bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative in vitro activity of DU-6859a, a new fluoroquinolone agent, against gram-positive cocci
Authors: Korten V , Tomayko J F , Murray B E
Published: June 2012

The in vitro activity of DU-6859a (DU), a new fluoroquinolone agent, was evaluated against 233 gram-positive cocci and was compared with those of ciprofloxacin, vancomycin, nafcillin, and ampicillin. The MICs of DU for 90% of the staphylococci tested were < or = 0.06 microgram/ml. All of the groups A and B and viridans group streptococci were inhibited by < or = 0.125 microgram of DU per ml, which was 32-fold more active than ciprofloxacin. On the basis of MICs for 90% of the strains tested, DU was 32- and 16-fold more active than ciprofloxacin against Enterococcus faecalis and Enterococcus faecium, respectively. The bactericidal activity of DU was demonstrated by time-kill techniques against all ciprofloxacin-susceptible enterococci. DU shows promise for the treatment of infections with gram-positive cocci and warrants further evaluation by in vitro and in vivo studies.
A changing pattern of susceptibility of Xanthomonas maltophilia to antimicrobial agents: implications for therapy
Authors: Vartivarian S , Anaissie E , Bodey G , Sprigg H , Rolston K
Published: June 2012

The in vitro susceptibilities of 130 Xanthomonas maltophilia isolates to 12 antibiotics--trimethoprim-sulfamethoxazole, minocycline, ticarcillin-clavulanate, ceftazidime, cefoperazone, cefoperazone-sulbactam, imipenem, ciprofloxacin, and the investigational quinolones PD 117558, PD 117596, PD 127391, and sparfloxacin--were determined by a microtiter broth dilution technique. Other than the investigational quinolones, the most active antibiotics were minocycline, trimethoprim-sulfamethoxazole, and ticarcillin-clavulanate, in order. However, the first two were not bactericidal, while about half of the isolates exhibited intermediate susceptibility to ticarcillin-clavulanate. Patterns of susceptibility to trimethoprim-sulfamethoxazole and ciprofloxacin relative to the years of isolation of these strains reflected the development of resistance to the antibiotic prophylaxis practices in the hospital. We recommend that a combination of antibiotics, such as trimethoprim-sulfamethoxazole, minocycline, and ticarcillin-clavulanate, at or close to the maximum tolerated doses be in the treatment of serious X. maltophilia infections.
Insertions of IS256-like element flanking the chromosomal beta-lactamase gene of Enterococcus faecalis CX19
Authors: Rice L B , Marshall S H
Published: June 2012

We have previously identified an inverted repeat characteristic of staphylococcal beta-lactamase transposons adjacent to the chromosomal beta-lactamase genes of Enterococcus faecalis CH19 and its beta-lactamase-producing transconjugant CX19. Nucleotide sequence analysis of the CH19 beta-lactamase structural gene (blaZ) reveals it to be identical to the blaZ gene from E. faecalis HH22 and to the blaZ gene from the staphylococcal beta-lactamase transposon Tn552. We also report the presence of nucleotide sequence identical to a 317-bp region of the staphylococcal insertion sequence IS256 upstream of the blaZ gene in both CH19 and CX19. The identical segment of IS256 is present downstream of the blaZ gene of CX19, suggesting a second insertion of the element (in the inverted orientation) accompanying transfer to the recipient strain. Restriction analysis of the areas beyond the ClaI sites used to clone these regions suggests that full copies of the IS256-like element (designated IS256E) are present in all positions but that these elements were not directly involved in the transfer of the beta-lactamase gene to the recipient strain. We have also identified a region downstream of the second IS256E insertion site which exhibits substantial homology to ISSIW, an iso-ISSI insertion originally identified in Lactococcus lactis subsp. cremoris. These data suggest that the two enterococcal blaZ genes sequenced to date evolved from a common ancestor and may at one time have been incorporated into a transposon similar to Tn552. They also suggest that IS256-like elements are mobile in E. faecalis and capable of inserting in a manner consistent with the formation of novel composite transposons. Finally, they provide the first confirmation of the presence of an ISSI-like element in enterococci, raising the possibility that these elements play a role in the exchange of chromosomal antimicrobial resistance determinants.
Multiply resistant Klebsiella pneumoniae strains from two Chicago hospitals: identification of the extended-spectrum TEM-12 and TEM-10 ceftazidime-hydrolyzing beta-lactamases in a single isolate
Authors: Bradford P A , Cherubin C E , Idemyor V , Rasmussen B A , Bush K
Published: June 2012

Ceftazidime-resistant Klebsiella pneumoniae strains began to appear when ceftazidime usage was increased in two unrelated Chicago hospitals. These strains produced a beta-lactamase with an isoelectric point of 5.6 (RP-5.6) and strong hydrolyzing activity against ceftazidime. Two different restriction digest profiles were associated with the ceftazidime resistance plasmids. A second beta-lactamase with a pI of 5.2 (RP-5.2) was coproduced in two representative strains. The second beta-lactamase hydrolyzed ceftazidime, cefotaxime, and aztreonam with relative hydrolysis rates of < 8% of that observed for benzylpenicillin. Both enzymes were inhibited by clavulanic acid and tazobactam. Nucleotide sequencing of the genes coding for RP-5.2 and RP-5.6 revealed sequences identical to those of the TEM-12 and TEM-10 beta-lactamase genes, respectively. Both genes were derived from a TEM-1 sequence related to that of the gene encoded on the Tn2 transposon. Single point mutations are required to progress from TEM-1 to TEM-12 and from TEM-12 to TEM-10. Extracts from broths grown from single cell isolates of the strain producing TEM-12 and TEM-10 were shown to contain both enzymes. Transconjugants producing either the TEM-12 or the TEM-10 beta-lactamase were obtained. A significant finding was that both enzymes were encoded by plasmids with identical restriction digest patterns. These studies show that mutations leading to extended-spectrum beta-lactamases can occur sequentially in the same organism, with the genes encoding both enzymes maintained stably.
Pharmacokinetics of dideoxyinosine in neonatal pigtailed macaques
Authors: Pereira C M , Nosbisch C , Unadkat J D
Published: June 2012

To determine whether age affects the pharmacokinetics of dideoxyinosine in neonatal pigtailed macaques (Macaca nemestrina), dideoxyinosine (10 mg/kg of body weight) was administered as a single intravenous bolus to macaques at ages < 1 week, 1 month, and 4 months. Clearance from plasma at < 1 week of age was significantly lower (P < 0.05) and the terminal half-life was significantly higher than the corresponding values obtained at 1 month and 4 months of age. Our data indicate that the pharmacokinetics of dideoxyinosine change significantly with age in M. nemestrina.
Pharmacokinetics and safety of levofloxacin in patients with human immunodeficiency virus infection
Authors: Goodwin S D , Gallis H A , Chow A T , Wong F A , Flor S C , Bartlett J A
Published: June 2012

Levofloxacin, the bacteriologically active isomer of ofloxacin, has microbiologic activity against many pathogens common in human immunodeficiency virus (HIV)-infected patients, including Mycoplasma species which may be cofactors in the progression of HIV disease. The purpose of this phase I, double-blind, randomized (1:1), placebo-controlled trial was to evaluate the pharmacokinetics and safety of levofloxacin hemihydrate in 10 asymptomatic HIV-infected males. Plasma concentrations by chiral high-performance liquid chromatography (HPLC) were evaluated for 48 h after a single 350-mg oral dose, at morning predose during the multiple-dosing phase, and for 72 h at steady state after a week of 350 mg every 8 h orally. Mean +/- standard deviation levofloxacin pharmacokinetic parameters (by noncompartmental moment method) after multiple dosing were as follows: area under the concentration-time curve, 31.24 +/- 5.60 mg.h/liter; apparent total body clearance, 11.18 +/- 1.76 liters/h; renal clearance, 8.63 +/- 2.82 liters/h; steady-state volume of distribution, 104.10 +/- 12.48 liters; and effective half-life, 6.50 +/- 0.51 h. Single-dose parameters were not significantly different from the multiple-dose parameters, with the exception of peak concentrations in plasma, which were 4.79 +/- 1.00 and 6.92 +/- 1.56 mg/liter for single- and multiple-dose data, respectively. Essentially identical parameter values were obtained from curve-fitting analysis when the entire 13-day plasma concentration profiles of the subjects were analyzed simultaneously by a two-compartmental distribution model. Levofloxacin pharmacokinetics in HIV-infected patients remained linear upon multiple dosing. The dosing regimen studied provides levels in plasma and urine well above those found to be effective in vitro against pathogens common in HIV-infected patients. Levofloxacin was well- tolerated in this group of asymptomatic HIV-infected males: there were no statistically significant differences in adverse effects in the two groups (P = 0.22). Use of placebo control helped to differentiate disease-related adverse effects from those related to the study drug.
Behavior of antibiotics during human necrotizing pancreatitis
Authors: Bassi C , Pederzoli P , Vesentini S , Falconi M , Bonora A , Abbas H , Benini A , Bertazzoni E M
Published: June 2012

The aim of the study was to verify whether antibiotics excreted by the normal pancreas are also excreted in human necrotizing pancreatitis, reaching the tissue sites of the infection. Twelve patients suffering from acute necrotizing pancreatitis were treated with imipenem-cilastatin (0.5 g), mezlocillin (2 g), gentamicin (0.08 g), amikacin (0.5 g), pefloxacin (0.4 g), and metronidazole (0.5 g). Serum and necrotic samples were collected simultaneously at different time intervals after parenteral drug administration by computed tomography-guided needle aspiration, intraoperatively, and from surgical drainages placed during surgery. Drug concentrations were determined by microbiological and high-performance liquid chromatography assays. All antibiotics reached the necrotic tissues, but with varying degrees of penetration, this being low for aminoglycosides (13%) and high in the case of pefloxacin (89%) and metronidazole (99%). The concentrations of pefloxacin (13.0 to 23 micrograms/g) and metronidazole (8.4 micrograms/g) in the necrotic samples were distinctly higher than the MICs for the organisms most commonly isolated in this disease; the concentrations in tissue of imipenem (3.35 micrograms/g) and mezlocillin (8.0 and 15.0 micrograms/g) did not always exceed the MICs for 90% of strains tested, whereas the aminoglycoside concentrations in necrotic tissue (0.5 microgram/g) were inadequate. Repeated administration of drugs (for 3, 7, 17, and 20 days) seems to enhance penetration of pefloxacin, imipenem, and metronidazole into necrotic pancreatic tissue. The choice of antibiotics in preventing infected necrosis during necrotizing pancreatitis should be based on their antimicrobial activity, penetration rate, persistence, and therapeutic concentrations in the necrotic pancreatic area. These requisites are provided by pefloxacin and metronidazole and to a variable extent by imipenem and mezlocillin.
Susceptibilities of bacterial isolates from patients with cancer to levofloxacin and other quinolones
Authors: Dholakia N , Rolston K V , Ho D H , LeBlanc B , Bodey G P
Published: June 2012

The antibacterial activity of levofloxacin was compared with those of ofloxacin and ciprofloxacin against bacterial isolates from patients with cancer. In general, levofloxacin was as active or was twofold more active than ofloxacin and was two- to fourfold less active than ciprofloxacin against most gram-negative pathogens. Against Pseudomonas aeruginosa, ciprofloxacin was the most active agent tested (MIC for 90% of isolates tested, 1.0 microgram/ml). Overall, all three agents had similar activities against gram-positive organisms and were moderately active against methicillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci, Streptococcus species, and Enterococcus species.
Regulation of herpes simplex virus thymidine kinase in cells treated with a synergistic antiviral combination of alpha interferon and acyclovir
Authors: Taylor J L , Tom P , Guy J , Selvarajan R M , O'Brien W J
Published: June 2012

Alpha interferon (IFN-alpha) and acyclovir (ACV) are synergistic in their anti-herpes simplex virus activities. IFN-alpha treatment reduced the herpes simplex virus thymidine kinase (TK) activity present in cells 6 h postinfection, while steady-state levels of TK mRNA remained at or above the amount in infected, untreated cells. The inhibition of TK production by IFN-alpha treatment appeared to be transient and translational, not transcriptional.
Influence of stereochemistry on antiviral activities and resistance profiles of dideoxycytidine nucleosides
Authors: Van Draanen N A , Tisdale M , Parry N R , Jansen R , Dornsife R E , Tuttle J V , Averett D R , Koszalka G W
Published: June 2012

beta-L-2',3'-Dideoxycytidine (beta-L-ddC) and beta-L-5-fluoro-2',3'-dideoxycytidine (5-F-beta-L-ddC) were prepared and shown to have potent activity against human immunodeficiency virus type 1 (HIV-1) and hepatitis B virus (HBV). These compounds were compared with beta-D-2',3'-dideoxycytidine (beta-D-ddC) and two beta-L-oxathiolane nucleosides (beta-L-3'-thio-2',3'-dideoxycytidine and beta-L-5-fluoro-3'-thio-2',3'-dideoxycytidine) in terms of anti-HIV and anti-HBV activity, cytotoxicity, and development of HIV-1 resistance. Compared with beta-D-ddC, the beta-L-dideoxycytidine nucleosides had similar anti-HIV-1 activities, significantly greater anti-HBV activities, and decreased toxicities to a B-cell line, T-cell lines, and human bone marrow progenitor cells. HIV-1 strains resistant to beta-D-ddC were susceptible to the beta-L-ddC analogs. Compared with the beta-L-oxathiolane nucleosides, beta-L-ddC and 5-F-beta-L-ddC had similar anti-HIV-1 activities, decreased anti-HBV activities, and greater toxicities to B- and T-cell lines and bone marrow progenitor cells. There were similarities between the beta-L-ddC and beta-L-oxathiolane nucleosides in the rate of development and pattern of resistant HIV-1 selection. While the in vitro activity and cytotoxicity profiles of the beta-L-ddC nucleosides differed from those of the beta-D-ddC and beta-L-oxathiolane nucleosides, the data presented herein suggest that the sugar configuration of a dideoxynucleoside analog may play a major role in the rate of development and the pattern of HIV-1 resistance.
Penetration of ciprofloxacin into bronchial secretions from mechanically ventilated patients with nosocomial bronchopneumonia
Authors: Saux P , Martin C , Mallet M N , Papazian L , Bruguerolle B , De Micco P , Gouin F
Published: June 2012

The aim of the study was to evaluate the penetration of ciprofloxacin into bronchial secretions from mechanically ventilated patients with nosocomial bronchopneumonia. For this purpose, in each patient studied, simultaneous serial blood and bronchial secretion samples were obtained over a 12-h period on days 2 and 4. Eight patients were included in the study. Ciprofloxacin was given at a dose of 200 mg over 30 min by using an automatic pump. Ciprofloxacin was measured by high-performance liquid chromatography. Peak levels of drug in serum were 2.95 +/- 1 mg/liter on day 2 and 2.43 +/- 0.7 mg/liter on day 4. Peak and trough levels in bronchial secretions were 0.95 +/- 0.51 and 0.21 +/- 0.12 mg/liter, respectively, on day 2 and 0.76 +/- 0.17 and 0.18 +/- 0.14 mg/liter, respectively, on day 4. The ratios of peak concentrations in bronchial secretions/serum were 0.32 +/- 0.11 and 0.33 +/- 0.06 on days 2 and 4, respectively. The ratios of the area under the concentration-time curve from 0 to 12 h (AUC0-12) for bronchial secretions/those for serum were 0.66 +/- 0.40 and 0.55 +/- 0.30 on days 2 and 4, respectively. A significant positive correlation was found on day 4 between the AUC0-12 for serum and the AUC0-12 for bronchial secretions. No significant correlations were found between peak values in serum and bronchial secretions.
Biofilm accumulation model that predicts antibiotic resistance of Pseudomonas aeruginosa biofilms
Authors: Stewart P S
Published: June 2012

A computer model of biofilm dynamics was adapted to incorporate the activity of an antimicrobial agent on bacterial biofilm. The model was used to evaluate the plausibility of two mechanisms of biofilm antibiotic resistance by qualitative comparison with data from a well-characterized experimental system (H. Anwar, J. L. Strap, and J. W. Costerton, Antimicrob. Agents Chemother. 36:1208-1214, 1992). The two mechanisms involved either depletion of the antibiotic by reaction with biomass or physiological resistance due to reduced bacterial growth rates in the biofilm. Both mechanisms predicted the experimentally observed resistance of 7-day-old Pseudomonas aeruginosa biofilms compared with that of 2-day-old ones. A version of the model that incorporated growth rate-dependent killing predicted reduced susceptibility of thicker biofilms because oxygen was exhausted within these biofilms, leading to very slow growth in part of the biofilm. A version of the model that incorporated a destructive reaction of the antibiotic with biomass likewise accounted for the relative resistance of thicker biofilms. Resistance in this latter case was due to depletion of the antibiotic in the bulk fluid rather than development of a gradient in the antibiotic concentration within the biofilm. The modeling results predicted differences between the two cases, such as in the survival profiles within the biofilm, that could permit these resistance mechanisms to be experimentally distinguished.
In vitro activities of two glycylcyclines
Authors: Wise R , Andrews J M
Published: June 2012

The in vitro activities of two glycylcyclines, CL 329,998 and CL 331,002 (two new semisynthetic tetracyclines), were evaluated in comparison with those of tetracycline and other available oral antimicrobial agents. A total of 523 recent clinical isolates were studied, including strains resistant to tetracycline. Members of the family Enterobacteriaceae were generally > or = 16-fold more susceptible to the glycylcyclines than to tetracycline (although less difference was seen with Proteus spp.). Pseudomonas aeruginosa was modestly susceptible to both new compounds (MIC for 90% of strains tested [MIC90], 16 micrograms/ml). Tetracycline- and methicillin-susceptible and -resistant strains of Staphylococcus aureus were all susceptible to the glycylcyclines (MIC90 < or = 1 microgram/ml). Streptococci (including Streptococcus pneumoniae) and Enterococcus faecalis and Enterococcus faecium displayed a bimodal distribution of susceptibility to tetracycline yet were uniformly susceptible to the glycylcyclines (MIC90 < or = 0.25 microgram/ml). The glycylcyclines were highly potent against Neisseria, Moraxella, Haemophilus, and Bacteroides spp. (MIC90 < or = 0.5 microgram/ml). Strains of Chlamydia spp. (three C. trachomatis strains and one C. pneumoniae strain) were inhibited by < or = 0.25 microgram of CL 329,998 or CL 331,002 per ml. Two strains of Mycoplasma pneumoniae were inhibited by < or = 0.12 microgram of CL 331,002 per ml and by 1 microgram of CL 329,998 per ml. Mycobacterium tuberculosis and Mycobacterium avium were resistant to the two glycylcyclines (MIC > or = 8 micrograms/ml). These results indicate that the two glycylcyclines have potent in vitro activities against a wide range of clinically important pathogenic bacteria.
Treatment of experimental endocarditis due to penicillin-resistant Streptococcus pneumoniae
Authors: Fernández Guerrero M L , Arbol F , Verdejo C , Fernández Roblas R , Soriano F
Published: June 2012

Using two strains of pneumococci for which MICs of penicillin were 1 and 4 micrograms/ml, those of cefotaxime were 0.01 and 0.5 micrograms/ml, and those of teicoplanin were 0.01 and 0.1 micrograms/ml, we studied the efficacy of different dosages of penicillin, cefotaxime, and teicoplanin in the treatment of experimental pneumococcal endocarditis in rabbits. Animals treated with dosages of penicillin G procaine needed to achieve levels in serum near the MIC for pneumococci showed a significant reduction in log10 CFU per gram of vegetation, as compared with the control (P < 0.001), although only 20% of the animals showed sterile vegetations. When levels of penicillin in serum were in the range of three- to fourfold the MIC, a greater reduction in log10 CFU per gram of vegetation was seen, and 88% of the animals showed sterile vegetations. Only the regimen of penicillin that provided concentrations in serum above the MIC throughout the interval between two doses provided constant sterilization of the cardiac vegetations. Dosages of cefotaxime and teicoplanin selected to achieve concentrations in serum equivalent to that obtained in humans during treatment resulted in levels of antimicrobial agents in serum hundreds or thousands of times higher than the MICs for the infecting strains. In terms of antimicrobial efficacy, cefotaxime and teicoplanin were equivalent to regimens with high dosages of penicillin.
Protein binding of human immunodeficiency virus protease inhibitor KNI-272 and alteration of its in vitro antiretroviral activity in the presence of high concentrations of proteins
Authors: Kageyama S , Anderson B D , Hoesterey B L , Hayashi H , Kiso Y , Flora K P , Mitsuya H
Published: June 2012

KNI-272 represents a peptide-based protease inhibitor having potent antiretroviral activity against human immunodeficiency virus (HIV) in vitro. The structure contains allophenylnorstatine [(2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid] with a hydroxymethylcarbonyl isostere. We asked whether this experimental anti-HIV agent could exert its activity in vitro in the presence of relatively high concentrations of fetal calf serum (FCS) and assessed its protein-binding properties by using fresh human plasma preparations. The 50 and 75% inhibitory concentrations of KNI-272 against HIV type 1 replication in vitro were 3- to 5-fold and 5-fold higher in the presence of 50% FCS and 15- to 25-fold and 25- to 100-fold higher in the presence of 80% ECS, respectively, than those with 15% FCS, whereas the antiviral activity of 2',3'-dideoxyinosine was not significantly affected by FCS concentrations in the culture. Detailed studies of the protein binding of KNI-272 suggest that in human plasma binding occurs predominantly to alpha 1-acid glycoprotein and that KNI-272 is probably extensively (approximately 98 to 99%) protein bound at concentrations likely to be achieved in the circulation. Thus, higher levels of KNI-272 in plasma may be required when this compound undergoes clinical trials relative to those inferred from in vitro data involving the use of 10 to 15% FCS-containing culture media. The current data may have a relevance to other antiretroviral drugs that are under development and that have a high protein-binding capacity.
Effects of pentamidine isethionate on Saccharomyces cerevisiae
Authors: Ludewig G , Williams J M , Li Y , Staben C
Published: June 2012

We used Saccharomyces cerevisiae as a model system in which to examine the mechanism of action of the anti-Pneumocystis drug pentamidine. Pentamidine at low concentrations inhibited S. cerevisiae growth on nonfermentable carbon sources (50% inhibitory concentration [IC50] of 1.25 micrograms/ml in glycerol). Pentamidine inhibited growth on fermentable energy sources only at much higher concentrations (IC50 of 250 micrograms/ml in glucose). Inhibition at low pentamidine concentrations in glycerol was due to cytostatic activity rather than cytotoxic or mutagenic activity. Pentamidine also rapidly inhibited respiration by intact yeast cells, although inhibitory concentrations were much higher than those inhibitory to growth (IC50 of 100 micrograms/ml for respiration). Pentamidine also induced petite mutations, although only at concentrations much higher than those required for growth inhibition. These results suggest that a function essential for respiratory growth is inhibited by pentamidine and that pentamidine affects mitochondrial processes. We propose the hypothesis that the primary cellular target of pentamidine in S. cerevisiae is the mitochondrion.
Susceptibility testing of Dientamoeba fragilis ATCC 30948 with iodoquinol, paromomycin, tetracycline, and metronidazole
Authors: Chan F T , Guan M X , Mackenzie A M , Diaz-Mitoma F
Published: June 2012

Susceptibility testing was performed on Dientamoeba fragilis ATCC 30948 in a dixenic culture with Klebsiella pneumoniae and Bacteroides vulgatus. D. fragilis was cocultured with the bacteria in TYGM-9 medium (ATCC medium 1171). The activities of antiparasitic drugs were assessed by counting viable D. fragilis trophozoites with a hemacytometer by trypan blue exclusion. The minimal amebicidal concentrations of the following four drugs were determined: iodoquinol at 128 micrograms/ml, paromomycin at 16 micrograms/ml, tetracycline (questionably) at 32 micrograms/ml, and metronidazole at 32 micrograms/ml.
Oral LY217896 for prevention of experimental influenza A virus infection and illness in humans
Authors: Hayden F G , Tunkel A R , Treanor J J , Betts R F , Allerheiligen S , Harris J
Published: June 2012

The efficacy and safety of oral LY217896 for prevention of experimental influenza A/Kawasaki/86 (H1N1) virus infection were assessed in susceptible males randomly assigned to receive LY217896 (75 mg) or placebo once daily for 7 days beginning 24 h prior to viral challenge. The rates of virus shedding (100% in both groups), days of viral shedding (3.1 +/- 1.3 for the LY217896 group; 2.8 +/- 1.3 for the placebo group), and titers of virus in nasal washings did not differ between the groups. Mild upper respiratory tract illness (72% in the LY217896 group; 69% in the placebo group) developed in similar proportions of each group. LY217896 was associated with asymptomatic rises in serum uric acid levels and was ineffective in modifying the virologic or clinical course of experimental influenza A (H1N1) virus infection.
Cloning and sequence analysis of blaBIL-1, a plasmid-mediated class C beta-lactamase gene in Escherichia coli BS
Authors: Fosberry A P , Payne D J , Lawlor E J , Hodgson J E
Published: June 2012

The extended-spectrum, plasmid-borne beta-lactamase gene blaBIL-1, which was discovered in Escherichia coli, has been cloned. Unusually for a plasmid-borne beta-lactamase, blaBIL-1 encodes a novel class C enzyme and appears to have originated from the chromosomal ampC gene of Citrobacter freundii.
Molecular characterization of the gene encoding high-level mupirocin resistance in Staphylococcus aureus J2870
Authors: Hodgson J E , Curnock S P , Dyke K G , Morris R , Sylvester D R , Gross M S
Published: June 2012

The nucleotide sequence of the ileS gene conferring high-level resistance to mupirocin in Staphylococcus aureus J2870 has been determined. The gene sequence is substantially different from that of the native ileS gene of S. aureus, indicating that high-level resistance to mupirocin results from the acquisition of a novel ileS gene.
Killing of Pseudomonas aeruginosa during continuous and intermittent infusion of ceftazidime in an in vitro pharmacokinetic model
Authors: Mouton J W , den Hollander J G
Published: June 2012

An in vitro pharmacokinetic model mimicking human serum drug concentrations, based on a dialyzer unit, was developed to study the efficacies of continuous infusion and intermittent administration of ceftazidime over a period of 36 h. The daily dose of ceftazidime was 300 mg/liter/24 h given either as a continuous infusion or as three bolus doses. The intermittent dosing regimen yielded peak and trough concentrations after the fourth dose of 92.3 (standard deviation, 8.0) and 1.4 (standard deviation, 0.9) mg/liter, respectively. Continuous administration yielded concentrations of approximately 20 mg/liter. To study efficacy, three Pseudomonas aeruginosa strains, ATCC 27853, CF4, and CF16, were used. The MICs of ceftazidime for these strains were 1, 4, and 16 mg/liter, respectively. Strain CF16 was killed initially during both regimens and then started to regrow. At the end of the fourth dosing interval, i.e., after 32 h, viable counts showed no difference between the regimens. Strains ATCC 27853 and CF4 were killed initially during both dosing schedules, and after the first dosing interval viable counts were similar. However, after the fourth interval, there was a marked difference between bacterial counts during continuous and intermittent infusion, being 2.2 and 2.8 log10, respectively, demonstrating a greater efficacy during continuous infusion. The results indicate that, in the absence of other factors, a sustained level of ceftazidime around or slightly above the MIC is not high enough to maintain efficacy over more than one (8-h) dosing interval. When sustained concentrations higher than four times the MIC are employed, continuous administration in this model is more efficacious than intermittent dosing.
Characterization and cilofungin inhibition of solubilized Aspergillus fumigatus (1,3)-beta-D-glucan synthase
Authors: Beaulieu D , Tang J , Yan S B , Vessels J M , Radding J A , Parr T R
Published: June 2012

(1,3)-beta-D-Glucan synthase, a major cell wall synthesis enzyme, is the target of antifungal drugs of the lipopeptide class. Aspergillus fumigatus (1,3)-beta-D-glucan synthase was prepared and its activity was measured by incorporation of [14C]glucose from UDP-[U-14C]glucose into an insoluble polymer in the presence of alpha-amylase. Solubilization of the (1,3)-beta-D-glucan synthase was attempted with several detergents, and the maximum percent solubilization was obtained with a polyoxyethylene ether detergent, W-1. Up to 70% of enzyme activity and 50% of total protein were recovered when 1-mg/ml membrane preparations were extracted with 0.045% W-1 at 4 degrees C overnight. Confirmation of the presence of a (1,3)-beta-D-glucose polymer synthesized by this glucan synthase was done by three methods. The first was enzymatic end product degradation by alpha-amylase (no degradation) and beta-glucanase (85 to 95% degradation). The second was gas chromatography-mass spectroscopy analysis of the partially methylated alditol acetate derivatives prepared from total carbohydrate polymers present in the sample. This method identified the presence of (1,3)- and (1,2)-glucosidic linkages. The third was high-performance anion exchange chromatography of radioactive oligosaccharides. This method allowed differentiation of the newly synthesized, radioactive polymers from the contaminating carbohydrates already present in the preparation. The results showed that the polymer synthesized comprised oligosaccharides consistent with beta-(1,3)-linked sugars. Maximal inhibition of the (1,3)-beta-D-glucan synthase by the lipopeptide antifungal agent cilofungin was 80%. Dose-response experiments with this inhibitor showed that the solubilized enzyme was maximally inhibited at a cilofungin concentration of 1.25 microgram/ml and showed <5% inhibition at 0.02 microgram/ml. The apparent K(m) (K(m app)) for the solubilized glucan synthase was 400 +/- 80 microM, and the apparent K(i) (K(i app)) for cilofungin was 0.19 +/- 0.03 microM. Inhibition of A.fumigatus (1,3)-beta-D-glucan synthase with cilofungin was noncompetitive, as it was for the Candida albicans (1,3)-beta-D-glucan synthase.
Influence of diet on experimental toxicity of amphotericin B deoxycholate
Authors: Chavanet P , Joly V , Rigaud D , Bolard J , Carbon C , Yeni P
Published: June 2012

The effects of pre- and postprandial levels of lipids in serum on the experimental in vivo and in vitro toxicities of amphotericin B deoxycholate (AmB-d) were studied. Normal OF1 mice were tested at baseline, after normal feeding, after 3 h of fasting, or after a sequence of feeding and fasting and vice versa. The 50% lethal dose (LD50) of AmB-d was significantly higher in fed mice than in mice which fasted or at baseline (2.38 +/- 0.12 versus 1.53 +/- 0.2 and 1.50 +/- 0.1 mg/kg of body weight, respectively; P < 0.05). When different nutritional regimens were alternated over a short period, the level of in vivo AmB-d toxicity was dictated by the last feeding regimen. Serum triglycerides, but not cholesterol in very-low-density and low-density lipoproteins, correlated significantly (P < 0.01) with the LD50 of AmB. In vitro experiments showed that the addition of human serum reduced AmB-d-induced toxicity against human erythrocytes, but serum drawn after fasting was less protective than postprandial serum. However, neither serum decreased the in vitro activity of AmB-d against Candida albicans. Circular dichroism, a method that enables the amount of free AmB to be measured, showed that both mouse and human total serum lipoproteins bound more AmB-d when serum was isolated postprandially than when it was obtained after fasting. Our results show that AmB-d toxicity is reduced by feeding-induced modifications in serum lipids. The influence of food intake on the clinical toxicity of the drug merits being investigated.
Molecular characterization of rifampin-resistant Neisseria meningitidis
Authors: Carter P E , Abadi F J , Yakubu D E , Pennington T H
Published: June 2012

Primers were designed to amplify the rpoB gene of Neisseria meningitidis. The region of the gene amplified covered clusters I and II of the rifampin resistance (Rifr) mutation sites identified in Escherichia coli. DNAs from six Rifr isolates and 21 rifampin-susceptible isolates from the United Kingdom representing a number of serogroups were amplified and sequenced. All six Rifr isolates had identical DNA sequences and the same amino acid change, a His to an Asn change at position 35 (H35N). This His residue is equivalent to the His residue at position 526 in E. coli, one of the known Rifr mutation sites. DNAs from an additional six Rifr mutations generated in vitro were amplified and sequenced. Three had H35Y changes, one had an H35R change, one had an H35N change and one had an S40F change. The predominance of mutations at the His residue at position 35 in Rifr N. meningitidis isolates suggests that it plays a critical role in the selection of antibiotic-resistant variants. All six Rifr isolates belonged to the same clonal group when analyzed by restriction enzyme analysis and pulsed-field gel electrophoresis. These data suggest that a single clone of Rifr N. meningitidis is present and widespread throughout the United Kingdom.
Effects of U-75875, a peptidomimetic inhibitor of retroviral proteases, on simian immunodeficiency virus infection in rhesus monkeys
Authors: Martin L N , Soike K F , Murphey-Corb M , Bohm R P , Roberts E D , Kakuk T J , Thaisrivongs S , Vidmar T J , Ruwart M J , Davio S R
Published: June 2012

U-75875 inhibits human immunodeficiency virus types 1 and 2 and simian immunodeficiency virus (SIV) proteases and blocks Gag-Pol protein processing and viral maturation and replication in vitro. Rhesus monkeys were treated with vehicle alone or with formulated U-75875 at doses of 7 or 20 mg/kg of body weight per day for 26 days by continuous intravenous infusion beginning 6 h prior to intravenous inoculation with 10 monkey 50% infectious doses of SIV Delta B670, and the monkeys were monitored until death. The effects of treatment on the level of SIV p26 antigenemia, the infectious virus titer in serum, and the level of proviral DNA in blood mononuclear cells evaluated by PCR were assessed. SIV infection of the controls resulted in an initial viral antigenemia that began 5 to 10 days postinoculation (p.i.), reached peak values on days 10 to 14 p.i., and lasted for more than 15 days. Proviral DNA was detectable in peripheral blood mononuclear cells by 7 to 11 days p.i., reached the mean peak level by 11 days p.i., and remained at high levels through day 24 p.i. Infectious virus was detected in serum from all of the infected controls by 24 days p.i. Treatment with U-75875 for 26 days resulted in a dose-related delay in the day of the peak level of antigenemia (P = 0.034). The level of proviral DNA in peripheral blood mononuclear cells at 11 days p.i. was significantly decreased in a dose-related fashion in the treated monkeys ( P </- 0.048), with a delay in the attainment of the peak level of proviral DNA in the treated groups. The titer of infectious virus in the serum of the group treated with 20 mg/kg/day was significantly decreased on day 24 p.i. compared with that in the serum of controls ( P = 0.046). Treatment with formulated U-75875 was well tolerated in rhesus monkeys and resulted in an inhibitory effect of SIV in vivo.
Anti-human immunodeficiency virus activities of the beta-L enantiomer of 2',3'-dideoxycytidine and its 5-fluoro derivative in vitro
Authors: Gosselin G , Schinazi R F , Sommadossi J P , Mathé C , Bergogne M C , Aubertin A M , Kirn A , Imbach J L
Published: June 2012

The L enantiomer of 2',3'-dideoxycytidine (DDC) was recently shown to inhibit selectively human immunodeficiency virus type 1 (HIV-1) in vitro. In the current study, the potent anti-HIV activity of L-DDC was confirmed and extended to several HIV-1 and HIV-2 strains in various cell culture systems, including primary human lymphocytes and macrophages. Furthermore, its 5-fluoro congener, beta-L-2',3'-dideoxy-5-fluorocytidine (L-FDDC), was found to have more potent anti-HIV activity and a higher therapeutic index in acutely infected human peripheral blood mononuclear cells. These compounds had no marked activity against HIV-1 isolates resistant to the oxathiolane pyrimidine nucleosides (-)-beta-L-2',3'-dideoxy-5-fluoro-3'-thiacytidine [(-)-FTC] and (-)-beta-L-2',3'-dideoxy-3'-thiacytidine, but 3'-azido-3'-deoxythymidine (AZT)-resistant viruses were susceptible to L-DDC and L-FDDC. Cytotoxicity studies with human myeloid progenitor cells indicated that L-DDC and L-FDDC had median inhibitory concentrations comparable to those of AZT, DDC, and FDDC, but L-DDC and L-FDDC were significantly less toxic than AZT, DDC, and FDDC when erythroid progenitor cells were used. L-FDDC had the highest selectivity indices (6,000 and 9,000 for erythroid and myeloid progenitor cells, respectively) of all the compounds evaluated. Further preclinical development of L-FDDC is warranted in order to determine its potential usefulness in the treatment of HIV infections.
Comparative prophylactic efficacies of ciprofloxacin, ofloxacin, cefazolin, and vancomycin in experimental model of staphylococcal wound infection
Authors: Kernodle D S , Kaiser A B
Published: June 2012

Recent shifts in the species and antibiotic resistance patterns of bacteria causing nosocomial infections present new challenges for providing effective prophylaxis in surgery. Traditional regimens lack activity against methicillin-resistant staphylococci and many gram-negative species causing nosocomial infections. The new fluoroquinolones exhibit in vitro activity against many emerging surgical wound pathogens. To determine the potential of this class of antimicrobial agents for use in surgery, we compared the prophylactic efficacies of ciprofloxacin and ofloxacin with those of cefazolin and vancomycin in a guinea pig model of abscess formation. Four Staphylococcus aureus strains, one Staphylococcus epidermidis strain, and one Staphylococcus haemolyticus strain were evaluated. Vancomycin was the most effective prophylactic agent, exhibiting in vivo activity against all strains which was superior or equivalent to those of all other agents tested. Cefazolin was the least effective agent and surpassed the two quinolones in prophylactic efficacy against only one organism, a quinolone- and methicillin-resistant strain of S. aureus. The two quinolones provided excellent protection against infection with all but the quinolone-resistant isolate. The in vivo emergence of quinolone resistance among quinolone-susceptible isolates was not detected. The methicillin-resistant, quinolone-susceptible S. epidermidis and S. haemolyticus isolates were extremely susceptible to prophylaxis, exhibiting 50% infective doses above 4 x 10(6) CFU for seven of the eight antibiotic-strain combinations. We conclude that ciprofloxacin and ofloxacin may be effective antistaphylococcal agents in surgery. The role of these agents remains to be defined, and the definition should include consideration of an adverse effect upon antibiotic resistance patterns of organisms causing nosocomial infections.
Interaction of oxyimino beta-lactams with a class C beta-lactamase and a mutant with a spectrum extended to beta-lactams
Authors: Nukaga M , Tsukamoto K , Yamaguchi H , Sawai T
Published: June 2012

The class C beta-lactamase of Citrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids, and substitution of the glutamic acid at position 219 in the enzyme by lysine was previously shown to broaden its substrate spectrum to oxyimino beta-lactams (K. Tsukamoto, R. Ohno, and T. Sawai, J. Bacteriol. 172:4348-4351, 1990). To clarify this spectrum extension from the kinetic point of view, the interactions of cefuroxime, ceftazidime, and aztreonam with the wild-type and mutant enzymes were analyzed. In addition to aztreonam, known as a progressive inhibitor of class C beta-lactamases, cefuroxime and ceftazidime were found to act as progressive inhibitors of the wild-type enzyme. On the other hand, only aztreonam showed weak progressive inhibition of the mutant enzyme. On the basis of kinetic parameters, a minimum scheme for interaction of the oxyimino beta-lactams with the wild-type enzyme was proposed, and the rate-limiting step of the hydrolysis of unfavorable substrates was indicated to be conversion of the stable acyl-enzyme intermediate to the unstable intermediate. In aztreonam hydrolysis by the mutant enzyme, the reaction rate at the rate-limiting step was 2,000 times that of the wild-type enzyme. These results indicate that the mutation at position 219 disturbs the stabilization of the stable intermediate.
Susceptibilities of human immunodeficiency virus type 1 enzyme and viral variants expressing multiple resistance-engendering amino acid substitutions to reserve transcriptase inhibitors
Authors: Byrnes V W , Emini E A , Schleif W A , Condra J H , Schneider C L , Long W J , Wolfgang J A , Graham D J , Gotlib L , Schlabach A J
Published: June 2012

To evaluate the potential that multiply resistant human immunodeficiency virus type 1 variants may arise during combination nucleoside and nonnucleoside reverse transcriptase inhibitor therapy, we constructed a series of mutant reverse transcriptase enzymes and viruses that coexpressed various combinations of resistance-associated amino acid substitutions. Substitutions at residues 100 (Leu-->Ile) and 181 (Tyr-->Cys), which mediate resistance to the nonnucleosides, suppressed resistance to 3'-azido-3'-deoxythymidine (AZT) when coexpressed with AZT-specific substitutions. However, a number of viral variants that exhibited significantly reduced susceptibilities to both classes of inhibitors were constructed.
Comparative antirhinoviral activities of soluble intercellular adhesion molecule-1 (sICAM-1) and chimeric ICAM-1/immunoglobulin A molecule
Authors: Crump C E , Arruda E , Hayden F G
Published: June 2012

We conducted a comparative study of the antirhinovirus activities of soluble intercellular adhesion molecule-1 (sICAM-1) and a chimeric ICAM-1/immunoglobulin A (IgA) molecule (ICI-5D/IgA) for nine major receptor group human rhinovirus (HRV) serotypes and for a variant of HRV-39 relatively resistant to inhibition by sICAM-1. ICI-5D/IgA inhibited the infectivity of eight of the nine wild-type HRVs and the resistant HRV-39 variant and was 60 to 170 times more potent than sICAM-1 on a molar basis. In contrast to sICAM-1, ICI-5D/IgA directly neutralized the infectivity of the representative HRVs by approximately 1 log10. These results expand on the antirhinovirus spectrum of ICI-5D/IgA, confirm that dimeric forms of sICAM-1 have a higher antirhinoviral potency than monomeric sICAM-1, and indicate that cross-linking of two adjacent receptor binding sites on the virus capsid by a divalent receptor enhances the direct inactivation of viral infectivity.
Novel mutation (V75T) in human immunodeficiency virus type 1 reverse transcriptase confers resistance to 2',3'-didehydro-2',3'-dideoxythymidine in cell culture
Authors: Lacey S F , Larder B A
Published: June 2012

We have selected a human immunodeficiency virus type 1 (HIV-1) mutant strain with a moderate (sevenfold) level of resistance to the nucleoside analog 2',3'-didehydro-2',3'-dideoxythymidine (D4T or stavudine). After serial passage of the HXB2 strain of HIV-1 in MT4 cells, a novel mutation involving two nucleotide substitutions in codon 75 of the viral reverse transcriptase, altering valine to threonine, was seen. When introduced into a wild-type HIV-1 background by site-directed mutagenesis, the T-75 mutation conferred cross-resistance to the dideoxynucleosides dideoxyinosine and dideoxycytosine as well as to 2',3'-didehydro-2',3'-dideoxycytosine.
Comparative activities of eight quinolones against members of the Bacteroides fragilis group
Authors: Borobio M V , Conejo M , Ramirez E , Suarez A I , Perea E J
Published: June 2012

The in vitro activities of five new quinolones (clinafloxacin [CI-960 or PD-127391], BAY Y 3118, E-4868, E-5065, and E-5068) against 100 Bacteroides fragilis group bacterial isolates were compared with those of ciprofloxacin, ofloxacin, and sparfloxacin. Overall, E-5068 was the most active in vitro (MIC for 90% of isolates tested [MIC90], 0.25 microgram/ml); this was followed by clinafloxacin and BAY Y 3118 (MIC90, 0.5 microgram/ml). Ciprofloxacin, sparfloxacin, and ofloxacin were the least active (MIC90s, 64, 16, and 16 micrograms/ml, respectively). B. fragilis and Bacteroides caccae were more susceptible than the other members of the B. fragilis group to all of the quinolones tested.
Comparative activities of azithromycin and clarithromycin against Mycobacterium avium infection in beige mice
Authors: Cynamon M H , Klemens S P , Grossi M A
Published: June 2012

The comparative activities of azithromycin (AZI) and clarithromycin (CLA) against eight Mycobacterium avium complex (MAC) isolates were evaluated in the beige mouse model of disseminated infection. Mice were infected intravenously with approximately 10(7) viable MAC isolate. AZI at 100 or 200 mg/kg of body weight or CLA at 200 mg/kg of body weight was given by gavage daily for 10 days starting at 7 days postinfection. In each study, groups of treated mice were compared with untreated control animals. A dose-related reduction in organism cell counts in the spleens between the groups receiving AZI at 100 and 200 mg/kg was observed. AZI at 200 mg/kg was more active than CLA at 200 mg/kg against six of eight MAC isolates in the spleens. CLA at 200 mg/kg was more active than AZI at 200 mg/kg against three of eight MAC isolates in the lungs. The difference between AZI at 200 mg/kg and CLA at 200 mg/kg against organisms in the lungs was not significant for the remaining five isolates. Clinical trials comparing the activities of AZI and CLA in combination with other agents in patients with disseminated MAC infection are necessary to ascertain any clinically significant differences in the efficacies of these agents.