bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro
and
In Vivo
Activity of Solithromycin (CEM-101) against Plasmodium Species
Authors: Wittlin Sergio , Ekland Eric , Craft J Carl , Lotharius Julie , Bathurst Ian , Fidock David A. , Fernandes Prabhavathi 
Published: November 2011

ABSTRACT

With the emergence of
Plasmodium falciparum
infections exhibiting increased parasite clearance times in response to treatment with artemisinin-based combination therapies, the need for new therapeutic agents is urgent. Solithromycin, a potent new fluoroketolide currently in development, has been shown to be an effective, broad-spectrum antimicrobial agent. Malarial parasites possess an unusual organelle, termed the apicoplast, which carries a cryptic genome of prokaryotic origin that encodes its own translation and transcription machinery. Given the similarity of apicoplast and bacterial ribosomes, we have examined solithromycin for antimalarial activity. Other antibiotics known to target the apicoplast, such as the macrolide azithromycin, demonstrate a delayed-death effect, whereby treated asexual blood-stage parasites die in the second generation of drug exposure. Solithromycin demonstrated potent
in vitro
activity against the NF54 strain of
P. falciparum
, as well as against two multidrug-resistant strains, Dd2 and 7G8. The dramatic increase in potency observed after two generations of exposure suggests that it targets the apicoplast. Solithromycin also retained potency against azithromycin-resistant parasites derived from Dd2 and 7G8, although these lines did demonstrate a degree of cross-resistance. In an
in vivo
model of
P. berghei
infection in mice, solithromycin demonstrated a 100% cure rate when administered as a dosage regimen of four doses of 100 mg/kg of body weight, the same dose required for artesunate or chloroquine to achieve 100% cure rates in this rodent malaria model. These promising
in vitro
and
in vivo
data support further investigations into the development of solithromycin as an antimalarial agent.
Characterization of CIA-1, an Ambler Class A Extended-Spectrum β-Lactamase from Chryseobacterium indologenes
Authors: Matsumoto Takehisa , Nagata Mika , Ishimine Nau , Kawasaki Kenji , Yamauchi Kazuyoshi , Hidaka Eiko , Kasuga Eriko , Horiuchi Kazuki , Oana Kozue , Kawakami Yoshiyuki , Honda Takayuki 
Published: November 2011

ABSTRACT

An Ambler class A β-lactamase gene,
bla
CIA-1
, was cloned from the reference strain
Chryseobacterium indologenes
ATCC 29897 and expressed in
Escherichia coli
BL21. The
bla
CIA-1
gene encodes a novel extended-spectrum β-lactamase (ESBL) that shared 68% and 60% identities with the CGA-1 and CME-1 β-lactamases, respectively.
bla
CIA-1
-like genes were detected from clinical isolates. In addition to the metallo-β-lactamase IND of Ambler class B,
C. indologenes
has a class A ESBL gene,
bla
CIA-1
, located on the chromosome.
Genetic Features of the Widespread Plasmid Coding for the Carbapenemase OXA-48
Authors: Poirel Laurent , Bonnin Rémy A. , Nordmann Patrice 
Published: November 2011

ABSTRACT

Complete sequencing of plasmid pOXA-48a carrying the
bla
OXA-48
gene from a
Klebsiella pneumoniae
isolate was performed. Its backbone corresponded to that of an IncL/M-type plasmid, in which the
bla
OXA-48
gene had been integrated through the acquisition of the Tn
1999
composite transposon without any other antibiotic resistance gene. Molecular epidemiology using a collection of international OXA-48 producers revealed the wide diffusion of pOXA-48a or closely related plasmids.
Inactivation of the Lipopeptide Antibiotic Daptomycin by Hydrolytic Mechanisms
Authors: D'Costa Vanessa M. , Mukhtar Tariq A. , Patel Tejal , Koteva Kalinka , Waglechner Nicholas , Hughes Donald W. , Wright Gerard D. , De Pascale Gianfranco 
Published: November 2011

ABSTRACT

The lipopeptide daptomycin is a member of the newest FDA-approved antimicrobial class, exhibiting potency against a broad range of Gram-positive pathogens with only rare incidences of clinical resistance. Environmental bacteria harbor an abundance of resistance determinants orthologous to those in pathogens and thus may serve as an early-warning system for future clinical emergence. A collection of morphologically diverse environmental actinomycetes demonstrating unprecedented frequencies of daptomycin resistance and high levels of resistance by antibiotic inactivation was characterized to elucidate modes of drug inactivation.
In vivo
studies revealed that hydrolysis plays a key role, resulting in one or both of the following structural modifications: ring hydrolysis resulting in linearization (in 44% of inactivating isolates) or deacylation of the lipid tail (29%). Characterization of the mechanism in actinomycete WAC4713 (a
Streptomyces
sp. with an MIC of 512 μg/ml) demonstrated a constitutive resistance phenotype and established daptomycin's circularizing ester linkage to be the site of hydrolysis. Characterization of the hydrolase responsible revealed it to be likely a serine protease. These studies suggested that daptomycin is susceptible to general proteolytic hydrolysis, which was further supported by studies using proteases of diverse origin. These findings represent the first comprehensive characterization of daptomycin inactivation in any bacterial class and may not only presage a future mechanism of clinical resistance but also suggest strategies for the development of new lipopeptides.
Blood, Tissue, and Intracellular Concentrations of Erythromycin and Its Metabolite Anhydroerythromycin during and after Therapy
Authors: Krasniqi S. , Matzneller P. , Kinzig M. , Sörgel F. , Hüttner S. , Lackner E. , Müller M. , Zeitlinger M. 
Published: November 2011

ABSTRACTFor macrolides, clinical activity but also the development of bacterial resistance has been attributed to prolonged therapeutic and subtherapeutic concentrations. Although erythromycin is a long-established antimicrobial, concomitant determination of the pharmacokinetics of erythromycin and its metabolites in different compartments is limited. To better characterize the pharmacokinetics of erythromycin and its anhydrometabolite (anhydroerythromycin [AHE]) in different compartments during and after the end of treatment with 500 mg of erythromycin four times daily, concentration-time profiles were determined in plasma, interstitial space of muscle and subcutaneous adipose tissue, and white blood cells (WBCs) at days 1 and 3 of treatment and 2 and 7 days after end of therapy. In WBCs, concentrations of erythromycin exceeded those in plasma approximately 40-fold, while free concentrations in plasma and tissue were comparable. The observed delay of peak concentrations in tissue might be caused by fast initial cellular uptake. Two days after the end of treatment, subinhibitory concentrations were observed in plasma and interstitial space of both soft tissues, while 7 days after the end of treatment, erythromycin was not detectable in any compartment. This relatively short period of subinhibitory concentrations may be advantageous compared to other macrolides. The ratio of erythromycin over AHE on day 1 was highest in plasma (2.81 ± 3.45) and lowest in WBCs (0.27 ± 0.22). While the ratio remained constant between single dose and steady state, after the end of treatment the concentration of AHE declined more slowly than that of the parent compound, indicating the importance of the metabolite for the prolonged drug interaction of erythromycin.
Penetration of Doripenem into Skeletal Muscle and Subcutaneous Adipose Tissue in Healthy Volunteers
Authors: Burian Bernhard , Zeitlinger Markus , Donath Oliver , Reznicek Gottfried , Sauermann Robert 
Published: November 2011

ABSTRACT

Sufficient antibiotic concentrations at the infection site are a prerequisite for good bacterial killing. This study was performed to determine pharmacokinetics of doripenem in soft tissues and saliva. Six healthy male volunteers received a single intravenous infusion of 500 mg doripenem over 1 h. The concentrations of doripenem were measured over 8 h in saliva, plasma, and extracellular space fluid of skeletal muscle and subcutaneous adipose tissue employing
in vivo
microdialysis. Unbound drug concentrations were determined using ultra-high-performance liquid chromatography-tandem mass spectrometry. Maximum concentrations of doripenem were 15.3 ± 6.0 mg/liter in plasma, 9.9 ± 2.3 mg/liter in subcutaneous adipose tissue, 6.6 ± 2.9 mg/liter in skeletal muscle, and 0.5 ± 0.2 mg/liter in saliva. Areas under the concentration-time curve (AUC) from 0 to infinity were 26.3 ± 10.1, 20.4 ± 3.8, 12.8 ± 3.0, and 1.0 ± 0.5 mg · h/liter in plasma, adipose tissue, skeletal muscle, and saliva, respectively. Ratios of AUC in adipose tissue, skeletal muscle, and saliva to those in plasma were 0.84 ± 0.28, 0.53 ± 0.19, and 0.04 ± 0.03, respectively. In all six volunteers, a threshold of ≥40% for “time above MIC,” an index indicative of good antimicrobial activity, was exceeded in adipose tissue for MICs of ≤2 mg/liter and in skeletal muscle for MICs ≤1.5 mg/liter. Doripenem penetrates well into interstitial space fluid of skeletal muscle and adipose tissue, suggesting good antimicrobial activity in infected soft tissues, whereas it is detectable in relatively low concentrations in saliva.
Phenotypic and Genotypic Analysis of
In Vitro
-Selected Artemisinin-Resistant Progeny of Plasmodium falciparum
Authors: Tucker Matthew S. , Mutka Tina , Sparks Kansas , Patel Janus , Kyle Dennis E. 
Published: November 2011

ABSTRACT

Emergence of artemisinin resistance in Cambodia highlights the importance of characterizing resistance to this class of drugs. Previously, intermediate levels of resistance in
Plasmodium falciparum
were generated
in vitro
for artelinic acid (AL) and artemisinin (QHS). Here we expanded on earlier selection efforts to produce levels of clinically relevant concentrations, and the resulting lines were characterized genotypically and phenotypically. Recrudescence assays determined the ability of resistant and parent lines to recover following exposure to clinically relevant levels of drugs. Interestingly, the parent clone (D6) tolerated up to 1,500 ng/ml QHS, but the resistant parasite, D6.QHS340×3, recovered following exposure to 2,400 ng/ml QHS. Resistant D6, W2, and TM91c235 parasites all exhibited elevated 50% inhibitory concentrations (IC
50
s) to multiple artemisinin drugs, with >3-fold resistance to QHS and AL; however, the degree of resistance obtained with standard methods was remarkably less than expected for parasite lines that recovered from 2,400-ng/ml drug pressure. A novel assay format with radiolabeled hypoxanthine demonstrated a greater degree of resistance
in vitro
than the standard SYBR green method. Analysis of merozoite number in resistant parasites found D6 and TM91c235 resistant progeny had significantly fewer merozoites than parent strains, whereas W2 resistant progeny had significantly more. Amplification of
pfmdr1
increased proportionately to the increased drug levels tolerated by W2 and TM91c235, but not in resistant D6. In summary, we define the artemisinin resistance phenotype as a decrease in susceptibility to artemisinins along with the ability to recover from drug-induced dormancy following supraclinical concentrations of the drug.
Interplay between Single Resistance-Associated Mutations in the HIV-1 Protease and Viral Infectivity, Protease Activity, and Inhibitor Sensitivity
Authors: Henderson Gavin J. , Lee Sook-Kyung , Irlbeck David M. , Harris Janera , Kline Melissa , Pollom Elizabeth , Parkin Neil , Swanstrom Ronald 
Published: November 2011

ABSTRACT
Resistance-associated mutations in the HIV-1 protease modify viral fitness through changes in the catalytic activity and altered binding affinity for substrates and inhibitors. In this report, we examine the effects of 31 mutations at 26 amino acid positions in protease to determine their impact on infectivity and protease inhibitor sensitivity. We found that primary resistance mutations individually decrease fitness and generally increase sensitivity to protease inhibitors, indicating that reduced virion-associated protease activity reduces virion infectivity and the reduced level of per virion protease activity is then more easily titrated by a protease inhibitor. Conversely, mutations at more variable positions (compensatory mutations) confer low-level decreases in sensitivity to all protease inhibitors with little effect on infectivity. We found significant differences in the observed effect on infectivity with a pseudotype virus assay that requires the protease to cleave the cytoplasmic tail of the amphotropic murine leukemia virus (MuLV) Env protein. Additionally, we were able to mimic the fitness loss associated with resistance mutations by directly reducing the level of virion-associated protease activity. Virions containing 50% of a D25A mutant protease were 3- to 5-fold more sensitive to protease inhibitors. This level of reduction in protease activity also resulted in a 2-fold increase in sensitivity to nonnucleoside inhibitors of reverse transcriptase and a similar increase in sensitivity to zidovudine (AZT), indicating a pleiotropic effect associated with reduced protease activity. These results highlight the interplay between enzyme activity, viral fitness, and inhibitor mechanism and sensitivity in the closed system of the viral replication complex.
Antiviral Breadth and Combination Potential of Peptide Triazole HIV-1 Entry Inhibitors
Authors: McFadden Karyn , Fletcher Patricia , Rossi Fiorella , Kantharaju  , Umashankara Muddagowda , Pirrone Vanessa , Rajagopal Srivats , Gopi Hosahudya , Krebs Fred C. , Martin-Garcia Julio , Shattock Robin J. , Chaiken Irwin 
Published: November 2011

ABSTRACT
The first stage of human immunodeficiency virus type 1 (HIV-1) infection involves the fusion of viral and host cellular membranes mediated by viral envelope glycoprotein gp120. Inhibitors that specifically target gp120 are gaining increased attention as therapeutics or preventatives to prevent the spread of HIV-1. One promising new group of inhibitors is the peptide triazoles, which bind to gp120 and simultaneously block its interaction with both CD4 and the coreceptor. In this study, we assessed the most potent peptide triazole, HNG-156, for inhibitory breadth, cytotoxicity, and efficacy, both alone and in combination with other antiviral compounds, against HIV-1. HNG-156 inhibited a panel of 16 subtype B and C isolates of HIV-1 in a single-round infection assay. Inhibition of cell infection by replication-competent clinical isolates of HIV-1 was also observed with HNG-156. We found that HNG-156 had a greater than predicted effect when combined with several other entry inhibitors or the reverse transcriptase inhibitor tenofovir. Overall, we find that HNG-156 is noncytotoxic, has a broad inhibition profile, and provides a positive combination with several inhibitors of the HIV-1 life cycle. These results support the pursuit of efficacy and toxicity analyses in more advanced cell and animal models to develop peptide triazole family inhibitors of HIV-1 into antagonists of HIV-1 infection.
Decoding the Functional Roles of Cationic Side Chains of the Major Antimicrobial Region of Human Cathelicidin LL-37
Authors: Wang Guangshun , Epand Raquel F. , Mishra Biswajit , Lushnikova Tamara , Thomas Vinai Chittezham , Bayles Kenneth W. , Epand Richard M. 
Published: November 2011

ABSTRACT

Human cathelicidin LL-37 is a critical cationic antimicrobial peptide for host defense against infection, immune modulation, and wound healing. This article elucidates the functional roles of the cationic side chains of the major antimicrobial region of LL-37, corresponding to residues 17 to 32 (designated GF-17). Antimicrobial assays, killing kinetics studies, and vesicle leakage experiments all indicate that a conversion of lysines to arginines affected the ability of the peptide to kill the Gram-positive
Staphylococcus aureus
strain USA300. Alanine scanning experiments show that
S. aureus
is less sensitive than
Escherichia coli
to a single cationic residue mutation of GF-17. Among the five cationic residues, R23 appears to be somewhat important in killing
S. aureus
. However, R23 and K25 of GF-17 are of prime importance in killing the Gram-negative organism
E. coli
. In particular, R23 is essential for (i) rapid recognition, (ii) permeation of the
E. coli
outer membrane, (iii) clustering of anionic lipids in a membrane system mimicking the
E. coli
inner membrane, and (iv) membrane disruption. Bacterial aggregation (i.e., rapid recognition via charge neutralization) is the first step of the peptide action. Structurally, R23 is located in the interface (i.e., the first action layer), a situation ideal for the interactions listed above. In contrast, residues K18, R19, and R29 are on the hydrophilic surface of the amphipathic helix and play only a secondary role. Mapping of the functional spectrum of cationic residues of GF-17 provides a solid basis for engineering bacterium-specific antimicrobials using this highly potent template.
PD 404,182 Is a Virocidal Small Molecule That Disrupts Hepatitis C Virus and Human Immunodeficiency Virus
Authors: Chamoun Ana Maria , Chockalingam Karuppiah , Bobardt Michael , Simeon Rudo , Chang Jinhong , Gallay Philippe , Chen Zhilei 
Published: November 2011

ABSTRACT

We describe a virucidal small molecule, PD 404,182, that is effective against hepatitis C virus (HCV) and human immunodeficiency virus (HIV). The median 50% inhibitory concentrations (IC
50
s) for the antiviral effect of PD 404,182 against HCV and HIV in cell culture are 11 and 1 μM, respectively. The antiviral activity of PD 404,182 is due to the physical disruption of virions that is accompanied to various degrees (depending on the virus and exposure temperature/time) by the release of viral nucleic acids into the surrounding medium. PD 404,182 does not directly lyse liposomal membranes even after extended exposure, and it shows no attenuation in antiviral activity when preincubated with liposomes of various lipid compositions, suggesting that the compound inactivates viruses through interaction with a nonlipid structural component of the virus. The virucidal activity of PD 404,182 appears to be virus specific, as little to no viral inactivation was detected with the enveloped Dengue and Sindbis viruses. PD 404,182 effectively inactivates a broad range of primary isolates of HIV-1 as well as HIV-2 and simian immunodeficiency virus (SIV), and it does not exhibit significant cytotoxicity with multiple human cell lines
in vitro
(50% cytotoxic concentration, >300 μM). The compound is fully active in cervical fluids, although it exhibits decreased potency in the presence of human serum, retains its full antiviral potency for 8 h when in contact with cells, and is effective against both cell-free and cell-associated HIV. These qualities make PD 404,182 an attractive candidate anti-HIV microbicide for the prevention of HIV transmission through sexual intercourse.
In Vitro
Activities of Candidate Microbicides against Cell-Associated HIV
Authors: Selhorst Philippe , Grupping Katrijn , Bourlet Thomas , Delézay Olivier , Ariën Kevin K. , Vanham Guido 
Published: November 2011

ABSTRACT

Most research on HIV transmission and microbicides focuses on the inhibition of cell-free virus (CFV) present in genital secretions. However, an effective microbicide should also block the transmission of cell-associated virus (CAV) originating from seminal T cells and macrophages. Because inhibition of CAV remains controversial, especially for viral entry inhibitors, we developed a novel
in vitro
assay to evaluate the activities of different classes of candidate microbicides against cell-free HIV and HIV-infected leukocytes (i.e., resting peripheral blood mononuclear cells [PBMC], activated PBMC, and monocyte-derived macrophages). The assay is based on two CD4
+
CXCR4
+
T-cell lines (R5MaRBLE and X4MaRBLE) that both contain a firefly luciferase reporter gene but differ in the expression of the CCR5 coreceptor. Consequently, the quantification of the luciferase activities and the Gag p24 concentrations in cocultures of R5-tropic HIV-infected leukocytes with each cell line separately allowed us to discriminate between the infection of the cell lines (i.e., target cells), the ongoing infection in the HIV-infected leukocytes (i.e., effector cells), and the total infection of the coculture (i.e., effector plus target cells). All 14 antiretrovirals tested were able to block target cell infection by all three sources of CAV, although a small decrease in activity (2- to 18-fold) was observed for all entry inhibitors. On the other hand, the production of Gag p24 by the infected effector cells could be blocked only by protease inhibitors. Overall, these results show that entry and protease inhibitors are eligible drug classes for inclusion in future combination microbicides.
Entamoeba histolytica Induces Intestinal Cathelicidins but Is Resistant to Cathelicidin-Mediated Killing
Authors: Cobo Eduardo R. , He Chen , Hirata Ken , Hwang Grace , Tran UyenPhuong , Eckmann Lars , Gallo Richard L. , Reed Sharon L. 
Published: November 2011

ABSTRACTThe enteric protozoan parasiteEntamoeba histolyticais the cause of potentially fatal amebic colitis and liver abscesses.E. histolyticatrophozoites colonize the colon, where they induce inflammation, penetrate the mucosa, and disrupt the host immune system. The early establishment ofE. histolyticain the colon occurs in the presence of antimicrobial human (LL-37) and murine (CRAMP [cathelin-related antimicrobial peptide]) cathelicidins, essential components of the mammalian innate defense system in the intestine. Studying this early step in the pathogenesis of amebic colitis, we demonstrate thatE. histolyticatrophozoites or their released proteinases, including cysteine proteinase 1 (EhCP1), induce intestinal cathelicidins in human intestinal epithelial cell lines and in a mouse model of amebic colitis. Despite induction,E. histolyticatrophozoites were found to be resistant to killing by these antimicrobial peptides, and LL-37 and CRAMP were rapidly cleaved by released amebic cysteine proteases. The cathelicidin fragments however, did maintain their antimicrobial activity against bacteria. Degradation of intestinal cathelicidins is a novel function ofE. histolyticacysteine proteinases in the evasion of the innate immune system in the bowel. Thus, early intestinal epithelial colonization of invasive trophozoites involves a complex interplay in which the ultimate outcome of infection depends in part on the balance between degradation of cathelicidins by amebic released cysteine proteinases and upregulation of proinflammatory mediators which trigger the inflammatory response.