bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Moxifloxacin, a New 8-Methoxyquinolone, for Treatment of Meningitis Caused by a PenicillinResistant Pneumococcus in Rabbits
Authors: Østergaard Christian , Klitmøller Sørensen Tina , Dahl Knudsen Jenny , Frimodt-Møller Niels
Published: October 2018

Moxifloxacin is a new 8-methoxyquinolone with high activity against gram-positive bacteria, including penicillin-resistant pneumococci. In an experimental meningitis model, we studied the pharmacokinetics of moxifloxacin in infected and uninfected rabbits and evaluated the antibiotic efficacies of moxifloxacin, ceftriaxone, and vancomycin against a penicillin-resistant
Streptococcus pneumoniae
strain (penicillin, ceftriaxone, vancomycin, and moxifloxacin MICs were 1, 0.5, 0.5, and 0.125 μg/ml, respectively). Moxifloxacin entered cerebrospinal fluid (CSF) readily, with peak values within 15 to 30 min after bolus intravenous infusion and with a mean percent penetration into normal and purulent CSF of approximately 50 and 80%, respectively. The bactericidal effect of moxifloxacin was concentration dependent, and regrowth was seen only when the concentration of moxifloxacin in CSF was below the minimal bactericidal concentration. All antibiotic-treated groups (moxifloxacin given in two doses of 40 mg/kg of body weight, moxifloxacin in two 20-mg/kg doses, ceftriaxone in one 125-mg/kg dose, and vancomycin in two 20-mg/kg doses) had significantly higher reductions in CSF bacterial concentration than the untreated group (
P
< 0.05). Moxifloxacin was as effective as vancomycin and ceftriaxone in reducing bacterial counts at all time points tested (3, 5, 10, and 24 h). Moreover, moxifloxacin given in two 40-mg/kg doses resulted in a significantly higher reduction in CSF bacterial concentration (in log
10
CFU per milliliter) than vancomycin within 3 h after the start of antibiotic treatment (3.49 [2.94 to 4.78] versus 2.50 [0.30 to 3.05];
P
< 0.05). These results indicate that moxifloxacin could be useful in the treatment of meningitis, including penicillin-resistant pneumococcal meningitis.
Pharmacokinetic Study of an Oral Cephalosporin, Cefdinir, in Hemodialysis Patients
Authors: Hishida Akira , Ohishi Kazuhisa , Nagashima Satoru , Kanamaru Mitsutaka , Obara Masao , Kitada Ayako
Published: October 2018

The pharmacokinetics of cefdinir were investigated in six hemodialysis patients. For the present study, two tests were carried out, one with 4 h of hemodialysis and the other without hemodialysis. Cefdinir was given orally to each patient in a dose of 100 mg, and blood was collected serially for 48 h after dosing in the test without dialysis and for 72 h in the test with dialysis. In the test without dialysis, the maximum plasma concentration (
C
max
) was 2.36 ± 0.53 μg/ml (mean ± standard deviation) and the time to
C
max
was 9.00 ± 2.45 h. The terminal elimination half-life (
t
1/2
) and area under the concentration-time curve (AUC) were 16.95 ± 1.20 h and 69.05 ± 14.84 μg · h/ml, respectively. In the test with dialysis,
t
1/2
during hemodialysis decreased approximately to one-sixth of that obtained in the test without dialysis, although
t
1/2
in the latter elimination phase did not differ from that in the nondialysis test. AUC was reduced to 43% of that in the test without dialysis. The fractional removal of cefdinir by hemodialysis was 61%. These findings indicate that clearance of cefdinir is prolonged in patients with renal failure, and cefdinir is well removed by introduction of hemodialysis, although
t
1/2
(during hemodialysis) and AUC were two and eight times higher than the data previously reported for healthy volunteers, respectively. The pharmacokinetic data suggest that 100 mg of oral cefdinir once a day would result in a sufficient concentration in plasma in hemodialysis patients, but this remains to be confirmed by multiple-dose studies.
Comparisons between Antimicrobial Pharmacodynamic Indices and Bacterial Killing as Described by Using the Zhi Model
Authors: Corvaisier S. , Maire P. H. , Bouvier d’yvoire M. Y. , Barbaut X. , Bleyzac N. , Jelliffe R. W.
Published: October 2018

Various suggestions have been made for empirical pharmacodynamic indices of antibiotic effectiveness, such as areas under the drug concentration-time curve in serum (AUC), AUC>MIC, AUC/MIC, area under the inhibitory curve (AUIC), AUC above MIC, and time above MIC (T>MIC). In addition, bacterial growth and killing models, such as the Zhi model, have been developed. The goal of the present study was to compare the empirical behavior of the Zhi model of bacterial growth and killing with the other empirical pharmacodynamic indices described above by using simulated clinical data analyzed with the USC*PACK PC clinical programs for adaptive control of drug therapy, with one model describing a concentration-dependent antibiotic (tobramycin) and another describing a concentration-independent antibiotic (ticarcillin). The computed relative number of CFU was plotted against each pharmacodynamic index, with each axis parameterized over time. We assumed that a good pharmacodynamic index should present a clear and continuous relationship between the time course of its values and the time course of the bacterial killing as seen with the Zhi model. Preliminary work showed that some pharmacodynamic indices were very similar. A good sensitivity to the change in the values of the MIC was shown for AUC/MIC and also forT>MIC. In addition, the time courses of some other pharmacodynamic indices were very similar. Since AUC/MIC is easily calculated and shows more sensitivity, it appeared to be the best of the indices mentioned above for the concentration-dependent drug, because it incorporated and used the MIC the best.T>MIC appeared to be the best index for a concentration-independent drug. We also propose a new composite index, weighted AUC (WAUC), which appears to be useful for both concentration-dependent and concentration-independent drugs.
P-Glycoprotein-Mediated Transport of Itraconazole across the Blood-Brain Barrier
Authors: Miyama Tetsuo , Takanaga Hitomi , Matsuo Hirotami , Yamano Katsuhiro , Yamamoto Koujirou , Iga Tatsuji , Naito Mikihiko , Tsuruo Takashi , Ishizuka Hitoshi , Kawahara Yukinori , Sawada Yasufumi
Published: October 2018

The mechanism for the accumulation of itraconazole (ITZ) in its elimination from the brain was studied in rats and mice. The concentration of ITZ in liver tissue declined in parallel with the plasma ITZ concentration until 24 h after intravenous injection of the drug (half-life, 5 h); however, the ITZ in brain tissue rapidly disappeared (half-life, 0.4 h). The time profiles of the brain/plasma ITZ concentration ratio (Kpvalue) showed a marked overshooting, and theKpvalue increased with increasing dose; these phenomena were not observed in the liver tissue. This finding indicates the occurrence of a nonlinear efflux of ITZ from the brain to the blood. Moreover, based on a pharmacokinetic model which hypothesized processes for both nonlinear and linear effluxes of ITZ from the brain to the blood, we found that the efflux rate constant in the saturable process was approximately sevenfold larger than that in the nonsaturable process. TheKpvalue for the brain tissue was significantly increased in the presence of ketoconazole or verapamil. The brainKpvalue formdr1aknockout mice was also significantly increased compared with that of control mice. Moreover, the uptake of vincristine or vinblastine, both of which are substrates of the P glycoprotein (P-gp), into mouse brain capillary endothelial cells was also significantly increased by ITZ or verapamil. In conclusion, P-gp in the brain capillary endothelial cells participates in a process of active efflux of ITZ from the brain to the blood at the blood-brain barrier, and ITZ can be an inhibitor of various substrates of P-gp.
Anti-Hepatitis B Virus Activity and Metabolism of 2′,3′-Dideoxy-2′,3′-Didehydro-β-
l
(−)-5-Fluorocytidine
Authors: Zhu Yong-Lian , Dutschman Ginger E. , Liu Shwu-Huey , Bridges Edward G. , Cheng Yung-Chi
Published: October 2018

2′,3′-Dideoxy-2′,3′-didehydro-β-
l
(−)-5-fluorocytidine [
l
(−)Fd4C] was found to be at least 10 times more potent than β-
l
-2′,3′-dideoxy-3′-thiacytidine [
l
(−)SddC; also called 3TC, or lamivudine]against hepatitis B virus (HBV) in culture. Its cytotoxicity against HepG2 growth in culture was also greater than that of
l
(−)SddC (3TC). There was no activity of this compound against mitochondrial DNA synthesis in cells at concentrations up to 10 μM. The dynamics of recovery of virus from the medium of cells pretreated with equal drug concentrations were slower with
l
(−)Fd4C than with
l
(−)SddC (3TC).
l
(−)Fd4C could be metabolized to mono-, di-, and triphosphate forms. The degree of
l
(−)Fd4C phosphorylation to the 5′-triphosphate metabolite was higher than the degree of
l
(−)SddC (3TC) phosphorylation when equal extracellular concentrations of the two drugs were used. The apparent

K
m

of
l
(−)Fd4C phosphorylated metabolites formed intracellularly was higher than that for
l
(−)SddC (3TC). This may be due in part to a difference in the behavior of
l
(−)Fd4C and
l
(−)SddC (3TC) towards cytosolic deoxycytidine kinase. Furthermore,
l
(−)Fd4C 5′-triphosphate was retained longer within cells than
l
(−)SddC (3TC) 5′-triphosphate.
l
(−)Fd4C 5′-triphosphate inhibited HBV DNA polymerase in competition with dCTP with a

K
i

of 0.069 ± 0.015 μM. Given the antiviral potency and unique pharmacodynamic properties of
l
(−)Fd4C, this compound should be considered for development as an expanded-spectrum anti-HBV drug.
Identification and Expression of Multidrug Transporters Responsible for Fluconazole Resistance in
Candida dubliniensis
Authors: Moran Gary P. , Sanglard Dominique , Donnelly Samantha M. , Shanley Diarmuid B. , Sullivan Derek J. , Coleman David C.
Published: October 2018

Candida dubliniensis
is a recently described
Candida
species associated with oral candidosis in human immunodeficiency virus (HIV)-infected and AIDS patients, from whom fluconazole-resistant clinical isolates have been previously recovered. Furthermore, derivatives exhibiting a stable fluconazole-resistant phenotype have been readily generated in vitro from fluconazole-susceptible isolates following exposure to the drug. In this study, fluconazole-resistant isolates accumulated up to 80% less [
3
H]fluconazole than susceptible isolates and also exhibited reduced susceptibility to the metabolic inhibitors 4-nitroquinoline-
N
-oxide and methotrexate. These findings suggested that
C. dubliniensis
may encode multidrug transporters similar to those encoded by the
C. albicans MDR1
,
CDR1
, and
CDR2
genes (
CaMDR1
,
CaCDR1
, and
CaCDR2
, respectively). A
C. dubliniensis
homolog of
CaMDR1
, termed
CdMDR1
, was cloned; its nucleotide sequence was found to be 92% identical to the corresponding
CaMDR1
sequence, while the predicted CdMDR1 protein was found to be 96% identical to the corresponding CaMDR1 protein. By PCR,
C. dubliniensis
was also found to encode homologs of
CDR1
and
CDR2
, termed
CdCDR1
and
CdCDR2
, respectively. Expression of
CdMDR1
in a fluconazole-susceptible Δ
pdr5
null mutant of
Saccharomyces cerevisiae
conferred a fluconazole-resistant phenotype and resulted in a 75% decrease in accumulation of [
3
H]fluconazole. Northern analysis of fluconazole-susceptible and -resistant isolates of
C. dubliniensis
revealed that fluconazole resistance was associated with increased expression of
CdMDR1
mRNA. In contrast, most studies showed that overexpression of
CaCDR1
was associated with fluconazole resistance in
C. albicans
. Increased levels of the CdMdr1p protein were also detected in fluconazole-resistant isolates. Similar results were obtained with fluconazole-resistant derivatives of
C. dubliniensis
generated in vitro, some of which also exhibited increased levels of
CdCDR1
mRNA and CdCdr1p protein. These results demonstrate that
C. dubliniensis
encodes multidrug transporters which mediate fluconazole resistance in clinical isolates and which can be rapidly mobilized, at least in vitro, on exposure to fluconazole.
Effect of Rebamipide, a Novel Antiulcer Agent, on
Helicobacter pylori
Adhesion to Gastric Epithelial Cells
Authors: Hayashi Shunji , Sugiyama Toshiro , Amano Ken-Ichi , Isogai Hiroshi , Isogai Emiko , Aihara Miki , Kikuchi Mikio , Asaka Masahiro , Yokota Kenji , Oguma Keiji , Fujii Nobuhiro , Hirai Yoshikazu
Published: October 2018

Helicobacter pylori
is a major etiological agent in gastroduodenal disorders. The adhesion of
H. pylori
to human gastric epithelial cells is the initial step of
H. pylori
infection. Inhibition of
H. pylori
adhesion is thus a therapeutic target in the prevention of
H. pylori
infection. Experiments were performed to evaluate the effect of rebamipide, a novel antiulcer agent, on
H. pylori
adhesion to gastric epithelial cells. MKN-28 and MKN-45 cells, derived from human gastric carcinomas, were used as target cells. Ten
H. pylori
strains isolated from patients with chronic gastritis and gastric ulcer were used in the study. We evaluated the effect of rebamipide on
H. pylori
adhesion to MKN-28 and MKN-45 cells quantitatively using our previously established enzyme-linked immunosorbent assay. The adhesion of
H. pylori
to MKN-28 and MKN-45 cells was significantly inhibited by pretreatment of these cells with 100 μg of rebamipide per ml. However, the adhesion was not affected by the pretreatment of
H. pylori
with rebamipide. On the other hand, the viabilities of
H. pylori
, MKN-28 cells, and MKN-45 cells were not affected by rebamipide. Our studies suggest that rebamipide inhibits the adhesion of
H. pylori
to gastric epithelial cells.
Generation of BioluminescentStreptococcus mutansand Its Usage in Rapid Analysis of the Efficacy of Antimicrobial Compounds
Authors: Loimaranta Vuokko , Tenovuo Jorma , Koivisto Leeni , Karp Matti
Published: October 2018

The oral bacteriumStreptococcus mutanswas transformed by electroporation with a shuttle vector (pCSS945) containing insect luciferase gene from a click beetle (Pyrophorus plagiophthalamus) resulting in a bioluminescent phenotype. ThisS. mutansstrain was used in experiments in which light emission was used as a rapid and, compared to conventional CFU counting, more convenient means of estimating the effects of various antimicrobial treatments. The basic parameters affecting in vivo light production by the strain were studied. It was found that pH 6.0 was optimal for incorporation of the substrated-luciferin for the luciferase reaction. The optimum concentration ofd-luciferin was approximately 150 μM at room temperature. Under optimum conditions the light emission in vivo increased rapidly to a constant level and thereafter had a decay of 0.6%/min when logarithmic-growth-phase cells were used. The light emission closely paralleled the numbers of CFU, giving a detectable signal from 30,000 cells and having a dynamic measurement range over 4 log CFU/relative light unit. The cells were treated with various antimicrobial agents, and the emitted bioluminescence was measured. With the bioluminescent measurements, the results were obtained within hours compared to the days required for agar plates, and also, the kinetics of the antibacterial actions could be followed. Thus, the light emission was found to be a reliable, sensitive, and real-time indicator of the bacteriostatic actions of the antimicrobial agents tested.
Characterization of the MexC-MexD-OprJ Multidrug Efflux System in Δ
mexA-mexB-oprM
Mutants of
Pseudomonas aeruginosa
Authors: Gotoh Naomasa , Tsujimoto Hideto , Tsuda Masataka , Okamoto Kiyomi , Nomura Atsuko , Wada Takaomi , Nakahashi Masaaki , Nishino Takeshi
Published: October 2018

Expression of the multidrug efflux system MexC-MexD-OprJ in
nfxB
mutants of
Pseudomonas aeruginosa
contributes to resistance to fluoroquinolones and the “fourth-generation” cephems (cefpirome and cefozopran), but not to most β-lactams, including the ordinary cephems (ceftazidime and cefoperazone).
nfxB
mutants also express a second multidrug efflux system, MexA-MexB-OprM, due to incomplete transcriptional repression of this operon by the
mexR
gene product. To characterize the contribution of the MexC-MexD-OprJ system to drug resistance in
P. aeruginosa
, a site-specific deletion method was employed to remove the
mexA-mexB-oprM
region from the chromosome of wild-type and
nfxB
strains of
P. aeruginosa
. Characterization of mutants lacking the
mexA-mexB-oprM
region clearly indicated that the MexC-MexD-OprJ efflux system is involved in resistance to the ordinary cephems as well as fluoroquinolones and the fourth-generation cephems but not to carbenicillin and aztreonam. Rabbit polyclonal antisera and murine monoclonal antibody against the components of the MexA-MexB-OprM system were prepared and used to demonstrate the reduced production of this efflux system in the
nfxB
mutants. Consistent with this, transcription of the
mexA-mexB-oprM
operon decreased in an
nfxB
mutant. This reduction appears to explain the hypersusceptibility of the
nfxB
mutant to β-lactams, including ordinary cephems.
Site-Specific Mutations in the 23S rRNA Gene of
Helicobacter pylori
Confer Two Types of Resistance to Macrolide-Lincosamide-Streptogramin B Antibiotics
Authors: Wang Ge , Taylor Diane E.
Published: October 2018

Clarithromycin resistance in
Helicobacter pylori
is mainly due to A-to-G mutations within the peptidyltransferase region of the 23S rRNA. In the present study, cross-resistance to macrolide, lincosamide, and streptogramin B (MLS) antibiotics (MLS phenotypes) has been investigated for several clinical isolates of
H. pylori
. Two major types of MLS resistance were identified and correlated with specific point mutations in the 23S rRNA gene. The A2142G mutation was linked with high-level cross-resistance to all MLS antibiotics (type I), and the A2143G mutation gave rise to an intermediate level of resistance to clarithromycin and clindamycin but no resistance to streptogramin B (type II). In addition, streptogramin A and streptogramin B were demonstrated to have a synergistic effect on both MLS-sensitive and MLS-resistant
H. pylori
strains. To further understand the mechanism of MLS resistance in
H. pylori
, we performed in vitro site-directed mutagenesis (substitution of G, C, or T for A at either position 2142 or 2143 of the 23S rRNA gene). The site-directed point mutations were introduced into a clarithromycin-susceptible strain,
H. pylori
UA802, by natural transformation followed by characterization of their effects on MLS resistance in an isogenic background. Strains with A-to-G and A-to-C mutations at the same position within the 23S rRNA gene had similar levels of clarithromycin resistance, and this level of resistance was higher than that for strains with the A-to-T mutation. Mutations at position 2142 conferred a higher level of clarithromycin resistance than mutations at position 2143. All mutations at position 2142 conferred cross-resistance to all MLS antibiotics, which corresponds to the type I MLS phenotype, whereas mutations at position 2143 were associated with a type II MLS phenotype with no resistance to streptogramin B. To explain that A-to-G transitions were predominantly observed in clarithromycin-resistant clinical isolates, we propose a possible mechanism by which A-to-G mutations are preferentially produced in
H. pylori
.
CTX-M-5, a Novel Cefotaxime-Hydrolyzing β-Lactamase from an Outbreak of
Salmonella typhimurium
in Latvia
Authors: Bradford Patricia A. , Yang Youjun , Sahm Daniel , Grope Ilze , Gardovska Dace , Storch Gregory
Published: October 2018

At a children’s hospital in Riga, Latvia, isolates identified as
Salmonella typhimurium
were found to be resistant to expanded-spectrum cephalosporins. Two of the resistant strains were analyzed for the mechanism of cephalosporin resistance. Isoelectric focusing revealed a common β-lactamase with a pI of 8.8. In addition, one of the strains produced a pI 7.6 β-lactamase. A transconjugant producing only the pI 7.6 enzyme was susceptible to expanded-spectrum cephalosporins; therefore, this enzyme was most likely SHV-1. Transformants producing only the pI 8.8 β-lactamase were resistant to cefotaxime and aztreonam but were susceptible or intermediate to ceftazidime. A substrate profile determined spectrophotometrically with purified enzyme revealed potent activity against cefotaxime, with a relative
k
cat
value of 95 (benzylpenicillin equal to 100). The enzyme showed lower relative
k
cat
values for ceftazidime (3.3) and aztreonam (9.3). In addition, the enzyme was inhibited by clavulanate, sulbactam and tazobactam, with 50% inhibitory concentrations of 19, 100, and 3.4 nM, respectively. These results indicated the presence of an unusual extended-spectrum β-lactamase. The gene expressing the pI 8.8 β-lactamase was cloned. Nucleotide sequencing revealed a β-lactamase gene that differs from the gene encoding CTX-M-2, which also originated from
S. typhimurium
, by 11 nucleotides, 4 of which result in amino acid substitutions: Ala27Thr, Val230Gly, Glu254Ala, and Ile278Val. These results indicated the presence of a novel extended-spectrum β-lactamase, designated CTX-M-5, that specifically confers resistance to cefotaxime.
Sensitivity of
Leishmania viannia panamensis
to Pentavalent Antimony Is Correlated with the Formation of Cleavable DNA-Protein Complexes
Authors: Lucumi Armando , Robledo Sara , Gama Vivian , Saravia Nancy G.
Published: October 2018

The emergence of
Leishmania
less sensitive to pentavalent antimonial agents (SbVs), the report of inhibition of purified topoisomerase I of
Leishmania donovani
by sodium stibogluconate (Pentostam), and the uncertain mechanism of action of antimonial drugs prompted an evaluation of SbVs in the stabilization of cleavable complexes in promastigotes of
Leishmania
(
Viannia
). The effect of camptothecin, an inhibitor of topoisomerase, and additive-free meglumine antimoniate (Glucantime) on the stabilization of cleavable DNA-protein complexes associated with the inhibition of topoisomerase was assessed in the human promonocytic cell line U-937, promastigotes of
L.
(
Viannia
)
panamensis
selected for SbV resistance in vitro, and the corresponding wild-type strain. The stabilization of cleavable complexes and the 50% effective dose (ED
50
) of SbVs for parasites isolated from patients with relapses were also evaluated. The median ED
50
for the wild-type strain was 16.7 μg of SbV/ml, while that of the line selected for resistance was 209.5 μg of SbV/ml. Treatment with both meglumine antimoniate and sodium stibogluconate (20 to 200 μg of SbV/ml) stabilized DNA-protein complexes in the wild-type strain but not the resistant line. The ED
50
s of the SbVs for
Leishmania
strains from patients with relapses was comparable to those for the line selected for in vitro resistance, and DNA-protein complexes were not stabilized by exposure to meglumine antimoniate. Cleavable complexes were observed in all
Leishmania
strains treated with camptothecin. Camptothecin stabilized cleavable complexes in U-937 cells; SbVs did not. The selective effect of the SbVs on the stabilization of DNA-protein complexes in
Leishmania
and the loss of this effect in naturally resistant or experimentally derived SbV-resistant
Leishmania
suggest that topoisomerase may be a target of antimonial drugs.
Disposition and Elimination of Meropenem in Cerebrospinal Fluid of Hydrocephalic Patients with External Ventriculostomy
Authors: Nau Roland , Lassek Christoph , Kinzig-Schippers Martina , Thiel Andreas , Prange Hilmar W. , Sörgel Fritz
Published: October 2018

The broad antibacterial spectrum and the low incidence of seizures in meropenem-treated patients qualifies meropenem for therapy of bacterial meningitis. The present study evaluates concentrations in ventricular cerebrospinal fluid (CSF) in the absence of pronounced meningeal inflammation. Patients with occlusive hydrocephalus caused by cerebrovascular diseases, who had undergone external ventriculostomy (
n
= 10, age range 48 to 75 years), received 2 g of meropenem intravenously over 30 min. Serum and CSF were drawn repeatedly and analyzed by liquid chromatography-mass spectroscopy. Pharmacokinetics were determined by noncompartmental analysis. Maximum concentrations in serum were 84.7 ± 23.7 μg/ml. A CSF maximum (
C
maxCSF
) of 0.63 ± 0.50 μg/ml (mean ± standard deviation) was observed 4.1 ± 2.6 h after the end of the infusion. C
maxCSF
and the area under the curve for CSF (AUC
CSF
) depended on the AUC for serum (AUC
S
), the CSF-to-serum albumin ratio, and the CSF leukocyte count. Elimination from CSF was considerably slower than from serum (half-life at β phase [
t
1/2β
] of 7.36 ± 2.89 h in CSF versus
t
1/2β
of 1.69 ± 0.60 h in serum). The AUC
CSF
/AUC
S
ratio for meropenem, as a measure of overall CSF penetration, was 0.047 ± 0.022. The AUC
CSF
/AUC
S
ratio for meropenem was similar to that for other β-lactam antibiotics with a low binding to serum proteins. The concentration maxima of meropenem in ventricular CSF observed in this study are high enough to kill fully susceptible pathogens. They may not be sufficient to kill bacteria with a reduced sensitivity to carbapenems, although clinical success has been reported for patients with meningitis caused by penicillin-resistant pneumococci and
Pseudomonas aeruginosa
.
Molecular Characterization of OXA-20, a Novel Class D β-Lactamase, and Its Integron from
Pseudomonas aeruginosa
Authors: Naas Thierry , Sougakoff Wladimir , Casetta Anne , Nordmann Patrice
Published: October 2018

The
Pseudomonas aeruginosa
Mus clinical isolate produces OXA-18, a pI 5.5 class D extended-spectrum β-lactamase totally inhibited by clavulanic acid (L. N. Philippon, T. Naas, A.-T. Bouthors, V. Barakett, and P. Nordmann, Antimicrob. Agents Chemother. 41:2188–2195, 1997). A second β-lactamase was cloned, and the recombinant
Escherichia coli
clone pPL10 expressed a pI 7.4 β-lactamase which conferred high levels of amoxicillin and ticarcillin resistance and which was partially inhibited by clavulanic acid. The 2.5-kb insert from pPL10 was sequenced, and a 266-amino-acid protein (OXA-20) was deduced; this protein has low amino acid identity with most of the class D β-lactamases except OXA-2, OXA-15, and OXA-3 (75% amino acid identity with each). OXA-20 is a restricted-spectrum oxacillinase and is unusually inhibited by clavulanic acid. OXA-20 is a peculiar β-lactamase because its translation initiates with a TTG (leucine) codon, which is rarely used as a translational origin in bacteria. Exploration of the genetic environment of
oxa20
revealed the presence of the following integron features: (i) a second antibiotic resistance gene,
aacA4
; (ii) an
intI1
gene; and (iii) two 59-base elements, each associated with either
oxa20
or
aacA4
. This integron is peculiar because it lacks the 3′ conserved region, and therefore is not a
sul1
-associated integron like most of them, and because its 3′ end is located within
tnpR
, a gene involved in the transposition of Tn
5393
, a gram-negative transposon.
P. aeruginosa
Mus produces two novel and unrelated oxacillinases, OXA-18 and OXA-20, both of which are inhibited by clavulanic acid.
Correlation between Quinolone Susceptibility Patterns and Sequences in the A and B Subunits of DNA Gyrase in Mycobacteria
Authors: Guillemin Isabelle , Jarlier Vincent , Cambau Emmanuelle
Published: October 2018

The in vitro activities of seven quinolones and the sequences of the quinolone resistance-determining regions (QRDR) in the A and B subunits of DNA gyrase were determined for 14 mycobacterial species. On the basis of quinolone activity, quinolones were arranged from that with the greatest to that with the least activity as follows: sparfloxacin, levofloxacin, ciprofloxacin, ofloxacin, pefloxacin, flumequine, and nalidixic acid. Based on MICs, the species could be organized into three groups: resistant (
Mycobacterium avium
,
M. intracellulare
,
M. marinum
,
M. chelonae
,
M. abscessus
[ofloxacin MICs, ≥8 μg/ml]), moderately susceptible (
M. tuberculosis
,
M. bovis
BCG,
M. kansasii
,
M. leprae
,
M. fortuitum
third biovariant,
M. smegmatis
[ofloxacin MICs, 0.5 to 1 μg/ml]), and susceptible (
M. fortuitum
,
M. peregrinum
,
M. aurum
[ofloxacin MICs, ≤0.25 μg/ml]). Peptide sequences of the QRDR of GyrB were identical in all the species, including the amino acids at the three positions known to be involved in acquired resistance to quinolone, i.e., 426 (Asp), 447 (Arg), and 464 (Asn) (numbering system used for
Escherichia coli
). The last two residues could be involved in the overall low level of susceptibility of mycobacteria to quinolones since they differ from those found in the very susceptible
E. coli
(Lys-447 and Ser-464) but are identical to those found in the less susceptible
Staphylococcus aureus
and
Streptococcus pneumoniae
. Peptide sequences of the QRDR of GyrA were identical in all the species, except for the amino acid at position 83, which was an alanine in the two less susceptible groups and a serine in the most susceptible one, as in
E. coli
, suggesting that this amino acid is involved in the observed differences of quinolone susceptibility within the
Mycobacterium
genus.
Identification of Novel Mutation Patterns in the
parC
Gene of Ciprofloxacin-Resistant Isolates of
Neisseria gonorrhoeae
Authors: Trees David L. , Sandul Amy L. , Whittington William L. , Knapp Joan S.
Published: October 2018

Of 65 ciprofloxacin-resistant, clinical isolates of
Neisseria gonorrhoeae
, 5 isolates exhibited ParC mutations previously undescribed in the gonococcus. For isolates containing two ParC mutations (the Ser-87→Ile and Glu-91→Gly mutations and the Gly-85→Cys and Arg116→Leu mutations) the MICs of ciprofloxacin (8.0 to 64.0 μg/ml) were higher than those for the isolate containing the single ParC mutation (Arg-116→Leu; MIC, 1.0 μg/ml).
Active Efflux of Norfloxacin by
Bacteroides fragilis
Authors: Miyamae Shin , Nikaido Hiroshi , Tanaka Yoshinobu , Yoshimura Fuminobu
Published: October 2018

Norfloxacin was actively pumped out by
Bacteroides fragilis
, which is intrinsically resistant to most fluoroquinolones. Reserpine moderately inhibited the efflux. A one-step spontaneous mutant had increased resistance to norfloxacin, ethidium bromide, and puromycin, a result suggesting that the efflux is catalyzed by a multidrug pump with specificity similar to that of NorA/Bmr.
Molecular Characterization of a TEM-21 β-Lactamase in a Clinical Isolate of
Morganella morganii
Authors: Tessier F. , Arpin C. , Allery A. , Quentin C.
Published: October 2018

A clinical isolate of
Morganella morganii
, with reduced susceptibility to expanded-spectrum cephalosporins and aztreonam, was found to produce an extended-spectrum β-lactamase with a pI of 6.4. The nucleotide sequence of the encoding gene was that of the gene encoding TEM-21. This is the first molecular characterization of an extended-spectrum β-lactamase in
M. morganii.
Inhibitor-Resistant OXY-2-Derived β-Lactamase Produced by
Klebsiella oxytoca
Authors: Sirot D. , Labia R. , Pouedras P. , Chanal-Claris C. , Cerceau C. , Sirot J.
Published: October 2018

Klebsiella oxytoca
strains are generally moderately resistant to amoxicillin and ticarcillin due to the activities of the chromosomally encoded OXY-1 and OXY-2 class A β-lactamase families. These enzymes have the ability to hydrolyze not only penicillins but also cephalosporins, including cefuroxime, ceftriaxone, and aztreonam, and are inhibited by clavulanic acid. A
Klebsiella oxytoca
strain was isolated from a culture of blood from a patient who had been treated with amoxicillin-clavulanate (3 g/day) for 10 days 1 month earlier. This strain harbored an unusual phenotype characterized by resistance to amoxicillin-clavulanate. It produced an OXY-2-type β-lactamase (pI 6.3), as confirmed by PCR amplification with primers specific for the OXY-2-encoding gene. Gene sequencing revealed a point mutation (A→G) corresponding to the amino acid substitution Ser→Gly at position 130. This mutant enzyme was poorly inhibited by inhibitors, and its kinetic constants compared to those of the parent enzyme were characterized by an increased

K
m

value for ticarcillin, with a drastically reduced activity against cephalosporins, as is observed with inhibitor-resistant TEM enzymes. The substitution Ser→Gly-130 was previously described in the inhibitor-resistant β-lactamase SHV-10 derived from an SHV-5 variant, but this is the first report of such a mutant in OXY enzymes from
K. oxytoca
.
Synergy of Nitric Oxide and Azoles against
Candida
Species In Vitro
Authors: McElhaney-Feser Gail E. , Raulli Robert E. , Cihlar Ronald L.
Published: October 2018

The candidacidal activity of nitric oxide (NO) as delivered by a class of compounds termed diazeniumdiolates has been investigated. Diazeniumdiolates are stable agents capable of releasing NO in a biologically usable form at a predicted rate, and three such compounds were examined for activity. One compound, (
Z
)-1-[
N
-(2-aminoethyl)-
N
-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NO), proved to be most suitable for examining NO activity due to its relatively long half-life (20 h) and because of limited candidacidal activity of the uncomplexed DETA nucleophile. DETA-NO was active against six species of
Candida
for which the MICs necessary to inhibit 50% growth (MIC
50
s) ranged from 0.25 to 1.0 mg/ml.
C. parapsilosis
and
C. krusei
were the most susceptible to the compound. In addition to a determination of NO effects alone, the complex was utilized to investigate the synergistic potential of released NO in combination with ketoconazole, fluconazole, and miconazole. Activity was investigated in vitro against representative strains of
Candida albicans
,
C. krusei
,
C. parapsilosis
,
C. tropicalis
,
C. glabrata
, and
C. dubliniensis
. Determination of MIC
50
, MIC
80
and MICs indicated that DETA-NO inhibits all strains tested, with strains of
C. parapsilosis
and
C. krusei
being consistently the most sensitive. The combination of DETA-NO with each azole was synergistic against all strains tested as measured by fractional inhibitory concentration indices that ranged from 0.1222 to 0.4583. The data suggest that DETA-NO or compounds with similar properties may be useful in the development of new therapeutic strategies for treatment of
Candida
infections.
In Vivo Activities of Amoxicillin and Amoxicillin-Clavulanate against
Streptococcus pneumoniae
: Application to Breakpoint Determinations
Authors: Andes D. , Craig W. A.
Published: October 2018

The in vivo activities of amoxicillin and amoxicillin-clavulanate against 17 strains of
Streptococcus pneumoniae
with penicillin MICs of 0.12–8.0 mg/liter were assessed in a cyclophosphamide-induced neutropenic murine thigh infection model. Renal impairment was produced by administration of uranyl nitrate to prolong the amoxicillin half-life in the mice from 21 to 65 min, simulating human pharmacokinetics. Two hours after thigh infection with 10
5
to 10
6
CFU, groups of mice were treated with 7 mg of amoxicillin per kg of body weight alone or combined with clavulanate (ratio, 4:1) every 8 h for 1 and 4 days. There was an excellent correlation between the MIC of amoxicillin (0.03 to 5.6 mg/liter) and (i) the change in log
10
CFU/thigh at 24 h and (ii) survival after 4 days of therapy. Organisms for which MICs were 2 mg/liter or less were killed at 1.4 to 4.2 and 1.6 to 4.1 log
10
CFU/thigh at 24 h by amoxicillin and amoxicillin-clavulanate, respectively. The four strains for which MICs were >4 mg/liter grew 0.2 to 2.6 and 0.6 to 2.3 logs at 24 h despite therapy with amoxicillin and amoxicillin-clavulanate, respectively. Infection was uniformly fatal by 72 h in untreated mice. Amoxicillin therapy resulted in no mortality with organisms for which MICs were 1 mg/liter or less, 20 to 40% mortality with organisms for which MICs were 2 mg/liter, and 80 to 100% mortality with organisms for which MICs were 4.0–5.6 mg/liter. Lower and higher doses (0.5, 2, and 20 mg/kg) of amoxicillin were studied against organisms for which MICs were near the breakpoint. These studies demonstrate that a reduction of 1 log
10
or greater in CFU/thigh at 24 h is consistently observed when amoxicillin levels exceed the MIC for 25 to 30% of the dosing interval. These studies would support amoxicillin (and amoxicillin-clavulanate) MIC breakpoints of 1 mg/liter for susceptible, 2 mg/liter for intermediate, and 4 mg/liter for resistant strains of
S. pneumoniae
.
Dynamics of Clarithromycin and Azithromycin Efficacies against ExperimentalHaemophilus influenzaePulmonary Infection
Authors: Alder J. D. , Ewing P. J. , Nilius A. M. , Mitten M. , Tovcimak A. , Oleksijew A. , Jarvis K. , Paige L. , Tanaka S. K. T.
Published: October 2018

The dynamics of clarithromycin and azithromycin efficacy against pulmonaryHaemophilus influenzaeinfection in rats were evaluated. Efficacy was measured by reduction in pulmonaryH. influenzaeburden on days 3 and 7 postinoculation. Clarithromycin therapy was effective on day 3 or 7 of therapy, while azithromycin was effective on day 7 but not on day 3 of therapy. Both macrolides produced marked efficacy against all six strains ofH. influenzaetested, including four strains for which MICs were above the susceptible breakpoint (8 μg/ml) concentration of clarithromycin. The two macrolides demonstrated markedly different pharmacokinetic characteristics, with clarithromycin present in both blood and tissue, while azithromycin was concentrated primarily in tissue. During pulmonary infection in rats,H. influenzaewas found in both intracellular locations and an extracellular location in the lung. Blood concentrations of clarithromycin and azithromycin approximated human pharmacokinetics, and the blood concentrations for either macrolide rarely exceeded MICs forH. influenzae. At dosages producing blood concentrations similar to values achieved clinically, clarithromycin produced efficacy on day 3 of therapy, while both clarithromycin and azithromycin were equally effective on day 7. The different dynamics of clarithromycin and azithromycin suggest that length of therapy should be considered as a key parameter in evaluations of drug efficacy.
Pharmacokinetics of Pentoxifylline and Its Metabolites in Healthy Mice and in Mice Infected with
Candida albicans
Authors: Miller Kenneth , Louie Arnold , Baltch Aldona L. , Smith Raymond P. , Davis Patrick J. , Gordon Morris A.
Published: October 2018

Pentoxifylline has immunomodulatory properties and has been shown to decrease organ damage and improve survival in animals with gram-negative sepsis or endotoxemia. This effect is mediated by a reduction in endotoxin-induced production of tumor necrosis factor alpha (TNF-α) by the host. In earlier studies, we observed an unexpected increase in mortality in mice infected with
Candida albicans
that were given pentoxifylline even though concentrations of TNF-α in serum were not affected. The current study was designed to determine whether the pharmacokinetics of pentoxifylline and its metabolites were altered in
C. albicans
-infected mice and, if so, whether these changes could have contributed to the increased mortality. Noninfected mice and mice infected with
C. albicans
were treated with pentoxifylline (60 mg/kg of body weight) intraperitoneally every 8 h. Serum was collected from animals after one (day 0), four (day 1), or seven (day 2) injections of pentoxifylline or saline (controls). The first dose was administered 6 h after
C. albicans
infection. Serum was pooled. Concentrations of pentoxifylline and metabolites I, IV, and V were determined by capillary gas chromatography. Renal function and hepatic profiles were assessed. Pharmacokinetic parameters (maximum concentration of pentoxifylline in serum, half-life, and area under the concentration-time curve from 0 h to infinity [AUC
0–∞
]) for all noninfected mice were similar and did not differ from those for day 0-infected mice. For day 1-infected mice, values of these three pharmacokinetic parameters for pentoxifylline and metabolite I were increased two- to fourfold over values for noninfected and day 0-infected mice. For metabolites IV and V, the AUC
0–∞
was increased approximately eightfold over control values. In addition, day 1-infected mice demonstrated evidence of renal and hepatic dysfunction. In summary,
C. albicans
infection produced marked changes in the pharmacokinetics of pentoxifylline and its metabolites in the mice. The high concentrations of pentoxifylline and its metabolites in serum attained in infected mice may have contributed to the increased mortality of mice with systemic candidiasis.
Single-Dose Pharmacokinetics of Meropenem during Continuous Venovenous Hemofiltration
Authors: Thalhammer Florian , Schenk Peter , Burgmann Heinz , El Menyawi Ibrahim , Hollenstein Ursula M. , Rosenkranz Alexander R. , Sunder-Plassmann Gere , Breyer Stefan , Ratheiser Klaus
Published: October 2018

The pharmacokinetic properties of meropenem were investigated in nine critically ill patients treated by continuous venovenous hemofiltration (CVVH). All patients received one dose of 1 g of meropenem intravenously. High-flux polysulfone membranes were used as dialyzers. Meropenem levels were measured in plasma and ultrafiltrate by high-performance liquid chromatography. The total body clearance and elimination half-life were 143.7 ± 18.6 ml/min and 2.46 ± 0.41 h, respectively. The post- to prehemofiltration ratio of meropenem was 0.24 ± 0.06. Peak plasma drug concentrations measured 60 min postinfusion were 28.1 ± 2.7 μg/ml, and trough levels after 6 h of CVVH were 6.6 ± 1.5 μg/ml. The calculated total daily meropenem requirement in these patients with acute renal failure and undergoing CVVH was 2,482 ± 321 mg. Based on these data, we conclude that patients with severe infections who are undergoing CVVH can be treated effectively with 1 g of meropenem every 8 h.
Susceptibilities of
Candida
Species Isolated from the Lower Gastrointestinal Tracts of High-Risk Patients to the New Semisynthetic Echinocandin LY303366 and Other Antifungal Agents
Authors: Zhanel George G. , Karlowsky James A. , Zelenitsky Sheryl A. , Turik Michael A. , Hoban Daryl J.
Published: October 2018

Fifty-two percent of stool specimens collected from 1,200 high-risk patients were colonized with yeasts, primarily
Candida albicans
(53.6%) and
Candida glabrata
(35.7%). Susceptibilities to all antifungal agents tested, including LY303366, were similar to those reported previously for
Candida
species isolated from blood.
Synergism between Poly-(1-6)-β-
d
-Glucopyranosyl-(1-3)-β
d
-Glucopyranose Glucan and Cefazolin in Prophylaxis of Staphylococcal Wound Infection in a Guinea Pig Model
Authors: Kaiser Allen B. , Kernodle Douglas S.
Published: October 2018

To determine whether the infection-preventing capability of the neutrophil-activating agent poly-(1-6)-β-
d
-glucopyranosyl-(1-3)-β-
d
-glucopyranose glucan (PGG-glucan) can be enhanced with antibiotic prophylaxis, we administered PGG-glucan and cefazolin, alone and in combination, to guinea pigs inoculated with isolates of staphylococci. Guinea pigs receiving both PGG-glucan and cefazolin had 50% infective doses that were 8- to 20-fold higher than those obtained with cefazolin alone and 100- to 200-fold higher than those obtained with PGG-glucan alone. PGG-glucan and cefazolin are synergistic in their ability to prevent staphylococcal wound infection.
Antimalarial Activities of Polyhydroxyphenyl and Hydroxamic Acid Derivatives
Authors: Holland Kevin P. , Elford Howard L. , Bracchi Valerie , Annis Charles G. , Schuster Sheldon M. , Chakrabarti Debopam
Published: October 2018

Several known mammalian ribonucleotide reductase inhibitors featuring a polyhydroxyphenyl and/or hydroxamate moiety as the active group were screened for potency in inhibiting growth of the malaria parasite
Plasmodium falciparum
. Compounds containing a 2,3- or 3,4-dihydroxyphenyl group as well as benzohydroxamate appear to be the most effective inhibitors of the malaria parasite.
Penetration of Oral Fluconazole into Gynecological Tissues
Authors: Mikamo Hiroshige , Kawazoe Kyoko , Sato Yasumasa , Izumi Koji , Ito Toshiya , Ito Kunihiko , Tamaya Teruhiko
Published: October 2018

Penetration of fluconazole into female genital tissues was examined. Fluconazole was administered orally at a dose of 150 mg to patients undergoing total abdominal hysterectomy 1 to 151 h prior to surgery. During surgery, blood, uterus, ovary, and oviduct were sampled. Fluconazole concentrations in each tissue were determined by high-performance liquid chromatography. The peak concentrations in serum reached approximately 6.1 μg/ml 1.0 h after a drip infusion was begun. At each time after the infusion, the concentrations in portio vaginalis, cervix uteri, myometrium, endometrium, ovary, and oviduct were higher than those in the serum: the peaks in the tissues ranged from 6.4 to 9.5 μg/g around 1.0 h after the drip infusion was begun. Thus, the levels of penentration of fluconazole into gynecological tissues appeared to be similar to or slightly above those in serum samples. Fluconazole can rapidly penetrate from plasma into the female genital organs, supporting high efficacy of fluconazole against fungal infections in the field of gynecology.
Targeting the Shikimate Pathway in the Malaria Parasite
Plasmodium falciparum
Authors: McConkey Glenn A.
Published: October 2018

The shikimate pathway presents an attractive target for malaria chemotherapy. Three shikimic acid analogs exhibited different effects on
Plasmodium falciparum
growth. (6
R
)-6-Fluoro-shikimate and (6
S
)-6-fluoro-shikimate inhibited growth (50% inhibitory concentrations, 1.5 × 10
−5
and 2.7 × 10
−4
M, respectively), whereas 2-fluoro-shikimate had no effect.
para
-Aminobenzoic acid abrogated the inhibition, demonstrating that the shikimate pathway was specifically targeted.
Development of Rifapentine Susceptibility Tests for
Mycobacterium tuberculosis
Authors: Heifets L. , Sanchez T. , Vanderkolk J. , Pham V.
Published: October 2018

Two methods for testing the susceptibility of
Mycobacterium tuberculosis
to rifapentine have been developed: the agar proportion method and the radiometric BACTEC technique. A critical concentration of 0.5 μg of rifapentine per ml is proposed for both methods since it provides a reliable means of distinguishing between susceptible and resistant
M. tuberculosis
isolates. It is recommended that two quality control
M. tuberculosis
strains be used at the introduction of these tests in a clinical laboratory: one that is pansusceptible (H37Rv) and one that is resistant to rifapentine. The resistant strain can be obtained from the American Type Culture Collection, where it is deposited under the number ATCC 700457.
Characterization of Mutations in the
rpoB
Gene in Naturally Rifampin-Resistant
Rickettsia
Species
Authors: Drancourt Michel , Raoult Didier
Published: October 2018

Rickettsiae are gram-negative, obligately intracellular bacteria responsible for arthropod-borne spotted fevers and typhus. Experimental studies have delineated a cluster of naturally rifampin-resistant spotted fever group species. We sequenced the 4,122- to 4,125-bp RNA polymerase β-subunit-encoding gene (
rpoB
) from typhus and spotted fever group representatives and obtained partial sequences for all naturally rifampin-resistant species. A single point mutation resulting in a phenylalanine-to-leucine change at position 973 of the
Rickettsia conorii rpoB
sequence and present in all the rifampin-resistant species was absent in all the rifampin-susceptible species.
rpoB
-based phylogenetic relationships among these rickettsial species yielded topologies which were in accordance with previously published phylogenies.