bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship between Capsular Type, Penicillin Susceptibility, and Virulence of Human
Streptococcus pneumoniae
Isolates in Mice
Authors: Azoulay-Dupuis E. , Rieux V. , Muffat-Joly M. , Bédos J. P. , Vallée E. , Rivier C. , Isturiz R. , Carbon C. , Moine P. 
Published: July 2002

ABSTRACT

We examined the relationship between penicillin susceptibility, peritoneal virulence in Swiss mice, and capsular type in a selection of 122 clinical
Streptococcus pneumoniae
isolates belonging to 24 serotypes. Regardless of the serotype, all 32 virulent strains were susceptible to penicillin, and all 41 strains with diminished susceptibility or resistance to penicillin were avirulent. The remaining 49 strains were both susceptible to penicillin and avirulent, irrespective of the serotype. On the basis of their capsular type and pathogenic behavior, strains fell into one of four groups. In the group consisting of serotypes 1, 3, and 4 (
n
= 16), strains were predominantly virulent (81.3%), and all were penicillin susceptible. In the serotype 6 group (
n
= 32), the frequency of virulence was significantly lower (34.4 versus 81.3%,
P
= 0.002), and strains were predominantly penicillin susceptible (71.9%). In the group composed of serotypes 9, 14, 19, and 23 (
n
= 50), all strains were avirulent, and 56% had decreased susceptibility (
n
= 12) or resistance to (
n
= 16) penicillin. The fourth group was heterogenous, as it pooled 24 strains of 15 different serotypes; in this group the frequency of virulence was 33.3%, and strains were predominantly penicillin susceptible (83.3%). These data point to a complex relationship between penicillin susceptibility and virulence in mice but do not entirely separate these characteristics from the role of the capsular type. The possibility that the mechanisms conferring penicillin resistance are related to those leading to a loss of virulence is supported by these findings.
Recombinant Green Fluorescent Protein-Expressing Human Cytomegalovirus as a Tool for Screening Antiviral Agents
Authors: Marschall Manfred , Freitag Martina , Weiler Sigrid , Sorg Gabriele , Stamminger Thomas 
Published: July 2002

ABSTRACT
A recombinant human cytomegalovirus (AD169-GFP) expressing green fluorescent protein was generated by homologous recombination. Infection of human fibroblast cultures with AD169-GFP virus produced stable and readily detectable amounts of GFP signals which were quantitated by automated fluorometry. Hereby, high levels of sensitivity and reproducibility could be achieved, compared to those with the conventional plaque reduction assay. Antiviral activities were determined for four reference compounds as well as a set of putative novel cytomegalovirus inhibitors. The results obtained were exactly in line with the known characteristics of reference compounds and furthermore revealed distinct antiviral activities of novel in vitro inhibitors. The fluorometric data could be confirmed by GFP-based flow cytometry and fluorescence microscopy. In addition, laboratory virus variants derived from the recombinant AD169-GFP virus provided further possibilities for study of the characteristics of drug resistance. The GFP-based antiviral assay appeared to be very reliable for measuring virus-inhibitory effects in concentration- and time-dependent fashions and might also be adaptable for high-throughput screenings of cytomegalovirus-specific antiviral agents.
Molecular Analysis of Antibiotic Resistance Gene Clusters in
Vibrio cholerae
O139 and O1 SXT Constins
Authors: Hochhut Bianca , Lotfi Yasmin , Mazel Didier , Faruque Shah M. , Woodgate Roger , Waldor Matthew K. 
Published: July 2002

ABSTRACT

Many recent Asian clinical
Vibrio cholerae
E1 Tor O1 and O139 isolates are resistant to the antibiotics sulfamethoxazole (Su), trimethoprim (Tm), chloramphenicol (Cm), and streptomycin (Sm). The corresponding resistance genes are located on large conjugative elements (SXT constins) that are integrated into
prfC
on the
V. cholerae
chromosome. We determined the DNA sequences of the antibiotic resistance genes in the SXT constin in MO10, an O139 isolate. In SXT
MO10
, these genes are clustered within a composite transposon-like structure found near the element's 5′ end. The genes conferring resistance to Cm (
floR
), Su (
sul
II), and Sm (
strA
and
strB
) correspond to previously described genes, whereas the gene conferring resistance to Tm, designated
dfr18
, is novel. In some other O139 isolates the antibiotic resistance gene cluster was found to be deleted from the SXT-related constin. The El Tor O1 SXT constin, SXT
ET
, does not contain the same resistance genes as SXT
MO10
. In this constin, the Tm resistance determinant was located nearly 70 kbp away from the other resistance genes and found in a novel type of integron that constitutes a fourth class of resistance integrons. These studies indicate that there is considerable flux in the antibiotic resistance genes found in the SXT family of constins and point to a model for the evolution of these related mobile elements.
Cyanovirin-N, a Potent Human Immunodeficiency Virus-Inactivating Protein, Blocks both CD4-Dependent and CD4-Independent Binding of Soluble gp120 (sgp120) to Target Cells, Inhibits sCD4-Induced Binding of sgp120 to Cell-Associated CXCR4, and Dissociates Bound sgp120 from Target Cells
Authors: Mori Toshiyuki , Boyd Michael R. 
Published: July 2002

ABSTRACT

Cyanovirin-N (CV-N), an 11-kDa protein originally isolated from the cyanobacterium
Nostoc ellipsosporum
, potently inactivates diverse strains of human immunodeficiency virus type 1 (HIV-1), HIV-2, simian immunodeficiency virus, and feline immunodeficiency virus. It has been well established that the HIV surface envelope glycoprotein gp120 is a molecular target of CV-N. We recently reported that CV-N impaired the binding of virion-associated gp120 to cell-associated CD4 and that CV-N preferentially inhibited binding of the glycosylation-dependent neutralizing monoclonal antibody 2G12 to gp120. However, CV-N did not interfere with the interactions of soluble CD4 (sCD4) with either soluble gp120 (sgp120) or virion-associated gp120. In the present study, we have evaluated the effects of CV-N on the binding of sgp120 to cell-associated CD4 to clarify the experimental basis of the previous binding results, and we further address the detailed mechanism of action of CV-N. Here we present evidence that (i) CV-N impairs both CD4-dependent and CD4-independent binding of sgp120 to the target cells, (ii) CV-N blocks the sCD4-induced binding of sgp120 with cell-associated coreceptor CXCR4, and (iii) CV-N dissociates bound sgp120 from target cells. The results illustrate that the measured effects of CV-N on gp120-CD4 binding interactions depend upon the type of CD4 (soluble or cell associated), but not upon the type of gp120 (soluble or virion associated), employed in the experimental protocol. In addition, this study reinforces that CV-N acts uniquely to prevent essential interactions between the envelope glycoprotein and target cell receptors and further supports the potential broad utility of CV-N as a microbicide to prevent the transmission of HIV and AIDS.
Efficacy of Zanamivir against Avian Influenza A Viruses That Possess Genes Encoding H5N1 Internal Proteins and Are Pathogenic in Mammals
Authors: Leneva Irina A. , Goloubeva Olga , Fenton Robert J. , Tisdale Margaret , Webster Robert G. 
Published: July 2002

ABSTRACT

In 1997, an avian H5N1 influenza virus, A/Hong Kong/156/97 (A/HK/156/97), caused six deaths in Hong Kong, and in 1999, an avian H9N2 influenza virus infected two children in Hong Kong. These viruses and a third avian virus [A/Teal/HK/W312/97 (H6N1)] have six highly related genes encoding internal proteins. Additionally, A/Chicken/HK/G9/97 (H9N2) virus has PB1 and PB2 genes that are highly related to those of A/HK/156/97 (H5N1), A/Teal/HK/W312/97 (H6N1), and A/Quail/HK/G1/97 (H9N2) viruses. Because of their similarities with the H5N1 virus, these H6N1 and H9N2 viruses may have the potential for interspecies transmission. We demonstrate that these H6N1 and H9N2 viruses are pathogenic in mice but that their pathogenicities are less than that of A/HK/156/97 (H5N1). Unadapted virus replicated in lungs, but only A/HK/156/97 (H5N1) was found in the brain. After three passages (P
3
) in mouse lungs, the pathogenicity of the viruses increased, with both A/Teal/HK/W312/97 (H6N1) (P
3
) and A/Quail/HK/G1/97 (H9N2) (P
3
) viruses being found in the brain. The neuraminidase inhibitor zanamivir inhibited viral replication in Madin-Darby canine kidney cells in virus yield assays (50% effective concentration, 8.5 to 14.0 μM) and inhibited viral neuraminidase activity (50% inhibitory concentration, 5 to 10 nM). Twice daily intranasal administration of zanamivir (50 and 100 mg/kg of body weight) completely protected infected mice from death. At a dose of 10 mg/kg, zanamivir completely protected mice from infection with H9N2 viruses and increased the mean survival day and the number of survivors infected with H6N1 and H5N1 viruses. Zanamivir, at all doses tested, significantly reduced the virus titers in the lungs and completely blocked the spread of virus to the brain. Thus, zanamivir is efficacious in treating avian influenza viruses that can be transmitted to mammals.
Atovaquone Nanosuspensions Show Excellent Therapeutic Effect in a New Murine Model of Reactivated Toxoplasmosis
Authors: Schöler Nadja , Krause Karsten , Kayser Oliver , Müller Rainer H. , Borner Klaus , Hahn Helmut , Liesenfeld Oliver 
Published: July 2002

ABSTRACT

Immunocompromised patients are at risk of developing toxoplasma encephalitis (TE). Standard therapy regimens (including sulfadiazine plus pyrimethamine) are hampered by severe side effects. While atovaquone has potent in vitro activity against
Toxoplasma gondii
, it is poorly absorbed after oral administration and shows poor therapeutic efficacy against TE. To overcome the low absorption of atovaquone, we prepared atovaquone nanosuspensions (ANSs) for intravenous (i.v.) administration. At concentrations higher than 1.0 μg/ml, ANS did not exert cytotoxicity and was as effective as free atovaquone (i.e., atovaquone suspended in medium) against
T. gondii
in freshly isolated peritoneal macrophages. In a new murine model of TE that closely mimics reactivated toxoplasmosis in immunocompromised hosts, using mice with a targeted mutation in the gene encoding the interferon consensus sequence binding protein, i.v.-administered ANS doses of 10.0 mg/kg of body weight protected the animals against development of TE and death. Atovaquone was detectable in the sera, brains, livers, and lungs of mice by high-performance liquid chromatography. Development of TE and mortality in mice treated with 1.0- or 0.1-mg/kg i.v. doses of ANS did not differ from that in mice treated orally with 100 mg of atovaquone/kg. In conclusion, i.v. ANSs may prove to be an effective treatment alternative for patients with TE.
Novel Cefotaximase (CTX-M-16) with Increased Catalytic Efficiency Due to Substitution Asp-240→Gly
Authors: Bonnet R. , Dutour C. , Sampaio J. L. M. , Chanal C. , Sirot D. , Labia R. , De Champs C. , Sirot J. 
Published: July 2002

ABSTRACT

Three clinical strains (
Escherichia coli
Rio-6,
E. coli
Rio-7, and
Enterobacter cloacae
Rio-9) collected in 1996 and 1999 from hospitals in Rio de Janeiro (Brazil) were resistant to broad-spectrum cephalosporins and gave a positive double-disk synergy test. Two
bla
CTX-M
genes encoding β-lactamases of pl 7.9 and 8.2 were implicated in this resistance: the
bla
CTX-M-9
gene observed in
E. coli
Rio-7 and
E. cloacae
Rio-9 and a novel CTX-M-encoding gene, designated
bla
CTX-M-16
, observed in
E. coli
strain Rio-6. The deduced amino acid sequence of CTX-M-16 differed from CTX-M-9 only by the substitution Asp-240→Gly. The CTX-M-16-producing
E. coli
transformant exhibited the same level of resistance to cefotaxime (MIC, 16 μg/ml) but had a higher MIC of ceftazidime (MIC, 8 versus 1 μg/ml) than the CTX-M-9-producing transformant. Enzymatic studies revealed that CTX-M-16 had a 13-fold higher affinity for aztreonam and a 7.5-fold higher k
cat
for ceftazidime than CTX-M-9, thereby showing that the residue in position 240 can modulate the enzymatic properties of CTX-M enzymes. The two
bla
CTX-M-9
genes and the
bla
CTX-M-16
gene were located on different plasmids, suggesting the presence of mobile elements associated with CTX-M-encoding genes. CTX-M-2 and CTX-M-8 enzymes were found in Brazil in 1996, and two other CTX-M β-lactamases, CTX-M-9 and CTX-M-16, were subsequently observed. These reports are evidence of the diversity of CTX-M-type extended-spectrum β-lactamases in Brazil.
Occurrence of Extended-Spectrum β-Lactamases in Members of the Family
Enterobacteriaceae
in Italy: Implications for Resistance to β-Lactams and Other Antimicrobial Drugs
Authors: Spanu T. , Luzzaro F. , Perilli M. , Amicosante G. , Toniolo A. , Fadda G. , The Italian ESBL Study Group  
Published: July 2002

ABSTRACT

An Italian nationwide survey was carried out to assess the prevalences and the antimicrobial susceptibilities of members of the family
Enterobacteriaceae
producing extended-spectrum β-lactamases (ESBLs). Over a 6-month period, 8,015 isolates were obtained from hospitalized patients and screened for resistance to extended-spectrum cephalosporins and monobactams. On the basis of a synergistic effect between clavulanate and selected β-lactams (ceftazidime, aztreonam, cefotaxime, cefepime, and ceftriaxone), 509 isolates were found to be ESBL positive (6.3%). Colony blot hybridization with
bla
TEM
and
bla
SHV
DNA probes allowed one to distinguish four different genotypes: TEM-positive, SHV-positive, TEM- and SHV-positive, and non-TEM, non-SHV ESBL types. MICs for each isolate (E-test) were obtained for widely used β-lactams, combinations of β-lactams with β-lactamase inhibitors, aminoglycosides, and fluoroquinolones. Among ESBL-positive strains,
Klebsiella pneumoniae
,
Proteus mirabilis
, and
Escherichia coli
accounted for 73.6% of isolates. Overall, TEM-type ESBLs were more prevalent than SHV-type enzymes (234 versus 173), whereas the prevalence of strains producing both TEM- and SHV-type ESBLs was similar to that of isolates producing non-TEM, non-SHV enzymes (55 and 38, respectively). In vitro, all but one of the ESBL-producing isolates remained susceptible to imipenem. Susceptibility to other drugs varied: piperacillin-tazobactam, 91%; amoxicillin-clavulanic acid, 85%; cefoxitin, 78%; amikacin, 76%; ampicillin-sulbactam, 61%; ciprofloxacin, 58%; and gentamicin, 56%. Associated resistance to aminoglycosides and ciprofloxacin was observed most frequently among TEM-positive strains. Since therapeutic options for multiresistant
Enterobacteriaceae
are limited, combinations of β-lactams and β-lactamase inhibitors appear to represent an important alternative for treating infections caused by ESBL-producing
Enterobacteriaceae
.
Protective Efficacy of a Sulfated Sialyl Lipid (NMSO3) against Human Rotavirus-Induced Diarrhea in a Mouse Model
Authors: Takahashi Kazuo , Ohashi Kazutaka , Abe Yurika , Mori Shuichi , Taniguchi Koki , Ebina Takusaburo , Nakagomi Osamu , Terada Masaki , Shigeta Shiro 
Published: July 2002

ABSTRACTAntiviral activity of sulfated sialyl lipid (NMSO3) against human rotavirus (RV) was examined in vitro and in vivo. NMSO3 inhibited the replication of four major serotypes (G1 to G4) of human rotavirus with a low 50% effective concentration of 1 to 5 μg/ml and 50% cytotoxic concentration of 153 μg/ml when determined by plaque assays with MA104 cells. Exposure of NMSO3 to HCl (pH 2.0) for 30 min exhibited no loss of anti-RV activity. Time-of-addition experiments revealed that NMSO3 inhibited the adsorption of four serotypes of RV to MA104 cells. Furthermore, an assay of virus binding with radiolabeled RVs revealed that NMSO3 inhibited the binding of virus to MA104 cells, suggesting that NMSO3 may bind to VP4 and/or VP7. Prophylactic oral administration of NMSO3 (10 μg three times per day, 4 days) to five suckling mice starting 30 min before inoculation of MO strain (3 × 106PFU/mouse) prevented the development of diarrhea. Four of five mice showed no stool or brown formed stool, and only one mouse showed brown soft stool, while water treatment caused watery diarrhea in all five mice. The mean titer of antibody to RV in mice which received NMSO3 at 10 μg three times per day for 4 days was significantly lower than that of untreated, infected mice. NMSO3 is a promising candidate for the prophylactic treatment of human RVs.
Cytotoxic Activities of Alkylphosphocholines against Clinical Isolates of
Acanthamoeba
spp
Authors: Walochnik Julia , Duchêne Michael , Seifert Karin , Obwaller Andreas , Hottkowitz Thomas , Wiedermann Gerhard , Eibl Hansjörg , Aspöck Horst 
Published: July 2002

ABSTRACT

Free-living amoebae of the genus
Acanthamoeba
are causing serious chronic conditions such as destructive keratitis in contact lens wearers or granulomatous amoebic encephalitis in individuals with compromised immune systems. Both are characterized by the lack of availability of sufficiently effective and uncomplicated, manageable treatments. Hexadecylphosphocholine (miltefosine) is licensed for use as a topical antineoplastic agent, but it is also active in vitro against several protozoan parasites, and it was applied very successfully for the treatment of human visceral leishmaniasis. The aim of our study was to evaluate the efficacy of hexadecylphosphocholine and other alkylphosphocholines (APCs) against
Acanthamoeba
spp. The in vitro activities of eight different APCs against three
Acanthamoeba
strains of various pathogenicities were determined. All substances showed at least amoebostatic effects, and some of them disrupted the amoebae, as shown by the release of cytoplasmic enzyme activity. Hexadecylphosphocholine exhibited the highest degree of cytotoxicity against trophozoites, resulting in complete cell death at a concentration as low as 40 μM, and also displayed significant cysticidal activity. Hexadecylphosphocholine may be a promising new candidate for the topical treatment of
Acanthamoeba
keratitis and, conceivably, even for the oral treatment of granulomatous amoebic encephalitis.
Biosynthetic Gene Cluster of Simocyclinone, a Natural Multihybrid Antibiotic
Authors: Trefzer A. , Pelzer S. , Schimana J. , Stockert S. , Bihlmaier C. , Fiedler H.-P. , Welzel K. , Vente A. , Bechthold A. 
Published: July 2002

ABSTRACT

The entire simocyclinone biosynthetic cluster (
sim
gene cluster) from the producer
Streptomyces antibioticus
Tü6040 was identified on six overlapping cosmids (1N1, 5J10, 2L16, 2P6, 4G22, and 1K3). In total, 80.7 kb of DNA from these cosmids was sequenced, and the analysis revealed 49 complete open reading frames (ORFs). These ORFs include genes responsible for the formation and attachment of four different moieties originating from at least three different pools of primary metabolites. Also in the
sim
gene cluster, four ORFs were detected that resemble putative regulatory and export functions. Based on the putative function of the gene products, a model for simocyclinone D8 biosynthesis was proposed. Biosynthetic mutants were generated by insertional gene inactivation experiments, and culture extracts of these mutants were analyzed by high-performance liquid chromatography. Production of simocyclinone D8 was clearly detectable in the wild-type strain but was not detectable in the mutant strains. This indicated that indeed the
sim
gene cluster had been cloned.
Bloodstream Infections by Extended-Spectrum β-Lactamase-Producing
Escherichia coli
and
Klebsiella pneumoniae
in Children: Epidemiology and Clinical Outcome
Authors: Kim Yun-Kyung , Pai Hyunjoo , Lee Hoan-Jong , Park Su-Eun , Choi Eun-Hwa , Kim Jungmin , Kim Je-Hak , Kim Eui-Chong 
Published: July 2002

ABSTRACT

To determine the epidemiologic features and clinical outcomes of bloodstream infections caused by extended-spectrum β-lactamase (ESBL)-producing
Escherichia coli
and
Klebsiella pneumoniae
isolates, cases of bacteremia caused by these organisms in children were analyzed retrospectively. Among the 157 blood isolates recovered from 1993 to 1998 at the Seoul National University Children's Hospital, the prevalence of ESBL production was 17.9% among the
E. coli
isolates and 52.9% among the
K. pneumoniae
isolates. The commonest ESBLs were SHV-2a and TEM-52. A novel ESBL, TEM-88, was identified. Pulsed-field gel electrophoresis analysis of the ESBL-producing organisms showed extensive diversity in clonality. The medical records of 142 episodes were reviewed. The risk factors for bloodstream infection with ESBL-producing organisms were prior hospitalization, prior use of oxyimino-cephalosporins, and admission to an intensive care unit within the previous month. There was no difference in clinical severity between patients infected with ESBL-producing strains (the ESBL group) and those infected with ESBL-nonproducing strains (the non-ESBL group) at the time of presentation. However, the overall fatality rate for the ESBL group was significantly higher than that for the non-ESBL group: 12 of 45 (26.7%) versus 5 of 87 (5.7%) (
P
= 0.001). In a subset analysis of patients treated with extended-spectrum cephalosporins with or without an aminoglycoside, favorable response rates were significantly higher in the non-ESBL group at the 3rd day (6 of 17 versus 33 of 51;
P
= 0.035), the 5th day (6 of 17 versus 36 of 50;
P
< 0.05), and the end of therapy (9 of 17 versus 47 of 50;
P
< 0.001). In conclusion, the ESBL production of the infecting organisms has a significant impact on the clinical course and survival of pediatric patients with bacteremia caused by
E. coli
and
K. pneumoniae
.
Tenofovir Diphosphate Is a Poor Substrate and a Weak Inhibitor of Rat DNA Polymerases α, δ, and ε*
Authors: Birkuš Gabriel , Hájek Miroslav , Kramata Pavel , Votruba Ivan , Holý Antonín , Otová Berta 
Published: July 2002

ABSTRACT

Tenofovir diphosphate (PMPApp) is a weak inhibitor of DNA polymerases (pol) α, δ, and ε*, with values for the

K
i

for PMPApp (
PMPApp

K
i

) relative to the

K
m

for dATP (
dATP

K
m

) of 10.2, 10.2, and 15.2, respectively. Its incorporation into DNA was about 1,000-fold less efficient than that of dATP, with
PMPApp

K
m

values 350-, 2,155-, and 187-fold higher than
dATP

K
m

values for pol α, δ, and ε*, respectively.
Microbial Degradation of the Multiply Branched Alkane 2,6,10,15,19,23-Hexamethyltetracosane (Squalane) by
Mycobacterium fortuitum
and
Mycobacterium ratisbonense
Authors: Berekaa Mahmoud M. , Steinbüchel Alexander 
Published: July 2002

ABSTRACT

Among several bacterial species belonging to the general
Gordonia
,
Mycobacterium
,
Micromonospora
,
Pseudomonas
, and
Rhodococcus
, only two mycobacterial isolates,
Mycobacterium fortuitum
strain NF4 and the new isolate
Mycobacterium ratisbonense
strain SD4, which was isolated from a sewage treatment plant, were capable of utilizing the multiply branched hydrocarbon squalane (2,6,10,15,19,23-hexamethyltetracosane) and its analogous unsaturated hydrocarbon squalene as the sole carbon source for growth. Detailed degradation studies and high-pressure liquid chromatography analysis showed a clear decrease of the concentrations of squalane and squalene during biomass increase. These results were supported by resting-cell experiments using strain SD4 and squalane or squalene as the substrate. The degradation of acyclic isoprenoids and alkanes as well as of acids derived from these compounds was also investigated. Inhibition of squalane and squalene degradation by acrylic acid indicated the possible involvement of β-oxidation in the degradation route. To our knowledge, this is the first report demonstrating the biodegradation of squalane by using defined axenic cultures.