bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of high-level quinolone resistance in Campylobacter jejuni
Authors: Gootz T D , Martin B A
Published: June 2012

High-level resistance to quinolones has previously been shown to occur in Campylobacter spp. both in vitro and in patients treated with quinolones. We have selected isolates that are resistant to quinolones by plating cells from a susceptible C. jejuni strain, UA535, on medium containing nalidixic acid at 32 micrograms/ml. Fluctuation analysis indicated that resistance occurred by mutation at a frequency of 5 x 10(-8) per cell plated. Unlike what is observed with other gram-negative organisms, the nalidixic acid-resistant mutants demonstrated high-level cross-resistance (MIC, greater than or equal to 4 micrograms/ml) to newer quinolones, including ciprofloxacin, norfloxacin, and temafloxacin, yet remained susceptible to coumermycin A1 and several other unrelated antibiotics. Mutants with an identical resistance phenotype could also be selected from UA535 with ciprofloxacin and norfloxacin at a similar frequency. To study the mechanism of quinolone resistance, DNA gyrases were purified from C. jejuni UA535 and two resistant mutants by heparin-agarose and novobiocin-Sepharose chromatography. After the respective enzyme concentrations were adjusted to equivalent units of activity in the DNA supercoiling reaction, the DNA gyrases from the resistant mutants were found to be 100-fold less susceptible than the wild-type enzyme to inhibition by quinolones. Subunit switching experiments with purified A and B subunits from the wild type and one of the quinolone-resistant mutants indicated that an alteration in the A subunit was responsible for resistance. These results show that a single-step mutation can occur in vitro in the gene encoding DNA gyrase in C. jejuni, producing clinically relevant levels of resistance to the newer quinolones.
6-Methoxypurine arabinoside as a selective and potent inhibitor of varicella-zoster virus
Authors: Averett D R , Koszalka G W , Fyfe J A , Roberts G B , Purifoy D J , Krenitsky T A
Published: June 2012

Seven 6-alkoxypurine arabinosides were synthesized and evaluated for in vitro activity against varicella-zoster virus (VZV). The simplest of the series, 6-methoxypurine arabinoside (ara-M), was the most potent, with 50% inhibitory concentrations ranging from 0.5 to 3 microM against eight strains of VZV. This activity was selective. The ability of ara-M to inhibit the growth of a variety of human cell lines was at least 30-fold less (50% effective concentration, greater than 100 microM) than its ability to inhibit the virus. Enzyme studies suggested the molecular basis for these results. Of the seven 6-alkoxypurine arabinosides, ara-M was the most efficient substrate for VZV-encoded thymidine kinase as well as the most potent antiviral agent. In contrast, it was not detectably phosphorylated by any of the three major mammalian nucleoside kinases. Upon direct comparison, ara-M was appreciably more potent against VZV than either acyclovir or adenine arabinoside (ara-A). However, in the presence of an adenosine deaminase inhibitor, the arabinosides of adenine and 6-methoxypurine were equipotent but not equally selective; the adenine congener had a much less favorable in vitro chemotherapeutic index. Again, this result correlated with data from enzyme studies in that ara-A, unlike ara-M, was a substrate for two mammalian nucleoside kinases. Unlike acyclovir and ara-A, ara-M had no appreciable activity against other viruses of the herpes group. The potency and selectivity of ara-M as an anti-VZV agent in vitro justify its further study.
Bactericidal effect of amoxicillin on Helicobacter pylori in an in vitro model using epithelial cells
Authors: Megraud F , Trimoulet pascale  , Lamouliatte H , Boyanova L
Published: June 2012

The treatment of Helicobacter pylori with antimicrobial agents has largely been ineffective, and susceptibility results are in disagreement with those obtained by standard in vitro testing. The bactericidal effect of amoxicillin was tested in an in vitro model by using sessile bacteria attached to HEp-2 cells; this bactericidal effect was compared with that against planktonic bacteria. Viable cell counts were performed by standard procedures after 1, 6, and 24 h of contact with the antibiotic at different concentrations. A bactericidal effect (99.9% killing) was observed against sessile bacteria after 24 h with concentrations of only 10, 1, and 0.1 mg/liter, while against planktonic bacteria it was also noted at concentrations of 0.01 and 0.001 mg/liter, and the effect was observed after 6 h with the three highest concentrations. When the results for five strains were studied by analysis of variance at 6 and 24 h, the main variable was the antibiotic concentration, followed by the culture conditions, e.g., planktonic or sessile bacteria, the strain tested, and the time of contact. A decreased pH of 5.4 did not affect the action of amoxicillin. The bactericidal effect of the combination of amoxicillin and metronidazole was additive against sessile H. pylori.
Pharmacologic basis for high-dose oral acyclovir prophylaxis of cytomegalovirus disease in renal allograft recipients
Authors: Fletcher C V , Englund J A , Edelman C K , Gross C R , Dunn D L , Balfour H H
Published: June 2012

The incidence of cytomegalovirus disease, the most important infectious complication of renal transplantation, was reduced in renal allograft recipients by a regimen of prophylactic high-dose oral acyclovir. To analyze the pharmacologic aspects of our prophylactic approach, we evaluated safety, pharmacodynamics, and in vitro susceptibility data. One hundred four recipients of cadaveric renal allografts received either oral acyclovir (n = 53) in doses of up to 3,200 mg/day or a placebo (n = 51) for 12 weeks posttransplant. Leukocyte count and serum creatinine were selected as markers of laboratory safety and were evaluated pretransplant, at study midpoint (creatinine only), and at study completion. Concentrations of acyclovir in plasma were determined to verify the ability of the dosing strategy to achieve predicted values. Viral resistance was assessed by calculation of in vitro 50% inhibitory concentrations (IC50s) of acyclovir for the cytomegalovirus strains collected from the subjects. Our results showed no difference in leukocyte count or serum creatinine between the acyclovir and placebo recipients. Plasma acyclovir concentrations were maintained within the expected limits and did not differ between patients who developed cytomegalovirus disease and those who did not. The mean acyclovir IC50s for cytomegalovirus isolates were 42.6 mumol/liter in the acyclovir recipients and 48 mumol/liter in the placebo recipients. We conclude that the clinical benefit of high-dose oral acyclovir therapy occurred despite plasma drug concentrations below the mean IC50 for the patient viral isolates. Furthermore, the use of the regimen did not produce leukopenia, adversely affect renal function, or alter the susceptibility of cytomegalovirus strains to acyclovir. This approach and dose adjustment scheme may be appropriate for other immunocompromised patients at risk for cytomegalovirus infection and disease.
Three-dimensional analysis of the synergistic cytotoxicity of ganciclovir and zidovudine
Authors: Prichard M N , Prichard L E , Baguley W A , Nassiri M R , Shipman C
Published: June 2012

The combined cytotoxicity of zidovudine and ganciclovir in three cell lines of human origin was examined. The data were generated by a new rapid cell proliferation assay and a more sensitive plating efficiency assay. A three-dimensional analytical approach was used to evaluate the drug-drug interactions, and the results were compared with those obtained by two conventional methods of analysis. Synergistic cytotoxicity was observed in all cell lines examined and by both assays. Moreover, this synergistic cytotoxicity was statistically significant at physiologically relevant concentrations. It is not known whether these drug-drug interactions manifest themselves in vivo as granulocytopenia or other untoward side effects. These results, however, indicate that further investigation is warranted and that the coadministration of zidovudine and ganciclovir may be contraindicated.
Evidence that amikacin ototoxicity is related to total perilymph area under the concentration-time curve regardless of concentration
Authors: Beaubien A R , Ormsby E , Bayne A , Carrier K , Crossfield G , Downes M , Henri R , Hodgen M
Published: June 2012

Previous studies have failed to fully establish whether ototoxicity is related in any way to the levels of an aminoglycoside antibiotic in the perilymph. To study this we exposed guinea pigs to continuously infused amikacin at four different dosing rates under conditions parallel to those used in our previous study which related ototoxicity to total plasma area under the concentration-time curve regardless of the level in plasma. It was found that at all dosing rates, levels in the perilymph and ratios of levels in perilymph/plasma remained constant as the dosing duration increased from nonototoxic to strongly ototoxic. Plasma and perilymph amikacin levels were found to be linear functions of the dosing rate even at ototoxic dosing exposures, and ratios of levels in perilymph/plasma did not differ between dosing rates. The total perilymph area under the concentration-time curve was not different between dosing rates either for a total dose associated with threshold ototoxicity or for one associated with severe ototoxicity. The results suggest that amikacin ototoxicity is related to the integral of the concentration in the perilymph over the total time of amikacin exposure regardless of the level in the perilymph.
Comparative effect of protein binding on the killing activities of teicoplanin and vancomycin
Authors: Bailey E M , Rybak M J , Kaatz G W
Published: June 2012

The effect of protein binding on the activity of teicoplanin against Staphylococcus aureus was evaluated. Bactericidal rates of teicoplanin in cation-supplemented Mueller-Hinton broth (SMHB) and in a 1:1 mixture of pooled human serum and cation-supplemented Mueller-Hinton broth (PHS-SMHB) were compared with those of vancomycin. Eight concentrations of each drug ranging from 15 to 150 micrograms/ml were studied in two series which correspond to the concentrations in serum achieved with low- (6 mg/kg of body weight once daily) and high-dose (30 mg/kg once daily) teicoplanin. Overall, the bactericidal rate of teicoplanin was lower than that of vancomycin. In the presence of serum, the bactericidal rate of teicoplanin in PHS-SMHB was lower than that in SMHB, often resulting in only one log10 drop in CFU over a 24-h period. There was no statistical difference in the bactericidal rates of high- and low-concentration teicoplanin in either medium. Additionally, concentration-dependent killing in SMHB was not evident with either agent. The bactericidal rates of teicoplanin and vancomycin in a 1:1 mixture of serum ultrafiltrate and SMHB at 60 micrograms/ml were also studied. It was noted that the bactericidal rate of neither agent was affected by the presence of serum ultrafiltrate. This finding is consistent with teicoplanin's high degree of protein binding (reported to be greater than 90% in undiluted serum) and further substantiates the hypothesis that only the free drug is active against microorganisms. These data support protein binding as being a factor in teicoplanin activity against S. aureus.
Comparative efficacy and safety of cefprozil (BMY-28100) and cefaclor in the treatment of acute group A beta-hemolytic streptococcal pharyngitis
Authors: Christenson J C , Swenson E , Gooch W M , Herrod J N
Published: June 2012

Cefprozil (BMY-28100) is a semisynthetic cephalosporin with broad-spectrum antibacterial activity and prolonged serum elimination half-life allowing for once-a-day oral administration. In vitro, cefprozil demonstrates excellent activity against Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. Cefprozil (500 mg once daily) was compared to cefaclor (250 mg three times daily) in an open, randomized, comparative trial for the treatment of acute group A beta-hemolytic streptococcal pharyngitis. Ninety-four patients were enrolled in this study; 53 patients were evaluable for clinical and bacteriological response assessment. Seventy-eight patients were evaluable for safety assessment. Three patients (all in the cefprozil treatment group) required disenrollment because of side effects, mainly nausea. Clinical and bacteriological responses were comparable for both study drugs. Leukopenia and nausea, the most common side effects observed, were more common in the cefprozil-treated group. Cefprozil appears to be an appropriate alternative to cefaclor for the treatment of acute group A beta-hemolytic streptococcal pharyngitis. However, because of the small number of patients eligible for efficacy assessment, a large type II (beta) error was expected in our study, which may have resulted in a potential failure to detect a difference between both treatment groups. A larger study would be required to determine the proper role of cefprozil in the treatment of group A beta-hemolytic streptococcal infections.
Characterization of the gentamicin resistance transposon Tn5281 from Enterococcus faecalis and comparison to staphylococcal transposons Tn4001 and Tn4031
Authors: Hodel-Christian S L , Murray B E
Published: June 2012

In Enterococcus faecalis, the genetic determinant encoding gentamicin resistance (Gmr) on the conjugative plasmid pBEM10 previously has been shown to be on a mobile element. In the current study, this element, termed Tn5281, was shown to relocate in the absence of homologous recombination in E. faecalis UV202. On the basis of restriction endonuclease analysis and DNA-DNA hybridization studies, Tn5281 was shown to be similar, if not identical, to the Gmr transposons Tn4001 found in Australian isolates of Staphylococcus aureus and Tn4031 found in U.S. isolates of Staphylococcus epidermidis, since all three of these transposons have symmetrically located HindIII (2.5 kb apart), ClaI (slightly more than 2.5 kb apart), and HaeIII (3.9 kb apart) sites. Restriction endonuclease digestion patterns of Tn5281 generated with HincII, ScaI, and AluI were also consistent with Tn4001 and Tn4031. By using a probe specific for the external portion of the terminal inverted repeat of Tn4031, it was determined that each terminus of Tn5281 contained a 0.35-kb HaeIII fragment and a 0.7-kb HindIII-HaeIII fragment. The sizes of these fragments are identical to those found in the staphylococcal transposons, which is a further indication that inverted repeats like IS256 are present in Tn5281. A 1-kb HaeIII fragment in pBEM10 also hybridized with this probe, which indicates that Tn5281 in pBEM10 contains a double copy of the inverted repeat at one end.
Increased susceptibility to beta-lactam antibiotics and decreased porin content caused by envB mutations of Salmonella typhimurium
Authors: Oppezzo O J , Avanzati B , Antón D N
Published: June 2012

Isogenic derivatives carrying envB6, envB9, or envB+ alleles were obtained from a strain of Salmonella typhimurium that was partially resistant to mecillinam, a beta-lactam antibiotic specific for penicillin-binding protein 2 (PBP 2). Testing of the isogenic strains with several antibacterial agents demonstrated that envB mutations either increased resistance (mecillinam) or did not affect the response (imipemen) to beta-lactams that act primarily on PBP 2, while susceptibilities to beta-lactams that act on PBP 1B, PBP 3, or both were increased. Furthermore, the susceptibilities of envB strains to hydrophobic compounds such as rifampin, novobiocin, or chloramphenicol were not modified, even though their susceptibilities to deoxycholate and crystal violet were enhanced. Outer cell membranes of envB mutants presented a 50% reduction in protein content compared with that of the isogenic envB+ strains, and OmpF and OmpD porins were particularly affected by the reduction. No alteration in the amount or pattern of periplasmic proteins was noticed, and lipopolysaccharides from envB mutants appeared to be normal by sodium dodecyl sulfate-urea-polyacrylamide gel electrophoresis. By using derivatives that produced a plasmid-encoded beta-lactamase, it was demonstrated that envB cells are slightly less permeable to cephalothin than envB+ bacteria are. It is concluded that the high susceptibility of envB mutants to beta-lactams is due to the increased effectiveness of the antibiotics on PBP 1B, PBP 3, or both.
Susceptibilities of 394 Bacteroides fragilis, non-B. fragilis group Bacteroides species, and Fusobacterium species to newer antimicrobial agents
Authors: Appelbaum P C , Spangler S K , Jacobs M R
Published: June 2012

The susceptibilities of 374 selected beta-lactamase-producing gram-negative anaerobes (including 22 cefoxitin-resistant strains and 36 strains refractory to the enhancing effect of beta-lactamase inhibitors) and 20 beta-lactamase-negative strains were tested by agar dilution against selected new agents. The organisms included 217 Bacteroides fragilis group strains, 137 non-B. fragilis group Bacteroides spp., and 40 fusobacteria. All strains were susceptible to piperacillin-tazobactam, imipenem, and meropenem. For the B. fragilis group, 96% were susceptible to ampicillin-sulbactam, 95% were susceptible to amoxicillin-clavulanate and cefoperazone-sulbactam, 94% were susceptible to tosufloxacin, 91% were susceptible to cefoxitin, 88% were susceptible to trospectomycin, and 73% were susceptible to cefotetan. For the beta-lactamase-positive non-B. fragilis group Bacteroides spp., greater than or equal to 94% were susceptible to cefoxitin, amoxicillin-clavulanate, ampicillin-sulbactam, cefoperazone-sulbactam, and trospectomycin, 90% were susceptible to cefotetan, and 85% were susceptible to tosufloxacin (the most resistant strains were B. bivius and B. disiens). For the beta-lactamase-positive fusobacteria, greater than or equal to 97% were susceptible to amoxicillin-clavulanate, ampicillin-sulbactam, cefoperazone-sulbactam, trospectomycin, and cefoxitin, 90% were susceptible to cefotetan, and 89% were susceptible to tosufloxacin. All agents showed excellent activity against beta-lactamase-negative strains (for trospectomycin, 95% were susceptible; for all other drugs, 100% were susceptible). Overall, both carbapenems and piperacillin-tazobactam were most active. Amoxicillin-clavulanate, ampicillin-sulbactam, and cefoperazone-sulbactam lacked activity against some cefoxitin-resistant B. fragilis group strains but had excellent activity against other organisms. Tosufloxacin, a new quinolone, had very good activity against B. fragilis group strains (94% susceptible), good activity against other beta-lactamase-positive strains (less than or equal 85% susceptible), and excellent activity against beta-lactamase-negative strains (100% susceptible; MIC for 90% of strains, 0.5 microgram/ml). Trospectomycin was active against >90% of all strains except for B. fragilis group strains (88% susceptible; MIC for 90% of strains, 32 microgram/ml). Clinical studies are required to delineate the role of newer agents in the therapy of anaerobic infections.
In vitro activity of metronidazole against Helicobacter pylori as determined by agar dilution and agar diffusion
Authors: Knapp C C , Ludwig M D , Washington J A
Published: June 2012

Metronidazole activity against 25 clinical isolates of Helicobacter pylori was evaluated by agar dilution, epsilometer (E-test; AB Biodisk, Solna, Sweden), and disk diffusion methods after 3 and 5 days of incubation in a microaerophilic atmosphere. Agar dilution, performed in duplicate, provided reproducible results with MICs for 50% of the isolates of less than or equal to 0.12 microgram/ml after 3 and 5 days of incubation and MICs for 90% of the isolates of 2 and 4 micrograms/ml after 3 and 5 days of incubation, respectively. Reproducibility of MICs was slightly better after 5 days than after 3 days of incubation. MICs obtained with the E-test were higher, with 76 and 68% of isolates inhibited by less than or equal to 16 micrograms of metronidazole per ml after 3 and 5 days, respectively, in contrast with corresponding values of 92 and 88% for agar dilution. Zone diameters obtained with the commercially available 80-micrograms metronidazole elution disk were too large (greater than or equal to 41 mm) to allow discrimination between susceptible and resistant isolates, although resistant subpopulations were detected by the appearance of inner colonies in four isolates. In conclusion, the E-test was easy to perform and interpret, and it appeared to be more likely than agar dilution to detect metronidazole resistance in vitro in H. pylori.
Accidental overdose of intravenous ofloxacin with benign outcome
Authors: Kohler R B , Arkins N , Tack K J
Published: June 2012

A patient accidentally received approximately 3 g of ofloxacin intravenously. She experienced only moderately severe central nervous system symptoms, which resolved within 9 h. The peak serum ofloxacin level was 39.3 micrograms/ml, approximately seven times the usual peak level. Ofloxacin may possess a considerable safety margin in humans.
Efficacy of Different β-Lactams against an Extended-Spectrum β-Lactamase-Producing
Klebsiella pneumoniae
Strain in the Rat Intra-Abdominal Abscess Model
Authors: Rice Louis B. , Yao Joseph D. C. , Klimm Karin , Eliopoulos George M. , Moellering Robert C.
Published: June 2012

Although standard-inoculum MICs were within the susceptible range for all compounds, cefoperazone, cefotaxime, and cefpirome were significantly less effective than imipenem or the combination of cefoperazone and sulbactam in the treatment of rat intra-abdominal abscesses due to an extended-spectrum β-lactamase-producing strain of
Klebsiella pneumoniae
.
Molecular cloning, purification, and properties of a plasmid-encoded chloramphenicol acetyltransferase from Staphylococcus haemolyticus
Authors: Schwarz S , Cardoso M
Published: June 2012

A small chloramphenicol resistance (Cmr) plasmid of approximately 3.75 kb, designated pSCS5, was isolated from Staphylococcus haemolyticus. This plasmid encoded an inducible chloramphenicol acetyltransferase (CAT; EC 2.3.1.28). The cat gene of pSCS5 was cloned into the Escherichia coli plasmid vector pBluescript SKII+. It differed in its nucleotide sequence and deduced amino acid sequence from the cat genes described previously in staphylococci and other gram-positive bacteria. The CAT enzyme was purified from cell-free lysates by ammonium sulfate precipitation, ion-exchange chromatography, and fast protein liquid chromatography. The native enzyme had an Mr of 70,000 and was composed of three identical subunits, each with an Mr of approximately 23,000. Its isoelectric point was at pH 6.15. CAT from pSCS5 exhibited Km values of 2.81 and 51.8 microM for chloramphenicol and acetyl coenzyme A, respectively. The optimum pH for activity was 7.8. CAT encoded by pSCS5 proved to be relatively heat stable, but sensitive to mercury ions. The observed differences in the nucleotide sequence and the biochemical characteristics of the enzyme allowed the identification of the pSCS5-encoded CAT from S. haemolyticus as a CAT variant different from those described previously in gram-positive bacteria.
Limited protection by small unilamellar liposomes against the renal tubular toxicity induced by repeated amphotericin B infusions in rats
Authors: Longuet P , Joly V , Amirault P , Seta N , Carbon C , Yeni P
Published: June 2012

Amphotericin B (AMB), either alone or incorporated into small unilamellar vesicles of pure dipalmitoylphosphatidyl choline (DPPC SUV-AMB), was administered intravenously to male Sprague-Dawley rats once daily for 5 days. Either 1.5 or 3.5 mg of AMB or DPPC SUV-AMB per kg was given, since these concentrations corresponded, respectively, to the lowest nephrotoxic dose and the sublethal dose of AMB in our model. Tubular functions were evaluated daily, and AMB concentrations in plasma, urine, and tissues were measured by high-performance liquid chromatography. AMB at both doses induced tubular toxicity, hyposthenuria being the earliest symptom. DPPC SUV-AMB at 1.5 mg/kg/day was atoxic, but the tubular alterations induced by 3.5 mg of DPPC SUV-AMB per kg were similar to those observed with 3.5 mg of AMB per kg, except that the ability to concentrate urine was partly restored 72 h after the last infusion. Incorporating AMB into DPPC SUV did not influence the pharmacokinetics of the drug. Using this lipidic AMB formulation, we thus observed a beneficial effect toward limiting the renal tubular toxicity of repeated low doses of AMB but, unexpectedly, not that of high doses. These results indicate that tubular renal functions and electrolyte serum values should be closely monitored in patients treated with AMB liposomal formulations, especially high-dose regimens.
Interaction of aminoglycosides with the outer membranes and purified lipopolysaccharide and OmpF porin of Escherichia coli
Authors: Hancock R E , Farmer S W , Li Z S , Poole K
Published: June 2012

The mechanism of uptake of aminoglycosides across the outer membrane of Escherichia coli was reevaluated. Porin-deficient mutants showed no alteration in gentamicin or kanamycin susceptibility. Furthermore, the influence of kanamycin on intrinsic tryptophan fluorescence of porin OmpF (Y. Kobayashi, and T. Nakae, Eur. J. Biochem. 151:231-236, 1985) was shown to be strongly influenced by protein concentration and EDTA. This led to the hypothesis that aminoglycoside-mediated increases and decreases in intrinsic tryptophan fluorescence were due to aggregation-disaggregation of OmpF mediated by interaction at a divalent cation binding site on OmpF. Gentamicin, kanamycin, and polymyxin B increased E. coli outer membrane permeability to the hydrophobic fluorescent compound 1-N-phenyl-naphthylamine (NPN) and the peptidoglycan-degrading enzyme lysozyme. Addition of Mg2+ blocked these permeabilizing activities. Furthermore, gentamicin and polymyxin B bound to Mg(2+)-binding sites on E. coli lipopolysaccharide, as determined in dansyl polymyxin displacement experiments. A polymyxin-resistant, lipopolysaccharide-altered pmr mutant of E. coli had a fourfold-lower MIC of gentamicin and kanamycin and was more poorly permeabilized to 1-N-phenylnaphthylamine than was its parent strain. These data were consistent with uptake of aminoglycosides across the E. coli outer membrane by the self-promoted uptake mechanism.
5'-Alkyl-substituted analogs of 5'-methylthioadenosine as trypanocides
Authors: Bacchi C J , Sufrin J R , Nathan H C , Spiess A J , Hannan T , Garofalo J , Alecia K , Katz L , Yarlett N
Published: June 2012

5'-Deoxy-5'-(methylthio)adenosine (MTA) is a by-product of polyamine metabolism and is phosphoryolytically cleaved to adenine and 5-deoxy-5-(methylthio)ribose-1-phosphate (MTR-1-P) by MTA phosphorylase. In eukaryotes, adenine is subsequently salvaged and converted to nucleotides, while MTR-1-P is converted to methionine. We examined 5'-deoxy-5'-substituted analogs of MTA for trypanocidal activity in vitro and in vivo. 5'-Deoxy-5'-(hydroxyethyl)thioadenosine (HETA) and its 5'-bromo,5'-chloro and 5'-fluoro derivatives were cleaved by extracts of the African trypanosome Trypanosoma brucei brucei (Km for MTA, 11.5 microM; Km for HETA, 13.2 microM) in a phosphate-dependent reaction. HETA and the three halo analogs were 50% inhibitory to growth at 0.5 to 5.0 microM in vitro. Inhibition of growth was reversible by exogenous methionine and 2-keto-4-methylthiobutyric acid, an intermediate in methionine synthesis from MTR-1-P. HETA was selected for further study in vivo. When administered by miniosmotic pump (25 to 150 mg/kg/day for 7 days) to mice infected with T. brucei brucei, HETA effected 70 to 90% cure rates. Results of this study indicate that these analogs of MTA are converted to trypanocidal MTR-1-P analogs and that this approach deserves further consideration in the development of novel chemotherapy of trypanosomiasis.
In vitro and in vivo potentiation of chloroquine against malaria parasites by an enantiomer of amlodipine
Authors: Deloron P , Basco L K , Dubois B , Gaudin C , Clavier F , Le Bras J , Verdier F
Published: June 2012

A combination of chloroquine and amlodipine, a derivative of 1,4-dihydropyridine calcium channel blocker, was tested against Plasmodium falciparum in vitro and P. yoelii in mice. The dextrorotary enantiomer of amlodipine, practically devoid of calcium channel blocking action, increased chloroquine accumulation inside the infected mouse erythrocytes and potentiated chloroquine action against the resistant strains of P. falciparum in vitro and P. yoelii in mice. Unlike the racemate, the dextrorotary amlodipine was not toxic to the host animal, even at the highest dose of 250 mg/kg. No potentiating effect was noted in the chloroquine-susceptible strains of P. falciparum. The results of this study indicate that chloroquine potentiation of amlodipine is probably independent of calcium channels and that a combination therapy of the dextrorotary enantiomer of amlodipine and chloroquine might be a potentially useful therapeutic strategy against chloroquine-resistant falciparum malaria.
Pharmacokinetics of cefotaxime and desacetylcefotaxime in patients with liver disease
Authors: Ko R J , Sattler F R , Nichols S , Akriviadis E , Runyon B , Appleman M , Cohen J L , Koda R T
Published: June 2012

The dispositions of cefotaxime and its metabolite desacetylcefotaxime were investigated in patients with different forms of chronic parenchymal liver disease (CPLD). A total of 31 subjects (27 patients and 4 controls) received a single 2-g dose of cefotaxime by infusion, and serial blood samples were drawn. The area under the concentration-time curve ranged from 176 to 241 micrograms.h/ml, the apparent half-life ranged from 1.49 to 2.42 h, and clearance ranged from 2.06 to 3.10 ml/min/kg in patients with four different forms of CPLD. The area under the concentration-time curve and the apparent half-life of desacetylcefotaxime ranged from 72 to 128 micrograms.h/ml and 7.1 to 13.4 h, respectively. Pharmacokinetic parameters were significantly different in patients with CPLD compared with those in control subjects and were related to clinical indices of hepatic impairment. Modest accumulation of cefotaxime in patients with severe hepatic impairment is unlikely to produce toxicity because of its high therapeutic index, and dosing modifications may not be required.
Lytic effect of two fluoroquinolones, ofloxacin and pefloxacin, on Escherichia coli W7 and its consequences on peptidoglycan composition
Authors: Vincent S , Glauner B , Gutmann L
Published: June 2012

Examination of biochemical changes in Escherichia coli W7 after exposure to ofloxacin or pefloxacin revealed distinct concentration-dependent responses. At levels close to the MIC, extensive filamentation was followed by a lytic event, which involved an active protein synthesis. This lysis was correlated with changes in the peptidoglycan composition, particularly a decrease in the average glycan chain length, involving the action of the autolysines. At higher concentrations, no lysis occurred and the growth was totally inhibited as well as the protein synthesis. The peptidoglycan composition exhibited an increase in the average glycan chain length, suggesting an apparent reduced activity of the lytic transglycosylase. These results show that exposure to low concentrations of quinolones leads to the induction of lysis and peptidoglycan modifications which might contribute to the bactericidal effects of quinolones.
Anti-human immunodeficiency virus type 1 activity and in vitro toxicity of 2'-deoxy-3'-thiacytidine (BCH-189), a novel heterocyclic nucleoside analog
Authors: Soudeyns H , Yao X I , Gao Q , Belleau B , Kraus J L , Nguyen-Ba N , Spira B , Wainberg M A
Published: June 2012

We describe a novel nucleoside analog, 2'-deoxy-3'-thiacytidine (BCH-189), in which the 3' carbon of the ribose ring of 2'-deoxycytidine has been replaced by a sulfur atom. In MT-4 T cells, this compound had significant time- and dose-dependent antiviral activity against five different strains of human immunodeficiency virus type 1 (HIV-1) (mean 50% inhibitory dose, 0.73 microM); known 3'-azido-3'-deoxythymidine (AZT)-resistant HIV-1 variants did not exhibit cross-resistance to it. BCH-189 also suppressed HIV-1 replication in the U937 monocytoid cell line as well as in primary cultures of human peripheral blood mononuclear cells; in these latter systems, suppression was fuller and longer lasting than that induced by AZT. Moreover, BCH-189 was less toxic than AZT in cell culture. BCH-189 may be a promising drug for the treatment of HIV-1-associated disease.
Bactericidal effects of ticarcillin-clavulanic acid against Legionella pneumophila pneumonia in immunocompromised weanling rats
Authors: Smith G M , Abbott K H , Wilkinson M J , Beale A S , Sutherland R
Published: June 2012

A model of acute Legionella pneumophila pneumonia in neutropenic weanling rats was developed as a means of assessing the efficacies in vivo of the beta-lactams ticarcillin, ticarcillin-clavulanic acid, and clavulanic acid, agents active against the organism in vitro. Weanling rats were dosed with cyclophosphamide 3 days before and immediately prior to infection by intrabronchial intubation with L. pneumophila. The bacteria persisted in the lungs of untreated animals at high counts (5.0 to 7.0 log10 CFU/g of lung tissue) for up to 168 h after infection, and the histological characteristics of the infection were similar to those of the disease in humans. Transmission electron micrography revealed the presence of L. pneumophila multiplying within alveolar macrophages. Therapy with ticarcillin was ineffective in reducing the bacterial numbers in the lung tissue, whereas ticarcillin-clavulanic acid and clavulanic acid were active, producing bactericidal effects similar to those of erythromycin. The ticarcillin-clavulanic acid combination was significantly more efficacious (P less than 0.01) than corresponding doses of clavulanic acid alone. Synergistic activity between ticarcillin and clavulanic acid against L. pneumophila has been demonstrated in vivo, and the combination showed activity similar to that of erythromycin.
Synergistic inhibition of human immunodeficiency virus type 1 replication by 5-ethyl-1-ethoxymethyl-6-(phenylthio)uracil (E-EPU) and azidothymidine in vitro
Authors: Baba M , Ito M , Shigeta S , Tanaka H , Miyasaka T , Ubasawa M , Umezu K , Walker R T , De Clercq E
Published: June 2012

A novel 6-substituted acyclouridine derivative, 5-ethyl-1-ethoxymethyl-6-(phenylthio)uracil (E-EPU), has recently proved to be a highly potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) in vitro. Combinations of 3'-azido-2',3'-dideoxythymidine (AZT) and E-EPU synergistically inhibit the replication of HIV-1 in MT-4 cells, whereas the cytotoxic effects of AZT and E-EPU on mock-infected MT-4 cells are not enhanced by the drug combination. Synergistic inhibition of HIV-1 replication has also been observed in peripheral blood lymphocytes. These results indicate that the combination of AZT and E-EPU should be further pursued in the treatment of AIDS.
Aerosol and intraperitoneal administration of ribavirin and ribavirin triacetate: pharmacokinetics and protection of mice against intracerebral infection with influenza A/WSN virus
Authors: Gilbert B E , Wyde P R , Wilson S Z , Robins R K
Published: June 2012

Ribavirin is active in vitro but not in vivo against a number of viruses capable of causing encephalitis. Ribavirin triacetate (RTA), a lipophilic derivative, has been reported to be more effective than ribavirin in protecting animals from encephalitis. By using an influenza A/WSN virus encephalitis model, we demonstrated that RTA administered by small-particle aerosol was able to decrease the death rate and increase the time of survival. To determine if this beneficial effect was due to increased delivery of drug, the pharmacokinetic properties of ribavirin and RTA when administered as an aerosol or by intraperitoneal injection were examined. Aerosol administration of ribavirin or RTA gave significantly higher concentrations of ribavirin in the lungs and serum of mice than did intraperitoneal injection. There was no difference, however, in ribavirin levels when either ribavirin or RTA was administered by small-particle aerosol. In brain tissue, ribavirin concentrations increased with time and did not appear to decrease as rapidly as in lungs and serum. Mean peak ribavirin concentrations in the brain were higher following aerosol administration of ribavirin than RTA, and both were higher than that following intraperitoneal injection of either drug. Administration of ribavirin or RTA by intraperitoneal injection failed to protect mice from a lethal intracerebral inoculation of influenza A/WSN virus, while aerosolized RTA did protect mice. The pharmacokinetics of ribavirin in brain tissue following aerosol administration of either drug did not explain the advantage of RTA over ribavirin in protecting mice from intracerebral infection with influenza A/WSN virus.
Identification of CTX-2, a novel cefotaximase from a Salmonella mbandaka isolate
Authors: Poupart M C , Chanal C , Sirot D , Labia R , Sirot J
Published: June 2012

A strain of Salmonella mbandaka isolated from the feces of an Algerian infant showed a reduced susceptibility to cefotaxime (MIC, 8 mg/liter). This strain produced two transferable beta-lactamases of pIs 5.3 and 5.6. The novel beta-lactamase with a pI of 5.3 inhibited by clavulanic acid showed cefotaxime hydrolysis and was therefore designated CTX-2.
In vitro comparison of GR69153, a novel catechol-substituted cephalosporin, with ceftazidime and ceftriaxone against 5,203 recent clinical isolates
Authors: Washington J A , Jones R N , Allen S D , Gerlach E H , Koontz F P , Murray P R , Pfaller M A , Erwin M E
Published: June 2012

The activity of GR69153, a novel catechol-substituted cephalosporin, was compared with those of ceftazidime and ceftriaxone in a multicenter study against 5,203 fresh clinical isolates of gram-negative and gram-positive bacteria. GR69153 was generally very active at concentrations equivalent to or two- to fourfold lower than those of ceftazidime and ceftriaxone against gram-negative bacilli other than Citrobacter freundii, Enterobacter cloacae, and Xanthomonas maltophilia. Against Pseudomonas aeruginosa, MICs of GR69153 and ceftazidime for 50% of isolates tested (MIC50s) were, respectively, 1 and 2 micrograms/ml; the corresponding MIC90s were 4 and 16 micrograms/ml. Although MIC50s of GR69153 for staphylococci were two- to eightfold lower than those of ceftazidime or ceftriaxone, MIC90s against staphylococci and enterococci were greater than or equal to 16 micrograms/ml for all three compounds. Quality control MIC ranges for reference strains are proposed for the broth microdilution method on the basis of the GR69153 data derived from this multicenter study.
Antiviral activity of oxetanocins against varicella-zoster virus
Authors: Sakuma T , Saijo M , Suzutani T , Yoshida I , Saito S , Kitagawa M , Hasegawa S , Azuma M
Published: June 2012

Several new nucleosides with an oxetanosyl-N-glycoside group, named oxetanocins, were evaluated for their antiviral activities against varicella-zoster virus (VZV) in human embryo lung cells. 9-(2-deoxy-2-hydroxy-methyl-beta-D-erythro-oxetanosyl)guanine (OXT-G) and 9-(2-deoxy-2-hydroxymethyl-beta-D-erythro-oxetanosyl)-2- aminoadenine were effective against not only thymidine kinase-positive (TK+) VZV (YS strain) but also thymidine kinase-negative (TK-) VZV (YSR strain), whereas carbocyclic OXT-G was effective against TK+ VZV but not against TK- VZV. [3H]OXT-G was incorporated into TK+ VZV-infected cells and TK- VZV-infected cells more than into mock-infected cells and was converted into the triphosphate form.
Comparative study of various hydrogen ion buffers to assay Zn(2+)-dependent beta-lactamases
Authors: Benitez M J , Company M , Arevalillo A , Jiménez J S
Published: June 2012

The low Zn2+ complex formation constants, the capacity to degrade penicillin G in combination with Zn2+, and UV absorbance make 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid, 1,3-bis[tris(hydroxymethyl)methylamino]propane, and 1,4-piperazinediethanesulfonic acid convenient buffers to study Zn(2+)-dependent beta-lactamases.
Interactions of amphotericin B and SCH 39304 in the treatment of experimental murine candidiasis: lack of antagonism of a polyene-azole combination
Authors: Sugar A M
Published: June 2012

Mice infected intravenously with Candida albicans were treated with SCH 39304, a new triazole antifungal compound, amphotericin B, or both. Two dose levels of each drug were evaluated in an attempt to identify potential helpful or harmful effects on survival and kidney colony counts. Contrary to theoretical predictions, combination therapy was not antagonistic and some additive or synergistic effects were observed. The results obtained in this study suggest that antagonism between polyene and azole antifungal drugs is not inevitable and that additive or synergistic effects may be possible.
Activity of new quinolones against ciprofloxacin-resistant staphylococci
Authors: Forstall G J , Knapp C C , Washington J A
Published: June 2012

Because of the development of newer fluoroquinolones with improved activity against gram-positive organisms, we elected to compare the inhibitory properties of ofloxacin, temafloxacin, sparfloxacin, PD131628, PD127391, and WIN57273 against 105 ciprofloxacin-resistant staphylococci. Based on comparison of MICs for 90% of the organisms (MIC90s), WIN57273 was the most active agent against oxacillin-resistant Staphylococcus aureus; the MIC90 was 0.5 microgram/ml. Against oxacillin-resistant, coagulase-negative staphylococci, PD127391 and WIN57273 were the most active agents; the MIC90 was 0.5 microgram/ml. Against isolates of staphylococci for which ciprofloxacin MICs were greater than or equal to 32 micrograms/ml, WIN57273 and PD127391 still exhibited high activity, inhibiting 100 and 95% of the isolates, respectively, at 2 micrograms/ml. The spontaneous mutation rates for ciprofloxacin-susceptible staphylococci were lowest for ofloxacin. The frequency of spontaneous mutations of ciprofloxacin-resistant staphylococci was low; however, the MICs of PD127391 and WIN57273 for these mutant isolates were greater than 2 micrograms/ml. WIN57273 and PD127391 are two potent new quinolones with high levels of activity against highly ciprofloxacin-resistant staphylococci. There is, however, a major concern of selection of spontaneous mutants resistant to these newer agents.
Ofloxacin and penicillin G combination therapy in prevention of bacterial translocation and animal mortality after irradiation
Authors: Brook I , Ledney G D
Published: June 2012

The efficacies of 40 mg of ofloxacin per kg/day given orally and 250 mg of penicillin per kg/day given intramuscularly, alone or in combination, were evaluated in the prevention of mortality of C3H/HeN female mice given 8.2 Gy of 60Co radiation. Mortalities were 51 of 60 mice (85%) in the control group, 46 of 60 mice (77%) among those treated with penicillin, 32 of 60 mice (53%) among those treated with ofloxacin (P less than 0.05), and 5 of 60 mice (8%) among those treated with ofloxacin and penicillin (P less than 0.001). The organisms recovered from the livers of control mice were members of the family Enterobacteriaceae and Streptococcus spp. A reduction in the number of the Enterobacteriaceae was noted only in ofloxacin-treated mice, and a reduction in the number of Streptococcus spp. was noted only in the penicillin-treated mice. Reductions in the numbers of both groups of organisms were noted only in the animals treated with both agents. This study shows the advantage of the combination of ofloxacin and penicillin in the prevention of bacterial translocation and animal mortality after irradiation.
In vitro antibacterial activity of ME1207, a new oral cephalosporin
Authors: Miyazaki S , Miyazaki Y , Tsuji A , Nishida M , Goto S
Published: June 2012

ME1207 is the prodrug of ME1206. Its in vitro antibacterial activity was compared with that of cefteram, cefpodoxime, cefixime, and cefaclor against various clinical isolates. ME1206 was more active than the other cephems tested against staphylococci, streptococci, Morganella morganii, Pseudomonas cepacia, and Flavobacterium meningosepticum and had the most potent activity against Haemophilus influenzae and Neiserria gonorrhoeae. The drug also showed a wide spectrum of activity against other gram-positive and gram-negative bacteria, except methicillin-resistant Staphylococcus aureus, Enterococcus faecalis, Citrobacter freundii, Pseudomonas aeruginosa, Xanthomonas maltophilia, and Alcaligenes xylosoxydans.
Effects of propicillin on mixed continuous cultures of periodontal bacteria
Authors: van der Hoeven J S , van den Kieboom C W
Published: June 2012

Experiments were designed to test the antibiotic (1-phenoxypropyl)penicillin (propicillin) against a complex microflora of periodontal bacteria. This was accomplished by using a continuously growing mixed culture that was obtained by enrichment of periodontal plaque in human serum. Peptostreptococcus species, Prevotella intermedia, Lactobacillus, catenaforme, and Streptococcus species were dominant members of the enrichment culture. None of the strains isolated from the enrichment culture exhibited detectable beta-lactamase activity. MICs of propicillin for the organisms ranged from 0.1 to 1.2 mg/liter. Propicillin was added to the cultures in single doses that were repeated once or twice at 24-h intervals, that is, after 2.4 volume changes of the culture vessel. Analyses done 24 h after the last addition of propicillin revealed that total cell counts of the culture were hardly affected by 1 mg of propicillin per liter, although some changes in the microbial composition occurred. The relative insusceptibility of the culture might be explained by the low growth rate. Higher concentrations (5, 10, and 50 mg/liter) of the antibiotic caused 10- to 20-fold drops in total cell counts. In these cultures P. intermedia was selectively suppressed to below the detection level, whereas other organisms that were equally susceptible to propicillin were less affected. It was concluded that mixed continuous cultures are a useful tool for studying the effects of antibiotics against the periodontal microbiota.
Treatment of murine cryptococcal meningitis with an SCH 39304-amphotericin B combination
Authors: Albert M M , Graybill J R , Rinaldi M G
Published: June 2012

Cryptococcal meningitis was induced in BALB/c mice by intracerebral infection with Cryptococcus neoformans. Drug therapy was initiated 1 day later, with mice receiving amphotericin B (AMB), SCH 39304, combination therapy, or no drug therapy (controls). Most, but not all, combinations showed additive benefits, significantly prolonging survival and reducing organism counts in tissues compared with those in controls and groups which received the drugs independently. Optimum protection was obtained when a single dose of 10 mg of AMB per kg of body weight was combined with a fairly narrow SCH 39304 dose range. AMB antagonism did not occur with any regimen tested. AMB-azole combinations may be reasonable alternatives for patients who fail standard cryptococcosis therapeutic regimens.