bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between structure and convulsant properties of some beta-lactam antibiotics following intracerebroventricular microinjection in rats
Authors: De Sarro A , Ammendola D , Zappala M , Grasso S , De Sarro G B
Published: June 2012

The epileptogenic activities of several beta-lactam antibiotics were compared following their intracerebroventricular administration in rats. Different convulsant potencies were observed among the various beta-lactam antibiotics tested, but the epileptogenic patterns were similar. The patterns consisted of an initial phase characterized by wet-dog shakes followed by head tremor, nodding, and clonic convulsions. After the largest doses of beta-lactam antibiotics injected, clonus of all four limbs and/or the trunk, rearing, jumping, falling down, escape response, transient tonic-clonic seizures, and sometimes generalized seizures were observed, followed by a postictal period with a fatal outcome. At a dose of 0.033 mumol per rat, cefazolin was the most powerful epileptogenic compound among the drugs tested. It was approximately three times more potent than benzylpenicillin in generating a response and much more potent than other cephalosporins, such as ceftriaxone, cefoperazone, and cefamandole. No epileptogenic signs were observed with equimolar doses of cefotaxime, cefonicid, cefixime, and ceftizoxime in this model. The more convulsant compounds (i.e., cefazolin and ceftezole) are both characterized by the presence of a tetrazole nucleus at position 7 and show a marked chemical similarity to pentylenetetrazole. Imipenem and meropenem, the two carbapenems tested, also showed epileptogenic properties, but imipenem was more potent than meropenem, with a convulsant potency similar to those of ceftezole and benzylpenicillin. In addition, the monobactam aztreonam possessed convulsant properties more potent than those of cefoperazone and cefamandole. This suggest that the beta-lactam ring is a possible determinant of production of epileptogenic activity, with likely contributory factors in the substitutions at the 7-aminocephalosporanic or 6-aminopenicillanic acid that may increase or reduce the epileptogenic properties of the beta-lactam antibiotics. While the structure-activity relationship was also investigated, there seem to be no convincing correlations among the rank order of lipophilicities and the convulsant potencies of the compounds studied. The lack of marked convulsant properties of cefixime, cefonicid, cefuroxime, and cephradine suggests that these antibiotics may interact with a binding site which is different from that by which the beta-lactam antibiotics exert their convulsant effects or may demonstrate a reduced affinity for the relevant site(s).
In vitro activities of a streptogramin (RP59500), three macrolides, and an azalide against four respiratory tract pathogens
Authors: Barry A L , Fuchs P C
Published: June 2012

Broth microdilution tests were carried out with 2,671 respiratory tract isolates from 19 medical centers throughout the continental United States. The tests compared a streptogramin (RP59500) to erythromycin, dirithromycin, clarithromycin, and azithromycin against Streptococcus pneumoniae, S. pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. Against macrolide-susceptible strains, the potency of RP59500 was similar to that of the macrolides: the azalide, azithromycin, was two to four times more potent against H. influenzae. The azalide and three macrolides showed nearly complete cross-resistance. At 2.0 micrograms/ml or less, the streptogramin, RP59500, was active against both macrolide-resistant and -susceptible strains of S. pneumoniae (MIC for 50% of the strains tested, 0.25 microgram/ml; MIC for 90% of the strains tested, 0.5 microgram/ml).
Explanations for high rates of eradication with triple therapy using metronidazole in patients harboring metronidazole-resistant Helicobacter pylori strains
Authors: van Zwet A A , Thijs J C , de Graaf B
Published: June 2012

In 4 of 17 Helicobacter pylori strains obtained from antral biopsy samples, the registered primary resistance (MIC, > 32 microgram/ml) appeared to be nonstable after prolonged microaerophilic incubation. In all resistant strains tested, susceptibility could be obtained when culture under normal microaerophilic conditions was preceded by a period of anaerobic incubation. Both of these findings may explain the observed discrepancy between the results of in vitro susceptibility tests and the eradication obtained in vivo.
Pharmacokinetics of michellamine B, a naphthylisoquinoline alkaloid with in vitro activity against human immunodeficiency virus types 1 and 2, in the mouse and dog
Authors: Supko J G , Malspeis L
Published: June 2012

Michellamine B (MB) is a naturally occurring naphthylisoquinoline alkaloid of novel chemical structure with activity against human immunodeficiency virus (HIV) types 1 and 2 in vitro. In conjunction with its preclinical evaluation, the plasma pharmacokinetics of MB was characterized in mice and dogs treated by intravenous infusions of 1- and 15-min durations, respectively. At doses ranging from 1 to 9 mg/kg of body weight, the drug exhibited apparent first-order kinetics in both species, affording triexponential plasma concentration-time profiles. Treatment with doses of 5 to 9 mg/kg provided peak plasma levels within the range that completely inhibits the cytopathic effects of HIV upon cultured human lymphoblastoid cells (50 to 100 micrograms/ml) without evidence of toxicity. MB had a biological half-life of 2.8 +/- 0.8 h in mice, with a mean residence time of 2.1 +/- 0.3 h, and a total plasma clearance of 2.4 +/- 0.5 ml/min/kg (mean +/- standard deviation; n = 3); however, the terminal-phase contribution to the area under the plasma profile from time zero to infinity was 44.6% +/- 12.9%. In contrast, the terminal phase was the primary determinant of drug disposition in dogs, accounting for 74.1% +/- 2.8% (n = 3) of the area under the curve. Furthermore, the systemic duration of MB was significantly longer in the dogs than in mice, as indicated by mean values of the apparent half-life (11.6 +/- 1.2 h), mean residence time (12.3 +/- 1.8 h), and clearance (0.50 +/- 0.08 ml/min/kg). However, there were no statistical difference between its apparent volume of distribution in the mice (0.60 +/- 0.08 liters/kg) and dogs (0.50 +/- 0.07 liters/kg). A single dog was also treated with a total dose of 97 mg/kg given as a 72-h constant-rate intravenous infusion, since prolonged systemic exposure to potentially therapeutic drug concentrations will very likely be required for clinical anti-HIV effects. Within 4 h after starting the infusion, the plasma MB concentration exceeded 18 micrograms/ml, it reported 50% effective concentration against HIV in vitro, and subsequently increased to 41 micrograms/ml at the end of the infusion. There were no clinical or pathological indications of toxicity. Whereas the total plasma clearance (0.48 ml/min/kg) was within the range observed for dogs treated by 15-min infusion, extension of the postinfusion sampling period from 24 h to 4 days facilitated better definition of the terminal exponential phase, yielding a value of 25.6 h for the biological half-life of MB. The amount of drug excreted by dogs unchanged in the urine ranged from 3.7 to 11.1% of the administered dose. Thus, the major pathways by which the drug is eliminated from the body remain to be identified. On the basis of these findings, continued development of MB as a novel lead compound for the treatment of HIV infection is warranted.
Pharmacokinetics and metabolism of 14C-isepamicin in humans following intravenous administration
Authors: Lin C , Korduba C , Affrime M , Radwanski E , Nomeir A , Batra V , Cutler D , Cayen M N
Published: June 2012

Twelve healthy adult male volunteers received 1 g (base equivalent) of 14C-isepamicin (131 microCi) as an intravenous bolus over 5 min. The areas under the plasma concentration-time curves at infinity for isepamicin (196 micrograms*h/ml) and total radioactivity (164 micrograms*h/ml) were similar, indicating no biotransformation of isepamicin. The disappearance of isepamicin from plasma followed a triexponential decline, with half-lives of 0.17, 2.12, and 34 h for the alpha, beta, and gamma phases, respectively. However, the contribution of the gamma phase to the total area under the concentration-time curve was only 2.6%. There were no detectable metabolites in plasma and urine, confirming that isepamicin was not biotransformed. The cumulative levels of isepamicin and total radioactivity excretion in urine from 0 to 120 h were 97.3 and 92.1% of the dose, respectively, indicating that the drug was excreted mainly as unchanged isepamicin in urine.
Growth impairment resulting from expression of influenza virus M2 protein in Saccharomyces cerevisiae: identification of a novel inhibitor of influenza virus
Authors: Kurtz S , Luo G , Hahnenberger K M , Brooks C , Gecha O , Ingalls K , Numata K , Krystal M
Published: June 2012

The gene encoding M2, the ion channel-forming protein of influenza virus A, was expressed under the control of an inducible promoter in Saccharomyces cerevisiae. By using single and multicopy plasmids containing GAL promoter-M2 fusions, a correlation was observed between plasmid copy number and growth in medium inducing M2 expression. Cells expressing M2 from multicopy plasmids have reduced growth rates, suggesting that high levels of M2 are toxic to growth. The addition of amantadine, a compound known to block the ion channel activity of certain M2 alleles, restores the growth rates to wild-type levels in cells expressing an amantadine-susceptible allele of M2 but not an amantadine-resistant allele of M2, suggesting that M2 expression in S. cerevisiae results in the formation of functional M2 ion channels. Measurements of extracellular acidification by microphysiometry suggest that proton efflux in M2-expressing cells is altered and that the addition of amantadine permits the reestablishment of the proton gradient. The growth impairment phenotype resulting from M2 expression was used to develop a high-capacity screening assay which identified a novel inhibitor possessing an antiviral profile similar to that of amantadine.
Safety and efficacy of long-term use of rimantadine for prophylaxis of type A influenza in nursing homes
Authors: Monto A S , Ohmit S E , Hornbuckle K , Pearce C L
Published: June 2012

The safety and efficacy of rimantadine for long-term prophylaxis of influenza A (H3N2) infection were evaluated among elderly residents in 10 nursing homes. Within each nursing home, participating residents were randomly assigned to receive placebo or rimantadine at 100 or 200 mg/day. Residents were evaluated daily for symptoms and significant health events as possible side effects, as well as for influenza-like illness. The study medications were administered to 328 residents for up to 8 weeks, with no statistically significant differences in the frequencies of gastrointestinal or central nervous system symptoms between the groups. However, residents in the active medication groups were more likely to withdraw from the study and to experience various health events including death; some but not all of these differences were statistically significant. Efficacy evaluations were carried out on the 68 vaccinated residents in the two nursing homes with demonstrated influenza virus activity. Rimantadine appeared to provide an additional protective effect beyond vaccination in reducing the risk of clinical and laboratory-confirmed influenza-like illness; however, the efficacy estimates were never statistically significant. The efficacies of the 100- and 200-mg/day dosages were generally similar. When data for the 100- and 200-mg/day dosage groups were combined and compared with data for the group receiving placebo, the efficacy of rimantadine in reducing the risk of clinical influenza-like illness was estimated to be 58 percent (P = 0.079). The results suggest the relative safety and clinical efficacy of using rimantadine for influenza prophylaxis among vaccinated elderly individuals and support the recommendation for a dosage reduction to 100 mg/day in this population.
High-throughput screen for detecting antimycobacterial agents
Authors: Chung G A , Aktar Z , Jackson S , Duncan K
Published: June 2012

A simple, robust assay system which can be used to screen for inhibitors of mycobacterial growth has been developed. A strain of the rapidly growing saprophyte Mycobacterium aurum is used as the test organism. Inhibition of its growth is highly predictive of activity against Mycobacterium tuberculosis, which cannot itself be used in screening because of its growth characteristics and highly infectious nature. The viability of M. aurum in the presence of a test sample is monitored by measuring the uptake of radiolabelled uracil into the cells. In a microtiter plate format, the screen has the potential for testing several thousand samples per day.
In vitro activities of 22 beta-lactam antibiotics against penicillin-resistant and penicillin-susceptible viridans group streptococci isolated from blood
Authors: Alcaide F , Liñares J , Pallares R , Carratala J , Benitez M A , Gudiol F , Martin R
Published: June 2012

A total of 410 strains of viridans group streptococci isolated consecutively from blood were tested by the microdilution method for in vitro susceptibility to 22 beta-lactam antibiotics. One hundred thirty-eight strains (33.6%) were resistant to penicillin with a MIC range of 0.25 to 8 micrograms/ml. MICs of all beta-lactam agents tested were higher for penicillin-resistant strains than for susceptible strains. These antibiotics were classified into three groups according to their in vitro activities (MICs at which 50 and 90% of the isolates are inhibited). Beta-Lactams of the first group (these included imipenem, cefpirome, FK-037, cefditoren, cefotaxime, ceftriaxone, and cefepime) showed activities higher than or similar to that of penicillin against penicillin-resistant viridans group streptococci. However, 80% of highly penicillin-resistant Streptococcus mitis organisms required cefotaxime and ceftriaxone MICs of > or = 2 micrograms/ml (range, 2 to 16 micrograms/ml). Beta-Lactams of the second group (cefpodoxime, ampicillin, amoxicillin-clavulanate, piperacillin, and cefuroxime) showed lower activities than penicillin. Finally, antibiotics of the third group (cephalothin, oxacillin, ceftazidime, cefixime, cefaclor, cefetamet, cefadroxil, cephalexin, and ceftibuten) showed poor in vitro activities. Therefore, some of the beta-lactam agents included in the first group could be an acceptable alternative in the treatment of serious infections due to strains highly resistant to penicillin, although clinical experience is needed.
In vitro and in vivo activities of the benzoxazinorifamycin KRM-1648 against Mycobacterium tuberculosis
Authors: Hirata T , Saito H , Tomioka H , Sato K , Jidoi J , Hosoe K , Hidaka T
Published: June 2012

The in vitro and in vivo activities of a new benzoxazinorifamycin, KRM-1648 (KRM), against Mycobacterium tuberculosis were studied. The MIC at which 50% of the isolates are inhibited (MIC50) and the MIC90 of KRM for 30 fresh isolates of M. tuberculosis measured by the BACTEC 460 TB System were 0.016 and 2 micrograms/ml, respectively. These values were much lower than those for rifampin (RMP), which were 4 and >128 micrograms/ml, respectively, and considerably lower than those for rifabutin (RBT), which were 0.125 and 8 micrograms/ml, respectively. A correlational analysis of the MICs of these drugs for the clinical isolates revealed the presence of cross-resistance of the organisms to KRM and either RMP or RBT although the MICs of KRM were distributed over a much lower range than were those of the other two drugs. KRM and RMP at concentrations of 1 to 10 micrograms/ml almost completely inhibited the bacterial growth of RMP-sensitive strains (H37Rv, Kurono, and Fujii) of M. tuberculosis phagocytosed in macrophage-derived J774.1 cells. KRM was more active than RMP in inhibiting the growth of the RMP-resistant (MIC = 8 micrograms/ml) Kurata strain but failed to show such an effect against the RMP-resistant (MIC >128 micrograms/ml) Watanabe stain. When KRM was given to M. tuberculosis-infected mice at dosages of 5 to 20 mg/kg of body weight by gavage, one daily six times per week from day 1 after infection, it was much more efficacious than RMP against infections induced in mice by the RMP-sensitive Kurono strain, as measured by a reduction of rates of mortality, a reduction of the frequency and extent of gross lung lesions, histopathological changes in lung tissues, and a decrease in the bacterial loads in the lungs and spleens of infected mice. KRM also displayed significant therapeutic efficacy against infection induced by the RMP-resistant Kurata strain, while neither KRM nor RMP was efficacious against infection by the RMP-resistant Watanabe strain. In the case of infection with the Kurono strain, the efficacy of the drugs in prolonging the time of survival was in the order KRM, RBT, RMP. KRM was much more efficacious than RMP, when given at 1- to 4-week intervals. These findings suggest that KRM may be useful for the clinical treatment of tuberculosis contracted through RMP-sensitive strains, even when it is administered at long intervals.
Antimycobacterial activity of a new rifamycin derivative, 3-(4-cinnamylpiperazinyl iminomethyl) rifamycin SV (T9)
Authors: Reddy V M , Nadadhur G , Daneluzzi D , Dimova V , Gangadharam P R
Published: June 2012

The antimycobacterial activities of a new rifampin (RIF) derivative, 3-(4-cinnamylpiperazinyl iminomethyl) rifamycin SV (To), against 20 susceptible and multidrug-resistant strains of Mycobacterium tuberculosis and 20 Mycobacterium avium complex (MAC) strains were investigated. The radiometric MICs of T9 for M. tuberculosis were significantly lower than those of RIF. The MICs of T9 and RIF at which 90% of the RIF-susceptible strains were inhibited were < or = 0.25 and < or = 0.5 micrograms/ml, respectively. Interestingly, T9 had lower MICs against some RIF-resistant M. tuberculosis strains. T9 had better activity against MAC strains, and the MIC at which 90% of the MAC strains were inhibited was < or = 0.125 micrograms/ml, and that of RIF was < or = 2.0 micrograms/ml. T9 also showed high in vitro bactericidal and intracellular activities which were significantly superior to those of RIF against both M. tuberculosis, and MAC strains. More importantly, T9 showed excellent in vivo activity against M. tuberculosis H37Rv compared with that of RIF in both the lungs and spleens of C57BL/6 mice, indicating the potential therapeutic value of T9 in the treatment of mycobacterial infections.
In vitro interactions between different beta-lactam antibiotics and fosfomycin against bloodstream isolates of enterococci
Authors: Pestel M , Martin E , Aucouturier C , Lemeland J F , Caron F
Published: June 2012

The effects of 16 different beta-lactam-fosfomycin combinations against 50 bloodstream enterococci were compared by a disk diffusion technique. Cefotaxime exhibited the best interaction. By checkerboard studies, the cefotaxime-fosfomycin combination provided a synergistic bacteriostatic effect against 45 of the 50 isolates (MIC of cefotaxime at which 90% of the isolates were inhibited, >2,048 micrograms/ml; MIC of fosfomycin at which 90% of the isolates were inhibited, 128 micrograms/ml; mean of fractional inhibitory concentration indexes, 0.195). By killing curves, cefotaxime (at 64 micrograms/ml) combined with fosfomycin (at > or = 64 micrograms/ml) was bactericidal against 6 of 10 strains tested.
NP-06: a novel anti-human immunodeficiency virus polypeptide produced by a Streptomyces species
Authors: Chokekijchai S , Kojima E , Anderson S , Nomizu M , Tanaka M , Machida M , Date T , Toyota K , Ishida S , Watanabe K
Published: June 2012

From an extract of a Streptomyces culture, we identified and purified a novel compound, NP-06, which is active against human immunodeficiency virus (HIV) in vitro. Analyses indicate that NP-06 is a hydrophobic 21-mer oligopeptide, N terminally cyclized through the side chain of Asp-9, containing two intramolecular cystine linkages with a molecular weight of 2,163.4. The 50% inhibitory concentrations were 2.8 and 1.3 microM when NP-06 was tested for in vitro anti-HIV-1 activity in ATH8 cells and phytohemagglutinin-activated peripheral blood mononuclear cells, respectively, NP-06 appears to block the early stage of HIV-1 infection, most likely at the stage of virus-cell fusion.
Short-term topical therapy of experimental tinea pedis in guinea pigs with lanoconazole, a new imidazole antimycotic agent
Authors: Niwano Y , Tabuchi T , Kanai K , Hamaguchi H , Uchida K , Yamaguchi H
Published: June 2012

The therapeutic efficacy of short-term treatment with a 1% cream of lanoconazole, a new imidazole antimycotic agent, in comparison with that of a 1% cream of terbinafine was evaluated in the guinea pig model of tinea pedis. Each agent was topically applied once a day for 3 or 7 consecutive days, starting on day 10 postinfection, and a culture study was conducted on day 5 after the last treatment with each agent. The 1% cream of lanoconazole was as highly effective as the 1% cream of terbinafine in terms of eradicating the fungi from the infected feet.
MICs of 28 antibiotic compounds for 14 Bartonella (formerly Rochalimaea) isolates
Authors: Maurin M , Gasquet S , Ducco C , Raoult D
Published: June 2012

We assessed in vitro the antibiotic susceptibilities of 14 Bartonella isolates of the species B. quintana, B. vinsonii, B. henselae, and B. elizabethae. Columbia agar base supplemented with 5% horse blood was used as the antibiotic assay medium. Bacterial growth could be evaluated within 5 days after incubation of the plates at 37 degrees C in a 5% carbon dioxide atmosphere. The MICs at which 90% of isolates are inhibited (MIC90s) were 0.06 microgram/ml for penicillin G and amoxicillin and 0.25 microgram/ml for ticarcillin and cefotaxime. The MIC90s of oxacillin and cephalothin were 4 and 16 micrograms/ml, respectively. The MIC90s ranged from 1 to 4 micrograms/ml for aminoglycosides. Erythromycin, doxycycline, and rifampin displayed MIC90s of 0.12, 0.12, and 0.25 microgram/ml, respectively. MIC90s were 1 and 5 micrograms/ml for trimethoprim-and sulfamethoxazole, respectively, 64 micrograms/ml for fosfomycin, and 16 micrograms/ml for colistin and vancomycin. The study confirms the high levels of in vitro susceptibility of Bartonella agents to antibiotics.
In vitro effectiveness of azithromycin against doxycycline-resistant and -susceptible strains of Rickettsia tsutsugamushi, etiologic agent of scrub typhus
Authors: Strickman D , Sheer T , Salata K , Hershey J , Dasch G , Kelly D , Kuschner R
Published: June 2012

In an effort to find a potential alternative treatment for scrub typhus, we evaluated the effectiveness of the standard drug doxycycline and the new macrolide azithromycin against a doxycycline-susceptible strain (Karp) and a doxycycline-resistant strain (AFSC-4) of Rickettsia tsutsugamushi. The antibiotics were tested in an in vitro assay system in which infected mouse fibroblast cells (L929) were incubated for 3 days in various concentrations of the drugs. Rickettsial growth was evaluated by direct visual counts of rickettsiae in Giemsastained cells or by flow cytometry. Initial tests were conducted at the concentration of each antibiotic considered to be the upper breakpoint for susceptibility (16 micrograms/ml for doxycycline and 8 micrograms/ml for azithromycin). Growth of both Karp and AFSC-4 was strongly inhibited with both antibiotics, as measured by visual counts, although the percentage of cells infected with AFSC-4 in the presence of doxycycline was three times greater than the percentage of cells infected with Karp but was only 60% as great as the percentage of cells infected with Karp in the presence of azithromycin. Flow cytometry confirmed that rickettsial growth occurred in the absence of antibiotics, but it failed to detect it in the presence of high concentrations of either drug. Visual counts of rickettsial growth at lower concentrations of the antibiotics (0.25 to 0.0078 microgram/ml) showed that the Karp strain was 16 times more susceptible that the AFSC-4 strain to doxycycline. Azithromycin was much more effective than doxycycline against AFSC-4, inhibiting rickettsial growth at 0.0156 microgram/ml to levels below that achieved by 0.25 microgram of doxycycline per ml. Azithromycin was also more effective than doxycycline against the Karp strain, causing greater reductions in the number of rickettsiae per cell at lower concentrations. If in vivo testing confirms the in vitro effectiveness of azithromycin, it may prove to be the drug of choice for the treatment of scrub typhus in children and pregnant women, who should not take doxycycline, and in patients with refractory disease from locations where doxycycline-resistant strains of R. tsutsugamushi have been found. When tested in an in vitro assay system, azithromycin was more effective than doxycycline against doxycycline-susceptible and -resistant strains of R. tsutsugamushi.
T30177, an oligonucleotide stabilized by an intramolecular guanosine octet, is a potent inhibitor of laboratory strains and clinical isolates of human immunodeficiency virus type 1
Authors: Ojwang J O , Buckheit R W , Pommier Y , Mazumder A , De Vreese K , Esté J A , Reymen D , Pallansch L A , Lackman-Smith C , Wallace T L
Published: June 2012

T30177, an oligonucleotide composed of only deoxyguanosine and thymidine, is 17 nucleotides in length and contains single phosphorothioate internucleoside linkages at its 5' and 3' ends for stability. This oligonucleotide does not share significant primary sequence homology with or possess any complementary (antisense) sequence motifs to the human immunodeficiency virus type 1 (HIV-1) genome. T30177 inhibited replication of multiple laboratory strains of HIV-1 in human T-cell lines, peripheral blood lymphocytes, and macrophages. T30177 was also found to be capable of inhibiting multiple clinical isolates of HIV-1 and preventing the cytopathic effect of HIV-1 in primary CD4+ T lymphocytes. In assays with human peripheral blood lymphocytes there was no observable toxicity associated with T30177 at the highest concentration tested (100 microM), while the median inhibitory concentration was determined to be in the range of 0.1 to 1.0 microM for the clinical isolates tested, resulting in a high therapeutic index for this drug. In temporal studies, the kinetics of addition of T30177 to infected cell cultures indicated that, like the known viral adsorption blocking agents dextran sulfate and Chicago sky blue, T30177 needed to be added to cells during or very soon after viral infection. However, analysis of nucleic acids extracted at 12 h postinfection from cells treated with T30177 at the time of virus infection established the presence of unintegrated viral cDNA, including circular proviral DNA, in the treated cells. In vitro analysis of viral enzymes revealed that T30177 was a potent inhibitor of HIV-1 integrase, reducing enzymatic activity by 50% at concentrations in the range of 0.050 to 0.09 microM. T30177 was also able to inhibit viral reverse transcriptase activity; however, the 50% inhibitory value obtained was in the range of 1 to 10 microM, depending on the template used in the enzymatic assay. No observable inhibition of viral protease was detected at the highest concentration of T30177 used (10 microM). In experiments in which T30177 was removed from infected cell cultures at 4 days post-HIV-1 infection, total suppression of virus production was observed for more than 27 days. PCR analysis of DNA extracted from cells treated in this fashion was unable to detect the presence of viral DNA 11 days after removal of the drug from the infected cell cultures. The ability of T30177 to inhibit both laboratory and clinical isolates of HIV-1 and the experimental data which suggest that T30177 represents a novel class of integrase inhibitors indicate that this compound is a viable candidate for evaluation as a therapeutic agent against HIV-1 in humans.
Proposed criteria for interpretation of susceptibilities of strains of Neisseria gonorrhoeae to ciprofloxacin, ofloxacin, enoxacin, lomefloxacin, and norfloxacin
Authors: Knapp J S , Hale J A , Neal S W , Wintersheid K , Rice R J , Whittington W L
Published: June 2012

The susceptibilities of 45 strains of Neisseria gonorrhoeae, including 25 strains susceptible to ciprofloxacin (MICs, < or = 0.06 microgram/ml) and 20 strains exhibiting decreased susceptibilities to ciprofloxacin (MICs, > or = 0.125 microgram/ml), to ciprofloxacin, ofloxacin, enoxacin, lomefloxacin, norfloxacin, and nalidixic acid were determined by agar dilution and disk diffusion. On the basis of theoretical calculations of predicted susceptibilities at which infections may fail therapy (supported by observed failures of infections to respond to the therapeutic doses of enoxacin and ciprofloxacin), the Centers for Disease Control and Prevention has adopted the following agar dilution breakpoints for interpretation of resistance to these agents: MICs of > or = 1.0 microgram of ciprofloxacin, enoxacin, and norfloxacin per ml and MICs of > or = 2.0 micrograms of ofloxacin and lomefloxacin per ml. The corresponding disk diffusion breakpoints for these agents were as follows: ciprofloxacin, < or = 29 mm; ofloxacin, < or = 24 mm; enoxacin, < or = 31 mm; lomefloxacin, < or = 26 mm; and norfloxacin, < or = 32 mm. The Centers for Disease Control and Prevention recommends two strains as interim quality control strains for susceptibility testing of ciprofloxacin and ofloxacin. These are N. gonorrhoeae CDC-10,328 (MIC of ciprofloxacin, 0.125 to 0.25 microgram/ml [inhibition zone diameter range, 30 to 34 mm]; MIC of ofloxacin, 0.5 microgram/ml [inhibition zone diameter range, 27 to 32 mm]) and N. gonorrhoeae CDC-10,329 (MIC of ciprofloxacin, 1.0 to 2.0 micrograms/ml [zone inhibition diameter range, 21 to 26 mm]; MIC of ofloxacin 2.0 micrograms/ml [inhibition zone diameter range, 18 to 21 mm]).
Identification of chromosomal mobile element conferring high-level vancomycin resistance in Enterococcus faecium
Authors: Handwerger S , Skoble J
Published: June 2012

A clinical isolate of Enterococcus faecium that contains a chromosomally encoded vanA gene cluster, Tn1546::IS1251, transferred vancomycin resistance to the plasmid-free strain Enterococcus faecalis JH2-2 during filter matings. Hybridization of a vanHAXY probe to SmaI restriction-digested genomic DNA separated by pulsed-field gel electrophoresis showed that the vanA gene cluster was located on a 40-kb fragment in the original donor strain and on fragments of different sizes (150 to 450 kb) in the transconjugants. No hybridization to vanA gene cluster probes was obtained with plasmid DNA preparations from the donor or transconjugants. These results suggested that in each case, the van genes had integrated into the recipient chromosome. The transconjugants in turn could act as donors of vancomycin resistance, and resistance was transferable to a Rec- recipient. The results of restriction analyses and DNA hybridizations of genomic DNA from the donor and transconjugants were consistent with the transfer of a mobile element that includes the 12.3-kb Tn1546::IS1251 gene cluster and at least 13 kb of additional DNA. This element has been tentatively designated Tn5482. DNA sequence analysis of a fragment predicted to contain the left end of Tn5482 revealed two insertion sequence-like elements: IS1216V and an apparently truncated IS3-like element. Restriction mapping and DNA hybridization patterns of the van gene clusters of three additional clinical isolates from New York City showed an element similar to Tn5482. Transfer of Tn5482 and related elements may be involved in dissemination of vancomycin resistance.
In vitro determination of optimal antifungal combinations against Cryptococcus neoformans and Candida albicans
Authors: Ghannoum M A , Fu Y , Ibrahim A S , Mortara L A , Shafiq M C , Edwards J E , Criddle R S
Published: June 2012

There is currently no rapid, reliable, and reproducible in vitro technique to describe the growth-inhibitory interactions of antifungal drug combinations over a wide range of drug concentrations. We have developed a microdilution plate assay that was used to determine optimal drug combinations and concentrations of one-, two-, and three-drug regimens of amphotericin B (AmphB), fluconazole (FLU), and 5-fluorocytosine (5FC) for growth inhibition of three isolates each of Cryptococcus neoformans and Candida albicans. These growth inhibition data were then used in a multifactorial design technique to (i) generate contour and surface response plots to aid visual interpretation and (ii) develop mathematical equations describing the growth responses of the fungi to a wide range of antifungal concentrations and ratios. Our data indicated that (i) antifungal drug-drug interactions affecting yeast growth are complex functions of the drugs used in combination, their absolute concentrations, and also their relative (proportional) concentrations; (ii) AmphB-FLU combinations had additive effects against C. albicans over wide concentration ranges for each agent but were indifferent (i.e., were less than additive) in their inhibitory effect on C. neoformans; (iii) other two-drug combinations (FLU-5FC or AmphB-5FC) had indifferent effects on the growth of both fungi; and (iv) three-drug combinations (AmphB-FLU-5FC) showed an additive inhibitory effect on the growth of both C. albicans and C. neoformans. The finding that no antagonism was observed in combinations employing AmphB and FLU in this in vitro model is of critical importance since it argues against the current theoretical concept, based on the individual drug's mode of action, of antagonism between these two drugs. These microdilution techniques provide a method to determine rational regimens of antifungal agents in multidrug combinations for future testing to correlate in vitro activity with in vivo response. The use of this approach has made the evaluation of complex antifungal drug-drug interactions possible and provided important new information to the evolving field of antifungal drug combination.
Biogenesis of the mycobacterial cell wall and the site of action of ethambutol
Authors: Mikusová K , Slayden R A , Besra G S , Brennan P J
Published: June 2012

The effect of ethambutol (EMB) is primarily on polymerization steps in the biosynthesis of the arabinan component of cell wall arabinogalactan (AG) of Mycobacterium smegmatis. Inhibition of the synthesis of the arabinan of lipoarabinomannan (LAM) occurred later, and thus in the cases of AG and LAM, the polymerization of D-arabinofuranose apparently involves separate pathways. While the synthesis of these arabinans was normal in an EMB-resistant isogeneic strain, the addition of EMB to the resistant strain resulted in partial inhibition of the synthesis of the arabinan of LAM and the emergence of a novel, truncated form of LAM, indicating partial susceptibility of the resistant gene(s) and providing a new intermediate in the LAM biosynthetic sequence. A consequence of inhibition of AG arabinan biosynthesis is the lack of new sites for mycolate attachment and thus the channeling of mycolate residues into a variety of free lipids which then accumulate. The primary biochemical effects of EMB can be explained by postulating separate AG and LAM pathways catalyzed by a variety of extramembranous arabinosyl transferases with various degrees of sensitivity to EMB.
Comparison of the bactericidal activities of ofloxacin and ciprofloxacin alone and in combination with ceftazidime and piperacillin against clinical strains of Pseudomonas aeruginosa
Authors: Klepser M E , Patel K B , Nicolau D P , Quintiliani R , Nightingale C H
Published: June 2012

On the basis of MIC data, ciprofloxacin exhibits superior activity against Pseudomonas aeruginosa than the other currently available fluoroquinolones do. Despite the antipseudomonal advantage noted for ciprofloxacin monotherapy, it is unknown whether this advantage is maintained when the fluoroquinolones are used in combination with antipseudomonal beta-lactams such as ceftazidime and piperacillin. Twelve healthy volunteers were enrolled in this open-label, randomized, steady-state, six-way cross-over, comparative trial. All subjects received the following regimens: (i) 400 mg of ofloxacin given intravenously (i.v.) every 12 h (q12h), (ii) 400 mg of ciprofloxacin given i.v. q12h, (iii) 400 mg of ofloxacin given i.v. q12h plus 1 g of ceftazidime given i.v. every 8 h (q8h), (iv) 400 mg of ciprofloxacin given i.v. q12h plus 1 g of ceftazidime given i.v. q8h, (v) 400 mg of ofloxacin given i.v. q12h plus 4 g of piperacillin given i.v. q8h, and (vi) 400 mg of ciprofloxacin given i.v. q12h plus 4 g of piperacillin given i.v. q8h. Serum bactericidal titers with subsequent calculation of the area under the bactericidal curve were determined against three clinical isolates of P. aeruginosa. As monotherapy, ciprofloxacin demonstrated superior antipseudomonal activity than ofloxacin did; however, combination of these agents with ceftazidime yielded remarkably similar and statistically comparable activity profiles. In contrast, ciprofloxacin-piperacillin retained a bactericidal advantage over ofloxacin-piperacillin. Although ciprofloxacin exhibits superior antipseudomonal activity when used as monotherapy, combination of ofloxacin or ciprofloxacin with ceftazidime yielded equivalent activity profiles against susceptible strains of P. aeruginosa.
Comparison of Etest and National Committee for Clinical Laboratory Standards broth macrodilution method for antifungal susceptibility testing: enhanced ability to detect amphotericin B-resistant Candida isolates
Authors: Wanger A , Mills K , Nelson P W , Rex J H
Published: June 2012

The National Committee for Clinical Laboratory Standards (NCCLS) proposed macrobroth reference method (M27P) for susceptibility testing of yeasts is technically difficult. We evaluated Etest, a simple agar-based MIC methodology, as a possible alternative. In studies of six yeast quality control strains, Etest yielded results identical to those obtained by the NCCLS reference method for both amphotericin B and fluconazole. In studies of 91 clinical Candida isolates, agreement +/- 2 dilutions between the two methods was 95% for fluconazole with phosphate-buffered RPMI 1640 agar and 96 to 97% for amphotericin B with either MOPS (morpholinepropanesulfonic acid)-buffered RPMI 1640 agar or antibiotic medium 3 agar. While the two methods had excellent general agreement, testing of a collection of amphotericin B-resistant isolates demonstrated that, unlike the NCCLS reference method, Etest readily identified the resistant isolates and could do so with a defined medium. Etest is equivalent to the NCCLS proposed method for susceptibility testing of yeasts and superior in its ability to detect amphotericin B resistance.
In vitro activities of the lichen secondary metabolites vulpinic acid, (+)-usnic acid, and (-)-usnic acid against aerobic and anaerobic microorganisms
Authors: Lauterwein M , Oethinger M , Belsner K , Peters T , Marre R
Published: June 2012

Secondary metabolites of different species of lichen were tested for their activities against a variety of microbial species. While gram-negative rods and fungi were not inhibited by these compounds, Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, and some anaerobic species (Bacteroides and Clostridium species) were susceptible at the concentrations tested. Vulpinic acid generally was less active than usnic acid, regardless of its stereochemistry. The susceptibility to usnic acid was not impaired in clinical isolates of S. aureus resistant to methicillin and/or mupirocin.
In vitro and in vivo antibiotic susceptibilities of ELB rickettsiae
Authors: Radulovic S , Higgins J A , Jaworski D C , Azad A F
Published: June 2012

The activities of doxycycline, rifampin, chloramphenicol, and erythromycin against ELB rickettsiae (Rickettsia azadi) were determined by dye uptake and plaque assays. Plaque formation in Vero cells was inhibited by 0.12 microgram of doxycycline per ml. The data presented demonstrate the susceptibility of ELB rickettsiae to commonly used antibiotics for the treatment of rickettsial diseases.
Effect of protein binding on penetration of beta-lactams into rabbit peripheral lymph
Authors: Woodnutt G , Berry V , Mizen L
Published: June 2012

The relevance of protein binding to penetration of beta-lactams into body fluids was investigated by examining the distribution of amoxicillin, ceftriaxone, clavulanic acid, temocillin, and ticarcillin into rabbit peripheral lymph after intravenous administration. The elimination half-lives in rabbit plasma varied between 0.34 h (temocillin) and 1.80 h (ceftriaxone), and the half-lives measured in lymph were similar to those in plasma (0.37 to 1.76 h). The percent penetration (area under the concentration-time curve in lymph/area under the concentration-time curve in plasma x 100) was high for amoxicillin (97.6%), temocillin (89.4%), and clavulanic acid (90.8%) but was lower for ticarcillin (76.0%) and for ceftriaxone (67.3%). There was a direct correlation between plasma protein binding and percent penetration. Correction for plasma and tissue binding increased the percent penetration for all compounds, and figures approached 100%. The results presented demonstrate the use of this model to examine the relationships between plasma pharmacokinetics, protein binding, and distribution of antibiotics.
Critical influence of timing of administration of granulocyte colony-stimulating factor on antibacterial effect in experimental endocarditis due to Pseudomonas aeruginosa
Authors: Vignes S , Fantin B , Elbim C , Walker F , Gougerot-Pocidalo M A , Carbon C
Published: June 2012

The effect of human recombinant granulocyte colony-stimulating factor (hrG-CSF) in rabbits with aortic endocarditis due to Pseudomonas aeruginosa was investigated. hrG-CSF significantly increased the number of polymorphonuclear neutrophils in blood and in cardiac vegetations and the expression of the adhesin molecule CD11b on the surface of polymorphonuclear neutrophils compared with those of animals that had not received hrG-CSF. When treatment was started 72 h after bacterial challenge, hrG-CSF alone had no antibacterial effect and did not enhance the efficacy of ciprofloxacin when used in combination, even with the higher dosing regimen used (50 micrograms/kg of body weight subcutaneously every 12 h for 4 days), in terms of number of positive blood cultures, bacterial counts in vegetations, and survival. In contrast, when treatment was started 30 min prior to bacterial challenge, hrG-CSF (50 micrograms/kg injected every 12 h) decreased bacterial titers in vegetations 72 h later (6.5 +/- 0.9 versus 7.9 +/- 0.9 log10 CFU/g of vegetation for hrG-CSF and controls, respectively; P = prophylactic administration of hrG-CSF did not increase the antibacterial effect of ciprofloxacin. We concluded that the antibacterial effect of hrG-CSF in experimental endocarditis was related to the timing of its administration since hrG-CSF demonstrated a significant but transient antimicrobial effect only when treatment was initiated before bacterial challenge.
Analysis of ceftriaxone and ceftazidime distribution in cerebrospinal fluid of and cerebral extracellular space in awake rats by in vivo microdialysis
Authors: Granero L , Santiago M , Cano J , Machado A , Peris J E
Published: June 2012

In vivo microdialysis was used to estimate the extracellular concentrations of ceftazidime and ceftriaxone, two expanded-spectrum cephalosporins commonly used in the treatment of bacterial meningitis, in two brain regions (the right corpus striatum and the left lateral ventricle_ of awake, freely moving rats. Antibiotics were administered by constant intravenous infusion at 18 mg/h until steady-state levels were reached. Ceftriaxone levels measured at the steady state in the extracellular space of the corpus striatum (0.80 +/- 0.17 micrograms/ml) were statistically equivalent to those obtained in the cerebrospinal fluid of the lateral ventricle (0.71 +/- 0.15 micrograms/ml). The ratios of these levels in the brain to the steady-state levels in plasma were 0.5 +/- 0.1% for both regions. The postinfusion concentrations of ceftriaxone in the brain declined monoexponentially, with an elimination half-life similar to that obtained in plasma. However, the mean antibiotic concentration of ceftazidime in the striatum (2.2 +/- 0.4 micrograms/ml) was lower (P < 0.001) than that in the lateral ventricle (3.8 +/- 0.5% and 4.0 +/- 1.8%, respectively) were higher than those obtained with ceftriaxone. Moreover, the half-life of ceftazidime elimination from plasma was lower than that obtained in the two brain regions. It was concluded that the in vivo microdialysis technique yields useful data on antibiotic distribution in the extracellular space of the brain, that the distribution may not be homogeneous, and that the decay of postinfusion concentrations in the brain may be different from the decay of postinfusion concentrations in plasma.
Pharmacokinetics and bioavailability of zidovudine and its glucuronidated metabolite in patients with human immunodeficiency virus infection and hepatic disease (AIDS Clinical Trials Group protocol 062)
Authors: Moore K H , Raasch R H , Brouwer K L , Opheim K , Cheeseman S H , Eyster E , Lemon S M , van der Horst C M
Published: June 2012

The pharmacokinetics of zidovudine (ZDV) are established in patients with various stages of human immunodeficiency virus (HIV) disease. This study was conducted to determine the pharmacokinetic parameters of ZDV in patients with asymptomatic HIV infection and liver disease. HIV-infected volunteers with normal renal function were stratified according to the severity of liver disease (seven of eight were classified as mild). Each subject received a single intravenous dose of ZDV (120 mg) on the first day, followed by a single oral dose of ZDV (200 mg) on the second day. Blood samples were obtained over a 8-h collection interval, and concentrations of ZDV and its glucuronidated metabolite (GZDV) were determined by high-performance liquid chromatography. The following pharmacokinetic parameters were obtained after oral administration of ZDV to HIV-infected patients with mild hepatic disease; these values were compared with previously reported data in healthy volunteers. The area under the curve (AUC) (1,670 +/- 192 ng.h/ml), maximum concentration of drug in serum (1,751 +/- 180 ng/ml), and half-life (2.04 +/- 0.38 h) of ZDV were increased, while the apparent oral clearance (1.57 +/- 0.31 liter/h/kg of body weight) was decreased; AUC (7,685 +/- 1,222 ng.h/ml) and maximum concentration of drug in serum (5,220 +/- 1,350 ng/ml) of GZDV and the AUC ratio of GZDV to ZDV (2.79 +/- 0.43) after oral administration were decreased. ZDV absolute bioavailability was 0.75 +/- 0.15 in HIV-infected patients with hepatic disease. Although the ZDV apparent oral clearance was not impaired as significantly as in patients with biopsy-proven cirrhosis, our results suggest that ZDV, could accumulate in HIV-infected patients with mild hepatic disease because of impaired formation of GZDV. Patients with mild hepatic disease may require dosage adjustment to avoid accumulation of ZDV after extended therapy.