bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloning and sequence of the gene encoding a cefotaxime-hydrolyzing class A beta-lactamase isolated from Escherichia coli
Authors: Ishii Y , Ohno A , Taguchi H , Imajo S , Ishiguro M , Matsuzawa H
Published: June 2012

Escherichia coli TUH12191, which is resistant to piperacillin, cefazolin, cefotiam, ceftizoxime, cefuzonam, and aztreonam but is susceptible to cefoxitin, latamoxef, flomoxef, and imipenem, was isolated from the urine of a patient treated with beta-lactam antibiotics. The beta-lactamase (Toho-1) purified from the bacteria had a pI of 7.8, had a molecular weight of about 29,000, and hydrolyzed beta-lactam antibiotics such as penicillin G, ampicillin, oxacillin, carbenicillin, piperacillin, cephalothin, cefoxitin, cefotaxime, ceftazidime, and aztreonam. Toho-1 was markedly inhibited by beta-lactamase inhibitors such as clavulanic acid and tazobactam. Resistance to beta-lactams, streptomycin, spectinomycin, sulfamethoxazole, and trimethoprim was transferred by conjugational transfer from E. coli TUH12191 to E. coli ML4903, and the transferred plasmid was about 58 kbp, belonging to incompatibility group M. The cefotaxime resistance gene for Toho-1 was subcloned from the 58-kbp plasmid by transformation of E. coli MV1184. The sequence of the gene for Toho-1 was determined, and the open reading frame of the gene consisted of 873 or 876 bases (initial sequence, ATGATG). The nucleotide sequence of the gene (DDBJ accession number D37830) was found to be about 73% homologous to the sequence of the gene encoding a class A beta-lactamase produced by Klebsiella oxytoca E23004. According to the amino acid sequence deduced from the DNA sequence, the precursor consisted of 290 or 291 amino acid residues, which contained amino acid motifs common to class A beta-lactamases (70SXXK, 130SDN, and 234KTG). Toho-1 was about 83% homologous to the beta-lactamase mediated by the chromosome of K. oxytoca D488 and the beta-lactamase mediated by the plasmid of E. coli MEN-1. Therefore, the newly isolated beta-lactamase Toho-1 produced by E. coli TUH12191 is similar to beta-lactamases produced by K. oxytoca D488, K. oxytoca E23004, and E. coli MEN-1 rather than to mutants of TEM or SHV enzymes. Toho-1 has shown the highest degree of similarity to K. oxytoca class A beta-lactamase. Detailed comparison of Toho-1 with other beta-lactamases implied that replacement of Asn-276 by Arg with the concomitant substitution of Thr for Arg-244 is an important mutation in the extension of the substrate specificity.
Metabolic pathways for activation of the antiviral agent 9-(2-phosphonylmethoxyethyl)adenine in human lymphoid cells
Authors: Robbins B L , Greenhaw J , Connelly M C , Fridland A
Published: June 2012

9-(2-Phosphonylmethoxyethyl)adenine (PMEA), the acyclic phosphonate analog of adenine monophosphate, is a promising antiviral drug with activity against herpesviruses, Epstein-Barr virus, and retroviruses, including the human immunodeficiency virus. In order to be active, it must be converted to the diphosphate derivative, the putative inhibitor of viral DNA polymerases. The metabolic pathway responsible for activation of PMEA is unclear. The metabolism of PMEA was investigated in human T-lymphoid cells (CEMss) and a PMEA-resistant subline (CEMss(r-1)) with a partial deficiency in adenylate kinase activity. Experiments with [3H]PMEA showed that extracts of CEMss phosphorylated PMEA to its mono- and diphosphate in the presence of ATP as the phosphate donor. No other nucleotides or 5-phosphoribosyl pyrophosphate displayed appreciable activity as a phosphate donor. Subcellular fractionation experiments showed that CEMss cells contained two nucleotide kinase activities, one in mitochondria and one in the cytosol, which phosphorylated PMEA. The PMEA-resistant CEMss mutant proved to have a deficiency in the mitochondrial adenylate kinase activity, indicating that this enzyme was important in the phosphorylation of PMEA. Other effective antiviral purine phosphonate derivatives of PMEA showed a profile of phosphorylating activity similar to that of PMEA. By comparison, phosphorylation of the pyrimidine analog (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine proceeded by an enzyme present in the cytosol. We conclude from these studies that adenylate kinase which has been localized in the intermembrane space of mitochondria is the major route for PMEA phosphorylation in CEMss cells but that another hitherto unidentified enzyme(s) present in the cytosol may contribute to the anabolism of the phosphonates.
Treatment of Mycobacterium haemophilum infection in a murine model with clarithromycin, rifabutin, and ciprofloxacin
Authors: Atkinson B A , Bocanegra R , Graybill J R
Published: June 2012

An animal model of disseminated Mycobacterium haemophilum infection was utilized to compare treatment with azithromycin, ciprofloxacin, rifabutin, and the combination of clarithromycin with rifabutin. Following subcutaneous challenge with M. haemophilum, local and disseminated infection occurred only in immunosuppressed mice. For disseminated infection, ciprofloxacin was relatively ineffective therapy. Clarithromycin and rifabutin alone significantly reduced the tissue burden in the spleen after 4 weeks of therapy. Combination therapy with rifabutin and clarithromycin was superior to 4 weeks of treatment with the individual agents. When immunosuppressed mice were treated for 20 weeks with the combination of rifabutin and clarithromycin, the tissue burden remained reduced in the spleen at 1 month following the completion of therapy. Combined rifabutin and clarithromycin provide effective treatment for M. haemophilum in this model.
In vitro antibacterial activity and beta-lactamase stability of a new carbapenem, BO-2727
Authors: Inoue K , Hamana Y , Mitsuhashi S
Published: June 2012

The in vitro activity of BO-2727, a new carbapenem, was compared with those of meropenem, biapenem, imipenem, and ceftazidime. BO-2727 was four- or eightfold more active than the other carbapenems against methicillin-resistant staphylococci and Pseudomonas aeruginosa strains, including imipenem- and ceftazidime-resistant bacteria. BO-2727 was quite stable to penicillinases, cephalosporinases, and oxyiminocephalosporinases, but not to metallo-beta-lactamase. Time-kill studies against Staphylococcus aureus Smith, Escherichia coli ML4707, and P. aeruginosa GN11189 showed that BO-2727 has potent bactericidal activity at concentrations greater than the MIC.
Pharmacokinetics of cefpirome in pediatric patients
Authors: Nahata M C , Barson W J , Puri S K
Published: June 2012

Cefpirome is a new investigational cephalosporin. We designed a study to determine the pharmacokinetics and tolerance of cefpirome in pediatric patients. A single dose of cefpirome was administered intravenously over 15 min to 18 patients (age 0.5 to 18 years). The doses were 10 mg/kg of body weight for five patients, 25 mg/kg of body weight for seven patients, and 50 mg/kg of body weight for six patients. Blood samples were collected at 0, 0.25, 0.5, 1, 3, 5, and 8 h after the dose, and cefpirome was measured by a high-performance liquid chromatography method. The maximum concentration in serum ranged from about 53.6 to 454 micrograms/ml after doses of 10 to 50 mg/kg. The total body clearance, apparent volume of distribution, and elimination half-life were 2.15 +/- 0.70 ml/min/kg, 0.32 +/- 0.32 liter/kg, and 1.8 +/- 1.3 h, respectively. No significant adverse effects were attributed to cefpirome. These data may be useful in conducting efficacy and safety studies of cefpirome in pediatric patients.
Population differences in ganciclovir clearance as determined by nonlinear mixed-effects modelling
Authors: Yuen G J , Drusano G L , Fletcher C , Capparelli E , Connor J D , Lalezari J P , Drew L , Follansbee S , Busch D , Jacobson M
Published: June 2012

We examined the pharmacokinetics of ganciclovir in different populations of cytomegalovirus (CMV)-infected patients through the use of nonlinear mixed-effects modelling. As expected, patient weight and estimated creatinine clearance were shown to be important covariates in the serum ganciclovir clearance. Unexpectedly, major differences in ganciclovir clearance between different populations of patients were found. Human immunodeficiency virus (HIV)-infected patients with CMV retinitis cleared ganciclovir 41% faster than HIV-infected patients only shedding CMV into the urine. Solid-organ transplant patients had a serum clearance one-fourth that of HIV-infected patients, even with correction for creatinine clearance. These findings require prospective validation and may have important implications for ganciclovir dosing in different populations of CMV-infected patients.
Postantibiotic effects and Burkholderia (Pseudomonas) pseudomallei: evaluation of current treatment
Authors: Walsh A L , Smith M D , Wuthiekanun V , White N J
Published: June 2012

The postantibiotic effects (PAEs) OF 16 antibiotics or antibiotic combinations currently used against Burkholderia (Pseudomonas) pseudomallei were determined. The beta-lactams had zero PAEs, while the carbapenems and ciprofloxacin induced median PAEs of 1 and 5 h, respectively. These results emphasize the need to maintain antibiotic levels above inhibitory concentrations in blood throughout the dosing interval in cases of severe melioidosis.
Anti-Mastigina activities of eight contact lens solutions
Authors: Niszl I A , Markus M B , van Deventer J M
Published: June 2012

The effects of eight contact lens solutions on a Mastigina sp., which was associated with the infected eye of a patient, were studied. The solutions which killed the organism promptly were those which are used for gas-permeable and hard contact lenses. Some solutions for soft contact lenses were more effective than others.
Clinical pharmacokinetics of adefovir in human immunodeficiency virus type 1-infected patients
Authors: Cundy K C , Barditch-Crovo P , Walker R E , Collier A C , Ebeling D , Toole J , Jaffe H S
Published: June 2012

The pharmacokinetics and bioavailability of adefovir [9-[2-(phosphonomethoxy)ethyl]adenine] were examined at two dose levels in three phase I/II studies in 28 human immunodeficiency type 1-infected patients. The concentrations of adefovir in serum following the intravenous infusion of 1.0 or 3.0 mg/kg of body weight were dose proportional and declined biexponentially, with an overall mean +/- standard deviation terminal half-life of 1.6 +/- 0.5 h (n = 28). Approximately 90% of the intravenous dose was recovered unchanged in the urine in 12 h, and more than 98% was recovered by 24 h postdosing. The overall mean +/- standard deviation total serum clearance of the drug (223 +/- 53 ml/h/kg; n = 25) approximated the renal clearance (205 +/- 78 ml/h/kg; n = 20), which was significantly higher (P < 0.01) than the baseline creatinine clearance in the same patients (88 +/- 18 ml/h/kg; n = 25). Since adefovir is essentially completely unbound in plasma or serum, these data indicate that active tubular secretion accounted for approximately 60% of the clearance of adefovir. The steady-state volume of distribution of adefovir (418 +/- 76 ml/kg; n = 28) suggests that the drug was distributed in total body water. Repeated daily dosing with adefovir at 1.0 mg/kg/day (n = 8) and 3.0 mg/kg/day (n = 4) for 22 days did not significantly alter the pharmacokinetics of the drug; there was no evidence of accumulation. The oral bioavailability of adefovir at a 3.0-mg/kg dose was < 12% (n = 5) on the basis of the concentrations in serum or 16.4% +/- 16.0% on the basis of urinary recovery. The subcutaneous bioavailability of adefovir at a 3.0-mg/kg dose was 102% +/- 8.3% (n = 5) on the basis of concentrations in serum or 84.8% +/- 28.5% on the basis of urinary recovery. These data are consistent with preclinical observations in various species.
Routine susceptibility testing of four antibiotic combinations for improvement of laboratory guide to therapy of cystic fibrosis infections caused by Pseudomonas aeruginosa
Authors: Weiss K , Lapointe J R
Published: June 2012

Previous studies have demonstrated synergy between an aminoglycoside and a beta-lactam for treating Pseudomonas aeruginosa infections. Cystic fibrosis patients are prone to infection by this bacterium, which becomes very resistant with recurrent antibiotic treatments. The purpose of this study was to evaluate the susceptibility patterns of 122 isolates of P. aeruginosa isolated from cystic fibrosis patients to five individual antibiotics (tobramycin, ceftazidime, piperacillin, ticarcillin, and imipenem) and to four antibiotic combinations (tobramycin associated with one of the other antibiotics). Strains were selected because of their resistance to individual antimicrobial agents, which ranged from 21.3% for imipenem to 56.5% for tobramycin. By using an automated broth microdilution method, we were able to demonstrate synergy against 39 strains (32%) with tobramycin-ticarcillin, against 38 strains (31%) with tobramycin-piperacillin, against 47 strains (39%) with tobramycin-ceftazidime, and against 23 strains (19%) with tobramycin-imipenem. Of the 122 isolates, 77 (63%) were rendered significantly susceptible to at least one of the four antibiotic combinations by synergy. These results suggest that when appropriate technology is available, susceptibility to antibiotic combinations greatly improves the guide to antibiotic therapy for infections due to P. aeruginosa in cystic fibrosis patients.
Staphylococcus aureus penicillin-binding protein 4 and intrinsic beta-lactam resistance
Authors: Henze U U , Berger-Bächi B
Published: June 2012

Increased levels of production of penicillin-binding protein PBP 4 correlated with in vitro acquired intrinsic beta-lactam resistance in a mutant derived from a susceptible strain of Staphylococcus aureus, strain SG511 Berlin. Truncation of the PBP 4 C-terminal membrane anchor abolished the PBP 4 content of cell membrane preparations as well as the resistance phenotype. A single nucleotide change and a 90-nucleotide deletion, comprising a 14-nucleotide inverted repeat in the noncoding pbp4 gene promoter proximal region, were the only sequence differences between the resistant mutant and the susceptible parent. These mutations were thought to be responsible for the observed overproduction of PBP 4 in the intrinsically beta-lactam-resistant mutant. The pbp4 gene was flanked upstream by the open reading frame abcA, coding for an ATP-binding cassette transporter-like protein showing similarities to eukaryotic multidrug transporters and downstream by a glycerol 3-phosphate cytidyltransferase (tagD)-like open reading frame presumably involved in teichoic acid synthesis. The abcA-pbp4-tagD gene cluster was located in the SmaI-D fragment in the S. aureus 8325 chromosome in close proximity to the RNA polymerase gene rpoB.
Inhibition of influenza virus transcription by 2'-deoxy-2'-fluoroguanosine
Authors: Tisdale M , Ellis M , Klumpp K , Court S , Ford M
Published: June 2012

The nucleoside analog 2'-deoxy-2'-fluoroguanosine (2'-fluorodGuo) is phosphorylated by cellular enzymes and reversibly inhibits influenza virus replication in chick embryo cells within the first 4 h of infection. RNA hybridization studies revealed that primary and secondary transcription of influenza virus RNA were blocked at a compound concentration of 10 microM, but no inhibition of cell protein synthesis was seen even at high compound concentrations (200 microM). In vitro, the triphosphate of 2'-fluorodGuo is a competitive inhibitor of influenza virus transcriptase activity from disrupted virus, with a Ki of 1.0 microM. The cellular polymerases DNA polymerase alpha and RNA polymerase II were only weakly inhibited or were insusceptible to 2'-fluorodGTP. In kinetic studies with the influenza virus transcriptase, 2'-fluorodGTP, in the absence of GTP, blocked elongation of the virus RNA chain. Similarly, by using purified ribonucleoprotein complexes it was found that the addition of a single nucleotide of 2'-fluorodGTP to the virus RNA caused chain termination, which resulted in the blockage of further virus transcription. Furthermore, the specificity for influenza virus transcriptase was confirmed when the transcriptase from partially resistant virus was found to be 10-fold less susceptible to 2'-fluorodGTP (Ki = 13.1 microM).
Effectiveness of short-course therapy (5 days) with cefuroxime axetil in treatment of secondary bacterial infections of acute bronchitis
Authors: Henry D , Ruoff G E , Rhudy J , Puopolo A , Drehobl M , Schoenberger J , Giguere G , Collins J J
Published: June 2012

Five hundred thirty-seven patients were enrolled in two independent, investigator-blinded, multicenter, randomized clinical trials comparing the clinical and bacteriologic efficacies and the safety of 5- or 10-day treatment with cefuroxime axetil with those of 10-day treatment with amoxicillin-clavulanate in the treatment of secondary bacterial infections of acute bronchitis. Patients received either 5 or 10 days of treatment (n = 177 in each group) with cefuroxime axetil at 250 mg twice daily or 10 days of treatment (n = 183) with amoxicillin-clavulanate at 500 mg three times daily. Patients in the cefuroxime axetil (5 days) group received placebo on days 6 to 10. Bacteriologic assessments were based on sputum specimen cultures obtained preceding and, when possible, following treatment. Organisms were isolated from the pretreatment sputum specimens of 242 of 537 (45%) patients, with the primary pathogens being Haemophilus influenzae, Haemophilus parainfluenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and Staphylococcus aureus (28, 25, 13, 9, and 8% of isolates, respectively). Pathogens were eradicated or presumed to be eradicated in 87% (52 of 60), 91% (53 of 58), and 86% (60 of 70) of bacteriologically evaluable patients treated with cefuroxime axetil (5 days), cefuroxime axetil (10 days), and amoxicillin-clavulanate, respectively. A satisfactory clinical outcome (cure or improvement) was achieved in 82% (107 of 130), 86% (117 of 136), and 83% (130 of 157) of the clinically evaluable patients treated with cefuroxime axetil (5 days), cefuroxime axetil (10 days), and amoxicillin-clavulanate, respectively. Treatment with amoxicillin-clavulanate was associated with a significantly higher incidence of drug-related adverse events than was treatment with cefuroxime axetil for either 5 or 10 days (P = 0.001), primarily reflecting a higher incidence of drug-related gastrointestinal adverse events (37 versus 19 and 15%, respectively; P < 0.001), particularly diarrhea and nausea. These results indicate that treatment with cefuroxime axetil at 250 mg twice daily for 5 days is as effective as treatment for 10 days with either the same dose of cefuroxime axetil or amoxicillin-clavulanate at 500 mg three times daily in patients with acute bronchitis. In addition, treatment with cefuroxime axetil for either 5 or 10 days is associated with significantly fewer gastrointestinal adverse events, particularly diarrhea and nausea, than is 10-day treatment with amoxicillin-clavulanate.
Comparative analysis of anti-human immunodeficiency virus type 1 activities of dideoxynucleoside analogs in resting and activated peripheral blood mononuclear cells
Authors: Shirasaka T , Chokekijchai S , Yamada A , Gosselin G , Imbach J L , Mitsuya H
Published: June 2012

We determined the anti-human immunodeficiency virus type 1 (anti-HIV-1) activities of various dideoxy-nucleoside analogs by using phytohemagglutinin-activated peripheral blood mononuclear cells (PHA-PBMs) and resting PBMs (R-PBMs) as target cells. The comparative order of anti-HIV-1 activity in PHA-PBMs was azidothymidine (AZT) > dideoxycytidine (ddC) > dideoxythymidinene (d4T) > dideoxyinosine (ddI) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) > 2'-beta-fluoro-dideoxyadenosine (F-ara-ddA), while that in R-PBMs was ddC > ddI, PMEA, and F-ara-ddA, > AZT and d4T. A pronucleotide, bis-(S-acetylthioethanol)phosphotriester-ddAMP, which bypasses the anabolic monophosphorylation step for the intracellular delivery of ddAMP, was highly active both in PHA-PBMs and R-PBMs. These data may have basic and clinical relevance in the design of anti-HIV chemotherapy, particularly combination chemotherapy with dideoxynucleosides, and in the development of active pronucleotides.
Use of decimal assay for additivity to demonstrate synergy in pair combinations of econazole, nikkomycin Z, and ibuprofen against Candida albicans in vitro
Authors: Tariq V N , Scott E M , McCain N E
Published: June 2012

Interactions between six compounds (econazole, miconazole, amphotericin B, nystatin, nikkomycin Z, and ibuprofen) were investigated for their antifungal activities against Candida albicans by using pair combinations in an in vitro decimal assay for additivity based on disk diffusion. Additive interactions were observed between miconazole and econazole, amphotericin B and nystatin, and amphotericin B and ibuprofen, while an antagonistic interaction was observed between econazole and amphotericin B. Synergistic interactions were recorded for the combinations of econazole and ibuprofen, econazole and nikkomycin Z, and ibuprofen and nikkomycin Z.
Autolysis of methicillin-resistant Staphylococcus aureus is involved in synergism between imipenem and cefotiam
Authors: Matsuda K , Nakamura K , Adachi Y , Inoue M , Kawakami M
Published: June 2012

Imipenem-induced autolysis and the activity of imipenem plus cefotiam were studied in 16 strains of methicillin-resistant Staphylococcus aureus (MRSA). The degree of imipenem-induced autolysis and the rate of synergistic action of imipenem plus cefotiam varied among strains and did not correlate with susceptibility to either imipenem or cefotiam. However, the degree of autolysis correlated well with susceptibility to the synergistic action of imipenem plus cefotiam. In methicillin-susceptible S. aureus strains, both imipenem-induced autolysis and the synergistic activity of the combined drugs were less than those observed in MRSA strains. Differences in the degree of autolysis were not due to differences in autolytic enzyme production. The autolysis of imipenem-pretreated MRSA was enhanced further by cefotiam, while treatment of cells in the reverse order did not enhance autolysis. These findings indicate that cell wall impairment in MRSA is caused by exposure to imipenem but not to cefotiam and that this difference in drug actions results in synergism between imipenem and cefotiam. The possible participation of penicillin-binding proteins PBP 2' and PBP4 in the observed effect is discussed.
Use of time-kill methodology to assess antimicrobial combinations against metronidazole-susceptible and metronidazole-resistant strains of Helicobacter pylori
Authors: Coudron P E , Stratton C W
Published: June 2012

Optimal therapy for Helicobacter pylori infection to date, consists of metronidazole, bismuth, and tetracycline. This combination, however, is less effective against metronidazole-resistant organisms. We used a time-kill kinetic methodology to assess the bactericidal effects of selected agents, alone and in combination, to a metronidazole-susceptible and a metronidazole-resistant strain of H. pylori. single, double, and triple agents showed increasing bactericidal activity. The combination of metronidazole, bismuth, and tetracycline showed maximal killing effect (no detectable regrowth) against the susceptible strain, but against the resistant strain this combination showed less killing. The time-kill methodology may therefore offer an in vitro approach to the initial selection of agents to be evaluated for the treatment of H. pylori infections.
Effects of free and liposome-encapsulated antibiotics on adherence of Pseudomonas aeruginosa to collagen type I
Authors: Trafny E A , Stepińska M , Antos M , Grzybowski J
Published: June 2012

The adherence of 27 clinical Pseudomonas aeruginosa strains to collagen type I was investigated by using a solid-phase assay. The influence of free antibiotics (amikacin, gentamicin, piperacillin, bacitracin, and polymyxin B) and liposome-entrapped antibiotics (amikacin and polymyxin B) on bacterial attachment to collagen type I was examined. The greatest inhibitory effect was shown for free and liposomal amikacin, which decreased the attachment of 74 and 100% of tested strains, respectively. The mean percent attachment (+/- standard deviation) in the presence of free amikacin was 65.7% (+/- 12.0%) as measured by solid-phase assay. In the presence of liposomal amikacin, the attachment ranged from 17.3% (+/- 6.0%) to 42.1% (+/- 9.4%), depending on the antibiotic solvent. In contrast, polymyxin B, even at a subinhibitory concentration, enhanced attachment of all P. aeruginosa isolates to collagen. Liposomal polymyxin B displayed a protective effect only when the encapsulated drug was of a low concentration. Application of liposome-encapsulated amikacin may be advantageous in injured tissues in which extracellular matrix structures become exposed.
Mutacin II, a bactericidal antibiotic from Streptococcus mutans
Authors: Chikindas M L , Novák J , Driessen A J , Konings W N , Schilling K M , Caufield P W
Published: June 2012

Mutacin II is an antibiotic that is produced by group II Streptococcus mutans. It inhibits the growth of other streptococci as well as many other gram-positive microorganisms by a hitherto unknown mechanism. Mutacin II possess bactericidal activity against susceptible cells. It transiently depolarizes the transmembrane electrical potential (delta psi) and the transmembrane pH gradient (delta pH) and partially inhibits amino acid transport. However, it rapidly depletes the intracellular ATP pool in glucose-energized cells and prevents the generation of ATP. It is concluded that mutacin II does not belong to the group of pore-forming antibiotics (type A) or to the type B antibiotics, which inhibit phospholipases or interfere with peptidoglycan biosynthesis. Mutacin II acts by inhibiting essential enzyme functions at the level of metabolic energy generation, an activity that has not yet been classified for antibiotics.
Structure-activity and cross-resistance evaluations of a series of human immunodeficiency virus type-1-specific compounds related to oxathiin carboxanilide
Authors: Buckheit R W , Kinjerski T L , Fliakas-Boltz V , Russell J D , Stup T L , Pallansch L A , Brouwer W G , Dao D C , Harrison W A , Schultz R J
Published: June 2012

A series of compounds related to the nonnucleoside reverse transcriptase (RT) inhibitor (NNRTI) oxathiin carboxanilide (UC84) were evaluated for activity against the human immunodeficiency virus (HIV) to determine structural requirements for anti-HIV activity. Twenty-seven compounds representative of the more than 400 Uniroyal Chemical Company (UC) compounds were evaluated for structure-activity relationships. Several of the compounds evaluated were highly active, with 50% effective concentrations in the nanomolar range and therapeutic indices of > 1,000. Highly synergistic anti-HIV activity was observed for each compound when used in combination with 3'-azido-3'-deoxythymidine; additive to slightly synergistic interactions were observed with the compounds used in combination with dideoxycytidine. In combination with the NNRTI costatolide, only UC38 synergistically inhibited HIV type 1. Residues in the RT which, when mutated, impart resistance to the virus isolates selected in cell culture, against virus variants with site-directed mutations, and against RTs containing defined single amino acid changes. The mutations included changes in RT amino acids 100, 101, 103, 106, 108, and 181. The results with isolates selected in cell culture indicate that the carboxanilide compounds interact with the RT at two vulnerable sites, selecting UC-resistant virus isolates with the Y-to-C mutation at position 181 (Y181C) or the L100I substitution. A resistant virus isolate containing both Y181C combination with calanolide A, an NNRTI which retains activity against virus with the single Y181C mutation, UC10 rapidly selected a virus isolate with the K103N mutation. The merits of selecting potential candidate anti-HIV agents to be used in rational combination drugs design as part of an armamentarium of highly active anti-HIV compounds are discussed.
The antileishmanial agent licochalcone A interferes with the function of parasite mitochondria
Authors: Zhai L , Blom J , Chen M , Christensen S B , Kharazmi A
Published: June 2012

Our previous studies have shown that licochalcone A, an oxygenated chalcone, has antileishmanial (M. Chen, S.B. Christensen, J. Blom, E. Lemmich, L. Nadelmann, K. Fich, T.G. Theander, and A. Kharazmi, Antimicrob, Agents Chemother. 37:2550-2556, 1993; M. Chen, S.B. Christensen, T.G. Theander, and A. Khrazmi, Antimicrob. Agents Chemother. 38:1339-1344, 1994) and antimalarial (M. Chen, T.G. Theander, S.B. Christensen, L. Hviid, L. Zhai, and A. Kaharazmi, Antimicrob. Agents Chemother. 38:1470-1475, 1994) activities. We have observed that licochalcone A alters the ultrastructure of the mitochondria of Leishmania promastigotes (Chen et al., Antimicrob. Agents Chemother. 37:2550-2556, 1993). The present study was designed to examine this observation further and investigate the mechanism of action of antileishmanial activity of licochalcone A. Electron microscopic studies showed that licochalcone A altered the ultrastructure of Leishmania major promastigote and amastigote mitochondria in a concentration-dependent manner without damaging the organelles of macrophages or the phagocytic function of these cells. Studies on the function of the parasite mitochondria showed that licochalcone A inhibited the respiration of the parasite by the parasites. Moreover, licochalcone A inhibited the activity of the parasite mitochondrial dehydrogenase. The inhibition of the activity of the parasite mitochondrial enzyme correlated well with the changes in the ultrastructure of the mitochondria shown by electron microscopy. These findings demonstrate that licochalcone A alters the ultrastructure and function of the mitochondria of Leishmania parasites.
Transition mutations in the 23S rRNA of erythromycin-resistant isolates of Mycoplasma pneumoniae
Authors: Lucier T S , Heitzman K , Liu S K , Hu P C
Published: June 2012

Erythromycin is the drug of choice for treatment of Mycoplasma pneumoniae infections due to its susceptibility to low levels of this antibiotic. After exposure of susceptible strains to erythromycin in vitro and in vivo, mutants resistant to erythromycin and other macrolides were isolated. Their phenotypes have been characterized, but the genetic basis for resistance has never been determined. We isolated two resistant mutants (M129-ER1 and M129-ER2) by growing M. pneumoniae M129 on agar containing different amounts of erythromycin. In broth dilution tests both strains displayed resistance to high levels of several macrolide-lincosamide-streptogramin B (MLS) antibiotics. In binding studies, ribosomes isolated from the resistant strains exhibited significantly lower affinity for [14C]erythromycin than did ribosomes from the M129 parent strain. Sequencing of DNA amplified from the region of the 2S rRNA gene encoding domain V revealed an A-to-G transition in the central loop at position 2063 of M129-ER1 and a similar A-to-G transition at position 2064 in M129-ER2. Transitions at homologous locations in the 23S rRNA from other organisms have been shown to result in resistance to MLS antibiotics. Thus, MLS-like resistance can occur in M. pneumoniae as the result of point mutations in the 23S rRNA gene which reduce the affinity of these antibiotics for the ribosome. Since they involve only single-base changes, development of resistance to erythromycin in vivo by these mechanisms could be relatively frequent event.
MS-8209, a new amphotericin B derivative, provides enhanced efficacy in delaying hamster scrapie
Authors: Adjou K T , Demaimay R , Lasmezas C , Deslys J P , Seman M , Dormont D
Published: June 2012

To test the efficacy of a new amphotericin B derivative, MS-8209, in delaying scrapie, hamsters were infected intracerebrally with the 263K scrapie agent and treated with MS-8209 either early in the course of the disease or continuously. The results show that (i) all treatments lengthened the incubation period of hamster scrapie, (ii) continuous treatment with MS-8209 doubled the length of the incubation period compared with that observed in infected, untreated animals, and (iii) all treatments delayed the accumulation of a proteinase-resistant prion protein and glial fibrillary acidic protein in the brain. These findings suggest that MS-8209 is a powerful tool for investigating the pathogenesis of transmissible subacute spongiform encephalopathies.
In vitro antibacterial activity of DU-6859a, a new fluoroquinolone
Authors: Nakane T , Iyobe S , Sato K , Mitsuhashi S
Published: June 2012

The in vitro antibacterial activity of DU-6859a, a new fluoroquinolone, against a wide variety of clinical isolates was evaluated and compared with those of tosufloxacin, ofloxacin, ciprofloxacin, and sparfloxacin. DU-6859a showed potent broad-spectrum activity against gram-positive, gram-negative, and anaerobic bacteria, and its activity was greater than those of the control quinolones. By comparison of MICs at which 90% of strains are inhibited, DU-6859a had potent activity against bacteria resistant to the control quinolones. The time-killing curves of quinolones showed that the number of viable cells decreased rapidly during 2 to 4 of incubation, and regrowth was not seen even after 8 h incubation. At a concentration of four times the MIC, the frequencies of appearance of spontaneous mutants of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa resistant to DU-6859a were < or = 4.0 x 10(-9) to 1.9 x 10(-8). The 50% inhibitory concentrations of DU-6859a were 0.86 and 1.05 micrograms/ml for the supercoiling activities of DNA gyrases isolated from E. coli and P. aeruginosa, respectively. The rank order of the 50% inhibitory concentrations observed for both DNA gyrases roughly paralleled the MICs.
Inhibition of human immunodeficiency virus integrase by bis-catechols
Authors: LaFemina R L , Graham P L , LeGrow K , Hastings J C , Wolfe A , Young S D , Emini E A , Hazuda D J
Published: June 2012

The human immunodeficiency virus type 1 (HIV-1) integrase protein is required for the productive infection of T-lymphoid cells in culture (R. L. LaFemina, C. L. Schneider, H. L. Robbins, P. L. Callahan, K. LeGrow, E. Roth, W. A. Schleif, and E. A. Emini, J. Virol. 66:7414-7419, 1992). This observation suggests that chemical inhibitors of integrase may prevent the spread of HIV in infected individuals. In our search for such potential chemotherapeutic agents, we observed that beta-conidendrol inhibits both the sequence-dependent and sequence-independent endonucleolytic activities of integrase with comparable potencies in vitro (50% inhibitory concentration, 500 nM). Structurally related compounds tested for their abilities to inhibit integrase generated a limited structure-activity analysis which demonstrated that potency is associated with the bis-catechol structure: two pairs of adjacent hydroxyls on separate benzene rings. beta-Conidendrol did not inhibit several other endonucleases and/or phosphoryltransferases. Although beta-conidendrol was not effective in preventing HIV-1 infection in cell culture, the in vitro data demonstrate that it is possible to identify selective agents targeted against this essential HIV-1 function.
Effect of zidovudine on transplacental pharmacokinetics of ddI in the pigtailed macaque (Macaca nemestrina)
Authors: Pereira C M , Nosbisch C , Baughman W L , Unadkat J D
Published: June 2012

Since zidovudine and ddI may be used in combination in the future to treat pregnant women who are human immunodeficiency virus positive, we conducted a study to determine whether zidovudine affects the transfer of ddI across the placenta. Zidovudine and ddI were infused simultaneously to three near-term pregnant macaques (Macaca nemestrina) at 156 +/- 1.5 days of gestation. Samples of maternal and fetal blood and amniotic fluid were drawn at intervals for 30 h. The steady-state dideoxyinosine concentrations in the plasma of the dam (Cssd), the fetus (Cssf), and the amniotic fluid (Cssa) and the ratios Cssf/Cssd and Cssa/Cssf were found to be not significantly different from the values previously determined after the administration of ddI alone during the same pregnancy. We conclude that concurrent zidovudine administration does not affect the transfer of ddI across the placenta in near-term Macaca nemestrina.
Molecular characterization of nine different types of mutants among 107 inhibitor-resistant TEM beta-lactamases from clinical isolates of Escherichia coli
Authors: Henquell C , Chanal C , Sirot D , Labia R , Sirot J
Published: June 2012

DNA-DNA hybridization and sequencing were performed to determine the molecular basis of resistance to clavulanic acid in 107 inhibitor-resistant TEM (IRT) enzymes produced by Escherichia coli clinical isolates. These beta-lactamases derived from TEM-1 enzyme focused at pI 5.2 (n = 68) or 5.4 (n = 39) and were very poorly inhibited by clavulanic acid compared with TEM-1 enzyme. Results showed that the amino acid sequences of 84 of the 107 enzymes differ from TEM-1 by one or two substitutions previously described: Arg-244-->Ser (IRT-2) in 22 strains, Met-69-->Leu (TEM-33) in 17 strains, Met-69-->Val (TEM-34) in 14 strains, Met-69-->Ile (IRT-3) in 6 strains, Met-69-->Leu associated with Asn-276-->Asp (IRT-4) in 13 strains, and Met-69-->Val associated with Asn-276-->Asp (TEM-36) in 12 strains. A new combination, Met-69-->Ile with Asn-276-->Asp, was found in 20 strains and was called IRT-8. Two IRT enzymes not previously described were characterized. The substitution Met-69-->Val associated with a novel substitution Arg-275-->Leu occurred in one strain. The combination Met-69-->Leu and Asn-276-->Asp was associated with the novel substitution Trp-165-->Arg in two strains. These two novel enzymes were called IRT-9 and IRT-10, respectively. The implication of these novel mutated positions, 165 and 275, in resistance to inactivation by clavulanate was supported by crystallographic data on the TEM-1 enzyme and results of site-directed mutagenesis. Molecular characterization of these mutants showed great diversity among the genes coding for inhibitor-resistant TEM enzymes produced by clinical E. coli isolates.
Amoxicillin pharmacokinetics in preterm infants with gestational ages of less than 32 weeks
Authors: Huisman-de Boer J J , van den Anker J N , Vogel M , Goessens W H , Schoemaker R C , de Groot R
Published: June 2012

The multiple-dose pharmacokinetics of amoxicillin (AM [administered twice daily in a 25-mg/kg of body weight intravenous dose]) in 17 preterm infants (11 males; gestational age, 29 +/- 1.9 weeks; birth weight, 1,175 +/- 278 g) were evaluated on day 3 of life. Blood samples were collected from an arterial catheter at 0, 0.5, 1, 2, 4, 8, and 12 h after the intravenous dose. A high-performance liquid chromatography method was used to determine AM concentrations in serum. AM pharmacokinetics followed a one-compartment open model. The glomerular filtration rates of all patients were simultaneously studied by means of the 24-h continuous inulin infusion technique. The elimination half-life, apparent volume of distribution, and total body clearance of AM (mean +/- standard deviation) were 6.7 +/- 1.7 h, 584 +/- 173 ml, and 62.4 +/- 23.3 ml/h, respectively. The mean (+/- standard deviation) AM peak and trough levels were 53.6 +/- 9.1 and 16.0 +/- 4.9 mg/liter, respectively. All infants had a serum trough level above 5 mg/liter. The total body clearance and apparent volume of distribution of AM and the clearance of inulin increased significantly with increasing gestational age. The total body clearance of AM (1.0 +/- 0.4 ml/min) and the clearance of inulin (1.0 +/- 0.3 ml/min) were similar. The total body clearance of AM increased significantly with increasing clearance of inulin. We conclude that an AM dose of 25 mg/kg every 12 h given to preterm infants in the first week of life with gestational ages of less than 32 weeks results in serum levels well above the MIC for major microorganisms involved in neonatal infections.
In vitro activity of the benzoxazinorifamycin KRM-1648 against drug-susceptible and multidrug-resistant tubercle bacilli
Authors: Luna-Herrera J , Reddy M V , Gangadharam P R
Published: June 2012

We investigated the activity of benzoxazinorifamycin (KRM-1648) against several drug-susceptible and multidrug-resistant strains of tubercle bacilli. Since KRM-1648 is a rifamycin derivative, we included some strains of Mycobacterium tuberculosis resistant to rifampin (RIF) among the multidrug-resistant strains. For RIF-susceptible strains, the MIC of KRM-1648 was much lower than that of RIF (MICs of KRM-1648 and RIF at which 90% of strains are inhibited, < or = 0.015 and < or = 0.25 micrograms/ml, respectively). The MBC of KRM-1648 (range, 0.007 to 0.03 microgram/ml) was also much lower than that of RIF (range, 0.5 to 1.0 microgram/ml). Postantibiotic effect studies with KRM-1648 showed a rapid reduction in the CFU counts with an exposure of 24 h or more, and its sterilizing effect was maintained even up to 21 days thereafter. Parallel postantibiotic effect studies with RIF showed a less significant effect with a faster recovery of growth, and RIF failed to sterilize the organisms even after 72 h of exposure. KRM-1648 at 0.125 and 0.25 microgram/ml caused complete inhibition of intracellular growth of M. tuberculosis in J774 A.1 macrophages after 48 h of exposure. After a similar exposure time RIF at a concentration of 0.25 microgram/ml caused complete inhibition of growth, but a concentration of 0.125 microgram/ml caused only a 50% reduction in growth compared with that of controls at day 7. With 24 h of pulsed exposure of the intracellular organisms to 0.25 micrograms of the drugs per ml, KRM-1648 caused complete inhibition of intracellular growth, while RIF caused only moderate inhibition of intracellular growth. These findings suggest that KRM-1648 is a potentially useful drug for the treatment of tuberculosis.
Skin uptake, distribution, and elimination of antimony following administration of sodium stibogluconate to patients with cutaneous leishmaniasis
Authors: al Jaser M , el-Yazigi A , Kojan M , Croft S L
Published: June 2012

We examined in this study the pharmacokinetics of Sb in the affected skin and normal skin of patients treated with sodium stibogluconate for cutaneous leishmaniasis and compared the results with those for the blood. The procedure was fully explained, and a written consent was obtained from each of nine patients. After a dose of sodium stibogluconate equivalent to 600 mg of Sb was administered intramuscularly, small skin biopsies were collected under local anesthesia at different time intervals from the circumferences of the lesions and simultaneously from normal skin. Antimony was measured in these biopsies after suitable ashing and processing by flameless atomic absorption spectrophotometry. The means (with standard errors of the means in parentheses) of the peak concentration, time to peak concentration, area under the curve, half-life, and mean residence time in lesions were 5.02 (1.43) micrograms/g, 2.1 (0.4) h, 32.8 (6.1) micrograms.h/g, 6.88 (0.54) h, and 10.4 (1.2) h, respectively, and those in normal skin were 6.56 (2.01) micrograms/g, 2.6 (0.8) h, 44.0 (15.8) micrograms.h/g, 5.44 (0.83) h, and 8.08 (1.34) h, respectively. There was no significant difference in any of these parameters between lesions and normal skin, whereas the differences in peak concentration, half-life, and mean residence time between lesions and whole blood were significant (P < or = 0.05). The penetration of Sb into skin, either affected or normal, as measured by the skin/blood area under the curve ratio appears to be complete, but the disposition is slow compared with that from the blood.
Action of uracil analogs on human immunodeficiency virus type 1 and its reverse transcriptase
Authors: Piras G , Dutschman G E , Im G J , Pan B C , Chu S H , Cheng Y C
Published: June 2012

Three structural analogs of 5-ethyl-1-benzyloxymethyl-6-(phenylthio)uracil (E-BPU) inhibited human immunodeficiency virus type 1 (HIV-1) replication without cytotoxicity in vitro and were more potent than azidothymidine and were as potent as E-BPU. The target of these compounds is HIV-1 reverse transcriptase. Reverse transcriptases resistant to nevirapine (tyrosine at position 181 to cysteine) and TIBO R82150 (leucine at position 100 to isoleucine) are cross resistant to E-BPU analogs. Nevirapine- or TIBO R82150-resistant HIV-1 were cross resistant to E-BPU analogs but were inhibited at concentrations 11- to 135-fold lower than the cytotoxic doses.
Aminoglycoside dosing weight correction factors for patients of various body sizes
Authors: Traynor A M , Nafziger A N , Bertino J S
Published: June 2012

Prior investigations have suggested the use of a dosing weight correction factor of ideal body weight (IBW) plus 40% excess body weight (EBW, where EBW = total body weight [TBW] - IBW) to determine the weight to use for aminoglycoside dosing in morbidly obese (TBW/IBW ratio, > 2) patients. Little data are available to provide dosing information for underweight or moderately obese patients. We investigated aminoglycoside pharmacokinetics in 1,708 patients receiving gentamicin and tobramycin. Patients were stratified into underaverage-weight or overweight weight categories based on both TBW/IBW ratio and body mass index (weight/height2 ratio), which has been shown to correlate with physiologic estimates of body fat. Regression analyses revealed that the TBW/IBW ratio predicts the volume of distribution. Dosing weight correction factors to give equivalent predicted peak aminoglycoside concentrations with a 2-mg/kg loading dose are 1.13 times the TBW for underweight patients and 0.43 times the EBW plus IBW for overweight patients. There were no large differences between the dosing weight correction factors derived from IBW- and body mass index-based classification systems. These data generate useful aminoglycoside dosing weight equations for both underweight and overweight patients.
Fluconazole penetration into the human prostate
Authors: Finley R W , Cleary J D , Goolsby J , Chapman S W
Published: June 2012

Fluconazole concentrations in the serum and prostate of human volunteers undergoing transurethral resection for benign prostatic hypertrophy were measured. There was a high correlation (r = 0.783) between serum (mean = 6.6 micrograms/ml) and tissue (mean = 1.9 micrograms/g) fluconazole concentrations, and these data were used to construct a model for local tissue concentrations.
DNA gyrase mutations in quinolone-resistant clinical isolates of Neisseria gonorrhoeae
Authors: Deguchi T , Yasuda M , Asano M , Tada K , Iwata H , Komeda H , Ezaki T , Saito I , Kawada Y
Published: June 2012

Eight quinolone-resistant clinical isolates of Neisseria gonorrhoeae were shown to carry mutations in their GyrA proteins. Six isolates had a single amino acid change of serine to phenylalanine at the position corresponding to Ser-83 in Escherichia coli. In addition to the change of serine to phenylalanine, two isolates had another change of aspartic acid to asparagine at the position corresponding to Asp-87 in E. coli.