bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of ketoconazole on lethal action of amphotericin B on Leishmania mexicana promastigotes
Authors: Ramos H , Saint-Pierre-Chazalet M , Bolard J , Cohen B E
Published: June 2012

The effect of ergosterol depletion by ketoconazole on the leishmanicidal activity of the pore-forming antibiotic amphotericin B (AmB) was investigated. Leishmania mexicana promastigotes were lysed within minutes by the addition of micromolar concentrations of AmB (0.5 microM) but became insensitive to AmB after growth in the presence of ketoconazole (0.25 microM, 90 h). Lipid chromatographic analysis indicated that under such conditions, ketoconazole depleted the major Leishmania sterols, dehydroepisterol and ergosterol. Plasma membrane vesicles prepared from ketoconazole-treated promastigotes exhibited a much reduced enhancement of their salt permeability after the addition of AmB at concentrations as high as 5 microM. This finding clearly indicates that upon ketoconazole treatment, the capacity of pore formation by the antibiotic is substantially impaired. The reduction of desmethyl sterols by ketoconazole was accompanied by a significant increase of 14-alpha-methyl sterols, but exogenous cholesterol remained unchanged. This ability of Leishmania promastigotes to incorporate cholesterol from the external medium may explain why ketoconazole-treated cells exhibited a much decreased but significative response to AmB when they were exposed to high AmB concentrations (2.5 or 5.0 microM). Parallel measurements by using a fluorescence energy transfer method indicated that binding of AmB to ketoconazole-treated Leishmania promastigotes and heat-transformed leishmanias was also decreased but to different extents, a finding that may be related to the differences in their sterol content. The results obtained clearly indicate that the specific interaction of AmB with desmethyl sterols, such as dehydroepisterol, ergosterol, and even exogenous cholesterol, is an absolute requirement for the lethal action exerted by this polyene antibiotic on L. mexicana promastigotes.
Rifampin for therapy of experimental pneumococcal meningitis in rabbits
Authors: Nau R , Kaye K , Sachdeva M , Sande E R , Täuber M G
Published: June 2012

Rifampin at a maximally effective dose was less active than ceftriaxone (both drugs at 10 mg/kg of body weight.h) in a rabbit model of pneumococcal meningitis (delta log10 CFU/ml.h, -0.40 +/- 0.13 versus -0.77 +/- 0.18; P < 0.01). The bactericidal activity of rifampin decreased at concentrations in cerebrospinal fluid greater than those that are clinically achievable, and use of rifampin in combination with ofloxacin had no synergistic or additive effect.
Rifabutin and sparfloxacin but not azithromycin inhibit binding of Mycobacterium avium complex to HT-29 intestinal mucosal cells
Authors: Bermudez L E , Young L S , Inderlied C B
Published: June 2012

Organisms of the Mycobacterium avium complex (MAC) cause disseminated disease in patients with AIDS, and evidence points to the gastrointestinal tract as the major route of infection. Since MAC can bind to and invade intestinal mucosal cells, we examined whether subinhibitory concentrations of antibiotics which have anti-MAC activity in vitro affect the interaction between MAC and HT-29 intestinal mucosal cells. MAC isolates were exposed to subinhibitory concentrations of rifabutin (MIC, 2.6 micrograms/ml), sparfloxacin (MIC, 8.4 micrograms/ml), or azithromycin (MIC, 32 micrograms/ml) for 30 to 120 min, washed, and incubated with HT-29 cell monolayers for 2 h at 4 degrees C. HT-29 cell monolayers were then washed to remove unbound bacteria and were subsequently lysed. The number of MAC isolates that bound to the HT-29 cells was determined by plating the cell lysate onto 7H10 agar. Preincubation of the MAC isolates with rifabutin at concentrations of 1 and 2 micrograms/ml reduced MAC binding to HT-29 cells by 80 to 90%, while MAC exposed to sparfloxacin at 1 and 7 micrograms/ml inhibited binding by 77 to 93%. Azithromycin at concentrations of 2, 10, and 30 micrograms/ml had no effect on MAC binding to HT-29 cells. Inhibition of MAC binding to the gastrointestinal mucosa may be one underlying mechanism for the prophylactic effects of rifabutin and quinolones.
Penicillin concentrations after increased doses of benzathine penicillin G for prevention of secondary rheumatic fever
Authors: Currie B J , Burt T , Kaplan E L
Published: June 2012

Plasma penicillin levels were studied 2, 3, and 4 weeks after intramuscular benzathine penicillin G (BPG) doses of 1,200,000, 1,800,000, and 2,400,000 U. Proportions of patients with penicillin levels above 25 ng/ml at each week increased with increasing BPG dose. Further studies of higher-dose BPG for rheumatic fever prophylaxis are required.
Concentrations of ceftriaxone in cerebrospinal fluid of children with meningitis receiving dexamethasone therapy
Authors: Gaillard J L , Abadie V , Cheron G , Lacaille F , Mahut B , Silly C , Matha V , Coustere C , Lokiec F
Published: June 2012

The penetration of ceftriaxone into cerebrospinal fluid (CSF) was studied with 11 children (mean age: 2 years, 4 months; range: 4 months to 8 years) with meningitis, receiving dexamethasone (0.15 mg/kg of body weight intravenously four times daily) as adjunctive therapy. Ceftriaxone was given intravenously at doses of 50 mg/kg twice daily to patients < 18 months old and 100 mg/kg once daily to patients > or = 18 months old. CSF was collected after 1 day of treatment at the expected peak concentration of ceftriaxone in CSF. Concentrations of ceftriaxone in CSF ranged from 0.7 to 9.2 mg/liter, with a mean value of 4.0 (standard deviation [SD], 2.9) mg/liter. Values were significantly higher for patients with CSF glucose levels of < 1 mmol/liter on admission to the hospital than for patients with CSF glucose levels of > or = 1 mmol/liter (mean values of 7.1 [SD, 2.2] mg/liter versus 2.2 [SD, 1.1] mg/liter; P < 0.001). After 1 day of treatment, ceftriaxone concentrations in the CSF of children receiving dexamethasone are similar to the mean values reported for children not treated with dexamethasone.
Synthesis and antimicrobial activity of dimethyl- and trimethyl-substituted phosphonium salts with alkyl chains of various lengths
Authors: Kanazawa A , Ikeda T , Endo T
Published: June 2012

Various phosphonium salts possessing single or double alkyl chains of various lengths (C10 to C18) were prepared as cationic biocides, and their antimicrobial activities against 11 typical strains of microorganisms including methicillin-resistant Staphylococcus aureus (MRSA) were evaluated. The phosphonium salts with long alkyl chains were found to show high levels of antimicrobial activity. Their activities depended strongly on the molecular structure, and a correlation between antimicrobial activity and molecular structure was observed. In the alkyltrimethylphosphonium salts, the bactericidal activity against S. aureus and Escherichia coli increased with increasing alkyl chain length, and the compound with the longest alkyl chain (C18) killed all the bacterial cells (ca. 10(7) cells per ml) within 30 min of contact at concentrations of 2.8 and 28 microM, respectively. In contrast, the bactericidal activity of dialkyldimethylphosphonium salts was found to decrease as the chain length of the substituents increased. It is significant that the phosphonium biocide containing double decyl groups exhibited the broadest spectrum of activity against microorganisms tested and showed the greatest bacteriostatic activity against MRSA (MIC = 0.78 micrograms/ml). Furthermore, we systematically investigated differences in bactericidal activity between the phosphonium salts and commonly available ammonium salts with the same hydrophobic structure. It was observed that the phosphonium salts showed an advantage over the corresponding ammonium salts in bactericidal activity and killing rate. For example, tetradecyltrimethyl- and didecyldimethylphosphonium chlorides killed all S. aureus organisms (ca. 10(7) cells per ml) within 60 and 30 min of exposure at 28 and 2.8 microM, respectively, while tetradecyltrimethyl- and didecyldimethylammonium chlorides which are representative of the existing cationic disinfectants did not kill all the bacteria even at the longest exposure time (120 min).
Effect of 3'-azido-3'-deoxythymidine and 2',3'-dideoxyinosine on establishment of human immunodeficiency virus type 1 infection in cultured CD8+ lymphocytes
Authors: Mercure L , Brenner B J , Phaneuf D , Tsoukas C , Wainberg M A
Published: June 2012

Several groups have shown that peripheral CD8+ lymphocytes can be infected with human immunodeficiency virus type 1 (HIV-1), resulting in noncytopathic infection and persistent production of viral particles. We studied the ability of 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxyinosine (ddI) to inhibit the establishment of HIV-1 infection in CD8+ cells that were derived from cultures of peripheral blood lymphocytes exposed to both virus and drug. In situ infection of CD8+ cells was demonstrated by double flow cytometry analysis by using both anti-glycoprotein 120 (anti-gp120) and anti-CD8 monoclonal antibodies. At higher concentrations of drug (e.g., 0.4 microM AZT), the production of viral particles was inhibited for over 2 months, as assessed by p24 antigen levels in the culture medium. We also performed a time course experiment to determine whether HIV-1 infection of CD8+ cells would be affected by treatment of peripheral blood lymphocytes with AZT or ddI for different intervals following exposure to virus. Quantitative PCR revealed that 0.4 microM AZT, added as late as 24 h after infection, interfered with the formation of proviral DNA in CD8+ cells. Both HIV-1 load and the production of progeny virions by CD8+ cells, as monitored by reverse transcriptase activity in culture fluids, were inhibited by both AZT and ddI in a dose-dependent manner.
Rapid identification of metallo- and serine beta-lactamases
Authors: Payne D J , Cramp R , Bateson J H , Neale J , Knowles D
Published: June 2012

Simple methods to detect, identify, and differentiate metallo- and serine beta-lactamases were developed and used to differentiate enzymes produced by 17 clinical isolates of Xanthomonas maltophilia. All isolates exhibited beta-lactamase activity, and in 16 strains this was induced by imipenem. All but one isolate hydrolyzed imipenem (and meropenem), and in all cases this activity was inhibited by 1 mM EDTA. The metallo- and serine beta-lactamases in the cell extracts were distinguished on isoelectric focusing (IEF) gels by using the following procedures. (i) Cell lysates were preincubated with 83 mM EDTA prior to IEF and subsequent visualization with nitrocefin, and (ii) after IEF, the gels were overlaid with either 1 mM zinc sulfate or 100 microM BRL 42715 before staining with nitrocefin. Bands of beta-lactamase activity which were removed by BRL 42715 but unaffected by EDTA or zinc sulfate were categorized as serine beta-lactamases. Bands which were unaffected by BRL 42715 but inhibited by EDTA or enhanced by zinc sulfate were classified as metallo-beta-lactamases. By using this approach, seven metallo-beta-lactamases were differentiated with pI values of 4.8 (two strains), 5.5 (four strains), 5.7 (one strain), 6.0 (one strain), 6.4 (four strains), 6.6 (one strain), and 6.8 (three strains). The metallo-beta-lactamase band with a pI of 6.4 aligned with the recently characterized metallo-beta-lactamase from X. maltophilia 511. Heterogeneity was also observed for the serine beta-lactamases: 14 isolates elaborated serine beta-lactamase activity which focused with major bands with at least eight different pIs. The remaining three strains produced serine beta-lactamases which focused with five distinct bands with pIs of 6.4, 6.2, 5.7, 5.5, and 5.2. We conclude that X. maltophilia produces many types of metallo- and serine beta-lactamases distinguishable by these new methods and that the previously reported L-1 and L-2 enzymes are not solely representative of the beta-lactamases produced by this species.
Single-dose pharmacokinetics of oral fleroxacin in bacteremic patients
Authors: Schrenzel J , Cerruti F , Herrmann M , Leemann T , Weidekamm E , Portmann R , Hirschel B , Lew D P
Published: June 2012

Fleroxacin is a new broad-spectrum quinolone which can be given by the oral route. The present study was designed to assess the influence of bacteremia on the pharmacokinetics of a single oral dose of fleroxacin. Thirteen patients with proven bacteremia (one or more pairs of positive blood cultures, no hypotension) were given a single 400-mg fleroxacin dose orally on two occasions while also receiving standard antibiotic therapy. The first dose was administered 12 to 36 h after the last positive blood culture was drawn (day 1), and a second dose was administered 7 days later (day 7 +/- 2) to compare the pharmacokinetics between the acute and the convalescent phases of the disease. Following each administration of fleroxacin, serial plasma samples were collected for up to 72 h and were analyzed for unchanged drug by a reversed phase high-pressure liquid chromatography technique. There were no significant changes in the following pharmacokinetic parameters (mean standard deviation) the maximum concentration of drug in serum (6.4 +/- 1.5 versus 6.7 +/- 1.9 mg/liter), the minimum concentration of drug in serum, defined as the concentration of drug in serum at 24 h postdose (3.0 +/- 1.7 versus 2.5 +/- 1.2 mg/liter), the time to the maximum concentration of drug in serum (2.3 +/- 1.4 versus 2.0 +/- 1.2 h), and the elimination half-life (19.7 +/- 8.0 versus 17.9 +/- 6.9 h). Fleroxacin clearances were compared for each individual patient. A positive correlation (R2 = 0.787) was found between the values measured on day 1 and day 7. Oral clearance of fleroxacin (CL = CL/F, where F is bioavailability was slightly, but not significantly, reduced during the bacteremic phase (oral clearance, 43.8+/- 23.5 versus 48.5 +/- 17.5 ml/min.). When compared with previous results obtained in healthy young subjects, longer times to the maximum concentration of drug in serum and elimination half-lives and higher areas under the curve were observed. This could be due to the bacteremic state, the old age of the patients (mean, 66 years), and the low renal clearance (mean calculated creatinine clearance, 71.1 ml/min). A single oral dose of 400 mg of fleroxacin provides sufficient levels in serum to cover susceptible microorganisms for at least 24 h in bacteremic patients. Renal function appeared to be the key element that had to be taken into consideration to adapt fleroxacin dosage profiles in our patient population. Bacteremia itself appeared to amplify that phenomenon, but to a much lesser extent than renal function did.
Correlation between response to acyclovir and foscarnet therapy and in vitro susceptibility result for isolates of herpes simplex virus from human immunodeficiency virus-infected patients
Authors: Safrin S , Elbeik T , Phan L , Robinson D , Rush J , Elbaggari A , Mills J
Published: June 2012

In vitro susceptibility testing of herpes simplex virus (HSV) isolates will play an increasingly important role in guiding the clinical management of immunocompromised hosts who have lesions that are poorly responsive to therapy with standard antiviral agents. We assessed the correlation between the in vitro susceptibility result using a plaque reduction assay in Vero cells and the response to antiviral therapy with acyclovir or foscarnet for 243 clinical isolates of HSV collected from 115 human immunodeficiency virus-infected patients. The in vitro results and clinical responses were highly associated for both acyclovir and foscarnet (P < 0.001 and P < 0.001, respectively). The predictive values of a susceptible result (50% effective concentrations, < 2 micrograms/ml for acyclovir and < 100 micrograms/ml for foscarnet) for complete healing of lesions were 62% for acyclovir and 82% for foscarnet; the predictive values of a resistant result for failure to heal were 95% for acyclovir and 88% for foscarnet. Thus, in vitro testing has clinical utility in guiding therapy, although the 1 to 2 weeks required to derive a definitive result by the plaque reduction assay is a major limitation.
Time-survival studies for quantifying effects of azlocillin and tobramycin on Pseudomonas aeruginosa
Authors: McFarland M M , Scott E M , Li Wan Po A
Published: June 2012

Time-survival studies were conducted to estimate the effects of azlocillin and tobramycin on Pseudomonas aeruginosa NCIMB 8295 (in the exponential phase of growth) at concentrations ranging from one-quarter to twice the MIC. The effects of the individual agents and their combinations were determined by measuring the viable counts (CFU per milliliter) over a 24-h period. The typical pattern observed from the plot of the logarithm of the CFU per milliliter against time was an initial rapid killing; this was followed by a period of stasis and regrowth. Initial rates of killing by tobramycin were concentration dependent, whereas this was not the case with azlocillin. From the time-survivor plots, the area under the curve for viable bacteria was also calculated. It offered a useful method of interpreting the results of time-kill studies, taking the overall pattern of killing and regrowth into consideration. The area under the curve for viable bacteria was concentration dependent for both antibiotics. A 2(2) factorial experimental design was used to analyze the joint effects of azlocillin and tobramycin. In such a factorial experiment, an interaction between two factors, in this case, azlocillin and tobramycin concentrations, is shown by a change in the slope of the plot when the concentration of the interactant is changed. Analysis of variance showed that the combination was synergistic at low concentrations, but this was not significant when the concentration of either interactant was increased.
Prospective randomized comparison of imipenem monotherapy with imipenem plus netilmicin for treatment of severe infections in nonneutropenic patients
Authors: Cometta A , Baumgartner J D , Lew D , Zimmerli W , Pittet D , Chopart P , Schaad U , Herter C , Eggimann P , Huber O
Published: June 2012

Nosocomial pneumonia and sepsis, as well as severe diffuse peritonitis, must be treated early in order to prevent complications such as septic shock and organ dysfunctions. With the availability of new broad-spectrum and highly bactericidal antibiotics, the need of combining beta-lactams with aminoglycosides for the treatment of severe infections should be reassessed. A prospective randomized controlled study was performed to compare imipenem monotherapy with a combination of imipenem plus netilmicin in the empiric treatment of nosocomial pneumonia, nosocomial sepsis, and severe diffuse peritonitis. A total of 313 patients were enrolled, and 280 were assessable. The antibiotic treatment was successful in 113 of 142 patients (80%) given the monotherapy and in 119 of 138 patients (86%) given the combination (P = 0.19). The failure rates for the most important type of infection, i.e., pneumonia, were similar in the two groups, as well as the number of superinfections. While creatinine increase was associated with factors not related to antibiotic therapy for all eight patients of the monotherapy group, no factor other than the antibiotics could be found for 6 of the 14 cases of nephrotoxicity observed in the combination group (P = 0.014). Finally, the emergence of Pseudomonas aeruginosa resistant to imipenem occurred in 8 monotherapy patients and in 13 combination therapy patients. In conclusion, imipenem monotherapy appeared as effective as the combination of imipenem plus netilmicin for the treatment of severe infection. The addition of netilmicin increased nephrotoxicity, and it did not prevent the emergence of P. aeruginosa resistant to imipenem.
Antagonistic effects of fluconazole and 5-fluorocytosine on candidacidal action of amphotericin B in human serum
Authors: Martin E , Maier F , Bhakdi S
Published: June 2012

This study addressed the effects of fluconazole and 5-fluorocytosine on the candidacidal activity of amphotericin B in the presence of human serum. A Candida albicans isolate that was susceptible to all three agents according to standard testing procedures was employed. Fungicidal activity was estimated by using a flow cytometric procedure that exploited the fact that yeast cells killed by amphotericin B diminish in size and take up propidium iodide. The following findings were made. (i) Fluconazole and 5-fluorocytosine each failed to inhibit pseudohyphal formation and cell aggregation even when applied at 10 and 50 micrograms/ml, respectively, for up to 10 h. Hence, these agents were not fungistatic when tested in the presence of serum. (ii) Simultaneous application of 5-fluorocytosine had neither enhancing nor inhibitory effects on the fungicidal activity of amphotericin B. However, yeasts that were preincubated for 20 h with 5-fluorocytosine became less susceptible to killing by amphotericin B. (iii) Fluconazole exerted a frank antagonistic effect on the fungicidal activity of amphotericin B. Thus, under our in vitro conditions, both fluconazole and 5-fluorocytosine can overtly antagonize the candidacidal action of amphotericin B.
Antileishmanial activity of licochalcone A in mice infected with Leishmania major and in hamsters infected with Leishmania donovani
Authors: Chen M , Christensen S B , Theander T G , Kharazmi A
Published: June 2012

This study was designed to examine the antileishmanial activity of the oxygenated chalcone licochalcone A in mice and hamsters infected with Leishmania parasites. Intraperitoneal administration of licochalcone A at doses of 2.5 and 5 mg/kg of body weight per day completely prevented lesion development in BALB/c mice infected with Leishmania major. Treatment of hamsters infected with L. donovani with intraperitoneal administration of licochalcone A at a dose of 20 mg/kg of body weight per day for 6 consecutive days resulted in a > 96% reduction of parasite load in the liver and the spleen compared with values for untreated control animals. The [3H]thymidine uptake by the parasites isolated from the treated hamsters was only about 1% of that observed in parasites isolated from the controls. Oral administration of licochalcone A at concentrations of 5 to 150 mg/kg of body weight per day for 6 consecutive days resulted in > 65 and 85% reductions of L. donovani parasite loads in the liver and the spleen, respectively, compared with those of untreated control hamsters. These data clearly demonstrate that licochalcone A is a promising lead for the development of a new drug against leishmaniases.
Treatment of complicated urinary tract infections with lomefloxacin compared with that with trimethoprim-sulfamethoxazole
Authors: Nicolle L E , Louie T J , Dubois J , Martel A , Harding G K , Sinave C P
Published: June 2012

The efficacy of lomefloxacin given at 400 mg once daily for 14 days compared with that of trimethoprim-sulfamethoxazole at 160 and 800 mg, respectively, given twice daily for 14 days in the treatment of symptomatic complicated urinary tract infections was studied in a prospective, randomized, single-blind multicenter study. A total of 133 subjects presenting with signs and symptoms of urinary tract infection and an underlying abnormality consistent with complicated urinary tract infection were enrolled in the study. Bacteriologic cure was significantly better in 68 subjects randomized to lomefloxacin than in 65 subjects randomized to trimethoprim-sulfamethoxazole at short-term follow-up (88 versus 52%; 95% confidence intervals [CIs] 77 and 94% and 39 and 65%, respectively) this difference was no longer significant at long-term follow-up (64 versus 47%; CIs, 52 and 75% and 32 and 57%, respectively). Clinical outcomes were similar for both therapeutic regimens at short- and long-term follow-ups. The organisms that infected the subjects pretherapy were more frequently resistant to trimethoprim-sulfamethoxazole, and drug therapy was discontinued more frequently in subjects treated with trimethoprim-sulfamethoxazole because of adverse antimicrobial effects. In secondary analyses, outcomes did not differ with age or underlying genitourinary abnormality.(ABSTRACT TRUNCATED AT 250 WORDS)
Use of cilofungin as direct fluorescent probe for monitoring antifungal drug-membrane interaction
Authors: Ko Y T , Ludescher R D , Frost D J , Wasserman B P
Published: June 2012

Cilofungin is an antifungal cyclopeptide which inhibits cell wall (1,3)-beta-glucan biosynthesis in fungal organisms, and its action against Candida albicans (1,3)-beta-glucan synthase has been widely studied. Since glucan synthase inactivation is thought to partially result from perturbations of the membrane lipid environment, the interaction of cilofungin with fungal membranes and phosphatidylcholine membrane vesicles was studied. Cilofungin, which contains two independent aromatic groups, has an excitation maximum of 270 nm and an emission maximum of 317 nm in aqueous solution. Comparison of the fluorescence properties of cilofungin with those of the analogs pneumocandin B0, N-acetyl-tyrosinamide, and 4-hydroxybenzamide indicated that the emission of cilofungin largely derived from the p-octyloxybenzamide side chain. Microsomal membranes from Saccharomyces cerevisiae, C. albicans, and phosphatidylcholine membrane vesicles induced a blue shift in the cilofungin emission spectrum and increased the cilofungin steady-state emission anisotropy, providing direct evidence for a cilofungin-membrane interaction. Cilofungin interacted more strongly with membranes of C. albicans than with those of S. cerevisiae, correlating with previous findings that C. albicans is far more susceptible than S. cerevisiae to the action of cilofungin. These findings support the hypothesis that drug-induced inhibition of the (1,3)-beta-glucan synthesis results from the perturbation of the membrane environment and the interaction with the glucan synthase complex combined. The study demonstrated ways in which the fluorescence properties of drugs can be used to directly evaluate drug-membrane interactions and structure-activity relationships.
Pharmacodynamic effects of subinhibitory concentrations of imipenem on Pseudomonas aeruginosa in an in vitro dynamic model
Authors: Maggiolo F , Taras A , Frontespezi S , Legnani M C , Silanos M A , Pravettoni G , Suter F
Published: June 2012

The postantibiotic effect (PAE), sub-MIC effect (SME), and postantibiotic sub-MIC effect (PASME) of imipenem on Pseudomonas aeruginosa were investigated with an in vitro dynamic model reproducing in vivo elimination kinetics of the antibiotic. The PASMEs were constantly longer than the corresponding SMEs, but differences between them were not statistically significant. Both PASMEs and SMEs were initially bactericidal and were significantly longer than PAEs. The mean values of both PASMEs and SMEs were over 12 h. SMEs appear to be more relevant for the bacterial growth kinetics than PAEs.
Fluconazole susceptibilities of Candida species and distribution of species recovered from blood cultures over a 5-year period
Authors: Price M F , LaRocco M T , Gentry L O
Published: June 2012

The distribution and fluconazole susceptibilities of Candida species isolated over a 5-year period were investigated. Susceptibilities were determined by using a new microtiter procedure and the National Committee for Clinical Laboratory Standards (NCCLS) proposed standard. The new method correlated well with the NCCLS proposed standard and gave very clear end points. Results indicate that there are species-related differences in MICs as reflected in the MICs for 90% of species tested. Candida albicans is most susceptible to fluconazole, while Candida glabrata is among the least susceptible. These findings coincided with the observation of a shift in distribution of yeast species recovered from blood cultures from 1987 to 1992. C. albicans was the predominant species (87%) in the pre- or early fluconazole years but decreased to only 31% of the isolates in 1992. Thus, Candida species for which MICs of fluconazole were higher have become more prominent in recent years. Significantly, throughout this period, MICs for each species did not change appreciably.
Licochalcone A, a new antimalarial agent, inhibits in vitro growth of the human malaria parasite Plasmodium falciparum and protects mice from P. yoelii infection
Authors: Chen M , Theander T G , Christensen S B , Hviid L , Zhai L , Kharazmi A
Published: June 2012

Licochalcone A, isolated from Chinese licorice roots, inhibited the in vitro growth of both chloroquine-susceptible (3D7) and chloroquine-resistant (Dd2) Plasmodium falciparum strains in a [3H]hypoxanthine uptake assay. The growth inhibition of the chloroquine-resistant strain by licochalcone A was similar to that of the chloroquine-susceptible strain. To examine the activity of licochalcone A on the different asexual blood stages of the parasite, licochalcone A was added to highly synchronized cultures containing rings, trophozoites, and schizonts. The growth of the parasites at all stages was inhibited by licochalcone A. The in vivo activity of licochalcone A was tested in a mouse model of infection with P. yoelii. Licochalcone A administered either intraperitoneally or orally for 3 to 6 days protected the mice from the otherwise lethal P. yoelii infection. These results demonstrate that licochalcone A exhibits potent antimalarial activity and might be developed into a new antimalarial drug.
Pharmacokinetics of zidovudine phosphorylation in peripheral blood mononuclear cells from patients infected with human immunodeficiency virus
Authors: Stretcher B N , Pesce A J , Frame P T , Stein D S
Published: June 2012

As part of an effort towards optimization of dosing of zidovudine (ZDV), formation and elimination of total phosphorylated ZDV (ZDVPt) in peripheral blood mononuclear cells were examined in 21 asymptomatic human immunodeficiency virus-infected patients during their first 24 weeks of therapy (AIDS Clinical Trials Group Protocol 161). Intracellular concentrations of ZDVPt were measured with a previously described and validated radioimmunoassay technique. Although ZDV phosphorylation occurred readily upon initiation of therapy, it declined with time; the area under the concentration-time curve (AUC) at week 4 (mean +/- standard deviation, 3.41 +/- 0.93 pmol.h/10(6) cells) was significantly greater than that at week 24 (2.19 +/- 1.10 pmol.h/10(6) cells). Plasma ZDV AUC did not change with time and did not correlate with ZDVPt AUC. In dose-response experiments (20 to 100 mg orally), phosphorylation did not proportionally increase with increasing plasma ZDV concentrations. Similarly, compared with a single dose, two doses of ZDV over an 8-h period resulted in little ZDVPt increase in cells relative to increase in plasma ZDV concentrations. The half-life of intracellular ZDVPt was twice that of plasma ZDV (4 versus 2 h), suggesting that an every-8-h dosing regimen is justifiable. These findings suggest that metabolism of ZDV to its active intracellular forms may be saturable in some patients, is poorly correlated with plasma concentrations, and diminishes over time. These findings have implications for future development and management of anti-human immunodeficiency virus nucleoside therapy.
L-651,392, a potent leukotriene inhibitor, controls inflammatory process in Escherichia coli pyelonephritis
Authors: Tardif M , Beauchamp D , Bergeron Y , Lessard C , Gourde P , Bergeron M G
Published: June 2012

In this study, the relationship between leukotrienes, peritubular cell infiltration with polymorphonuclear cells (PMNs) and renal tubular damage was investigated in a rat model of acute ascending pyelonephritis. Infection was induced by the injection of 10(5) CFU of Escherichia coli into the bladder and occlusion of the left ureter for 24 h. Treatment of infected animals was started 24 h after the induction of pyelonephritis with either hydrocortisone (25 mg/kg of body weight per day), the leukotriene inhibitor L-651,392 (10 mg/kg/day), or the vehicle of L-651,392 and was maintained for 5 days. At the end of treatment, the animals were killed, serum was collected, and both kidneys were removed for colony counts and histopathology. Renal function was evaluated by the measurement of blood urea nitrogen levels and creatinine clearance. The numbers of PMNs and mononuclear cells (MNs) in the cortex and medulla were recorded for all groups on plastic sections done from the left kidney. Infection alone (vehicle of L-651,392) resulted in intensive interstitial infiltration and a severe tubular destruction in the cortex. Treatment with hydrocortisone did not prevent PMN migration and tissue damage. By contrast, treatment with L-651,392 resulted in a significant reduction in PMNs (P < 0.001 in comparisons with all other groups) and greater preservation of the tubular structure despite identical bacterial counts than in the group receiving hydrocortisone. We conclude that L-651,392 prevents inflammatory cells from reaching the site of infection and protects the kidney from tubular damage associated with inflammation during pyelonephritis. Inhibitors of leukotrienes should be further investigated for their potential benefit as adjuvants to antibiotherapy in the treatment of pyelonephritis.
Potency and selectivity of inhibition of human immunodeficiency virus protease by a small nonpeptide cyclic urea, DMP 323
Authors: Erickson-Viitanen S , Klabe R M , Cawood P G , O'Neal P L , Meek J L
Published: June 2012

DMP 323 is a potent inhibitor of the protease of human immunodeficiency virus (HIV), with antiviral activity against both HIV type 1 and HIV type 2. This compound is representative of a class of small, novel, nonpeptide cyclic urea inhibitors of HIV protease that were designed on the basis of three-dimensional structural information and three-dimensional database searching. We report here studies of the kinetics of DMP 323 inhibition of the cleavage of peptide and HIV-1 gag polyprotein substrates. DMP 323 acts as a rapidly binding, competitive inhibitor of HIV protease. DMP 323 is as potent against both peptide and viral polyprotein substrates as A-80987, Q8024, and Ro-31-8959, which are among the most potent inhibitors of HIV protease described in the literature to date. Incubation with human plasma or serum did not decrease the effective potency of DMP 323 for HIV protease, suggesting that plasma protein binding is of a low affinity relative to that of HIV protease. DMP 323 was also assessed for its ability to inhibit the mammalian proteases renin, pepsin, cathepsin D, cathepsin G, and chymotrypsin. No inhibition of greater than 12% was observed for any of these enzymes at concentrations of DMP 323 that were 350 to 40,000 times higher than that required to inhibit the viral protease 50%.
DMP 323, a nonpeptide cyclic urea inhibitor of human immunodeficiency virus (HIV) protease, specifically and persistently blocks intracellular processing of HIV gag polyprotein
Authors: Rayner M M , Cordova B C , Meade R P , Aldrich P E , Jadhav P K , Ru Y , Lam P Y
Published: June 2012

DMP 323, a C-2-symmetrical cyclic urea, is representative of a new class of inhibitors of human immunodeficiency virus protease. In this study, we correlate the potent antiviral activity of DMP 323 in acute infections with antiprotease activity assessed by monitoring the inhibition of the processing of viral gag precursor polyprotein from chronically infected lymphoid and monocytoid cell lines. Electron microscopic examination confirmed that the inhibition of gag processing was associated with the production of immature viral particles. Reduction of DMP 323 in the environment of unprocessed gag viral particles did not result in the resumption of gag processing for at least 72 h.
Macrolide antibiotics protect against endotoxin-induced vascular leakage and neutrophil accumulation in rat trachea
Authors: Tamaoki J , Sakai N , Tagaya E , Konno K
Published: June 2012

We studied the effects of macrolides on lipopolysaccharide (LPS)-induced airway inflammation in the rat tracheal mucosa. Erythromycin and roxithromycin dose dependently inhibited microvascular leakage and neutrophil recruitment induced by LPS. This inhibitory action on vascular permeability was abolished by neutrophil depletion.
Emergence of Haemophilus ducreyi resistance to trimethoprim-sulfamethoxazole in Rwanda
Authors: Van Dyck E , Bogaerts J , Smet H , Tello W M , Mukantabana V , Piot P
Published: June 2012

The in vitro susceptibilities of 112 clinical isolates of Haemophilus ducreyi to six antimicrobial agents were determined. These isolates were obtained in Kigali, Rwanda, during three studies on genital ulcer disease performed in 1986 (18 isolates), 1988 (23 isolates), and 1991 (71 isolates). All H. ducreyi isolates were susceptible to azithromycin, ceftriaxone, ciprofloxacin, and erythromycin; all isolates obtained in 1986 were also susceptible to trimethoprim and to the combination trimethoprim-sulfamethoxazole. In contrast, 39 and 9% of the isolates obtained in 1988 and 59 and 48% of the isolates obtained in 1991 were resistant to trimethoprim (MIC, > or = 4.0 mg/liter) and trimethoprim-sulfamethoxazole (MIC, < or = 4.0/76 mg/liter), respectively. These data indicate that trimethoprim-sulfamethoxazole can no longer be recommended for use in the treatment of chancroid in Rwanda, and possibly elsewhere in Africa.
Decreased susceptibility to penicillin G and Tet M plasmids in genital and anorectal isolates of Neisseria meningitidis
Authors: Winterscheid K K , Whittington W L , Roberts M C , Schwebke J R , Holmes K K
Published: June 2012

Genital and anorectal isolates of Neisseria meningitidis were characterized, and their antimicrobial susceptibilities were determined. Twelve of 43 isolates demonstrated moderate susceptibility to penicillin G (MIC range, 0.125 to 0.5 microgram/ml). Two isolates were resistant to tetracycline (MIC, > or = 8 micrograms/ml) and contained plasmids of 25.2 MDa.
Intermittent azithromycin for treatment of Mycobacterium avium infection in beige mice
Authors: Klemens S P , Cynamon M H
Published: June 2012

The activity of azithromycin (AZI) was evaluated in the beige mouse model of disseminated Mycobacterium avium infection. Mice were infected intravenously with approximately 10(7) viable avium ATCC 49601. AZI at 50, 100, or 200 mg/kg of body weight or clarithromycin (CLA) at 200 mg/kg was given by gavage 5 days per week for 4 weeks. Groups of treated mice were compared with untreated control animals. A dose-related reduction in cell counts in organs was observed with AZI treatment. AZI at 200 mg/kg was more active than CLA at 200 mg/kg against organisms in spleens. The activities of these two agents at 200 mg/kg were comparable against organisms in lungs. In a second study, AZI at 200 mg/kg was given daily for 5 days; this was followed by intermittent AZI treatment for the next 3 weeks. The activities of AZI given on a three-times- and five-times-per-week basis in the continuation phase were comparable. AZI given on a once-weekly basis was less active. The regimen of AZI given in combination with rifapentine on a once-weekly basis for 8 weeks showed promising activity. Clinical evaluation of AZI and rifapentine will help to define the roles of these agents in the treatment of disseminated M. avium complex infection.
Neurotoxicity of artemisinin analogs in vitro
Authors: Wesche D L , DeCoster M A , Tortella F C , Brewer T G
Published: June 2012

The sesquiterpene endoperoxide antimalarial agents arteether and artemether have been reported to cause neurotoxicity with a discrete distribution in the brain stems of rats and dogs after multiple doses. The nature and distribution of the brain lesions suggest a specific neuronal target, the identity of which is unknown. In order to further investigate artemisinin analog-induced neurotoxicity, we evaluated several in vitro models: fetal rat primary neuronal cultures, fetal rat secondary astrocyte cultures, and transformed neuronal cultures (rat-derived neuroblastoma NG108-15 and mouse-derived neuroblastoma Neuro-2a). Results indicate that toxicity was specific for neuronal cell types but not glial cells. Neurotoxicity, as indexed by liberation of lactate dehydrogenase and/or inhibition of radiolabelled-leucine uptake, was seen in all three neuronal culture types, implicating a common target. In vitro neurotoxicity was dose and time dependent. Acute exposure to drug results in delayed, but not immediate, manifestations of cell toxicity. Structure-activity comparisons indicate that substitutions at positions 9 and 10 and stereoisomerism at position 10 of the artemisinin backbone influence the degree of toxicity. The endoperoxide is necessary but not sufficient for toxicity. Sodium artesunate and dihydroartemisinin, a metabolite common to all artemisinin analogs currently being developed for clinical use, are the most potent of all analogs tested. These results are consistent with a specific neuronal target, but the identity of the target(s) remains unknown.
Bactericidal activities of DU-6859a and clinafloxacin (CI-960) against staphylococci
Authors: Forstall G J , Knapp C C , Washington J A
Published: June 2012

Time killing curves were calculated at concentrations of 2 and 8 times the MICs of DU-6859a and clinafloxacin against six isolates of Staphylococcus aureus. Both quinolones produced a decrease in the log10 CFU per milliliter of > or = 3 within 3 h at 2 and 8 times the MIC for the ciprofloxacin-susceptible isolates and at 8 times the MIC for the ciprofloxacin-resistant isolates; however, only 8 times the MIC of DU-6859a consistently prevented regrowth of all isolates after 24 h of incubation.
Characteristics of murine model of genital infection with Chlamydia trachomatis and effects of therapy with tetracyclines, amoxicillin-clavulanic acid, or azithromycin
Authors: Beale A S , Upshon P A
Published: June 2012

Following intravaginal inoculation of progesterone-treated outbred mice with Chlamydia trachomatis MoPn, 4 to 6 log10 inclusion-forming units were recovered in vaginal swabs for 21 days but all animals were culture negative after 28 days. Serum antibody titers were elevated and remained high for at least 70 days. Between 28 and 70 days, upper tract infection (inflammation and distension of the uterine horns, occlusion of oviducts with inflammatory exudate, pyosalpinx, and hydrosalpinx) was seen in > 80% of the animals. Mice were dosed orally, commencing at 7 days after infection, with minocycline, doxycycline, or amoxicillin-clavulanate. Further groups received azithromycin either as a single high dose or as lower once-daily doses. In addition, minocycline and amoxicillin-clavulanate were administered at 24 h after infection, and this early treatment prevented elevation of antibody titers whereas delayed therapy did not. Vaginal swabs from mice in all treatment regimens were culture negative except for 25% of mice receiving either early amoxicillin-clavulanate or low-dose azithromycin, which yielded low numbers (20 to 70 inclusion-forming units) of chlamydiae. Numbers of fertile mice in the early treatment regimens and their litter sizes were similar to those of noninfected controls, although 25% of amoxicillin-clavulanate-treated mice had unilateral hydrosalpinges. In comparison, 88% of untreated mice developed hydrosalpinges and only 25% conceived. Delayed dosing did not affect the outcome of amoxicillin-clavulanate therapy but did diminish the protective efficacy of minocycline such that 50% of treated mice had either unilateral hydrosalpinges or ovarian abscesses. Doxycycline and azithromycin were highly effective in restoring fertility. This model makes possible the study of both short- and long-term outcomes of chlamydial infection.
Assessment of mycobacterial viability by RNA amplification
Authors: van der Vliet G M , Schepers P , Schukkink R A , van Gemen B , Klatser P R
Published: June 2012

We investigated whether the presence of intact RNA is a valuable indicator of viability of mycobacteria with Mycobacterium smegmatis. M. smegmatis was exposed to various concentrations of rifampin and ofloxacin suspended in broth for different periods of time. The NASBA nucleic acid amplification system was used because of its rapid, sensitive, and specific detection of 16S rRNA. During drug exposure, the viability of the mycobacteria, expressed by the number of CFU, was compared with the presence of 16S rRNA as determined by NASBA and with the presence of DNA coding for 16S rRNA as determined by PCR. Both NASBA and PCR were shown to have a detection limit of approximately 5 x 10(2) CFU/ml. The intensity of the NASBA signal corresponded well with the number of CFU, and the lack of NASBA signal coincided with a loss of viability, which was reached after 3 days of exposure to bactericidal concentrations of both drugs. The presence of mycobacterial DNA, as determined by the intensity of the PCR signal, and the viability of M. smegmatis were not related, but an increase in the number of cells and intensity of PCR signal correlated well. Bacterial viability may thus be assessed by a rapid, sensitive, and specific, and semiquantitative technique by using NASBA. This system of viability testing provides the potential for rapid evaluation of drug susceptibility testing.
Quinolone resistance mutations in the DNA gyrase gyrA and gyrB genes of Staphylococcus aureus
Authors: Ito H , Yoshida H , Bogaki-Shonai M , Niga T , Hattori H , Nakamura S
Published: June 2012

A 6.4-kb DNA fragment containing the DNA gyrase gyrA and gyrB genes was cloned and sequenced from the quinolone-susceptible Staphylococcus aureus type strain ATCC 12600. An expression plasmid was constructed by inserting the cloned genes into the Escherichia coli-S. aureus shuttle vector pAT19, and deletion plasmids carrying only functional gyrA and gyrB genes were derived from this plasmid. An efficient transformation system for S. aureus RN4220 was established by using these plasmids. Quinolone-resistant mutants of S. aureus RN4220 were isolated by three-step selection with quinolones. The first- and second-step mutants were considered to be transport mutants, and the third-step mutants were divided into five groups with respect to their resistance patterns and transformation results with gyrA and gyrB genes. Sequencing analysis of the resulting mutant gyrase genes showed that they had the following point mutations: group 1, Ser-84 (TCA) to Leu (TTA) in GyrA; group 2, Ser-84 (TCA) to Ala (GCA), Ser-85 (TCT) to Pro (CCT), or Glu-88 (GAA) to Lys (AAA) in GyrA; group 3, Asp-437 (GAC) to Asn (AAC) in GyrB; group 4, Arg-458 (CGA) to Gln (CAA) in GyrB; and group 5, Ser-85 (TCT) to Pro (CCT) in GyrA and Asp-437 (GAC) to Asn (AAC) in GyrB. When the gyrA and/or gyrB mutants were transformed with the wild-type gyrA and/or gyrB plasmids, they became quinolone susceptible, but transformants with the plasmids having the same mutations on the gyrA and/or gyrB genes did not confer susceptibility. These results indicate that mutations in both gyrA and gyrB can be responsible for quinolone resistance in S. aureus.