bluuebunny/crossref_metadata_2025 huggingface dataset:
Can penicillins and other beta-lactam antibiotics be used to treat tuberculosis?
Authors: Chambers H F , Moreau D , Yajko D , Miick C , Wagner C , Hackbarth C , Kocagöz S , Rosenberg E , Hadley W K , Nikaido H
Published: June 2012

An increase in the number of tuberculosis cases caused by multiple-drug-resistant strains of Mycobacterium tuberculosis has stimulated search for new antituberculous agents. Beta-lactam antibiotics, traditionally regarded as ineffective against tuberculosis, merit consideration. Four major penicillin-binding proteins (PBPs) with approximate molecular sizes of 94, 82, 52, and 37 kDa were detected by fluorography of [3H]penicillin-radiolabeled membrane proteins prepared from M. tuberculosis H37Ra. The presence of membrane-associated beta-lactamase precluded the use of membranes for assaying the binding affinities of beta-lactam antibiotics. Therefore, ampicillin affinity chromatography was used to purify these four PBPs from crude membranes in order to assay the binding affinities of beta-lactam antibiotics. Ampicillin, amoxicillin, and imipenem, beta-lactam antibiotics previously reported to be active in vitro against M. tuberculosis, bound to M. tuberculosis PBPs at therapeutically achievable concentrations. Binding of the 94-, 82-, and 52-kDa PBPs, but not the 37-kDa PBP, was associated with antibacterial activity, suggesting that these PBPs are the critical targets. Studies of mycobacterial cell wall permeability, which was assayed with a panel of reference cephalosporins and penicillins with different charge positivities, indicated that the rate of penetration of beta-lactam antibiotics to the target PBPs could not account for resistance. Resistance could be reversed with the beta-lactamase inhibitors clavulanate or sulbactam or could be circumvented by the use of a beta-lactamase-stable drug, imipenem, indicating that mycobacterial beta-lactamase, probably in conjunction with slow penetration, is a major determinant of M. tuberculosis resistance to beta-lactam antibiotics. These findings confirm in vitro data that M. tuberculosis is susceptible to some beta-lactam antibiotics. Further evaluation of these drugs for the treatment of tuberculosis in animal models and in clinical trials is warranted.
Genetic basis of macrolide resistance in Mycobacterium avium isolated from patients with disseminated disease
Authors: Nash K A , Inderlied C B
Published: June 2012

Clarithromycin (CLM) and azithromycin (AZM) are important agents in the treatment of disseminated Mycobacterium avium complex disease; however, monotherapy with these macrolides often leads to clinically significant resistance. The underlying resistance mechanism was investigated by comparing 23S rRNA gene sequences in the domain V region of 10 CLM-susceptible strains included in this study. The only differences in the domain V sequences associated with CLM resistance were at position 2274 of the complete M. avium 23S rRNA gene (GenBank accession no. X74494). All the CLM-susceptible strains had an A residue at this site, whereas seven of the eight CLM-resistant strains had either a C, G, or T. Four of these seven CLM-resistant strains emerged during monotherapy with CLM and two emerged during AZM monotherapy, showing that resistance selected by either macrolide was associated with mutation of the 23S rRNA gene. Thermodynamic analysis of secondary rRNA structure suggests that the observed mutations cause an alteration in free energy associated with rRNA folding, which may result in a localized conformation change in assembled ribosomes. Such a shift may be important in the resistance of ribosomes to the effects of macrolides. This study therefore establishes a link between mutations within the 23S rRNA gene and clinically significant macrolide resistance in M. avium and also identifies a possible molecular mechanism of resistance at the level of the ribosome.
Nonionic block copolymers potentiate activities of drugs for treatment of infections with Toxoplasma gondii
Authors: Araujo F G , Slifer T
Published: June 2012

We studied the interaction between drugs and the nonionic block copolymers CRL 8131 and CRL 8142 in the treatment of toxoplasmosis in murine models of the disease. Treatment of acute toxoplasmosis with copolymers alone caused slight prolongation of time to death but not survival. In contrast, significant survival occurred when mice were treated with either copolymer combined with doses of sulfadiazine, pyrimethamine, clindamycin, or atovaquone, which did not prevent mortality when used alone. Treatment with CRL 8131 plus sulfadiazine or pyrimethamine resulted in 50 or 40% survival, respectively. Treatment with the same copolymer plus a dose of clindamycin that protected 40% of the mice when used alone resulted in 100% survival. Treatment of toxoplasmic encephalitis with CRL 8131 plus an ineffective dose of atovaquone reduced the inflammation and numbers of Toxoplasma gondii cysts in the brain. Studies to investigate the drug-enhancing activity of CRL 8131 revealed that mice immunized with toxoplasma lysate plus copolymer had lymphocyte proliferation responses to T. gondii antigens significantly higher than those in mice immunized with lysate alone. Challenge of immunized mice with a lethal inoculum of T. gondii resulted in significant survival. Administration of CRL 8131 alone appeared to cause a down-regulation in the production of gamma interferon and up-regulation in the production of interleukin-2. No differences were noted in the production of tumor necrosis factor alpha between mice treated with CRL 8131 and controls.
Pharmacokinetics of intravenously administered isepamicin in men
Authors: Lin C C , Radwanski E , Korduba C , Cayen M , Affrime M
Published: June 2012

The pharmacokinetics of isepamicin, a broad-spectrum aminoglycoside antibiotic, were studied in men after intravenous administration. Three groups of six volunteers received isepamicin for 10 consecutive days by 0.5-h intravenous infusions at respective dosages of 7.5 mg/kg of body weight once daily, 7.5 mg/kg twice daily, and 15 mg/kg once daily. Levels of isepamicin in plasma and urine were determined by a specific high-performance liquid chromatography method. For all three groups, steady-state concentrations of the drug in plasma were attained with the first dose. The area under the concentration-time curve for plasma and urinary drug excretion were dose proportional. A half-life ranging from 2.0 to 2.5 h was independent of the dosage regimen. Isepamicin excreted in urine over 24 h accounted for about 100% of the dose. The results show that the pharmacokinetics of isepamicin are linear with these dosage regimens. The drug does not accumulate upon multiple dosing, undergoes no detectable biotransformation, and is cleared solely by urinary excretion.
Colonization and infection with Enterococcus faecalis in intensive care units: the role of antimicrobial agents
Authors: Bonten M J , Gaillard C A , van Tiel F H , van der Geest S , Stobberingh E E
Published: June 2012

We studied the influences of antimicrobial agents on the colonization of the respiratory tract and infection with Enterococcus faecalis in intensive care unit (ICU) patients receiving mechanical respiration for at least 3 days. In a matched-cohort analysis, patients receiving topical antimicrobial prophylaxis (TAP) of the oropharynx and stomach with antimicrobial agents not treating E. faecalis were compared with patients not receiving TAP. Patients were matched with controls on the basis of their duration in the ICU, their use of systemic antibiotics treating and not treating E. faecalis, the administration of TAP, their APACHE II score, and surgical procedures they had undergone. In all, 276 patients were analyzed. The colonization of the oropharynx and/or trachea by E. faecalis at admission was demonstrated for 43 patients (16%). Twenty patients (9%) acquired tracheal colonization and 91 patients (40%) acquired oropharyngeal colonization with E. faecalis. In the matched-cohort analysis, 43 patients receiving TAP were matched in two controls each. TAP patients more frequently acquired tracheal colonization (15 of 43 versus 2 of 86 patients, P < 0.00001) and infections with E. faecalis (6 of 43 versus 1 of 86 patients, P < 0.01). The use of topical antibiotics and treating E. faecalis increased the risk for colonization and infection with E. faecalis.
Strategies for control of zidovudine concentrations in serum
Authors: Noormohamed S E , Henry W K , Rhame F S , Balfour H H , Fletcher C V
Published: June 2012

There are several clinical scenarios in which knowledge of zidovudine disposition may be important. This study evaluated the clinical utility of pharmacokinetic parameters for zidovudine derived from sparse serum concentration data obtained in an outpatient setting. Twelve human immunodeficiency virus-infected participants had two serum zidovudine concentrations determinations obtained on two different clinic visits, 2 to 38 days apart. Zidovudine concentrations were measured by radioimmunoassay. A one-compartment oral absorption model was used to describe zidovudine disposition. Three different approaches were used to estimate pharmacokinetic parameters: Bayesian estimation with one or two concentrations and least squares with one concentration. The ability of these parameters to predict concentrations measured during the second clinic visit was assessed by calculation of precision and bias and compared with predictions using standard fixed or weight-adjusted parameters. Estimated pharmacokinetic parameters for zidovudine were consistent with literature values; there was no statistically significant difference among the parameters calculated with the three estimation strategies. Absorptive phase concentrations were poorly predicted by all methods (mean percent bias, 157 to 249%; mean percent precision, 389 to 537%). Predictive ability for concentrations obtained in the elimination phase was strikingly improved: mean percent bias, -17 to 70%; mean percent precision, 40 to 95%. Bayesian and least-squares estimated parameters were statistically better than fixed-parameter values for predicting concentrations in the elimination phase. These observations provide a modeling framework to determine pharmacokinetic disposition of zidovudine in an individual, screen for the existence of a drug interaction, and conduct concentration-controlled clinical trials.
Postantibiotic effect of clarithromycin alone and combined with ethambutol against Mycobacterium avium complex
Authors: Ellis L C , Benson C A , Koenig G I , Trenholme G M
Published: June 2012

The postantibiotic effect (PAE) of clarithromycin alone and in combination with ethambutol was determined for two clinical blood isolates of Mycobacterium avium complex. An average PAE, ranging from 5.5 to 18.0 h, was noted for each isolate at each clarithromycin concentration except when isolate B was exposed to clarithromycin at the MIC. The addition of ethambutol did not enhance the PAE observed with clarithromycin alone. The clinical implications of the PAE of clarithromycin for M. avium complex remain to be determined.
Activity of lipopolysaccharide-binding protein-bactericidal/permeability-increasing protein fusion peptide in an experimental model of Pseudomonas sepsis
Authors: Opal S M , Palardy J E , Jhung J W , Donsky C , Romulo R L , Parejo N , Marra M N
Published: June 2012

A chimeric protein consisting of the N-terminal domain of lipopolysaccharide-binding protein and the C-terminal domain of bactericidal/permeability-increasing protein demonstrated a dose-dependent survival benefit (P = 0.001) and reduced endotoxin levels (P < 0.01) in neutropenic rats with Pseudomonas aeruginosa sepsis. This lipopolysaccharide-binding protein-bactericidal/ permeability-increasing peptide has favorable pharmacokinetics and antiendotoxin properties which may be of value for human sepsis.
Enhanced activity of the combination of penicillin G and gentamicin against penicillin-resistant viridans group streptococci
Authors: Cercenado E , Díaz M D , Sánchez-Carrillo C , Vicente T , Bernaldo de Quirós J C
Published: June 2012

We evaluated the effects of the combination of penicillin G and gentamicin against 10 penicillin-resistant bacteremic isolates of viridans group streptococci for which the MICs of penicillin were 4 to 64 micrograms/ml. In time-kill studies, the combination resulted in more killing of eight isolates for which the MICs of penicillin were from 8 to 64 micrograms/ml than any of the antimicrobial agents tested alone. In general, clearly enhanced antimicrobial activity was observed with the combination.
Pharmacokinetics of stavudine (2',3'-didehydro-3'-deoxythymidine) in the neonatal macaque (Macaca nemestrina)
Authors: Keller R D , Nosbisch C , Unadkat J D
Published: June 2012

Our objective was to determine whether age effects the pharmacokinetics of stavudine (2',3'-didehydro-3'-deoxythymidine) in the neonatal pig-tailed macaque (Macaca nemestrina). The drug (5 mg/kg of body weight) was administered serially as a single intravenous bolus to the same four macaques at the ages of < 1 week, 1 month, and 4 months. Plasma clearance at < 1 week of age was significantly lower (P < 0.05) than the corresponding values at 1 month and 4 months. Our data indicate that the pharmacokinetics of stavudine change significantly with age in M. nemestrina.
Intranasal pirodavir (R77,975) treatment of rhinovirus colds
Authors: Hayden F G , Hipskind G J , Woerner D H , Eisen G F , Janssens M , Janssen P A , Andries K
Published: June 2012

A randomized, double-blind, placebo-controlled trial assessed the therapeutic efficacy of intranasal pirodavir in naturally occurring rhinovirus colds. Adults with symptoms of < or = 2 days' duration were randomly assigned to intranasal sprays of pirodavir (2 mg per treatment) or placebo six times daily for 5 days. In people with laboratory-documented rhinovirus colds (53 in the pirodavir group, 55 in the placebo group), no significant differences in the resolution of respiratory symptoms were apparent between the groups. The median duration of illness was 7 days in each group. Similarly, scores for individual symptoms found no differences in favor of pirodavir during or after treatment. In contrast, reduced frequencies of rhinovirus shedding were observed in the pirodavir group on day 3 (70 versus 23%; P < 0.001) and day 5 (38 versus 12%; P = 0.002) but not after the cessation of treatment, on day 7 (19 versus 21%). No pirodavir-resistant viruses were recovered from treated individuals. The pirodavir group had higher rates of nasal dryness, blood in mucus, or unpleasant taste on several study days. In summary, intranasal sprays of pirodavir were associated with significant antiviral effects but no clinical benefit in treating naturally occurring rhinovirus colds.
Antimicrobial activities of amphiphilic peptides covalently bonded to a water-insoluble resin
Authors: Haynie S L , Crum G A , Doele B A
Published: June 2012

A series of polymer-bound antimicrobial peptides was prepared, and the peptides were tested for their antimicrobial activities. The immobilized peptides were prepared by a strategy that used solid-phase peptide synthesis that linked the carboxy-terminal amino acid with an ethylenediamine-modified polyamide resin (PepsynK). The acid-stable, permanent amide bond between the support and the nascent peptide renders the peptide resistant to cleavage from the support during the final acid-catalyzed deprotection step in the synthesis. Select immobilized peptides containing amino acid sequences that ranged from the naturally occurring magainin to simpler synthetic sequences with idealized secondary structures were excellent antimicrobial agents against several organisms. The immobilized peptides typically reduced the number of viable cells by > or = 5 log units. We show that the reduction in cell numbers cannot be explained by the action of a soluble component. We observed no leached or hydrolyzed peptide from the resin, nor did we observe any antimicrobial activity in soluble extracts from the immobilized peptide. The immobilized peptides were washed and reused for repeated microbial contact and killing. These results suggest that the surface actions by magainins and structurally related antimicrobial peptides are sufficient for their lethal activities.
Development of test panel of beta-lactamases expressed in a common Escherichia coli host background for evaluation of new beta-lactam antibiotics
Authors: Bradford P A , Sanders C C
Published: June 2012

A test panel of 35 different beta-lactamases expressed in a common Escherichia coli host was created to compare the effect that each beta-lactamase had on susceptibility to various beta-lactam antibiotics. A comparison of the MICs obtained with this panel generally reflected differences in the substrate profiles of the various beta-lactamases examined. In addition, several strains of the panel were subjected to selection with porin-specific bacteriophages to obtain mutants lacking either the OmpC or OmpF porin protein. A mutation in either OmpC or OmpF did change the susceptibilities of certain strains expressing beta-lactamase to certain beta-lactam antibiotics. However, the loss of a single porin did not predictably alter susceptibility to any given beta-lactam drug. This panel of strains producing various beta-lactamases was found to be a useful tool for comparing the effects of different beta-lactamases and outer membrane permeability upon susceptibility to beta-lactam drugs.
Comparative and collaborative evaluation of standardization of antifungal susceptibility testing for filamentous fungi
Authors: Espinel-Ingroff A , Dawson K , Pfaller M , Anaissie E , Breslin B , Dixon D , Fothergill A , Paetznick V , Peter J , Rinaldi M
Published: June 2012

The purpose of the study was to evaluate the interlaboratory agreement of broth dilution susceptibility methods for five species of conidium-forming (size range, 2 to 7 microns) filamentous fungi. The methods used included both macro- and microdilution methods that were adaptations of the proposed reference method of the National Committee for Clinical Laboratory Standards for yeasts (m27-P). The MICs of amphotericin B, fluconazole, itraconazole, miconazole, and ketoconazole were determined in six centers by both macro- and microdilution tests for 25 isolates of Aspergillus flavus, Aspergillus fumigatus, Pseudallescheria boydii, Rhizopus arrhizus, and Sporothrix schenckii. All isolates produced clearly detectable growth within 1 to 4 days at 35 degrees C in the RPMI 1640 medium. Colony counts of 0.4 x 10(6) to 3.3 x 10(6) CFU/ml (mean, 1.4 x 10(6) CFU/ml) were demonstrated in 90% of the 148 inoculum preparations. Overall, good intralaboratory agreement was demonstrated with amphotericin B, fluconazole, and ketoconazole MICs (90 to 97%). The agreement was lower with itraconazole MICs (59 to 79% median). Interlaboratory reproducibility demonstrated similar results: 90 to 100% agreement with amphotericin B, fluconazole, miconazole, and ketoconazole MICs and 59 to 91% with itraconazole MICs. Among the species tested, the MICs for S. schenckii showed the highest variability. The results of the study imply that it may be possible to develop a reference method for antifungal susceptibility testing of filamentous fungi.
Antiviral properties of aminodiol inhibitors against human immunodeficiency virus and protease
Authors: Bechtold C M , Patick A K , Alam M , Greytok J , Tino J A , Chen P , Gordon E , Ahmad S , Barrish J C , Zahler R
Published: June 2012

A series of aminodiol inhibitors of human immunodeficiency virus type 1 (HIV-1) protease were identified by using an in vitro peptide cleavage assay. BMS 182,193, BMS 186,318, and BMS 187,071 protected cells against HIV-1, HIV-2, and simian immunodeficiency virus infections, with 50% effective doses ranging from 0.05 to 0.33 microM, while having no inhibitory effect on cells infected with unrelated viruses. These compounds were also effective in inhibiting p24 production in peripheral blood mononuclear cells infected with HIV-1 IIIB and against the zidovudine-resistant HIV-1 strain A018C. Time-of-addition studies indicated that BMS 182,193 could be added as late as 27 h after infection and still retain its antiviral activity. To directly show that the activity of these compounds in culture was due to inhibition of proteolytic cleavage, the levels of HIV-1 gag processing in chronically infected cells were monitored by Western blot (immunoblot) analysis. All compounds blocked the processing of p55 in a dose-dependent manner, with 50% effective doses of 0.4 to 2.4 microM. To examine the reversibility of BMS 186,318, chronically infected CEM-SS cells were treated with drug and virions purified from the culture medium. Incubation of HIV-1 particles in drug-free medium indicated that inhibition of p55 proteolysis was slowly reversible. The potent inhibition of HIV-1 during both acute and chronic infections indicates that these aminodiol compounds are effective anti-HIV-1 compounds.
Activity of carbapenem BMS-181139 against Pseudomonas aeruginosa is not dependent on porin protein D2
Authors: Fung-Tomc J C , Gradelski E , Kolek B , Minassian B , Pucci M , Kessler R E , Bonner D P
Published: June 2012

The broad antipseudomonal spectrum of the carbapenem BMS-181139 includes clinical strains and laboratory mutants of Pseudomonas aeruginosa that are resistant to imipenem. Unlike other known carbapenems (meropenem, panipenem, biapenem, and BO-2727), which have reduced activity against imipenem-resistant strains of P. aeruginosa, BMS-181139 was equally active against imipenem-susceptible (D2-sufficient) and imipenem-resistant (D2-deficient) strains. Conversely, imipenem and meropenem activities were the same against the susceptible parental strains and their BMS-181139-resistant mutants. Whereas basic amino acids antagonized the antipseudomonal activities of imipenem and meropenem, they had no effect on the activity of BMS-181139. These results suggest that the uptake of BMS-181139 into pseudomonal cells occurs by a non-D2 pathway. Compared with imipenem and meropenem, BMS-181139 may have a slightly higher affinity for penicillin-binding protein 2 (PBP-2) of P. aeruginosa. The rates of resistance development to imipenem, meropenem, and BMS-181139 in P. aeruginosa strains were similar; resistance occurred at frequencies of approximately 10(-7) to 10(-8). Resistance to BMS-181139 in P. aeruginosa is presumed to be caused by its diminished permeability since no change in their penicillin-binding protein affinities or beta-lactamase levels could be detected. In summary, BMS-181139 is a new carbapenem which differs from other known carbapenems in its lack of cross-resistance with imipenem. This difference could be explained by the permeation of BMS-181139 through a non-D2 channel, compared to the preferential uptake of other carbapenems by the D2 porin.
Structure-activity relationships of carbapenems that determine their dependence on porin protein D2 for activity against Pseudomonas aeruginosa
Authors: Fung-Tomc J C , Huczko E , Banville J , Ménard M , Kolek B , Gradelski E , Kessler R E , Bonner D P
Published: June 2012

A number of carbapenem derivatives were examined to determine the structure-activity relationships required for dependence on porin protein D2 for activity against Pseudomonas aeruginosa. As suggested by J. Trias and H. Nikaido (Antimicrob. Agents Chemother. 34:52-57, 1990), carbapenem derivatives, such as imipenem and meropenem, containing a sole basic group at position 2 of the molecule utilize the D2 channel for permeation through the outer membrane of pseudomonads; they are more active against D2-sufficient strains of P. aeruginosa. Our results indicated that carbapenems with a basic group at position 1 or 6 of the molecule did not depend on the D2 channel for activity; i.e. they were equally active against D2-sufficient and D2-deficient pseudomonal strains. However, addition of a basic group at position 1 or 6 of a carbapenem derivative already containing a basic group at position 2 resulted in its lack of dependency on the D2 pathway. Comparison between meropenem and its 1-guanidinoethyl derivative, BMY 45047, indicated that they differed in their dependence on D2; while meropenem required the D2 channel for uptake, BMY 45047 activity was independent of D2. Meropenem and BMY 45047 had similar affinities for the penicillin-binding proteins of P. aeruginosa. However, BMY 45047 and meropenem differed in the morphological changes that they induced in pseudomonal cells. While meropenem induced filamentation, BMY 45047 induced filaments only in BMS-181139-resistant mutants and not in imipenem-resistant mutants or in carbapenem-susceptible P. aeruginosa strains. These results suggested that in Mueller-Hinton medium the uptake of BMY 45047 through the non-D2 pathway is more rapid than that of meropenem through the D2 porin. In summary, the presence of a basic group at position 2 of a carbapenem is important for its preferential uptake by the D2 channel. However the addition of a basic group at position 1 or 6 of a carbapenem already containing a basic group at position 2 dissociates its necessity for porin protein D2 for activity.
Enhancement of antibiotic susceptibility and suppression of Mycobacterium avium complex growth by poloxamer 331
Authors: Hunter R L , Jagannath C , Tinkley A , Behling C A , Nolte F
Published: June 2012

The resistance of Mycobacterium avium complex (MAC) to antibiotics is thought to be enhanced by its outer glycolipid layer, which protects the organisms from antibiotics and host defense mechanisms. We hypothesized that surfactants which disrupt the lipid barrier might be of therapeutic value. We evaluated the ability of 10 poloxamer surfactants to inhibit the growth of MAC organisms and to potentiate antimycobacterial drug activity in broth culture using a radiometric assay. Very large, small, or hydrophilic poloxamers had little or no effect. However, certain hydrophobic poloxamers, especially P331, retarded the growth of most isolates of MAC and produced a synergistic effect with rifampin. The MIC of rifampin required to inhibit the growth of MAC was reduced from a mean of 14.6 micrograms/ml (range, 4 to > 32 micrograms/ml) to 1.4 micrograms/ml (range, < 1.125 to 4 micrograms/ml) by 1.0 mg of P331 per ml (P < 0.01). Enhancement of antibiotic susceptibility was observed with concentrations of poloxamer as low as 10 micrograms/ml. These studies suggest that P331 might be useful in increasing the effectiveness of antibiotic therapy of MAC infections.
Cloning of multidrug resistance gene pqrA from Proteus vulgaris
Authors: Ishida H , Fuziwara H , Kaibori Y , Horiuchi T , Sato K , Osada Y
Published: June 2012

The multiple antibiotic resistance gene pqrA was cloned from the chromosomal DNA of a clinical isolate of Proteus vulgaris 881051 into Escherichia coli KY2563. The MICs of quinolones tetracycline, cephalosporin, and chloramphenicol for transformant strain DNS7020 were from 8 to 32 times higher than those for the parent strain, KY2563. The level of expression of outer membrane protein F (OmpF) by DNS7020 was lower than that of KY2563 but not as low as that of an OmpF-deficient control strain. The 1.4-kb fragment containing the pqrA gene had an open reading frame encoding a polypeptide of 122 amino acid residues with a molecular weight of about 14,000, which was consistent with the experimental value identified by the Maxicell method. The putative PqrA polypeptide showed significant amino acid sequence similarity to the E. coli proteins SoxS and MarA. These polypeptides are strongly conserved in predicted helix-turn-helix DNA binding domains. The MarA protein, which is responsible for multiple antibiotic resistance in E. coli, also decreases OmpF expression. Moreover, the SoxS protein, which is characterized as a superoxide response regulon of E. coli, has also been shown to increase resistance to many structurally unrelated antibiotics. The soxS gene increases superoxide dismutase levels in addition to decreasing OmpF expression. The expression level of superoxide dismutase with DNS7020 was about 1.5 times higher than that with KY2563. These findings suggest that the pqrA gene in P. vulgaris confers multidrug resistance in a way similar to that of the soxS and marA genes in E. coli.
Tobramycin uptake in Escherichia coli membrane vesicles
Authors: Leviton I M , Fraimow H S , Carrasco N , Dougherty T J , Miller M H
Published: June 2012

The uptake of tobramycin was measured in Escherichia coli membrane vesicles prepared in KMES [K(+)-2-(N-morpholino)ethanesulfonic acid] buffer at pH 6.6. Uptake occurred in vesicles energized with ascorbic acid and phenazine methosulfate, in which the electrical potential (delta psi) was -120 mV, but not in vesicles energized with D-lactate (delta psi = -95 mV). The addition of nigericin to vesicles energized with D-lactate did not induce tobramycin uptake despite an increase in delta psi to -110 mV. However, when delta psi was increased or decreased by the addition of nigericin or valinomycin, respectively, uptake in vesicles energized with ascorbic acid and phenazine methosulfate was stimulated or inhibited, respectively, confirming studies with whole cells showing that uptake of aminoglycosides is gated by delta psi rather than by proton motive force (delta microH+) or delta pH. N-ethylmaleimide prevented uptake, suggesting that the aminoglycoside transporter is a cytoplasmic membrane protein with accessible sulfhydryl groups. The observation that uptake is gated in vesicles as well as in whole cells suggested that diffusion occurs through a voltage-gated channel. In vesicles preloaded with tobramycin, no efflux occurred after the addition of the protonophore carbonyl cyanide m-chlorophenylhydrazone. In susceptible cells, aminoglycosides themselves decreased the magnitude of delta psi. We propose a mechanism of aminoglycoside-induced killing in which aminoglycosides themselves close the voltage-gated channel by decreasing the magnitude of delta psi. Channel closure causes aminoglycosides accumulated prior to the fall in delta psi to be trapped, which in turn causes irreversible uptake and subsequent bactericidal effects.
Development of multiple-antibiotic-resistant (Mar) mutants of Pseudomonas aeruginosa after serial exposure to fluoroquinolones
Authors: Zhanel G G , Karlowsky J A , Saunders M H , Davidson R J , Hoban D J , Hancock R E , McLean I , Nicolle L E
Published: June 2012

Laboratory-derived fluoroquinolone-resistant mutants were created by serially passaging wild-type Pseudomonas aeruginosa on fluoroquinolone-containing agar to obtain high-level fluoroquinolone resistance (e.g., ciprofloxacin MIC of 1,024 micrograms/ml). With increases of 4- to 32-fold in MICs of fluoroquinolones, these organisms demonstrated (relative to wild-type) normal morphology, resistance to fluoroquinolones only, no change in fluoroquinolone uptake, and no change in lipopolysaccharide profiles or outer membrane protein profiles. Complementation with wild-type Escherichia coli gyrA restored fluoroquinolone susceptibility, suggesting that these were gyrA mutants. After 4- to 32-fold increases in fluoroquinolone MICs (with continued passage on fluoroquinolone-containing agar) isolates demonstrated altered morphology, a multiple-antibiotic-resistant (Mar) phenotype (including cross-resistance to beta-lactams, chloramphenicol, and tetracycline), reduced fluoroquinolone uptake and altered outer membrane proteins (reductions in the 25- and 38-kDa bands as well as several bands in the 43- to 66-kDa region). Complementation with wild-type E. coli gyrA partially reduced the level of fluoroquinolone resistance by approximately 8- to 32-fold, suggesting that these mutants displayed both gyrA and non-gyrA mutations.
Effect of aerobic and anaerobic environments on antistaphylococcal activities of five fluoroquinolones
Authors: Zabinski R A , Walker K J , Larsson A J , Moody J A , Kaatz G W , Rotschafer J C
Published: June 2012

A previously established in vitro pharmacodynamic system was used to evaluate the antistaphylococcal activities of five fluoroquinolones under both aerobic and anaerobic conditions. Staphylococcus aureus ATCC 29213 was exposed to a 5-micrograms/ml concentration of each of the following fluoroquinolones: ciprofloxacin, ofloxacin, temafloxacin, sparfloxacin, and clinafloxacin. Terminal elimination half-lives of 4, 6, 8, 8, and 13 h were simulated for the respective drugs. Each fluoroquinolone was bactericidal under both aerobic and anaerobic conditions. However, the bactericidal activity of each fluoroquinolone was delayed by anaerobiosis. This difference in fluoroquinolone activity under aerobic and anaerobic conditions could not be attributed to any particular parameter or physiochemical property but was most likely caused by a combination of factors (e.g., variations in hydrophobicity, intracellular pH, antibiotic concentration, and structure-activity relationships). Fluoroquinolone uptake studies were also performed to investigate the possibility of active, energy-dependent transport mechanisms in S. aureus ATCC 29213. Uptake studies indicated that active efflux does occur in S. aureus ATCC 29213.
Relationship between quinolone use and emergence of ciprofloxacin-resistant Escherichia coli in bloodstream infections
Authors: Peña C , Albareda J M , Pallares R , Pujol M , Tubau F , Ariza J
Published: June 2012

From 1988 to 1992, 27 of 855 cases of Escherichia coli bacteremia in nonneutropenic adult patients observed at our hospital were due to ciprofloxacin-resistant (CIPRO-R) strains. Eighteen episodes (67%) were community acquired, and nine (33%) were nosocomially acquired. Overall, the rates of E. coli bacteremia caused by CIPRO-R strains increased steadily from 0% in 1988 to 7.5% in 1992 (P < 0.01). There was a statistically significant correlation between the incidence of CIPRO-R E. coli bacteremia and the upward trend in fluoroquinolone (norfloxacin and ciprofloxacin) use in the community (r = 0.974; P = 0.005) as well as in the hospital (r = 0.975; P = 0.005). When we compared the 27 case patients with 54 simultaneous control patients who had ciprofloxacin-susceptible E. coli bacteremia, the case patients more frequently had chronic underlying diseases (71 versus 37%; P = 0.004), urinary tract infection (74 versus 50%; P = 0.03), prior surgery (22 versus 6%; P = 0.02), and prior fluoroquinolone use (63 versus 4%; P < 0.001). A logistic regression analysis identified prior quinolone use as the only independent risk factor for CIPRO-R E. coli bacteremia. In conclusion, our study shows a significant correlation between ciprofloxacin resistance and fluoroquinolone use and indicates that prior fluoroquinolone use seems to be the most important risk factor for CIPRO-R E. coli bacteremia.
Susceptibilities of fluoroquinolone-resistant strains of Campylobacter jejuni to 11 oral antimicrobial agents
Authors: Gomez-Garces J L , Cogollos R , Alos J L
Published: June 2012

The resistance of Campylobacter jejuni strains to the fluoroquinolones is increasingly frequent, and in our area it reaches nearly 50%. We studied the susceptibilities of 60 of these strains to 11 oral antibiotics. All strains except one were susceptible to the macrolides tested, with azithromycin being the most active agent tested. Of the rest of the antibiotics studied, amoxicillin-clavulanic acid, clindamycin, and fosfomycin displayed good in vitro activities. Knowledge of the susceptibilities of these microorganisms to a varied group of oral agents is necessary in view of the appearance of multiresistant strains, such as those included in our series.
Effect of inflammation on intraocular penetration of intravenous ofloxacin in albino rabbits
Authors: Gatti G , Panozzo G
Published: June 2012

The effect of inflammation on the intraocular penetration of ofloxacin was studied in 20 albino rabbits (New Zealand White). Inflammation was induced in the left eye by inoculation of a suspension of 10(9) CFU of heat-killed Staphyloccus epidermidis per 0.1 ml of saline solution (0.9%) in the midvitreous cavity. The other eye was kept as a control. Twenty-four hours following inoculation, ofloxacin was administered in the marginal ear vein at a dose of 15 mg/kg over 20 min with an infusion pump. Animals were sacrificed at different times up to 24 h following drug administration. Ofloxacin levels were determined in aqueous humor, vitreous humor, and serum by a bioassay. Inflammation was scored on the basis of perilimbal and corneal reactions and vitreoretinal statuses. Inflammation had a relevant effect on intraocular penetration of ofloxacin, with levels in the ocular fluids of the inflamed eye markedly exceeding the ones of the control eye. In the uninflamed eye, the levels were rapidly decaying below assay sensitivity and were no longer detectable at approximately 5 h following drug administration while they were still detectable in both ocular fluids of the inflamed eye at 24 h. Ofloxacin levels in the ocular fluids of the inflamed eye were superior to the MIC for several of the bacteria which commonly cause endophthalmitis, including Staphylococcus epidermidis, Staphylococcus aureus, most members of the family Enterobacteriaceae, Haemophilus influenzae, and strains of Pseudomonas aeruginosa.
Comparison of effects of suture and cyanoacrylate tissue adhesive on bacterial counts in contaminated lacerations
Authors: Howell J M , Bresnahan K A , Stair T O , Dhindsa H S , Edwards B A
Published: June 2012

We studied the effects of closing lacerations with suture or cyanoacrylate tissue adhesive on staphylococcal counts in inoculated guinea pig lacerations. Wounds closed with adhesive alone had lower counts than wounds containing suture material (P < 0.05). The results of a time-kill study were consistent with a bacteriostatic adhesive effect of the adhesive against Staphylococcus aureus.
Low-level resistance to the cephalosporin 3'-quinolone ester Ro 23-9424 in Escherichia coli
Authors: Chapman J S , Bertasso A , Cummings L M , Georgopapadakou N H
Published: June 2012

Four spontaneous, single-step mutants of Escherichia coli K-12 resistant to low levels of the cephalosporin 3'-quinolone ester Ro 23-9424 were isolated at a frequency of 10(-10) to 10(-11) mutants per CFU plated. The mutants were cross-resistant to both cephalosporin (cefotaxime) and quinolone (fleroxacin) components. Accordingly, they had altered porins and replicative DNA biosynthesis resistant to fleroxacin. There was no increase in beta-lactamase activity when tested with nitrocephin, and the penicillin-binding protein profiles were normal.
Quinolone antibiotics in therapy of experimental pneumococcal meningitis in rabbits
Authors: Nau R , Schmidt T , Kaye K , Froula J L , Täuber M G
Published: June 2012

Using a rabbit model of pneumococcal meningitis, we compared the pharmacokinetics and bactericidal activities in cerebrospinal fluid (CSF) of older (ciprofloxacin, ofloxacin) and newer (levofloxacin, temafloxacin, CP-116,517, and Win 57273) quinolones with those of the beta-lactam ceftriaxone. All quinolones penetrated into the inflamed CSF better than ceftriaxone, and the speed of entry into CSF was closely related to their degrees of lipophilicity. At a dose of 10 mg/kg.h, which in the case of the quinolones already in use in clinical practice produced concentrations attainable in the sera and CSF of humans, ciprofloxacin had no antipneumococcal activity (delta log10 CFU/ml.h, +0.20 +/- 0.14). Ofloxacin (delta log10 CFU/ml.h, -0.13 +/- 0.12), temafloxacin (delta log10 CFU/ml.h, -0.19 +/- 0.18), and levofloxacin (delta log10 CFU/ml.h, -0.24 +/- 0.16) showed slow bactericidal activity (not significantly different from each other), while CP-116,517 (delta log10 CFU/ml.h, -0.59 +/- 0.21) and Win 57273 (delta log10 CFU/ml.h, -0.72 +/- 0.20) showed increased bactericidal activities in CSF that was comparable to that of ceftriaxone at 10 mg/kg.h (delta log10 CFU/ml.h, -0.80 +/- 0.17). These improved in vivo activities of the newer quinolones reflected their increased in vitro activities. All quinolones and ceftriaxone showed positive correlations between bactericidal rates in CSF and concentrations in CSF relative to their MBCs. Only when this ratio exceeded 10 did the antibiotics exhibit rapid bactericidal activities in CSF. In conclusion, in experimental pneumococcal meningitis the activities of new quinolones with improved antipneumococcal activities were comparable to that of ceftriaxone.
Safety, tolerance, and pharmacokinetics of atevirdine mesylate (U-87201E) in asymptomatic human immunodeficiency virus-infected patients
Authors: Been-Tiktak A M , Vrehen H M , Schneider M M , van der Feltz M , Branger T , Ward P , Cox S R , Harry J D , Borleffs J C
Published: June 2012

Atevirdine mesylate (U-87201E) is a new nonnucleoside (bisheteroarylpiperazine) inhibitor of human immunodeficiency virus type 1 reverse transcriptase. In a double-blind, escalating single-dose study the safety, tolerance, and pharmacokinetics of atevirdine mesylate were investigated in 24 asymptomatic human immunodeficiency virus-seropositive male patients. Each patient received one single oral dose of atevirdine mesylate and placebo separated by an interval of 1 to 3 weeks. For each dose level (400, 800, 1,200, and 1,600 mg) six patients received drug and placebo on separate occasions. Blood samples were collected before dosing and at intervals afterward for safety evaluation and estimation of atevirdine and metabolite levels. The concentrations of atevirdine and its principal metabolite (U-89255) in serum were determined by high-performance liquid chromatography. The results of the study showed that atevirdine mesylate is well tolerated at all dose levels. No clinically significant effects on vital signs, electrocardiograms, or laboratory tests were observed. Occasional headache and nausea were reported both in the drug group and in the placebo group. The times to peak values were relatively short (0.5 to 1.0 h), suggesting a rapid absorption. The maximum concentrations of drug in serum were 1.4 microM (400 mg), 4.2 microM (800 mg), 7.3 microM (1,200 mg), and 5.8 microM (1,600 mg). The values of the pharmacokinetic parameters for atevirdine were found to have relatively large intersubject variabilities, and consequently, the study had little power to detect dose-dependent changes in the values of the pharmacokinetic parameters. The oral clearance of atevirdine tended to increase by 90% as the atevirdine mesylate doses increased from 400 to 1,600 mg, but this change in oral clearance was not statistically significant. The values of the pharmacokinetic parameters determined in the study were similar to those found in a previous single-dose study in healthy volunteers.
Effect of cefodizime and ceftriaxone on phagocytic function in patients with severe infections
Authors: Wenisch C , Parschalk B , Hasenhündl M , Wiesinger E , Graninger W
Published: June 2012

Thirty patients with severe bacterial infections were treated with 50 mg of cefodizime per kg of body weight once daily or 50 mg of ceftriaxone per kg once daily for 10 +/- 3 days. The effect of cefodizime and ceftriaxone on the phagocytic capacity and generation of reactive oxygen intermediates after phagocytosis by granulocytes was assessed prior to, during, and after therapy. Flow cytometry was used to study phagocytic capacity by measuring the uptake of fluorescein-labeled bacteria. The generation of reactive oxygen intermediates after phagocytosis was estimated by the quantification of the intracellular conversion of dihydrorhodamine 123 to rhodamine 123. Prior to therapy, patients in both groups exhibited a decreased capacity to phagocytize Escherichia coli and subsequently to generate reactive oxygen intermediates. Granulocyte function increased after the initiation of therapy and normalized within 7 days for the ceftriaxone-treated patients and within 3 days for the cefodizime group (P < 0.05). In the cefodizime group, an enhancement of phagocytic capacity was observed 14 days after the initiation of therapy (P < 0.05). Prior to therapy, phagocytic capacity was significantly correlated with the generation of reactive oxygen products (r = 0.674 and P < 0.005).
Roles of divalent cations and pH in mechanism of action of nitroxoline against Escherichia coli strains
Authors: Pelletier C , Prognon P , Bourlioux P
Published: June 2012

The antibacterial activity of nitroxoline (NIT), an antibiotic used in the treatment of acute or recurrent urinary tract infections caused by Escherichia coli, is decreased in the presence of Mg2+ and Mn2+ but not Ca2+. In order to elucidate the interaction between this drug and the divalent cations, spectrophotometric studies based on the natural absorption of the nitroxoline moiety were conducted. In the presence of the divalent metal ions, a shift in the NIT A448 suggested the formation of drug-ion complexes, for which the stability followed the order Mn2+ > Mg2+ > Ca2+. A clear correlation was found between the chelating property and antibacterial activity of NIT; both were pH dependent. A convenient colorimetric method for the determination of NIT uptake by bacterial cells was also developed. Uptake was energy independent and showed biphasic kinetics: a rapid association with cells and then a slower increase in cell-associated NIT which reached a plateau. NIT uptake was reduced in the presence of magnesium. The implications of metal ion complexation and pH on the clinical efficacy of NIT are discussed.
Bioluminescence method to evaluate antimicrobial agents against Mycobacterium avium
Authors: Cooksey R C , Morlock G P , Beggs M , Crawford J T
Published: June 2012

Plasmid pLUC10, carrying the firefly luciferase gene, was transformed by electroporation into Mycobacterium avium A5. Bioluminescence production by strain A5(pLUC10), as measured in a microdilution plate luminometer, was approximately 1 relative light unit per 2 x 10(6) viable bacilli, whereas it was 0.0005 relative light unit for an equal number of parental cells. The susceptibility of strain A5(pLUC10) to eight concentrations of each of eight antimicrobial agents was evaluated by the luciferase microplate assay in parallel with a conventional broth macrodilution method with antimicrobial agents. Decreases in bioluminescence to levels that were < or = 10% of those of drug-free controls were observed in microplate wells containing inhibitory concentrations of drugs in as few as 3 days. The close correlation of these inhibitory concentrations with the MICs determined by a conventional broth macrodilution method suggests that the luciferase microplate method may offer a convenient and reliable means of evaluating the in vitro activities of antimicrobial agents against the M. avium complex.
Use of cryomicrotomy to study gastric diffusion of amoxicillin in guinea pigs
Authors: Lozniewski A , Weber M , De Korwin J D , Conroy M C , Franck P , Floquet J , Le Faou A , Burdin J C
Published: June 2012

Cryomicrotomy has been used as a new technique for removing gastric mucosae from adult guinea pigs for the study of amoxicillin secretion across gastric mucosae. This method allowed a very regular thickness of the removed surface layer of mucosa to be obtained with good reproducibility. Gastric superficial mucosa concentrations and gastric juice concentrations of amoxicillin were determined 1, 2, and 4 h after intramuscular administration (50 mg/kg) in 21 guinea pigs by a microbiological method. No antibiotic was detected in gastric samples at 4 h, except for a low-level mucosal concentration in one animal, thus indicating the short time that amoxicillin is present in gastric samples.