bluuebunny/crossref_metadata_2025 huggingface dataset:
Point mutation in the pribnow box, the molecular basis of beta-lactamase overproduction in Klebsiella oxytoca
Authors: Fournier B , Lu C Y , Lagrange P H , Krishnamoorthy R , Philippon A
Published: June 2012

Klebsiella oxytoca mutants resistant to a variety of beta-lactams were obtained in vitro on aztreonam. Constitutive beta-lactamase production was much higher in the mutants than in the susceptible strains (75-fold). The only difference observed in these mutants compared with the susceptible strains were point mutations in the Pribnow box: a transversion (G-->T) in the first base for one mutant or a transition (G-->A) in the fifth base of the -10 consensus sequence for the other three mutants. The transcriptional output of the beta-lactamase gene (blaOXY) from the mutants was significantly higher than that of the blaOXY gene from the susceptible strains.
SDZ PRI 053, an orally bioavailable human immunodeficiency virus type 1 proteinase inhibitor containing the 2-aminobenzylstatine moiety
Authors: Billich A , Fricker G , Müller I , Donatsch P , Ettmayer P , Gstach H , Lehr P , Peichl P , Scholz D , Rosenwirth B
Published: June 2012

A series of inhibitors of human immunodeficiency virus type 1 (HIV-1) proteinase containing the 2-aralkyl-amino-substituted statine moiety as a novel transition-state analog was synthesized, with the aim to obtain compounds which combine anti-HIV potency with oral bioavailability. The reduced-size 2-aminobenzylstatine derivative SDZ PRI 053, which contains 2-(S)-amino-3-(R)-hydroxyindane in place of an amino acid amide, is a potent and orally bioavailable inhibitor of HIV-1 replication. The antiviral activity of SDZ PRI 053 was demonstrated in various cell lines, in primary lymphocytes, and in primary monocytes, against laboratory strains as well as clinical HIV-1 isolates (50% effective dose = 0.028 to 0.15 microM). Cell proliferation was impaired only at 100- to 300-fold-higher concentrations. The mechanism of antiviral action of the proteinase inhibitor SDZ PRI 0.53 was demonstrated to be inhibition of gag precursor protein processing. The finding that the inhibitory potency of SDZ PRI 053 in chronic virus infection, determined by p24 release, was considerably lower than that in de novo infection may be explained by the fact that the virus particles produced in the presence of SDZ PRI 053 are about 50-fold less infectious than those from untreated cultures. Upon intravenous administration, half-lives in blood of 100 and 32 min in mice and rats, respectively, were measured. Oral bioavailability of SDZ PRI 053 in rodents was 20 to 60%, depending on the dose. In mice, rats, and dogs, the inhibitor levels after oral administration remained far above the concentrations needed to efficiently block HIV replication in vitro for a prolonged period. This compound is thus a promising candidate for clinical use in HIV disease.
RP 59500 prophylaxis of experimental endocarditis due to erythromycin-susceptible and -resistant isogenic pairs of viridans group streptococci
Authors: L'Hériteau F , Entenza J M , Lacassin F , Leport C , Glauser M P , Moreillon P
Published: June 2012

RP 59500 is a new injectable streptogramin composed of two synergistic components (quinupristin and dalfopristin) which are active against a number of erythromycin-susceptible and -resistant gram-positive bacteria. The following experiments investigate the ability of RP 59500 to prevent experimental endocarditis due to either of two erythromycin-susceptible streptococcal isolates or their constitutively erythromycin-resistant Tn916 delta E transconjugants. RP 59500 had low MICs (0.125 to 0.5 mg/liter) for all four test organisms and was substantially bactericidal in vitro. Rats with catheter-induced aortic vegetations were given single-dose antibiotic prophylaxis 30 to 60 min before bacterial inoculation through a computerized pump system which permitted the simulation of drug kinetics for humans produced by either 7 mg of RP 59500 per kg of body weight or 1 g of vancomycin. Single-dose RP 59500 prophylaxis successfully prevented endocarditis due to both the erythromycin-susceptible parent strains and their erythromycin-resistant derivatives in rats challenged with the minimal inoculum infecting 90% of controls. In addition, RP 59500 also prevented infection in animals challenged with fivefold-larger inocula of the erythromycin-susceptible parent strains. Vancomycin successfully prevented endocarditis due to any of the four test organisms. These results underline the in vivo efficacy of RP 59500 against both erythromycin-susceptible and -resistant streptococci. Such good results against the resistant strains would not be expected with erythromycin or clindamycin, which are the standard macrolidelincosamide-streptogramin antibiotics used for endocarditis prophylaxis in humans. An oral form of RP 59500 which might advantageously replace some of the older prophylactic regimens is currently being developed.
Contribution of the C-8 substituent of DU-6859a, a new potent fluoroquinolone, to its activity against DNA gyrase mutants of Pseudomonas aeruginosa
Authors: Kitamura A , Hoshino K , Kimura Y , Hayakawa I , Sato K
Published: June 2012

Inhibitory effects of five quinolones against DNA gyrases purified from four quinolone-resistant clinical isolates of Pseudomonas aeruginosa and the quinolone-susceptible strain PAO1 were examined. All of the quinolone-resistant strains tested were found to be DNA gyrase mutants. The 50% inhibitory concentrations (IC50s) of the quinolones for these DNA gyrases roughly correlated with their MICs. Interestingly, gyrase inhibition by DU-6859a was found to be significantly less affected by these mutations that inhibition by other currently available quinolones. To assess the enhanced activity shown by DU-6859a, the effects of quinolones with altered substituents at the N-1, C-7, and C-8 positions of the quinolone ring of DU-6859a were tested. Measurement of MICs for four DNA gyrase mutants and IC50s for their purified DNA gyrases showed that removal of the C-8 chlorine of DU-6859a significantly increased MICs and IC50s for DNA gyrase mutants. However, no deleterious effects were observed when either the fluorine on the cyclopropyl substituent at the N-1 position or the cyclopropyl ring at the C-7 substituent was removed. Moreover, removal of the C-8 chlorine also increased the MIC for 19 of 20 quinolone-resistant clinical isolates. Our results led to the conclusion that DU-6859a is much more active against quinolone-resistant clinical isolates of P. aeruginosa than other currently available quinolones, probably because of its strong inhibitory effects against mutant quinolone-resistant DNA gyrases, and that the C-8 chlorine is necessary for these potent effects.
Evaluation of retinal toxicity and efficacy of the anticytomegalovirus compound 2-amino-7-[(1,3-dihydroxy-2-propoxy)methyl]purine
Authors: Besen G , Chavez-de la Paz E , Tatebayashi M , Flores-Aguilar M , Gangan P A , Munguia D , Wiley C A , Jähne G , Winkler I , Helsberg M
Published: June 2012

Compound 2242, also known as 2-amino-7-[(1,3-dihydroxy-2-propoxy)methyl]purine, is the first known antivirally active nucleoside analog with the side chain substituted at the N-7 position of the purine ring system. Our purpose was to evaluate its retinal toxicity and assess the efficacy of its highest nontoxic concentration in a rabbit model of herpes simplex retinitis. Concentrations of the drug from 0.5 to 2,000 microM were injected intravitreally in twelve New Zealand White rabbits. Fundoscopic, histologic, and electrophysiologic data revealed no evidence of toxicity even at the highest dose of the compound. Dutch pigmented rabbits (n = 34) had their left eyes injected with herpes simplex virus type 1 3 days after, concurrently, or 3 days before intravitreal injection of either 2,000 microM compound 2242 or 480 microM ganciclovir (final concentration in the eye). Both compound 2242 and ganciclovir were equally effective compared with saline when administered simultaneously with the virus (P < 0.0001). In the 3-day pretreatment paradigm, compound 2242 was superior to ganciclovir (P < 0.04), but there was no clear difference between the two with regard to their effects on an established infection. The pharmacokinetics of compound 2242 in 10 rabbits injected intravitreally with 30 microM showed an intravitreal half-life of 8 h. This compound, which may be orally active in its pro form, has a very high therapeutic index in the eye and is more efficient than ganciclovir in this animal model of herpes retinitis.
Mechanism of action of antimycobacterial activity of the new benzoxazinorifamycin KRM-1648
Authors: Fujii K , Saito H , Tomioka H , Mae T , Hosoe K
Published: June 2012

The mechanism of antimicrobial activity of KRM-1648 (KRM), a new rifamycin derivative with potent antimycobacterial activity, was studied. Both KRM and rifampin (RMP) inhibited RNA polymerases from Escherichia coli and Mycobacterium avium at low concentrations: the 50% inhibitory concentrations (IC50s) of KRM and RMP for E. coli RNA polymerase were 0.13 and 0.10 micrograms/ml, respectively, while the IC50s for M. avium RNA polymerase were 0.20 and 0.07 microgram/ml. Both KRM and RMP exerted weak inhibitory activity against Mycobacterium fortuitum RNA polymerase, rabbit thymus RNA polymerases, E. coli DNA polymerase I, and two types of reverse transcriptases. Uptake of 14C-KRM by M. avium reached 18,000 dpm/mg (dry weight) 1.5 h after incubation, while uptake by E. coli cells was slight. KRM was much more effective in inhibiting uptake of 14C-uracil than was RMP (IC50 of KRM, 0.04 microgram/ml; IC50 of RMP, 0.12 microgram/ml). These findings suggest, first, that the potent antimycobacterial activity of KRM is due to inhibition of bacterial RNA polymerase and, second, that the activity of KRM against target organisms depends on target cell wall permeability.
Pharmacodynamics of RP 59500 alone and in combination with vancomycin against Staphylococcus aureus in an in vitro-infected fibrin clot model
Authors: Kang S L , Rybak M J
Published: June 2012

The bactericidal activity and emergence of resistance to RP 59500 (quinupristin/dalfopristin) when it was administered alone and in combination with vancomycin against fibrin clots that have been infected with methicillin-susceptible Staphylococcus aureus ATCC 25923 or methicillin-resistant S. aureus (MRSA) 67 were evaluated in an in vitro pharmacodynamic infected fibrin clot model. Fibrin clots were infected with S. aureus to achieve an inoculum of approximately 10(9) CFU/g. Antibiotics were administered to simulate pharmacokinetics in humans: RP 59500 (7.5 mg/kg of body weight) every 8 h and vancomycin (15 mg/kg) every 12 h over 72 h. Preliminary test tube time-kill experiments with an inoculum of approximately 10(5) CFU/ml suggested that RP 59500 was more rapid in achieving a 99.9% reduction in the number of CFU per milliliter than vancomycin against ATCC 25923 (6.94 versus 24 h; P = 0.0003) and MRSA 67 (6.77 versus 17.03 h; P = 0.004). At a higher inoculum (approximately 10(8) CFU/ml), 99.9% kill was achieved only with the combination regimen against ATCC 25923 and MRSA 67 (10.9 and 10.5 h, respectively), with total reductions of 6.35 and 6.33 log10 CFU/ml over 24 h, respectively. In the fibrin clot model, RP 59500 was more effective than vancomycin in reducing organism titers over 72 h. In the fibrin clot model, the most optimal therapy was the combination regimen.
Inhibition of sterol 4-demethylation in Candida albicans by 6-amino-2-n-pentylthiobenzothiazole, a novel mechanism of action for an antifungal agent
Authors: Kuchta T , Léka C , Farkas P , Bujdáková H , Belajová E , Russell N J
Published: June 2012

The effects of 6-amino-2-n-pentylthiobenzothiazole (APB), a new antifungal agent, on ergosterol biosynthesis in Candida albicans and Saccharomyces cerevisiae were studied, using [14C]acetate incorporation. In C. albicans, the inhibition of growth was accompanied by a marked inhibition of acetate incorporation in 4-desmethylsterols, with a significant portion of the radiolabel being incorporated in 4,4-dimethylsterols, lanosterol, and 4,4-dimethylzymosterol and minor amounts being incorporated in 4-methylsterols and squalene. The data are interpreted as evidence of a block of the ergosterol biosynthesis pathway at the level of 4-demethylation of 4,4-dimethylzymosterol, with partial inhibition of lanosterol 14-dimethylation and squalene epoxidation also being possible. In 6-amino-2-n-pentylthiobenzothiazole-treated S. cerevisiae, a significant amount of the radiolabel was incorporated also in 4-methylsterols, 4-methylzymosterol, and 4-methylfecosterol, indicating that in this microorganism there are different sensitivities of the two 4-demethylations and that the pathway is blocked at the level of 4-demethylation of 4-methylsterols.
In vitro and in vivo effects of penicillin and clindamycin on expression of group A beta-hemolytic streptococcal capsule
Authors: Brook I , Gober A E , Leyva F
Published: June 2012

Encapsulation of group A beta-hemolytic streptococci (GABHS) is an important virulence factor. The changes that occur in the frequency of encapsulation of GABHS during pharyngotonsillitis, in 20 patients treated with penicillin and 20 treated with clindamycin, were investigated. The effects of subinhibitory concentrations of these agents were also evaluated in vitro. At day 4, 8 of 10 (80%) GABHS isolates recovered from children treated with penicillin were encapsulated, compared with 1 of 5 (20%) of those from children treated with clindamycin (P < 0.05). Two days following 10 days of therapy, GABHS was eliminated from 13 of the 20 (65%) children treated with penicillin and from all treated with clindamycin (P < 0.05). At that time, six of the seven GABHS isolates recovered in patients treated with penicillin were encapsulated. GABHS were not detected after 4 days of therapy in those treated with clindamycin. Incubation of GABHS isolates with one-half of the MIC of clindamycin reduced the frequency of encapsulation, compared with that after incubation with one-half of the MIC of penicillin (12.5 versus 67.5%). These data illustrate the superiority of clindamycin over penicillin in reducing the expression of a capsule by GABHS.
Product of fosC, a gene from Pseudomonas syringae, mediates fosfomycin resistance by using ATP as cosubstrate
Authors: García P , Arca P , Evaristo Suárez J
Published: June 2012

Pseudomonas syringe PB-5123, a producer of fosfomycin, is resistant to high concentrations of the antibiotic. Two possible mechanisms of resistance have been detected: (i) impermeability to exogenous fosfomycin, even in the presence of sugar phosphate uptake inducers, and (ii) antibiotic phosphorylation. The gene responsible for this last activity, fosC, encodes a ca. 19,000-Da protein and is immediately followed by a second open reading frame, which shows sequence similarities to glutathione S-transferases. FosC uses ATP as a cosubstrate in an inactivation reaction that can be reversed with alkaline phosphatase. Other nucleotide triphosphates cannot be substituted for ATP in this reaction. No relationship between fosC and the previously described genes of fosfomycin resistance was found.
Antimicrobial activity of MDL 63,246, a new semisynthetic glycopeptide antibiotic
Authors: Goldstein B P , Candiani G , Arain T M , Romanò G , Ciciliato I , Berti M , Abbondi M , Scotti R , Mainini M , Ripamonti F
Published: June 2012

MDL 63,246 is a semisynthetic derivative of the naturally occurring glycopeptide antibiotic MDL 62,476 (A40926). It was more active in vitro against Staphylococcus aureus and coagulase-negative staphylococci than MDL 62,476, teicoplanin, and vancomycin and was more active than mideplanin (MDL 62,873) against some isolates. MDL 63,246 had excellent activity against streptococci and teicoplanin-susceptible enterococci, and it also had in vitro activity against some VanA enterococcal isolates. It was more active than teicoplanin and vancomycin against acute staphylococcal, streptococcal, and enterococcal septicemia in immunocompetent and neutropenic mice. It was highly efficacious in reducing the bacterial load in the hearts of rats in staphylococcal endocarditis experiments and the bacterial load of Staphylococcus epidermis in a high infection model in neutropenic mice. The excellent in vivo activity of MDL 63,246 appears to correlate both with its in vitro antibacterial activity and with its long half-life in rodents.
Activities of three investigational fluoroquinolones (BAY y 3118, DU-6859a, and clinafloxacin) against Neisseria gonorrhoeae isolates with diminished susceptibilities to ciprofloxacin and ofloxacin
Authors: Carlyn C J , Doyle L J , Knapp C C , Ludwig M D , Washington J A
Published: June 2012

Between 1 January 1992 and 31 December 1993, our laboratory, as part of the Gonococcal Isolate Surveillance Project, found that 39 of 673 isolates of Neisseria gonorrhoeae from one local sexually transmitted diseases clinic demonstrated decreased susceptibilities to both ciprofloxacin and ofloxacin. The MICs of BAY y 3118, DU-6859a, and clinafloxacin at which 90% of the gonococci with decreased susceptibility to ciprofloxacin and ofloxacin were inhibited were all 0.016 microgram/ml, which was eightfold higher than those for ciprofloxacin-susceptible gonococci. Our report substantiates prior observations that diminished susceptibility to one quinolone is often associated with diminished susceptibility to other quinolones.
Comparison of sparfloxacin, temafloxacin, and ciprofloxacin for prophylaxis and treatment of experimental foreign-body infection by methicillin-resistant Staphylococcus aureus
Authors: Cagni A , Chuard C , Vaudaux P E , Schrenzel J , Lew D P
Published: June 2012

The prophylactic and therapeutic activities of three broad-spectrum fluoroquinolones were evaluated in two different experimental models of foreign-body infections caused by methicillin-resistant Staphylococcus aureus (MRSA) susceptible to quinolones. In a guinea pig model of prophylaxis, subcutaneously implanted tissue cages were infected at a > 90% rate by 10(2) CFU of MRSA in control animals. A single dose of 50 mg of ciprofloxacin per kg of body weight administered intraperitoneally 3 h before bacterial challenge was less effective than an equivalent regimen of either sparfloxacin or temafloxacin in decreasing the rate of experimental infection in tissue cages challenged with increasing inocula of MRSA. In a rat model evaluating the therapy of chronic tissue cage infection caused by MRSA, the efficacy of a 7-day high-dose (50-mg/kg twice-daily) regimen of sparfloxacin, temafloxacin, or ciprofloxacin was compared to that of vancomycin (50 mg/kg twice daily). Active levels of sparfloxacin, temfloxacin, or ciprofloxacin were continuously present in tissue cage fluid during therapy, exceeding their MBCs for MRSA by 6- to 20-fold. Either temafloxacin, sparfloxacin, or vancomycin was significantly (P < 0.01) more active than ciprofloxacin in decreasing the viable counts of MRSA in tissue cage fluids. The different activities of ciprofloxacin compared with those of the other two quinolones against chronic tissue cage infections caused by MRSA did not involve the selective emergence of quinolone-resistant mutants. Temafloxacin and ciprofloxacin, which showed the most prominent differences in their in vivo activities, however, exhibited similar bactericidal properties and pharmacokinetic parameters in the rat model. In conclusion, both temafloxacin and sparfloxacin were significantly more active than ciprofloxacin for the prophylaxis or treatment of experimental foreign-body infections caused by a quinolone-susceptible strain of MRSA.
New system based on site-directed mutagenesis for highly accurate comparison of resistance levels conferred by SHV beta-lactamases
Authors: Nüesch-Inderbinen M T , Hächler H , Kayser F H
Published: June 2012

We developed a system based on site-directed mutagenesis that allows a precise comparison of SHV enzymes under isogenic conditions. In addition, the influences of two different, naturally occurring promoters were examined for each SHV derivative. The system comprised two separately cloned DNA fragments, each the size of 3.6 kb. Both fragments encoded an SHV gene originating from clinical isolates but with different promoters. The structural genes were made identical by site-directed mutagenesis. Other mutations were then introduced into both fragments by means of site-directed mutagenesis, resulting in the SHV derivatives SHV-1, SHV-2, SHV-2a, SHV-3, and SHV-5. The amino acid exchange of glutamic acid at position 235 for lysine in SHV-5 resulted in the highest resistance levels. SHV-3, differing from SHV-2 by the exchange of arginine at position 201 for leucine and previously described as indistinguishable from SHV-2, was shown to cause slightly higher resistance to ceftazidime and lower resistance to ceftriaxone, cefotaxime, and cefepime than SHV-2. The point mutation in SHV-2a, with the leucine-to-glutamine replacement at the unusual position 31, previously considered almost insignificant, proved to increase resistance to ceftazidime but reduced the MICs of all other cephalosporins tested when compared with those for SHV-2. For all clones harboring SHV derivatives, resistance was increased by a stronger promoter, in some cases masking the effect of the point mutation itself and demonstrating the importance of regulatory mechanisms of resistance.
Purification of a 54-kilodalton protein (OprJ) produced in NfxB mutants of Pseudomonas aeruginosa and production of a monoclonal antibody specific to OprJ
Authors: Hosaka M , Gotoh N , Nishino T
Published: June 2012

The 54-kDa outer membrane protein (designated OprJ) of a norfloxacin-resistant nfxB mutant of Pseudomonas aeruginosa PAO1 was purified by ion-exchange high-performance liquid chromatography. Mobility of OprJ in sodium dodecyl sulfate-polyacrylamide gel electrophoresis was not affected by reduction and heating. A murine monoclonal antibody (MAb) against OprJ was prepared to investigate existence of this protein in fluoroquinolone-susceptible and -resistant strains of P. aeruginosa. Western blot (immunoblot) analysis with this MAb revealed a single band at the position corresponding to OprJ in outer membrane proteins of NfxB mutants derived from clinical isolates. However, the MAb did not react with any outer membrane proteins of the respective parent strains. Complementation of the NfxB mutation by transformation with plasmid pNF111, which contained the wild-type nfxB gene, led to disappearance of the single band corresponding to OprJ. The existence of OprJ was associated with fluoroquinolone resistance. Furthermore, the MAb did not react with any outer membrane proteins of other fluoroquinolone-resistant nalB and nfxC mutants. These results suggest that OprJ is newly produced in NfxB mutants of P. aeruginosa and is involved in fluoroquinolone resistance specific to NfxB, and it appears that the MAb to OprJ should aid in detection of the NfxB mutation in P. aeruginosa.
In vivo activity and pharmacodynamics of cefotaxime or ceftriaxone in combination with fosfomycin in fibrin clots infected with highly penicillin-resistant Streptococcus pneumoniae
Authors: Chavanet P , Beloeil H , Pechinot A , Duigou F , Buisson J C , Duong M , Neuwirth C , Kazmierczak A , Portier H
Published: June 2012

Using a clinical pneumococcal strain for which MICs were 2, 0.5, 0.5, and 16 mg/liter for penicillin, cefotaxime, ceftriaxone, and fosfomycin, respectively, we studied the efficacies of these antibiotics alone and in combination in one or two doses or in continuous infusion over 6 h in the treatment of the prolonged (48-h) experimental fibrin clot infections in rabbits. Doses were chosen to obtain low antibiotic concentrations. We observed the highest bacterial reductions (change in log10 CFU per gram) with the following five regimens: combination of cefotaxime plus fosfomycin given in two divided doses 6 h apart (each at 50 mg/kg of body weight given intravenously (4.2 +/- 0.7 CFU/g), ceftriaxone (8 mg/kg given once intravenously) along with one or two doses of fosfomycin (3.79 +/- 0.6 and 3.95 +/- 0.5 CFU/g), cefotaxime alone administered in two divided doses (3.6 +/- 0.4 CFU/g), and a 6-h continuous infusion of cefotaxime (100 mg/kg) with fosfomycin (100 mg/kg) (3.5 +/- 0.4 CFU/g). The bacterial reductions obtained with these five regimens were all higher than those obtained with the other regimens tested (P < 0.05). The time of bacterial regrowth was significantly delayed with the two doses of the cefotaxime-fosfomycin regimens (23.2 +/- 11 h) compared with those with the other combinations (P < 0.05). The rate of bacterial regrowth with this regimen was even lower than that observed with cefotaxime alone given in two doses (P < 0.05). By a multivariate analysis, the most important independent parameters for efficacy were the maximal concentrations of beta-lactam antibiotics and the residual concentration of fosfomycin and, for the combinations, the log of the area under the concentration-time curve/MIC ratio for beta-lactam antibiotics. From these findings, the combinations cefotaxime or ceftriaxone plus fosfomycin could be proposed for the treatment of infections caused by highly penicillin-resistant pneumococci.
Effect of xylitol on growth of nasopharyngeal bacteria in vitro
Authors: Kontiokari T , Uhari M , Koskela M
Published: June 2012

Xylitol is known to reduce caries by inhibiting the growth of Streptococcus mutans. We hypothesized that xylitol could also affect the growth of other nasopharyngeal bacterial flora, which could be important when considering respiratory infections caused by these bacteria. We studied this in vitro by adding xylitol to the medium and observed that 1 and 5% xylitol reduced markedly the growth of alpha-hemolytic streptococci, including S. pneumoniae. It reduced slightly the growth of beta-hemolytic streptococci but not that of Haemophilus influenzae or Moraxella catarrhalis. The inhibitory growth pattern was similar to that previously seen with S. mutans, which may indicate a similarity in the enzymatic processing of five-carbon sugars such as xylitol. This sugar alcohol is a widely used sweetener, and the concentrations used in our experiments are easily achieved in the oral cavity. If xylitol reduces the growth of S. pneumoniae in the nasopharynx, it could also reduce the carriage of this pathogen and thus have clinical significance in the prevention of pneumococcal diseases.
Pharmacokinetics and bioavailability of fluconazole in two groups of males with human immunodeficiency virus (HIV) infection compared with those in a group of males without HIV infection
Authors: Tett S , Moore S , Ray J
Published: June 2012

Fluconazole pharmacokinetics, including absolute bioavailability, were determined for one group of controls (n = 10) and two groups of people with human immunodeficiency virus (HIV) infection (those with CD4+ T-cell counts of less than [n = 4] or greater than [n = 9] 200 cells per mm3). Twenty subjects received four doses of fluconazole; three doses were oral (50, 100, and 400 mg), and one dose was intravenous (either 50, 100, or 400 mg). The other three subjects received one or two doses. The groups were comparable in terms of the weight, body mass index, and estimated creatinine clearance of the subjects, but the people with HIV infection were older. Pharmacokinetic parameters indicated linearity in all subjects; the area under the plasma concentration-time curve and the maximum concentration increased in proportion to the dose. The fraction of an oral dose of fluconazole absorbed approximated unity in all three groups of subjects. The mean (+/- standard deviation) plasma clearance of fluconazole was lowest in the group of subjects with low CD4+ T-cell counts; the value for this group was 0.74 +/- 0.19 liter/h, compared with 0.97 +/- 0.19 liter/h in the group with HIV infection and CD4+ T-cell counts of greater than 200 cells/mm3 and 1.18 +/- 0.23 liter/h in the group of control subjects (P < 0.05). The volume of distribution was lower in those with HIV infection (P = 0.04, corrected for weight). The half-life was longest in people with HIV infection and low CD4+ T-cell counts (P = 0.01). This study has shown that some differences do exist between the pharmacokinetics of fluconazole in people with HIV infection and those in noninfected controls.
Susceptibilities of Neisseria gonorrhoeae to the glycylcyclines
Authors: Whittington W L , Roberts M C , Hale J , Holmes K K
Published: June 2012

To assess the activities of two glycylcyclines, N,N-dimethylglycylamido (DMG) derivatives of minocycline (MINO) and 6-demethyl-6-deoxytetracycline (DMDOT), 203 gonococcal isolates recovered at six sexually transmitted disease clinics in the western United States were evaluated. Antimicrobial susceptibilities to tetracycline HCl, doxycycline, MINO, DMG-DMDOT, and DMG-MINO were determined by agar dilution tests. DMG-DMDOT and DMG-MINO were more active than tetracycline HCl, doxycycline, or MINO regardless of the presence of Tet M or of chromosomal mutations mediating tetracycline resistance (P < 0.001).
K65R mutation of human immunodeficiency virus type 1 reverse transcriptase encodes cross-resistance to 9-(2-phosphonylmethoxyethyl)adenine
Authors: Gu Z , Salomon H , Cherrington J M , Mulato A S , Chen M S , Yarchoan R , Foli A , Sogocio K M , Wainberg M A
Published: June 2012

Cloned variants of human immunodeficiency virus type 1 that contain the K65R mutation in reverse transcriptase have previously been shown to display approximately 10- to 30-fold resistance against 2',3'-dideoxycytidine, 2',3'-dideoxyinosine, and 2',3'-dideoxy-3'-thiacytidine. On the basis of tissue culture studies with both primary T cells and established cell lines, we now report that the K65R mutation confers approximately 12- to 15-fold resistance to 9-(2-phosphonylmethoxyethyl)adenine (PMEA). Likewise, a chain termination system revealed that mutated recombinant K65R reverse transcriptase displays resistance to PMEA diphosphate, the active metabolite of PMEA, in cell-free enzyme assays. Parallel studies have shown that the M184V mutation in reverse transcriptase, associated with high-level resistance against the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine, does not confer resistance to PMEA in tissue culture. Viruses and enzymes that included both the K65R and M184V mutations were resistant to PMEA and PMEa diphosphate, respectively, but only to the extent conferred by the K65R mutation alone.
In vivo efficacy of azithromycin in treatment of systemic infection and septic arthritis induced by type IV group B Streptococcus strains in mice: comparative study with erythromycin and penicillin G
Authors: Tissi L , von Hunolstein C , Mosci P , Campanelli C , Bistoni F , Orefici G
Published: June 2012

We compared the activities of azithromycin, erythromycin, and penicillin G in a mouse model of systemic infection and septic arthritis induced by type IV group B streptococci (GBS). The in vitro and in vivo efficacy data for these drugs were analyzed relative to the pharmacokinetics of the drugs in sera, joints, and kidneys. Adult CD-1 mice were infected intravenously with 10(7) CFU of type IV GBS. Intraperitoneal drug administration was initiated with different dose regimens at different times after infection. A single dose of azithromycin (100 mg/kg) strongly reduced the incidence of articular lesions with respect to that with erythromycin or penicillin G. Treatment with azithromycin (three intraperitoneal administrations of 50 mg/kg at 12-h intervals) resulted in the complete prevention of arthritis. In contrast, erythromycin was poorly effective and penicillin G was effective only if inoculated 30 min after infection and at high doses (400,000 or 600,000 IU/kg). Furthermore, azithromycin was able to cure about 70% of the mice when administered 7, 8, and 9 days after GBS infection. Azithromycin was much more active than erythromycin and penicillin G with respect to bacterial killing in the joints and kidneys. In fact, cultures from these tissues were always negative no matter what treatment schedule was employed. The pharmacokinetics of azithromycin account for its superior in vivo efficacy against type IV GBS. A longer half-life and higher levels of this drug in serum and tissues with respect to those for erythromycin or penicillin G were achieved. The high affinity of azithromycin for the joints strongly supports its potential value for therapy of septic arthritis, which is a severe and frequent clinical manifestation of GBS infection.
Evidence for an efflux pump in multidrug-resistant Campylobacter jejuni
Authors: Charvalos E , Tselentis Y , Hamzehpour M M , Köhler T , Pechere J C
Published: June 2012

Mechanisms of drug resistance in Campylobacter jejuni were investigated. Mutant strains 34PEFr, which was resistant to pefloxacin (128-fold increase in the MIC), and 34CTXr, which was resistant to cefotaxime (32-fold increase in the MIC) and which was derived from the susceptible parent 34s, were obtained by serial passages on pefloxacin and cefotaxime gradient plates, respectively. Both mutants showed cross-resistance to erythromycin, chloramphenicol, tetracycline, beta-lactams, and quinolones. While the quinolone resistance of strain PEFr could be explained by a mutation at codon 86 of the gyrA gene, the multidrug resistance phenotype of both strains was further investigated. Accumulation of pefloxacin, ciprofloxacin, and minocycline was measured by fluorometry and was found to be lower in the mutant strains than in the parent strain. Preincubation of the cells with carbonyl cyanide m-chlorophenylhydrazone, however, completely abolished this difference. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of outer membrane preparations from both mutant strains showed overexpression of two proteins of 55 and 39 kDa which were absent from the outer membranes of the wild-type strain. These results indicate that in C. jejuni 34PEFr and 34CTXr, multidrug resistance is associated with an efflux system with a broad specificity.
Doxycycline-rifampin versus doxycycline-streptomycin in treatment of human brucellosis due to Brucella melitensis. The GECMEI Group. Grupo de Estudio de Castilla-la Mancha de Enfermedades Infecciosas
Authors: Solera J , Rodríguez-Zapata M , Geijo P , Largo J , Paulino J , Sáez L , Martínez-Alfaro E , Sánchez L , Sepulveda M A , Ruiz-Ribó M D
Published: June 2012

Brucellosis is a common zoonosis in many parts of the world; the best regimen for the treatment of brucellosis has not been clearly determined. We have carried out a multicenter, open, controlled trial in five general hospitals in Spain to compare the efficacy and safety of doxycycline and rifampin (DR) versus doxycycline and streptomycin (DS) for the treatment of human brucellosis. The study included 194 ambulatory or hospitalized patients with acute brucellosis, without endocarditis or neurobrucellosis. The diagnostic criterion was isolation of Brucella species from blood or other tissues (n = 120) or a standard tube agglutination titer of 1/160 or more for anti-Brucella antibodies with compatible clinical findings (n = 74). Patients were randomly assigned to receive either 100 mg of doxycycline twice daily plus rifampin, 900 mg/day, in a single morning dose for 45 days (DR group) or the same dose of doxycycline for 45 days plus streptomycin, 1 g/day, intramuscularly for 14 days (DS group). A lack of therapeutic efficacy developed in 8 of the 100 patients in the DR group (8%) and in 2 of the 94 patients in the DS group (2%)(P = 0.10). Relapses occurred in 16 of the 100 patients in the DR group (16%) but in only 5 of the 94 patients in the DS group (5.3%) (P = 0.02). When relapse was considered in combination with initial lack of efficacy, 26 patients in the DR group (24%) and 7 patients in the DS group (7.45%) failed to respond to therapy (P = 0.0016). In general, therapy was well tolerated and only four patients (4%) in the DR group and two (2%) in the DS group had episodes of adverse effects necessitating discontinuation of treatment (P> 0.2). We conclude that a doxycycline-and-rifampin regimen is less effective than the doxycycline-and-streptomycin regimen in patients with acute brucellosis.
Identification of daptomycin-binding proteins in the membrane of Enterococcus hirae
Authors: Boaretti M , Canepari P
Published: June 2012

Daptomycin, a lipopeptide antibiotic active against gram-positive bacteria, was preliminarily shown to inhibit lipoteichoic acid (LTA) synthesis as a consequence of membrane binding in the presence of Ca2+ (P. Canepari, M. Boaretti, M. M. Lleó, and G. Satta, Antimicrob. Agents Chemother. 34:1220-1226, 1990). In the present study, it is shown that, along with binding bacterial-membrane components, daptomycin binds the protein fraction with a noncovalent bond, as suggested by the instability of the bond in the presence of ionic detergents such as sodium dodecyl sulfate. Analysis of membrane proteins by isoelectric focusing electrophoresis reveals that five bands with isoelectric points ranging from 5.9 to 6.2 bind radioactive daptomycin. These proteins are therefore called daptomycin-binding proteins. In an attempt to correlate these proteins to the main inhibition observed during LTA synthesis, two-dimensional thin-layer chromatography of lipids synthesized during daptomycin treatment was performed. A threefold increase in diglucosyl diacylglycerol is demonstrated, while the compounds phosphatidyl-alpha-kojibiosyldiacylglycerol, glycerophospho-phosphatidyl-alpha-kojibiosyldiacylglycerol, and glycerophospho-kojibiosyldiacylglycerol, which follow diglucosyl diacylglycerol in LTA synthesis, decrease progressively with time during the course of daptomycin treatment.
Comparison of activities of rifapentine and rifampin against Mycobacterium tuberculosis residing in human macrophages
Authors: Mor N , Simon B , Mezo N , Heifets L
Published: June 2012

The activities of rifapentine and rifampin against Mycobacterium tuberculosis residing in human monocyte-derived macrophages were determined. The MICs and MBCs of rifapentine for intracellular bacteria were two- to fourfold lower than those of rifampin. For extracellular bacteria, this difference was less noticeable. Nevertheless, the more favorable pharmacokinetics of rifapentine over rifampin was addressed in other experimental models. These models showed substantial differences after short pulsed exposures of the infected macrophages to the drugs and when the infected macrophages were exposed to changing drug concentrations that imitated the pharmacokinetic curves observed in blood. Once-a-week exposures to rifapentine concentrations equivalent to those attained in blood after one 600-mg dose resulted during the first week in a dramatic decline in the number of bacteria, and this decline was maintained at a minimal level for a period of four weeks. The results of this study have shown the suitability of rifapentine for intermittent-treatment regimens. The prolonged effect of rifapentine found in this study may be associated with high ratios of intracellular accumulation, which were four- to fivefold higher than those found for rifampin. Further studies on the intracellular distribution of rifamycins and on the sites of actual interaction between the drugs and bacteria residing in macrophages are necessary.
Sequences of conserved region in the A subunit of DNA gyrase from nine species of the genus Mycobacterium: phylogenetic analysis and implication for intrinsic susceptibility to quinolones
Authors: Guillemin I , Cambau E , Jarlier V
Published: June 2012

The sequences of a conserved region in the A subunit of DNA gyrase corresponding to the quinolone resistance-determining region were determined for nine mycobacterial species and were compared. Although the nucleotide sequences were highly conserved, they clearly differentiated one species from another. The results of the phylogenetic analysis based on the sequences of the quinolone resistance-determining regions were compared with those provided by the 16S rRNA sequences. Deduced amino acid sequences were identical within the nine species except for amino acid 83, which was frequently involved in acquired resistance to quinolones in many genera, including mycobacteria. The presence at position 83 of an alanine for seven mycobacterial species (M. tuberculosis, M. bovis BCG, M. leprae, M. avium, M. kansasii, M. chelonae, and M. smegmatis) and of a serine for the two remaining mycobacterial species (M. fortuitum and M. aurum) correlated well with the MICs of ofloxacin for both groups of species, suggesting the role of this residue in intrinsic susceptibility to quinolones in mycobacteria.
Effect of cefotaxime or ceftriaxone treatment on nasopharyngeal Haemophilus influenzae type b colonization in children
Authors: Goldwater P N
Published: June 2012

The effects of cefotaxime and ceftriaxone treatment on nasopharyngeal carriage of Haemophilus influenzae type b (Hib) were prospectively studied with 53 children with invasive Hib disease. Nasopharyngeal aspirates were monitored during therapy. Hib was eliminated within 2 days in 92% of patients and was eliminated in all patients after the third day of antibiotic treatment.
Absorption of ciprofloxacin in patients with diabetic gastroparesis
Authors: Marangos M N , Skoutelis A T , Nightingale C H , Zhu Z , Psyrogiannis A G , Nicolau D P , Bassaris H P , Quintiliani R
Published: June 2012

The purpose of this study was to assess the pharmacokinetic profile of ciprofloxacin in 12 patients with diabetic gastroparesis. Patients received both a single 500-mg oral (p.o.) dose and a single 400-mg intravenous (i.v.) dose of ciprofloxacin separated by a 1-week washout period. Pharmacokinetic parameters (means +/- standard deviations) for the p.o. and i.v. doses were as follows: areas under the concentration-time curve from 0 h to infinity, 9.74 +/- 2.59 and 11.78 +/- 3.18 micrograms.h/ml, respectively; maximum concentrations of drug in serum, 2.13 +/- 0.67 and 4.21 +/- 1.07 micrograms/ml, respectively; and half-lives, 4.03 +/- 0.58 and 4.20 +/- 0.58 h, respectively. The ratio of the areas under the concentration-time curves from 0 h to infinity for the p.o. and i.v. doses was 0.84, with a 90% confidence interval of 0.68 to 0.98; the mean absolute bioavailability was calculated to be 67% (range, 43 to 82%). From these data it appears that ciprofloxacin is adequately absorbed in patients with diabetic gastroparesis.
CD8+T Cells Use TRAIL To Restrict West Nile Virus Pathogenesis by Controlling Infection in Neurons
Authors: Shrestha Bimmi , Pinto Amelia K. , Green Sharone , Bosch Irene , Diamond Michael S.
Published: June 2012

Previous studies of mice have demonstrated that an orchestrated sequence of innate and adaptive immune responses is required to control West Nile virus (WNV) infection in peripheral and central nervous system (CNS) tissues. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; also known as CD253) has been reported to inhibit infection with dengue virus, a closely related flavivirus, in cell culture. To determine the physiological function of TRAIL in the context of flavivirus infection, we compared the pathogenesis of WNV in wild-type andTRAIL−/−mice. Mice lacking TRAIL showed increased vulnerability and death after subcutaneous WNV infection. Although no difference in viral burden was detected in peripheral tissues, greater viral infection was detected in the brain and spinal cord at late times after infection, and this was associated with delayed viral clearance in the few survivingTRAIL−/−mice. While priming of adaptive B and T cell responses and trafficking of immune and antigen-specific cells to the brain were undistinguishable from those in normal mice, inTRAIL−/−mice, CD8+T cells showed qualitative defects in the ability to clear WNV infection. Adoptive transfer of WNV-primed wild-type but notTRAIL−/−CD8+T cells to recipient CD8−/−mice efficiently limited infection in the brain and spinal cord, and analogous results were obtained when wild-type orTRAIL−/−CD8+T cells were added to WNV-infected primary cortical neuron culturesex vivo. Collectively, our results suggest that TRAIL produced by CD8+T cells contributes to disease resolution by helping to clear WNV infection from neurons in the central nervous system.
Cohesins Repress Kaposi's Sarcoma-Associated Herpesvirus Immediate Early Gene Transcription during Latency
Authors: Chen Horng-Shen , Wikramasinghe Priyankara , Showe Louise , Lieberman Paul M.
Published: June 2012

Chromatin-organizing factors such as CTCF and cohesins have been implicated in the control of complex viral regulatory programs. We investigated the role of CTCF and cohesins in the control of the switch from latency to the lytic cycle for Kaposi's sarcoma-associated herpesvirus (KSHV). We found that cohesin subunits but not CTCF are required for the repression of KSHV immediate early gene transcription. Depletion of the cohesin subunits Rad21, SMC1, and SMC3 resulted in lytic cycle gene transcription and viral DNA replication. In contrast, depletion of CTCF failed to induce lytic transcription or DNA replication. Chromatin immunoprecipitation with high-throughput sequencing (ChIP-Seq) revealed that cohesins and CTCF bound to several sites within the immediate early control region for ORF50 and to more distal 5′ sites that also regulate the divergently transcribed ORF45-ORF46-ORF47 gene cluster. Rad21 depletion led to a robust increase in ORF45, ORF46, ORF47, and ORF50 transcripts, with similar kinetics to that observed with chemical induction by sodium butyrate. During latency, the chromatin between the ORF45 and ORF50 transcription start sites was enriched in histone H3K4me3, with elevated H3K9ac at the ORF45 promoter and elevated H3K27me3 at the ORF50 promoter. A paused form of RNA polymerase II (Pol II) was loosely associated with the ORF45 promoter region during latency but was converted to an active elongating form upon reactivation induced by Rad21 depletion. Butyrate treatment caused a rapid dissociation of cohesins and loss of CTCF binding at the immediate early gene locus, suggesting that cohesins may be a direct target of butyrate-mediated lytic induction. Our findings implicate cohesins as a major repressor of KSHV lytic gene activation and show that they function coordinately with CTCF to regulate the switch between latent and lytic gene activity.