bluuebunny/crossref_metadata_2025 huggingface dataset:
New pharmacokinetic in vitro model for studies of antibiotic activity against intracellular microorganisms
Authors: Hultén K , Rigo R , Gustafsson I , Engstrand L
Published: October 2018

The capacity for intracellular growth is an important survival strategy for a large group of common pathogens. Helicobacter pylori, the etiological agent for gastritis and duodenal ulcer, has been shown by both in vivo and in vitro studies to have the capacity to invade epithelial cells. In vitro models are used to study the effect of antibiotics on microoganisms. Most investigations are performed in broth culture or on agar plates, but kinetic models for bacteria in broth have been described. We present a new, kinetic model adapted for intracellular pathogens. A glass chamber, with a metal rack fitting Falcon cell culture inserts, was connected to a pump by rubber tubes. Different tube diameters and pump speeds were evaluated, and the assay was designed to mimic the half-lives of the antibiotics in vivo, i.e., 11.5 h for azithromycin, 5 h for clarithromycin, and 1 h for amoxicillin. Monolayers of HEp-2 cells were grown in the inserts for 2 days, after which H. pylori (clinical strain 88-23), was added to the system. Internalization was allowed for 12 h, and extracellular H. pylori cells were eradicated with gentamicin. The inserts were moved to the glass chamber, containing medium with 12.5 mg of either amoxicillin or azithromycin per liter or 2.4 mg of clarithromycin per liter. This represents 12.5, 50, and 80 times the extracellular minimum bactericidal concentration value, respectively. Samples were taken at 0, 2, 4, 6, 8, and 24 h. The HEp-2 cells were lysed, and intracellular bacteria were counted by plating. Inserts with infected cells grown in drug-free medium were included as controls for each time interval. A 3-log10 reduction of H. pylori was achieved in the experiments with azithromycin, and a 4-log10 reduction was achieved in the clarithromycin experiments, while no intracellular effect was seen when amoxicillin was used. The antibiotic concentrations at the sampling intervals were 12.5, 3.1, 0.8, 0.2, 0.05, and 0 mg/liter for amoxicillin; 12.5, 11.5, 10, 9, 8, and 3 mg/liter for azithromycin; and 2.4, 1.8, 1.4, 1, 0.8, and 0 mg/liter for clarithromycin. This new model for pharmacokinetic studies provides a useful tool, with applications for a broad range of microorganisms.
In vitro and in vivo inhibition of erythrocytic development of malarial parasites by docetaxel
Authors: Sinou V , Grellier P , Schrevel J
Published: October 2018

The stage-dependent susceptibility of Plasmodium falciparum to a short exposure to docetaxel (Taxotere) was evaluated by subjecting ring-infected, trophozoite-infected, and schizont-infected erythrocytes to a 5-h exposure to various concentrations of the drug. The schizont stage was shown to be the most sensitive stage; an inhibition of more than 60% of parasite development was observed at 10 nM. At this drug concentration, the development of the younger ring and trophozoite forms was unaffected. The in vivo antimalarial activity of docetaxel against the development in blood of old trophozoites of a species that causes malaria in rodents, Plasmodium vinckei petteri, was evaluated in IOPS-OF1 mice. Two tests were performed: the 4-day suppressive test, as described by Peters (W. Peters, p. 145-273, in Chemotherapy, and Drug Resistance in Malaria, vol. 1, 1987), and the effects of a single injection of docetaxel after inoculation of the parasites. A single injection of docetaxel at 40 mg/kg of body weight was sufficient to reduce drastically the level of parasitemia; 90% inhibition of the development of parasites in blood was observed 5 days after drug injection. This program avoided the toxicity observed when mice were treated with four injections of docetaxel. The possibility of using a single bolus of taxoids to treat malaria infections is discussed.
The guanine nucleoside analog penciclovir is active against chronic duck hepatitis B virus infection in vivo
Authors: Lin E , Luscombe C , Wang Y Y , Shaw T , Locarnini S
Published: October 2018

Ducks congenitally infected with duck hepatitis B virus (HBV) were treated with the antiviral guanine nucleoside analog penciclovir for 4 weeks at a dose of 10 mg/kg of body weight per day. The effects of treatment on viremia and intrahepatic viral genome replication, transcription, and translation were examined. In seven of eight penciclovir-treated ducks, viremia was barely detectable after a week of treatment. After 4 weeks of treatment, molecular hybridization studies showed that intrahepatic viral DNA, RNA, and protein levels were significantly reduced compared with those in placebo-treated controls. Synthesis of all viral replicative intermediates, including the normally persistent viral supercoiled DNA species, was inhibited by penciclovir treatment. Examination of liver tissue sections after in situ DNA hybridization or immunohistochemical staining confirmed that viral DNA and protein synthesis had been profoundly inhibited in most hepatic parenchymal cells. However, small subpopulations of cells, in particular the small bile duct epithelial cells, remained strongly positive for duck HBV antigens and DNA despite treatment. There was no evidence of toxicity associated with penciclovir therapy. This study confirms the safety and potent antihepadnaviral activity of penciclovir in vivo but indicates that further improvements in antiviral therapy will be required to completely eliminate HBV infection.
Some repair-deficient mutants of Dictyostelium discoideum display enhanced susceptibilities to bleomycin
Authors: Deering R A , Guyer R B , Stevens L , Watson-Thais T E
Published: October 2018

Dictyostelium discoideum, a soil eukaryote, is highly resistant to DNA-damaging agents; repair mutants are more susceptible. Susceptibility to bleomycin, produced by Streptomyces verticillus, is greater for mutants which are susceptible to other agents than for resistant strains. The high potential for DNA repair may result from the need to cope with chemicals produced by other soil microorganisms.
Selective cytotoxicity of ricin A chain immunotoxins towards murine cytomegalovirus-infected cells
Authors: Barnett B B , Smee D F , Malek S M , Sidwell R W
Published: October 2018

Immunotoxins were constructed by linking immunoglobulins specific for murine cytomegalovirus (MCMV) to deglycosylated ricin A chain. Toxicities toward MCMV-infected and uninfected cells were determined by measuring the inhibition of protein synthesis following a 48-h exposure to immunotoxins commencing 24 h after infection. The 50% inhibitory concentrations ranged from 0.4 to 4 micrograms/ml for infected cells and from 22 to 120 micrograms/ml for uninfected cells. Selectivity indices ranged from 30 to 157. Control immunotoxins, which were constructed identically except that the immunoglobulin moiety had no specificity toward MCMV antigens, had 50% inhibitory concentrations of 50 and 100 micrograms/ml toward infected and uninfected cells, respectively.
Mutations in 23S rRNA are associated with clarithromycin resistance in Helicobacter pylori
Authors: Versalovic J , Shortridge D , Kibler K , Griffy M V , Beyer J , Flamm R K , Tanaka S K , Graham D Y , Go M F
Published: October 2018

Twelve clarithromycin-resistant Helicobacter pylori isolates (100% of resistant isolates examined) from seven different patients each contained an A-->G transition mutation within a conserved loop of 23S rRNA. A-->G transition mutations at positions cognate with Escherichia coli 23S rRNA positions 2058 and 2059 were identified. Clarithromycin-susceptible H. pylori isolates from 14 different patients displayed no polymorphisms in a conserved loop within domain V of 23S rRNA. The study is the first to report mutations in H. pylori associated with resistance to an antimicrobial agent used in established peptic ulcer treatment regimens.
Investigation of bioequivalence and tolerability of intramuscular ceftriaxone injections by using 1% lidocaine, buffered lidocaine, and sterile water diluents
Authors: Hayward C J , Nafziger A N , Kohlhepp S J , Bertino J S
Published: October 2018

The pharmacokinetics and tolerability of 1-g doses of ceftriaxone diluted in sterile water, 1% lidocaine, or buffered lidocaine were investigated. No difference in bioequivalence was noted between the three treatments. No difference in peak creatine kinase values was seen. By use of a quantitative pain scale, injection of ceftriaxone with the water diluent was significantly more painful than that with either of the other two diluents. No difference in injection pain was noted for lidocaine or buffered lidocaine.
In vitro potency of inhibition by antiviral drugs of hematopoietic progenitor colony formation correlates with exposure at hemotoxic levels in human immunodeficiency virus-positive humans
Authors: Dornsife R E , Averett D R
Published: October 2018

Inhibition of in vitro colony formation of human hematopoietic progenitors (CFU-granulocyte-macrophage, burst-forming unit-erythroid) by the antiviral nucleoside drugs alovudine, zalcitabine, zidovudine, ganciclovir, stavudine, didanosine, lamivudine, and acyclovir was measured. Significant correlations between in vitro 50% inhibitory concentrations and the daily human exposures (area under the concentration-time curve from 0 to 24 h; in micromolar.hour) of these chronically administered drugs in human immunodeficiency virus-positive patients that induced neutropenia or anemia were demonstrated by both linear regression and Spearman rank-order analyses. These quantitative correlations allow estimation of the exposure at which bone marrow toxicity may occur with candidate compounds.
The macrolide-lincosamide-streptogramin B resistance phenotypes characterized by using a specifically deleted, antibiotic-sensitive strain of Streptomyces lividans
Authors: Pernodet J L , Fish S , Blondelet-Rouault M H , Cundliffe E
Published: October 2018

Genes conferring resistance to macrolide, lincosamide, and streptogramin B (MLS) antibiotics via ribosomal modification are widespread in bacteria, including clinical isolates and MLS-producing actinomycetes. Such erm-type genes encode enzymes that mono- or dimethylate residue A-2058 of 23S rRNA. The different phenotypes resulting from monomethylation (MLS-I phenotype, conferred by erm type I genes) or dimethylation (MLS-II phenotype due to erm type II genes) have been characterized by introducing tlrD or ermE, respectively, into an MLS-sensitive derivative of Streptomyces lividans TK21. This strain (designated OS456) was generated by specific replacement of the endogenous resistance genes lrm and mgt. The MLS-I phenotype is characterized by high-level resistance to lincomycin with only marginal resistance to macrolides such as chalcomycin or tylosin, whereas the MLS-II phenotype involves high-level resistance to all MLS drugs. Mono- and dimethylated ribosomes were introduced into a cell-free protein-synthesizing system prepared from S. lividans and compared with unmodified particles in their response to antibiotics. There was no simple correlation between the relative potencies of MLS drugs at the level of the target site (i.e., the ribosome) and their antibacterial activities expressed as MICs.
Antituberculosis activities of clofazimine and its new analogs B4154 and B4157
Authors: Reddy V M , Nadadhur G , Daneluzzi D , O'Sullivan J F , Gangadharam P R
Published: October 2018

In our efforts to develop new drugs for the treatment of tuberculosis, especially that caused by multidrug-resistant strains, we investigated clofazimine (CFM) and two of its analogs, B4154 and B4157, for their antituberculosis activities. Twenty M. tuberculosis strains were tested, including 16 drug-resistant strains (strains resistant to one or more antituberculosis drugs), for their susceptibilities to these three agents. All of the strains were found to be susceptible to B4154 and B4157, and one strain showed moderate resistance to CFM. The MICs of B4154, B4157, and CFM at which 90% of strains were inhibited were 0.25, 0.12, and < or = 1.0 microgram/ml, respectively. The intracellular activities of CFM and B4157 were superior to that of B4154. The chemotherapeutic activities of the three compounds were evaluated in C57BL/6 mice. At a dose of 20 mg/kg of body weight, the activity of CFM was slightly superior to that of B4157; however, both compounds prevented mortality and caused a significant reduction in the numbers of CFU in the lungs and spleens. The animals treated with B4157 showed less pigmentation than animals treated with CFM. The chemotherapeutic activity of CFM was comparable to those of rifampin and isoniazid. Complete susceptibility of multidrug-resistant strains to CFM and B4157 and the therapeutic efficacies of these compounds against mouse tuberculosis make these drugs attractive agents for the treatment of drug-resistant tuberculosis.
Effect of mitonafide analogs on topoisomerase II of Leishmania chagasi
Authors: Slunt K M , Grace J M , Macdonald T L , Pearson R D
Published: October 2018

Mitonafide (4-nitro-benzoisoquinolinedione) and a number of structural analogs were synthesized and studied in order to determine the structural requirements for inhibition of leishmanial nuclear and kinetoplast topoisomerase II and human topoisomerase II. The structure-activity relationship studies with the mitonafide analogs demonstrated that there was selective targeting of leishmanial nuclear topoisomerase II and human topoisomerase II and differential targeting of kinetoplast over nuclear topoisomerase II in the parasite. Mitonafide analogs appeared to have multiple mechanisms of action leading to death of leishmanias, but several compounds that affected kinetoplast but not nuclear topoisomerase II were not cytotoxic as determined by short-term assays. These studies provide new insight into the differential sensitivities of leishmanial nuclear and kinetoplast topoisomerase II to topoisomerase II-targeting drugs.
Uptake and intracellular activity of NM394, a new quinolone, in human polymorphonuclear leukocytes
Authors: Ozaki M , Komori K , Matsuda M , Yamaguchi R , Honmura T , Tomii Y , Nishimura I , Nishino T
Published: October 2018

The uptake of NM394, a new quinolone, by and its subsequent elution from human polymorphonuclear leukocytes were studied and compared with those of ofloxacin and ciprofloxacin. The kinetics of the uptake of NM394 was similar to that of ciprofloxacin. The maximum intracellular-to-extracellular concentration ratio was 12.3, compared with 8.6 for ciprofloxacin and 4.9 for ofloxacin at the extracellular concentration of 20 micrograms/ml. The elution of NM394 from human polymorphonuclear leukocytes occurs relatively slowly; 5 min after the removal of extracellular NM394, nearly 100% still remained in polymorphonuclear leukocytes, compared with ofloxacin, which was so rapidly eluted that only 12% remained. The uptake of NM394 was significantly decreased at 4 degrees C and by the presence of NaCN but was not affected by the presence of L-glycine, L-leucine, L-serine, adenosine, or NaF. NM394 showed intracellular activity at a concentration of 0.1 microgram/ml that significantly reduced the number of phagocytosed Pseudomonas aeruginosa cells with 2 h of incubation. These results suggest that uptake of NM394 by human polymorphonuclear leukocytes occurs via an active transport system differing from that of ofloxacin, whose uptake is affected by the presence of L-glycine and L-leucine, and that once accumulated, NM394 remains intracellularly active and participates in protection against bacterial infection.
Didanosine reduces atevirdine absorption in subjects with human immunodeficiency virus infections
Authors: Morse G D , Fischl M A , Shelton M J , Borin M T , Driver M R , DeRemer M , Lee K , Wajszczuk C P
Published: October 2018

Atevirdine is a nonnucleoside reverse transcriptase inhibitor with in vitro activity against human immunodeficiency virus type 1 and is currently in phase II clinical trials. Atevirdine is most soluble at a pH of < 2, and therefore, normal gastric acidity is most likely necessary for optimal bioavailability. Because of the rapid development of resistance in vitro, atevirdine is being evaluated in combination with didanosine and/or zidovudine in both two- and three-drug combination regimens. To examine the influence of concurrent didanosine (buffered tablet formulation) on the disposition of atevirdine, 12 human immunodeficiency virus type 1-infected subjects (mean CD4+ cell count, 199 cells per mm3; range, 13 to 447 cells/mm3) participated in a three-way, partially randomized, crossover, single-dose study to evaluate the pharmacokinetics of didanosine and atevirdine when each drug was given alone (treatments A and B, respectively) versus concurrently (treatment C). Concurrent administration of didanosine and atevirdine significantly reduced the maximum concentration of atevirdine in serum from 3.45 +/- 2.8 to 0.854 +/- 0.33 microM (P = 0.004). Likewise, the mean atevirdine area under the concentration-time curve from 0 to 24 h after administration of the combination was reduced to 6.47 +/- 2.2 microM.h (P = 0.004) relative to a value of 11.3 +/- 4.8 microM.h for atevirdine alone. Atevirdine had no statistically significant effect on the pharmacokinetic parameters of didanosine. Concurrent administration of single doses of atevirdine and didanosine resulted in a markedly lower maximum concentration of atevirdine in serum and area under the concentration-time curve, with a minimal effect on the disposition of didanosine. It is unknown whether an interaction of similar magnitude would occur under steady-state conditions; thus, combination regimens which include both atevirdine and didanosine should be designed so that their administration times are separated. Since the duration of the buffering effect of didanosine formulations is unknown, atevirdine should be given prior to didanosine.
Pharmacokinetics of sparfloxacin and serum bactericidal activity against pneumococci
Authors: Trautmann M , Ruhnke M , Borner K , Wagner J , Koeppe P
Published: October 2018

Sparfloxacin, a new fluorinated quinolone, exhibits higher in vitro activity against pneumococci than do ciprofloxacin and ofloxacin. Since up to 30% of cases of pneumococcal pneumonia are associated with bacteremia, and since an increasing percentage of pneumococci are resistant against penicillin, we studied the serum bactericidal activity of sparfloxacin against pneumococci in eight healthy, middle-aged volunteers. Pharmacokinetics in serum and urine after a 400-mg oral dose of sparfloxacin were comparable to those described by other authors. Inhibitory and bactericidal activities in serum were measured for four pneumococcal isolates representing penicillin-susceptible (one isolate), intermediately resistant (two isolates), and highly resistant (one isolate) strains. Geometric mean inhibitory titers ranged between 1:2.4 and 1:6.3 and bactericidal titers ranged between 1:1.3 and 1:3.6 during a time period of 1 to 6 h after drug intake. Although such titers were not sufficient to predict a clinical response based on previous pharmacodynamic studies using quinolone antibiotics, data obtained with volunteers may only partially reflect the clinical situation in which a rise of humoral antibodies directed against pneumococcal antigens may help to reinforce the bactericidal action of the antibiotic.
Alteration of postantibiotic effect during one dosing interval of tobramycin, simulated in an in vitro pharmacokinetic model
Authors: den Hollander J G , Mouton J W , van Goor M P , Vleggaar F P , Verbrugh H A
Published: October 2018

The kinetics of the postantibiotic effect (PAE) during one dosing interval of tobramycin against Staphylococcus aureus and Pseudomonas aeruginosa was investigated. We determined the PAE at different time points during this dosing interval of 12 h in an in vitro pharmacokinetic model simulating human pharmacokinetics in which the half-life of tobramycin was adjusted to 2.4 +/- 0.2 h. Using an enzymatic method to inactivate tobramycin, we determined PAEs in samples extracted from the model at 1, 5, 8, and 12 h, corresponding with tobramycin concentrations of 20, 5, 2, and 1 times the MIC for the test organism. The PAE decreased significantly from 2.5 h at 1 h to 0 h at 12 h. No change in MIC was observed for the strains during the experiments. We conclude that the PAE decreases with decreasing tobramycin concentrations during a 12-h dosing interval and completely disappears after the concentration has reached the MIC for the test organism. On the basis of these observations, the emphasis that is placed on the PAE in discussions about the optimal dosing interval in aminoglycoside therapy is questionable.
Mutations in gyrA gene of quinolone-resistant Salmonella serotypes isolated from humans and animals
Authors: Griggs D J , Gensberg K , Piddock L J
Published: October 2018

The quinolone resistance-determining regions (QRDRs) of the gyrA genes of quinolone-resistant clinical and veterinary salmonella isolates were sequenced. Substitutions analogous to a substitution of a Ser to a Phe at position 83 (Ser83-->Phe) and Asp87-->Gly or Tyr in Escherichia coli were found, as was a single novel mutation outside of the QRDR resulting in Ala119-->Glu. The data suggest that gyrA mutations are associated with quinolone resistance in veterinary and clinical salmonella isolates and that the limits of the QRDR may require revision.
Differential regulation of the mcb and emr operons of Escherichia coli: role of mcb in multidrug resistance
Authors: Lomovskaya O , Kawai F , Matin A
Published: October 2018

The mcb operon (which is responsible for microcin B17 production) and the emr operon (which encodes a multidrug resistance pump) share a common negative regulator, EmrR. Nevertheless, compounds that induce the emr operon repress the mcb operon. The pump dedicated to microcin B17 extrusion can also protect the calls against sparfloxacin and other toxic compounds.
Activity of nitric oxide-generating compounds against encephalomyocarditis virus
Authors: Guillemard E , Geniteau-Legendre M , Kergot R , Lemaire G , Petit J F , Labarre C , Quero A M
Published: October 2018

Nitric oxide (NO) generated by two NO donors (sodium nitroprusside or S-nitroso-L-glutathione) was shown to exert a dose-dependent inhibition of encephalomyocarditis virus growth in L-929 cells. This activity was not due to the cytotoxic or direct virucidal effects of NO donors. L-929 cells were shown to produce NO endogenously, but this low level of production did not counter encephalomyocarditis virus replication.
Penicillin-binding proteins 2b and 2x of Streptococcus pneumoniae are primary resistance determinants for different classes of beta-lactam antibiotics
Authors: Grebe T , Hakenbeck R
Published: October 2018

High-level resistance to beta-lactam antibiotics in Streptococcus pneumoniae is mediated by successive alterations in essential penicillin-binding proteins (PBPs). In the present work, single amino acid changes in S. pneumoniae PBP 2x and PBP 2b that result in reduced affinity for the antibiotic and that confer first-level beta-lactam resistance are defined. Point mutations in the PBP genes were generated by PCR-derived mutagenesis. Those conferring maximal resistance to either cefotaxime (pbp2x) or piperacillin (pbp2b) were obtained after transformation of the susceptible laboratory strain R6 with the PCR-amplified PBP genes and selection on agar with various concentrations of the antibiotic. In the case of PBP 2x, transformants for which the cefotaxime MIC was 0.16 microgram/ml contained the substitution of a Thr for an Ala at position 550 (Thr550-->Ala), close to the PBP homology box Lys547SerGly, a mutation frequently observed in laboratory mutants and in a high-level cefotaxime-resistant clinical isolate as well. After further selection, transformants resisting 0.3 microgram of cefotaxime per ml were obtained; they contained the substitution Gly550 as the result of two mutations in the same codon. In PBP 2b, Thr446-->Ala, adjacent to another homology box Ser443SerAsn, was the mutation selected with piperacillin. This substitution has been described in all clinical isolates with a low-affinity PBP 2b but was distinct from point mutations found in laboratory mutants. Both pbp2b with the single mutation and a mosaic pbp2b of a clinical isolate conferred a twofold increase in piperacillin resistance. Attempts to select PBP 2b variants at higher piperacillin concentrations were unsuccessful. The mutated PBP 2b also markedly reduced the lytic response to piperacillin, suggesting that such a mutation is an important step in resistance development in clinical isolates.
Selection and characterization of a mutant of feline immunodeficiency virus resistant to 2',3'-dideoxycytidine
Authors: Medlin H K , Zhu Y Q , Remington K M , Phillips T R , North T W
Published: October 2018

We have selected and plaque purified a mutant of feline immunodeficiency virus (FIV) that is resistant to 2',3'-dideoxycytidine (ddC). This mutant was selected in cultured cells in the continuous presence of 25 microM ddC. The mutant, designated DCR-5c, was fourfold resistant to ddC, threefold resistant to 2',3'-dideoxyinosine, and more than fourfold resistant to phosphonoformic acid. DCR-5c displayed little or no resistance to (-)-beta-2',3'-dideoxy-3'-thiacytidine, 3'-azido-3'-deoxythymidine, or 9-(2-phosphonylmethoxyethyl) adenine. Reverse transcriptase purified from DCR-5c was less susceptible to inhibition by ddCTP, phosphonoformic acid, ddATP, or azido-dTTP than the wild-type FIV reverse transcriptase. Sequence analysis of DCR-5c revealed a single base change (G to C at nucleotide 2342) in the reverse transcriptase-encoding region of FIV. This mutation results in substitution of His for Asp at codon 3 of FIV reverse transcriptase. The role of this mutation in ddC resistance was confirmed by site-directed mutagenesis.
Monodrug efficacies of sulfonamides in prophylaxis for Pneumocystis carinii pneumonia
Authors: Hughes W T , Killmar J
Published: October 2018

A remarkably high rate of adverse events is associated with the use of trimethoprim-sulfamethoxazole in patients with human immunodeficiency virus type 1 infection. We examined the efficacies of sulfonamides alone in the prevention of Pneumocystis carinii pneumonitis, with the assumption that at least some of the adverse events with the drug combination might be due to trimethoprim. With the immunosuppressed rat model, eight sulfonamides were studied at 100, 10, and 1.0 mg/kg/day (10 rats per dosage and drug). P. carinii infection was prevented in all animals (100%) receiving dosages of as little as 1.0 mg of sulfamethoxazole, sulfamethoxypyridazine, and sulfadimethoxine per kg per day, as little as 10 mg of sulfameter, sulfachlorpyridazine, and sulfaquinoxaline per kg per day; and 100 mg of sulfaguanidine and sulfanilamide per kg per day. These studies suggest that a sulfonamide, such as sulfamethoxazole, might provide effective prophylaxis for P. carinii pneumonitis without trimethoprim.
Population pharmacokinetics of ceftazidime in cystic fibrosis patients analyzed by using a nonparametric algorithm and optimal sampling strategy
Authors: Vinks A A , Mouton J W , Touw D J , Heijerman H G , Danhof M , Bakker W
Published: October 2018

Postinfusion data obtained from 17 patients with cystic fibrosis participating in two clinical trials were used to develop population models for ceftazidime pharmacokinetics during continuous infusion. Determinant (D)-optimal sampling strategy (OSS) was used to evaluate the benefits of merging four maximally informative sampling times with population modeling. Full and sparse D-optimal sampling data sets were analyzed with the nonparametric expectation maximization (NPEM) algorithm and compared with the model obtained by the traditional standard two-stage approach. Individual pharmacokinetic parameter estimates were calculated by weighted nonlinear least-squares regression and by maximum a posteriori probability Bayesian estimator. Individual parameter estimates obtained with four D-optimally timed serum samples (OSS4) showed excellent correlation with parameter estimates obtained by using full data sets. The parameters of interest, clearance and volume of distribution, showed excellent agreement (R2 = 0.89 and R2 = 0.86). The ceftazidime population models were described as two-compartment kslope models, relating elimination constants to renal function. The NPEM-OSS4 model was described by the equations kel = 0.06516+ (0.00708.CLCR) and V1 = 0.1773 +/- 0.0406 liter/kg where CLCR is creatinine clearance in milliliters per minute per 1.73 m2, V1 is the volume of distribution of the central compartment, and kel is the elimination rate constant. Predictive performance evaluation for 31 patients with data which were not part of the model data sets showed that the NPEM-ALL model performed best, with significantly better precision than that of the standard two-stage model (P < 0.001). Predictions with the NPEM-OSS4 model were as precise as those with the NPEM-ALL model but slightly biased (-2.2 mg/liter; P < 0.01). D-optimal monitoring strategies coupled with population modeling results in useful and cost-effective population models and will be of advantage in clinical practice, as it allows pharmacokinetic-pharmacodynamic modeling with sparse data, thus describing the relationship between ceftazidime exposure and response in the treatment of acute exacerbations in patients with cystic fibrosis.
Concentrations of doxycycline and penicillin G in sera and cerebrospinal fluid of patients treated for neuroborreliosis
Authors: Karlsson M , Hammers S , Nilsson-Ehle I , Malmborg A S , Wretlind B
Published: October 2018

Concentrations of doxycycline and penicillin G in serum and cerebrospinal fluid (CSF) were analyzed in 46 patients during treatment for neuroborreliosis. Twenty patients were treated intravenously with penicillin G at 3 g every 6 h (q6h), and 26 patients were treated orally with doxycycline at 200 mg q24h. All samples were collected on day 13 of treatment. The median concentrations of penicillin G in serum were 0.5, 37, and 5.6 micrograms/ml before and 1 and 3 h after drug administration, and that in CSF was 0.5 (range, 0.3 to 1.6) microgram/ml after 2 to 3 h. The median concentrations of doxycycline in serum were 2.1, 6.1, and 4.7 micrograms/ml before and 2 and 6 h after drug administration, and that in CSF was 0.6 (range, 0.4 to 2.5) microgram/ml after 4 h. All patients had concentrations of penicillin G or doxycycline in CSF above the lowest reported MICs of penicillin G (0.003 microgram/ml) and doxycycline (0.12 microgram/ml) for Borrelia burgdorferi. However, no patients had a drug concentration in CSF above the highest reported MIC of penicillin G (8 micrograms/ml), and only one had a drug concentration in CSF above the highest reported MIC of doxycycline (2 micrograms/ml), despite good clinical response to treatment. No treatment failure or relapse was observed during a 1-year follow-up, although one patient treated with penicillin G and one treated with doxycycline were retreated because of residual pain. The chosen dosages of penicillin G and doxycycline seem to give sufficient concentrations in serum and CSF for the treatment of neuroborreliosis.
Protein binding of clindamycin in sera of patients with AIDS
Authors: Flaherty J F , Gatti G , White J , Bubp J , Borin M , Gambertoglio J G
Published: October 2018

Patients with AIDS have altered pharmacokinetics of clindamycin compared with those of healthy control subjects. In an attempt to better understand these differences, we undertook a study of protein binding of clindamycin in sera of patients with AIDS. Fifteen patients with AIDS and 15 healthy volunteers were given a single 600-mg dose of clindamycin orally and intravenously, and serum samples were collected at three time points corresponding to high, midpoint, and low clindamycin concentrations. Protein binding was determined by ultrafiltration, and total and unbound clindamycin concentrations were measured with a gas chromatography assay. AIDS patients had alpha 1-acid glycoprotein values approximately twice those of healthy volunteers (mean +/- standard deviation, 103 +/- 27 versus 61 +/- 11 mg/dl; P = 0.001). Overall, serum protein binding levels were higher in AIDS patients (mean +/- standard deviation, 83 +/- 7 versus 78% +/- 8%; P = 0.0001), which is likely the result of increased alpha 1-acid glycoprotein levels in these patients. Total concentrations of clindamycin in plasma were significantly higher in AIDS patients at most time points studied, while unbound serum clindamycin concentrations did not differ among the groups at each sampling time after both oral and intravenous dosing. Increased protein binding may partly explain the altered pharmacokinetic disposition of clindamycin in AIDS patients; however, other factors cannot be excluded.
Effect of polyaspartic acid on pharmacokinetics of gentamicin after single intravenous dose in the dog
Authors: Whittem T , Parton K , Turner K
Published: October 2018

The effects of poly-L-aspartic acid on the pharmacokinetics of gentamicin were examined by using a randomized crossover trial design with the dog. When analyzed according to a three-compartment open model, poly-L-aspartic acid reduced some first-order rate equation constants (A3, lambda 1, and lambda 3), the deep peripheral compartment exit microconstant (k31), the elimination rate constant (k(el)), and the area under the concentration-time curve from 0 to 480 h (AUC0-480) (0.21-, 0.60-, 0.26-, 0.27-, 0.72-, and 0.76-fold, respectively; P < 0.05) but increased the volume of distribution at steady state (Vss), the volume of distribution calculated by the area method (V(area)), the apparent volume of the peripheral compartment (Vp), and all mean time parameters. These results suggested that poly-L-aspartic acid increased the distribution of gentamicin to or binding within the deep peripheral compartment and that poly-L-aspartic acid may have delayed gentamicin transit through the peripheral tissues. In contrast, poly-L-aspartic acid did not alter pharmacokinetic parameters relevant to the central or shallow peripheral compartments to a clinically significant extent. Although gentamicin's pharmacokinetic parameters of relevance to therapeutic drug monitoring were not directly altered, this study has provided pharmacokinetic evidence that poly-L-aspartic acid alters the peripheral distribution of gentamicin. This pharmacokinetic interaction occurred after a single intravenous dose of each drug. Therefore, this interaction should be investigated further, before polyaspartic acid can be considered for use as a clinical nephroprotectant.
Population pharmacokinetic study of teicoplanin in severely neutropenic patients
Authors: Lortholary O , Tod M , Rizzo N , Padoin C , Biard O , Casassus P , Guillevin L , Petitjean O
Published: October 2018

The teicoplanin pharmacokinetics (PK) of 30 febrile and severely neutropenic patients (polymorphonuclear count, < 500/mm3) with hematologic malignancies were compared with those determined for five healthy volunteers (HV). Neutropenic patients were given piperacillin combined with amikacin, and teicoplanin was added to the regimen the day fever developed in patients suspected of having a staphylococcal infection or 48 h later. Teicoplanin was given intravenously at a dosage of 6 mg/kg of body weight at 0, 12, and 24 h and once a day thereafter. Five to eleven blood samples per patient were collected. Teicoplanin concentrations were measured by liquid chromatography. A bicompartmental model was fitted to the data by a nonlinear mixed-effect-model approach. Multiple-linear regression analysis was applied in an attempt to correlate PK parameters to nine covariates. The mean trough concentrations of teicoplanin 48 h after the onset of treatment and 24 h after the last injection (last trough) +/- standard deviations were 8.8 +/- 4.1 and 17.5 +/- 13.5 mg/liter, respectively. A significant increase was noted in the mean rate of elimination clearance of teicoplanin in neutropenic patients compared with that of HV (0.86 versus 0.73 liter/h, P = 0.002), as was the case with rates of distribution clearance (5.89 versus 4.94 liter/h, P = 0.002); the mean half-life of distribution was significantly shorter in patients than in HV (0.43 versus 0.61 h, P = 0.002). In contrast, the volumes of the central compartment (ca. 5.8 liters for both groups), the volumes of distribution at steady state (HV, 37.6 liters; patients, 55.9 liters), and the elimination half-lives (HV, 39.6 h; patients, 52.7 h) were not significantly different between HV and neutropenic patients. Interindividual variabilities of rates of clearance (coefficient of variation [CV], 43%) and elimination half-lives (CV, 56%) were mainly explained by the variabilities among rates of creatinine clearance. Interindividual variabilities of the volumes of the central compartment (CV, 33%) and the volumes of distribution at steady state (CV = 51%) were correlated to interindividual variabilities among numbers of leukocytes and the ages of patients, respectively. On the basis of the population PK model of teicoplanin, simulations were made to optimize the dosing schedule. A supplemental 6 mg/kg dose of teicoplanin at 36 h resulted in a trough concentration at 48 h of 16.0 +/- 4.5 mg/liter, with only 7% of patients having a trough concentration of less than 10 mg/liter, compared with 46% of patients on the usual schedule.
50S ribosomal subunit synthesis and translation are equivalent targets for erythromycin inhibition in Staphylococcus aureus
Authors: Champney W S , Burdine R
Published: October 2018

Macrolide antibiotics like erythromycin can prevent the formation of the 50S ribosomal subunit in growing bacterial cells, in addition to their inhibitory effect on translation. The significance of this novel finding has been further investigated. The 50% inhibitory doses of erythromycin for the inhibition of translation and 50S subunit assembly in Staphylococcus aureus cells were measured and were found to be identical. Together they account quantitatively for the observed effects of erythromycin on cell growth rates. There is also a direct relationship between the loss of rRNA from the 50S subunit and its accumulation as oligoribonucleotides in cells. The importance of this second site for erythromycin inhibition of bacterial cell growth is discussed.
Anti-influenza virus activities of 4-substituted 2,4-dioxobutanoic acid inhibitors
Authors: Hastings J C , Selnick H , Wolanski B , Tomassini J E
Published: October 2018

We previously identified a series of compounds which specifically inhibited the transcription of influenza A and B viruses (J. Tomassini, H. Selnick, M.E. Davies, M.E. Armstrong, J. Baldwin, M. Bourgeois, J. Hastings, D. Hazuda, J. Lewis, W. McClements, G. Ponticello, E. Radzilowski, G. Smith, A. Tebben, and A. Wolfe, Antimicrob. Agents Chemother. 38:2827-2837, 1994). The compounds, 4-substituted 2,4-dioxobutanoic acids, selectively targeted the cap-dependent endonuclease activity of the transcriptase complex. Additionally, several of these compounds effectively inhibited the replication of influenza virus but not other viruses in cell culture assays. Here, we report on the anti-influenza virus activities of other potent derivatives of the series evaluated in both in vitro and in vivo infectivity assays. These compounds inhibited the replication of influenza virus in yield reduction assays, with 50% inhibitory concentrations ranging from 0.18 to 0.71 microM. These 50% inhibitory concentrations were similar to those observed for inhibition of in vitro transcription (0.32 to 0.54 microM). One selected compound also elicited a dose-dependent inhibition of influenza virus replication in mice following an upper respiratory tract challenge. These studies demonstrate the antiviral efficacy of this inhibitor class and thereby establish the utility of influenza virus endonuclease as a chemotherapeutic target.
Electronic compliance assessment of antifungal prophylaxis for human immunodeficiency virus-infected women
Authors: Geletko S M , Segarra M , Mayer K H , Fiore T C , Bettencourt F A , Flanigan T P , Dudley M N
Published: October 2018

Several prophylactic medications for opportunistic or recurrent infections are used in human immunodeficiency virus-infected individuals. Essential to the efficacy evaluation of these agents is the accurate reporting of medication compliance. We hypothesized that poor patient compliance with thrice-weekly fluconazole prophylaxis would correlate with the occurrence of clinical events. Fluconazole compliance was monitored electronically by using the Medication Event Monitoring Systems with 19 women receiving fluconazole at 50 mg thrice weekly for prophylaxis of recurrent mucocutaneous candidiasis. During 202 patient-months of follow-up, eight breakthrough episodes of mucocutaneous candidiasis developed in four women; compliance data were available for seven of these episodes. At 6 months of therapy, more women with greater than or equal to 80% compliance were disease free compared with women with less than 80% compliance (P < 0.05; the Fisher exact test). These data suggest that documentation of medication compliance is essential in studies of chronic prophylaxis in human immunodeficiency virus-infected patients to properly evaluate drug efficacy and to avoid erroneous conclusions concerning drug failure.
In vitro synergy testing of macrolide-quinolone combinations against 41 clinical isolates of Legionella
Authors: Martin S J , Pendland S L , Chen C , Schreckenberger P , Danziger L H
Published: October 2018

Combination antimicrobial therapy against Legionella species has not been well studied. Several quinolones have activity against Legionella strains, which prompted this in vitro search for a synergistic combination with the macrolides. By a checkerboard assay, erythromycin, clarithromycin, and azithromycin, each in combination with ciprofloxacin and levofloxacin, were tested for synergy against 46 isolates of Legionella. The agar dilution method was employed using buffered charcoal-yeast extract media. A final inoculum of 10(4) CFU per spot was prepared from 24-h growth of each isolate. Plates were incubated at 35 degrees C for 48 h. Synergy, partial synergy, additive effect, or indifference was observed for all combinations of antibiotics tested. There was no antagonism observed. Synergy occurred to a significantly greater extent for the clarithromycin-levofloxacin (P = 0.0001) and azithromycin-levofloxacin (P = 0.003) combinations versus erythromycin-levofloxacin. The azithromycin-ciprofloxacin combination demonstrated significantly greater synergy than did either erythromycin-ciprofloxacin (P = 0.003) or clarithromycin-ciprofloxacin (P = 0.001). The newer macrolides clarithromycin and azithromycin may be more active in combination with a fluoroquinolone than is erythromycin.
Antimicrobial effect of acidified nitrite on gut pathogens: importance of dietary nitrate in host defense
Authors: Dykhuizen R S , Frazer R , Duncan C , Smith C C , Golden M , Benjamin N , Leifert C
Published: October 2018

Dietary intake of nitrate generates salivary nitrite, which is acidified in the stomach, leading to a number of reactive intermediates of nitrogen, among which are the potentially carcinogenic N-nitrosamines. Acidified nitrite, however, also has antimicrobial activity which coincides with the formation of nitric oxide. The present study examines the antimicrobial effect in vitro of acidified nitrite on Salmonella enteritidis, Salmonella typhimurium, Yersinia enterocolitica, Shigella sonnei, and Escherichia coli O157. First-order regression plots showed a linear inverse relationship of log-transformed proton and nitrite concentrations with MICs and MBCs after 30 min, 2 h, and 24 h of exposure (P < 0.001 for all antibacterial activities). Susceptibility to the acidified nitrate solutions ranked as follows: Y. enterocolitica > S. enteritidis > S. typhimurium = Shigella sonnei > E. coli O157 (P < 0.05). Addition of SCN-, but not that of CI-, increased the antibacterial activity (paired t testing, P < 0.001). Generation of salivary nitrite from dietary nitrate may provide significant protection against gut pathogens in humans.
Efficiency of nanoparticles as a carrier system for antiviral agents in human immunodeficiency virus-infected human monocytes/macrophages in vitro
Authors: Bender A R , von Briesen H , Kreuter J , Duncan I B , Rübsamen-Waigmann H
Published: October 2018

Polyhexylcyanoacrylate nanoparticles loaded with either the human immunodeficiency virus (HIV) protease inhibitor saquinavir (Ro 31-8959) or the nucleoside analog zalcitabine (2',3'-dideoxycytidine) were prepared by emulsion polymerization and tested for antiviral activity in primary human monocytes/macrophages in vitro. Both nanoparticulate formulations led to a dose-dependent reduction of HIV type 1 antigen production. While nanoparticle-bound zalcitabine showed no superiority to an aqueous solution of the drug, a significantly higher efficacy was observed with saquinavir-loaded nanoparticles. In acutely infected cells, an aqueous solution of saquinavir showed little antiviral activity at concentrations below 10 nM, whereas the nanoparticulate formulation exhibited a good antiviral effect at a concentration of 1 nM and a still-significant antigen reduction at 0.1 nM (50% inhibitory concentrations = 4.23 nM for the free drug and 0.39 nM for the nanoparticle-bound drug). At a concentration of 100 nM, saquinavir was completely inactive in chronically HIV-infected macrophages, but when bound to nanoparticles it caused a 35% decrease in antigen production. Using nanoparticles as a drug carrier system could improve the delivery of antiviral agents to the mononuclear phagocyte system in vivo, overcoming pharmacokinetic problems and enhancing the activities of drugs for the treatment of HIV infection and AIDS.
Resistance to fluoroquinolones in Escherichia coli isolated from poultry
Authors: Bazile-Pham-Khac S , Truong Q C , Lafont J P , Gutmann L , Zhou X Y , Osman M , Moreau N J
Published: October 2018

Quinolone-resistant Escherichia coli strains were isolated from poultry clinical samples in Saudi Arabia. The poultry flocks had been treated with oxolinic acid or flumequine prophylaxis. The measure of the uptake of fluoroquinolones showed that none of the strains had a reduced accumulation of quinolones. The result of complementation with the wild-type E. coli gyrA gene, which restored fluoroquinolone susceptibility, and the isolation of DNA gyrase from six isolates indicated that the resistant strains had an altered DNA gyrase. The minimum effective dose of ciprofloxacin for inhibition of supercoiling catalyzed by the isolated gyrases varied from 0.085 microgram/ml for a susceptible isolate (MIC < 4 micrograms/ml) up to 96 micrograms/ml for the more resistant one (strain 215, MIC > 64 micrograms/ml). For the same two isolates, the minimum effective doses of sparfloxacin varied from 0.17 up to 380 micrograms/ml. The in vitro selection of spontaneous single-step fluoroquinolone-resistant mutants using ciprofloxacin suggested that the more resistant mutants are likely the result of several mutations. These results also show that, as in human medicine, cross-resistance between older quinolones and fluoroquinolones can exist in veterinary isolates and reiterate the need for the prudent use of these drugs.