bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a
Mycobacterium smegmatis
Mutant Lacking Penicillin Binding Protein 1
Authors: Billman-Jacobe Helen , Haites Ruth E. , Coppel Ross L. 
Published: October 2018

ABSTRACT

The
ponA
gene of
Mycobacterium smegmatis
encodes a 95-kDa penicillin binding protein, PBP1, that is similar to PBP1s of
Mycobacterium tuberculosis
and
Mycobacterium leprae
. Transposon disruption of
ponA
in
M. smegmatis
resulted in a PBP1-deficient mutant that was sensitive to β-lactam antibiotics, was more permeable to glycine, and grew slowly in liquid culture.
Mechanism Underlying Levofloxacin Uptake by Human Polymorphonuclear Neutrophils
Authors: Vazifeh Doina , Bryskier André , Labro Marie-Thérèse 
Published: October 2018

ABSTRACT

The mechanism of radiolabeled levofloxacin ([
3
H]levofloxacin) uptake by human polymorphonuclear neutrophils (PMNs) was investigated by a classical velocity centrifugation technique. PMNs were incubated with levofloxacin for 5 to 180 min under various conditions before centrifugation through an oil cushion. Radioactivity was measured in the cell pellet to determine the amount of cell-associated drug. The uptake of levofloxacin was moderate with a cellular concentration/extracellular concentration ratio of about 4 to 6. Levofloxacin accumulated in PMNs parallel to the extracellular concentration, without saturation, over the range of 2.5 to 200 mg/liter (linear regression analysis:
r
= 0.92;
P
< 0.001). The activation energy was low (36 ± 7.2 kJ/mol). Levofloxacin uptake was increased in Ca
2+
-depleted, EGTA-containing medium by approximately 33% (
P
= 0.022), while Ni
2+
, a Ca
2+
channel inhibitor, inhibited it in a concentration-dependent manner, with the concentration that inhibited 50% of control uptake being approximately 2.65 mM. Verapamil (an
l
-type Ca
2+
channel inhibitor) and other pharmacologic agents which modify Ca
2+
homeostasis did not modify levofloxacin uptake. Interestingly, Ca
2+
and Mg
2+
inhibited levofloxacin uptake in a concentration-dependent manner. EGTA, Ni
2+
, and verapamil did not modify levofloxacin efflux; thapsigargin, a Ca
2+
pool-releasing agent, modestly increased the intracellular retention of levofloxacin. In addition, contrary to other fluoroquinolones, probenecid at 1 to 10 mM did not modify either levofloxacin uptake or efflux. These data are consistent with a mechanism of passive accumulation of levofloxacin in PMNs. Extracellular Ca
2+
and Mg
2+
may influence the structural conformation of levofloxacin or the lipophilicity of PMN membranes, thus explaining their effect on levofloxacin uptake.
Genetic Variation and Susceptibilities to Protease Inhibitors among Subtype B and F Isolates in Brazil
Authors: Tanuri Amilcar , Vicente Ana C. P. , Otsuki Koko , Ramos Carlos A. , Ferreira Orlando C. , Schechter Mauro , Janini Luis M. , Pieniazek Danuta , Rayfield Mark A. 
Published: October 2018

ABSTRACT

The genetic variation of the human immunodeficiency virus type 1 (HIV-1) protease gene (
prt
) permits the classification of HIV-1 strains into five distinct protease subtypes, which follow the
gag
subtyping patterns. The susceptibilities of non-B-subtype strains to protease inhibitors (PIs) and other antiretroviral drugs remain largely unknown. Subtype F is the main non-B strain contributing to the Brazilian epidemic, accounting for 15 to 20% of these infections. In this work, we report the findings on 81 isolates from PI-naive Brazilian patients collected between 1993 and 1997. In addition, the relevant PI resistance mutations and their phenotypes were determined in vitro for 15 of these patients (B = 9 and F = 6). Among these, the subtype F samples evidenced high sensitivities in vitro to ritonavir and indinavir, with MICs at which 50 and 90% of the isolates are inhibited similar to those of both the Brazilian and the U.S. subtype B isolates. Analysis of the 81 Brazilian
prt
sequences demonstrated that the subtype F consensus sequence differs from the U.S. and Brazilian subtype B consensus in eight positions (I15V, E35D, M36I, R41K, R57K, Q61N, L63P, and L89M). The frequency of critical PI resistance substitutions (amino acid changes D30N, V82A/F/T, I84V, N88D, and L90M) among Brazilian isolates is very low (mean, 2.5%), and the associated secondary substitutions (amino acid positions 10L, 20K, 36M, 46M, 48G, 54I, 63P, 71A, and 77A) are infrequent. These observations document the relative rarity of resistance to PIs in the treatment of patients infected with HIV-1 subtype F in South America.
Characterization of SFO-1, a Plasmid-Mediated Inducible Class A β-Lactamase from
Enterobacter cloacae
Authors: Matsumoto Yoshimi , Inoue Matsuhisa 
Published: October 2018

ABSTRACT

Enterobacter cloacae
8009 produced an inducible class A β-lactamase which hydrolyzed cefotaxime efficiently. It also hydrolyzed other β-lactams except cephamycins and carbapenems. The activity was inhibited by clavulanic acid and imipenem. The
bla
gene was transferable to
Escherichia coli
by electroporation of plasmid DNA. The molecular mass of the β-lactamase was 29 kDa and its pI was 7.3. All of these phenotypic characteristics of the enzyme except for inducible production resemble those of some extended-spectrum class A β-lactamases like FEC-1. The gene encoding this β-lactamase was cloned and sequenced. The deduced amino acid sequence of the β-lactamase was homologous to the AmpA sequences of the
Serratia fonticola
chromosomal enzyme (96%), MEN-1 (78%),
Klebsiella oxytoca
chromosomal enzymes (77%), TOHO-1 (75%), and FEC-1 (72%). The conserved sequences of class A β-lactamases, including the S-X(T)-X(S)-K motif, in the active site were all conserved in this enzyme. On the basis of the high degree of homology to the β-lactamase of
S. fonticola
, the enzyme was named SFO-1. The
ampR
gene was located upstream of the
ampA
gene, and the AmpR sequence of SFO-1 had homology with the AmpR sequences of the chromosomal β-lactamases from
Citrobacter diversus
(80%),
Proteus vulgaris
(68%), and
Pseudomonas aeruginosa
(60%). SFO-1 was also inducible in
E. coli
. However, a transformant harboring plasmid without intact
ampR
produced a small amount of β-lactamase constitutively, suggesting that AmpR works as an activator of
ampA
of SFO-1. This is the first report from Japan describing an inducible plasmid-mediated class A β-lactamase in gram-negative bacteria.
Therapeutic Effects of Benzoxazinorifamycin KRM-1648 Administered Alone or in Combination with a Half-Sized Secretory Leukocyte Protease Inhibitor or the Nonsteroidal Anti-Inflammatory Drug Diclofenac Sodium againstMycobacterium aviumComplex Infection in Mice
Authors: Sano Chiaki , Shimizu Toshiaki , Sato Katsumasa , Kawauchi Hideyuki , Kawahara Shin , Tomioka Haruaki 
Published: October 2018

ABSTRACTThe effects of half-sized secretory leukocyte protease inhibitor or diclofenac sodium administered alone or in combination with the benzoxazinorifamycin KRM-1648 on the therapeutic efficacy of KRM-1648 againstMycobacterium aviumcomplex (MAC) in mice were studied. Neither of the two anti-inflammatory drugs affected the efficacy of KRM-1648, while they exerted significant modulating effects on tumor necrosis factor alpha production by MAC-infected macrophages.
Updated Sequence Information for TEM β-Lactamase Genes
Authors: Goussard Sylvie , Courvalin Patrice 
Published: October 2018

ABSTRACT

The sequences of the promoter regions and of the structural genes for 13 penicillinase, extended-spectrum, and inhibitor-resistant TEM-type β-lactamases have been determined, and an updated
bla
TEM
gene nomenclature is proposed.
Human Herpesvirus 8 DNA Load in Leukocytes of Human Immunodeficiency Virus-Infected Subjects: Correlation with the Presence of Kaposi’s Sarcoma and Response to Anticytomegalovirus Therapy
Authors: Boivin Guy , Gaudreau Annie , Toma Emil , Lalonde Richard , Routy Jean-Pierre , Murray Gilles , Handfield Julie , Bergeron Michel G. 
Published: October 2018

ABSTRACT

Specific human herpesvirus 8 (HHV-8) DNA sequences were found in leukocytes of 12 of 29 (41.4%) AIDS subjects with Kaposi’s sarcoma (KS), whereas they were found in 4 of 43 (9.3%) AIDS subjects without KS (
P
= 0.003), although the peak HHV-8 DNA load in PCR-positive subjects with KS (mean, 425 copies per 0.2 μg of DNA) did not significantly differ from the one found in PCR-positive patients without KS (mean, 218 copies). The use of intravenous ganciclovir or foscarnet therapy to treat cytomegalovirus disease did not affect the HHV-8 DNA load in seven patients for whom serial samples were analyzed.
RecA-Mediated Gene Conversion and Aminoglycoside Resistance in Strains Heterozygous for rRNA
Authors: Prammananan Therdsak , Sander Peter , Springer Burkhard , Böttger Erik C. 
Published: October 2018

ABSTRACT

Clinical resistance to aminoglycosides in general is due to enzymatic drug modification. Mutational alterations of the small ribosomal subunit rRNA have recently been found to mediate acquired resistance in bacterial pathogens in vivo. In this study we investigated the effect of 16S rRNA heterozygosity (wild-type [wt] and mutant [mut] operons at position 1408 [1408
wt
/1408
mut
]) on aminoglycoside resistance. Using an integrative vector, we introduced a single copy of a mutated rRNA operon (1408 A→G) into
Mycobacterium smegmatis
, which carries two chromosomal wild-type rRNA operons; the resultant transformants exhibited an aminoglycoside-sensitive phenotype. In contrast, introduction of the mutated rRNA operon into an
M. smegmatis rrnB
knockout strain carrying a single functional chromosomal wild-type rRNA operon resulted in aminoglycoside-resistant transformants. Subsequent analysis by DNA sequencing and RNase protection assays unexpectedly demonstrated a homozygous mutant genotype, rRNA
mut
/rRNA
mut
, in the resistant transformants. To investigate whether RecA-mediated gene conversion was responsible for the aminoglycoside-resistant phenotype in the rRNA
wt
/rRNA
mut
strains,
recA
mutant strains were generated by allelic exchange techniques. Transformation of the
recA rrnB M. smegmatis
mutant strains with an integrative vector expressing a mutated rRNA operon (
Escherichia coli
position 1408 A→G) resulted in transformants with an aminoglycoside-sensitive phenotype. Subsequent analysis showed stable heterozygosity at 16S rRNA position 1408 with a single wild-type allele and a single resistant allele. These results demonstrate that rRNA-mediated mutational resistance to aminoglycosides is recessive.
Efflux-Mediated Aminoglycoside and Macrolide Resistance in
Burkholderia pseudomallei
Authors: Moore Richard A. , DeShazer David , Reckseidler Shauna , Weissman Ania , Woods Donald E. 
Published: October 2018

ABSTRACT

Burkholderia pseudomallei
, the causative agent of melioidosis, is intrinsically resistant to a wide range of antimicrobial agents including β-lactams, aminoglycosides, macrolides, and polymyxins. We used Tn
5
-OT182 to mutagenize
B. pseudomallei
to identify the genes involved in aminoglycoside resistance. We report here on the identification of AmrAB-OprA, a multidrug efflux system in
B. pseudomallei
which is specific for both aminoglycoside and macrolide antibiotics. We isolated two transposon mutants, RM101 and RM102, which had 8- to 128-fold increases in their susceptibilities to the aminoglycosides streptomycin, gentamicin, neomycin, tobramycin, kanamycin, and spectinomycin. In addition, both mutants, in contrast to the parent, were susceptible to the macrolides erythromycin and clarithromycin but not to the lincosamide clindamycin. Sequencing of the DNA flanking the transposon insertions revealed a putative operon consisting of a resistance, nodulation, division-type transporter, a membrane fusion protein, an outer membrane protein, and a divergently transcribed regulator protein. Consistent with the presence of an efflux system, both mutants accumulated [
3
H]dihydrostreptomycin, whereas the parent strain did not. We constructed an
amr
deletion strain,
B. pseudomallei
DD503, which was hypersusceptible to aminoglycosides and macrolides and which was used successfully in allelic exchange experiments. These results suggest that an efflux system is a major contributor to the inherent high-level aminoglycoside and macrolide resistance found in
B. pseudomallei
.
In Vitro Activities of Cephalosporins and Quinolones againstEscherichia coliStrains Isolated from Diarrheic Dairy Calves
Authors: Orden José Antonio , Ruiz-Santa-Quiteria José Antonio , García Silvia , Cid Dolores , de la Fuente Ricardo 
Published: October 2018

ABSTRACTThe in vitro activities of several cephalosporins and quinolones against 195 strains ofEscherichia coliisolated from dairy calves affected by neonatal diarrhea were determined. One hundred thirty-seven of these strains produced one or more potential virulence factors (F5, F41, F17, cytotoxic necrotizing factor, verotoxin, and theeaegene), but the remaining 58 strains did not produce any of these factors. From 11 to 18% of theE. colistrains were resistant to cephalothin, nalidixic acid, enoxacin, and enrofloxacin. However, cefuroxime, cefotaxime, and cefquinome were highly effective against theE. coliisolates tested. Some significant differences (P< 0.05) in resistance to quinolones between the strains producing potential virulence factors and nonfimbriated, nontoxigenic,eae-negative strains were found. Thus,eae-positive, necrotoxigenic, and verotoxigenic (except for nalidixic acid)E. colistrains were significantly more sensitive to nalidixic acid, enoxacin, and enrofloxacin than nonfimbriated, nontoxigenic,eae-negative strains. Moreover,eae-positive strains were significantly more sensitive to enoxacin and enrofloxacin than F5-positive strains. Thus, the results of this study suggest that the bovineE. colistrains that produce some potential virulence factors are more sensitive to quinolones than those that do not express these factors.
Alternative Oxidase Inhibitors Potentiate the Activity of Atovaquone against
Plasmodium falciparum
Authors: Murphy Anina D. , Lang-Unnasch Naomi 
Published: October 2018

ABSTRACT

Recent evidence suggests that the malaria parasite
Plasmodium falciparum
utilizes a branched respiratory pathway including both a cytochrome chain and an alternative oxidase. This branched respiratory pathway model has been used as a basis for examining the mechanism of action of two antimalarial agents, atovaquone and proguanil. In polarographic assays, atovaquone immediately reduced the parasite oxygen consumption rate in a concentration-dependent manner. This is consistent with its previously described role as an inhibitor of the cytochrome bc
1
complex. Atovaquone maximally inhibited the rate of
P. falciparum
oxygen consumption by 73% ± 10%. At all atovaquone concentrations tested, the addition of the alternative oxidase inhibitor, salicylhydroxamic acid, resulted in a further decrease in the rate of parasite oxygen consumption. At the highest concentrations of atovaquone tested, the activities of salicylhydroxamic acid and atovaquone appear to overlap, suggesting that at these concentrations, atovaquone partially inhibits the alternative oxidase as well as the cytochrome chain. Drug interaction studies with atovaquone and salicylhydroxamic acid indicate atovaquone’s activity against
P. falciparum
in vitro is potentiated by this alternative oxidase inhibitor, with a sum fractional inhibitory concentration of 0.6. Propyl gallate, another alternative oxidase inhibitor, also potentiated atovaquone’s activity, with a sum fractional inhibitory concentration of 0.7. Proguanil, which potentiates atovaquone activity in vitro and in vivo, had a small effect on parasite oxygen consumption in polarographic assays when used alone or in the presence of atovaquone or salicylhydroxamic acid. This suggests that proguanil does not potentiate atovaquone by direct inhibition of either branch of the parasite respiratory chain.
Lack of Absorption of Didanosine after Rectal Administration in Human Immunodeficiency Virus-Infected Patients
Authors: Wintergerst Uwe , Rolinski B. , Sölder B. , Bogner J. R. , Wolf E. , Jäger H. , Roscher A. A. , Belohradsky B. H. 
Published: October 2018

ABSTRACT

The feasibility of rectal administration of didanosine (DDI) was studied in six human immunodeficiency virus-infected patients. After oral intake of a DDI solution (100 mg/m
2
of body surface area) combined with an antacid (Maalox), pharmacokinetic parametric values were in accordance with previously published data; the mean ± standard deviation for terminal half-life was 59.5 ± 15.0 min, that for peak concentration was 5.2 ± 3.9 μmol/liter, and that for the area under the time-concentration curve (AUC) was 494 ± 412 min · μmol/liter. After rectal administration of a similarly prepared DDI solution (100 mg/m
2
of body surface area), plasma DDI levels were below the detection limit (0.1 μmol/liter) at all time points in five of the six patients, and in the remaining patient the AUC after rectal application was only 5% of that after oral administration. We conclude that oral administration of DDI cannot be easily replaced by rectal application.
Efficacy of RD3-0028 Aerosol Treatment against Respiratory Syncytial Virus Infection in Immunosuppressed Mice
Authors: Sudo Kenji , Watanabe Wataru , Konno Kenji , Sato Ryu , Kajiyashiki Tsuyoshi , Shigeta Shiro , Yokota Tomoyuki 
Published: October 2018

ABSTRACT
RD3-0028, a benzodithiin compound, has antiviral activity against respiratory syncytial virus (RSV) in cell culture. We used a mouse model of RSV infection to determine the in vivo effect of RD3-0028. Cyclophosphamide (CYP)-treated, immunosuppressed mice were inoculated intranasally. The lungs of the mice were removed on day 4. The virus titers of the lungs of RD3-0028-treated mice were compared to the virus titers of the lungs of virus-inoculated, untreated control mice. In an effort to increase the therapeutic effectiveness of this compound, RD3-0028 was administered by aerosol to RSV-infected mice by using a head-exposure system. Aerosols generated from reservoirs containing RD3-0028 (7 mg/ml) administered for 2 h twice daily for 3 days significantly reduced the pulmonary titer of RSV-infected mice. It is clear that the minimal effective dose of RD3-0028 for RSV-infected mice is significantly less than that of ribavirin, the only compound currently available for use against RSV disease. Furthermore, the RD3-0028 aerosol administration appeared to protect the lungs of infected, CYP-treated mice against tissue damage, as evidenced by the preservation of the lung architecture and a reduction in pulmonary inflammatory infiltrates. RD3-0028 aerosol was not toxic for mice at the therapeutic dose. The present study demonstrates the effectiveness of aerosol administration of RD3-0028 for RSV-infected mice.
Recombinant Bactericidal/Permeability-Increasing Protein (rBPI21) in Combination with Sulfadiazine Is Active againstToxoplasma gondii
Authors: Khan Anis A. , Lambert Lewis H. , Remington Jack S. , Araujo Fausto G. 
Published: October 2018

ABSTRACTThe activity of recombinant bactericidal/permeability-increasing protein (rBPI21), alone or in combination with sulfadiazine, on the intracellular replication ofToxoplasma gondiiwas assessed in vitro and in mice with acute toxoplasmosis. rBPI21markedly inhibited the intracellular growth ofT. gondiiin human foreskin fibroblasts (HFFs). Following 72 h of exposure, the 50% inhibitory concentration of rBPI21forT. gondiiwas 2.6 μg/ml, whereas only slight cytotoxicity for HFF cells was observed at the concentrations tested. Subsequent mathematical analyses revealed that the combination of rBPI21with sulfadiazine yielded slight to moderate synergistic effects againstT. gondiiin vitro. Infection of mice orally with C56 cysts or intraperitoneally (i.p.) with RH tachyzoites resulted in 100% mortality, whereas prolongation of the time to death or significant survival (P= 0.002) was noted for those animals treated with 5 to 20 mg of rBPI21per kg of body weight per day. Treatment with rBPI21in combination with sulfadiazine resulted in significant (P= 0.0001) survival of mice infected i.p. with tachyzoites but not of mice infected orally withT. gondiicysts. These results indicate that rBPI21is active in vitro and in vivo againstT. gondiiand that its activity is significantly enhanced when it is used in combination with sulfadiazine. To our knowledge, this is the first report of the activity of rBPI21against a protozoan parasite.
Nitrite Reductase from
Pseudomonas aeruginosa
Released by Antimicrobial Agents and Complement Induces Interleukin-8 Production in Bronchial Epithelial Cells
Authors: Sar Borann , Oishi Kazunori , Wada Akihiro , Hirayama Toshiya , Matsushima Kouji , Nagatake Tsuyoshi 
Published: October 2018

ABSTRACT

We have recently reported that nitrite reductase, a bifunctional enzyme located in the periplasmic space of
Pseudomonas aeruginosa
, could induce interleukin-8 (IL-8) generation in a variety of respiratory cells, including bronchial epithelial cells (K. Oishi et al. Infect. Immun. 65:2648–2655, 1997). In this report, we examined the mode of nitrite reductase (PNR) release from a serum-sensitive strain of live
P. aeruginosa
cells during in vitro treatment with four different antimicrobial agents or human complement. Bacterial killing of
P. aeruginosa
by antimicrobial agents induced PNR release and mediated IL-8 production in human bronchial epithelial (BET-1A) cells. Among these agents, imipenem demonstrated rapid killing of
P. aeruginosa
as well as rapid release of PNR and resulted in the highest IL-8 production. Complement-mediated killing of
P. aeruginosa
was also associated with PNR release and enhanced IL-8 production. The immunoprecipitates of the aliquots of bacterial culture containing imipenem or complement with anti-PNR immunoglobulin G (IgG) induced a twofold-higher IL-8 production than did the immunoprecipitates of the aliquots of bacterial culture with a control IgG. These pieces of evidence confirmed that PNR released in the aliquots of bacterial culture was responsible for IL-8 production in the BET-1A cells. Furthermore, the culture supernatants of the BET-1A cells stimulated with aliquots of bacterial culture containing antimicrobial agents or complement similarly mediated neutrophil migration in vitro. These data support the possibility that a potent inducer of IL-8, PNR, could be released from
P. aeruginosa
after exposure to antimicrobial agents or complement and contributes to neutrophil migration in the airways during bronchopulmonary infections with
P. aeruginosa.
Molecular Characterization of an Antibiotic Resistance Gene Cluster of
Salmonella typhimurium
DT104
Authors: Briggs Connie E. , Fratamico Pina M. 
Published: October 2018

ABSTRACT

Salmonella typhimurium
phage type DT104 has become an important emerging pathogen. Isolates of this phage type often possess resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT resistance). The mechanism by which DT104 has accumulated resistance genes is of interest, since these genes interfere with treatment of DT104 infections and might be horizontally transferred to other bacteria, even to unrelated organisms. Previously, several laboratories have shown that the antibiotic resistance genes of DT104 are chromosomally encoded and involve integrons. The antibiotic resistance genes conferring the ACSSuT-resistant phenotype have been cloned and sequenced. These genes are grouped within two district integrons and intervening plasmid-derived sequences. This sequence is potentially useful for detection of multiresistant DT104.