/ml for BM4275 and BM4316. The combination of LY333328 and gentamicin was the only regimen demonstrating in vitro bactericidal activity against BM4316. In vivo, intravenous treatment with LY333328 alone, providing peak and trough serum levels of 83.3 ± 1.3 and 3.8 ± 0.2 μg/ml, respectively, was inactive against BM4316 and BM4275 and selected mutants resistant to LY333328 in half of the rabbits infected with the VanA-type strain (MICs, 8 to 20 μg/ml). However, the LY333328-gentamicin combination was active against the three strains and prevented the emergence of mutants resistant to both components of the combination. We conclude that the LY333328-gentamicin combination might be of interest for the treatment of enterococcal infections, particularly against VanA-type strains.
Therapeutic Efficacy of GAR-936, a Novel Glycylcycline, in a Rat Model of Experimental Endocarditis
Authors: Murphy Timothy M. , Deitz Jacqueline M. , Petersen Peter J. , Mikels Susan M. , Weiss William J.
Published: July 2002

GAR-936, a novel glycylcycline, was investigated with a rat model of experimental endocarditis. It was compared with vancomycin against both vancomycin-susceptible and -resistant
Enterococcus faecalis
and methicillin-resistant
Staphylococcus aureus
. GAR-936 exhibited the lowest MICs (≤0.12 μg/ml) in vitro against each of the isolates tested. Endocarditis was established by placement of a catheter across the aortic valve, followed by intravenous injection of 10
6
CFU of bacteria 48 h later. Treatment with GAR-936 or vancomycin was initiated 24 to 36 h after bacterial infection and administered subcutaneously twice a day for 3 days at ascending doses. GAR-936 reduced bacterial vegetation titers by >2 log
10
CFU, compared to those in untreated controls, for both vancomycin-susceptible and -resistant (VanA and VanB)
E. faecalis
strains and >4 log
10
CFU for a methicillin-resistant
S. aureus
isolate. The glycylcycline was more efficacious at a lower administered dose in the rat model of endocarditis than was vancomycin. The efficacy of GAR-936 in this model was apparently not enhanced by a factor in rat serum, as was observed for vancomycin with a time-kill curve. The results of this study demonstrate the therapeutic potential of GAR-936 for the treatment of enterococcal and staphylococcal infections and warrant further investigation.
Low Level of Cross-Resistance to Amprenavir (141W94) in Samples from Patients Pretreated with Other Protease Inhibitors
Authors: Schmidt Barbara , Korn Klaus , Moschik Brigitte , Paatz Christiane , Überla Klaus , Walter Hauke
Published: July 2002

The therapeutic success of an antiretroviral salvage regimen containing protease inhibitors (PI) is limited by PI-resistant viral strains exhibiting various degrees of resistance and cross-resistance. To evaluate the extent of cross-resistance to the new PI amprenavir, 155 samples from 132 human immunodeficiency virus type 1-infected patients were analyzed for viral genotype by direct sequencing of the protease gene. Concomitantly, drug sensitivity to indinavir, saquinavir, ritonavir, nelfinavir, and amprenavir was analyzed by a recombinant virus assay. A total of 111 patients had been pretreated with 1-4 PI, but all were naive to amprenavir. A total of 105 samples (67.7%) were sensitive to amprenavir; 25 samples (16.1%) were intermediately resistant, and another 25 samples were highly resistant (4- to 8-fold- and >8-fold-reduced sensitivity, respectively). The mutations 46I/L, 54L/V, 84V, and 90M showed the strongest association with amprenavir resistance (
P
< 0.0001). The scoring system using 84V and/or any two of a number of mutations (10I/R/V/F, 46I/L, 54L/V, and 90M) predicted amprenavir resistance with a sensitivity of 86.0% and a specificity of 81.0% within the analyzed group of samples. Of 62 samples with resistance against 4 PI, 23 (37.1%) were still sensitive to amprenavir. In comparison, only 2 of 23 samples (8.7%) from nelfinavir-naive patients with resistance against indinavir, saquinavir, and ritonavir were still sensitive to nelfinavir. Amprenavir thus appears to be an interesting alternative for PI salvage therapy.
Characterization of Novel Human Hepatoma Cell Lines with Stable Hepatitis B Virus Secretion for Evaluating New Compounds against Lamivudine- and Penciclovir-Resistant Virus
Authors: Fu Lei , Cheng Yung-Chi
Published: July 2002

l-Nucleoside analogs are new therapeutic agents for treatment of chronic hepatitis B. However, their clinical application was limited by the emergence of viral resistance. It is important to develop a new system to evaluate drug cross-resistance and to test new agents that may overcome resistant virus. In this report, three cell lines HepG2-WT10, HepG2-SM1, and HepG2-DM2 are presented; these cell lines were established by transfection of HepG2 cells with unique fully functional 1.1× hepatitis B virus (HBV) genomes: wild-type HBV-adr and its L526M and L526MM550V variants, respectively. We have demonstrated that these genomes have different susceptibilities to lamivudine [l(−)SddC] and penciclovir (PCV). By examining HBV RNA transcription, antigen expression, progeny DNA replication, and viral susceptibilities tol(−)SddC, PCV, and other nucleoside analogs, it is concluded that the cell lines are able to stably producel(−)SddC- and PCV-sensitive and -resistant HBV virions. In addition, the relative susceptibilities of the wild-type and mutant HBV produced from the stably transfected cell lines to several anti-HBV nucleoside analogs were also examined and found to be about the same as those found by using a transient infection system. PMEA [9-(2-phosphonylmethoxytehyl)-adenine] and QYL685 are able to suppressl(−)SddC- and PCV-resistant HBV. In conclusion, this cell culture system is a novel and useful tool for evaluating anti-HBV compounds and biologics.
Molecular Mechanisms of Fluoroquinolone Resistance in
Pseudomonas aeruginosa
Isolates from Cystic Fibrosis Patients
Authors: Jalal Shah , Ciofu Oana , Høiby Niels , Gotoh Naomasa , Wretlind Bengt
Published: July 2002

Twenty
P. aeruginosa
isolates were collected from six cystic fibrosis (CF) patients, aged 27 to 33, in 1994 (9 isolates) and 1997 (11 isolates) at the CF Center, Copenhagen, Denmark, and were typed by pulse-field gel electrophoresis (PFGE) or ribotyping. Five of the patients had isolates with the same PFGE or ribotyping patterns in 1997 as in 1994, and ciprofloxacin had a two- to fourfold higher MIC for the isolates collected in 1997 than those from 1994. Genomic DNA was amplified for
gyrA
,
parC
,
mexR
, and
nfxB
by PCR and sequenced. Eleven isolates had mutations in
gyrA
, seven isolates had mutations at codon 83 (Thr to Ile), and four isolates had mutations at codon 87 (Asp to Asn or Tyr). Sixteen isolates had mutations in
nfxB
at codon 82 (Arg to Leu). Increased amounts of OprN were found in six isolates and OprJ in eight isolates as determined by immunoblotting. No isolates had mutations in
parC
or
mexR
. Six isolates had mutations in efflux pumps without
gyrA
mutations. The average number of mutations was higher in isolates from 1997 than in those from 1994. The results also suggested that efflux resistance mechanisms are more common in isolates from CF patients than in strains from urine and wounds from non-CF patients, in which mutations in
gyrA
and
parC
dominate (S. Jalal and B. Wretlind, Microb. Drug Resist. 4:257–261, 1998).
Antiviral Activity of 2′-Deoxy-3′-Oxa-4′-Thiocytidine (BCH-10652) against Lamivudine-Resistant Human Immunodeficiency Virus Type 1 in SCID-hu Thy/Liv Mice
Authors: Stoddart Cheryl A. , Moreno Mary E. , Linquist-Stepps Valerie D. , Bare Christopher , Bogan Mark R. , Gobbi Alberto , Buckheit Robert W. , Bedard Jean , Rando Robert F. , McCune Joseph M.
Published: July 2002

Oral administration of 2′-deoxy-3′-oxa-4′-thiocytidine (BCH-10652), a nucleoside analog structurally similar to lamivudine (3TC), caused dose-dependent inhibition of viral replication in SCID-hu Thy/Liv mice infected with human immunodeficiency virus type 1 NL4-3 and with an NL4-3 clone containing the M184V mutation in reverse transcriptase that confers resistance to 3TC. These experiments demonstrate the utility of this mouse model for evaluating drug resistance and for performing direct comparisons between antiviral compounds in vivo.
Identification of a Streptogramin A Acetyltransferase Gene in the Chromosome of
Yersinia enterocolitica
Authors: Seoane Asunción , García Lobo Juan M.
Published: July 2002

Streptogramins are polypeptide antibiotics inhibiting protein synthesis by the prokaryotic ribosome. Gram-positive organisms are susceptible to streptogramins, while most gram-negative bacteria are intrinsically resistant. We have found a genomic fragment from a
Yersinia enterocolitica
isolate with an open reading frame coding for a polypeptide similar to the virginiamycin acetyltransferases found in various plasmids from gram-positive bacteria. The susceptible
Escherichia coli
strain DB10 was transformed to resistance to the type A streptogramins and to mixed (A + B) streptogramins upon introduction of a plasmid containing that gene. In addition, we showed streptogramin acetylating activity in vitro dependent on the presence of the
Y. enterocolitica sat
gene. Southern blot hybridization experiments showed that the
sat
gene was present in all the
Y. enterocolitica
isolates examined. These data together show that the gene in the
Y. enterocolitica
chromosome encoded an active streptogramin acetyltransferase. The deduced sequence of the
Y. enterocolitica
Sat protein was close to those of
sat
gene products found in gram-positive bacteria and cyanobacteria, suggesting a common evolutionary origin.
Pharmacodynamics of Glycopeptides in the Mouse Peritonitis Model ofStreptococcus pneumoniaeorStaphylococcus aureusInfection
Authors: Knudsen Jenny Dahl , Fuursted Kurt , Raber Susan , Espersen Frank , Frimodt-Møller Niels
Published: July 2002

The emergence of resistance to various antibiotics in pneumococci leaves the glycopeptides as the only antibiotics against which pneumococci have no resistance mechanism. This situation has led to a renewed interest in the use of glycopeptides. It has not yet been possible to conclude which one or more of the pharmacokinetic or pharmacodynamic (PK/PD) parameters are the most important and best predictors for the effects of treatment with glycopeptides in animal models or in humans. We used the mouse peritonitis model with immunocompetent mice and withStaphylococcus aureusandStreptococcus pneumoniaeas infective organisms. A wide spectrum of different treatment regimens with vancomycin and teicoplanin was tested to study the pharmacodynamics of these drugs. In studies in which the single dose that protected 50% of lethally infected mice (ED50) was given as one dose or was divided into two doses, survival was significantly decreased when the dose was divided. The only statistically significant correlations between the percentage of survival of the mice after 6 days and each of the PK/PD parameters were for peak concentration (Cmax)/MIC andS. aureusand for the free fraction ofCmax(Cmax-free)/MIC andS. pneumoniae. ForS. pneumoniae, the ED50for different dosing regimens increased with the number of doses given; e.g., the single-dose ED50s for vancomycin and teicoplanin were 0.65 and 0.45 mg/kg, respectively, but the ED50s for dosing regimens with 2-h doses given for 48 h were 6.79 and 5.67 mg/kg, respectively. In experiments with 39 different vancomycin dosing regimens and 40 different teicoplanin dosing regimens againstS. pneumoniae, the different PK/PD parameters were analyzed using logistic regression. TheCmax-free/MIC was one of two parameters that best explained the effect for both drugs; for vancomycin, the other important parameter was the AUC/MIC, and for teicoplanin, the other parameter was the time the free fraction of the drug is above the MIC. The effect analyzed as a function ofCmax-free/MIC disclosed thresholds with shifts from almost no effect to full effect at ratios of five to six for vancomycin and two to three for teicoplanin.
Spectinomycin Resistance in
Neisseria
spp. Due to Mutations in 16S rRNA
Authors: Galimand Marc , Gerbaud Guy , Courvalin Patrice
Published: July 2002

Spectinomycin resistance in clinical isolates of
Neisseria meningitidis
and
Neisseria gonorrhoeae
was found to be due to mutations G1064C and C1192U (
Escherichia coli
numbering) in 16S rRNA genes, respectively.
Therapeutic Responses to Different Antimalarial Drugs in Vivax Malaria
Authors: Pukrittayakamee Sasithon , Chantra Arun , Simpson Julie A. , Vanijanonta Sirivan , Clemens Ralf , Looareesuwan Sornchai , White Nicholas J.
Published: July 2002

The therapeutic responses to the eight most widely used antimalarial drugs were assessed in 207 adult patients with
Plasmodium vivax
malaria. This parasite does not cause marked sequestration, so parasite clearance can be used as a direct measure of antimalarial activity. The activities of these drugs in descending order were artesunate, artemether, chloroquine, mefloquine, quinine, halofantrine, primaquine, and pyrimethamine-sulfadoxine (PS). Therapeutic responses to PS were poor; parasitemias did not clear in 5 of the 12 PS-treated patients, whereas all the other patients made an initial recovery. Of 166 patients monitored for ≥28 days, 35% had reappearance of vivax malaria 11 to 65 days later and 7% developed falciparum malaria 5 to 21 days after the start of treatment. There were no significant differences in the times taken for vivax malaria reappearance among the different groups except for those given mefloquine and chloroquine, in which all vivax malaria reappearances developed >28 days after treatment, suggesting suppression of the first relapse by these slowly eliminated drugs. There was no evidence of chloroquine resistance. The antimalarial drugs vary considerably in their intrinsic activities and stage specificities of action.
Antipneumococcal Activity of ABT-773 Compared to Those of 10 Other Agents
Authors: Davies Todd A. , Ednie Lois M. , Hoellman Dianne M. , Pankuch Glenn A. , Jacobs Michael R. , Appelbaum Peter C.
Published: July 2002

MICs, time-kills, and postantibiotic effects (PAEs) of ABT-773 (a new ketolide) and 10 other agents were determined against 226 pneumococci. Against 78
ermB
- and 44
mefE
-containing strains, ABT-773 MICs at which 50% of the isolates tested were inhibited (MIC
50
s) and MIC
90
s were 0.016 to 0.03 and 0.125 μg/ml, respectively. Clindamycin was active only against macrolide-resistant strains containing
mefE
(MIC
50
, 0.06 μg/ml; MIC
90
, 0.125 μg/ml). Activities of pristinamycin (MIC
90
, 0.5 μg/ml) and vancomycin (MIC
90
, 0.25 μg/ml) were unaffected by macrolide or penicillin resistance, while β-lactam MICs rose with those of penicillin G. Against 19 strains with L4 ribosomal protein mutations and two strains with mutations in domain V of 23S rRNA, ABT-773 MICs were 0.03 to 0.25 μg/ml, while macrolide and azalide MICs were all ≥16.0 μg/ml. ABT-773 was bactericidal at twice the MIC after 24 h for 8 of 12 strains (including three strains with erythromycin MICs greater than or equal to 64.0 μg/ml). Kill kinetics of erythromycin, azithromycin, clarithromycin, and roxithromycin against macrolide-susceptible strains were slower than those of ABT-773. ABT-773 had longer PAEs than macrolides, azithromycin, clindamycin, or β-lactams, including against
ermB
-containing strains. ABT-773, therefore, shows promising in vitro activity against macrolide-susceptible as well as -resistant pneumococci.
Prevalence and Characteristics of Multinucleoside-Resistant Human Immunodeficiency Virus Type 1 among European Patients Receiving Combinations of Nucleoside Analogues
Authors: Van Vaerenbergh Kristien , Van Laethem Kristel , Albert Jan , Boucher Charles A. B. , Clotet Bonaventura , Floridia Marco , Gerstoft Jan , Hejdeman Bo , Nielsen Claus , Pannecouque Christophe , Perrin Luc , Pirillo Maria F. , Ruiz Lidia , Schmit Jean-Claude , Schneider François , Schoolmeester Anne , Schuurman Rob , Stellbrink Hans J. , Stuyver Lieven , Van Lunzen Jan , Van Remoortel Barbara , Van Wijngaerden Eric , Vella Stefano , Witvrouw Myriam , Yerly Sabine , De Clercq Erik , Desmyter Jan , Vandamme Anne-Mieke
Published: July 2002

The prevalence and the genotypic and phenotypic characteristics of multinucleoside-resistant (MNR) human immunodeficiency virus type 1 (HIV-1) variants in Europe were investigated in a multicenter study that involved centers in nine European countries. Study samples (
n
= 363) collected between 1991 and 1997 from patients exposed to two or more nucleoside analogue reverse transcriptase inhibitors (NRTIs) and 274 control samples from patients exposed to no or one NRTI were screened for two marker mutations of multinucleoside resistance (the Q151M mutation and a mutation with a 2-amino-acid insertion at codon 69, T69S-XX). Q151M was identified in six of the study samples (1.6%), and T69S-XX was identified in two of the study samples (0.5%; both of them T69S-SS), but both patterns were absent among control samples. Non-NRTI (NNRTI)-related changes were observed in viral strains from two patients, which displayed the Q151M resistance pattern, although the patients were NNRTI naive. The patients whose isolates displayed multinucleoside resistance had received treatment with zidovudine and either didanosine, zalcitabine, or stavudine. Both resistance patterns conferred broad cross-resistance to NRTIs in vitro and a poor response to treatment in vivo. MNR HIV-1 is found only among multinucleoside-experienced patients. Its prevalence is low in Europe, but it should be closely monitored since it seriously limits treatment options.
Therapeutic Efficacy of Liposomal Rifabutin in a
Mycobacterium avium
Model of Infection
Authors: Gaspar Maria Manuela , Neves Susana , Portaels Françoise , Pedrosa Jorge , Silva Manuel T. , Cruz Maria Eugénia M.
Published: July 2002

Liposomal formulations of rifabutin were developed, and the effects of some parameters on the incorporation efficiency were studied. The antimycobacterial activity of rifabutin incorporated into liposomes prepared with phosphatidylcholine and phosphatidylserine (molar ratio, 7:3) was evaluated in a murine model of infection with a virulent
Mycobacterium avium
strain (strain P1581) and was compared with that of free rifabutin. The influences of the size of the liposomal rifabutin formulation, the administered doses, and the treatment schedules on the evolution of infection were studied. Two types of treatment schedules were assayed: therapeutic and prophylactic. The therapeutic treatment started 2 weeks after infection, while the prophylactic treatment began 1 day before the experimental infection with mycobacteria. Incorporation of rifabutin in liposomes resulted in a significant enhancement of activity against
M. avium
infection compared to that of rifabutin in the free form in both schedules. These results demonstrate that liposomal formulations of antibiotics such as rifabutin may be effective for the treatment or prophylaxis of infectious diseases.
Bactericidal Activity of Micromolar
N
-Chlorotaurine: Evidence for Its Antimicrobial Function in the Human Defense System
Authors: Nagl Markus , Hess Michael W. , Pfaller Kristian , Hengster Paul , Gottardi Waldemar
Published: July 2002

N
-Chlorotaurine, the main representative of long-lived oxidants found in the supernatant of stimulated granulocytes, has been investigated systematically with regard to its antibacterial activity at different physiological concentrations for the first time.
N
-Chlorotaurine (12.5 to 50 μM) demonstrated a bactericidal effect i.e., a 2 to 4 log
10
reduction in viable counts, after incubation at 37°C for 6 to 9 h at pH 7.0, which effect was significantly enhanced in an acidic milieu (at pH 5.0), with a 3 to 4 log
10
reduction after 2 to 3 h. Moreover, bacteria were attenuated after being incubated in
N
-chlorotaurine for a sublethal time, as demonstrated with the mouse peritonitis model. The supernatant of stimulated granulocytes exhibited similar activity. Transmission electron microscopy revealed changes in the bacterial cell membrane and cytoplasmic disintegration with both reacting systems, even in the case of a mere attenuation. The results of this study suggest a significant bactericidal function of
N
-chlorotaurine and other chloramines during inflammation.
Comparative In Vitro Activities of ABT-773 against Aerobic and Anaerobic Pathogens Isolated from Skin and Soft-Tissue Animal and Human Bite Wound Infections
Authors: Goldstein Ellie J. C. , Citron Diane M. , Merriam C. Vreni , Warren Yumi , Tyrrell Kerin
Published: July 2002

We studied the comparative in vitro activities of ABT-773, a new ketolide, against 268 aerobic and 148 anaerobic recent isolates from clinical bites using an agar dilution method and inocula of 10
4
CFU/spot for aerobes and 10
5
CFU for anaerobes. The following are the MIC ranges and MICs at which 90% of isolates are inhibited (MIC
90
s) of ABT-773 for various isolates, respectively:
Pasteurella multocida
and
Pasteurella septica
, 0.125 to 2 and 1 μg/ml; other
Pasteurella
species, 0.125 to 1 and 0.5 μg/ml;
Corynebacterium
spp., 0.015 to 0.06 and 0.015 μg/ml;
Staphylococcus aureus
, 0.03 to 0.06 and 0.06 μg/ml; coagulase-negative staphylococci, 0.015 to >32 and 32 μg/ml; streptococci, 0.015 to 0.03 and 0.03 μg/ml;
Eikenella corrodens
, 0.25 to 1 and 1 μg/ml; and
Bergeyella zoohelcum
, 0.03 to 0.25 and 0.06 μg/ml. For anaerobes the MIC ranges and MIC
90
s of ABT-773 were as follows, respectively:
Prevotella heparinolytica
, 0.06 to 0.125 and 0.125 μg/ml;
Prevotella
spp., 0.015 to 0.125 and 0.06 μg/ml;
Porphyromonas
spp., 0.015 to 0.03 and 0.015 μg/ml;
Fusobacterium nucleatum
, 0.5 to 8 and 8 μg/ml; other
Fusobacterium
spp., 0.015 to 8 and 0.5 μg/ml;
Bacteroides tectum
, 0.015 to 0.5 and 0.06 μg/ml; and
Peptostreptococcus
spp., 0.015 to 0.25 and 0.03 μg/ml. ABT-773 was more active than all macrolides tested against
S. aureus
,
E. corrodens
, and anaerobes, but all compounds were poorly active against
F. nucleatum
. The activity of ABT-773 was within 1 dilution of that of azithromycin against
Pasteurella
spp., and ABT-773 was four- to eightfold more active than clarithromycin against
Pasteurella
spp. ABT-773 may offer a therapeutic alternative for bite wound infections.
Pharmacokinetics of Oral Acyclovir in Neonates and in Infants: a Population Analysis
Authors: Tod M. , Lokiec F. , Bidault R. , De Bony F. , Petitjean O. , Aujard Y. ,   the Acyclovir Pediatric French Group
Published: July 2002

Acyclovir is approved for the treatment of herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections in children by the intravenous and oral routes. However, its use by the oral route in children younger than 2 years of age is limited due to a lack of pharmacokinetic data. The objectives of the present study were to determine the typical pharmacokinetics of an oral suspension of acyclovir given to children younger than 2 years of age and the interindividual variabilities in the values of the pharmacokinetic parameters in order to support the proposed dosing regimen (24 mg/kg of body weight three times a day for patients younger than 1 month of age or four times a day otherwise). Children younger than age 2 years with HSV or VZV infections were enrolled in a multicenter study. Children were treated for at least 5 days with an acyclovir oral suspension. Plasma samples were obtained at steady state, before acyclovir administration, and at 2, 3, 5, and 8 h after acyclovir administration. Acyclovir concentrations were measured by radioimmunoassay. The data were analyzed by a population approach. Data for 79 children were considered in the pharmacokinetic study (212 samples, 1 to 5 samples per patient). Acyclovir clearance was related to the estimated glomerular filtration rate, body surface area, and serum creatinine level. The volume of distribution was related to body weight. The elimination half-life decreased sharply during the first month after birth, from 10 to 15 h to 2.5 h. Bioavailability was 0.12. The interindividual variability was less pronounced when the parameters were normalized with respect to body weight. Hence, dosage adjustment by body weight is recommended for this population. Simulations showed that the length of time that acyclovir remains above the 50% inhibitory concentration during a 24-h period was more than 12 h for HSV but not for VZV. The proposed dosing regimen seems adequate for the treatment of HSV infections, while for the treatment of VZV infections, a twofold increase in the dose seems necessary for children older than age 3 months.
Pharmacodynamics of Telithromycin In Vitro against Respiratory Tract Pathogens
Authors: Odenholt Inga , Löwdin Elisabeth , Cars Otto
Published: July 2002

Telithromycin (HMR 3647) is a new ketolide that belongs to a new class of semisynthetic 14-membered-ring macrolides which have expanded activity against multidrug-resistant gram-positive bacteria. The aim of the present study was to investigate different basic pharmacodynamic properties of this new compound. The following studies of telithromycin were performed: (i) studies of the rate and extent of killing of respiratory tract pathogens with different susceptibilities to erythromycin and penicillin exposed to a fixed concentration that corresponds to a dose of 800 mg in humans, (ii) studies of the rate and extent of killing of telithromycin at five different concentrations, (iii) studies of the rate and extent of killing of the same pathogens at three different inocula, (iv) studies of the postantibiotic effect and the postantibiotic sub-MIC effect of telithromycin, and (v) determination of the rate and extent of killing of telithromycin in an in vitro kinetic model. In conclusion, telithromycin exerted an extremely fast killing of all strains of
Streptococcus pneumoniae
both with static concentrations and in the in vitro kinetic model. A slower killing of the strains of
Streptococcus pyogenes
was noted, with regrowth in the kinetic model of a macrolide-lincosamide-streptogramin B-inducible strain. The strains of
Haemophilus influenzae
were not killed at all at a concentration of 0.6 mg/liter due to high MICs. A time-dependent killing was seen for all strains. No inoculum effect was seen for the strains of
S. pneumoniae
, with a 99.9% reduction in the numbers of CFU for all inocula at both 8 h and 24 h. The killing of the strains of
S. pyogenes
was reduced by 1 log
10
CFU at 8 h and 2 to 3 log
10
CFU at 24 h when the two lower inocula were used but not at all at 8 and 24 h when the highest inoculum was used. For both of the
H. influenzae
strains there was an inoculum effect, with 1 to 2 log
10
CFU less killing for the inoculum of 10
8
CFU/ml in comparison to that for the inoculum of 10
6
CFU/ml. Overall, telithromycin exhibited long postantibiotic effects and postantibiotic sub-MIC effects for all strains investigated.
Comparative In Vitro Activities of ABT-773 against 362 Clinical Isolates of Anaerobic Bacteria
Authors: Citron Diane M. , Appleman Maria D.
Published: July 2002

The activity of ABT-773, a novel ketolide antibiotic, against clinical isolates of anaerobic bacteria was determined and compared to the activities of other antimicrobial agents. MICs at which 90% of isolates were inhibited (MIC
90
s) were ≤0.06 μg/ml for
Actinomyces
spp.,
Clostridium perfringens
,
Peptostreptococcus
spp.,
Propionibacterium
spp., and
Porphyromonas
spp. The MIC
50
s and MIC
90
s were ≤0.06 and >32 μg/ml, respectively, for
Eubacterium
spp.,
Lactobacillus
spp.,
Clostridium difficile
, and
Clostridium ramosum.
The MIC
90
for
Bilophila wadsworthia
,
Bacteroides ureolyticus,
and
Campylobacter gracilis
was 1 μg/ml, and that for
Prevotella bivia
and other
Prevotella
spp. was 0.5 μg/ml. The MIC
90
for
Fusobacterium nucleatum
was 8 μg/ml, and that for
Fusobacterium mortiferum
and
Fusobacterium varium
was >32 μg/ml
.
The MIC
90
s for the
Bacteroides fragilis
group were as follows: for
B. fragilis
, 8 μg/ml; for
Bacteroides thetaiotaomicron
,
Bacteroides ovatus
,
Bacteroides distasonis
, and
Bacteroides uniformis
, >32 μg/ml; and for
Bacteroides vulgatus
, 4 μg/ml. Telithromycin MICs for the
B. fragilis
group were usually 1 to 2 dilutions higher than ABT-773 MICs. For all strains, ABT-773 was more active than erythromycin by 4 or more dilutions, and for some strains this drug was more active than clindamycin.
Pharmacokinetic Profiles of Nevirapine and Indinavir in Various Fractions of Seminal Plasma
Authors: van Praag Rieneke M. E. , Repping Sjoerd , de Vries Jan W. A. , Lange Joep M. A. , Hoetelmans Richard M. W. , Prins Jan M.
Published: July 2002

Limited data are available on antiretroviral drug concentrations in seminal plasma during a dosing interval. Further, since human ejaculate is composed of fluids originating from the testes, the seminal vesicles, and the prostate, all having different physiological characteristics, drug concentrations in total seminal plasma do not necessarily reflect concentrations in the separate compartments. Five human immunodeficiency virus type 1-infected patients on nevirapine (NVP; 200 mg twice a day [b.i.d.]) and/or indinavir (IDV; 800 mg b.i.d. with ritonavir, 100 mg b.i.d.) regimens used a split ejaculate technique to separate seminal plasma in two fractions, representing fluids from the testes and prostate (first fraction) and fluids from the seminal vesicles (second fraction). Split-ejaculate samples were provided at 0, 2, 5, and 8 h after drug ingestion, on separate days after 3 days of sexual abstinence. NVP and IDV showed time-dependent concentrations in seminal plasma, with peak concentrations in both fractions at 2 and 2 to 5 h, respectively, after drug ingestion. The NVP concentrations were not significantly different between the first and second fractions of the ejaculate at all time points measured and were in the therapeutic range, except for the predose concentration in two patients. The median (range) predose IDV concentrations in the first and second fractions of the ejaculate were 448 (353 to 1,015) ng/ml and 527 (240 to 849) ng/ml, respectively (P= 0.7). In conclusion, NVP and IDV concentrations in seminal plasma are dependent on the time after drug ingestion. Furthermore, our data suggest that NVP and IDV achieve therapeutic concentrations in both the testes and prostate and the seminal vesicles throughout the dosing interval.
Therapeutic Efficacy of Liposome-Encapsulated Gentamicin in Rat
Klebsiella pneumoniae
Pneumonia in Relation to Impaired Host Defense and Low Bacterial Susceptibility to Gentamicin
Authors: Schiffelers Raymond M. , Storm Gert , ten Kate Marian T. , Bakker-Woudenberg Irma A. J. M.
Published: July 2002

Long-circulating liposomes (LCL) may be used as targeted antimicrobial drug carriers as they localize at sites of infection. As a result, LCL-encapsulated gentamicin (LE-GEN) has demonstrated superior antibacterial activity over the free drug in a single-dose study of immunocompetent rats with
Klebsiella pneumoniae
pneumonia. In the present study, the therapeutic efficacy of LE-GEN was evaluated by monitoring rat survival and bacterial counts in blood and lung tissue in clinically relevant models, addressing the issue of impaired host defense and low bacterial antibiotic susceptibility. The results show that in immunocompetent rats infected with the high-GEN-susceptibility
K. pneumoniae
strain, a single dose of LE-GEN is clearly superior to an equivalent dose of free GEN. Yet complete survival can also be obtained with multiple doses of free GEN. In leukopenic rats infected with the high-GEN-susceptible
K. pneumoniae
strain, free GEN at the maximum tolerated dose (MTD) was needed to obtain survival. However, with the addition of a single dose of LE-GEN to free-GEN treatment, complete survival can be obtained using a sevenfold-lower cumulative amount of GEN than with free-GEN treatment alone. In leukopenic rats infected with low-GEN-susceptible
K. pneumoniae
cells, free GEN at the MTD did not result in survival. The use of LE-GEN is needed for therapeutic success. Increasing LE-GEN bilayer fluidity resulted in an increased GEN release from the liposomes and hence improved rat survival, thus showing the importance of the liposome lipid composition for therapeutic efficacy. These results warrant further clinical studies of liposomal formulations of aminoglycosides in immunocompromised patients with severe infections.
Antimicrobial Properties and Mode of Action of the Pyrrothine Holomycin
Authors: Oliva Brunello , O'Neill Alexander , Wilson Jenny M. , O'Hanlon Peter J. , Chopra Ian
Published: July 2002

Holomycin, a member of the pyrrothine class of antibiotics, displayed broad-spectrum antibacterial activity, inhibiting a variety of gram-positive and gram-negative bacteria, with the exception of
Enterobacter cloacae, Morganella morganii
, and
Pseudomonas aeruginosa
. The antibiotic lacked activity against the eukaryotic microorganisms
Saccharomyces cerevisiae
and
Candida kefyr
. Holomycin exhibited a bacteriostatic response against
Escherichia coli
that was associated with rapid inhibition of RNA synthesis in whole cells. Inhibition of RNA synthesis could have been a secondary consequence of inhibiting tRNA aminoacylation, thereby inducing the stringent response. However, the levels of inhibition of RNA synthesis by holomycin were similar in a stringent and relaxed pair of
E. coli
strains that were isogenic except for the deletion of the
relA
gene. This suggests that inhibition of RNA synthesis by holomycin could reflect direct inhibition of DNA-dependent RNA polymerase. Examination of the effects of holomycin on the kinetics of the appearance of β-galactosidase in induced
E. coli
cells was also consistent with inhibition of RNA polymerase at the level of RNA chain elongation. However, holomycin only weakly inhibited
E. coli
RNA polymerase in assays using synthetic poly(dA-dT) and plasmid templates. Furthermore, inhibition of RNA polymerase was observed only at holomycin concentrations in excess of those required to inhibit the growth of
E. coli
. It is possible that holomycin is a prodrug, requiring conversion in the cell to an active species that inhibits RNA polymerase.
In Vitro Activities of the New Ketolide HMR 3647 (Telithromycin) in Comparison with Those of Eight Other Antibiotics against Viridans Group Streptococci Isolated from Blood of Neutropenic Patients with Cancer
Authors: Alcaide Fernando , Benı́tez Miguel Angel , Carratalà Jordi , Gudiol Francesc , Liñares Josefina , Martı́n Rogelio
Published: July 2002

The in vitro activities of the ketolide telithromycin and eight other antibiotics were tested against 77 strains of viridans group streptococci isolated from blood samples of neutropenic patients. Thirty-one (40.3%) of the strains were resistant to penicillin G, and 27 (35.1%) were resistant to erythromycin A. Telithromycin (MIC range of ≤0.03 to 1 μg/ml) was the most active antimicrobial tested. These data suggest that telithromycin could be useful for treatment of viridans group streptococcal bacteremia in neutropenic patients with cancer.
Phenotypic Resistance of
Staphylococcus aureus
, Selected
Enterobacteriaceae
, and
Pseudomonas aeruginosa
after Single and Multiple In Vitro Exposures to Ciprofloxacin, Levofloxacin, and Trovafloxacin
Authors: Gilbert D. N. , Kohlhepp S. J. , Slama K. A. , Grunkemeier G. , Lewis G. , Dworkin R. J. , Slaughter S. E. , Leggett J. E.
Published: July 2002

The phenotypic resistance of selected organisms to ciprofloxacin, levofloxacin, and trovafloxacin was defined as a MIC of ≥4 μg/ml. The dynamics of resistance were studied after single and sequential drug exposures: clinical isolates of methicillin-susceptible and methicillin-resistant
Staphylococcus aureus
(MSSA and MRSA),
Escherichia coli
,
Klebsiella pneumoniae
,
Enterobacter cloacae
,
Serratia marcescens
, and
Pseudomonas aeruginosa
were utilized. After a single 48-h exposure of a large inoculum to four times the initial MIC for the organism, the frequency of selection of resistant mutants of MSSA was greater for trovafloxacin than levofloxacin (
P
= 0.008); for
E. cloacae
, the frequency was highest for ciprofloxacin and lowest for levofloxacin and trovafloxacin; for
S. marcescens
, the frequency was highest for trovafloxacin and lowest for ciprofloxacin (
P
= 0.003). The results of serial passage experiments were analyzed both by the Kaplan-Meier product-limited method as well as by analysis of variance of mean inhibitory values. By both methods, MSSA and MRSA expressed mutants resistant to ciprofloxacin after fewer passages than were required for either levofloxacin or trovafloxacin. For the aerobic gram-negative bacilli, two general patterns emerged. Mutants resistant to trovafloxacin appeared sooner and reached higher mean MICs than did mutants resistant to levofloxacin or ciprofloxacin. Mutants resistant to ciprofloxacin appeared later and reached mean MICs lower than the MICs of the other two drugs studied. Even though individual strain variation occurred, the mean MICs were reproduced when the serial passage experiment was repeated using an identical panel of
E. coli
isolates. In summary, the dynamic selection of fluoroquinolone-resistant bacteria can be demonstrated in experiments that employ serial passage of bacteria in vitro.
Katanosin B and Plusbacin A
3
, Inhibitors of Peptidoglycan Synthesis in Methicillin-Resistant
Staphylococcus aureus
Authors: Maki Hideki , Miura Kenji , Yamano Yoshinori
Published: July 2002

Both katanosin B and plusbacin A
3
are naturally occurring cyclic depsipeptide antibiotics containing a lactone linkage. They showed strong antibacterial activity against methicillin-resistant
Staphylococcus aureus
and VanA-type vancomycin-resistant enterococci, with MICs ranging from 0.39 to 3.13 μg/ml, as well as against other gram-positive bacteria. They inhibited the incorporation of
N
-acetylglucosamine, a precursor of cell wall synthesis, into peptidoglycan of
S. aureus
whole cells at concentrations close to their MICs. In vitro studies with a wall-membrane particulate fraction of
S. aureus
showed that katanosin B and plusbacin A
3
inhibited the formation of lipid intermediates, with 50% inhibitory concentrations (IC
50
s) of 2.2 and 2.3 μg/ml, respectively, and inhibited the formation of nascent peptidoglycan, with IC
50
s of 0.8 and 0.4 μg/ml, respectively. Vancomycin, a well-known inhibitor of transglycosylation, did not inhibit the formation of lipid intermediates but did inhibit the formation of nascent peptidoglycan, with an IC
50
of 4.1 μg/ml. Acetyl-Lys-
d
-Ala-
d
-Ala, an analog of the terminus of the lipid intermediates, effectively suppressed the inhibition of transglycosylation by vancomycin, but did not suppress those by katanosin B and plusbacin A
3
. These results indicate that the antibacterial activity of katanosin B and plusbacin A
3
is due to blocking of transglycosylation and its foregoing steps of cell wall peptidoglycan synthesis via a mechanism differing from that of vancomycin.
Activities of Hexadecylphosphocholine (Miltefosine), AmBisome, and Sodium Stibogluconate (Pentostam) against
Leishmania donovani
in Immunodeficient
scid
Mice
Authors: Escobar Patricia , Yardley Vanessa , Croft Simon L.
Published: July 2002

In both
scid
and BALB/c mouse-
Leishmania donovani
models, hexadecyphosphocholine (miltefosine) and AmBisome had similar levels of activity. In contrast, sodium stibogluconate (Pentostam) was significantly less active against
L. donovani
in
scid
mice than in BALB/c mice. The in vitro anti-leishmanial activity of miltefosine was similar in peritoneal macrophages derived from both
scid
and BALB/c mice, whereas Pentostam and AmBisome were significantly more active in the latter.
Comparative In Vitro Activity of ABT-773, a Novel Antibacterial Ketolide
Authors: Nilius A. M. , Bui M. H. , Almer L. , Hensey-Rudloff D. , Beyer J. , Ma Z. , Or Y. S. , Flamm R. K.
Published: July 2002

The in vitro activities of ABT-773, erythromycin, clarithromycin, and azithromycin were compared. ABT-773 was the most active compound against macrolide-susceptible
Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Staphylococcus epidermidis, Listeria monocytogenes
, and
Enterococcus
spp. and multidrug-resistant
Streptococcus pneumoniae
. It also had good activity against gram-negative and atypical respiratory tract pathogens and
Helicobacter pylori.
Identification of a Plasmid Encoding SHV-12, TEM-1, and a Variant of IMP-2 Metallo-β-Lactamase, IMP-8, from a Clinical Isolate of
Klebsiella pneumoniae
Authors: Yan Jing-Jou , Ko Wen-Chien , Wu Jiunn-Jong
Published: July 2002

A multidrug-resistant plasmid encoding TEM-1, SHV-12, and a variant of IMP-2 metallo-β-lactamase, designated IMP-8, was identified from a clinical isolate of
Klebsiella pneumoniae
. There are four nucleotide differences between
bla
IMP-2
and
bla
IMP-8
, resulting in two amino acid differences.
bla
IMP-8
was also found to be carried by an integron-borne gene cassette similar to the
bla
IMP-2
cassette.
Influence of Liposomal Amphotericin B on CD8 T-Cell Function
Authors: Kretschmar Marianne , Geginat Gernot , Bertsch Thomas , Walter Simon , Hof Herbert , Nichterlein Thomas
Published: July 2002

Liposomal amphotericin B was immunosuppressive on target cell lysis in vitro and on protection mediated by cytotoxic CD8 T cells in murine listeriosis. When dosages usually used for therapy in humans were compared, the immunosuppressive effect of 5 mg of liposomal amphotericin B/kg of body weight/day was similar to that of standard amphotericin B at 1 mg/kg/day, but a dosage of liposomal amphotericin B of 1 mg/kg/day was not suppressive in vivo.
Cell-Based Fluorescence Assay for Human Immunodeficiency Virus Type 1 Protease Activity
Authors: Lindsten Kristina , Uhlı́ková Tat'ána , Konvalinka Jan , Masucci Maria G. , Dantuma Nico P.
Published: July 2002

The human immunodeficiency virus type 1 (HIV-1) protease is essential for production of infectious virus and is therefore a major target for the development of drugs against AIDS. Cellular proteins are also cleaved by the protease, which explains its cytotoxic activity and the consequent failure to establish convenient cell-based protease assays. We have exploited this toxicity to develop a new protease assay that relies on transient expression of an artificial protease precursor harboring the green fluorescent protein (GFP-PR). The precursor is activated in vivo by autocatalytic cleavage, resulting in rapid elimination of protease-expressing cells. Treatment with therapeutic doses of HIV-1 protease inhibitors results in a dose-dependent accumulation of the fluorescent precursor that can be easily detected and quantified by flow cytometric and fluorimetric assays. The precursor provides a convenient and noninfectious model for high-throughput screenings of substances that can interfere with the activity of the protease in living cells.